Historical Background Data in CB6F1-Tg-rasH2 Mice and CB6F1-nonTg-rasH2 Mice over a 26-Week Experimental Period

Abstract

CB6F1-TgHras2 mice (rasH2 mice) are considered to be a promising model for short-term carcinogenicity studies. This study was conducted to obtain background data for rasH2 mice, and the data were compared with those for CB6F1-nonTgHras2 mice (nonTg mice). This study revealed that the survival ratio of rasH2 mice was 92% for males and 97% for females and the body weights were lower than those of nonTg mice while plasma AST and ALT levels in rasH2 males were higher than those in nonTg males. On histopathology, higher incidences of the following neoplastic lesions were observed in rasH2 mice: hemangiosarcoma in the spleen, bronchiolo-alveolar adenoma/carcinoma in the lung in both sexes, hepatocellular adenoma in the liver, squamous cell papilloma in the forestomach, and adenocarcinoma in the Harderian glands in males. For non-neoplastic lesions in rasH2 mice, the incidences of dilatation of the glands in the glandular stomach, inflammatory cell infiltration in the submucosa of the glandular stomach, myopathy of the tongue and skeletal muscle, eosinophilic bodies in the respiratory epithelium of the nasal cavity, and basophilic renal tubules in the kidney were higher than those in nonTg mice for both sexes. In this study, various tumors and characteristic non-neoplastic lesions were observed in the rasH2 mice; furthermore, the incidence of hepatocelluler adenoma was higher than that in previous reports. These findings will be useful when evaluating the short-term carcinogenicity study using rasH2 mice.