title: Reversal of hypermethylation and reactivation of glutathione S-transferase pi 1 gene by curcumin in breast cancer cell line.
abstract: One of the mechanisms for epigenetic silencing of tumor suppressor genes is hypermethylation of cytosine residue at CpG islands at their promoter region that contributes to malignant progression of tumor. Therefore, activation of tumor suppressor genes that have been silenced by promoter methylation is considered to be very attractive molecular target for cancer therapy. Epigenetic silencing of glutathione S-transferase pi 1, a tumor suppressor gene, is involved in various types of cancers including breast cancer. Epigenetic silencing of tumor suppressor genes can be reversed by several molecules including natural compounds such as polyphenols that can act as a hypomethylating agent. Curcumin has been found to specifically target various tumor suppressor genes and alter their expression. To check the effect of curcumin on the methylation pattern of glutathione S-transferase pi 1 gene in MCF-7 breast cancer cell line in dose-dependent manner. To check the reversal of methylation pattern of hypermethylated glutathione S-transferase pi 1, MCF-7 breast cancer cell line was treated with different concentrations of curcumin for different time periods. DNA and proteins of treated and untreated cell lines were isolated, and methylation status of the promoter region of glutathione S-transferase pi 1 was analyzed using methylation-specific polymerase chain reaction assay, and expression of this gene was analyzed by immunoblotting using specific antibodies against glutathione S-transferase pi 1. A very low and a nontoxic concentration (10 µM) of curcumin treatment was able to reverse the hypermethylation and led to reactivation of glutathione S-transferase pi 1 protein expression in MCF-7 cells after 72 h of treatment, although the IC50value of curcumin was found to be at 20 µM. However, curcumin less than 3 µM of curcumin could not alter the promoter methylation pattern of glutathione S-transferase pi 1. Treatment of breast cancer MCF-7 cells with curcumin causes complete reversal of glutathione S-transferase pi 1 promoter hypermethylation and leads to re-expression of glutathione S-transferase pi 1, suggesting it to be an excellent nontoxic hypomethylating agent.
authors.affiliation: 1 Molecular Oncology Division, Dr. B.R. Ambedkar Center for Biomedical Research (ACBR), University of Delhi (North Campus), Delhi, India.
authors.forename: Umesh
authors.initials: U
authors.lastname: Kumar
authors.affiliation: 2 Department of Biochemistry, Postgraduate Institute of Medical Education & Research (PGIMER), Chandigarh, India.
authors.forename: Ujjawal
authors.initials: U
authors.lastname: Sharma
authors.affiliation: 1 Molecular Oncology Division, Dr. B.R. Ambedkar Center for Biomedical Research (ACBR), University of Delhi (North Campus), Delhi, India.
authors.forename: Garima
authors.initials: G
authors.lastname: Rathi
mesh_terms: D001943:Breast Neoplasms / Q000188:drug therapy* / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D003474:Curcumin / Q000494:pharmacology*; D004249:DNA Damage; D019175:DNA Methylation / Q000187:drug effects*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic; D051549:Glutathione S-Transferase pi / Q000235:genetics*; D006801:Humans; D061986:MCF-7 Cells
chemical_list: C496556:GSTP1 protein, human; D051549:Glutathione S-Transferase pi; D003474:Curcumin
keywords: GSTP1; MCF-7; Methylation; breast cancer; curcumin