Abstract 1628: Tumor suppressor gene demethylation and reactivation in human colon cancer cells by black raspberry anthocyanins

Abstract

Our laboratory has shown that the anthocyanins (ACs) in black raspberries (BRBs) are responsible for much of their chemopreventive effects in the rat esophagus. The present study was undertaken to determine the effects of BRB ACs on human colon cancer cells in vitro. Three days of AC treatment at 5 and 25 μg/ml medium significantly decreased cell proliferation and increased apoptosis in HCT116, Caco2, and SW480 human colon cancer cell lines. The ACs also reduced the activities and protein expression levels of DNA methyltransferases 1 and 3 (DNMT1, DNMT3) in all three cell lines. Promoter methylation of p16 (CDKN2A) and the Wnt pathway inhibitors, Sfrp2, Sfrp5 and Wif1, was decreased by AC treatment resulting in increased mRNA expression levels of all three Wnt inhibitors. ACs did not alter global methylation LINE-1. DNMT1 and DNMT3B knockout (KO) HCT116 cells were generated using siRNA to determine the role of these methyltransferases in AC-induced demethylation. In DNMT1 KO cells, the promoter methylation of Sfrp5 was reduced when compared with wild type HCT116 cells. AC treatment further reduced promoter methylation of Sfrp5 in DNMT1 KO cells suggesting that the ACs targeted protein(s) other than DNMT1 to regulate methylation. Promoter methylation of Sfrp5 was decreased to almost zero by treatment of DNMT3B KO cells with ACs. Interestingly, promoter methylation of p16 was reduced in both DNMT1 and DNMT3B KO cells, and AC treatment further reduced p16 methylation in both lines. In conclusion, these results suggest that ACs demethylated and reactivated tumor suppressor genes through regulation of DNMT1 and DNMT3B. This research was supported by NCI grant CA148818. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1628. doi:1538-7445.AM2012-1628