SYNERGISTIC AND ANTAGONISTIC EFFECTS OF MYELOID GROWTH-FACTORS ON IN-VITRO CELLULAR KILLING BY CYTOTOXIC DRUGS

The effect of stimulating acute myeloid leukemia blast cells with a co mbination of growth factors (G-CSF, GM-CSF, and IL-3) on cellular resi stance to the antileukemia drugs Ara-C, daunorubicin, aclarubicin, and mitoxantrone was studied. For assessment of in vitro cellular drug re sistance the MTT assay was employed. Stimulated cells showed enhanced sensitivity to Ara-C (p < 0.02), whereas a significant increase in cel lular drug resistance to daunorubicin (p < 0.02) was observed. Variabl e and statistically non-significant changes in drug resistance to acla rubicin and mitoxantrone was induced by stimulation of the blast cells . We conclude on the basis of these observations that myeloid growth f actors should be used with caution in combination with daunorubicin in AML treatment until further confirmatory evidence has been presented by other investigators.