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: 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.
MATERIALS AND METHODS: Two leukemic cell lines, MV4-11 (acute myeloid leukemia) and K562 (chronic myeloid leukemia), were studied. IC50 concentrations were determined and apoptosis and cell cycle regulation were studied by flow cytometric analysis. The expression of apoptosis and cell-cycle related regulatory proteins was assessed by Western blotting.
RESULTS: P sacharosa inhibited growth of MV4-11 and K562 cells in a dose-dependent manner. The mode of cell death was via induction of intrinsic apoptotic pathways and cell cycle arrest. There was profound up-regulation of cytochrome c, caspases, p21 and p53 expression and repression of Akt and Bcl-2 expression in treated cells.
CONCLUSIONS: These results suggest that P sacharosa induces leukemic cell death via apoptosis induction and changes in cell cycle checkpoint, thus deserves further study for anti-leukemic potential.
APPROACH: This study was carried out to evaluate the cytotoxicity of triphenyltin(lV) methylisopropyldithiocarbamate (compound 1) and triphenyltin(IV) ethylisopropyldithiocarbamate (compound (2) on chronic myelogenus leukemia cells. The determination of their cytotoxicity (IC50) at different time of exposure and concentration was carried out through the employment of 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl-tetrazolium bromide (MTT) assay.
RESULTS: The IC50 values obtained for compound 1 and 2 following treatment at 24, 48 and 72 h were 0.660, 0.223, 0.370 microM and 0.677, 0.306, 0.360 microM, respectively. Cell morphological changes such as apoptotic and necrotic features were also been observed.
CONCLUSION: The compounds tested were found to give cytotoxic effect against chronic myelogenus leukemia (K-562) cell at a micromolar dose. Thus, further study on their specific mechanism of actions in the human cells should be carried out to elucidate their potential as an anticancer agent.
METHODS: MTT assay was performed to evaluate the cytotoxic effects of both compounds toward the cells after 24, 48 and 72 hours of exposure or treatment. The alkaline comet assay was conducted to determine the DNA damage on K562 cells after been exposed to both compounds for 30, 60 and 90 minutes.
RESULTS: The IC50 values obtained from K562 cells ranged from 0.01 to 0.30 μM, whereas for both Chang liver cell and lung fibroblast V79 cell, the values ranged from 0.10 to 0.40 μM. For genotoxicity evaluation, the percentage of damaged DNA is measured as an average of tail moment, and was found to be within 1.20 to 2.20 A.U while the percentage of DNA intensity ranging from 1.50 to 3.50% indicating no genotoxic effects.
CONCLUSION: Both compounds are cytotoxic toward leukemia cells and non-cancerous cells but do not exert their genotoxic effects towards leukemia cell.
METHODS: Transfection of ANXA1 siRNA was conducted to downregulate ANXA1 expression in Jurkat, K562 and U937 cells. Apoptosis and cell cycle assays were conducted using flow cytometry. Western blot was performed to evaluate ANXA1, caspases and Bcl-2 proteins expression. Phagocytosis was determined using hematoxylin and eosin staining.
RESULTS: The expression of ANXA1 after the knockdown was significantly downregulated in all cell lines. Genistein significantly induced apoptosis associated with an upregulation of procaspase-3, -9, and - 1 in Jurkat cells. The Bcl-2 expression showed no significant difference in Jurkat, K562 and U937 cells. Treatment with phytoestrogens increased procaspase-1 expression in Jurkat and U937 cells while no changes were detected in K562 cells. Flow cytometry analysis demonstrated that after ANXA1 knockdown, coumestrol and genistein caused cell cycle arrest at G2/M phase in selected type of cells. The percentage of phagocytosis and phagocytosis index increased after the treatment with phytoestrogens in all cell lines.
CONCLUSION: Phytoestrogens induced cell death in ANXA1-knockdown leukemia cells, mediated by Annexin A1 proteins. Graphical abstract.