Rapid induction of skin and mammary tumors in human c-Ha-ras proto-oncogene transgenic rats by treatment with 7,12-dimethylbenz[a]anthracene followed by 12-O-tetradecanoylphorbol 13-acetate.
We have established a transgenic rat line carrying 3 copies of the human c-Ha-ras proto-oncogene with its own promoter region (Jcl/SD-TgN(HrasGen)128Ncc) (Hras128 rat), expression being detectable in almost all organs. We have already demonstrated that the rat is highly sensitive to mammary, esophagus and bladder carcinogenesis. In the present study, male and female transgenic and wild-type littermates were topically treated with 2.5 mg of 7,12-dimethylbenz[a]anthracene (DMBA) dissolved in 1.0 ml of acetone on the back skin at 50 days after birth. Starting 1 week thereafter, they were again topically treated with 100 nmol of 12-O-tetradecanoylphorbol 13-acetate (TPA) dissolved in 0.5 ml of acetone 3 times weekly for the following 31 weeks. In males treated with DMBA and/or TPA, skin tumors, including both squamous cell papillomas (SCP) and carcinomas (SCC), were preferentially induced at the DMBA-TPA painting sites: DMBA-TPA, 15/15 (100%); DMBA, 6/8 (75%); TPA, 1/6 (16.7%). They were also, unexpectedly, induced on remote scrotal skin: DMBA-TPA, 13/15 (86.7%); DMBA, 5/8 (62.5%); TPA, 0/6 (0%). Lesions were thus more frequent in the DMBA-TPA group than with DMBA or TPA alone. In females, adenomas and adenocarcinomas of the mammary glands were preferentially induced: DMBA-TPA, 12/14 (85.7%); DMBA, 6/8 (75%); TPA, 3/6 (50%), with only a few small skin papillomas at painting sites. Incidences and numbers of the mammary and skin tumors were much greater in Hras128 rats than in their wild-type counterparts. PCR-RFLP analysis of the transgene indicated that the percentage of the cell populations harboring a mutation in codons 12 and/or 61 ranged from 2% to 60% in individual tumors; skin tumors showed more mutations in codon 61 in the DMBA-treated groups. In contrast, no mutations were detected in the endogenous rat c-Ha-ras gene. These results indicate that the Hras128 rat is highly susceptible to DMBA-TPA skin and mammary carcinogenesis, thus providing a unique painting model for skin as well as mammary gland carcinogenesis, that would be suitable for investigating the role of transgene mutations.
Park
Cheol Beom
CB
Experimental Pathology and Chemotherapy Division, National Cancer Center Research Institute, 5-1-1 Tsukiji, Chuo-ku, Tokyo 104-0045, Japan.
Fukamachi
Katsumi
K
Takasuka
Nobuo
N
Han
Beom Seok
BS
Kim
Chuel Kyu
CK
Hamaguchi
Tetsuya
T
Fujita
Ken-ichi
K
Ueda
Shinobu
S
Tsuda
Hiroyuki
H
D000818:Animals; D030801:Animals, Genetically Modified; D001551:Benz(a)Anthracenes / Q000633:toxicity; D002273:Carcinogens / Q000633:toxicity; D005260:Female; D011905:Genes, ras / Q000235:genetics*; D006801:Humans; D008297:Male; D008325:Mammary Neoplasms, Experimental / Q000139:chemically induced / Q000235:genetics* / Q000473:pathology*; D009154:Mutation; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D000090063:Proto-Oncogene Mas; D051381:Rats; D012878:Skin Neoplasms / Q000139:chemically induced / Q000235:genetics* / Q000473:pathology*; D013755:Tetradecanoylphorbol Acetate / Q000633:toxicity
D001551:Benz(a)Anthracenes; D002273:Carcinogens; C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; C046810:7,12-dihydroxymethylbenz(a)anthracene; D013755:Tetradecanoylphorbol Acetate