The effect of etoposide on human CFU-GM

Etoposide is being used increasingly in the treatment of a variety of malignant conditions and in conjunction with autologous bone marrow transplantation. We have examined the effect of the drug on human CFU-GM as an indication of the response of these bone marrow progenitor cells to measured plasma concentrations. When etoposide is present in the routine assay for 7 days, 50% growth of colony-forming CFU-GM occurs at a concentration of 0.0098 micrograms ml-1. When bovine serum albumin or human serum albumin is present this value is increased to 0.042 and 0.375 micrograms ml-1. Protein binding therefore plays an important part in modifying in vitro response and possibly in vivo response of these progenitor cells to etoposide.