Role of DNA demethylation in cancer

There is an overwhelming amount of evidence that show that DNA methylation patterns are altered in cancer. In a normal cell, methylation of CpG-rich islands in regulatory regions of genes which confer selective advantage upon cancer cells such as tumor suppressors, adhesion molecules, inhibitors of angiogenesis and repair enzymes results in their transcriptional silencing. In parallel, these genes are globally less methylated in the tumor cell genomes normal counterparts. As compared to regional hypermethylation, the global hypomethylation in cancer cells occurs in sparsely distributed CpG sequences, thus making DNA methylation an important contributor in setting gene expression programs during development. Evidence from research suggests that changes in DNA methylation patterns are involved in human disease through altering normal gene expression programming. With respect to genetic changes aberrant DNA methylation patterns are potentially reversible raising the hope for DNA methylation based therapeutics. This reversal of DNA methylation patterns is accomplished mainly by passive mechanisms which include covalent trapping of DNMTs by cytosine base analogues. Removal of methyl layer could also be occurred by excision of the 5-methyl cytosine base by DNA glycosylase. However, the importance of truly chemically defined direct demethylation on intact DNA is mainly in the regulation of gene expression, development and cell growth, hence it becomes necessary to know the exact biochemical mechanism and the enzymes involved in it. The present study has been carried out keeping this in mind with an objective to study the role of demethylation in cancer and investigate certain candidate genes such as methyl-binding proteins MBD2 and MBD4 for putative demethylase activity

Investigation of the Epigenetic Regulators and Signaling Pathways influencing Pluripotency Inducing Transcription Factors mediated Tumorigenesis

Pluripotency inducing transcription factors (TFs) Oct4,Sox2 and Nanog under the influence of epigenetic modifications (especially,DNA methylation and histone H3 modifications) and signaling pathways work stringently to guard stem cell pluripotency and smoothly manoeuvre transition between differential gene expression states during both normal and pathological conditions.The present work is undertaken to investigate the influence of epigenetic regulators and signaling pathways on pluripotency inducing TFs during tumorigenesis.The expression profile of Oct4,Sox2 and Nanog in breast and prostate cancer along with epigenetic regulatory enzymes(DNA methyltransferases(DNMTs),histone methyltransferases(HMTs)and histone deacetylases(HDACs) predominantly active in controlling the expression of these TFs are studied.Furthermore,hedgehog(HH)signaling pathway mediated regulation of Oct4,Sox2 and Nanog is also examined.Oct4,Sox2 and Nanog are over-expressed both at transcript(mRNA)and protein level in a stage-specific manner in both cancers.The over-expression of Oct4,Sox2 and Nanog is associated with enhanced tumorigenic potential as is evident from reduction in cell proliferation,decrease in cell migration and invasive potential,cell cycle arrest at G1 phase and increase in apoptotic population upon silencing of these factors via si-RNA.Upon investigating the epigenetic regulatory mechanism controlling their over-expression,it was found that active histone modifications H3K4me3 and H3K9AcS10p in promoters of Oct4 and Sox2 predominantly up-regulate expression of these genes in both cancers whereas promoter DNA methylation is not effective.Alongside these marks,it is also seen that HH-Sox2 axis is active in prostate cancer and mediates androgen independent prostate cancer.As researchers and oncologists are struggling to find a successful treatment approach for metastatically aggressive malignancies,unravelling the epigenetic machinery and allied signaling pathways controlling transcriptional network of a cancer cell will be one step forward in this endeavour

Synthesis of novel spirobibenzopyrans as potent anticancer leads inducing apoptosis in HeLa cells

Spirobibenzopyrans are an unexplored class of therapeutics. We report the anticancer activity of novel spirobibenzopyrans, synthesized by a one-pot reaction and extensively characterized. Structure of one of the spirobibenzopyran has been determined by the single crystal XRD technique. The in vitro anticancer activity of these derivatives across the NCI 60-cell line panel was evaluated and for the first time their mechanism of action against HeLa cells was probed via cell morphology analysis and cell cycle analysis. They were determined to be apoptosis inducers with cell cycle arrest in G(0)/G(1) and S phase suggesting CDK-4 protein inhibition and the inhibition of DNA replication. The DNA inhibition was studied and confirmed using the alkaline comet assay for the compound CHX-4MO-SAL showing S phase inhibition. Further, conformity with the in silico Lipinski's score signify the potential of spirobibenzopyrans as anticancer leads

Diarylidene-N-Methyl-4-Piperidone and Spirobibenzopyran Curcumin Analogues as Antioxidant and Anti-Inflammatory Pharmacophores

There is a significant need for new small molecule anti-inflammatory compounds. Curcumin, a small molecule natural product from the Turmeric (Curcuma longa) plant, has well-known anti-oxidant properties, resulting from its radical scavenging ability and inhibition of inflammation-associated factors. However, its lack of solubility, instability, and poor bioavailability and biodistribution characteristics are an impediment to its use. To circumvent these issues while retaining curcumin’s biological activity, we synthesized twenty-one diarylidene-N-methyl-4-piperidones (DANMPs), four diheteroarylidene-N-methyl-4-piperidones (DHANMPs), and five spirobibenzopyran (SBP) derivatives. All were screened in terms of anti-oxidant activity via a cell-free 2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay and for drug-like properties in silico. In the former, some compounds possessed improved radical scavenging behavior versus ascorbic acid, which was used as a benchmark. Conformity to simulated Lipinski’s parameters and Absorption, Distribution, Metabolism, and Excretion (ADME) studies indicated the DANMPs, DHANMPs, and SBPs to be potentially useful compounds. A subset of molecules was investigated in terms of their aqueous solubilities, which were significantly improved compared to that of curcumin. In vitro assessments of the cellular and anti-inflammatory effects of these compounds were conducted using RAW264.7 macrophages. RT-PCR and Griess assays were used to evaluate the presence of inflammatory/activated (M1) markers and production of nitric oxide (NO) species, which are associated with inflammation, respectively. While the compounds did not affect non-stimulated (naïve) macrophages, they did reduce levels of markers and NO to extents similar to or better than curcumin in inflamed cells. Our results indicate that these pharmacophores possess anti-inflammatory properties and can be used as curcumin-substitutes with improved characteristics. Further investigation into their mechanisms of action and potential use in the treatment of inflammatory diseases is merited

Epigenetic silencing of genes enhanced by collective role of reactive oxygen species and MAPK signaling downstream ERK/Snail axis: Ectopic application of hydrogen peroxide repress CDH1 gene by enhanced DNA methyltransferase activity in human breast cancer

Loss of E-cadherin and epithelial to mesenchymal transition (EMT) are key steps in cancer progression. Reactive oxygen species (ROS) play significant roles in cellular physiology and homeostasis. Roles of E-cadherin (CDH1), EMT and ROS are intriguingly illustrated in many cancers without focusing their collective concert during cancer progression. We report that hydrogen peroxide (H2O2) treatment modulate CDH1 gene expression by epigenetic modification(s). Sublethal dosage of H2O2 treatment decrease E-cadherin, increase DNMT1, HDAC1, Snail, Slug and enrich H3K9me3 and H3K27me3 in the CDH1 promoter. The effect of H2O2 was attenuated by ROS scavengers; NAC, lupeol and beta-sitosterol. DNMT inhibitor, AZA prevented the H2O2 induced promoter-CpG-island methylation of CDH1. Treatment of cells with U0126 (inhibitor of ERK) reduced the expression of DNMT1, Snail and Slug, increased CDHL This implicates that CDH1 is synergistically repressed by histone methylation, DNA methylation and histone deacetylation mediated chromatin remodelling and activation of Snail and Slug through ERK pathway. Increased ROS leads to activation of epigenetic machineries and EMT activators Snail/Slug which in their course of action inactivates CDH1 gene and lack of E-cadherin protein promotes EMT in breast cancer cells. ROS and ERK signaling facilitate epigenetic silencing and support the fact that subtle increase of ROS above basal level act as key cell signaling molecules. Free radical scavengers, lupeol and beta-sitosterol may be tested for therapeutic intervention of breast cancer. This work broadens the amplitude of epigenome and open avenues for investigations on conjoint effects of canonical and intrinsic metabolite signaling and epigenetic modulations in cancer