• BMB Reports
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• v.56 no.2
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• pp.78-83
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• 2023

Chronic myeloid leukemia (CML) has a markedly improved prognosis with the use of breakpoint cluster region-abelson 1 (BCR-ABL1) tyrosine kinase inhibitors (BCR-ABL1 TKIs). However, approximately 40% of patients are resistant or intolerant to BCR-ABL1 TKIs. Hypoxia-inducible factor 1α (HIF-1α) is a hypoxia response factor that has been reported to be highly expressed in CML patients, making it a therapeutic target for BCR-ABL1 TKI-sensitive CML and BCR-ABL1 TKI-resistant CML. In this study, we examined whether HIF-1α inhibitors induce cell death in CML cells and BCR-ABL1 TKI-resistant CML cells. We found that echinomycin and PX-478 induced cell death in BCR-ABL1 TKIs sensitive and resistant CML cells at similar concentrations while the cell sensitivity was not affected with imatinib or dasatinib in BCR-ABL1 TKIs resistant CML cells. In addition, echinomycin and PX-478 inhibited the c-Jun N-terminal kinase (JNK), Akt, and extracellular-regulated protein kinase 1/2 (ERK1/2) activation via suppression of BCR-ABL1 and Met expression in BCR-ABL1 sensitive and resistant CML cells. Moreover, treatment with HIF-1α siRNA induced cell death by inhibiting BCR-ABL1 and Met expression and activation of JNK, Akt, and ERK1/2 in BCR-ABL1 TKIs sensitive and resistant CML cells. These results indicated that HIF-1α regulates BCR-ABL and Met expression and is involved in cell survival in CML cells, suggesting that HIF-1α inhibitors induce cell death in BCR-ABL1 TKIs sensitive and resistant CML cells and therefore HIF-1α inhibitors are potential candidates for CML treatment.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.22
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• pp.9961-9966
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• 2014

Background: Some reports have suggested that chronic myeloid leukemia (CML) patients have a higher prevalence of M-bcr than acute lymphoblastic leukemia (ALL) patients, which show a higher prevalence of m-bcr. However, the relationship between BCR-ABL subtypes and progression of CML and ALL remains unclear. Materials and Methods: 354 CML chronic phase (CML-CP) patients, 26 CML blastic phase (CML-BP) patients and 72 ALL patients before treatment with BCR-ABL positive were recruited for blood routine examination and bone marrow smear cytology. Some 80 CML-CP and 32 ALL patients after imatinib (IM) treatment were followed-up for BCR-ABL relative concentrations detected after treatment for 3, 6 and 9 months and 1 year. Results: Before treatment, CML-CP patients showed lower BCR-ABL relative concentrations with a higher proportion of M-bcr (42.7%) compared to CML-BP and ALL patients while ALL patients had a higher BCR-ABL relative concentration with high expression of m-bcr (51.4%). Patients with M-bcr demonstrated higher WBC counts than those with m-bcr and the mixed group and higher PLT counts were noted in the CML-CP and ALL groups. After imatinib (IM) treatment, patients with m-bcr showed higher BCR-ABL relative concentrations in both CML-CP and ALL groups. Conclusions: This study identified the BCR-ABL gene as an important factor in CML and ALL cases. The M-bcr subtype was associated more with CML while the m-bcr subtype was associated more with ALL. Patients with m-bcr seem to have a poorer response to IM in either CML or ALL patients compared to M-bcr patients.

• BMB Reports
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• v.29 no.3
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• pp.241-247
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• 1996

The Philadelphia (Ph) chromosome is the single most intensively studied chromosome alteration characterizing a human malignancy. The specific genetic alteration of chronic myelogenous leukemia (CML) is the formation of the BCR/abl fusion gene in leukemic cells. The presence of the BCR/abl gene has important diagnostic and prognostic implications in CML. The detection of BCR/abl transcripts by reverse transcriptase based polymerase chain reaction (RT-PCR) was investigated in patients with CML in whom the Ph chromosome abnormality was documented by cytogenetic analysis. In a total of 68 CML patient cases, the Ph chromosome was found in 53 cases (77.9%) by cytogenetic analysis. On the other hand, sixty two cases (91.2%) were detected to have BCR/abl gene rearrangement Of these, b3a2 was 44 cases (64.7%) and b2a2 was 17 cases (25,0%). There was one case with both b3a2 and b2a2 (1.5%). Of the fifteen cases of Ph chromosome negative by cytogenetic anlaysis, the BCR/abl gene was observed in nine cases, The results of BCR/abl fusion gene confirmed by the direct sequencing method correlated well with PCR analysis, The amplified PCR products were detected by $1{\times}10^{-5}$ dilutions. In conclusion, PCR technique is sensitive, rapid and relatively simple for a laboratory test in detecting the BCR/abl fusion gene with CML regardless of the result of cytogenetic analysis.

• Molecules and Cells
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• v.39 no.12
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• pp.869-876
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• 2016

Cantharidin (CTD) is an active compound isolated from the traditional Chinese medicine blister beetle and displayed anticancer properties against various types of cancer cells. However, little is known about its effect on human chronic myeloid leukemia (CML) cells, including imatinib-resistant CML cells. The objective of this study was to investigate whether CTD could overcome imatinib resistance in imatinib-resistant CML cells and to explore the possible underlying mechanisms associated with the effect. Our results showed that CTD strongly inhibited the growth of both imatinib-sensitive and imatinib-resistant CML cells. CTD induced cell cycle arrest at mitotic phase and triggered DNA damage in CML cells. The ATM/ATR inhibitor CGK733 abrogated CTD-induced mitotic arrest but promoted the cytotoxic effects of CTD. In addition, we demonstrated that CTD downregulated the expression of the BCR-ABL protein and suppressed its downstream signal transduction. Real-time quantitative PCR revealed that CTD inhibited BCR-ABL at transcriptional level. Knockdown of BCR-ABL increased the cell-killing effects of CTD in K562 cells. These findings indicated that CTD overcomes imatinib resistance through depletion of BCR-ABL. Taken together, CTD is an important new candidate agent for CML therapy.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.11
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• pp.4857-4861
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• 2016

Background: Imatinib mesylate, a tyrosine kinase inhibitor specifically targeting the BCR/ABL fusion protein, induces hematological remission in patients with chronic myeloid leukemia (CML). However, the majority of CML patients treated with imatinib develop resistance with prolonged therapy. Dendrophthoe pentandra (L.) Miq. is a Malaysian mistletoe species that has been used as a traditional treatment for several ailments such as smallpox, ulcers, and cancers. Methods: We developed a resistant cell line (designated as K562R) by long-term co-culture of a BCR/ABL positive CML cell line, K562, with imatinib mesylate. We then investigated the anti-proliferative effects of D. pentandra methanol extract on parental K562 and resistant K562R cells. Trypan blue exclusion assays were performed to determine the IC50 concentration; apoptosis and cell cycle analysis were conducted by flow cytometry. Results: D. pentandra extract had greater anti-proliferative effects towards K562R ($IC50=192{\mu}g/mL$) compared to K562 ($500{\mu}g/mL$) cells. Upon treatment with D. pentandra extract at the IC50. concentration: K562 but not K562R demonstrated increase in apoptosis and cell cycle arrest in the G2/M phase. Conclusion: D. pentandra methanol extract exerts potent anti-proliferative effect on BCR/ABL positive K562 cells.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.13
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• pp.5273-5278
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• 2015

Background: Chronic myeloid leukemia (CML) is a stem cell disorder characterized by the fusion of two oncogenes namely BCR and ABL with their aberrant expression. Autophosphorylation of BCR-ABL oncogenes results in proliferation of CML. The study deals with estimation of rate constant involved in each step of the cellular autophosphorylation process, which are consequently playing important roles in the proliferation of cancerous cells. Materials and Methods: A mathematical model was proposed for autophosphorylation of BCR-ABL oncogenes utilizing ordinary differential equations to enumerate the rate of change of each responsible system component. The major difficulty to model this process is the lack of experimental data, which are needed to estimate unknown model parameters. Initial concentration data of each substrate and product for BCR-ABL systems were collected from the reported literature. All parameters were optimized through time interval simulation using the fminsearch algorithm. Results: The rate of change versus time was estimated to indicate the role of each state variable that are crucial for the systems. The time wise change in concentration of substrate shows the convergence of each parameter in autophosphorylation process. Conclusions: The role of each constituent parameter and their relative time dependent variations in autophosphorylation process could be inferred.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.7
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• pp.3025-3033
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• 2016

Chronic myeloid leukaemia (CML) is a clonal myeloproliferative hematopoietic stem cell disorder. Deregulated BCR-ABL fusion tyrosine kinase activity is the main cause of CML disease pathogenesis, making BCR-ABL an ideal target for inhibition. Current tyrosine kinase inhibitors (TKIs) designed to inhibit BCR-ABL oncoprotein activity, have completely transformed the prognosis of CML. Interruption of TKI treatment leads to minimal residual disease reside (MRD), thought to reside in TKI-insensitive leukaemia stem cells which remain a potential reservoir for disease relapse. This highlights the need to develop new therapeutic strategies for CML either as small molecule master TKIs or phytopharmaceuticals derived from nature to achieve chronic molecular remission. This review outlines the past, present and future therapeutic approaches for CML including coverage of relevant mechanisms, whether ABL dependent or independent, and epigenetic factors responsible for developing resistance against TKIs. Appearance of mutant clones along the course of therapy either pre-existing or induced due to therapy is still a challenge for the clinician. A proposed in-vitro model of generating colony forming units from CML stem cells derived from diagnostic samples seems to be achievable in the era of high throughput technology which can take care of single cell genomic profiling.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.12
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• pp.4773-4780
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• 2014

Background: To investigate the effects of small interference RNA (siRNA) targeting BCR/ABL mRNA on proliferation and apoptosis in the K562 human chronic myeloid leukemia (CML) cell line and to provide a theoretical rationale and experimental evidence for its potential clinical application for anti-CML treatment. Materials and Methods: The gene sequence for BCR/ABL mRNA was found from the GeneBank. The target gene site on the BCR/ABL mRNA were selected according to Max-Planck-Institute (MPI) and rational siRNA design rules, the secondary structure of the candidate targeted mRNA was predicted, the relevant thermodynamic parameters were analyzed, and the targeted gene sequences were compared with BLAST to eliminate any sequences with significant homology. Inhibition of proliferation was evaluated by MTT assay and colony-formation inhibiting test. Apoptosis was determined by flow cytometry (FCM) and the morphology of apoptotic cells was identified by Giemsa-Wright staining. Western blotting was used to analyze the expression of BCR/ABL fusion protein in K562 cells after siRNA treatment. Results: The mRNA local secondary structure calculated by RNA structure software, and the optimal design of specific siRNA were contributed by bioinformatics rules. Five sequences of BCR/ABL siRNAs were designed and synthesized in vitro. Three sequences, siRNA1384, siRNA1276 and siRNA1786, which showed the most effective inhibition of K562 cell growth, were identified among the five candidate siRNAs, with a cell proliferative inhibitory rate nearly 50% after exposure to 12.5nmol/L~50nmol/L siRNA1384 for 24,48 and 72 hours. The 50% inhibitory concentrations ($IC_{50}$) of siRNA1384, siRNA1276 and siRNA1786 for 24hours were 46.6 nmol/L, 59.3 nmol/L and 62.6 nmol/L, respectively, and 65.668 nmol/L, 76.6 nmol/L, 74.4 nmol/L for 72 hours. The colony-formation inhibiting test also indicated that, compared with control, cell growth of siRNA treated group was inhibited. FCM results showed that the rate of cell apoptosis increased 24 hours after transfecting siRNA. The results of annexinV/PI staining indicated that the rate of apoptosis imcreased (1.53%, 15.3%, 64.5%, 57.5% and 21.5%) following treamtne with siRNAs (siRNA34, siRNA372, siRNA1384, siRNA1276 and siRNA1786). Morphological analysis showed td typical morphologic changes of apoptosis such as shrunken, fragmentation nucleus as well as "apoptotic bodies" after K562 cell exposure to siRNA. Western blot analysis showed that BCR/ABL protein was reduced sharply after a single dose of 50nmol/L siRNA transfection. Conclusions: Proliferation of K562 cells was remarkbly inhibited by siRNAs (siRNA1384, siRNA1276 and siRNA1786) in a concentration-dependent manner in vitro, with effective induction of apoptosis at a concentration of 50 nmol/L. One anti-leukemia mechanism in K562 cells appeared that BCR/ABL targeted protein was highly down-regulated. The siRNAs (siRNA1384, siRNA1276 and siRNA1786) may prove valuable in the treatment of CML.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.11
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• pp.4555-4561
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• 2014

Background: Silencing due to methylation of suppressor of cytokine signaling-3 (SOCS-3), a negative regulator gene for the JAK/STAT signaling pathway has been reported to play important roles in leukemogenesis. Imatinib mesylate is a tyrosine kinase inhibitor that specifically targets the BCR-ABL protein and induces hematological remission in patients with chronic myeloid leukemia (CML). Unfortunately, the majority of CML patients treated with imatinib develop resistance under prolonged therapy. We here investigated the methylation profile of SOCS-3 gene and its downstream effects in a BCR-ABL positive CML cells resistant to imatinib. 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 $IC_{50}$ 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 $IC_{50}$ for imatinib on K562 was 362nM compared to 3,952nM 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.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.17
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• pp.7415-7423
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• 2015

Chronic myeloid leukemia (CML) is a stem cell disorder characterized by unrestricted proliferation of the myeloid series that occurs due to the BCR-ABL fusion oncogene as a result of reciprocal translocation t(9;22) (q34;q11). This discovery has made this particular domain a target for future efforts to cure CML. Imatinib revolutionized the treatment options for CML and gave encouraging results both in case of safety as well as tolerability profile as compared to agents such as hydroxyurea or busulfan given before Imatinib. However, about 2-4% of patients show resistance and mutations have been found to be one of the reasons for its development. European Leukemianet gives recommendations for BCR-ABL mutational analysis along with other tyrosine kinase inhibitors (TKIs) that should be administered according to the mutations harbored in a patient. The following overview gives recommendations for monitoring patients on the basis of their mutational status.