Association of the Interleukin-10-592C/A Polymorphism and Cervical Cancer Risk: A Meta-Analysis

A literature review showed some discrepancies regarding the association of -592C/A with the risk of cervical cancer. To allow more precise analysis of the data by increasing the number of cases studied and more acceptable generalization by considering results from different sources, the present meta-analysis was performed on available published studies that explored the relationship between SNP-592C/A of the IL-10 gene and the risk of cervical cancer. Eleven available studies, including 4187 cases and 3311 controls, were included in this study investigating the relationship between the -592C/A polymorphism of IL-10 and cervical cancer risk. Fixed-effects or random-effects models were performed with pooled odds ratios (ORs). Heterogeneity and bias tests were performed by the inconsistency test and funnel plot, respectively. The overall analysis showed an increased susceptibility to cervical cancer with the -592C/A polymorphism of the IL-10 gene for the recessive model (OR = 1.30, 95% CI = 1.14–1.49), dominant model (OR = 1.36, 95% CI = 1.09–1.70), and additive model (OR = 1.25, 95% CI = 1.09–1.44). Regarding ethnicity, a significant association of the -592C/A polymorphism of the IL-10 gene was linked to an elevated risk of cervical cancer for all genetic models (recessive, dominant, and additive) in the Asian populations and for the recessive and additive models in Caucasians with P < 0.05. The -592C/A polymorphism of the IL-10 gene may be considered a risk factor for cervical cancer.


Introduction
Cervical cancer is the fourth most common cancer in the world, accounting for 6.5% of all cancers, after breast, colorectal, and lung cancer. It is also the fourth highest cause of cancer death in women in both high-income and low-middleincome countries, with an estimated mortality rate of 7.7% worldwide (GLOBOCAN 2020) [1]. Exposure to high-risk human papillomavirus (HPV) is required but is not a sufficient cause of cervical cancer [2,3]. Oncogenic HPV DNA is present in nearly 100% of invasive cervical cancers. A limited immune response to HPV linked to the host's genetic make-up may increase the risk of cervical cancer [4]. Many authors have been interested in the research of risk factors related to cervical cancer throughout the last few decades [5]. It appears from their investigations that genetic factors seem to exert a significant influence on the carcinogenesis of the cervix. Notably, the reported results are conflicting. However, mutations in genes involved in cytokine synthesis, such as interleukin 10 (IL-10), appear to be strong predictors of cervical cancer risk [6][7][8]. Physiologically, IL-10 is an essential cytokine for inflammatory modulation. Several cell types are involved in the production of this cytokine, including 1, 2, 17 lymphocytes, B lymphocytes, mast cells, eosinophils, monocytes, macrophages, and dendritic cells [9,10].
e IL-10 gene, which contains five exons, has been found on the long arm of chromosome 1q31-32 in humans [11,12]. e significance of the IL-10 gene in the control of immune-mediated illness responses has resulted in the discovery of numerous polymorphisms in different portions of the gene, including the promoter region [4,11]. e majority of identified genetic polymorphisms are single nucleotide polymorphisms (SNPs). e SNP-592C/A of the IL-10 gene promoter is located near a number of transcription factor binding sites. is SNP has been implicated in the pathogenesis of cutaneous malignant melanoma and prostate, breast, gastric, and cervical cancer [6,[13][14][15][16][17][18]. Association studies carried out in different populations have shown that this SNP increases the risk of developing cervical cancer [6,17,19]. However, other studies have reported conflicting results [7,20,21]. Furthermore, the expression of the IL-10 gene and/or the production of IL-10 has been demonstrated in various types of tumors, suggesting that IL-10 could, by promoting escape from the immune system, constitute a step in tumorigenesis [22][23][24]. Given the contradictory results of numerous studies on the role of SNP-592C/ A of the IL-10 gene in the pathogenesis of cervical cancer, we conducted a meta-analysis to assess the association between SNP-592C/A in the IL-10 gene and the risk of cervical cancer.

Literature Search Strategy.
e identification of initial manuscripts or published articles, available in English, was performed using the online databases PubMed, the Harvard University Library, Web of Science, and Genetics Medical Literature Database. Additional articles were identified from references cited in relevant reports and journals. e key search words "Interleukin-10" or "IL-10," "−592C/A" or "−592C > A" or "rs1800872," "polymorphism" or "variant" or "mutation" or "gene" or "cervical tumor" or "cervical cancer" were used to locate and select the articles.

Inclusion Criteria.
e eligibility criteria were as follows: (1) case-control study design evaluating the association of the -592C/A polymorphisms of the IL-10 gene with the risk of cervical cancer, (2) availability of the full scientific manuscript, (3) distribution of polymorphisms in the controls in agreement with Hardy-Weinberg equilibrium (HWE), (4) availability of proportions of the different genotypes (CC, CA, AA for −592C/A of the IL-10 gene) in both cases and controls, and (5) no significant change in the value of the odds ratio (OR).

Data Extraction.
ree authors independently carried out the literature search to optimize the convergence of the retrieved data, including principal author, year of publication, study design, study population, racial and ethnic groups, sample size, genotypic and allelic proportions in cases and controls, HWE calculation, and genetic models tested.

Statistical Analysis.
e statistical analyses were conducted using Review Manager v5.3 and MedCalc v14.8.1. e distribution of the −592C/A polymorphism of the IL-10 gene in agreement with HWE in the controls was evaluated by a chi-square test, with P < 0.05. A pooled OR test with a 95% confidence interval (CI) was used to assess the strength of the association between the −592C/A polymorphism in the IL-10 gene and the risk of cervical cancer, including the recessive model (AA vs. CC + CA), the dominant model (AA + CA vs. CC), and the additive model (A vs. C). To avoid type I error, the level of significance was corrected using Bonferroni's adjustment during multiple comparisons. An inconsistency (I 2 ) statistical test was used to determine heterogeneity [25,26]. If there was no heterogeneity (I 2 < 50%), a fixed-effect model (FEM) was retained for interpretation of a global OR. In the case of heterogeneity, the OR was interpreted using a random-effect model (REM). A funnel plot was used to determine bias [27]. e trial sequential analysis (TSA) software was used to estimate the sample size required for each arm to assess the robustness of the meta-analysis findings with 90% statistical power [28].

Quantitative Analysis.
Based on analysis by race/ethnicity (Table 2), the -592C/ A polymorphism of the IL-10 gene was significantly associated with an increased risk of cervical cancer in Caucasians for the recessive model (OR (FEM) � 1.50, 95%    CI � 1.08-1.30, P � 0.0002) models ( Figure 4). After Bonferroni correction adjusts P value, a nonsignificant association was found between IL-10 -592C/A polymorphism and cancer for the dominant model in Caucasians.

Sensitivity Analysis.
e stability of the meta-analysis was maintained by removing studies that significantly changed the overall OR and P value after excluding those that deviated from HWE [8]. In this regard, only the article by Singhal et al. has been omitted [19].

Heterogeneity Source.
We found heterogeneity for the dominant and additive models with I 2 > 50 and I 2 � 66 percent, respectively, when we excluded studies that deviated from HWE and the ones that significantly affected the cumulative OR value (Figures 2(b) and 2(c)). e genetic models showed no heterogeneity in the race/ethnicity study, except for the dominating pattern in Caucasians (I 2 � 84 percent, P � 0.0003) (Figure 3(b)).

Publication Bias.
e evaluation of publication bias was conducted by performing funnel plots. An absence of publication bias was observed for the recessive, dominant, and additive models after removing studies, not in agreement with the HWE and the study modifying the value of the pooled OR ( Figure 5).

Results of TSA
e TSA's outcome is depicted in Figure 6. e conclusions of the present meta-analysis are strong because the required sample size is 3669 and the cumulative z-curve reached the requested sample size by crossing the upper limit of sequential trial monitoring.

Discussion
HPV infection is one of the leading causes of cervical cancer, yet it is not sufficient to trigger cervical carcinogenesis.  contraceptives have all been identified as additional risk factors. Although genetic variables have been linked to carcinogenesis, the mechanism by which the IL-10 gene polymorphism causes cervical cancer is unknown. In vitro, IL-10 has been shown to have powerful immunosuppressive and antiinflammatory activities [35][36][37]. is cytokine is produced by a variety of cell types, such as CD4 T cells and monocytes/macrophages [38,39]. Macrophages' ability to present antigens to T cells, as well as their ability to provide a costimulatory signal to T cells, is reduced by IL-10. It performs this function by inhibiting the activation of class II MHC-11 molecules and specific accessory molecules on their surfaces, including the B7.1 molecule [40]. By blocking cell-mediated immune responses and inflammatory reactions, IL-10 can promote carcinogenesis by limiting the development of an adequate antitumor response against tumor cells [40,41].
It is worth noting that, in addition to its inhibitory characteristics, IL-10 stimulates antibody production, as well as the differentiation and proliferation of B lymphocytes, which in turn produce IL-10 [42][43][44]. Furthermore, the expression of the IL-10 gene has been confirmed in various tumors, suggesting that IL-10 could play a nonnegligible role in carcinogenesis by allowing the immune system to escape [4]. In promoter regions, functional polymorphisms of the IL-10 gene such as -592C/ A can lead to changes in the affinity of transcriptional factors, thereby altering levels of mRNA expression (dose-  6 Genetics Research dependent effect) of inflammatory cytokines associated with the occurrence of cancer [22,45].
In the present study, including 4187 cases and 3311 controls, we noted that the −592C/A polymorphism of the IL-10 gene was correlated with the overall risk of cervical cancer for the recessive, dominant, and additive models. is finding is in line with a previous meta-analysis that identified a significant association between the −592C/A polymorphism and an increased risk of cervical cancer in 2396 cases and 1388 controls [46]. Contrary to our results, Guo et al. reported in a meta-analysis of 3,149 cases and 2,237 controls that the −592C/A polymorphism was not globally correlated with cervical cancer for the three genetic models [14]. A recent meta-analysis with 1,393 cases and 1,307 controls also found conflicting results [47]. In Caucasians and Asians, our meta-analysis adjusted for race and ethnicity found an association between the −592C/A polymorphism and cervical cancer in all models. Some meta-analyses supported our conclusions in some respects. is was the case in the metaanalysis by Guo et al. on the Caucasian population, which found that only the recessive model was associated with an increased risk of cervical cancer [14], and another metaanalysis from the Asian population, which found that the additive model was associated with the risk of cervical cancer [46]. However, Wang et al. found that the −592C/A polymorphism had no effect on the risk of cervical cancer in Caucasian and Asian populations across all genetic models tested [47].  [6,7,30]. ese discrepancies between studies can be explained by a few factors, including (1) sample size differences between studies, (2) inclusion of studies with allele frequencies that deviate from the HWE, (3) inclusion of studies that change the pooled OR value, (4) population genetic background, and (5) inclusion of studies based on noncancerous cervical lesions [8,19,48]. e present study shows certain limitations as follows: the limited number of case and control studies carried out on the association of SNP-592C/A in the IL-10 gene with the Although the sample size requirement showed statistical power of 90%, a more representative sample size from different populations worldwide could confirm or refute a robust conclusion.

Conclusions
Based on an analysis of a large sample with precise inclusion criteria, this study reveals that women with the −529C/A polymorphism of the IL-10 gene promoter have a high risk of cervical cancer for genetic models and provides evidence of an association of the IL-10 gene promoter in the pathogenesis of cervical cancer.

Disclosure
is manuscript was presented as a preprint in "Association of Interleukin-10 −592C/A Polymorphism and Cervical Cancer Risk: A Meta-Analysis" (Preprint) [49] Abbreviations AA vs. Hardy-Weinberg equilibrium I 2 : Inconsistency IL-10: Interleukin-10 N: Number OR: Odds ratio RE: Random effect vs: Versus.
Data Availability e supplementary material represents all the data analyzed in this meta-analysis.

Conflicts of Interest
e authors declare that there are no conflicts of interest regarding the publication of this paper.

Authors' Contributions
e final manuscript has been read and approved by all authors. Study conceptualization and design were done by BD, YK, MM, and LH. View, collection, analysis, and interpretation of the meta-analysis data were performed by BD, YK, MM, GD, OK, JLH, and LH. BD drafted of the