RT Journal Article SR Electronic T1 The Synergistic Inhibitory Effect of STI571 in Combination with Arsenic Trioxide (AS2O3) on Multidrug-Resistant Leukemic Cells JF Chinese Journal of Clinical Oncology JO Cancer Biol Med FD China Anti-Cancer Association SP 671 OP 674 VO 2 IS 3 A1 Li Chen A1 Jianmin Wang A1 Xiaoping Xu A1 Lei Gao A1 Xinhong Fei A1 Jingwei Lou A1 Zhengxia Huang YR 2005 UL http://www.cancerbiomed.org/content/2/3/671.abstract AB OBJECTIVE To study the synergistic effect of STI571, an inhibitor of tyrosine kinase, in combination with arsenic trioxide As2O3 on a multidrug-resistant leukemia cell line expressing bcr-abl.METHODS The cytotoxic effect of STI571 alone or in combination with different concentrations of As2O3 on the bcr-abl and mdr1-positive leukemia cell line, K562-n/VCR, was examined by the MTT method.RESULTS One μmol/L of STI571 alone had no significant cytotoxic effect on K562-n/VCR cells. However the cytotoxic effect increased markedly when combined with As2O3 at concentrations of 10-5, 10-6, 10-7 and 10-8 mol/L. The IC50 of K562-n/VCR cells in As2O3 group was 1.879 mol/L, with Upon addition of STI571, the IC50 decreased to 0.155 μmol/L resulting in a synergistic cytotoxic effect on K562-n/VCR cells that was increased 12.1 times.CONCLUSION A combination of STI571 with As2O3 has a more powerful inhibitory effect on leukemia cells expressing positive bcr-abl and positive mdrl compared to the effect with As2O3 alone.