The influence of a new antitumor agent on hemopoietic colony forming cells.

The cytostatic and immunsuppressive agent N'-methyl-N'-beta-chloroethylbenzaldehyde hydrazone (B1) in in-vitro experiments has a stimulating effect on colony-forming culture (CFUc) of bone marrow from C57BL mice. This unusual behaviour, which is in contrast to other cytostatics, could also be observed in vitro with CFUc obtained from mice treated with therapeutic doses of B1 for 2 weeks. This stimulation is not a particular effect of B1 alone but seems to depend on a synergistic effect of the combination of B1 and the colony-stimulating activity (CSA) present in the serum from endotoxin-treated mice (MP) in the testing system. The results suggest that the described effect of B1 is due to an interference at the cell membrane of CFUc or their precursor cells.