Neoplastic transformation and DNA-binding of 4,4'-methylenebis(2-chloroaniline) in SV40-immortalized human uroepithelial cell lines.
The tumorigenic transformation of certain occupationally significant chemicals, such as N-hydroxy-4-4'-methylenebis[2-chloroaniline] (N-OH-MOCA), N-hydroxy-ortho-toluidine (N-OH-OT), 2-phenyl-1,4-benzoquinone (PBQ) and N-hydroxy-4-aminobiphenyl (N-OH-ABP) were tested in vitro using the well established SV40-immortalized human uroepithelial cell line SV-HUC.PC. SV-HUC cells were exposed in vitro to varying concentrations of N-OH-MOCA, N-OH-OT, N-OH-ABP and PBQ that caused approximately 25% and 75% cytotoxicity. The carcinogen treated cells were propagated in culture for about six weeks and subsequently injected subcutaneously into athymic nude mice. Two of the fourteen different groups of SV-HUC.PC treated with different concentrations of N-OH-MOCA, and one of the three groups exposed to N-OH-ABP, formed carcinomas in athymic nude mice. 32P-postlabeling analyses of DNA isolated from SV-HUC.PC after exposure to N-OH-MOCA revealed one major and one minor adduct. The major adduct has been identified as the N-(deoxyadenosin-3',5'-bisphospho-8-yl)-4-amino-3-chlorob enz yl alcohol (pdAp-ACBA) and the minor adduct as N-(deoxyadenosin-3',5'-bisphospho-8-yl)-4-amino-3-chlorot oluene (pdApACT). Furthermore, SV-HUC.PC cytosols catalyzed the binding of N-OH-MOCA to DNA, in the presence of acetyl-CoA, to yield similar adducts. The same adducts were also formed by chemical interaction of N-OH-MOCA with calf thymus DNA, suggesting that the aryl nitrenium ion may be the ultimate reactive species responsible for DNA binding. The tumorigenic activity of N-OH-MOCA in this highly relevant in vitro transformation model, coupled with the findings that SV-HUC.PC cells formed DNA-adducts in vitro and contained enzyme systems that activated N-OH-MOCA to reactive electrophilic species that bound to DNA, strongly suggest that MOCA could be a human bladder carcinogen. These findings are consistent with the International Agency for Research on Cancer's classification of MOCA as a probable human carcinogen.
Swaminathan
S
S
University of Wisconsin Comprehensive Cancer Center, Madison 53792, USA.
Frederickson
S M
SM
Hatcher
J F
JF
Reznikoff
C A
CA
Butler
M A
MA
Cheever
K L
KL
Savage
R E
RE
D000818:Animals; D001665:Binding Sites; D002273:Carcinogens / Q000378:metabolism / Q000633:toxicity*; D002461:Cell Line, Transformed; D002471:Cell Transformation, Neoplastic; D004247:DNA / Q000187:drug effects* / Q000378:metabolism; D005260:Female; D006801:Humans; D008753:Methylenebis(chloroaniline) / Q000378:metabolism / Q000633:toxicity*; D051379:Mice; D008819:Mice, Nude; D013539:Simian virus 40 / Q000502:physiology; D001749:Urinary Bladder Neoplasms / Q000139:chemically induced; D014566:Urogenital System / Q000166:cytology / Q000187:drug effects*
D002273:Carcinogens; D008753:Methylenebis(chloroaniline); D004247:DNA