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.
- [Show abstract] [Hide abstract]
ABSTRACT: It is a well-acclaimed fact that proteins expressed as a consequence of oncogenic fusions, mutations or amplifications can facilitate ectopic protein-protein interactions that re-wire signal dissemination pathways, in a manner that escalates malignancy. BCR-ABL-mediated signal transduction cascades in leukemic cells are assembled and modulated by a finely controlled network of protein-protein interactions, mediated by characteristic signaling domains and their respective binding motifs. BCR-ABL functions in a cell context-specific and cell type-specific manner to integrate signals that affect uncontrolled cellular proliferation. In this review, we draw attention to the recent progress made in outlining resistance against TRAIL-mediated apoptosis and diametrically opposed roles of miRNAs in BCR-ABL-positive leukemic cells. BCR-ABL governs carcinogenesis through well-organized web of antiapoptotic proteins and over-expressed oncomirs which target death receptors and pro-apoptotic genes. Set of oncomirs which inversely correlate with expression of TRAIL via suppression of SMAD is an important dimension which is gradually gaining attention of the researchers. Contrary to this, some current findings show a new role of BCR-ABL in nucleus with spotlight on apoptosis. It seems obvious that genetic heterogeneity of leukemias poses therapeutic challenges, and pharmacological agents that target components of the cancer promoting nano-machinery still need broad experimental validation to be considered competent as a component of the therapeutic arsenal for this group of diseases. Rapidly developing technologies are empowering us to explain the molecular "nature" of a patient and/or tumor and with this integration of personalized medicine, with maximized efficacy, cost effectiveness will hopefully improve survival chances of the patient.Archivum Immunologiae et Therapiae Experimentalis 12/2012; · 2.38 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Despite rapid progress in anticancer drug development and improvement in clinical outcomes, the survival rate for many types of cancer is still unacceptably low. Therefore, it is crucial to discover novel anticancer drugs to both prevent and treat the disease. In recent years, the advent of combinatorial chemistry allows the design and parallel synthesis of millions of small compounds that have drug-like properties. In vitro high throughput screening of such compound libraries has allowed the identification of many new drug candidates that may be further evaluated for their efficacy and mechanism of action. The overall objective of this study was to identify small molecule compounds as candidates for anti-cancer drug development. We first used cell proliferation and cytotoxicity assays to identify compounds exhibiting anti-cancer activity in vitro in a leukemia cell line (K562). Six top compounds selected from the initial screening of a library of 2,560 compounds were further evaluated in multiple cancer cell lines to rank the drug candidates. The top candidate was further investigated to elucidate the molecular mechanism underlying its anticancer activity. Our studies suggest that this piperazine derivative effectively (GI50 = 0.06-0.16 μM) inhibits cancer cell proliferation and induces caspase-dependent apoptosis via inhibiting multiple cancer signaling pathways including the PI3K/AKT, the Src family kinases and the BCR-ABL pathways.American Journal of Translational Research 01/2013; 5(6):622-633.
- [Show abstract] [Hide abstract]
ABSTRACT: PURPOSE: Pre-clinical data suggest that combining imatinib with traditional cytotoxic chemotherapy may improve imatinib efficacy. We conducted a Phase I study of imatinib in combination with paclitaxel in patients with advanced or metastatic solid tumors. METHODS: Patients were accrued to the study in a standard 3 + 3 design. Patients were restaged every two cycles, and those with stable disease (SD), or better, continued study treatment without interruption. Maximally tolerated doses (MTDs) and pharmacokinetic profiles of combination imatinib and paclitaxel were assessed. RESULTS: Fifty-eight patients were enrolled, including 40 in the Phase I dose escalation portion. Alternating dose escalation of imatinib and paclitaxel on a 28-day cycle resulted in MTDs of 800 mg imatinib daily, on days 1-4, 8-11, 15-18, and 22-25, and 100 mg/m(2) paclitaxel weekly, on days 3, 10, and 17. Two expansion cohorts, comprising 10 breast cancer patients and 8 patients with soft-tissue sarcomas, were enrolled at the MTDs. The most common adverse events were flu-like symptoms (64 %) and nausea/vomiting (71 %). The most common Grade 3/4 toxicities were neutropenia (26 %), flu-like symptoms (12 %), and pain (12 %). There were no relevant differences in the pharmacokinetic profiles of either drug when given in combination compared with alone. Thirty-eight subjects were evaluable for response, 18 (47.4 %) of whom experienced clinical benefit. Five patients (13.2 %) had a partial response (PR) and 13 patients (34.2 %) had SD; the average time to progression in those with clinical benefit was 17 weeks (range: 7-28 weeks). CONCLUSIONS: This combination of imatinib and paclitaxel was reasonably safe and tolerable, and demonstrated evidence of anti-tumor activity. Further exploration in disease-specific Phase II trials is warranted.Cancer Chemotherapy and Pharmacology 09/2012; · 2.80 Impact Factor