Mediators of Inflammation
Volume 2018 (2018), Article ID 8739473, 22 pages
https://doi.org/10.1155/2018/8739473

Review Article

Role of Epidermal Growth Factor Receptor (EGFR) and Its Ligands in Kidney Inflammation and Damage

Sandra Rayego-Mateos,¹ Raul Rodrigues-Diez,² Jose Luis Morgado-Pascual,³ Floris Valentijn,⁴ Jose M. Valdivielso,¹ Roel Goldschmeding,⁴ and Marta Ruiz-Ortega³

¹Vascular and Renal Translational Research Group, Institut de Recerca Biomèdica de Lleida (IRBLleida), Lleida 25198, Spain
²IdiPAZ, Madrid, Spain
³Cellular Biology in Renal Diseases Laboratory, Universidad Autónoma Madrid, IIS-Fundación Jiménez Díaz, Madrid, Spain
⁴University Medical Center Utrecht, Utrecht, Netherlands

Correspondence should be addressed to Sandra Rayego-Mateos; srayego@irblleida.cat

Received 31 May 2018; Revised 29 October 2018; Accepted 7 November 2018; Published 23 December 2018

Academic Editor: Martha Lappas

Copyright © 2018 Sandra Rayego-Mateos et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract.

Chronic kidney disease (CKD) is characterized by persistent inflammation and progressive fibrosis, ultimately leading to end-stage renal disease. Although many studies have investigated the factors involved in the progressive deterioration of renal function, current therapeutic strategies only delay disease progression, leaving an unmet need for effective therapeutic interventions that target the cause behind the inflammatory process and could slow down or reverse the development and progression of CKD. Epidermal growth factor receptor (EGFR) (ERBB1), a membrane tyrosine kinase receptor expressed in the kidney, is activated after renal damage, and preclinical studies have evidenced its potential as a therapeutic target in CKD therapy. To date, seven official EGFR ligands have been described, including epidermal growth factor (EGF) (canonical ligand), transforming growth factor-α, heparin-binding epidermal growth factor, amphiregulin, betacellulin, epiregulin, and epigen. Recently, the connective tissue growth factor (CTGF/CCN2) has been described as a novel EGFR ligand. The direct activation of EGFR by its ligands can exert different cellular responses, depending on the specific ligand, tissue, and pathological condition. Among all EGFR ligands, CTGF/CCN2 is of special relevance in CKD. This growth factor, by binding to EGFR and downstream signaling pathway activation, regulates renal inflammation, cell growth, and fibrosis. EGFR can also be “transactivated” by extracellular stimuli, including several key factors involved in renal disease, such as angiotensin II, transforming growth factor beta (TGFB), and other cytokines, including members of the tumor necrosis factor superfamily, showing another important mechanism involved in renal pathology. The aim of this review is to summarize the contribution of EGFR pathway activation in experimental kidney damage, with special attention to the regulation of the inflammatory response and the role of some EGFR ligands in this process. Better insights in EGFR signaling in renal disease could improve our current knowledge of renal pathology contributing to therapeutic strategies for CKD development and progression.

1. Introduction

Chronic kidney disease (CKD) is a devastating progressive disease that affects 5–7% of the world’s population. CKD has become a public health priority due to the increasing incidence of type 2 diabetes mellitus, hypertension, obesity, and aging [1]. CKD is characterized by diverse insults that trigger persistent inflammation, development of fibrosis, and loss of renal function ultimately leading to end-stage renal disease. Nowadays, the therapeutic protocols applied for the treatment against CKD have limited effectiveness underscoring the importance of the development of new molecular diagnostic approaches and therapeutic targets to either prevent or delay the progression of renal diseases.

Many preclinical studies have shown that the epidermal growth factor receptor (EGFR) can be a potential therapeutic target for renal diseases, as we will review here. Activation of the EGFR signaling pathway is linked to the regulation of several cellular responses, including cell proliferation, inflammatory processes, and extracellular matrix regulation—all of them being involved in the onset and progression of renal damage. Nowadays, there are seven official EGFR ligands, including the following: EGF (canonical ligand), transforming growth factor-α (TGFA), heparin-binding EGF-like growth factor (HBEGF), amphiregulin (AREG), betacellulin (BTC), epiregulin (EPR), and epigen (EPGN) [2–7]. Recently, the connective tissue growth factor (CTGF/CCN2) has been described as a novel EGFR ligand [7]. Among all EGFR ligands, CTGF has been considered as a therapeutic target and a potential biomarker of human renal diseases [8–15]. The aim of this review is to summarize the contribution of EGFR pathway activation in experimental kidney damage, with special attention to the regulation of the inflammatory response and the role of some EGFR ligands in this process.

1.1. The EGFR Activation Pathways

The binding of neurotransmitters, hormones, or growth factors (ligands) to their membrane receptors produces biochemical changes inside the cell, which lead to a specific response to the initial stimulus. There are different groups of membrane receptors, all defined by their signal transduction mechanisms; these include ionotropic receptors, G protein-coupled receptors (GPCRs), and receptors with tyrosine kinase (RTK) activity. The EGFR (also known as HER1; ERBB1) is a transmembrane glycoprotein of 1186 aa (180 KDa) that belongs to the ERBB family of tyrosine kinase receptors, which is composed of members such as HER2/neu (ERBB2), HER3 (ERBB3), and HER4 (ERBB4). EGFR comprises a cysteine-rich extracellular domain (responsible for ligand binding), a transmembrane domain, and an intracellular domain with tyrosine kinase regions (activation domain) [16]. In most cases, EGFR is activated either directly or indirectly, by EGFR transactivation.

The first step of direct EGFR activation begins with the binding of specific ligands to the receptor. The seven official EGFR ligands have been extensively studied and share a common structure involved in EGF binding [17, 18], but information about the novel described ligands, such as CTGF, is scarce. EGFR ligands activate this pathway in different ways: (1) direct activation by soluble ligands, (2) the juxtacrine mode, when the ligand is anchored to the cell membrane, (3) autocrine signaling, in which EGFR activation occurs in the same cell, (4) the paracrine form if acting on a neighbouring cell [19], and (5) the extracrine form, which combines features of autocrine, paracrine, and juxtacrine signaling as well as possibly endocrine signaling, since EGFR and AREG can be detected in human plasma exosomes [20] (Figure 1).

Figure 1: Types of signaling via epidermal growth factor receptor (EGFR) ligands: (A) the autocrine form if EGFR activation occurs in the same cell; (B) the juxtacrine form, when the ligand is anchored to the cell membrane; (C) the extracrine form, which combines features of autocrine, paracrine, and juxtacrine signaling as well as possibly endocrine signaling; and (D) the paracrine form if acting in a neighbouring cell. Adapted from Singh et al. 2016.

All EGFR ligands can be found as soluble proteins, but some of them are also present as biologically active precursors anchored to the plasma membrane, including HBEGF, TGFA, AR, and BTC. The release of EGFR ligands from the cellular membrane is an important point in the EGFR transactivation process [21–25]. Interestingly, EGFR transactivation can be prompted by physiological and nonphysiological stimuli. The physiological stimuli capable of bringing about this effect include chemokines, adhesion molecules, and growth factors that require previous interaction with its specific receptors (GPCRs or not). EGFR transactivation by nonphysiological processes such as hyperosmolarity, oxidative stress, mechanical stress, ultraviolet light, and γ radiation is mediated by the inactivation of certain phosphatases that antagonize the intrinsic kinase activity of the receptor, thus allowing EGFR autophosphorylation [26].

The affinity of EGFR for its ligands depends on the tissue and pathological condition. Most of the studies have been done comparing the seven official EGFR ligands [17, 18]. These ligands display different ligand-biding affinities at around 3 orders of magnitude [17, 18]. Moreover, depending on the specific ligand that binds to EGFR, different cellular responses can be activated. Structural studies have described how EGFR activation occurs but ligand-related activation is less understood [18]. After EGFR ligand interaction, the receptor undergoes a conformational change leading to the formation of homo- or heterodimers. Then, the intracellular domain is activated in its tyrosine residues by phosphorylation, promoting the autophosphorylation of these same residues in their homologue. Phosphorylated residues in turn serve as a binding site for certain molecules that have domains of SRC homology; this interaction leads to different signaling cascades [27]. Earlier studies described that the different intracellular signaling triggered after EGFR activation depends on the phosphorylation of certain residues in the intracellular domain of the receptor. In SAA cells (NIH3T3 fibroblasts that overexpress human EGFR) stimulated with EGF, treatment with a phosphopeptide that blocks the autophosphorylation site Tyr1068 of EGFR induced a significant inhibition of EGFR/Grb2 interaction and RAS/MAP kinase activation [28]. EGFR activation translates signals to the nucleus, modulating the activity of transcription factors such as c-JUN, c-FOS, c-MYC, and NFKB and regulating gene transcription [16]. In bronchial epithelium, EGFR activation is linked to phosphorylation of the tyrosine residue (Tyr1173) associated with the activation of JNK, AP1, p38 MAPK, and NFKB pathways [29]. On the other hand, SRC kinase protein can act as cotransducer of EGFR signals and SRC-dependent EGFR activation mediated by EGFR phosphorylation of Tyr 845 and Tyr 1101 [30, 31].

EGFR transactivation (indirect activation) is triggered when different molecules bind to their specific receptors. A variety of these molecules have been identified and can be broadly categorized into the following groups: G protein-coupled receptors (e.g., Ang II and ET-1), cytokines (e.g., TNFA, TWEAK, and other TNF receptor family proteins), growth factors (e.g., TGFB and other proteins, including TPA and LPA), integrins, ion channels, and other physical stimuli [32–38]. Many of these molecules that transactivate EGFR are very relevant in renal damage, including Ang II, TGFB, and TNF receptor family proteins, showing the importance of EGFR transactivation in renal pathology. After the specific binding of these molecules to their own receptors, several second messengers, including intracellular Ca²⁺, reactive oxygen species (ROS), and protein kinases, such as PKC, can be released [39–41]. These intracellular signals trigger a signaling cascade, leading to the activation of metalloproteases/disintegrins from the family of ADAMs. In general, the EGFR ligands involved in EGFR transactivation are inactive transmembrane precursors located in the cellular membrane which need to undergo proteolytic processing and be released as soluble ligands into the extracellular medium in order to bind to EGFR [42], being the most studied EGF, TGFA, and HBEGF. This proteolytic processing is carried out by ADAMs. Therefore, EGFR transactivation via ADAMs leads to the release of EGFR from the cellular membrane and subsequent binding to EGFR and pathway activation. Alternatively, in some cases, EGFR transactivation can occur independently of MMPs/ADAMs and is mediated by intracellular protein kinases, as in the case of Src kinase [43–46] (Figure 2).

Figure 2: Different EGFR signaling systems in the inflammatory process: (A) direct ligand-receptor activation: the first step for the direct activation of EGFR begins with the binding of the ligand to the receptor. In general, EGFR ligands are located as inactive transmembrane precursors, which, in order to bind to their receptor, need to undergo proteolytic processing and be released as soluble ligands into the extracellular medium. This proteolytic processing is carried out by metalloproteases/disintegrins of the ADAM family. (B) Indirect ligand-receptor activation/transactivation: this process is triggered by the binding of molecules such as Ang II, thrombin, and ET1 to their specific receptor. After this binding, the release of second messengers is induced, such as intracellular Ca2⁺, ROS, and certain protein kinases such as PKC, which induces activation of metalloproteases/disintegrins of the family of ADAMs. After EGFR ligand interaction, the receptor undergoes a conformational change inducing the formation of homo- or heterodimers. Then, the intracellular domain is activated in its tyrosine residues by phosphorylation, promoting the autophosphorylation of these same residues in their homologue. Phosphorylated residues in turn serve as a binding site for certain intracellular kinases that are capable of activating EGFR independently to MMPs, as in the case of the SRC kinase.

1.2. ADAMs: Key Proteins in EGFR Transactivation

ADAMs are a family of 23 glycoproteins expressed as transmembrane surface proteins consisting of an extracellular metalloproteinase domain followed by a disintegrin-like domain, a cysteine-rich domain, a transmembrane domain, and finally a cytoplasmic tail. Their proteolytic activity is mediated by the zinc-dependent metalloproteinase domain, with the other domains contributing to substrate recognition and regulation. These domains give them its characteristics of adhesion molecules and proteases [47]. The first ADAMs described were involved in reproductive functions, mainly spermatogenesis and the attachment of sperm to the ovule (ADAM1 and ADAM2). However, only 12 of the human ADAMs (ADAM8, 9, 10, 12, 15, 17, 19, 20, 21, 28, 30, and 33) contain a functional catalytic consensus sequence (HEXGEHXXGXXH). The physiological function of the proteinase-inactive ADAMs (ADAM2, 7, 11, 18, 22, 23, 29, and 32) remains largely unknown, although some members of this group play important roles in development and function as adhesion molecules rather than proteinases [48, 49]. Numerous transmembrane proteins have been identified as targets of ADAM-mediated proteolysis [50]. Some of these substrates can be cleaved by different ADAMs, while others appear to be specific to an individual ADAM.

Recently, the roles of different ADAMs such as ADAM9, 10, 12, 15, 17, and 19 in the release and/or activation of cell surface proteins have been described. Among those proteins cleaved by ADAMs are several EGFR ligands, such as EGF, TGFA, and HBEGF [47, 51]. Depending on the tissue, different ADAMs may be involved in the release of the EGFR ligands. For example, kidney angiotensin II- (Ang II-) induced transactivation of EGFR is mediated by ADAM17 and by the release of TGFA [52], while in the heart, ADAM12 regulates this process through the release of HBEGF [53].

These glycoproteins are synthesized in the Golgi apparatus; under the action of the furin protease, they undergo a conformational change that induces activation. In their active form, they are transported to the plasma membrane where they exert their sheddase activity on the inactive precursors of the EGFR ligands. Functional upregulation of ADAM activity is generally observed in association with cytosolic Ca²⁺ elevation, purinergic receptor agonists, or membrane-perturbating agents. In some cases, such as ADAM17, sheddase activity is amplified by other signaling pathways, including activation of protein kinase C (PKC) and receptor tyrosine kinases. Furthermore, certain physicochemical properties of the lipid bilayer also govern the action of ADAM proteases [54].

Once these precursors are proteolytically processed, they are released into the extracellular environment and can interact with EGFR and activate this signaling pathway [42]. Therefore, modulation of ADAM activity is of paramount importance to EGFR activation. Indeed, several strategies for ADAM inhibition are being considered as pharmacological targets. Thus, therapeutic strategies have focused on the inhibition, induction, and activation of ADAM expression as well as the use of small molecules blocking the active site and events blocking the domain for substrate recognition [55].

1.3. EGFR in Pathological Processes

Malfunctioning of EGFR, or its related pathways, has been shown to be relevant to the pathogenesis of several malignancies, playing a role in the development of ovarian, breast, and colorectal cancers as well as non-small cell lung and head and neck carcinomas [56]. Moreover, a strong correlation between EGFR expression and prognosis has been found in ovarian, head and neck, bladder, and esophageal cancers [57]. Thus, anti-EGFR therapy could have a place in the treatment of some of these tumors; in fact, the use of erlotinib or cetuximab may be employed as second-line therapy after failure of mono- or polychemotherapy in squamous cell lung carcinoma [58]. Recent studies suggest that EGFR activation can be involved in inflammatory diseases. Overexpression of EGFR may be related to a number of skin disorders, such as psoriasis or atopic dermatitis [59]. Apart from these spontaneously occurring diseases, it has been described that inhibition of EGFR by either monoclonal antibodies or small-molecule EGFR tyrosine kinase inhibitors brings about a monomorphic acneiform reaction, which, interestingly, is directly correlated with overall survival [60]. EGFR blockade is being explored as a new treatment for the disease [61], and future studies on inflammation are needed.

1.4. EGFR in the Kidney in Normal and Pathological Conditions

EGFR is expressed in the kidney, specifically localized in the glomerulus and the tubulointerstitial compartment [62]. This receptor plays a key role in renal electrolyte homeostasis [42]. However, its role in renal pathology is somewhat contradictory since both beneficial and deleterious actions have been found. Interestingly, upregulation of the EGFR pathway (including several of its ligands, as TGFA, HBEGF, and CTGF) has been described in human and experimental chronic renal pathologies, including glomerulonephritis, diabetic nephropathy, transplant rejection, and polycystic kidney disease [63–65], as well as in experimental models of acute kidney injury (AKI), such as ischemia/reperfusion or folic acid administration [66–68]. Intensive research in many experimental studies has shown that EGFR blockade exerts beneficial effects in progressive kidney disease, mainly ameliorating fibrosis [69, 70]. However, EGFR inhibition in AKI models exerts opposite results, presenting deleterious effects. Studies in models of ischemic injury using waved-2 mice (an EGFR mutation that induces a reduction in receptor tyrosine kinase activity) and wild-type mice treated with the EGFR kinase inhibitor erlotinib showed significantly decreased renal function in the depleted/treated mice [71, 72]. On the contrary, activation of the EGFR pathway can accelerate renal recovery in the early AKI phase by means of a mechanism that involves induction of renal tubular cell regeneration and protection of these cells from apoptosis, as demonstrated by the in vivo administration of several ligands (EGF, HBEGF) in experimental acute ischemic injury [69, 73–78]. These data were confirmed in vitro in cultured proximal tubular epithelial cells, in which activation of EGFR by the ligands EGF [76], HBEGF [46], and EPR [78, 79] induced cell proliferation and migration, supporting their protective role in renal repair after AKI. Thus far, there are no studies of CTGF modulation in experimental AKI.

Interestingly, the consequences of EGF signaling activation depend on species. In models of hydronephrosis, EGF administration causes cell death in mice, while it induces cell survival in rats [80]. Moreover, in a rat model of cisplatin-induced nephrotoxicity, the EGFR inhibitor erlotinib induced renoprotective properties by modulation of apoptosis and proliferation of tubular cells [81].

1.5. Official and Novel Described EGFR Ligands and Signaling in Renal Physiopathology

Most EGFR ligands have a similar globular structure, with a common fold defined by six conserved cysteine residues that form three disulphide bonds, termed EGF motifs, through which they interact with EGFR [82–86]. In contrast, CTGF does not possess an EGF motif and interacts with EGFR through its C-terminal domain [7] and future studies are needed to compare its structural binding to EGFR with other ligands. Several EGFR ligands contain amino-terminal heparin-binding domains (HBEGF domains), including HBEGF, AR, and CTGF [87, 88]. Contradictory results have been also reported in diabetic nephropathy. For instance, high glucose induces transactivation of EGFR and profibrotic responses in mesangial cells by increasing HBEGF release [89, 90]. However, Dey et al. [91] reported a beneficial effect of ADAM-mediated EGFR transactivation by bradykinin, leading to a decrease of podocyte permeability. EGFR ligands have generally been classified based on their interaction with EGFR and can be categorized into two classes: high affinity or low affinity. The high-affinity ligands are EGF, TGFA, HBEGF, and BTC, which bind to EGFR and have a dissociation constant (Kd) of between 1 and 100 nM, while the low-affinity ligands, AR, EPR, and EPGN, have a Kd greater than 100 nM [17]. CTGF has a Kd of 126 nM, which places it within the group of ligands of lower affinity [7].

1.6. EGF (Canonical Ligand)

EGF is the canonical EGFR ligand and the one with the highest EGFR affinity described to date. EGF was identified from submaxillary gland extracts during nerve growth factor studies [92]. The kidney is the key source for EGF production, and several studies have identified elevated urine EGF levels as an independent risk factor for CKD progression [93–97].

EGF is produced in the kidney as a membrane-anchored prepro-EGF located in the apical membrane of epithelial cells [93, 98, 99]. Earlier studies conducted in rats showed positive EGF immunostaining, mostly in the proximal tubules, as well as increased EGF mRNA levels in the thick ascending limb of Henle’s loop and distal convoluted tubules [100, 101]. EGF regulates physiological processes in the kidney. Several studies have shown the important role of EGF on sodium and magnesium transport through the regulation of epithelial ion channels such as epithelial sodium channel (ENaC) or Na⁺/K⁺/2Cl⁻ cotransporter (NKCC1), among others [102–105]. Many studies have described the importance of EGF in polycystic kidney diseases [106–108] as well as the role of EGF in cell proliferation, including in tubular epithelial cells [109, 110]. Exogenous EGF administration has been found to reduce tissue injury caused by ischemia/reperfusion injury (IRI) showing beneficial antiapoptotic and antioxidant effects [111–113]. However, in vitro studies described prooxidative effects. In mammalian cells, EGF enhances the production of intracellular reactive oxygen species by dual oxidase 1 [114] and these oxidative species, which are induced by EGF, modulate ADAMs (positive regulator of EGFR signaling) or protein tyrosine phosphatases (negative regulator of EGFR signaling) [115–118]. AKI is a multifactorial pathology characterized by renal tubular damage, inflammation, and, frequently, a transient decrease in renal function. After the initial injury, there is a recovery phase, associated with proximal tubular cell proliferation and migration (as part of a regeneration process). But if this regenerative process fails to resolve, it may lead to fibrosis and loss of renal function [42, 119, 120]. Several experimental studies have shown the involvement of EGF in renal regeneration after IRI damage [121–123], but studies on EGF signaling in renal inflammation are scarce.

1.7. Transforming Growth Factor-α (TGFA)

TGFA is one of the most widely studied EGFR ligands. TGFA is expressed in normal adult human kidney [121], and TGFA protein is detected in the urine of healthy human subjects [122]. Several experimental models of renal damage have described upregulation of TGFA. In an experimental model of renal mass reduction, elevated TGFA protein levels were markedly increased after nephron reduction and prior to the development of renal lesions [123]. Experimental studies have demonstrated the involvement of TGFA in renal fibrosis, as in the model of Ang II-induced renal damage [52]. Moreover, elevated mRNA expression levels of TGFA were found in inflammation-induced renal damage triggered by systemic administration of TWEAK. In addition, treatment with a pharmacological inhibitor of ADAM17 (WTACE2) diminished renal inflammation associated with downregulation of TGFA and inhibition of EGFR pathway activation [38]. In in vitro studies in cultured tubular epithelial cells, stimulation with recombinant TGFA upregulated proinflammatory gene expression [38]. In these cells, upregulation of proinflammatory cytokines and chemokines induced by stimulation with aldosterone and TWEAK was blocked by a TGFA-neutralizing antibody [124]. Additionally, in Xenopus 2F3 cells, chronic treatment with TGFA over 24 hours inhibits the epithelial sodium channel ENaC by decreasing the number of channels in the membrane through the modulation of MAPK1/2 pathways but acute treatment with TGFA for 1 hour activates ENaC via PI-3 kinase [125]. In models of middle cerebral artery occlusion in mice and rats, TGFA treatment significantly reduced infarct size, suggesting that TGFA can induce angiogenesis, neurogenesis, and neuroprotection after stroke [126, 127].

Several studies have investigated the effect of TGFA loss on different pathological conditions. Research using a model of acute intestinal mucositis in TGFA knockout mice described that the lack of TGFA in intestinal epithelial cells resulted in higher apoptosis and lower proliferation [128]. In a model of bleomycin-induced lung injury, TGFA-null mice exhibited diminished pulmonary inflammation and fibrosis compared to wild-type mice [129]. Another study about peripheral nerve injury showed that TGFA knockout mice have no effect in regeneration process, probably due to compensatory expression mechanisms of other EGFR ligands [130]. These studies demonstrated that EGF-related growth factors could present specific and unique functions in certain tissues and cells.

1.8. Heparin-Binding Epidermal Growth Factor (HBEGF)

HB-EGF is a 22 kDa protein originally identified in macrophage-like U-937 cells [131]. HBEGF is synthesized as a transmembrane precursor protein (pro-HBEGF) that can be cleaved by metalloproteinases such as ADAM17 to release a mature soluble HB-EGF (sHBEGF), a different form that is more functionally active in vivo than the precursor protein [82, 132]. The soluble form of HBEGF is capable of linking to heparan sulfate proteoglycans present in the cell surface, favouring local expression and accumulation of growth factors [133]. HBEGF participates in several physiological and pathological events, including wound healing [134], atherosclerosis [135], and tumor progression [136].

Some studies have analysed the role of HBEGF in renal pathology. Studies carried out on HBEGF-deficient mice showed the involvement of this ligand in podocyte damage in progressive glomerulonephritis. The loss of HBEGF was associated with lower renal inflammatory infiltration and decreased albuminuria levels prior to the appearance of renal cell proliferation [137]. Several studies using mice with specific HBEGF deletion in endothelium demonstrated attenuated renal damage in streptozotocin- (STZ-) induced diabetic renal injury [138] and in response to Ang II infusion [139]. In these conditional knockout mice, the inflammation in the perivascular area or renal interstitium (tested by F4/80- and CD3-positive stained cells) and the renal fibrosis caused by Ang II were significantly reduced compared to those in control mice [139]. Pharmacological blockade of ADAM17 by WTACE2 in a model of renal injury induced by TWEAK administration reduced HBEGF renal mRNA expression levels associated with lower inflammatory cell infiltration [38]. In vitro studies have clearly demonstrated that HBEGF regulates cell proliferation, including in glomerular epithelial cells [69, 140], and also regulates proinflammatory gene expression, as observed in cultured tubular epithelial cells [38]. In inner medullary collecting duct cells, the sustained exposure to sHBEGF induces the transition from an epithelial to a mesenchymal phenotype by upregulating the E-cadherin transcriptional repressor SNAIL2, thus contributing to renal fibrosis [141].

1.9. Amphiregulin (AREG)

AREG is constitutively expressed in different cell types during development and homeostasis [142] and participates in several physiological processes, including the regulation of pulmonary morphogenesis [143] and the proliferation of keratinocytes [144]. Although AREG was originally described as an epithelial cell-derived factor, multiple studies have shown that it can also be expressed by activated immune cells in different inflammatory processes. Emerging evidence shows that AREG plays a critical role in restoring tissue integrity after infection or inflammation [145–148] and induces tolerance by promoting the restoration of tissue integrity after damage associated with acute or chronic inflammation [149, 150]. The immune system plays an important role in the EGFR signaling pathway, thus contributing to the progression of the inflammatory process. Cells such as basophils express high amounts of AREG after exposure to IL3 [151] and other types of immune cells such as neutrophils, CD8 T cells, and T regulatory lymphocytes [149]. Interestingly, AREG is expressed only in proinflammatory-type M1 macrophages [152]. Inflammation, ischemia, and hypoxia induce AREG expression in the brain. Under these situations, glial cells show upregulation of AREG, which protects against neuronal cell death. In neuro-2a cells, administration of AREG inhibits endoplasmic reticulum stress and cell death [153].

There are few studies about the role of AREG in kidney damage. In autosomal dominant polycystic kidney disease, the use of anti-AREG antibodies and inhibitors of activator protein-1 (AP1) can reduce cell proliferation in cystic cells by reducing AREG expression and EGFR activity [154]. In a model of streptozotocin-induced diabetes, the genetic blockade of EGFR or pharmacological inhibition using erlotinib showed a downregulation of phospho-AKT, CTGF, and AREG expression compared to that in diabetic mice [155]. However, there are no studies assessing the role of AREG gene deletion of direct modulation in experimental renal disease.

1.10. Betacellulin (BTC)

BTC was first described in 1993 by Shing and et al. as a mytogen from pancreatic B cell tumors [5]. BTC was detected in the normal kidney at low levels; its location in the nephron remains unclear [156]. BTC could have different roles depending on the organ where it is expressed. A murine model of BTC overexpression demonstrated a reduction in body weight in BTC transgenic animals, which was accompanied by a reduction in kidney and pancreas weight, whereas the lungs of these animals were overgrown and their hearts had the same weight as those in controls [157]. Regarding inflammation, few studies have evaluated the role of BTC in this process, and to our knowledge, there is none in the kidney. One study demonstrated that BTC upregulates COX-2 expression in human granulose cells [158]. With regard to particular diseases, elevated BTC levels have been described in rheumatoid arthritis patients [159] and other authors observed that BTC overexpression protects against acute pancreatitis by activating stress-activated protein kinase [160].

1.11. Epiregulin (EPR)

EPR was originally purified from conditioned medium of the fibroblast-derived tumor cell line NIH3T3/T7 [6] and is another example of the less widely studied EGF ligands. Higher EPR concentrations were found in patients with inflammatory diseases [161], including patients suffering from rheumatoid arthritis [159]. In this pathology, EPR inhibition suppresses the development of experimental autoimmune arthritis [161]. EPR regulates several immune-related processes. EPR is involved in peptidoglycan-mediated proinflammatory cytokine production in antigen-presenting cells and in innate immunity [162]. In a model of wound healing in corneal epithelial cells, EPR knockout mice presented an increased number of infiltrating cells in the wound area and this difference was related to the upregulation of several proinflammatory factors, including IL6, CXCL1, CXCL2, and CCL2 [163]. In the kidney, EPR promotes proliferation and migration of renal proximal tubular cells [78]. In 2016, Boyles et al. [164] commented on unpublished data with regard to the potential beneficial effects of a specific EPR neutralization antibody in experimental diabetes. However, the direct role of EPR on kidney inflammation requires further study.

1.12. Epigen (EPGN)

EPGN was first identified in 2001 by Lorna Strachan. It consists of 152 amino acids and a transmembrane domain. EPGN is present in many tissues such as the testes, heart, and liver and is characterized as a low-affinity ligand [165, 166]. Several studies have shown that EPGN participates in cell proliferation. EPGN is a mitogen for HaCaT cells [165]. In epithelial cells, EPGN stimulates phosphorylation of c-ERBB1 and MAP kinase proteins [165]. The EPGN transgenic overexpression during embryonic development induces sebaceous gland hyperplasia [167], and the activation of NRF2 causes sebaceous gland enlargement in an EPGN-dependent manner [168]. EPGN-null mice exhibit peripheral demyelinating neuropathy that induces muscular dystrophy [169]. Data on inflammation, however, is scarce. One study described the involvement of EPGN in the inflammatory process in the skin via ERK pathway activation [170]. Other studies reported that recombinant EPGN is unable to activate ERBB2 in the presence of other ERBBs. Additionally, soluble EPGN has more mitogenic activity than EGF, although its binding affinity is lower [171].

1.13. The Two Unofficial/Novel Ligands

1.13.1. Teratocarcinoma-Derived Growth Factor 1 (TDGF1; CRIPTO1; CR-1)

CRIPTO1 is another molecule that binds to EGFR but differs to official EGFR ligands because it does not possess an EGF-like motif. In addition to binding to EGFR, CRIPTO1 also acts as a coreceptor for the TGFB subfamily. CRIPTO1 is critically important in early embryogenesis, maintenance of stem cells, and the progression of some types of cancer [172]. There are few studies on the role of this EGFR ligand in pathophysiological processes. A cancer study reported that CRIPTO1 was expressed in a certain type of non-small cell lung cancer that causes intrinsic resistance to specific inhibitors of EGFR tyrosine kinase activity and participates in EMT [173]. A recent study suggests a potential role of this EGFR ligand in cardiac repair. In human cardiac ventricular fibroblasts, CRIPTO1 production was increased in response to reparative factors, such as NRG1B, and the blockade of PI3K, ERBB2, and ERBB3 by pharmacological inhibitors or neutralizing antibodies significantly reduced CRIPTO1 levels [174]. Currently there are no studies about the role of CRIPTO1 in inflammatory processes or in kidney diseases.

1.13.2. Connective Tissue Growth Factor (CCN2/CTGF): A Newly Described EGFR Ligand

CTGF (also known as CCN2) is a cysteine-enriched secretable matricellular protein with a molecular weight of 38 kDa. CTGF was identified in the conditioned medium of endothelial cells of the umbilical cord vein [175]. This protein has a modular structure made up of a secretory peptide at the N-terminal end followed by 4 functional modules [176]: (1) the insulin-like growth factor- (IGF-) binding domain, which stimulates the production of matrix proteins in renal cells [177–179]; (2) the von Willebrand factor type C domain, which is rich in cysteines and participates in protein oligomerization and synthesis. In Xenopus cells, CTGF binds directly to TGFB through this domain and promotes binding to its receptor, leading to the activation of the Smad response promoter [180]; (3) the thrombospondin-1 domain, which is involved in the union of soluble macromolecules or matrix proteins and participates in the union of CTGF to VEGF [181, 182]; and (4) the C-terminal domain, a dimerization domain involved in binding to the cell surface, possesses mitogenic activity for fibroblasts, and is responsible for the interaction with fibronectin [183]. This domain contains heparin-binding EGF sites [87, 88] and a region with a cysteine knot motif that resembles PDGF, TGFB, and NGF [184]. Finally, the N-terminal domain contains putative binding sites for IGF and TGFB.

Between module 2 and module 3, there is a hinge region that can be processed by multiple proteases, including the MMPs 1, 2, 3, 7, 9, and 13, generating two protein portions (one with the N-terminal domain and the other with the C-terminal domain), both with biological activity. This region can also be proteolyzed by elastase and plasmin, which can cleave the individual modules to produce four fragments [185]. In addition, it has been observed in vitro that MMP2 processes CTGF, thereby generating the C-terminal fragment of 10–12 kDa. In biological fluids and in the medium of cells in culture, the presence of CTGF has been described in its different forms: complete molecule CTGF, C-terminal fragment, and the N-terminal fragment [186, 187]. However, the in vivo biological effects of CTGF and its fragments have not been investigated in depth.

1.14. Role of CTGF in Pathological Processes: A Key Mediator in Renal Inflammation

CTGF plays an important role in multiple cellular processes such as development, differentiation, cell proliferation, extracellular matrix (ECM) remodelling, and angiogenesis [8]. According to the cell type, a large variety of factors and molecules are involved in the induction and regulation of CTGF expression, including GPCR agonists, such as Ang II; growth factors such as TGFB, BMP, VEGF, IGF, GMCSF, and IL4; high concentrations of glucose; AGEs; hypoxia; mechanical stress; and oxidative stress [188–196].

CTGF is a developmental gene that is not expressed in adult tissues. However, under pathological conditions, CTGF could be induced in several diseases such as scleroderma, pulmonary fibrosis, and hepatic fibrosis [178, 196, 197] and in a multitude of renal diseases, including diabetic nephropathy [10, 198, 199]. In several independent studies, CTGF has been proposed as a biomarker for human diabetic nephropathy and other forms of CKD [8, 10–12] and also for cardiac dysfunction in patients exhibiting myocardial fibrosis and chronic heart failure [13]. Plasma CTGF levels predict end-stage renal disease and mortality in diabetic nephropathy [12]. Moreover, urine CTGF can also be used as predictor/biomarker of CKD, including diabetic nephropathy [9, 10, 14]. Patients with reduced right ventricular function had higher plasma CTGF levels than those with normal or mildly reduced right ventricular function [15].

Initial studies demonstrated the role of CTGF as a mediator of the profibrotic action of TGFB [200] and other factors involved in renal damage, such as Ang II [201] or endothelin-1 [202]. Additionally, experimental studies showed that blockade of endogenous CTGF using different approaches, including antisense oligonucleotides or gene silencing, demonstrated beneficial effects in fibrotic-related diseases, including experimental lung, liver, and vascular damage, as well as models of chronic renal damage, including diabetic nephropathy [200, 201, 203–205]. Interestingly, CTGF exerts opposite effects in other pathologies in much the same way as other EGFR ligands. CTGF overexpression conferred cardioprotection in Ang II-infused mice and in ischemia-reperfusion injury [206, 207]. However, the role of CTGF in AKI has not been investigated in depth. A recent study by our group described the beneficial effects of CTGF gene deletion, reducing proliferation, the induction of the G2M phase of cellular cycle, and fibrosis in the kidney using a model of CTGF injection over 10 days [70]. Near total inhibition of CTGF below baseline levels reduced tubulointerstitial fibrosis in different models of renal damage, such as folic acid administration or obstructive nephropathy [70, 208].

Many reports suggest that CTGF can also be considered a cytokine involved in the regulation of immune and inflammatory responses. CTGF can activate several cells of the immune system. CTGF is a chemotactic factor for immune cells, including mononuclear cells [209], and induces cell adhesion and migration [210]. In human CD4 lymphocytes, CTGF, in combination with IL16, contributes to Th17 differentiation [211]. Interestingly, monocyte-derived macrophages do not produce CTGF on stimulation with TGFB, lipopolysaccharide, but CTGF is taken up by macrophages in vitro [209]. In an early study, our group demonstrated that in vivo administration of the C-terminal CTGF fragment induced an acute renal inflammatory response, characterized by infiltration of inflammatory cells in the kidney (lymphocytes and macrophages) and activation of the NFKB and subsequent induction of proinflammatory factors such as CCL2, CCL5, and IL6 [212]. In later studies, we found that CTGF induces a sustained renal inflammatory response linked to activation of the Th17 response, characterized by the presence of interstitial infiltration of Th17 (IL17A⁺/CD4⁺) cells and upregulation of Th17-related factors (STAT3 and RORγt) [211]. Recent evidence suggests that CTGF can also regulate inflammation in other pathological conditions. Studies performed with conditional CTGF knockout mice have found lower macrophage accumulation and downregulation of proinflammatory factors in peritoneal-induced damage [213]. In experimental models of alcohol-induced inflammatory process in the pancreas, overexpression of CTGF in mice plays a novel role, regulating inflammation by increasing infiltration of macrophages and neutrophils and increasing inflammatory mediators such as IL1B or CCL3 [214]. In another study in a model of skin fibrosis induced by Ang II, pharmacological blockade with a neutralizing antibody against CTGF mitigated the inflammation and fibrotic process in the dermis and diminished the number of cells expressing PDGFRB, procollagen, αSMA, pSMAD2, CD45, and FSP1 [215].

Recent studies have analysed the relationship between CTGF and other signaling pathways. Several have demonstrated the crucial role played by integrins, proteoglycans heparan sulfate, and low-density protein receptors in CTGF cellular responses [216]. The existence of CTGF binding sites in the cell membrane was suggested in 1998 in chondrocyte studies [217]. In 2005, a potential CTGF receptor was described in mesangial cells, the receptor tyrosine kinase of nerve growth factor (TRKA), a member of the TRK membrane receptor family (TRKA, TRKB, and TRKC) [218]. Some studies have confirmed that CTGF also activates TRKA in murine cardiomyocytes and tubuloepithelial cells [7, 219]. In 2013, we described that CTGF can bind to EGFR through its C-terminal module and via a process modulated by αVβ3 integrin [7]. The CTGF-EGFR interaction activates this signaling pathway linked to the modulation of proinflammatory factors and the recruitment of lymphocytes and macrophages in the kidney [7]. At the vascular level, we also observed that CTGF-EGFR activation is linked to the oxidative process, endothelial dysfunction, and vascular inflammation through the NOX1 and NFKB pathways [220]. These results demonstrate that the activation of the EGFR pathway by the new ligand CTGF regulates inflammatory processes (Figure 3) and identify EGFR as a potential therapeutic target for the treatment of chronic kidney disease and vascular diseases closely linked with kidney damage.

Figure 3: Different signaling pathways related to EGFR activation induced by CTGF/EGFR interaction. CTGF binds to EGFR through its C-terminal module. This interaction activates the EGFR signaling pathway linked to the modulation of different pathways closely related with cell growth, oxidative process, inflammation, EMT, and fibrosis in renal damage.

In summary, EGFR activation has dual effects in AKI or CKD, ameliorating renal damage in experimental AKI by activating the regenerative process that occurs following acute renal damage through the induction of proliferation and migration of tubular cells. In contrast, EGFR activation exerted deleterious effects on CKD by activation of a fibrotic-related process, as observed in long-term models of renal damage [42, 70, 119, 120] (Figure 3).

1.15. Role of ERBB Crosstalks in Renal Inflammation

Previous studies described the possible crosstalk between EGFR and other receptors. The most obvious EGFR crosstalk is related to its heterodimerization with other members of the ERBB family (ERBB2, ERBB3, and ERBB4), whose function is amplifying and diversifying the signals [221–223].

Depending of the type of dimerization of ERBB1 (with itself or with other ERBB receptors as ERBB2), the signaling is very different [224, 225]. Only ERBB1/EGFR, ERBB3, and ERBB4 are able to bind ligands, an obligatory process for activation of the tyrosine kinase domain and intracellular signaling [226, 227]. ERBB2 has no known ligands, and it acts as a signal transducer in the recruitment of other components of the heteromeric complexes like ERBB1, ERBB3, or ERBB4 [228, 229]. ERBB3 has no kinase activity, and the biological relevance of the complex formation with other ERBB receptors (ERBB2-ERBB3 and ERBB2-ERBB4) has been analysed in studies with ERBB2,3,4-null mice [230–233].

As described above, EGFR transactivation can be induced by several GPCRs, different cytokines, integrins, and diverse tyrosine kinase receptors (TKRs) [36, 234, 235]. Moreover, it is possibly a crosstalk induced by ligand-independent EGFR transactivation, which consists of physical interactions between EGFR and other receptors such as platelet-derived growth factor receptor (PDGFR) [236] or IGF1R [237] and c-MET [238].

Several studies developed in monocytes have described a crosstalk between EGFR and GPCRs, linked to the regulation of inflammatory responses. The pharmacological blockade of EGFR or N-formyl-l-methionyl-l-leucyl-phenylalanine (fMLP) receptor, with AG1478 or cyclosporine H, respectively, decreased oxidative stress, CD11b upregulation, and EGFR/fMLP phosphorylation induced by their respective ligands. This crosstalk is SRC and ERK dependent [239]. In cervical cancer, GPCR TF-PAR2 (tissue factor protease-activated receptor 2) transactivates EGFR and mediates resistance to cisplatin, decreasing cisplatin-induced apoptosis [240]. Another study in monocytes has described a crosstalk between EGFR and TRKA in response to the stimulation of GPCRs [239], which further confirms the interaction between these two receptors. TRKA is a member of the TRK membrane receptor family (TRKA, TRKB, and TRKC). These receptors interact with neurotrophins and form homo/heterodimers with the low-affinity neurotrophin receptor, p75NTR [241].

There are few studies about EGFR crosstalks in renal inflammation. Most of them are related to EGFR transactivation. Lautrette et al. [52] demonstrated a possible crosstalk between EGFR and Ang II receptors in the kidney. In this in vivo study, the authors showed that Ang II is capable of transactivating EGFR and overexpression of a dominant negative isoform of EGFR prevents the frequency and severity of renal lesions in Ang II mice as well as interstitial cell infiltration.

In rat renal fibroblasts, palmitic acid (PA) activated the EGFR signaling pathway through TLR4/c-Src signaling. Previous studies described that fatty acids directly activate Toll-like receptor 4 (TLR4) and this process can induce c-SRC kinase activation [242]. In NRK-52E cells, the pharmacological blockade of EGFR or c-SRC previous to PA stimulation suppressed EGFR activation and its downstream signaling pathways ERK and AKT, closely related with renal inflammation and oxidative stress. The genetic silencing of TLR4 through siRNA transfection blocked the PA-induced phosphorylation of EGFR, c-SRC, ERK, and AKT [243].

A study carried out in hepatocyte growth factor (HGF) transgenic mice demonstrated that the HGF/c-MET system significantly reduced LPS-induced renal and vascular injuries by the diminution of inflammation and ROS production, though EGFR ubiquitin degradation [244].

In vitro studies have described an EGFR crosstalk with aldosterone receptors. In cultured tubular epithelial cells, aldosterone caused EGFR transactivation, by a process mediated by ADAM17 and release via TGFB, and upregulated proinflammatory genes, via ERK and STAT1 activation [124]. In mesangial cells, aldosterone also activates EGFR linked to ROS production, ERK signaling, and modulation of cell growth [245].

A study developed in renal cells using gene silencing and pharmacological inhibitors of EGFR and TRKA demonstrated a clear crosstalk between EGFR and TRKA in response to stimulation with CTGF [7]. The analysis of the phospho-proteomic profiles of TRKA and EGFR shows a considerable similarity in the signaling originated by these RTKs [246]. EGFR crosstalk with TNF-related proteins is also involved in renal inflammation. TWEAK, a TNF member, is a cytokine that engages its receptor Fn14 to activate ADAM17, which releases the mature ligands HBEGF and TGFA that, in turn, transactivate EGFR. In cultured tubular epithelial cells, Fn14 gene silencing inhibited TWEAK-induced EGFR phosphorylation. Conversely, EGFR inhibition blocked TWEAK-induced responses, including activation of the ERK kinase pathway and upregulation expression of proinflammatory factors [38]. Moreover, pharmacological EGFR blockade inhibited TWEAK-induced renal inflammation. In vitro studies in renal cells have described that CTGF is involved in TGFB-induced EGFR transactivation [7]. However, the functional consequence of this EGFR/TRII crosstalk has not been investigated.

In conclusion, there are some possible crosstalks between ERBB1 and other receptors and their different interaction will trigger diverse signaling pathways, as well as amplify and diversify the intracellular signals related to inflammation and other key processes in kidney diseases. However, more studies in this topic are needed.

1.16. Therapy Targeting the ERBB1 Receptor in Kidney Disease

Several experimental studies have suggested that blocking EGFR could be an important tool to treat kidney diseases [42], especially by regulating inflammation, cell proliferation, and fibrosis [7, 38, 69]. Studies conducted in an autosomal recessive polycystic kidney model showed that treatment with an EGFR kinase inhibitor decreased the formation of cysts and improved renal function. In addition, similar results were observed using WAVED-2 mutant mice (which present a point mutation in EGFR that reduces their 90% tyrosine kinase activity) [247]. In subsequent studies using the same mice model, it was observed that the beneficial effect of EGFR blockade was increased when is combined with the inhibition of ADAM17 [248]. Previous studies described that the EGFR blockade in different mice models of renal damage, induced by CCN2 and TWEAK injection, reduced the inflammatory infiltration of T lymphocytes and macrophages as well as the gene and protein expression of the proinflammatory mediators CCL2, CCL5, or IL6 [38]. In vitro studies developed in tubuloepithelial cells and an experimental model of renal inflammation in mice induced by TWEAK injection showed that the pharmacological blockade of ADAM17 with TAPI-2 and WTACE-2, respectively, inhibited the upregulation of proinflammatory mediators at gene and protein levels. Studies performed in models of renal mass reduction (subtotal nephrectomy) and prolonged ischemia showed that the truncated expression of a dominant negative of EGFR in proximal tubular cells decreased the infiltration of mononuclear cells, the accumulation of interstitial collagen, and renal tubular proliferation [249]. In diabetic rats, treatment with EGFR kinase inhibitors decreased the proliferation of tubuloepithelial cells, in addition to increase glomerular size [77]. In experimental models of hypertension induced by several factors (Ang II, leptin, monocrotaline, or ET1), EGFR blockade by different approaches including antisense oligonucleotides for EGFR, inhibitors of the EGFR kinase, and mutated WAVED-2 mice reduced the characteristic effects of tissue damage observed in these models [250–253]. Systemic administration of Ang II induces severe fibrotic lesions in the kidney. However, the infusion of this peptide in mice that express a dominant negative form of the renal tubular-specific EGFR, protected them against the lesions produced by Ang II. In addition, it has been observed that in knockout mice for TGFA and in mice treated with a specific inhibitor of ADAM17, renal fibrosis induced by Ang II decreases [52].

The origin of the study of the EGFR signaling pathway was in tumor pathology [254, 255]. In various types of cancer, including tumors of the head, neck, lung, and breast and colorectal tumors, the ErbB family of receptors (EGFR/HER1/ERBB1, HER2/neu/ERBB2, HER3/ERBB3, and HER4/ERBB4) is unregulated, producing an inappropriate cell stimulation [254, 256]. In malignant tumors, it has been described that HER2 and EGFR/HER1 are overexpressed and it has been established that overexpression of EGFR correlates with a worse clinical prognosis [257]. In the specific case of lung cancer, EGFR overexpression has been described in 90% of tumors. Several mechanisms can trigger an aberrant expression of EGFR, including in particular the overexpression of the protein, its gene amplification, appearance of mutations, the overexpression of EGFR ligands, and finally the loss of the regulatory mechanisms of these processes [256]. It should be noted that mutations in this receptor are one of the indicators that correlate best with the efficacy of EGFR inhibitors [256]. Specifically, a marked beneficial effect and greater response to treatment with these EGFR inhibitors have been observed in patients with mutations in exon 19 (codons 746–750) and exon 21 (substitution of leucine by arginine in codon 858 (L858R)) of EGFR compared to patients without these mutations [258].

The EGFR signaling pathway plays a crucial role in tumor processes since it modulates the cell cycle, inhibits apoptosis, induces angiogenesis, and promotes the motility of cancer cells and metastasis [259]. The first therapeutic approaches against EGFR began with the development of reversible pharmacological inhibitors of EGFR such as gefitinib (competes with ATP to bind the intracellular tyrosine kinase domain of EGFR, preventing its phosphorylation). Subsequently, erlotinib was designed, which presented a better pharmacokinetic and toxicity profile [260]. However, the response to gefitinib and erlotinib did not improve survival and improvements were only observed in those patients with mutations in EGFR [261, 262]. Another newly developed inhibitor is afatinib, with dual specificity against EGFR/ERBB1 and HER2/ERBB2 [263]. Due to the involvement of these pathways in embryonic development and cell proliferation, most efforts so far are focused on anti-EGFR therapies. These therapies involve the use of tyrosine kinase inhibitors, which are small molecules that bind intracellularly and interfere with signaling of the receptor, and the use of monoclonal antibodies that block the extracellular domain of the EGFR kinase. Among the developed antibodies, cetuximab stands out, which improved the survival rates in patients with lung cancer and colorectal cancer in combination with chemotherapy [264, 265]. In a kidney cancer study, administration of a murine/human chimeric anti-EGFR antibody (C225) was shown to inhibit the growth of normal renal cell carcinoma explants in NUDE mice [266].

EGFR regulates vascular homeostasis and pathophysiology. Studies with spontaneously hypertensive rats showed that vascular smooth muscle cells expressed high levels of EGFR and increased proliferation [267]. In models of experimental hypertension, EGFR blockers reduced blood pressure elevation and improved vascular lesions [69, 250, 268–270]. In atherosclerosis, increased expression of EGFR and some of its ligands, such as HBEGF, were described in the different stages of the atherogenic process [135, 271–273]. EGFR activation has also been involved in the vascular complications of diabetes [274–276].

1.17. Future Perspectives

All these studies show the complexity of EGFR pathway activation and its involvement in the pathogenesis of kidney damage. The canonical EGFR ligand EGF participates in acute renal damage mainly regulating cell proliferation, and future studies focusing on its role in renal regeneration are important. The other official ligands, TGFA and HBEGF, have an important role in the process of EGFR transactivation, by modulating key factors of renal damage, including Ang II, aldosterone, and TWEAK, mainly by regulation of renal inflammation. The recently described EGFR ligand CTGF is a potential therapeutic target that exerts proinflammatory and fibrotic properties, although more research is needed to completely understand EGFR binding and its involvement in EGFR transactivation in vivo. These data suggest that inhibiting EGFR or some of its ligands is an interesting therapeutic strategy for CKD and future studies are warranted.

Abbreviations

AREG: | Amphiregulin
EPGN: | Epigen
aa: | Amino acids
ADAMs: | Membrane-anchored disintegrin metalloproteases
ADPKD: | Autosomal dominant polycystic kidney disease
AKI: | Acute kidney injury
AKT: | Protein kinase a
Ang II: | Angiotensin II
AP1: | Activator protein 1
BMP: | Bone morphogenetic protein
BTC: | Betacellulin
CCL3: | Chemokine (C-C motif) ligand 3
CCN2/CTGF: | Connective tissue growth factor
CKD: | Chronic kidney disease
COX2: | Cyclooxygenase 2
CYR61: | Protein rich in cysteines 61
EGF: | Epidermal growth factor
EGFR/c-ERBB1: | Epidermal growth factor receptor
EMT: | Epithelial mesenchymal transition
EPR: | Epiregulin
ERK: | Intracellular signal regulation kinase
ET1: | Endothelin-1
FGF: | Fibroblast growth factor
GMCSF: | Granulocyte macrophage colony-stimulating factor
GPCRs: | Receptors coupled to G proteins
HBEGF: | Heparin-binding epidermal growth factor
HER2/neu (ERBB2): | Receptor tyrosine-protein kinase erbB-2
HER3 (ERBB3): | Receptor tyrosine-protein kinase erbB-3
HER4 (ERBB4): | Receptor tyrosine-protein kinase erbB-4
HGF: | Hepatocyte growth factor
IGF: | Insulin-like growth factor
IL1B: | Interleukin 1 beta
IL4: | Interleukin 4
IL6: | Interleukin 6
IRI: | Ischemia/reperfusion injury
JNK: | c-Jun N-terminal kinase
LPA: | Lysophosphatidic acid
LPR: | Low-density protein
MAPK: | Protein kinases activated by mitogen
MCP1/CCL2: | Monocyte chemoattractant protein-1
MMPs: | Metalloproteinases
NFKB: | Nuclear factor-κB
NGF: | Nerve growth factor
NKCC1: | Na⁺/K⁺/2Cl⁻ cotransporter
PDGF: | Platelet-derived growth factor
PDGFRB: | Platelet-derived growth factor receptor beta
PA: | Palmitic acid
PI3K: | Phosphatidylinositol 3-kinase
PKC: | Protein kinase C
PLC: | Phospholipase C
RANTES/CCL5: | Regulated on activation, normal T expressed, and secreted
RORγt: | RAR-related orphan receptor gamma
ROS: | Reactive oxygen species
RTKs: | Receptors with tyrosine kinase activity
SMAD: | Mothers against decapentaplegic homolog
SRC: | Tyrosine-protein kinase
STAT3: | Signal transducer and activator of transcription 3
STZ: | Streptozotocin
TGFA: | Transforming growth factor-α
TGFB: | Transforming growth factor-β
Th17: | T helper 17 cells
TLR4: | Toll-like receptor 4
TNFA: | Tumor necrosis factor-α
TPA: | Tetradecanoyl-phorbol-13-acetate
TRKA: | Receptor of nerve growth factor A
VEGF: | Vascular endothelial growth factor
WTACE2: | Pharmacological inhibitor of tumor necrosis factor-alpha-converting enzyme (TACE)
αSMA: | α-Smooth muscle actin.

Conflicts of Interest

The authors declare that they have no conflicts of interest.

Acknowledgments

This work was supported by the Instituto de Salud Carlos III and Fondos FEDER European Union (PI014/00041, PI17/00119), Red de Investigación Renal (REDinREN; RD16/0009), Comunidad de Madrid (B2017/BMD-3751 NOVELREN-CM), and Sociedad Española de Nefrología. The “Juan de la Cierva de Formacion” training program of the Ministerio de Economía, Industria y Competitividad, Gobierno de España supported the salary of SR-M (FJCI-2016-29050).

References

A. Ortiz and B. Fernandez-Fernandez, “Humble kidneys predict mighty heart troubles,” The Lancet Diabetes and Endocrinology, vol. 3, no. 7, pp. 489–491, 2015.

H. M. Marquart, W. Hunkapiller, L. E. Hood, and G. J. Todaro, “Rat transforming growth factor type 1: structure and relation to epidermal growth factor,” Science, vol. 223, no. 4640, pp. 1079–1082, 1984.

D. Slamon, G. Clark, S. Wong, W. Levin, A. Ullrich, and W. McGuire, “Human breast cancer: correlation of relapse and survival with amplification of the HER-2/neu oncogene,” Science, vol. 235, no. 4785, pp. 177–182, 1987.

S. Higashiyama, J. A. Abraham, J. Miller, J. Fiddes, and M. Klagsbrun, “A heparin- binding growth factor secreted by macrophagelike cells that is related to EGF,” Science, vol. 251, no. 4996, pp. 936–939, 1991.

Y. Shing, G. Christofori, D. Hanahan et al., “Betacellulin: a mitogen from pancreatic beta cell tumors,” Science, vol. 259, no. 5101, pp. 1604–1607, 1993.

H. Toyoda, T. Komuasaki, D. Uchida et al., “Epiregulin, a novel epidermal growth factor with mitogenic activity for rat primary hepatocytes,” Journal of Biological Chemistry, vol. 270, no. 13, pp. 7495–7500, 1995.

S. Rayego-Mateos, R. Rodrigues-Díez, J. L. Morgado-Pascual et al., “Connective tissue growth factor is a new ligand of epidermal growth factor receptor,” Journal of Molecular Cell Biology, vol. 5, no. 5, pp. 323–335, 2013.

M. K. Phanish, S. K. Winn, and M. E. Dockrell, “Connective tissue growth factor-(CTGF, CCN2) – a marker, mediator and therapeutic target for renal fibrosis,” Nephron Experimental Nephrology, vol. 114, no. 3, pp. e83–e92, 2010.

C. M. O’Seaghdha, S. J. Hwang, N. A. Bhavsar et al., “Lower urinary connective tissue growth factor levels and incident CKD stage 3 in the general population,” American Journal of Kidney Diseases, vol. 57, no. 6, pp. 841–849, 2011.

B. L. Riser, P. Cortes, M. Denichilo et al., “Urinary CCN2 (CTGF) as a possible predictor of diabetic nephropathy: preliminary report,” Kidney International, vol. 64, no. 2, pp. 451–458, 2003.

F. W. Tam, B. L. Riser, K. Meeran, J. A. Rambow, C. D. Pusey, and A. H. Frankel, “Urinary monocyte chemoattractant protein-1 (MCP-1) and connective tissue growth factor (CCN2) as prognostic markers for progression of diabetic nephropathy,” Cytokine, vol. 47, no. 1, pp. 37–42, 2009.

M. C. Slagman, T. Q. Nguyen, F. Waanders et al., “Effects of antiproteinuric intervention on elevated connective tissue growth factor (CTGF/CCN-2) plasma and urine levels in nondiabetic nephropathy,” Clinical Journal of the American Society of Nephrology, vol. 6, no. 8, pp. 1845–1850, 2011.

N. Koitabashi, M. Arai, K. Niwano et al., “Plasma connective tissue growth factor is a novel potential biomarker of cardiac dysfunction in patients with chronic heart failure,” European Journal of Heart Failure, vol. 10, no. 4, pp. 373–379, 2008.

J. Bao, Z. Tu, J. Wang et al., “A novel accurate rapid ELISA for detection of urinary connective tissue growth factor, a biomarker of chronic allograft nephropathy,” Transplantation Proceedings, vol. 40, no. 7, pp. 2361–2364, 2008.

D. S. Bergestuen, J. Gravning, K. H. Haugaa et al., “Plasma CCN2/connective tissue growth factor is associated with right ventricular dysfunction in patients with neuroendocrine tumors,” BMC Cancer, vol. 10, no. 1, p. 6, 2010.

T. Holbro and N. E. Hynes, “Erb B receptors: directing key signaling networks throughout life,” Annual Review of Pharmacology and Toxicology, vol. 44, no. 1, pp. 195–217, 2004.

J. T. Jones, R. W. Akita, and M. X. Sliwkowski, “Binding specificities and affinities of egf domains for Erb B receptors,” FEBS Letters, vol. 447, no. 2-3, pp. 227–231, 1999.

J. M. Sanders, M. E. Wampole, M. L. Thakur, and E. Wickstrom, “Molecular determinants of epidermal growth factor binding: a molecular dynamics study,” PLoS One, vol. 8, no. 1, article e54136, 2013.

B. Singh, G. Bogatcheva, M. K. Washington, and R. J. Coffey, “Transformation of polarized epithelial cells by apical mistrafficking of epiregulin,” Proceedings of the National Academy of Sciences of the United States of America, vol. 110, no. 22, pp. 8960–8965, 2013.

J. N. Higginbotham, Q. Zhang, D. K. Jeppesen et al., “Identification and characterization of EGF receptor in individual exosomes by fluorescence-activated vesicle sorting,” Journal of Extracellular Vesicles, vol. 5, no. 1, article 29254, 2016.

H. Tada, R. Sasada, Y. Kawaguchi et al., “Processing and juxtacrine activity of membrane-anchored betacellulin,” Journal of Cellular Biochemistry, vol. 72, no. 3, pp. 423–434, 1999.

S. Inui, S. Higashiyama, K. Hashimoto, M. Higashiyama, K. Yoshikawa, and N. Taniguchi, “Possible role of coexpression of CD9 with membrane-anchored heparin-binding EGF-like growth factor and amphiregulin in cultured human keratinocyte growth,” Journal of Cellular Physiology, vol. 171, no. 3, pp. 291–298, 1997.

P. Anklesaria, J. Teixido, M. Laiho, J. H. Pierce, J. S. Greenberger, and J. Massague, “Cell-cell adhesion mediated by binding of membrane-anchored transforming growth factor alpha to epidermal growth factor receptors promotes cell proliferation,” Proceedings of the National Academy of Sciences of the United States of America, vol. 87, no. 9, pp. 3289–3293, 1990.

R. Iwamoto and E. Mekada, “Heparin-binding EGF-like growth factor: a juxtacrine growth factor,” Cytokine & Growth Factor Reviews, vol. 11, no. 4, pp. 335–344, 2000.

A. B. Singh, K. Sugimoto, P. Dhawan, and R. C. Harris, “Juxtacrine activation of EGFR regulates claudin expression and increases transepithelial resistance,” American Journal of Physiology Cell Physiology, vol. 293, no. 5, pp. C1660–C1668, 2007.

O. M. Fischer, S. Hart, A. Gschwind, and A. Ullrich, “EGFR signal transactivation in cancer cells,” Biochemical Society Transactions, vol. 31, no. 6, pp. 1203–1208, 2003.

X. Yu, K. D. Sharma, T. Takahashi, R. Iwamoto, and E. Mekada, “Ligand-independent Dimer Formation of Epidermal Growth Factor Receptor (EGFR) Is a Step Separable from Ligand-induced EGFR Signaling,” Molecular Biology of the Cell, vol. 13, no. 7, pp. 2547–2557, 2002.

M. Rojas, S. Yao, and Y. Z. Lin, “Controlling epidermal growth factor (EGF)-stimulated Ras activation in intact cells by a cell-permeable peptide mimicking phosphorylated EGF receptor,” The Journal of Biological Chemistry, vol. 271, no. 44, pp. 27456–27461, 1996.

J. Pourazar, A. Blomberg, F. J. Kelly et al., “Diesel exhaust increases EGFR and phosphorylated C-terminal Tyr 1173 in the bronchial epithelium,” Particle and Fibre Toxicology, vol. 5, no. 1, p. 8, 2008.

J. S. Biscardi, M. C. Maa, D. A. Tice, M. E. Cox, T.-H. Leu, and S. J. Parsons, “c-Src-mediated phosphorylation of the epidermal growth factor receptor on Tyr⁸⁴⁵ and Tyr¹¹⁰¹ is associated with modulation of receptor function,” Journal of Biological Chemistry, vol. 274, no. 12, pp. 8335–8343, 1999.

W. Wu, L. M. Graves, G. N. Gill, S. J. Parsons, and J. M. Samet, “Src-dependent phosphorylation of the epidermal growth factor receptor on tyrosine 845 is required for zinc-induced Ras activation,” Journal of Biological Chemistry, vol. 277, no. 27, pp. 24252–24257, 2002.

S. S. Hobbs, J. A. Goettel, D. Liang et al., “TNF transactivation of EGFR stimulates cytoprotective COX-2 expression in gastrointestinal epithelial cells,” American Journal of Physiology Gastrointestinal and Liver Physiology, vol. 301, no. 2, pp. G220–G229, 2011.

M. Ebi, H. Kataoka, T. Shimura et al., “TGFβ induces pro HB-EGF shedding and EGFR transactivation through ADAM activation in gastric cancer cells,” Biochemical and Biophysical Research Communications, vol. 402, no. 3, pp. 449–454, 2010.

H. Daub, C. Wallasch, A. Lankenau, A. Herrlich, and A. Ullrich, “Signal characteristics of G protein- transactivated EGF receptor,” The EMBO Journal, vol. 16, no. 23, pp. 7032–7044, 1997.

H. Daub, F. U. Weiss, C. Wallasch, and A. Ullrich, “Role of transactivation of the EGF receptor in signalling by G-protein-coupled receptors,” Nature, vol. 379, no. 6565, pp. 557–560, 1996.

P. O. Hackel, E. Zwick, N. Prenzel, and A. Ullrich, “Epidermal growth factor receptors: critical mediators of multiple receptor pathways,” Current Opinion in Cell Biology, vol. 11, no. 2, pp. 184–189, 1999.

L. M. Luttrell, Y. Daaka, and R. J. Lefkowitz, “Regulation of tyrosine kinase cascades by G-protein- coupled receptors,” Current Opinion in Cell Biology, vol. 11, no. 2, pp. 177–183, 1999.

S. Rayego-Mateos, J. L. Morgado-Pascual, A. B. Sanz et al., “TWEAK transactivation of the epidermal growth factor receptor mediates renal inflammation,” The Journal of Pathology, vol. 231, no. 4, pp. 480–494, 2013.

H. Kodama, K. Fukuda, T. Takahashi et al., “Role of EGF receptor and Pyk2 in endothelin-1-induced ERK activation in rat cardiomyocytes,” Journal of Molecular and Cellular Cardiology, vol. 34, no. 2, pp. 139–150, 2002.

S. P. Soltoff, “Related adhesion focal tyrosine kinase and the epidermal growth factor receptor mediate the stimulation of mitogen- activated protein kinase by the G-protein- coupled P2Y2 receptor. Phorbol ester or [Ca²⁺]i elevation can substitute for receptor activation,” The Journal of Biological Chemistry, vol. 273, no. 36, pp. 23110–23117, 1998.

W. Tsai, A. D. Morielli, and E. G. Peralta, “The m1 muscarinic acetylcholine receptor transactivates the EGF receptor to modulate ion channel activity,” The EMBO Journal, vol. 16, no. 15, pp. 4597–4605, 1997.

W. B. Melenhorst, G. M. Mulder, Q. Xi et al., “Epidermal growth factor receptor signaling in the kidney: key roles in physiology and disease,” Hypertension, vol. 52, no. 6, pp. 987–993, 2008.

D. Bokemeyer, U. Schmitz, and H. J. Kramer, “Angiotensin II-induced growth of vascular smooth muscle cells requires an Src-dependent activation of the epidermal growth factor receptor,” Kidney International, vol. 58, no. 2, pp. 549–558, 2000.

B. H. Shah, M. P. Farshori, A. Jambusaria, and K. J. Catt, “Roles of Src and epidermal growth factor receptor transactivation in transient and sustained ERK1/2 responses to gonadotropin -releasing hormone receptor activation,” Journal of Biological Chemistry, vol. 278, no. 21, pp. 19118–19126, 2003.

L. M. Luttrell, G. J. Della Rocca, T. van Biesen, D. K. Luttrell, and R. J. Lefkowitz, “Gβγ subunits mediate Src-dependent phosphorylation of the epidermal growth factor receptor. A scaffold for G protein-coupled receptor-mediated Ras activation,” Journal of Biological Chemistry, vol. 272, no. 7, pp. 4637–4644, 1997.

S. Zhuang, G. R. Kinsey, K. Rasbach, and R. G. Schnellmann, “Heparin-binding epidermal growth factor and Src family kinases in proliferation of renal epithelial cells,” American Journal of Physiology Renal Physiology, vol. 294, no. 3, pp. F459–F468, 2008.

J. Schlöndorff and C. P. Blobel, “Metalloprotease-disintegrins: modular proteins capable of promoting cell-cell interactions and triggering signals by protein-ectodomain shedding,” Journal of Cell Science, vol. 112, pp. 3603–3617, 1999.

C. P. Blobel, T. G. Wolfsberg, C. W. Turck, D. G. Myles, P. Primakoff, and J. M. White, “A potential fusion peptide and an integrin ligand domain in a protein active in sperm-egg fusion,” Nature, vol. 356, no. 6366, pp. 248–252, 1992.

Y. Fukata, H. Adesnik, T. Iwanaga, D. S. Bredt, R. A. Nicoll, and M. Fukata, “Epilepsy-related ligand/receptor complex LGI1 and ADAM22 regulate synaptic transmission,” Science, vol. 313, no. 5794, pp. 1792–1795, 2006.

D. R. Edwards, M. M. Handsley, and C. J. Pennington, “The ADAM metalloproteinases,” Molecular Aspects of Medicine, vol. 29, no. 5, pp. 258–289, 2008.

A. P. Huovila, A. J. Turner, M. Pelto-Huikko, I. Kärkkäinen, and R. M. Ortiz, “Shedding light on ADAM metalloproteinases,” Trends in Biochemical Sciences, vol. 30, no. 7, pp. 413–422, 2005.

A. Lautrette, S. Li, R. Alili et al., “Angiotensin II and EGF receptor cross talk in chronic kidney diseases: a new therapeutic approach,” Nature Medicine, vol. 11, no. 8, pp. 867–874, 2005.

M. Asakura, M. Kitakaze, S. Takashima et al., “Cardiac hypertrophy is inhibited by antagonism of ADAM12 processing of HB-EGF: metalloproteinase inhibitors as a new therapy,” Nature Medicine, vol. 8, no. 1, pp. 35–40, 2002.

K. Reiss and S. Bhakdi, “The plasma membrane: penultimate regulator of ADAM sheddase function,” Biochimica et Biophysica Acta (BBA) - Molecular Cell Research, vol. 1864, no. 11, pp. 2082–2087, 2017.

D. Dreymueller and A. Ludwig, “Considerations on inhibition approaches for proinflammatory functions of ADAM proteases,” Platelets, vol. 28, no. 4, pp. 354–361, 2017.

R. Bianco, T. Gelardi, V. Damiano, F. Ciardiello, and G. Tortora, “Rational bases for the development of EGFR inhibitors for cancer treatment,” The International Journal of Biochemistry & Cell Biology, vol. 39, no. 7-8, pp. 1416–1431, 2007.

R. I. Nicholson, J. M. Gee, and M. E. Harper, “EGFR and cancer prognosis,” European Journal of Cancer, vol. 37, Supplement 4, pp. 9–15, 2001.

A. Stratigos, C. Garbe, C. Lebbe et al., “Diagnosis and treatment of invasive squamous cell carcinoma of the skin: European consensus-based interdisciplinary guideline,” European Journal of Cancer, vol. 51, no. 14, pp. 1989–2007, 2015.

S. Pastore, E. Gubinelli, L. Leoni, D. Raskovic, and L. Korkina, “Biological drugs targeting the immune response in the therapy of psoriasis,” Biologics: Targets and Theraphy, vol. 2, no. 4, pp. 687–697, 2008.

G. Fabbrocini, L. Panariello, G. Caro, and S. Cacciapuoti, “Acneiform rash induced by EGFR inhibitors: review of the literature and new insights,” Skin Appendage Disorders, vol. 1, pp. 31–37, 2015.

K. Okamoto, H. Maeda, T. Shiga et al., “Cetuximab and panitumumab in a patient with colon cancer and concomitant chronic skin disease: a potential beneficial effect on psoriasis vulgaris,” World Journal of Gastroenterology, vol. 21, no. 12, pp. 3746–3749, 2015.

K. Yoshioka, T. Takemura, K. Murakami et al., “Identification and localization of epidermal growth factor and its receptor in the human glomerulus,” Laboratory Investigation, vol. 63, no. 2, pp. 189–196, 1990.

B. Sis, S. Sarioglu, A. Celik, M. Zeybel, A. Soylu, and S. Bora, “Epidermal growth factor receptor expression in human renal allograft biopsies: an immunohistochemical study,” Transplant Immunology, vol. 13, no. 3, pp. 229–232, 2004.

L. Nakopoulou, K. Stefanaki, J. Boletis et al., “Immunohistochemical study of epidermal growth factor receptor (EGFR) in various types of renal injury,” Nephrology Dialysis Transplantation, vol. 9, pp. 764–769, 1994.

T. Takemura, Y. Murata, S. Hino et al., “Heparin-binding EGF-like growth factor is expressed by mesangial cells and is involved in mesangial proliferation in glomerulonephritis,” The Journal of Pathology, vol. 189, no. 3, pp. 431–438, 1999.

M. K. Hise, M. Salmanullah, L. Liu, C. I. Drachenberg, J. C. Papadimitriou, and R. M. Rohan, “Control of the epidermal growth factor receptor and its ligands during renal injury,” Nephron, vol. 88, no. 1, pp. 71–79, 2001.

T. Homma, M. Sakai, H. F. Cheng, T. Yasuda, R. J. Coffey Jr, and R. C. Harris, “Induction of heparin-binding epidermal growth factor-like growth factor mRNA in rat kidney after acute injury,” The Journal of Clinical Investigation, vol. 96, no. 2, pp. 1018–1025, 1995.

M. Sakai, M. Zhang, T. Homma et al., “Production of heparin binding epidermal growth factor-like growth factor in the early phase of regeneration after acute renal injury. Isolation and localization of bioactive molecules,” The Journal of Clinical Investigation, vol. 99, no. 9, pp. 2128–2138, 1997.

M. Flamant, G. Bollée, C. Hénique, and P.-L. Tharaux, “Epidermal growth factor: a new therapeutic target in glomerular disease,” Nephrology, Dialysis, Transplantation, vol. 27, no. 4, pp. 1297–1304, 2012.

S. Rayego-Mateos, J. L. Morgado-Pascual, R. R. Rodrigues-Diez et al., “Connective tissue growth factor induces renal fibrosis via epidermal growth factor receptor activation,” The Journal of Pathology, vol. 244, no. 2, pp. 227–241, 2018.

Z. Wang, J. K. Chen, S. W. Wang, G. Moeckel, and R. C. Harris, “Importance of functional EGF receptors in recovery from acute nephrotoxic injury,” Journal of the American Society of Nephrology, vol. 14, no. 12, pp. 3147–3154, 2003.

J. Chen, J. K. Chen, and R. C. Harris, “Deletion of the epidermal growth factor receptor in renal proximal tubule epithelial cells delays recovery from acute kidney injury,” Kidney International, vol. 82, no. 1, pp. 45–52, 2012.

H. D. Humes, D. A. Cieslinski, T. M. Coimbra, J. M. Messana, and C. Galvao, “Epidermal growth factor enhances renal tubule cell regeneration and repair and accelerates the recovery of renal function in postischemic acute renal failure,” The Journal of Clinical Investigation, vol. 84, no. 6, pp. 1757–1761, 1989.

R. L. Chevalier, S. Goyal, and B. A. Thornhill, “EGF improves recovery following relief of unilateral ureteral obstruction in the neonatal rat,” The Journal of Urology, vol. 162, no. 4, pp. 1532–1536, 1999.

A. B. Singh, K. Sugimoto, and R. C. Harris, “Juxtacrine activation of epidermal growth factor (EGF) receptor by membrane-anchored heparin-binding EGF-like growth factor protects epithelial cells from anoikis while maintaining an epithelial phenotype,” Journal of Biological Chemistry, vol. 282, no. 45, pp. 32890–32901, 2007.

S. Zhuang, Y. Dang, and R. G. Schnellmann, “Requirement of the epidermal growth factor receptor in renal epithelial cell proliferation and migration,” American Journal of Physiology Renal Physiology, vol. 287, no. 3, pp. F365–F372, 2004.

L. Wassef, D. J. Kelly, and R. E. Gilbert, “Epidermal growth factor receptor inhibition attenuates early kidney enlargement in experimental diabetes,” Kidney International, vol. 66, no. 5, pp. 1805–1814, 2004.

S. Zhuang, Y. Yan, R. A. Daubert, and R. G. Schnellmann, “Epiregulin promotes proliferation and migration of renal proximal tubular cells,” American Journal of Physiology Renal Physiology, vol. 293, no. 1, pp. F219–F226, 2007.

F. Zeng, A. B. Singh, and R. C. Harris, “The role of the EGF family of ligands and receptors in renal development, physiology and pathophysiology,” Experimental Cell Research, vol. 315, no. 4, pp. 602–610, 2009.

S. C. Kiley, B. A. Thornhill, B. C. Belyea et al., “Epidermal growth factor potentiates renal cell death in hydronephrotic neonatal mice, but cell survival in rats,” Kidney International, vol. 68, no. 2, pp. 504–514, 2005.

Y. Wada, M. Iyoda, K. Matsumoto et al., “Epidermal growth factor receptor inhibition with erlotinib partially prevents cisplatin-induced nephrotoxicity in rats,” PLoS One, vol. 9, no. 11, article e111728, 2014.

R. C. Harris, E. Chung, and R. J. Coffey, “EGF receptor ligands,” Experimental Cell Research, vol. 284, no. 1, pp. 2–13, 2003.

T. P. Garrett, N. M. McKern, M. Lou et al., “Crystal structure of a truncated epidermal growth factor receptor extracellular domain bound to transforming growth factor α,” Cell, vol. 110, no. 6, pp. 763–773, 2002.

G. V. Louie, W. Yang, M. E. Bowman, and S. Choe, “Crystal structure of the complex of diphtheria toxin with an extracellular fragment of its receptor,” Molecular Cell, vol. 1, no. 1, pp. 67–78, 1997.

K. Miura, H. Doura, T. Aizawa et al., “Solution structure of betacellulin, a new member of EGF-family ligands,” Biochemical and Biophysical Research Communications, vol. 294, no. 5, pp. 1040–1046, 2002.

K. Sato, T. Nakamura, M. Mizuguchi et al., “Solution structure of epiregulin and the effect of its C-terminal domain for receptor binding affinity,” FEBS Letters, vol. 553, no. 3, pp. 232–238, 2003.

K. Frazier, S. Williams, D. Kothapalli, H. Klapper, and G. R. Grotendorst, “Stimulation of fibroblast cell growth, matrix production, and granulation tissue formation by connective tissue growth factor,” The Journal of Investigative Dermatology, vol. 107, no. 3, pp. 404–411, 1996.

M. L. Kireeva, F. E. Mo, G. P. Yang, and L. F. Lau, “Cyr61, a product of a growth factor-inducible immediate-early gene, promotes cell proliferation, migration, and adhesion,” Molecular and Cellular Biology, vol. 16, no. 4, pp. 1326–1334, 1996.

L. Uttarwar, F. Peng, D. Wu et al., “HB-EGF release mediates glucose-induced activation of the epidermal growth factor receptor in mesangial cells,” American Journal of Physiology Renal Physiology, vol. 300, no. 4, pp. F921–F931, 2011.

R. Li, L. Uttarwar, B. Gao et al., “High glucose up-regulates ADAM17 through HIF-1α in mesangial cells,” Journal of Biological Chemistry, vol. 290, no. 35, pp. 21603–21614, 2015.

M. Dey, A. Baldys, D. B. Sumter et al., “Bradykinin decreases podocyte permeability through ADAM17-dependent epidermal growth factor receptor activation and zonula occludens-1 rearrangement,” The Journal of Pharmacology and Experimental Therapeutics, vol. 334, no. 3, pp. 775–783, 2010.

S. Cohen, “Purification of a nerve-growth promoting protein from the mouse salivary gland and its neuro-cytotoxic antiserum,” Proceedings of the National Academy of Sciences of the United States of America, vol. 46, no. 3, pp. 302–311, 1960.

D. A. Fisher, E. C. Salido, and L. Barajas, “Epidermal growth factor and the kidney,” Annual Review of Physiology, vol. 51, no. 1, pp. 67–80, 1989.

L. C. Read, F. M. Upton, G. L. Francis, J. C. Wallace, G. W. Dahlenberg, and F. John Ballard, “Changes in the growth-promoting activity of human milk during lactation,” Pediatric Research, vol. 18, no. 2, pp. 133–139, 1984.

B. Dvorak, “Milk epidermal growth factor and gut protection,” The Journal of Pediatrics, vol. 156, no. 2, pp. S31–S35, 2010.

T. Nojiri, T. Yoshizato, T. Fukami et al., “Clinical significance of amphiregulin and epidermal growth factor in colostrum,” Archives of Gynecology and Obstetrics, vol. 286, no. 3, pp. 643–647, 2012.

G. Carpenter and S. Cohen, “Epidermal growth factor,” Annual Review of Biochemistry, vol. 48, no. 1, pp. 193–216, 1979.

L. B. Rall, J. Scott, G. I. Bell et al., “Mouse prepro-epidermal growth factor synthesis by the kidney and other tissues,” Nature, vol. 313, no. 5999, pp. 228–231, 1985.

G. Parries, K. Chen, K. S. Misono, and S. Cohen, “The human urinary epidermal growth factor (EGF) precursor. Isolation of a biologically active 160-kilodalton heparin-binding pro-EGF with a truncated carboxyl terminus,” Journal of Biological Chemistry, vol. 270, no. 46, pp. 27954–27960, 1995.

R. C. Harris, “Potential physiologic roles for epidermal growth factor in the kidney,” American Journal of Kidney Diseases, vol. 17, no. 6, pp. 627–630, 1991.

L. Raaberg, E. Nexo, J. Damsgaard Mikkelsen, and S. Seier Poulsen, “Immunohistochemical localisation and developmental aspects of epidermal growth factor in the rat,” Histochemistry, vol. 89, no. 4, pp. 351–356, 1988.

N. N. Zheleznova, P. D. Wilson, and A. Staruschenko, “Epidermal growth factor-mediated proliferation and sodium transport in normal and PKD epithelial cells,” Biochimica et Biophysica Acta (BBA) - Molecular Basis of Disease, vol. 1812, no. 10, pp. 1301–1313, 2011.

F. O'Mahony, F. Toumi, M. S. Mroz, G. Ferguson, and S. J. Keely, “Induction of Na⁺/K⁺/2Cl⁻ cotransporter expression mediates chronic potentiation of intestinal epithelial Cl⁻ secretion by EGF,” American Journal of Physiology-Cell Physiology, vol. 294, no. 6, pp. C1362–C1370, 2008.

M. S. Mroz and S. J. Keely, “Epidermal growth factor chronically upregulates Ca²⁺-dependent Cl⁻ conductance and TMEM16A expression in intestinal epithelial cells,” The Journal of Physiology, vol. 590, no. 8, pp. 1907–1920, 2012.

N. T. Trinh, A. Privé, E. Maillé, J. Noël, and E. Brochiero, “EGF and K⁺ channel activity control normal and cystic fibrosis bronchial epithelia repair,” American Journal of Physiology Lung Cellular and Molecular Physiology, vol. 295, no. 5, pp. L866–L880, 2008.

V. H. Gattone, D. A. Lowden, and B. D. Cowley Jr., “Epidermal growth factor ameliorates autosomal recessive polycystic kidney disease in mice,” Developmental Biology, vol. 169, no. 2, pp. 504–510, 1995.

I. E. Veizis and C. U. Cotton, “Abnormal EGF-dependent regulation of sodium absorption in ARPKD collecting duct cells,” American Journal of Physiology Renal Physiology, vol. 288, no. 3, pp. F474–F482, 2005.

S. Ryan, S. Verghese, N. L. Cianciola, C. U. Cotton, and C. R. Carlin, “Autosomal recessive polycystic kidney disease epithelial cell model reveals multiple basolateral epidermal growth factor receptor sorting pathways,” Molecular Biology of the Cell, vol. 21, no. 15, pp. 2732–2745, 2010.

D. Zepeda-Orozco, H. M. Wen, B. A. Hamilton, N. S. Raikwar, and C. P. Thomas, “EGF regulation of proximal tubule cell proliferation and VEGF-A secretion,” Physiological Report, vol. 5, no. 18, article e13453, 2017.

S. D. Coaxum, M. G. Blanton, A. Joyner et al., “Epidermal growth factor-induced proliferation of collecting duct cells from Oak Ridge polycystic kidney mice involves activation of Na⁺/H⁺ exchanger,” American Journal of Physiology Cell Physiology, vol. 307, no. 6, pp. C554–C560, 2014.

P. Arda-Pirincci and S. Bolkent, “The role of epidermal growth factor in prevention of oxidative injury and apoptosis induced by intestinal ischemia/reperfusion in rats,” Acta Histochemica, vol. 116, no. 1, pp. 167–175, 2014.

J. Lorita, M. Soley, and I. Ramirez, “Epidermal growth factor protects the heart against low-flow ischemia-induced injury,” Journal of Physiology and Biochemistry, vol. 66, no. 1, pp. 55–62, 2010.

A. Hussein Ael, A. A. Shokeir, M. E. Sarhan et al., “Effects of combined erythropoietin and epidermal growth factor on renal ischaemia/reperfusion injury: a randomized experimental controlled study,” BJU International, vol. 107, no. 2, pp. 323–328, 2011.

G. Sirokmány, A. Pató, M. Zana et al., “Epidermal growth factor-induced hydrogen peroxide production is mediated by dual oxidase 1,” Free Radical Biology and Medicine, vol. 97, pp. 204–211, 2016.

B. Singh, M. Schneider, P. Knyazev, and A. Ullrich, “UV-induced EGFR signal transactivation is dependent on proligand shedding by activated metalloproteases in skin cancer cell lines,” International Journal of Cancer, vol. 124, no. 3, pp. 531–539, 2009.

A. Knebel, H. J. Rahmsdorf, A. Ullrich, and P. Herrlich, “Dephosphorylation of receptor tyrosine kinases as target of regulation by radiation, oxidants or alkylating agents,” The EMBO Journal, vol. 15, no. 19, pp. 5314–5325, 1996.

S. Tomic, U. Greiser, R. Lammers et al., “Association of SH2 domain protein tyrosine phosphatases with the epidermal growth factor receptor in human tumor cells. Phosphatidic acid activates receptor dephosphorylation by PTP1C,” Journal of Biological Chemistry, vol. 270, no. 36, pp. 21277–21284, 1995.

D. E. Heppner and A. van der Vliet, “Redox-dependent regulation of epidermal growth factor receptor signaling,” Redox Biology, vol. 8, pp. 24–27, 2016.

R. Bellomo, J. A. Kellum, and C. Ronco, “Acute kidney injury,” The Lancet, vol. 380, no. 9843, pp. 756–766, 2012.

X. Wen, R. Murugan, Z. Peng, and J. A. Kellum, “Pathophysiology of acute kidney injury: a new perspective,” Contributions to Nephrology, vol. 165, pp. 39–45, 2010.

L. G. Gomella, E. R. Sargent, T. P. Wade, P. Anglard, W. M. Linehan, and A. Kasid, “Expression of transforming growth factor α in normal human adult kidney and enhanced expression of transforming growth factors α and β1 in renal cell carcinoma,” Cancer Research, vol. 49, 24, Part 1, pp. 6972–6975, 1989.

Y. C. Yeh, J. F. Tsai, L. Y. Chuang et al., “Elevation of transforming growth factor α and its relationship to the epidermal growth factor and α-fetoprotein levels in patients with hepatocellular carcinoma,” Cancer Research, vol. 47, no. 3, pp. 896–901, 1987.

D. Laouari, M. Burtin, A. Phelep et al., “TGF-α mediates genetic susceptibility to chronic kidney disease,” Journal of the American Society of Nephrology, vol. 22, no. 2, pp. 327–335, 2011.

J. L. Morgado-Pascual, S. Rayego-Mateos, J. M. Valdivielso, A. Ortiz, J. Egido, and M. Ruiz-Ortega, “Paricalcitol inhibits aldosterone-induced proinflammatory factors by modulating epidermal growth factor receptor pathway in cultured tubular epithelial cells,” BioMed Research International, vol. 2015, Article ID 783538, 13 pages, 2015.

L. Liu, B. J. Duke, B. Malik, Q. Yue, and D. C. Eaton, “Biphasic regulation of ENaC by TGF-α and EGF in renal epithelial cells,” American Journal of Physiology Renal Physiology, vol. 296, no. 6, pp. F1417–F1427, 2009.

C. Justicia and A. M. Planas, “Transforming growth factor-α acting at the epidermal growth factor receptor reduces infarct volume after permanent middle cerebral artery occlusion in rats,” Journal of Cerebral Blood Flow & Metabolism, vol. 19, no. 2, pp. 128–132, 1999.

R. R. Leker, Z. E. Toth, T. Shahar et al., “TGFα induces angiogenesis and neurogenesis following stroke,” Neuroscience, vol. 163, no. 1, pp. 233–243, 2009.

C. J. Xian, J. C. Cool, G. S. Howarth, and L. C. Read, “Effects of TGF-alpha gene knockout on epithelial cell kinetics and repair of methotrexate-induced damage in mouse small intestine,” Journal of Cellular Physiology, vol. 191, no. 1, pp. 105–115, 2002.

D. K. Madtes, A. L. Elston, R. C. Hackman, A. R. Dunn, and J. G. Clark, “Transforming growth factor-alpha deficiency reduces pulmonary fibrosis in transgenic mice,” American Journal of Respiratory Cell and Molecular Biology, vol. 20, no. 5, pp. 924–934, 1999.

C. J. Xian, L. Li, Y. S. Deng, S. P. Zhao, and X. F. Zhou, “Lack of effects of transforming growth factor-α gene knockout on peripheral nerve regeneration may result from compensatory mechanisms,” Experimental Neurology, vol. 172, no. 1, pp. 182–188, 2001.

D. K. Moscatello, M. Holgado-Madruga, D. R. Emlet, R. B. Montgomery, and A. J. Wong, “Constitutive activation of phosphatidylinositol 3-kinase by a naturally occurring mutant epidermal growth factor receptor,” Journal of Biological Chemistry, vol. 273, no. 1, pp. 200–206, 1998.

A. B. Singh, T. Tsukada, R. Zent, and R. C. Harris, “Membrane-associated HB-EGF modulates HGF-induced cellular responses in MDCK cells,” Journal of Cell Science, vol. 117, no. 8, pp. 1365–1379, 2004.

N. Prenzel, E. Zwick, H. Daub et al., “EGF receptor transactivation by G-protein-coupled receptors requires metalloproteinase cleavage of pro HB-EGF,” Nature, vol. 402, no. 6764, pp. 884–888, 1999.

Y. Shirakata, R. Kimura, D. Nanba et al., “Heparin-binding EGF-like growth factor accelerates keratinocyte migration and skin wound healing,” Journal of Cell Science, vol. 118, no. 11, pp. 2363–2370, 2005.

J. Miyagawa, S. Higashiyama, S. Kawata et al., “Localization of heparin-binding EGF-like growth factor in the smooth muscle cells and macrophages of human atherosclerotic plaques,” The Journal of Clinical Investigation, vol. 95, no. 1, pp. 404–411, 1995.

S. Fu, I. Bottoli, M. Goller, and P. K. Vogt, “Heparin-binding epidermal growth factor-like growth factor, a v-Jun target gene, induces oncogenic transformation,” Proceedings of the National Academy of Sciences of the United States of America, vol. 96, no. 10, pp. 5716–5721, 1999.

G. Bollee, M. Flamant, S. Schordan et al., “Epidermal growth factor receptor promotes glomerular injury and renal failure in rapidly progressive crescentic glomerulonephritis,” Nature Medicine, vol. 17, no. 10, pp. 1242–1250, 2011.

T. Miyazawa, F. Zeng, S. Wang et al., “Low nitric oxide bioavailability upregulates renal heparin binding EGF-like growth factor expression,” Kidney International, vol. 84, no. 6, pp. 1176–1188, 2013.

F. Zeng, L. A. Kloepfer, C. Finney, A. Diedrich, and R. C. Harris, “Specific endothelial heparin-binding EGF-like growth factor deletion ameliorates renal injury induced by chronic angiotensin II infusion,” American Journal of Physiology Renal Physiology, vol. 311, no. 4, pp. F695–F707, 2016.

K. Hashimoto, S. Higashiyama, H. Asada et al., “Heparin-binding epidermal growth factor-like growth factor is an autocrine growth factor for human keratinocytes,” Journal of Biological Chemistry, vol. 269, pp. 20060–20066, 1994.

J. P. Smith, A. Pozzi, P. Dhawan, A. B. Singh, and R. C. Harris, “Soluble HB-EGF induces epithelial-to-mesenchymal transition in inner medullary collecting duct cells by upregulating Snail-2,” American Journal of Physiology Renal Physiology, vol. 296, no. 5, pp. F957–F965, 2009.

C. Berasain and M. A. Avila, “Amphiregulin,” Seminars in Cell & Developmental Biology, vol. 28, pp. 31–41, 2014.

L. Schuger, G. R. Johnson, K. Gilbride, G. D. Plowman, and R. Mandel, “Amphiregulin in lung branching morphogenesis: interaction with heparan sulfate proteoglycan modulates cell proliferation,” Development, vol. 122, no. 6, pp. 1759–1767, 1996.

P. W. Cook, M. R. Pittelkow, and G. D. Shipley, “Growth factor-independent proliferation of normal human neonatal keratinocytes: production of autocrine- and paracrine-acting mitogenic factors,” Journal of Cellular Physiology, vol. 146, no. 2, pp. 277–289, 1991.

C. Berasain, E. R. García-Trevijano, J. Castillo et al., “Amphiregulin: an early trigger of liver regeneration in mice,” Gastroenterology, vol. 128, no. 2, pp. 424–432, 2005.

C. Meulenbroeks, H. van Weelden, C. Schwartz et al., “Basophil-derived amphiregulin is essential for UVB irradiation-induced immune suppression,” The Journal of Investigative Dermatology, vol. 135, no. 1, pp. 222–228, 2015.

M. J. Perugorria, M. U. Latasa, A. Nicou et al., “The epidermal growth factor receptor ligand amphiregulin participates in the development of mouse liver fibrosis,” Hepatology, vol. 48, no. 4, pp. 1251–1261, 2008.

D. M. Zaiss, L. Yang, P. R. Shah, J. J. Kobie, J. F. Urban, and T. R. Mosmann, “Amphiregulin, a TH2 cytokine enhancing resistance to nematodes,” Science, vol. 314, no. 5806, article 1746, 2006.

D. Burzyn, W. Kuswanto, D. Kolodin et al., “A special population of regulatory T cells potentiates muscle repair,” Cell, vol. 155, no. 6, pp. 1282–1295, 2013.

L. A. Monticelli, G. F. Sonnenberg, M. C. Abt et al., “Innate lymphoid cells promote lung-tissue homeostasis after infection with influenza virus,” Nature Immunology, vol. 12, no. 11, pp. 1045–1054, 2011.

Y. Qi, D. J. Operario, C. M. Oberholzer et al., “Human basophils express amphiregulin in response to T cell–derived IL-3,” Journal of Allergy and Clinical Immunology, vol. 126, no. 6, pp. 1260–1266.e4, 2010.

C. Meng, G. Liu, H. Mu, M. Zhou, S. Zhang, and Y. Xu, “Amphiregulin may be a new biomarker of classically activated macrophages,” Biochemical and Biophysical Research Communications, vol. 466, no. 3, pp. 393–399, 2015.

L. Zhan, L. Zheng, T. Hosoi, Y. Okuma, and Y. Nomura, “Stress-induced neuroprotective effects of epiregulin and amphiregulin,” PLoS One, vol. 10, no. 2, article e0118280, 2015.

G. Aguiari, F. Bizzarri, A. Bonon et al., “Polycystin-1 regulates amphiregulin expression through CREB and AP1 signalling: implications in ADPKD cell proliferation,” Journal of Molecular Medicine, vol. 90, no. 11, pp. 1267–1282, 2012.

J. Chen and R. C. Harris, “Interaction of the EGF receptor and the Hippo pathway in the diabetic kidney,” Journal of the American Society of Nephrology, vol. 27, no. 6, pp. 1689–1700, 2016.

S. Zhuang and N. Liu, “EGFR signaling in renal fibrosis,” Kidney International Supplements, vol. 4, no. 1, pp. 70–74, 2014.

M. R. Schneider, M. Dahlhoff, N. Herbach et al., “Betacellulin overexpression in transgenic mice causes disproportionate growth, pulmonary hemorrhage syndrome, and complex eye pathology,” Endocrinology, vol. 146, no. 12, pp. 5237–5246, 2005.

L. Fang, J. C. Cheng, H. M. Chang, Y. P. Sun, and P. C. K. Leung, “EGF-like growth factors induce COX-2-derived PGE2 production through ERK1/2 in human granulosa cells,” The Journal of Clinical Endocrinology and Metabolism, vol. 98, no. 12, pp. 4932–4941, 2013.

M. Harada, D. Kamimura, Y. Arima et al., “Temporal expression of growth factors triggered by epiregulin regulates inflammation development,” Journal of Immunology, vol. 194, no. 3, pp. 1039–1046, 2015.

M. Dahlhoff, H. Algül, J. T. Siveke et al., “Betacellulin protects from pancreatitis by activating stress-activated protein kinase,” Gastroenterology, vol. 138, no. 4, pp. 1585–1594.e3, 2010.

M. Murakami, M. Harada, D. Kamimura et al., “Disease-association analysis of an inflammation-related feedback loop,” Cell Reports, vol. 3, no. 3, pp. 946–959, 2013.

S. Sugiyama, K. Nakabayashi, I. Baba, T. Sasazuki, and S. Shirasawa, “Role of epiregulin in peptidoglycan-induced proinflammatory cytokine production by antigen presenting cells,” Biochemical and Biophysical Research Communications, vol. 337, no. 1, pp. 271–274, 2005.

Y. Zhang, T. Kobayashi, Y. Hayashi et al., “Important role of epiregulin in inflammatory responses during corneal epithelial wound healing,” Investigative Ophthalmology & Visual Science, vol. 53, no. 4, pp. 2414–2423, 2012.

J. S. Boyles, S. Atwell, Z. Druzina, J. G. Heuer, and D. R. Witcher, “Structural basis of selectivity and neutralizing activity of a TGFα/epiregulin specific antibody,” Protein Science, vol. 25, no. 11, pp. 2028–2036, 2016.

L. Strachan, J. G. Murison, R. L. Prestidge, M. A. Sleeman, J. D. Watson, and K. D. Kumble, “Cloning and biological activity of epigen, a novel member of the epidermal growth factor superfamily,” Journal of Biological Chemistry, vol. 276, no. 21, pp. 18265–18271, 2001.

M. R. Schneider and E. Wolf, “The epidermal growth factor receptor ligands at a glance,” Journal of Cellular Physiology, vol. 218, no. 3, pp. 460–466, 2009.

M. Dahlhoff, D. Frances, J. E. Kloepper et al., “Overexpression of epigen during embryonic development induces reversible, epidermal growth factor receptordependent sebaceous gland hyperplasia,” Molecular and Cellular Biology, vol. 34, no. 16, pp. 3086–3095, 2014.

M. Schäfer, A. H. Willrodt, S. Kurinna et al., “Activation of Nrf2 in keratinocytes causes chloracne (MADISH)‐like skin disease in mice,” EMBO Molecular Medicine, vol. 6, no. 4, pp. 442–457, 2014.

M. Dahlhoff, D. Emrich, E. Wolf, and M. R. Schneider, “Increased activation of the epidermal growth factor receptor in transgenic mice overexpressing epigen causes peripheral neuropathy,” Biochimica et Biophysica Acta (BBA) - Molecular Basis of Disease, vol. 1832, no. 12, pp. 2068–2076, 2013.

H. Sakai, K. Sato, F. Sato et al., “Curcumin inhibits epigen and amphiregulin upregulated by 2, 4, 6-trinitrochlorobenzene associated with attenuation of skin swelling,” Inflammation Research, vol. 66, no. 8, pp. 663–678, 2017.

B. S. Kochupurakkal, D. Harari, A. Di-Segni et al., “Epigen, the last ligand of ErbB receptors, reveals intricate relationships between affinity and mitogenicity,” Journal of Biological Chemistry, vol. 280, no. 9, pp. 8503–8512, 2005.

R. Rosell, T. Moran, C. Queralt et al., “Screening for epidermal growth factor receptor mutations in lung cancer,” The New England Journal of Medicine, vol. 361, no. 10, pp. 958–967, 2009.

K. S. Park, M. Raffeld, Y. W. Moon et al., “CRIPTO1 expression in EGFR-mutant NSCLC elicits intrinsic EGFR-inhibitor resistance,” The Journal of Clinical Investigation, vol. 124, no. 7, pp. 3003–3015, 2014.

A. Kirabo, S. Ryzhov, M. Gupte et al., “Neuregulin-1β induces proliferation, survival and paracrine signaling in normal human cardiac ventricular fibroblasts,” Journal of Molecular and Cellular Cardiology, vol. 105, pp. 59–69, 2017.

D. M. Bradham, A. Igarashi, R. L. Potter, and G. R. Grotendorst, “Connective tissue growth factor: a cysteine-rich mitogen secreted by human vascular endothelial cells is related to the SRC-induced immediate early gene product CEF-10,” Journal of Cell Biology, vol. 114, no. 6, pp. 1285–1294, 1991.

P. Bork, “The modular architecture of a new family of growth regulators related to connective tissue growth factor,” FEBS Letters, vol. 327, no. 2, pp. 125–130, 1993.

H. S. Kim, S. R. Nagalla, Y. Oh, E. Wilson, C. T. Roberts, and R. G. Rosenfeld, “Identification of a family of low-affinity insulin-like growth factor binding proteins (IGFBPs): characterization of connective tissue growth factor as a member of the IGFBP superfamily,” Proceedings of the National Academy of Sciences of the United States of America, vol. 94, no. 24, pp. 12981–12986, 1997.

S. Wang, M. Denichilo, C. Brubaker, and R. Hirschberg, “Connec tive tissue growth factor in tubulointerstitial injury of diabetic nephropathy,” Kidney International, vol. 60, no. 1, pp. 96–105, 2001.

S. Lam, R. N. van der Geest, N. A. M. Verhagen et al., “Connective tissue growth factor and IGF-I are produced by human renal fibroblasts and cooperate in the induction of collagen production by high glucose,” Diabetes, vol. 52, no. 12, pp. 2975–2983, 2003.

J. G. Abreu, N. I. Ketpura, B. Reversade, and E. M. de Robertis, “Connective-tissue growth factor (CTGF) modulates cell signalling by BMP and TGF-β,” Nature Cell Biology, vol. 4, no. 8, pp. 599–604, 2002.

J. C. Adams and R. P. Tucker, “The thrombospondin type 1 repeat (TSR) superfamily: diverse proteins with related roles in neuronal development,” Developmental Dynamics, vol. 218, no. 2, pp. 280–299, 2000.

I. Inoki, T. Shiomi, G. Hashimoto et al., “Connective tissue growth factor binds vascular endothelial growth factor (VEGF) and inhibits VEGF-induced angiogenesis,” The FASEB Journal, vol. 16, no. 2, pp. 219–221, 2002.

M. Hoshijima, T. Hattori, M. Inoue et al., “CT domain of CCN2/CTGF directly interacts with fibronectin and enhances cell adhesion of chondrocytes through integrin·α5β1,” FEBS Letters, vol. 580, no. 5, pp. 1376–1382, 2006.

J. Murray-Rust, N. Q. McDonald, T. L. Blundell et al., “Topological similarities in TGF-β2, PDGF-BB and NGF define a superfamily of polypeptide growth factors,” Structure, vol. 1, no. 2, pp. 153–159, 1993.

G. Hashimoto, I. Inoki, Y. Fujii, T. Aoki, E. Ikeda, and Y. Okada, “Matrix metalloproteinases cleave connective tissue growth factor and reactivate angiogenic activity of vascular endothelial growth factor 165,” Journal of Biological Chemistry, vol. 277, no. 39, pp. 36288–36295, 2002.

P. Winter, P. Leoni, and D. Abraham, “Connective tissue growth factor: structure–function relationships of a mosaic, multifunctional protein,” Growth Factors, vol. 26, no. 2, pp. 80–91, 2008.

D. R. Brigstock, C. L. Steffen, G. Y. Kim, R. K. Vegunta, J. R. Diehl, and P. A. Harding, “Purification and characterization of novel heparin- binding growth factors in uterine secretory fluids. Identification as heparin- regulated Mr10, 000 forms of connective tissue growth factor,” Journal of Biological Chemistry, vol. 272, no. 32, pp. 20275–20282, 1997.

A. M. Babic, C. C. Chen, and L. F. Lau, “Fisp12/mouse connective tissue growth factor mediates endothelial cell adhesion and migration through integrin αvβ₃, promotes endothelial cell survival, and induces angiogenesis in vivo,” Molecular and Cellular Biology, vol. 19, no. 4, pp. 2958–2966, 1999.

G. Chen, G. Grotendorst, T. Eichholtz, and N. Khalil, “GM-CSF increases airway smooth muscle cell connective tissue expression by inducing TGF-β receptors,” American Journal of Physiology Lung Cellular and Molecular Physiology, vol. 284, no. 3, pp. L548–L556, 2003.

X. Liu, F. Luo, K. Pan, W. Wu, and H. Chen, “High glucose upregulates connective tissue growth factor expression in human vascular smooth muscle cells,” BMC Cell Biol, vol. 8, no. 1, p. 1, 2007.

M. Murphy, C. Godson, S. Cannon et al., “Suppression subtractive hybridization identifies high glucose levels as a stimulus for expression of connective tissue growth factor and other genes in human mesangial cells,” Journal of Biological Chemistry, vol. 274, no. 9, pp. 5830–5834, 1999.

J. S. Park, M. K. Park, S. Y. Lee et al., “TWEAK promotes the production of interleukin-17 in rheumatoid arthritis,” Cytokine, vol. 60, no. 1, pp. 143–149, 2012.

E. Rimon, B. Chen, A. L. Shanks, D. M. Nelson, and Y. Sadovsky, “Hypoxia in human trophoblasts stimulates the expression and secretion of connective tissue growth factor,” Endocrinology, vol. 149, no. 6, pp. 2952–2958, 2008.

D. C. Rishikof, D. A. Ricupero, P. P. Kuang, H. Liu, and R. H. Goldstein, “Interleukin-4 regulates connective tissue growth factor expression in human lung fibroblasts,” Journal of Cellular Biochemistry, vol. 85, no. 3, pp. 496–504, 2002.

G. Zhou, C. Li, and L. Cai, “Advanced glycation end-products induce connective tissue growth factor-mediated renal fibrosis predominantly through transforming growth factor β-independent pathway,” The American Journal of Pathology, vol. 165, no. 6, pp. 2033–2043, 2004.

A. Leask and D. J. Abraham, “All in the CCN family: essential matricellular signaling modulators emerge from the bunker,” Journal of Cell Science, vol. 119, no. 23, pp. 4803–4810, 2006.

B. Perbal, “CCN proteins: multifunctional signalling regulators,” The Lancet, vol. 363, no. 9402, pp. 62–64, 2004.

Y. Ito, J. Aten, R. J. Bende et al., “Expression of connective tissue growth factor in human renal fibrosis,” Kidney International, vol. 53, no. 4, pp. 853–861, 1998.

H. Makino, M. Mukoyama, A. Sugawara et al., “Roles of connective tissue growth factor and prostanoids in early streptozotocin-induced diabetic rat kidney: the effect of aspirin treatment,” Clinical and Experimental Nephrology, vol. 7, no. 1, pp. 33–40, 2003.

M. Ruiz-Ortega, J. Rodriguez-Vita, E. Sanchez-Lopez, G. Carvajal, and J. Egido, “TGF-β signaling in vascular fibrosis,” Cardiovascular Research, vol. 74, no. 2, pp. 196–206, 2007.

J. Rodriguez-Vita, M. Ruiz-Ortega, M. Rupérez et al., “Endothelin-1, via ETA receptor and independently of transforming growth factor-β, increases the connective tissue growth factor in vascular smooth muscle cells,” Circulation Research, vol. 97, no. 2, pp. 125–134, 2005.

A. Leask, S. K. Parapuram, X. Shi-Wen, and D. J. Abraham, “Connective tissue growth factor (CTGF, CCN2) gene regulation: a potent clinical bio-marker of fibroproliferative disease?” Journal of Cell Communication and Signaling, vol. 3, no. 2, pp. 89–94, 2009.

H. Yokoi, M. Mukoyama, T. Nagae et al., “Reduction in connective tissue growth factor by antisense treatment ameliorates renal tubulointerstitial fibrosis,” Journal of the American Society of Nephrology, vol. 15, no. 6, pp. 1430–1440, 2004.

H. Okada, T. Kikuta, and T. Kobayashi, “Connective tissue growth factor expressed in tubular epithelium plays a pivotal role in renal fibrogenesis,” Journal of the American Society of Nephrology, vol. 16, pp. 133–143, 2005.

M. Guha, Z. G. Xu, D. Tung, L. Lanting, and R. Natarajan, “Specific down-regulation of connective tissue growth factor attenuates progression of nephropathy in mouse models of type 1 and type 2 diabetes,” The FASEB Journal, vol. 21, no. 12, pp. 3355–3368, 2007.

A. N. Panek, M. G. Posch, N. Alenina et al., “Connective tissue growth factor overexpression in cardiomyocytes promotes cardiac hypertrophy and protection against pressure overload,” PLoS One, vol. 4, no. 8, article e6743, 2009.

M. S. Ahmed, J. Gravning, V. N. Martinov et al., “Mechanisms of novel cardioprotective functions of CCN2/CTGF in myocardial ischemia-reperfusion injury,” American Journal of Physiology Heart and Circulatory Physiology, vol. 300, no. 4, pp. H1291–H1302, 2011.

H. Kinashi, L. L. Falke, T. Q. Nguyen et al., “Connective tissue growth factor regulates fibrosis-associated renal lymphangiogenesis,” Kidney International, vol. 92, no. 4, pp. 850–863, 2017.

I. Cicha, A. Yilmaz, M. Klein et al., “Connective tissue growth factor is overexpressed in complicated atherosclerotic plaques and induces mononuclear cell chemotaxis in vitro,” Arteriosclerosis, Thrombosis, and Vascular Biology, vol. 25, no. 5, pp. 1008–1013, 2005.

L. Kular, J. Pakradouni, P. Kitabgi, M. Laurent, and C. Martinerie, “The CCN family: a new class of inflammation modulators?” Biochimie, vol. 93, no. 3, pp. 377–388, 2011.

R. Rodrigues-Díez, R. R. Rodrigues-Díez, S. Rayego-Mateos et al., “The C-terminal module IV of connective tissue growth factor is a novel immune modulator of the Th17 response,” Laboratory Investigation, vol. 93, no. 7, pp. 812–824, 2013.

E. Sánchez-López, S. Rayego, R. Rodrigues-Díez et al., “CTGF promotes inflammatory cell infiltration of the renal interstitium by activating NF-κB,” Journal of the American Society of Nephrology, vol. 20, no. 7, pp. 1513–1526, 2009.

N. Toda, K. Mori, M. Kasahara et al., “Deletion of connective tissue growth factor ameliorates peritoneal fibrosis by inhibiting angiogenesis and inflammation,” Nephrology, Dialysis, Transplantation, vol. 33, no. 6, pp. 943–953, 2017.

A. Charrier, R. Chen, S. Kemper, and D. R. Brigstock, “Regulation of pancreatic inflammation by connective tissue growth factor (CTGF/CCN2),” Immunology, vol. 141, no. 4, pp. 564–576, 2014.

K. Makino, T. Makino, L. Stawski, K. E. Lipson, A. Leask, and M. Trojanowska, “Anti-connective tissue growth factor (CTGF/CCN2) monoclonal antibody attenuates skin fibrosis in mice models of systemic sclerosis,” Arthritis Research & Therapy, vol. 19, no. 1, pp. 134–185, 2017.

R. Gao and D. R. Brigstock, “Connective tissue growth factor (CCN2) induces adhesion of rat activated hepatic stellate cells by binding of its C-terminal domain to integrin αvβ3 and heparan sulfate proteoglycan,” Journal of Biological Chemistry, vol. 279, no. 10, pp. 8848–8855, 2004.

T. Nishida, T. Nakanishi, T. Shimo et al., “Demonstration of receptors specific for connective tissue growth factor on a human chondrocytic cell line (HCS-2/8),” Biochemical and Biophysical Research Communications, vol. 247, no. 3, pp. 905–909, 1998.

N. Wahab, D. Cox, A. Witherden, and R. M. Mason, “Connective tissue growth factor (CTGF) promotes activated mesangial cell survival via up-regulation of mitogen-activated protein kinase phosphatase-1 (MKP-1),” Biochemical Journal, vol. 406, no. 1, pp. 131–138, 2007.

X. Wang, S. V. McLennan, T. J. Allen, and S. M. Twigg, “Regulation of pro-inflammatory and pro-fibrotic factors by CCN2/CTGF in H9c2 cardiomyocytes,” Journal of Cell Communication and Signaling, vol. 4, no. 1, pp. 15–23, 2010.

R. R. Rodrigues-Diez, A. B. Garcia-Redondo, M. Orejudo et al., “The C-terminal module IV of connective tissue growth factor, through EGFR/Nox1 signaling, activates the NF-κB pathway and proinflammatory factors in vascular smooth muscle cells,” Antioxidants & Redox Signaling, vol. 22, no. 1, pp. 29–47, 2015.

M. A. Olayioye, R. M. Neve, H. A. Lane, and N. E. Hynes, “The ErbB signaling network: receptor heterodimerization in development and cancer,” The EMBO Journal, vol. 19, no. 13, pp. 3159–3167, 2000.

Y. Ito, T. Takeda, M. Sakon et al., “Expression and clinical significance of erb-B receptor family in hepatocellular carcinoma,” British Journal of Cancer, vol. 84, no. 10, pp. 1377–1383, 2001.

J. Liu, A. Ahiekpor, L. Li et al., “Increased expression of c-Erb B-2 in liver is associated with hepatitis B × antigen and shorter survival in patients with liver cancer,” International Journal of Cancer, vol. 125, no. 8, pp. 1894–1901, 2009.

S. K. Muthuswamy and W. J. Muller, “Activation of Src family kinases in Neu-induced mammary tumors correlates with their association with distinct sets of tyrosine phosphorylated proteins in vivo,” Oncogene, vol. 11, no. 9, pp. 1801–1810, 1995.

J. C. Wilkinson and J. V. Staros, “Effect of ErbB2 coexpression on the kinetic interactions of epidermal growth factor with its receptor in intact cells,” Biochemistry, vol. 41, no. 1, pp. 8–14, 2002.

D. Harari and Y. Yarden, “Molecular mechanisms underlying ErbB2/HER2 action in breast cancer,” Oncogene, vol. 19, no. 53, pp. 6102–6114, 2000.

Y. Yarden and M. X. Sliwkowski, “Untangling the ErbB signalling network,” Nature Reviews Molecular Cell Biology, vol. 2, no. 2, pp. 127–137, 2001.

J. M. Daly, C. B. Jannot, R. R. Beerli, D. Graus-Porta, F. G. Maurer, and N. E. Hynes, “Neu differentiation factor induces ErbB2 down-regulation and apoptosis of ErbB2-overexpressing breast tumor cells,” Cancer Research, vol. 57, no. 17, pp. 3804–3811, 1997.

S. Sundaresan, P. E. Roberts, K. L. King, M. X. Sliwkowski, and J. P. Mather, “Biological response to ErbB ligands in nontransformed cell lines correlates with a specific pattern of receptor expression,” Endocrinology, vol. 139, no. 12, pp. 4756–4764, 1998.

K. F. Lee, H. Simon, H. Chen, B. Bates, M. C. Hung, and C. Hauser, “Requirement for neuregulin receptor erbB2 in neural and cardiac development,” Nature, vol. 378, no. 6555, pp. 394–398, 1995.

D. Riethmacher, E. Sonnenberg-Riethmacher, V. Brinkmann, T. Yamaai, G. R. Lewin, and C. Birchmeier, “Severe neuropathies in mice with targeted mutations in the ErbB3 receptor,” Nature, vol. 389, no. 6652, pp. 725–730, 1997.

S. L. Erickson, K. S. O'Shea, N. Ghaboosi et al., “ErbB3 is required for normal cerebellar and cardiac development: a comparison with ErbB2-and heregulin-deficient mice,” Development, vol. 124, no. 24, pp. 4999–5011, 1997.

M. Gassmann, F. Casagranda, D. Orioli et al., “Aberrant neural and cardiac development in mice lacking the ErbB4 neuregulin receptor,” Nature, vol. 378, no. 6555, pp. 390–394, 1995.

N. Moghal and P. W. Sternberg, “Multiple positive and negative regulators of signaling by the EGF-receptor,” Current Opinion in Cell Biology, vol. 11, no. 2, pp. 190–196, 1999.

C. Liebmann, “EGF receptor activation by GPCRs: an universal pathway reveals different versions,” Molecular and Cellular Endocrinology, vol. 331, no. 2, pp. 222–231, 2011.

Y. Saito, J. Haendeler, Y. Hojo, K. Yamamoto, and B. C. Berk, “Receptor heterodimerization: essential mechanism for platelet-derived growth factor-induced epidermal growth factor receptor transactivation,” Molecular and Cellular Biology, vol. 21, no. 19, pp. 6387–6394, 2001.

F. Morgillo, J. K. Woo, E. S. Kim, W. K. Hong, and H. Y. Lee, “Heterodimerization of insulin-like growth factor receptor/epidermal growth factor receptor and induction of survivin expression counteract the antitumor action of erlotinib,” Cancer Research, vol. 66, no. 20, pp. 10100–10111, 2006.

M. Jo, D. B. Stolz, J. E. Esplen, K. Dorko, G. K. Michalopoulos, and S. C. Strom, “Cross-talk between epidermal growth factor receptor and c-Met signal pathways in transformed cells,” Journal of Biological Chemistry, vol. 275, no. 12, pp. 8806–8811, 2000.

N. El Zein, S. D'Hondt, and E. Sariban, “Crosstalks between the receptors tyrosine kinase EGFR and TrkA and the GPCR, FPR, in human monocytes are essential for receptors-mediated cell activation,” Cellular Signalling, vol. 22, no. 10, pp. 1437–1447, 2010.

V. Hugo de Almeida, G. IDS, L. R. Almendra et al., “Positive crosstalk between EGFR and the TF-PAR2 pathway mediates resistance to cisplatin and poor survival in cervical cancer,” Oncotarget, vol. 9, no. 55, pp. 30594–30609, 2018.

S. J. Allen and D. Dawbarn, “Clinical relevance of the neurotrophins and their receptors,” Clinical Science, vol. 110, no. 2, pp. 175–191, 2006.

K. J. H. Kleinwort, B. Amann, S. M. Hauck et al., “Retinopathy with central oedema in an INS C94Y transgenic pig model of long-term diabetes,” Diabetologia, vol. 60, no. 8, pp. 1541–1549, 2017.

Q. Fang, C. Zou, P. Zhong et al., “EGFR mediates hyperlipidemia-induced renal injury via regulating inflammation and oxidative stress: the detrimental role and mechanism of EGFR activation,” Oncotarget, vol. 7, no. 17, pp. 24361–24373, 2016.

K. Shimizu, Y. Taniyama, F. Sanada et al., “Hepatocyte growth factor inhibits lipopolysaccharide-induced oxidative stress via epithelial growth factor receptor degradation,” Arteriosclerosis, Thrombosis, and Vascular Biology, vol. 32, no. 11, pp. 2687–2693, 2012.

S. Huang, A. Zhang, G. Ding, and R. Chen, “Aldosteroneinduced mesangial cell proliferation is mediated by EGF receptor transactivation,” American Journal of Physiology—Renal Physiology, vol. 296, no. 6, pp. F1323–F1333, 2009.

R. A. Bradshaw, R. J. Chalkley, J. Biarc, and A. L. Burlingame, “Receptor tyrosine kinase signaling mechanisms: devolving TrkA responses with phosphoproteomics,” Advances in Biological Regulation, vol. 53, no. 1, pp. 87–96, 2013.

W. G. Richards, W. E. Sweeney, B. K. Yoder, J. E. Wilkinson, R. P. Woychik, and E. D. Avner, “Epidermal growth factor receptor activity mediates renal cyst formation in polycystic kidney disease,” The Journal of Clinical Investigation, vol. 101, no. 5, pp. 935–939, 1998.

W. E. Sweeney Jr, K. Hamahira, J. Sweeney, M. Garcia-Gatrell, P. Frost, and E. D. Avner, “Combination treatment of PKD utilizing dual inhibition of EGFreceptor activity and ligand bioavailability,” Kidney International, vol. 64, no. 4, pp. 1310–1319, 2003.

F. Terzi, M. Burtin, M. Hekmati et al., “Targeted expression of a dominant-negative EGF-R in the kidney reduces tubulo-interstitial lesions after renal injury,” The Journal of Clinical Investigation, vol. 106, no. 2, pp. 225–234, 2000.

S. Kagiyama, S. Eguchi, G. D. Frank, T. Inagami, Y. C. Zhang, and M. I. Phillips, “Angiotensin II-induced cardiac hypertrophy and hypertension are attenuated by epidermal growth factor receptor antisense,” Circulation, vol. 106, no. 8, pp. 909–912, 2002.

A. Jamroz-Wiśniewska, G. Wójcicka, E. Łowicka, M. Książek, and J. Bełtowski, “Transactivation of epidermal growth factor receptor in vascular and renal systems in rats with experimental hyperleptinemia: role in leptin-induced hypertension,” Biochemical Pharmacology, vol. 75, no. 8, pp. 1623–1638, 2008.

S. L. Merklinger, P. L. Jones, E. C. Martinez, and M. Rabinovitch, “Epidermal growth factor receptor blockade mediates smooth muscle cell apoptosis and improves survival in rats with pulmonary hypertension,” Circulation, vol. 112, no. 3, pp. 423–431, 2005.

M. Flamant, P. L. Tharaux, S. Placier et al., “Epidermal growth factor receptor trans-activation mediates the tonic and fibrogenic effects of endothelin in the aortic wall of transgenic mice,” The FASEB Journal, vol. 17, no. 2, pp. 327–329, 2003.

M. Sibilia, R. Kroismayr, B. M. Lichtenberger, A. Natarajan, M. Hecking, and M. Holcmann, “The epidermal growth factor receptor: from development to tumorigenesis,” Differentiation, vol. 75, no. 9, pp. 770–787, 2007.

G. Bronte, M. Terrasi, S. Rizzo et al., “EGFR genomic alterations in cancer: prognostic and predictive values,” Frontiers in Bioscience, vol. E3, no. 1, pp. 879–887, 2011.

J. Martinez-Useros and J. Garcia-Foncillas, “The challenge of blocking a wider family members of EGFR against head and neck squamous cell carcinomas,” Oral Oncology, vol. 51, no. 5, pp. 423–430, 2015.

J. Mendelsohn and J. Baselga, “Status of epidermal growth factor receptor antagonists in the biology and treatment of cancer,” Journal of Clinical Oncology, vol. 21, no. 14, pp. 2787–2799, 2003.

T. Kosaka, E. Yamaki, A. Mogi, and H. Kuwano, “Mechanisms of resistance to EGFR TKIs and development of a new generation of drugs in non-small-cell lung cancer,” Journal of Biomedicine & Biotechnology, vol. 2011, Article ID 165214, 7 pages, 2011.

R. S. Herbst and D. M. Shin, “Monoclonal antibodies to target epidermal growth factor receptor-positive tumors: a new paradigm for cancer therapy,” Cancer, vol. 94, no. 5, pp. 1593–1611, 2002.

J. Li, M. Zhao, P. He, M. Hidalgo, and S. D. Baker, “Differential metabolism of gefitinib and erlotinib by human cytochrome P450 enzymes,” Clinical Cancer Research, vol. 13, no. 12, pp. 3731–3737, 2007.

T. S. Mok, Y. L. Wu, S. Thongprasert et al., “Gefitinib or carboplatin-paclitaxel in pulmonary adenocarcinoma,” The New England Journal of Medicine, vol. 361, no. 10, pp. 947–957, 2009.

B. Higgins, K. Kolinsky, M. Smith et al., “Antitumor activity of erlotinib (OSI-774, Tarceva) alone or in combination in human non-small cell lung cancer tumor xenograft models,” Anti-Cancer Drugs, vol. 15, no. 5, pp. 503–512, 2004.

D. Li, L. Ambrogio, T. Shimamura et al., “BIBW2992, an irreversible EGFR/HER2 inhibitor highly effective in preclinical lung cancer models,” Oncogene, vol. 27, no. 34, pp. 4702–4711, 2008.

R. Pirker, J. R. Pereira, A. Szczesna et al., “Cetuximab plus chemotherapy in patients with advanced non-smallcell lung cancer (FLEX): an openlabel randomised phase III trial,” The Lancet, vol. 373, no. 9674, pp. 1525–1531, 2009.

D. J. Jonker, C. J. O’Callaghan, C. S. Karapetis et al., “Cetuximab for the treatment of colorectal cancer,” The New England Journal of Medicine, vol. 357, no. 20, pp. 2040–2048, 2007.

M. Prewett, M. Rothman, H. Waksal, M. Feldman, N. H. Bander, and D. J. Hicklin, “Mouse–human chimeric anti-epidermal growth factor receptor antibody C225 inhibits the growth of human renal cell carcinoma xenografts in nude mice,” Clinical Cancer Research, vol. 4, no. 12, pp. 2957–2966, 1998.

C. Limas, B. Westrum, and C. J. Limas, “The evolution of vascular changes in thespontaneously hypertensive rat,” The American Journal of Pathology, vol. 98, no. 2, pp. 357–384, 1980.

V. Griol-Charhbili, C. Fassot, S. Messaoudi, C. Perret, V. Agrapart, and F. Jaisser, “Epidermal growth factor receptor mediates the vascular dysfunction but not the remodeling induced by aldosterone/salt,” Hypertension, vol. 57, no. 2, pp. 238–244, 2011.

I. F. Benter, M. Benboubetra, A. J. Hollins, M. H. M. Yousif, H. Canatan, and S. Akhtar, “Early inhibition of EGFR signaling prevents diabetes-induced up-regulation of multiple gene pathways in the mesenteric vasculature,” Vascular Pharmacology, vol. 51, no. 4, pp. 236–245, 2009.

N. Ulu, H. Gurdal, S. W. Landheer et al., “α1-Adrenoceptor-mediated contraction of rat aorta is partly mediated via transactivation of the epidermal growth factor receptor,” British Journal of Pharmacology, vol. 161, no. 6, pp. 1301–1310, 2010.

S. Shafi, D. Lamb, H. Modjtahedi, and G. Ferns, “Periadventitial delivery of anti-EGF receptor antibody inhibits neointimal macrophage accumulation after angioplasty in a hypercholesterolaemic rabbit,” International Journal of Experimental Pathology, vol. 91, no. 3, pp. 224–234, 2010.

P. Gao, X. M. Wang, D. H. Qian et al., “Induction of oxidative stress by oxidized LDL via meprinα-activated epidermal growth factor receptor in macrophages,” Cardiovascular Research, vol. 97, no. 3, pp. 533–543, 2013.

B. Stanic, D. Pandey, D. J. Fulton, and F. J. Miller Jr., “Increased epidermal growth factor-like ligands are associated with elevated vascular nicotinamide adenine dinucleotide phosphate oxidase in a primate model of atherosclerosis,” Arteriosclerosis, Thrombosis, and Vascular Biology, vol. 32, no. 10, pp. 2452–2460, 2012.

A. Templeton, M. Braendle, T. Cerny, and S. Gillessen, “Remission of diabetes while on sunitinib treatment for renal cell carcinoma,” Annals of Oncology, vol. 19, no. 4, pp. 824-825, 2008.

D. B. Costa and M. S. Huberman, “Improvement of type 2 diabetes in a lung cancer patient treated with erlotinib,” Diabetes Care, vol. 29, no. 7, p. 1711, 2006.

D. Veneri, M. Franchini, and E. Bonora, “Imatinib and regression of type 2 diabetes,” The New England Journal of Medicine, vol. 352, no. 10, pp. 1049-1050, 2005.