Even though most of these epigenetic drugs are still in early development and the prospects for them to be used clinically for cancer treatment remain to be evaluated, that evaluation will depend on our understanding of how they work and what outcomes might be expected. 5-Aza-dC and TSA are viewed as potent and specific inhibitors for methylation and histone deacetylation, respectively, and they have been widely used for investigating epigenetic alteration of many tumor suppressor genes. These inhibitors usually cause global changes in gene expression by remodeling chromatin via directly MEDChem Express 183204-72-0 converting methylated DNA to unmethylated DNA or unacetylated histones to the acetylated state, thereby allowing easy access of the transcription machinery to gene promoters. However, some inhibitors might be doing more, and their anti-cancer properties could be much more complicated. For instance, many non-histone cellular proteins such as transcription factors are also substrates of HDAC, and their transcriptional activities could be affected by the HDAC inhibitor TSA as well. Most tumor suppressor genes are epigenetically silenced by either DNA methylation and/or histone deacetylation in their promoters. To our knowledge, there is no report showing that the expression of such genes can be differentially regulated by inhibitors of methylation or histone deacetylation in a cancerspecific fashion without having epigenetic modifications in the promoter. The regulation of MIG-6 by these inhibitors, as we show here, unveils a novel mechanism by which a tumor suppressor gene can be epigenetically silenced in an indirect and tissuespecific 1187431-43-1 manner. Our luciferase reporter assay results indicated that the regulation of MIG-6 expression in melanoma and in lung cancer was most likely mediated by different factors. We have identified a minimal TSA response element in exon 1 of MIG-6 proximal to its promoter, while location of the 5- aza-dC response element is still uncertain. We speculate that the TSA response element in the MIG-6 gene is most likely regulated by a factor whose expression is affected by histone deacetylation in its promoter or whose protein activity is directly regulated by acetylation/deacetylation. This factor would be activated in l
