Tified as one of the principal factors supporting cancer development, demethylation agents have now become the main focus of molecular-targeted therapeutics. Various in vitro studies have shown that 5azacytidine (5-AZA), a potent DNA methyl transferase inhibitor (DNMTi), leads to re-expression of silenced?2016 Sajadian et al. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.Sajadian et al. Clinical Epigenetics (2016) 8:Page 2 ofgenes and altered expression of genes involved in tumor suppression [7]. However, a very few studies have been published to understand the mode of action of 5-AZA. Recently, our lab clearly demonstrated that 5-AZA modulates the expression of genes through induction of TET2 and TET3, improving 5hmC generation in HCC and inhibiting cells proliferation [8]. All TET proteins contain a catalytic domain which binds to Fe2+ and 2-oxoglutarate to mediate oxidation of 5mC to 5hmC in DNA [4]. Vitamin C plays a buy Chloroquine (diphosphate) central role in the conversion of 5mC to 5hmC by enhancing the catalytic activity of TET dioxygenases [9, 10]. In addition, recent reports point to the important role of vitamin C in modulating mesenchymal-epithelial transition (MET) by regulating TET1 [11] and also in inducing cell death via epigenetic modification in melanoma cells [12]. Therefore, vitamin C might be an important factor in reducing the risk of promoter hypermethylation supporting the maintenance of the 5hmC state and PubMed ID:https://www.ncbi.nlm.nih.gov/pubmed/29072704 thus might play a major role in the epigenetic regulation [9, 11, 13, 14]. Transition from epithelial to mesenchymal (EMT) state is partially mediated by Snail expression, which is considered as a hallmark of cancer progression [15?7]. Transient Snail expression suppresses the epithelial marker E-cadherin whose downregulation is directly associated with tumor invasion and metastasis in HCC [18?0]. In addition to the control of EMT, Snail as a major transcriptional repressor is also involved in the regulation of cell cycle progression and in conferring resistance to programmed cell death [21]. Several reports have shown that 5-AZA induces cell cycle arrest and cell death in tumor cells [22, 23] by altering the epigenetic state, but the details of 5-AZA-induced cell cycle arrest in HCC are not completely understood. Accumulating evidences also point to the significance of epigenetics in regulating EMT in cancer [reviewed in [24]]. A recent report shows MET in trophoblast cells by induction of epithelial markers when treated with a 5AZA analog [25]. However, the effect of 5-AZA on Snail expression and the downstream pathways is not yet known. Hence, we have probed into the changes in gene expression of Snail which could possibly link EMT/MET and cell cycle arrest mediated by 5-AZA. Furthermore, we have also questioned if vitamin C as an epigenetic modifier could enhance the effect of 5-AZA in inducing cell death which probably could be explored as a possible combination therapy in HCC. Our results have shown tha.
