Imatinib mesylate (STI571) abrogates the resistance to doxorubicin in human K562 chronic myeloid leukemia cells by inhibition of BCR/ABL kinase-mediated DNA repair.
ABSTRACT Imatinib mesylate (STI571), a specific inhibitor of BCR/ABL tyrosine kinase, exhibits potent antileukemic effects in the treatment of chronic myelogenous leukemia (CML). However, the precise mechanism by which inhibition of BCR/ABL activity results in pharmacological responses remains unknown. BCR/ABL-positive human K562 CML cells resistant to doxorubicin (K562DoxR) and their sensitive counterparts (K562DoxS) were used to determine the mechanism by which the STI571 inhibitor may overcome drug resistance. K562 wild type cells and CCRF-CEM lymphoblastic leukemia cells without BCR/ABL were used as controls. The STI571 specificity was examined by use of murine pro-B lymphoid Baf3 cells with or without BCR/ABL kinase expression. We examined kinetics of DNA repair after cell treatment with doxorubicin in the presence or absence of STI571 by the alkaline comet assay. The MTT assay was used to estimate resistance against doxorubicin and Western blot analysis with Crk-L antibody was performed to evaluate BCR/ABL kinase inhibition by STI571. We provide evidence that treatment of CML-derived BCR/ABL-expressing leukemia K562 cells with STI571 results in the inhibition of DNA repair and abrogation of the resistance of these cells to doxorubicin. We found that doxorubicin-resistant K562DoxR cells exhibited accelerated kinetics of DNA repair compared with doxorubicin-sensitive K562DoxS cells. Inhibition of BCR/ABL kinase in K562DoxR cells with 1 microM STI571 decreased the kinetics of DNA repair and abrogated drug resistance. The results suggest that STI571-mediated inhibition of BCR/ABL kinase activity can affect the effectiveness of the DNA-repair pathways, which in turn may enhance drug sensitivity of leukemia cells.
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ABSTRACT: BCR/ABL positive cells are known to be resistant to DNA damage induced by chemotherapy while they are sensitive to imatinib (IM), a tyrosine kinase inhibitor (TKI). To evaluate whether this drug can increase the activity of cytotoxic drugs on BCR/ABL positive cells, we measured the toxicity of cytosine arabinoside (ARA-C), hydroxyurea (HU) and melphalan (MEL), after a pretreatment of 24 h with IM on K562 cell line. The highest cytotoxic effect was seen when the TKI was followed by MEL; our results indicate that inhibition of BCR/ABL activity by IM increased the cytotoxicity of MEL by favoring the DNA damage induced by this drug and by shortening the time for DNA repair at the G2/M checkpoint. A stronger activation of some genes involved in both intrinsic and extrinsic apoptotic pathways was also observed with IM/MEL combination compared to IM or MEL alone. The drugs association was further tested in a type of BaF3 cells (TonB.210) where the BCR-ABL expression is inducible by doxycycline; in this model it was confirmed that a reduction of BCR/ABL activity resulted in an increased susceptibility to the cytotoxic effect of MEL. Furthermore, we studied the effect of IM/MEL treatment on the proliferative potential of myeloid progenitors of six CML patients at diagnosis. The analysis of CFU-GM and BFU-E colonies demonstrated that the IM/MEL combination was more effective than IM alone in reducing the overall number of colonies and the number of copies of BCR/ABL. In conclusion, our work shows that inhibition of BCR/ABL activity increases the toxicity of MEL and allows an efficient killing of leukemic cells, suggesting that a clinical development of this approach could have therapeutic advantages for CML patients.European Journal Of Haematology 03/2011; 86(3):216-25. DOI:10.1111/j.1600-0609.2010.01570.x · 2.41 Impact Factor
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ABSTRACT: The Philadelphia translocation t(9;22) resulting in the bcr/abl fusion gene is the pathogenic principle of almost 95% of human chronic myelogenous leukemia (CML). Imatinib mesylate (STI571) is a specific inhibitor of the BCR/ABL fusion tyrosine kinase that exhibits potent antileukemic effects in CML. BCR/ABL-positive K562 and -negative CCRF-CEM human leukemia cells were investigated. MTT survival assay and clonogenic test of the cell proliferation ability were used to estimate resistance against idarubicin. DNA damage after cell treatment with the drug at the concentrations from 0.001 to 3 microM with or without STI571 pre-treatment were examined by the alkaline comet assay. We found that the level of DNA damages was lower in K562 cells after STI571 pre-treatment. It is suggested that BCR/ABL activity may promote genomic instability, moreover K562 cells were found to be resistant to the drug treatment. Further, we provided evidence of apoptosis inhibition in BCR/ABL-positive cells using caspase-3 activity colorimetric assay and DAPI nuclear staining for chromatin condensation. We suggest that these processes associated with cell cycle arrest in G2/M checkpoint detected in K562 BCR/ABL-positive compared to CCRF-CEM cells without BCR/ABL expression might promote clone selection resistance to drug treatment.Comparative Biochemistry and Physiology Part C Toxicology & Pharmacology 10/2006; 144(1):85-92. DOI:10.1016/j.cbpc.2006.06.010 · 2.83 Impact Factor
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ABSTRACT: In this study, we have tried to find new targets and effective drugs for imatinib-resistant chronic myelogenous leukemia (CML) cells displaying loss of Bcr-Abl kinase target dependence. The imatinib-resistant K562/R1, -R2 and -R3 cells showed profound declines of Bcr-Abl level and concurrently exhibited up-regulation of Bcl-2 and Ku70/80, and down-regulation of Bax, DNA-PKcs and BRCA1, suggesting that loss of Bcr-Abl after exposure to imatinib might be accompanied by other cell survival mechanism. K562/R3 cells were more sensitive to camptothecin (CPT)- and radiation-induced apoptosis than K562 cells, indicating hypersensitivity of imatinib-resistant cells to DNA damaging agents. Moreover, when K562 cells were treated with the combination of imatinib with CPT, the level of Bax and the cleavage of PARP-1 and DNA-PK were significantly increased in comparison with the effects of each drug. Therefore, our study suggests that CPT can be used to treat CML with loss of Bcr-Abl expression.Cancer Letters 08/2007; 252(1):75-85. DOI:10.1016/j.canlet.2006.12.013 · 5.02 Impact Factor