Abstract 253: Green tea polyphenol-mediated epigenetic reactivation of TIMP-3 reduces invasiveness and gelatinolytic activity in human breast cancer cells
Authors: Deb Gauri , Thakur Vijay S. , Limaye Anil M. , Gupta Sanjay 
Published: May 2015

Abstract
The molecular pathway from tumor development to clinically evident metastasis is complex and consists of multiple sequential steps. Substantial data indicate the involvement of gelatinases/ type IV collagenases (MMP-2/9) secreted by tumor cells during cancer cell invasion and metastasis. MMP-2/9 are produced in a latent form as pro-matrix metalloproteinases that require activation and are inhibited by tissue inhibitors of matrix metalloproteinases (TIMPs). TIMPs are natural inhibitors of MMPs and are involved in diverse biological processes including cell proliferation, apoptosis, invasion, metastasis and angiogenesis. Four TIMP genes (TIMP-1, -2, -3, -4) and proteins are known in human which inhibit active form of most MMPs but with different affinities. TIMPs inhibit MMPs by binding in a 1:1 stoichiometry through strong non-covalent interaction. The balance between active MMPs and TIMPs determine tumor progression by regulating the net activity of MMPs. Aberrant epigenetic silencing of TIMP-3 has been implicated in the pathogenesis and metastasis of breast cancer. In the present study, we demonstrate that green tea polyphenols (GTP) and its major constituent, epigallocatechin-3-gallate (EGCG) mediate epigenetic induction of TIMP-3 levels and play a key role in suppressing invasiveness and gelatinolytic activity of MMP-2/9 in breast cancer cells. Treatment of MCF-7 and MDA-MB-231 breast cancer cells with 20μM EGCG and 10μg/ml GTP for 72 h significantly induces TIMP-3 mRNA and protein levels. Interestingly, investigations into the molecular mechanism revealed that TIMP-3 repression in breast cancer cells is mediated by epigenetic silencing mechanism(s) involving increased activity of the enhancer of zeste homolog 2 (EZH2) and class I histone deacetylases, independent of promoter DNA hypermethylation. Treatment of breast cancer cells with GTP/EGCG significantly reduced EZH2 and class I HDAC protein levels. Furthermore, transcriptional activation of TIMP-3 was found to be associated with decreased EZH2 localization and H3K27 trimethylation enrichment at the TIMP-3 promoter with a concomitant increase in histone H3K9/18 acetylation. Our findings highlight TIMP-3 induction as a key epigenetic event modulated by GTP/EGCG in restoring the MMP:TIMP balance to delay breast cancer progression and invasion. Although case-control and epidemiological studies provide some clues that regular consumption of GTP and EGCG could decrease the risk of breast cancer invasion and/or progression however these studies do not provide further insight into the molecular mechanism, related to tumor inhibition. Based on our present findings, TIMP-3 can be used as a surrogate marker of GTP/EGCG response and warrants further investigation through well designed clinical trial.
Citation Format: Gauri Deb, Vijay S. Thakur, Anil M. Limaye, Sanjay Gupta. Green tea polyphenol-mediated epigenetic reactivation of TIMP-3 reduces invasiveness and gelatinolytic activity in human breast cancer cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 253. doi:10.1158/1538-7445.AM2014-253