Project Number: 5450-51000-036-00
Project Type: Appropriated

Start Date: Jul 21, 2004
End Date: Apr 30, 2009

Objective:
Determine the molecular and cellular mechanism(s) of action of selenium (Se) in anti-carcinogenesis. Specific objectives include 1) Determine the role of Se in cell cycle progression and apoptosis in models of colon cancer; 2) Determine the role of selenoproteins in cancer prevention and the role of dietary components in the regulation of selenoprotein activity; 3) Determine the mechanism(s) by which Se alters DNA methylation and 4) Determine the relationship of oral selenium intake with selenium status and indicators of cancer risk.

Approach:
A variety of cell culture and animal model approaches will be used. In general, cell culture experiments will be run using cell lines specific for colon. Various forms and concentrations of selenium will be added to serum-free media. Cell growth, indices of selenium status, and indices of cell cycle progression and apoptosis will be measured. These studies will be used to determine the effects of nutritional levels of selenium in supporting cellular survival signaling in human cultured colon cells, and the role of the putative anti-tumorigenic selenium-metabolite, methylselenol, in cell cycle progression and apoptosis in human cultured colon cells. Other cell culture models (colon and/or liver cell lines) will be used in siRNA knockdown studies. These experiments will determine the effect of selenium in cells in which specific genes have been knocked down by siRNA. Other studies will use knock downs of various selenoproteins to determine their role in anticarcinogenicity of selenium. Animal studies will use rats and mice to determine the effects of form and concentration of dietary selenium on 1) selenoprotein expression and activity as related to carcinogenesis, 2) carcinogen-induced aberrant crypt formation (preneoplastic colon cells) and, 3) indices of oxidative stress and one-carbon metabolism including DNA methylation of genomic and gene specific DNA.