CPT-11-induced cell death in leukemic cells is not affected by the MDR phenotype.

CPT-11 is a topoisomerase I (Topo I) inhibitor which was initially described as active in multi-drug resistance (MDR) tumors. The MDR phenomenon is characterized by the overexpression of efflux pumps which are able to extrude a range of drugs non-related chemical or functionally. In this work, we treated leukemic cells with CPT-11 300 microM at 24h and compared its cytotoxicity with the activity of efflux pumps and with cell cycle phase. Our findings show that CPT-11 has a potent anti-tumor activity in leukemic cells regardless MDR phenotype and the cell cycle phase, suggesting new avenues to be explored in leukemia treatment.