Journal of Thyroid Research
Volume 2015 (2015), Article ID 540183, 2 pages
http://dx.doi.org/10.1155/2015/540183

Letter to the Editor

Tumor Growth Mitigating Effects of Valproic Acid in Systemic Malignancies

Shailendra Kapoor

Private Practice, Richmond, VA 23114, USA

Received 11 May 2015; Accepted 18 May 2015

Academic Editor: Thomas J. Fahey

Copyright © 2015 Shailendra Kapoor. 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.

Recent data suggests that valproic acid (VPCA) also attenuates and limits tumor growth in a number of systemic malignancies [1].

For instance, VPCA has a suppressive effect on tumor growth in renal malignancies. Oertl et al. have recently shown that VPCA mediates this role in part by altering the expression of beta1 integrins in tumor cells [2]. VPCA also mediates this role in part by upregulating BAX expression. These changes have recently been confirmed in Caki-1 and KTC-26 cell lines. In addition, VPCA accentuates the expression of ULBP1 and ULBP2. Jones et al. have recently demonstrated that, at the same time, VPCA accentuates p21 expression [3]. Recent data also suggests that IFN-alpha accentuates the cytotoxic effects of VPCA. Cyclin B and cyclin D3 levels are also modulated by VPCA [4]. Yang et al. have recently demonstrated that VPCA also accentuates the cytotoxicity of NK cells against renal cancer cells [5]. In addition, VPCA also affects tumor cell adhesiveness thereby further attenuating tumor expansion in renal carcinomas [6].

Similarly, VPCA has an inhibitory effect on tumor growth in gastric malignancies. VPCA has a positive impact on acetyl-α-tubulin levels. It also mediates this role in part by attenuating c-Myc expression. Bcl-2 expression is downregulated concurrently. As a result, tumor cell apoptosis is markedly augmented. Zhao et al. have recently demonstrated that this is accompanied by accentuation of p21 (Waf/cip1) expression [7]. These changes have recently been confirmed in BGC-823, OCUM-2MD3, HGC-27, and SGC-7901 cell lines. In addition, VPCA has a negative impact on cyclin A as well as cyclin D1 expression. At the same time, tumor cell proliferation is markedly attenuated [8]. This is accompanied by accentuation of acetyl-histone H3 levels. G1 phase arrest is typically seen. In addition, Yagi et al. have recently demonstrated that survivin expression is significantly downregulated [9]. Mad1 expression is upregulated concurrently. p27 expression is also accentuated simultaneously. Besides the above-mentioned changes, VPCA also augments and enhances caspase 9 and caspase 3 activation thereby further abrogating tumor growth in gastric carcinomas.

As is obvious from the above discussion, VPCA exhibits potent tumor growth mitigating effects. Hopefully, the coming few years will see an increase in the utilization of VPCA as an antineoplastic agent.

Conflict of Interests

The author declares that there is no conflict of interests regarding the publication of this paper.

References

V. Haghpanah, M. Malehmir, B. Larijani et al., “The beneficial effects of valproic acid in thyroid cancer are mediated through promoting redifferentiation and reducing stemness level: an in vitro study,” Journal of Thyroid Research, vol. 2014, Article ID 218763, 9 pages, 2014.

A. Oertl, B. Relja, J. Makarevic et al., “Altered expression of β1 integrins in renal carcinoma cell lines exposed to the differentiation inducer valproic acid,” International Journal of Molecular Medicine, vol. 18, no. 2, pp. 347–354, 2006.

J. Jones, E. Juengel, A. Mickuckyte et al., “Valproic acid blocks adhesion of renal cell carcinoma cells to endothelium and extracellular matrix,” Journal of Cellular and Molecular Medicine, vol. 13, no. 8, pp. 2342–2352, 2009.

E. Juengel, M. Bhasin, T. Libermann et al., “Alterations of the gene expression profile in renal cell carcinoma after treatment with the histone deacetylase-inhibitor valproic acid and interferon-alpha,” World Journal of Urology, vol. 29, no. 6, pp. 779–786, 2011.

F. Yang, Y. Shao, F. Yang et al., “Valproic acid upregulates NKG2D ligand expression and enhances susceptibility of human renal carcinoma cells to NK cell-mediated cytotoxicity,” Archives of Medical Science, vol. 9, no. 2, pp. 323–331, 2013.

E. Juengel, J. Makarević, I. Tsaur et al., “Resistance after chronic application of the HDAC-inhibitor valproic acid is associated with elevated Akt activation in renal cell carcinoma in vivo,” PLoS ONE, vol. 8, no. 1, Article ID e53100, 2013.

X. Zhao, W. Yang, C. Shi et al., “The G1 phase arrest and apoptosis by intrinsic pathway induced by valproic acid inhibit proliferation of BGC-823 gastric carcinoma cells,” Tumor Biology, vol. 32, no. 2, pp. 335–346, 2011.

E. Juengel, J. Engler, A. Mickuckyte et al., “Effects of combined valproic acid and the epidermal growth factor/vascular endothelial growth factor receptor tyrosine kinase inhibitor AEE788 on renal cell carcinoma cell lines in vitro,” BJU International, vol. 105, no. 4, pp. 549–557, 2010.

Y. Yagi, S. Fushida, S. Harada et al., “Effects of valproic acid on the cell cycle and apoptosis through acetylation of histone and tubulin in a scirrhous gastric cancer cell line,” Journal of Experimental and Clinical Cancer Research, vol. 29, article 149, 2010.