TAXOL-ENHANCED CYTOTOXIC EFFECT OF RADIATION IN HUMAN PROMYELOCYTIC LEUKEMIA-CELLS - RELATIVE RESISTANCE OF MULTIDRUG-RESISTANT HL-60 CELLSIN-VITRO

Cytotoxic effects of sequential taxol (paclitaxel) and X-irradiation o n drug-sensitive human cultured promyelocytic leukemia (HL-60) cell li ne and its multidrug-resistant sublines were examined using photometri c MTT test and flow cytometry. Paclitaxel (at concentrations 1-10 nmol ) stimulated the cytotoxic effect of irradiation in HL-60 and to a les ser extent also in HL-60/ADR, but not in HL-60/VCR cells. The stimulat ion of radiation-induced cytotoxic effect by paclitaxel correlated wit h its potential to induce cell cycle and viability alterations identif ied with flow cytometric analysis (i.e. increased propidium iodide sta ining, increased side scatter, decreased forward angle scatter, accumu lation of necrotic cell detritus, apoptotic pre-G(0) cells and cells i n the G(2)/M phase of the cell cycle).