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Title: Skin tumorigenesis by initiators and promoters of different chemical structures in lines of mice selectively bred for resistance (Car-r) or susceptibility (Car-s) to two-stage skin carcinogenesis. Author: Saran A, Pazzaglia S, Rebessi S, Bouthillier Y, Pioli C, Covelli V, Mouton D, Doria G, Biozzi G. Journal: Int J Cancer; 1999 Oct 29; 83(3):335-40. PubMed ID: 10495425. Abstract: Carcinogenesis-resistant (Car-R) and carcinogenesis-susceptible (Car-S) mice were obtained applying a bi-directional selective breeding approach to a two-stage skin carcinogenesis protocol, using 9,10-dimethyl-1,2-benzanthracene (DMBA) as initiator and 12-O-tetradecanoylphorbol-13-acetate (TPA) as promoter. Sixteen generations of selection produced a remarkable interline difference in responsiveness to two-stage skin carcinogenesis between Car-R and Car-S: identical DMBA (25 microgram) and TPA (5 microgram) doses induced papillomas in 100% of Car-S compared with 3.3% of Car-R mice and maximal responses of 14.3 or 0.03 papillomas/mouse, respectively, despite the shorter promotion applied to Car-S (49 vs. 208 days). To define the factors determining this great difference, Car-R and Car-S mice were challenged by initiators/promoters chemically unrelated to those used for selection. Both lines were subjected to either initiation by N-methyl-N-nitrosourea (MNU) followed by TPA promotion, or promotion by benzoyl peroxide, or 1,8-dihydroxy-3-methyl-9-anthrone (chrysarobin) following DMBA initiation. Initiation with MNU induced a 10-fold tumour incidence in Car-S compared with Car-R mice, and a 32-fold difference in tumour induction rate. The 2 lines also differed markedly in susceptibility to benzoyl peroxide promotion: Car-S mice initiated with 25 microgram DMBA and promoted with 7.5 mg benzoyl peroxide showed a 12-fold tumour incidence and a 103-fold tumour induction rate compared with the corresponding Car-R group. Both lines, however, were refractory to chrysarobin promotion. The progression of papillomas to carcinomas was examined in all Car-S groups. The incidence of mice that developed carcinomas was 57% in MNU-initiated mice. Benzoyl peroxide was also able to promote carcinoma development in Car-S mice, though with a lower incidence (30.4%) than TPA.[Abstract] [Full Text] [Related] [New Search]