Sister chromatid exchanges in vivo in mouse mammary adenocarcinoma

The proliferation and genetic characteristics of a mouse mammary adenocarcinoma designated dbrB are described. This tumor was maintained as subcutaneous serial transplants in syngeneic inbred mice of the DBA/1J strain. Quantitative in vivo sister chromatid exchange(s) (SCE) were determined in the tumor cells and in the bone marrow cells of the host strain. Over a twofold increase in SCE, frequency was noted in the dbrB tumor cells compared to the bone marrow cells. The high frequency of SCE in the dbrB tumor was assumed to be caused by the high degree of malignancy of this tumor. Such information indicating genetic stress may serve for evaluation of the degree of malignancy in neoplasms.