Analysis of DNA strand breaks, oxidized bases, and glutathione S-transferase P1 in human colon cells from biopsies

The balance of genetic damage and deactivating enzymes is decisive for cancer risk. To assess these factors in normal human colon cells, we determined background levels of DNA breaks or oxidized bases and of glutathione S-transferases (GSTs) as potential biomarkers of risk and chemoprevention, respectively. Also, genotoxicity by compounds involved in lipid peroxidation was determined to elucidate possible sources of damage. Cells were isolated from sigmoid biopsies of 51 donors and processed with the comet assay to reveal genetic damage. GST proteins were analyzed immunologically. HT29 clone 19A colon tumor cells, resembling primary cells, were treated with 2-trans-hexenal (400 microM) or hydrogen peroxide (75 microM) and processed for damage. Fifteen percent of primary colon cells contained strand breaks; 22% contained additional oxidized bases, with distinct sex differences. Similar damage was found in HT29 clone cells and is induced by both test compounds. GST levels were similar in both cell types. The comet assay is sufficiently sensitive to detect oxidative genetic damage in small amounts of cells from small amounts of biopsies. Lipid peroxidation is a possible risk factor. Together with GST as a potential biomarker of chemoprevention, the technique may serve as a valuable biomarker to assess exposure to risk factors.