Bone marrow stromal cells attenuate mitoxantrone cytotoxicity against HL-60 leukemic cells.

We evaluated the effect of cultured human bone marrow (BM) stromal cells on the cytotoxicity of mitoxantrone (MIT) against the HL-60 leukemic cell line. BM-derived fibroblastoid cells (BMFC) suppressed colony formation of HL-60 cells in the absence of MIT. BMFC increased the survival of HL-60 colony-forming cells in the presence of 50 ng/ml MIT. A significant decrease in the drug concentration was not detected on BMFC. Our results suggest that BM stromal cells can modulate the antileukemic effect of an anticancer drug.