Evaluation of the wap-ras transgenic mouse as a model system for testing anticancer drugs.

Transgenic mouse models have provided many valuable insights into the molecular mechanisms of tumorigenesis; unfortunately, there is a paucity of published information on the utility of these models for evaluating potential anticancer therapeutics. Line 69 wap-ras transgenic mice have an activated, human c-Ha-ras gene on their Y chromosome. Adult males develop salivary and/or mammary adenocarcinomas. Both tumor types express high levels of human ras oncoprotein. Two new sublines, designated wap-ras/F, were created by selective breeding. Subline 69-2 wap-ras/F males developed multiple mammary tumors at puberty. Tumor onset was delayed by cyclophosphamide treatment prior to puberty. Mammary tumors from cyclophosphamide-treated mice weighed 0.57 +/- 0.09 g/mouse (SD +/- SEM; n = 8), while tumors from control mice weighed significantly more at 2.36 +/- 0.25 g/mouse (n = 8; P less than or equal to 0.001; SD +/- SEM). These results suggest that subline 69-2F mice will be valuable for testing therapeutic regimes designed to interfere with processes occurring early in tumorigenesis, before palpable tumor presentation. Tumor sensitivity to several clinically relevant cytotoxins was also tested in adult wap-ras males with palpable tumors. Both salivary and mammary tumors were sensitive to cyclophosphamide and 5-fluorouracil, but not methotrexate. This suggests that wap-ras transgenic mice will indeed be useful in the discovery of novel therapeutics against neoplasia.