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

Abstract

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. (Cancer Sci 2004; 95: 205-210) arious transgenic and knockout mice have proven to be good animal models for analysis of gene functions. In the chemical carcinogenesis field, transgenic mice carrying human c-Ha-ras proto-oncogenes (rasH2 mice) have been shown to be highly susceptible to induction of skin, lung and lymphatic cell tumors by various carcinogens.1-6) However, rats are more frequently used for analysis of events occurring during tumor development. There are thus many more basic experimental data available for rats than mice regarding chemical carcinogenesis, and a variety of preneoplastic lesions, including hepatocellular enzyme-altered foci, for example, are available in rats as surrogate markers for cancer development. 7,8) Furthermore, mammary cancers in rats can be induced without the complication of a viral etiology irrelevant to the disease in man. So far, only limited types of transgenic rats have been de...

Enhancement of tongue carcinogenesis in Hras128 transgenic rats treated with 4-nitroquinoline 1-oxide

“…These results clearly show that Hras128 rats are more sensitive to 4NQO induced tongue carcinogenesis than SD rats. This susceptibility to a carcinogen is in accordance with previous experiments demonstrating that Hras128 rats are more sensitive to a 7,12-dimethylbenz[a]anthracene (DMBA) or 4NQO in the mammary or tongue tumors than were wild-type SD rats (11,21). In addition, Miyamoto et al demonstrated that the rasH2 mouse carcinogenesis model is highly susceptible to 4NQO induced tongue and esophageal tumors (12).…”

Possible enhancing effects of atrazine and nonylphenol on 7,12‐dimethylbenz[a]anthracene‐induced mammary tumor development in human c‐Ha‐ras proto‐oncogene transgenic rats

“…61) In the present study, atrazine and nonylphenol inhibited development of DMBA-induced skin tumors in male Tg rats, in line with earlier data for estradiol. 36) In Tg rats, feminization by endocrine disruptors may thus play a role in reducing the skin tumors, which do not develop in females.…”

“…36) We recently showed that the transgenic (Tg) rats have a potential for use in medium-term bioassay models to test for the modifying effects of estrogenic environmental compounds on mammary tumor development. 37) In the present study, they were employed to investigate potential modifying effects of atrazine and nonylphenol on DMBA mammary and skin carcinogenesis.…”

“…The animals have also been found to be susceptible to N-butyl-N-(4-hydroxybutyl)nitrosamine urinary bladder, 34) N-nitrosomethylbenzylamine esophageal, 35) and DMBA skin carcinogenesis. 36) We recently showed that the transgenic (Tg) rats have a potential for use in medium-term bioassay models to test for the modifying effects of estrogenic environmental compounds on mammary tumor development. 37) In the present study, they were employed to investigate potential modifying effects of atrazine and nonylphenol on DMBA mammary and skin carcinogenesis.…”

Bin3 Deletion Causes Cataracts and Increased Susceptibility to Lymphoma during Aging

“…Mice treated with DEN were monitored up to an end point of 12 mo, after which all animals were euthanized and examined at necropsy for evidence of tumor formation. For skin carcinogenesis, mice were shaved and the dorsal epidermis was treated essentially as described (30,31) with a single dose of 400 nmol 7,12-dimethylbenz(a)anthracene (DMBA) followed by a twice-weekly application of 17 nmol phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA). Mice treated with DMBA + TPA were monitored to a 20-wk end point for skin tumors.…”