Abstract 5084: Epigenetic modifications involving reactivation of RECK inhibiting MMP-9 and MMP-2 in prostate cancer

Metastasis is responsible for more than 90% of prostate cancer-associated mortality in the United States. One of the distinctive reason for metastasis has been the imbalance of matrix metalloproteinases (MMPs) as a result of reduced expression of RECK (reversion-inducing-cysteine-rich protein with Kazal motifs) a novel tumor suppressor. RECK has been shown to be a potent inhibitor of MMP-2 and MMP-9. Loss of RECK has been frequently identified in clinical prostate cancer specimens and prostate cancer cell lines, therefore mechanistic understanding of its loss and approaches to restore its expression would facilitate inhibition of 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 has ability to restore induction of RECK and play a key role in suppressing invasiveness in prostate cancer. Human prostate cancer LNCaP tumor were implanted in the ventral prostate of athymic nude mice for 2 weeks followed by per-oral intake of GTP at 7.5 and 15.0 mg/kg body weight freshly prepared in 100µl PBS. Other groups were treated with DNA methyltransferase inhibitor-5-aza-29-deoxycytidine (AZA), histone deacetylase inhibitor-trichostatin A (TSA) and histone methyltransferase inhibitor-3-Deazaneplanocin A (DZNep) individually at 0.1 mg/kg body weight intraperitoneally at alternate days/week; and combination of AZA+TSA and DZNep+TSA at similar doses and times. Treatment of mice with GTP resulted in marked decrease in tumor growth and its local invasion in dose dependent manner, compared to treatment with epigenetic inhibitors and their combination after 8 weeks of intervention. GTP treatment significantly reduced serum levels of MMP-2, MMP-9 and VEGF, compared to treatment with epigenetic inhibitors alone. Combination of AZA+TSA exhibited similar effect which was equivalent to the lower dose of GTP treatment. Furthermore, GTP treatment significantly reduced EZH2 and H3K27me3 and class I HDAC protein levels in tumors. GTP partially reversed RECK hypermethylation and significantly enhanced its expression in the tumor tissue. Similar findings were noted in cell culture where treatment of PC-3 and LNCaP cells with 20µM EGCG and 10µg/mL GTP for 72 h significantly induced RECK expression at mRNA and protein levels along with decrease invasiveness in these cells. Our findings suggest that induction of RECK is a key epigenetic event reactivated by GTP/EGCG that results in suppression of MMP-2/MMP-9, matrix degradation and angiogenesis to delay prostate cancer invasion and its subsequent progression. Citation Format: Eswar Shankar, Omair Iqbal, Natarajan Bhaskaran, Gauri Deb, Gregory T. MacLennan, Pingfu Fu, Sanjay Gupta. Epigenetic modifications involving reactivation of RECK inhibiting MMP-9 and MMP-2 in prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5084.