Poster Topical Area: Diet and Cancer
Poster Board Number: 229
Objectives: Butyrate, an intestinal microbiota metabolite of dietary fiber exhibits colon cancer preventive effects. In contrast, high dietary fat causes an increase in fecal secondary bile acids such as deoxycholic acid (DCA) which are implicated as promoters of colon cancer. Long term consumption of a high-fat diet may selectively enrich colonic epithelial cells with an abnormally high resistance to bile acid-induced apoptosis. However, the effect of butyrate on DCA-resistant cells remains unclear. We tested the hypothesis that physiological concentrations of butyrate inhibit DCA-resistant colonic cell proliferation.
Methods: With the use of HCT116 as parent colonic cells, we developed a DCA-resistant cell line (DCA-RCL) after 8 to 10 cell culture passages in the presence of DCA (0.2 mmol/L). We used cell cycle, apoptosis, PCR array, biochemical, western blotting and immunofluorescent assays to determine butyrate's inhibitory effects on DCA-RCL cell proliferation.
Results: DCA treatment (0.1 to 0.3 mmol/L) increased intracellular reactive oxygen species (ROS) and cell apoptosis in HCT116 cells, but to a much lesser extent in DCA-RCL cells. In agreement with this observation, we identified 43 anti-apoptotic genes with more than one fold increase in mRNA levels in DCA-RCL cells when compared with the parent HCT116 cells using a PCR array assay. These genes are involved in tumor necrosis factor alpha receptor, caspase recruitment domain-containing protein, and B-cell lymphoma-2 regulated pathways. More importantly, butyrate treatment (0.5 to 2 mmol/L) induced cell cycle arrest, apoptosis, and inhibited DCA-RCL cell proliferation. At the molecular level, butyrate reduced p38 mitogen-activated protein kinase/cellular myelocytomatosis oncogene protein level, a cell proliferation promoting pathway.
Conclusions: Collectively, we developed / characterized DCA-RCL cells and showed that butyrate effectively inhibited their cell proliferation. These data suggest that butyrate can protect against colon carcinogenesis through specific targeting of DCA-resistant colonic cells.
USDA/ARS, Grand Forks Human Nutrition Research Center
Grand Forks, North Dakota