Abstract 1872: Treatment of colon cancer with black raspberries reduces DNA Methyltransferase 1-associated gene methylation

Abstract

Abstract Black raspberries (BRB) confer anti-cancer effects in gastrointestinal organs via a number of mechanisms. Recently, we have shown that BRB are capable of reversing aberrant promoter-region methylation and silencing of tumor suppressor genes in colorectal cancers in two separate clinical trials. Familial adenomatous polyposis (FAP) is characterized by inherited mutation of the APC gene resulting in uncontrolled growth of pre-cancerous polyps and 100% risk of colon cancer by age 40. In a 9-month clinical trial, a total of fourteen FAP patients were treated with two 700 mg BRB suppositories intra-rectally once a day. Seven of the 14 patients consumed a slurry containing 20g freeze-dried BRB powder three times a day while the other seven received a placebo slurry. In the second study, twenty-five colorectal cancer patients consumed a slurry containing 20g of BRB powder three times a day for a short period (2-4 weeks) before surgery. DNA from both studies was extracted from paraffin-embedded biopsies of normal and tumor tissue before and after treatment. Methylation status of the promoter regions of tumor suppressor genes were studied using MassARRAY/EpiTyper which quantifies the percent methylation of C-G units (each containing 1-3 CpGs) in target gene promoter regions The five genes studied, including p16, a cell cycle regulator, PAX6a, a development regulator, and three Wnt pathway inhibitors, SFRP2, SFRP5 and WIF1, were all positively regulated by BRB in colon tumors, however, only p16, SFRP2 and WIF1 were demethylated in rectal polyps from FAP patients. In both studies, 75% of both normal and tumor tissues showed decreased methylation of at least one tumor suppressor gene. Multiple-gene demethylation was different in the two studies. More than one gene was found to be reduced in methylation in a greater percentage of colon tumors (55%) than in normal tissues (26%) from colon cancer patients. In contrast, in the FAP study, more than one gene was demethylated in a greater percentage of normal tissue (23%) than in polyps (7%). However, the effect of BRB on the expression of DNA Methyltransferase 1 (DNMT1), a maintenance methylation enzyme, was similar in both colon cancers and polyps from FAP patients. In both FAP and colon cancers, demethylation of at least one gene coincided with DNMT1 decrease in a greater percentage of tumor tissues (63%, 79%) than in normal tissues (20%, 50%), respectively. This correlation suggests that in both polyps from FAP patients and in colon cancers, BRB action on methylation acts through DNMT1 reduction to a greater extent in tumor tissue than in normal tissue. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1872.