An in vitro/in vivo transformation system has been developed as a model for bladder tumorigenesis (Bookland et al, Cancer Res 52: 1606-1614). 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. This study 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 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.
The Toxicologist. Society of Toxicology 34th Annual Meeting, March 5-9,1995, Baltimore, Maryland