目的　研究酪氨酸激酶抑制剂STI5 71与三氧化二砷 (As2 O3 )联合应用对多药耐药bcr abl阳性白血病细胞的协同效应。方法　采用MTT法比较STI5 71单独或与不同浓度的As2 O3 联合应用对bcr abl和mdr1共同阳性的白血病细胞系K5 6 2 n/VCR的抑制作用。结果　 1μmol/L的STI5 71对K5 6 2 n/VCR细胞无明显细胞毒作用 ,与 10 -5,10 -6,10 -7,10 -8mol/L的As2 O3 联合应用 ,细胞毒作用明显增强。As2 O3 单独对K5 6 2 n/VCR细胞的IC50 为 1.879μmol/L ,加STI5 71后 ,IC50 为 0 .15 5 μmol/L ,协同抑制作用为 12 .12倍。结论　STI5 71与As2 O3 联合应用对于bcr abl与mdr1共同阳性的白血病细胞有更强的抑制作用 Objective To investigate the synergistic effect of STI5 71, a tyrosine kinase inhibitor, and arsenic trioxide (As2 O3) on multidrug resistant bcr abl positive leukemia cells. Methods MTT assay was used to compare the inhibitory effect of STI571 alone or in combination with different concentrations of As2 O3 on K562 n / VCR in both bcr abl and mdr1-positive leukemia cell lines. Results STI571 (1μmol / L) had no obvious cytotoxic effect on K562 / nCR cells, and cytotoxicity was significantly enhanced when treated with 10-5,10-6,10-7,10-8mol / L As2 O3 . As2 O3 alone had an IC50 of 1.879 μmol / L for K5 6 2 n / VCR cells and an IC50 of 0.155 μmol / L for STI5 71 with a synergistic inhibitory effect of 12.12-fold. Conclusion The combination of STI5 71 and As2 O3 has a stronger inhibitory effect on bcr abl and mdr1-positive leukemia cells