An in vitro/in vivo transformation system has been developed as a model for bladder tumorigenesis. SV40-immortalized human uroepithelial cells are exposed to putative carcinogens and then implanted into athymic nude mice to testfortumorigenesis. Studies with 4-aminobiphenyl(4-ABP) demonstrated that one cell line, SV-HUC-PC, was sensitive to chemical-induced transformation and another line, SV-HUC-BC, was refractory. We are currently testing this system as a model to identify occupational carcinogens and develop biomarkers of exposure and effects of exposure. As part of this study, we examined P450- dependent metabolism, glutathione transferase, and the effects of chemicals on deoxyribonucleic acid(DNA)synthesis and repair in SV-HUC-PC and SV-HUCBC. Activities for CYP1A1/1A2, CYP3A, and CYP2B1/2B2 were estimated by determining o-dealkylation of ethoxy-, benzoxy-, and pentoxy-resorufin, respectively. Coumarin hydroxylase and p-nitrophenol hydroxylase were used to estimate CYP2A and CYP2E1, respectively. SV-HUC-PC microsomes had five fold greater CYP1A1/1A2 activity and two fold higher CYP3A activity than SV-HUCBC. CYP2B1/2B2 and CYP2A activities and glutathione transferase were not different between the two cell lines. DNA synthesis and repair, by BrdU incorporation, was not different between the two lines when N-methyl-N-nitroN-nitrosoguanidine (MNNG) or other reactive metabolites were tested; however, SV-HUC-PC was more sensitive to n -nitrosodimethylamine, 4-ABP, and 4,4-methylene bis (2-chloroaniline) (MOCA). The data demonstrate that, while these cells have retained form-specific P450 activities, SV-HUC-PC has greater CYP1A1/1A2 and CYP3A activities.
John E. Snawder, NIOSH, Taft Laboratories, MS-C23, 4676 Columbia Parkway, Cincinnati, OH 45226, USA