Comparative potency of the mammary tumour agent of mice of different genetic constitution.

PREVIOUS experiments (Dmochowski, 1944a) have shown that dried breast tumour tissue of the R III strain of mice gives rise to breast cancer in C57 x Strong A hybrid mice. It also induces a high incidence of breast cancer in the same hybrid mice after preliminary transmission through two other strains of mice, viz.: S x R III and S. Thus it is clear that the mammary tumour agent of a high cancer strain of mice can induce breast cancer in susceptible mice of an entirely different genetic constitution from that of the strain from which the agent originated. In extension of these observations the present experiments were undertaken to ascertain whether the mammary tumour agent from other high cancer strains of mice can give rise to breast cancer in susceptible mice which differ in their genetic constitutions from that of the strains from which the mammary tumour agent was obtained.