Methylcholanthrene-induced neoplasms in germ-free RFM mice.

Abstract

AbstractFive‐ to six‐week‐old germ‐free RFM mice treated orally three times a week with 0.1 ml of 0.8% solution of 20‐methylcholanthrene in olive oil developed a high incidence of thymic lymphoma but no myeloid leukemia. On the other hand, 11% of males painted on the abdomen twice a week with a 5% solution of croton oil in benzene and receiving the same oral methylcholanthrene treatment developed myeloid leukemia. Methylcholanthrene with or without the croton oil in benzene treatment increased the incidence of pulmonary adenomas, but papillomas of the skin and stomach and squamous cell carcinomas of the skin were seen only in mice treated with both methylcholanthrene and croton oil in benzene. The croton oil in benzene acted as a co‐carcinogen for the induction of papillomas of the skin and stomach and squamous cell carcinomas of the skin, but not for pulmonary adenomas or thymic lymphomas. Methylcholanthrene induction of myeloid leukemia in mice painted with croton oil in benzene gives further evidence of the relationship between granulocytopoiesis and induction of myeloid leukemia.