Pharmacodynamics of curcumin as DNA hypomethylation agent in restoring the expression of Nrf2 via promoter CpGs demethylation

Abstract

Prostate cancer (PCa) is one of the most deadly malignancies among men in the United States. Although localized prostate cancer can be effectively treated via surgery or radiation, metastatic disease is usually lethal. Recent evidence suggests that the development and progression of human prostate cancer involves complex interplay between epigenetic alterations and genetic defects. We have recently demonstrated that Nrf2, a master regulator of cellular antioxidant defense systems, was epigenetically silenced during the progression of prostate tumorigenesis in TRAMP mice. The aim of this study is to investigate the potential of curcumin (CUR), a dietary compound that we have reported to be able to prevent the development of prostate cancer in TRAMP mice, as a DNA hypomethylation agent. Using bisulfite genomic sequencing (BGS), treatment of TRAMP C1 cells we showed that CUR reversed the methylation status of the first 5 CpGs in the promoter region of the Nrf2 gene. Methylation DNA immunoprecipitation (MeDIP) analysis revealed that CUR significantly reduced the anti-mecyt antibody binding to the first 5 CpGs of the Nrf2 promoter, corroborated the BGS results. Demethylation of Nrf2 was found to be associated with the re-expression of Nrf2 and one of its downstream target gene, NQO-1, one of the major anti-oxidative stress enzymes, both at the mRNA and protein levels. Taken together, our current study suggests that CUR can elicit its prostate cancer chemopreventive effect, potentially at least in part, through epigenetic modification of the Nrf2 gene with its subsequent induction of the Nrf2-mediated anti-oxidative stress cellular defense pathway.