As part of our effort to investigate the carcinogenicity of 4,4'methylene-bis(2chloroaniline) (MOCA) and develop biomarkers of effects of exposure to occupational carcinogens, N-OH-MOCA-DNA adduct formation was examined in a human uroepithelial cell (HUC-PC) line sensitive to neoplastic transformation by 4-aminobiphenyl. HUC-PC cells were a generous gift from the Department of Human Oncology, University of Wisconsin Comprehensive Cancer Center (UWCCC). HUC-PC were incubated with 0, 2.5, 5 and 10 JLM N-OH-MOCA for 24 hours. Following incubations, cells were harvested, DNA isolated, and analyzed by 32p postlabeling for N-OH-MOCA-DNA adducts. At 10 M, two adducts were identified. The major adduct, with chromatographic properties similar to N-(deoxyadenosine-8-yl)-4-amino-3 chlorobenzyl alcohol, formed at a level of 430 +/- 23 fmol/ ug DNA +/- S.E.. The same major adduct was found in DNA from exfoliated urothelial cells found in urine of a worker acutely exposed to MOCA and in liver DNA of rats dosed with MOCA. The site of MOCA-induced tumor formation in the rat is the liver and in humans MOCA is a suspected bladder carcinogen. The minor adduct was found (261 +/- 158 fmol/ug DNA +/- S.E.) in the 10 JLM-treated HUC-PC, but was not detectable in HUC cells treated at the lower doses. However, this adduct was observed in rats dosed with MOCA. In the concentrations examined, there was no significant difference in the level of major adduct in the HUC cells. Preliminary results suggest that only the 10 uM treated HUC-PC were malignantly transformed.
The Toxicologist. Society of Toxicology 34th Annual Meeting, March 5-9,1995, Baltimore, Maryland