e18543 Background: Chronic myeloid leukemia (CML) is characterized by the Bcr-Abl genetic translocation which leads to constitutive tyrosine kinase signaling. Treatment with tyrosine kinase inhibitors as imatinib eliminates CML cells, but resistance often occurs. No specific molecular risk factors or imatinib-resistance predictors have been validated so far, thus the aim of this study was to determine genetic factors that would allow for a better management of this disease. Methods: An age and gender matched case-control study of 57 CML patients and 63 healthy controls was performed. In vitro experiments were performed on K562 cells and an imatinib-resistant K562R cell line. CML patients were treated with imatinib and stratified into responders (complete molecular response after three months, CMR) and non-responders. RNA was isolated from blood leukocytes or cells and used for cDNA synthesis. Gene expression levels were evaluated by real-time PCR and the results analyzed using the delta-delta-Ct method. Differences in expression levels and their prognostic/predictive potentials were evaluated by t-test, linear regression analysis and receiver operating characteristics curve, with statistical significance set at p < 0.05. Results: In CML patients, the Bcl2 and IGF-1R mRNA expression level were higher than in controls (1.03 ± 0.06 vs. 0.92 ± 0.18, p < 0.0001; 1.14 ± 0.15 vs. 1.03 ± 0.15, p = 0.0001, respectively). Prior to treatment, the Bcl2 mRNA levels were lower for the K562 than for the resistant K562R cell line (1.13±0.04 vs. 1.62±0.01, p < 0.0001), and the same was observed for IGF-1R (1.22±0.01 vs. 1.29±0.01, p = 0.001). Patients who achieved a CMR after imatinib treatment had significantly lower pre-treatment levels of Bcl-2 and IGF-1R (0.99 ± 0.05 vs. 1.04 ± 0.06, p = 0.005; 1.12 ± 0.02 vs. 1.15 ± 0.04, p = 0.0123, respectively) compared to patients who did not achieve a CMR, which confirmed the in vitro observed data. Conclusions: High levels of Bcl-2 and IGF-1R mRNA were detected in CML patients, and the analysis of their expression might be used as a low-cost CML screening tool. Successful imatinib treatment was correlated with significantly lower pre-treatment Bcl-2 and IGF-1R levels in vitro and in vivo, which might also be used as a low-cost molecular predictor of a favorable clinical response .
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