title: Expression profiling of DNA methylation-mediated epigenetic gene-silencing factors in breast cancer.
abstract: 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Epigenetics and Cancer Research Laboratory, Biochemistry and Molecular Biology Group, Department of Life Science, National Institute of Technology, Rourkela, Odisha 769008, India.
authors.forename: Swayamsiddha
authors.initials: S
authors.lastname: Kar
authors.affiliation: Epigenetics and Cancer Research Laboratory, Biochemistry and Molecular Biology Group, Department of Life Science, National Institute of Technology, Rourkela, Odisha 769008, India.
authors.forename: Dipta
authors.initials: D
authors.lastname: Sengupta
authors.affiliation: Epigenetics and Cancer Research Laboratory, Biochemistry and Molecular Biology Group, Department of Life Science, National Institute of Technology, Rourkela, Odisha 769008, India.
authors.forename: Moonmoon
authors.initials: M
authors.lastname: Deb
authors.affiliation: Epigenetics and Cancer Research Laboratory, Biochemistry and Molecular Biology Group, Department of Life Science, National Institute of Technology, Rourkela, Odisha 769008, India.
authors.forename: Arunima
authors.initials: A
authors.lastname: Shilpi
authors.affiliation: Epigenetics and Cancer Research Laboratory, Biochemistry and Molecular Biology Group, Department of Life Science, National Institute of Technology, Rourkela, Odisha 769008, India.
authors.forename: Sabnam
authors.initials: S
authors.lastname: Parbin
authors.affiliation: Epigenetics and Cancer Research Laboratory, Biochemistry and Molecular Biology Group, Department of Life Science, National Institute of Technology, Rourkela, Odisha 769008, India.
authors.forename: Sandip Kumar
authors.initials: SK
authors.lastname: Rath
authors.affiliation: Epigenetics and Cancer Research Laboratory, Biochemistry and Molecular Biology Group, Department of Life Science, National Institute of Technology, Rourkela, Odisha 769008, India.
authors.forename: Nibedita
authors.initials: N
authors.lastname: Pradhan
authors.affiliation: Epigenetics and Cancer Research Laboratory, Biochemistry and Molecular Biology Group, Department of Life Science, National Institute of Technology, Rourkela, Odisha 769008, India.
authors.forename: Madhumita
authors.initials: M
authors.lastname: Rakshit
authors.affiliation: Epigenetics and Cancer Research Laboratory, Biochemistry and Molecular Biology Group, Department of Life Science, National Institute of Technology, Rourkela, Odisha 769008, India.
authors.forename: Samir Kumar
authors.initials: SK
authors.lastname: Patra
keywords: Cancer; DNA methylation; DNA methyltransferases; Epigenetics; Gene silencing; Methyl-CpG-binding domain proteins