Studies on Leukemia Development in the SJL/J Strain of Mice

Summary

Spontaneous reticulum cell neoplasms developed in 70–80% of intact male and female SJL/J mice at a mean age of 380 days. The neoplasms had a basic histological paHern of a multicellular type-B reticulum cell neoplasm, as designated by Dunn. The tumors were transplanted in isogenic mice. Serial passages of cell suspensions of these tumors were carried on through at least 4 tumor-inducing generations, and the growing transplanted tumors maintained the structure of a reticulum cell neoplasm similar to the original tumor. A histological survey of spontaneous lesions in SJL/J mice revealed different characteristics of reticulum cell neoplasms, some similar to Hodgkin' s lesions. Five or ten feedings of 7,12-dimethylbenz[a]anthracene (DMBA) in polyethylene glycol 400 (1 mg DMBA per feeding) to SJL/J mice induced lymphosarcomas in 74–83% of the mice at a mean age of 157–188 days. A single feeding of DMBA induced lymphosarcomas in only 27% of the mice at a mean age of 246 days. These DMBA-induced lymphatic leukemias do not appear to depend on the thymus for development—a 60% incidence of lymphosarcomas was obtained in adult thymectomized mice treated with DMBA, and 27% of the thymectomized DMBA-treated mice developed myeloid leukemia at a mean age of 180 days. Urethan was only slightly leukemogenic in SJL/J mice.