MATERIALS AND METHODS: BCR-ABL positive CML cells resistant to imatinib (K562-R) were developed by overexposure of K562 cell lines to the drug. Cytotoxicity was determined by MTS assays and IC50 values calculated. Apoptosis assays were performed using annexin V-FITC binding assays and analyzed by flow cytometry. Methylation profiles were investigated using methylation specific PCR and sequencing analysis of SOCS-1 and SOCS-3 genes. Gene expression was assessed by quantitative real-time PCR, and protein expression and phosphorylation of STAT1, 2 and 3 were examined by Western blotting.
RESULTS: The IC50 for imatinib on K562 was 362 nM compared to 3,952 nM for K562-R (p=0.001). Percentage of apoptotic cells in K562 increased upto 50% by increasing the concentration of imatinib, in contrast to only 20% in K562-R (p<0.001). A change from non-methylation of the SOCS-3 gene in K562 to complete methylation in K562-R was observed. Gene expression revealed down- regulation of both SOCS-1 and SOCS-3 genes in resistant cells. STAT3 was phosphorylated in K562-R but not K562.
CONCLUSIONS: Development of cells resistant to imatinib is feasible by overexposure of the drug to the cells. Activation of STAT3 protein leads to uncontrolled cell proliferation in imatinib resistant BCR-ABL due to DNA methylation of the SOCS-3 gene. Thus SOCS-3 provides a suitable candidate for mechanisms underlying the development of imatinib resistant in CML patients.
METHODS: This is a retrospective study, which included 93 CML patients and 98 controls. The polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) method was used to genotype the FAS and FASL polymorphisms. Data nanlysis was done using SPSS Version 22. The associations of the genotypes with susceptibility risk and IM response in CML patients were assessed by means of logistic regression analysis and deriving odds ratio with 95% CI.
RESULTS: We observed a significant association between FASL-844T>C polymorphism and CML susceptibility risk and IM response. Variant C allele and FASL-844 CC variant genotype carriers had significantly higher risk for CML susceptibility (OR 1.756, CI 1.163-2.652, p=0.007 and OR 2.261, CI 1.013-5.047, p=0.047 respectively). Conversely, the heterozygous genotype FASL-844 TC conferred lower risk for CML susceptibility (OR 0.379, CI 0.176-0.816, p=0.013). The heterozygous and homozygous variant genotypes and variant C alleles were found to confer a lower risk for the development of IM resistance with OR 0.129 (95% CI: 0.034-0.489 p=0.003), OR 0.257 (95% CI: 0.081-0.818, p=0.021), and OR 0.486 (95% CI: 0.262-0.899, p=0.021) respectively. We also found that FAS-670 A>G polymorphism was not associated with CML susceptibility risk or IM response.
CONCLUSION: The genetic polymorphism FASL-844 T>C may contribute to the CML susceptibility risk and also IM treatment response in CML patients. Accodringly, it may be useful as a biomarker for predicting CML susceptibility risk and IM resistance.
METHODS: BCR-ABL positive K562 CML cells were treated with TQ. Cytotoxicity was determined by Trypan blue exclusion assay. Apoptosis assay was performed by annexin V-FITC/PI staining assay and analyzed by flow cytometry. Transcription levels of BCR ABL, JAK2, STAT3, STAT5A and STAT5B genes were evaluated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Protein levels of JAK2 and STAT5 were determined by Jess Assay analysis.
RESULTS: TQ markedly decreased the cell proliferation and induced apoptosis in K562 cells (P < 0.001) in a concentration dependent manner. TQ caused a significant decrease in the transcriptional levels of BCR ABL, JAK2, STAT3, STAT5A and STAT5B genes (P < 0.001). TQ induced a significant decrease in JAK2 and STAT5 protein levels (P < 0.001).
CONCLUSION: our results indicated that TQ inhibited cell growth of K562 cells via downregulation of BCR ABL/ JAK2/STAT3 and STAT5 signaling and reducing JAK2 and STAT5 protein levels.
AIM: To investigate the correlation of HOXA4 and HOXA5 promoter DNA hypermethylation with imatinib resistance among CML patients.
METHODS AND RESULTS: Samples from 175 Philadelphia positive CML patients (83 good response and 92 BCR-ABL non-mutated imatinib resistant patients) were subjected to Methylation Specific High Resolution Melt Analysis for methylation levels quantification of the HOXA4 and HOXA5 promoter regions. Receiver operating characteristic curve analysis was done to elucidate the optimal methylation cut-off point followed by multiple logistic regression analysis. Log-Rank analysis was done to measure the overall survival difference between CML groups. The optimal methylation cut-off point was found to be at 62.5% for both HOXA4 and HOXA5. Chronic myeloid leukemia patients with ≥63% HOXA4 and HOXA5 methylation level were shown to have 3.78 and 3.95 times the odds, respectively, to acquire resistance to imatinib. However, overall survival of CML patients that have ≤62% and ≥ 63% methylation levels of HOXA4 and HOXA5 genes were found to be not significant (P-value = 0.126 for HOXA4; P-value = 0.217 for HOXA5).
CONCLUSION: Hypermethylation of the HOXA4 and HOXA5 promoter is correlated with imatinib resistance and with further investigation, it could be a potential epigenetic biomarker in supplement to the BCR-ABL gene mutation in predicting imatinib treatment response among CML patients but could not be considered as a prognostic marker.