Abstract 2609: Epigenetic reactivation of TIMP-3 in human prostate cancer cells by green tea polyphenols

Abstract Metastasis is responsible for more than 90% of prostate cancer-associated mortality in the United States. Metastasis is facilitated by remodeling of the extracellular matrix by a family of proteolytic enzymes known as matrix metalloproteinases (MMPs). These zinc-dependent proteases elicit pivotal role in the proteolytic degradation of structural components of extracellular matrix contributing to the metastatic process. High levels of MMP-2/9 in the plasma and urine has been correlated with metastasis. MMPs are produced in a latent form (pro-MMP) that require activation and are inhibited by tissue inhibitors of matrix metalloproteinases (TIMPs). TIMPs inhibit MMPs by binding in a 1:1 stoichiometry through strong noncovalent interactions. In prostate cancer, low levels of TIMP3 has been associated with aggressive tumor phenotype and poor disease-free survival. Loss of TIMP3 in prostate cancer is attributed to epigenetic silencing tipping the balance towards active MMPs driving metastasis. Green tea polyphenols (GTP) and its major constituent, epigallocatechin-3-gallate (EGCG) has been shown to suppress prostate cancer metastasis, however the mechanism has not been fully elucidated. We determined whether treatment with GTP/EGCG has ability to restore induction of TIMP3 and play a key role in suppressing invasiveness in prostate cancer. Treatment of prostate cancer LNCaP and DUPRO cells with 10μg/mL GTP and 20μM EGCG for 72 h significantly induced TIMP3 mRNA and protein levels. Silencing of enhancer of zeste homolog 2 (EZH2) and class I histone deacetylases (HDACs) significantly increased the expression of TIMP3 which was independent of DNA hypermethylation. Treatment of prostate cancer cells with GTP/EGCG significantly reduced EZH2 and class I HDAC protein levels; H3K27 trimethylation activity; and transcriptional activation of TIMP-3 was found to be associated with decreased EZH2 localization and H3K27 trimethylation enrichment at the TIMP3 promoter with a concomitant increase in histone H3K9/18 acetylation. EGCG/GTP treatment also caused a global reduction in histone methylation thereby increasing histone acetylation to revive and activate TIMP3 levels. Furthermore, EGCG/GTP exposure significantly reduced MMP2/9 gelatinolytic activity and abrogated invasive and migration capabilities in prostate cancer cells. Taken together, our findings suggests that TIMP-3 induction could be a key epigenetic event modulated by GTPs in restoring MMP: TIMP balance to delay prostate cancer invasion and metastasis. Citation Format: Gauri Deb, Vijay S. Thakur, Eswar Shankar, Sanjay Gupta. Epigenetic reactivation of TIMP-3 in human prostate cancer cells by green tea polyphenols. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2609.