Carcinogenesis Advance Access published online on October 11, 2005
Carcinogenesis, doi:10.1093/carcin/bgi241
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1 Department of Oncologic Pathology, Kanazawa Medical University, 1-1 Daigaku, Uchinada, Ishikawa 920-0293, Japan; A Research fellow of the Japan Society for the Promotion of Science, 6 Ichiban-cho, Chiyoda-ku, Tokyo 102-8471, Japan
* To whom correspondence should be addressed. Oral squamous cell carcinoma is one of the most common human neoplasms, and prevention of this malignancy requires a better understanding of its carcinogenesis process. For this end, we tried to establish an animal model using the human c-Ha-ras proto-oncogene-carrying transgenic (Tg) rats and the carcinogen 4-nitroquinoline 1-oxide (4-NQO). 4-NQO (20 ppm) was administered to Tg and non-Tg rats for 8 weeks in their drinking water, and then the occurrence of tongue carcinogenesis was compared during the experimental period of 22 weeks. In addition, we determined the DNA ploidy in tongue lesions, and examined the immunohistochemical expression of five biomarkers, such as cyclin D1, glutathione S-transferase placental form, cyclooxygenase (COX)-2, inducible nitric oxide synthase (iNOS), and
Received July 4, 2005
Revised September 11, 2005
Accepted September 30, 2005
CARCINOGENESIS
An animal model for the rapid induction of tongue neoplasms in human c-Ha-ras proto-oncogene transgenic rats by 4-nitroquinoline 1-oxide: its potential use for preclinical chemoprevention studies
2 Department of Oncologic Pathology, Kanazawa Medical University, 1-1 Daigaku, Uchinada, Ishikawa 920-0293, Japan
3 Tumor Pathology, University of the Ryukyu Faculty of Medicine, 207 Uehara Nishihara-cho, Okinawa 903-0215, Japan
4 Department of Molecular Toxicology, Nagoya City University, Graduate School of Medical Sciences, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467-8601, Japan
5 Cancer Prevention Basic Research Project, National Cancer Research Institute, 5-1-1 Tsukiji, Chuo-ku, Tokyo 104-0045, Japan
Takuji Tanaka, E-mail: takutt{at}kanazawa-med.ac.jp
Abstract 
-catenin. Next, using Tg rats, the cancer chemopreventive effects of nimesulide, pioglitazone, and a synthetic geranylated derivative, which have been reported to be inhibitors of tongue carcinogenesis, were examined in Tg rats treated with 4-NQO. Either during or after treatment with 4-NQO in the drinking water, tongue dysplasia and tumors were observed on the tongues of both Tg and non-Tg rats, with a greater incidence and multiplicity in Tg rats. Histopathologically, squamous cell dysplasia, papilloma, and carcinoma with or without invasion were present in the tongue. Immunohistochemistry revealed that expression levels against five biomarkers increase with disease progression, and the changes correlated with those of the DNA ploidy pattern. Interestingly, a strong expression of COX-2, iNOS, and -catenin was observed on the invasive front of squamous cell carcinomas. A subsequent chemoprevention study using Tg rats showed that the chemicals tested suppressed the occurrence of tongue carcinomas when they were administered after 4-NQO-exposure. These results may thus indicate that our 4-NQO-induced Tg rat tongue carcinogenesis model simulates many aspects of human oral carcinogenesis and it can be applied for an analysis of oral cancer development while also helping to identify potentially effective cancer chemopreventive agents against oral cancer.
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