Epigenetic regulation of NDGA and its synergistic inhibition with EZH2 inhibitors in prostate cancer via NRP1

Epigenetic modulating drugs are emerging as promising cancer treatments. We previously showed that a natural compound, nordihydroguaiaretic acid (NDGA), exerted anti-prostate cancer effects in vitro and in vivo. In this study, we elucidated the anticancer mechanisms of NDGA against prostate cancer. Using integrating bioinformatics analysis and proteomic research, we identified 12 differentially expressed proteins in NDGA-treated PC3 cells that were associated with EZH2, a histone methyltransferase and a catalytic component of polycomb repressive complex 2 (PRC2), which catalyzed the trimethylation of histone H3 at Lys27 (H3K27me3). We showed that NDGA (5, 10, 20 μmol/L) dose-dependently inhibited EZH2 expression in PC3 cells by increasing its degradation and inhibiting its transcription. We demonstrated that NDGA targeted neuropilin 1 (NRP1) in PC3 cells, inhibiting the EZH2/H3K27me3 and PI3K/AKT/mTOR pathways and the expression of E2F1. NDGA blocked E2F1 binding to the EZH2 promoter, decreasing EZH2 and H3K27me3 levels. On the other hand, NDGA inhibited CBP/p300, decreased H3K27ac levels, and synergized with the EZH2 inhibitor EPZ6438 against PC3 cells. In conclusion, NDGA is a potential epigenetic antineoplastic agent that downregulates EZH2 and H3K27me3 through the NRP1 and PI3K/AKT/mTOR pathways and exerts a synergistic antitumor effect with H3K27ac and EZH2 inhibitors, suggesting that it could be a valuable therapeutic option for prostate cancer.