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 canc er risk. To assess these factors in normal human colon cells, we determined background levels of DNA breaks or oxidized bases and of glutathione S-tra nsferases (GSTs) as potential biomarkers of risk and chemoprevention, respe ctively. Also, genotoxicity by compounds involved in lipid peroxidation was determined to elucidate possible sources of damage. Cells were isolated fr om sigmoid biopsies of 51 donors and processed with the comet assay to reve al genetic damage. GST proteins were analyzed immunologically. HT29 clone 1 9A colon tumor cells, resembling primary cells, were treated with 2-trans-h exenal (400 mu M) or hydrogen peroxide (75 mu M) and processed for damage, Fifteen percent of primary colon cells contained strand breaks; 22% contain ed additional oxidized bases, with distinct sex differences. Similar damage was found in HT29 clone cells and is induced by both test compounds. GST l evels were similar in both cell types. The comet assay is sufficiently sens itive to detect oxidative genetic damage in small amounts of cells from sma ll amounts of biopsies. Lipid peroxidation is a possible risk factor. Toget her with GST as a potential biomarker of chemoprevention, the technique may serve as a valuable biomarker to assess exposure to risk factors.