Presentation Abstract

Abstract Number: 1325
Presentation Title: Organ, species and sex differences in mutagenesis induced by butyl-hydroxybutyl-N-nitrosamine in big blue transgenic rodents as the basis for the strict organ specificity of this environmental carcinogen metabolite
Presentation Time: Monday, Apr 04, 2011, 8:00 AM -12:00 PM
Location: Exhibit Hall A4-C, Poster Section 15
Poster Section: 15
Poster Board Number: 12
Author Block: Zhiming He1, Zhong-Lin Zhao 1, Wieslawa Kosinska1, Xue-Ru Wu2, Joseph B. Guttenplan1. 1New York Univ. College of Dentistry, New York, NY; 2New York Univ. School of Medicine, New York, NY
Abstract Body: Although butyl-hydroxybutyl-N-nitrosamine (BBN) is a powerful carcinogen that specifically causes bladder cancer in rodents, the reason for such a high degree of organ specificity is unclear. Mutagenesis induced by BBN in a chromosomally incorporated mutagenesis reporter gene was measured in bladder urothelial cells and smooth muscle cells of mice or rats and compared with mutagenesis in liver, kidney, ureter and forestomach. BBN was administered as a 0.05% solution in water for 2 weeks followed by 4 weeks of water to 6 male and female mice and 4 male rats. All animals were euthanized at 6 weeks. Since mutagenesis in the reporter gene is a surrogate for mutagenesis in general, we hypothesized that mutations also induced in critical growth control genes would contribute to the tumor formation induced by BBN. The mutant fractions in urothelial cells were: 257 +/- 25 mutants / 105 pfu for male mice, 276 +/- 43 for female mice and 54 +/- 6 for rats. In contrast, the mutant fractions in bladder smooth muscle cells were 8-9 fold lower than these values in all animals. In non-bladder tissues such as liver, kidney, ureter and forestomach, the mutant fractions were between 2 and 5 mutants / 105 pfu, a level comparable to the control groups without BBN treatment. Hence mutagenesis correlated extremely well with the organ specificity for cancer induction by BBN. Additionally, mutagenesis level was found to be significantly higher in mice than in rats, consistent with the fact that BBN is a much more potent bladder carcinogen in mice. Finally, no significant difference in mutagenicity of BBN between male and female mice was observed, suggesting that post-initiation processes may be responsible for the gender difference in bladder tumor susceptibility. BBN is a primary metabolite of the environmental carcinogen, dibutylnitrosamine and hence a potential human carcinogen. These results provide molecular explanations to the bewildering organ and species specificity of BBN, and indicate that BBN-induced mutagenesis in the urinary bladder represents a highly appropriate model for initiation of bladder cancer, and combined with other models can help elucidate distinct steps in bladder carcinogenesis. Supported by an NYU Centers of Excellence Seed Grant.