Epigenetics reactivation of Nrf2 in Prostate TRAMP C1 Cells by curcumin analog FN1

摘要

It has previously been demonstrated that curcumin is effective against prostate cancer growth and progression in TRAMP mice, potentially acting through the epigenetic modification of the Nrf2 gene and the subsequent induction of the Nrf2-mediated anti-oxidative stress cellular defense pathway. FN1 is a synthetic curcumin analog that shows stronger anti-cancer activity than curcumin. The purpose of this study was to investigate a potential epigenetic effect of FN1 that restores Nrf2 gene expression in TRAMP-C1 cells. Stably transfected HepG2-C8 cells were used to investigate the effect of FN1 on the Nrf2-ARE pathway. Real-time quantitative PCR and western blotting were used to study the influence of FN1 on endogenous Nrf2 and its downstream genes. Bisulfite genomic sequencing (BGS) and methylated DNA immunoprecipitation (MeDIP) were then performed to examine the methylation profile of the Nrf2 promoter. An anchorage-independent colony-formation assay was conducted to test the tumor inhibitory effect of FN1. Epigenetic modification enzymes, including DNMTs and HDACs, were investigated by western blotting. Luciferase reporter assay indicated FN1 was more potent than curcumin in activating the Nrf2-ARE pathway. FN1 increased the mRNA and protein expression of Nrf2 and downstream genes, such as HO-1, NQO1, and UGT1A1. FN1 significantly inhibited the colony formation of TRAMP-C1 cells. BGS and MeDIP assays revealed that FN1 treatment (250 nM for 3 days) decreased the level of CpG methylation of the Nrf2 promoter. FN1 also downregulated epigenetic modification enzymes. In conclusion, our results suggest that FN1 is a novel anti-cancer agent for prostate cancer. FN1 can activate the Nrf2-ARE pathway, inhibit the colony formation of TRAMP-C1 cells and increase the expression of Nrf2 and downstream genes potentially through the decreased expression of keap1 coupled with CpG demethylation of the Nrf2 promoter. This CpG demethylation effect may come from decreased epigenetic modification enzymes, such as DNMT1, DNMT3a, DNMT3b and HDAC4.