A53 Research suggests strong correlations between the inflammation process and colon cancer progression, making it an attractive target for anti-inflammatory drugs and compounds. Muscadines (Vitis rotundifolia), a grape species native to the Southeastern United States, are rich in polyphenols containing many biologically important flavonoids that may have potential anti-inflammatory and anti-oxidant properties. Current research has shown that the muscadine grape has a higher total phenolic and flavonoid content than commercially available red grapes. A hallmark of progressive colon cancers is disruption of different signaling pathways leading to increased proliferation and escape from apoptotic mechanisms. We hypothesize that extracts containing high levels of biologically important polyphenols from the muscadine pomace would induce cell cycle arrest and apoptosis in HT-29 and HT-15 colon cancer cell lines. Polyphenolic compounds were extracted from muscadine pomace using 80% methanol in 6N hydrochloric acid at 60ºC. Whole concentrated extract (WCE) was fractionized using an Oasis HLB column to yield three different muscadine fractions (MF). We compared the cytotoxic effects of both cell lines when treated with WCE versus three different muscadine fractions (MF-1, MF-2, and MF-3). Cell proliferation assays showed a decrease in viable cell proliferation in both cell lines treated with MF-3. Apoptosis was confirmed through the use of flow cytometry and we found evidence of G1 arrest in MF-3 treated cells. Immunoblots for apoptosis-related proteins suggest apoptotic activation of the caspase-3 pathway in treated cells compared to non-treated cells. We conclude that extracts of muscadine grape contain biologically active polyphenols that inhibit the growth of HT-29 and HT-15 colon cancer cells via an apoptotic pathway. Citation Information: Cancer Prev Res 2008;1(7 Suppl):A53.

A54 Retinoids are known for their role in regulating cell growth and proliferation and for activating tumor suppressor genes. We have previously shown that Retinoid X Receptor alpha (RXR alpha) is silenced in tumors of the colon cancer AOM-APCmin+ mouse model. Upon treatment with green tea, RXR alpha expression was restored and intestinal tumorigenesis was inhibited. We hypothesize that tea polyphenols, especially epigallocatechin gallate (EGCG), induce modification of gene expression through effects of DNA methyltransferases (DNMTs). We first determined the optimal range of EGCG concentration with which to treat the cells by performing cytotoxcity assays. We treated HT-29 and HCT116 colon cancer cells with EGCG concentrations of 0, 50, 100 or 150µM for 24 and 48 hours. The cell lines were chosen based on their methylation status. HCT116 cells are sensitive to methylation while HT-29 cells are not. Using nuclear fractions of the cell lysates, we probed for presence of the most common DNMTs using western blotting. We found that expression of DNMT1, DNMT3a and DNMT3b was inhibited in a dose dependent manner following treatment with EGCG at both 24 and 48 hour time points. We also used the DNMT inhibitor 5-aza-2dC as a positive control to recover DNMT expression in the cells treated with EGCG. We can conclude that the silencing of RXR alpha may be due in part to by repressing effects of EGCG on DNMT activity. Citation Information: Cancer Prev Res 2008;1(7 Suppl):A54.