Submitted to: Journal of Nutrition
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/28/2003
Publication Date: 8/1/2003
Citation: Zeng, H., Davis, C.D. 2003. Down-regulation of proliferating cell nuclear antigen gene expression occurs during cell cycle arrest induced by human fecal water in colonic HT-29 cells. Journal of Nutrition. 133:2682-2687. Interpretive Summary: The association between colon cancer and diet has been well established in human epidemiologic studies as well as animal studies, and dietary factors significantly affect the cytotoxicity of fecal water. The colon epithelium is in an equilibrium between cell birth and death, which plays a critical role in tumor development. It is important to understand the mechanism of human fecal water that affects this process which may lead to the development of sensitive biological indicators related to human fecal water and colon cancer prevention. The current data suggest that human fecal water changes the expression of growth arrest genes, and inhibits cell cycle progression. The implications of these data in the development of biological indicators related to human fecal water and colon cancer are discussed. These findings will be useful for scientists and health-care people who are interested in early detection regarding the influence of dietary factors on etiology of colon cancer.
Technical Abstract: Cancer is a disease in which the cell cycle is altered; the elucidation of the mechanisms by which constituents of human fecal water regulate the cell cycle can lead to a better understanding of their roles in colon cancer prevention. The purpose of the present study was to investigate the molecular basis for the effect of human fecal water on HT-29 cell cycle progression. Sodium selenite was used as a control. Both human fecal water (2.5-5.0%) and selenite (3-4 µmol/L) significantly (p<0.0001) inhibited cell growth. Cell-cycle analysis revealed that human fecal water decreased S and G2 phase cells and increased G1 phase cells. In contrast, selenite decreased G1 phase cells and increased S and G2 phase cells. Gene array analysis demonstrated that both 5% human fecal water and 4 µmol/L selenite increased the mRNA level of cyclin-dependent kinase inhibitor gene P21waf1 by 2-3 fold. Interestingly, the MRNA levels of cyclin A and proliferating cell nuclear antigen (PCNA) were dramatically decreased in fecal water but not in selenite treated HT-29 cells. In contrast, the mRNA level of DNA-damage-inducible transcript 1, gadd45 was significantly increased in selenite but not in fecal water treated HT-29 cells. Furthermore, a PCNA gene promoter was cloned into a luciferase reported construct and its activity was significantly reduced in a dose-dependent manner in fecal water but not in selenite treated cells. Collectively, these results suggest human fecal water and selenite differentially induce growth arrest genes, and PCNA gene expression is uniquely and highly sensitive to human fecal water.