Differential sensitivity of colony-forming cells of hemopoietic tissue, Lewis lung carcinoma, and B16 melanoma to three nitrosoureas.

A comparison has been made of the effects of three nitrosoureas (BCNU, CCNU, and methyl-CCNU) on the cells of Lewis lung carcinoma and B16 melanoma in vivo using a new in vitro method for assaying colony-forming cells. In addition, the effect on early hemopoietic precursors has been studied using the in vivo spleen colony assay and the in vitro agar colony assay. The results show that the three nitrosoureas are selective against Lewis lung carcinoma and B16 melanoma relative to normal hemopoietic precursors. Furthermore, the effect of these nitrosoureas is unchanged when the rate of proliferation of the hemopoietic precursor cells is increased.