Mechanisms of DNA methyltransferase-inhibitor interactions: Procyanidin B2 shows new promise for therapeutic intervention of cancer.

DNA methyltransferases (DNMTs) is a key epigenetic enzyme for pharmacological manipulation and is employed in cancer reprogramming. During past few years multiple strategies have been implemented to excavate epigenetic compounds targeting DNMTs. In light of the emerging concept of chemoinformatics, molecular docking and simulation studies have been employed to accelerate the development of DNMT inhibitors. Among the DNMT inhibitors known till date, epigallocathechin-3-gallate (EGCG) was identified to be effective in reducing DNMT activity. However, the broad spectrum of EGCG to other diseases and variable target enzymes offers some limitations. In view of this, 32 EGCG analogues were screened at S-Adnosyl-L-homocysteine (SAH) binding pocket of DNMTs and procyanidin B2-3, 3'-di-O-gallate (procyanidin B2) was obtained as potent inhibitor having medicinally relevant chemical space. Further, in vitro analysis demonstrates the efficiency of procyanidin B2 in attenuating DNMT activity at IC50 of 6.88±0.647 µM and subsequently enhancing the expression of DNMT target genes, E-cadherin, Maspin and BRCA1. Moreover, the toxic property of procyanidin B2 towards triple negative breast cancer cells to normal cells offers platform for pre-clinical trial and an insight to the treatment of cancer.

Expression profiling of DNA methylation-mediated epigenetic gene-silencing factors in breast cancer.

BACKGROUND: DNA methylation mediates gene silencing primarily by inducing repressive chromatin architecture via a common theme of interaction involving methyl-CpG binding (MBD) proteins, histone modifying enzymes and chromatin remodelling complexes. Hence, targeted inhibition of MBD protein function is now considered a potential therapeutic alternative for thwarting DNA hypermethylation prompted neoplastic progress. We have analyzed the gene and protein expression level of the principal factors responsible for gene silencing, that is, DNMT and MBD proteins in MCF-7 and MDA-MB-231 breast cancer cell lines after treatment with various epigenetic drugs. RESULTS: Our study reveals that the epigenetic modulators affect the expression levels at both transcript and protein levels as well as encourage growth arrest and apoptosis in MCF-7 and MDA-MB-231 cells. AZA, TSA, SFN, and SAM inhibit cell growth in MCF-7 and MDA-MB-231 cell lines in a dose-dependent manner, that is, with increasing concentrations of drugs the cell viability gradually decreases. All the epigenetic modulators promote apoptotic cell death, as is evident form increased chromatin condensation which is a distinct characteristic of apoptotic cells. From FACS analysis, it is also clear that these drugs induce G2-M arrest and apoptosis in breast cancer cells. Further, transcript and protein level expression of MBDs and DNMTs is also affected - after treatment with epigenetic drugs; the level of transcripts/mRNA of MBDs and DNMTs has consistently increased in general. The increase in level of gene expression is substantiated at the protein level also where treated cells show higher expression of DNMT1, DNMT3A, DNMT3B, and MBD proteins in comparison to untreated cells. In case of tissue samples, the expression of different DNMTs is tissue stage-specific. DNMT1 exhibits significantly higher expression in the metastatic stage, whereas, DNMT3A and DNMT3B have higher expression in the primary stage in comparison to the metastatic samples. CONCLUSION: The epigenetic modulators AZA, TSA, SFN, and SAM may provide opportunities for cancer prevention by regulating the components of epigenetic gene-silencing machinery especially DNMTs and MBDs.

Epigenetic choreography of stem cells: the DNA demethylation episode of development.

Reversible DNA methylation is a fundamental epigenetic manipulator of the genomic information in eukaryotes. DNA demethylation plays a very significant role during embryonic development and stands out for its contribution in molecular reconfiguration during cellular differentiation for determining stem cell fate. DNA demethylation arbitrated extensive make-over of the genome via reprogramming in the early embryo results in stem cell plasticity followed by commitment to the principal cell lineages. This article attempts to highlight the sequential phases and hierarchical mode of DNA demethylation events during enactment of the molecular strategy for developmental transition. A comprehensive knowledge regarding the pattern of DNA demethylation during embryogenesis and organogenesis and study of the related lacunae will offer exciting avenues for future biomedical research and stem cell-based regenerative therapy.