• Biomolecules & Therapeutics
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• 제25권5호
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• pp.490-496
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• 2017

Imatinib resistance has become a major clinical problem for chronic myeloid leukemia. The aim of the present study was to investigate the involvement of MEG3, a lncRNA, in imatinib resistance and demonstrate its underlying mechanisms. RNAs were extracted from CML patients' peripheral blood cells and human leukemic K562 cells, and the expression of MEG3 was measured by RT-qPCR. Cell proliferation and cell apoptosis were evaluated. Western blotting was used to measure the protein expression of several multidrug resistant transporters. Luciferase reporter assay was performed to determine the binding between MEG3 and miR-21. Our results showed that MEG3 was significantly decreased in imatinib-resistant CML patients and imatinib-resistant K562 cells. Overexpression of MEG3 in imatinib-resistant K562 cells markedly decreased cell proliferation, increased cell apoptosis, reversed imatinib resistance, and reduced the expression of MRP1, MDR1, and ABCG2. Interestingly, MEG3 binds to miR-21. MEG3 and miR-21 were negatively correlated in CML patients. In addition, miR-21 mimics reversed the phenotype of MEG3-overexpression in imatinib-resistant K562 cells. Taken together, MEG3 is involved in imatinib resistance in CML and possibly contributes to imatinib resistance through regulating miR-21, and subsequent cell proliferation, apoptosis and expression of multidrug resistant transporters.

• Molecules and Cells
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• 제39권12호
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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.

• 생명과학회지
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• 제30권8호
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• pp.661-671
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• 2020

항암 요법의 실패의 주요 원인으로 암세포의 항암제에 대한 내성 획득이 잘 알려져 있다. 비스테로이드소염제(NSAID)는 항염증작용뿐만 아니라 항암제와의 병용요법으로 임상적인 암 치료 요법에 응용되고있다. 본 연구에서는 NSAIDs 인 celecoxib 및 이의 구조 유사체인 2,5-dimethyl celecoxib 그리고 ibuprofen의 인간 암세포에 대한 imatinib 및 TNF-related apoptosis inducing ligand (TRAIL) 세포 독성 변화에 미치는 영향을 조사하였다. NSAID는 TRAIL 및 imatinib에 각각 약제 내성을 나타내는 간암 세포와 백혈병 세포에서 이들 약물의 세포독성을 증강시키는 활성을 나타내었다. NSAID는 ATF4/CHOP의 발현 증강으로 소포체 스트레스 및 오토파지(Autophagy, 자가포식)를 유도하였다. 이로 인한 DR5 발현 증강과 함께 c-FLIP 발현 억제로 TRAIL의 세포독성을 증강시키는 기전을 나타내었다. NSAID로 유도되는 오토파지 활성은 imatinib-resistant CD44^highK562 백혈병세포의 imatinib 감수성을 증강시켰으며, NSAID는 이 세포에서 높은 발현을 나타내는 다양한 stemness-related marker 단백질의 발현 감소를 촉진시키는 활성으로 세포사멸을 유도하는 것을 알 수 있었다. 이러한 결과는 NSAID의 오토파지 유도 활성이 TRAIL과 imatinib의 세포 독성을 증강시키는 것으로서, NSAID와 이들 약물과 병용 처리방법은 인간 암세포의 TRAIL 및 imatinib 내성을 극복 시킴과 동시에 암세포에 이들 약물의 독성 부작용을 감소시킬 수 있는 낮은 농도의 처리를 가능하게 할 것으로 사료된다.

• BMB Reports
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• 제38권6호
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• pp.725-738
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• 2005

Resistance to imatinib mesylate (also known as Gleevec, Glivec, and STI571) often becomes a barrier to the treatment of chronic myelogenous leukemia (CML). In order to identify markers of the action of imatinib mesylate, we used a mass spectrometry approach to compare protein expression profiles in human leukemia cells (K562) and in imatinib mesylate-resistant human leukemia cells (K562-R) in the presence and absence of imatinib mesylate. We identified 118 differentially regulated proteins in these two leukemia cell-lines, with and without a $1\;{\mu}M$ imatinib mesylate challenge. Nine proteins of unknown function were discovered. This is the first comprehensive report regarding differential protein expression in imatinib mesylate-treated CML cells.

• 대한의생명과학회지
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• 제24권4호
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• pp.426-429
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• 2018

Chronic eosinophilic leukemia (CEL) is characterized by eosinophilia and organ damage. Imatinib is widely used for treating CEL, chronic myeloid leukemia (CML) and acute myeloid leukemia (AML). Unfortunately, the cancer cells gain resistance against the drug after prolonged molecular-targeted therapies. Imatinib-resistant EoL-1 (EoL-1-IR) cells were produced from chronic eosinophilic leukemia cells (EoL-1) after treatment with imatinib for a long duration. Two-dimensional electrophoresis (2-DE) analysis revealed numerous protein variations in the EoL-1 and EoL-1-IR sub-types. Compared to the EoL-1 cells, expression levels of TIP49, RBBP7, ${\alpha}$-enolase, adenosine deaminase, C protein, galactokinase, eukaryotic translation initiation factor, $IFN-{\gamma}$, and human protein homologous to DROER were increased, whereas core I protein, proteasome subunit p42, heterogeneous ribonuclear particle protein, chain B, and nucleoside diphosphate were decreased in the EoL-1-IR cells. Taken together, these results contribute to understanding the pathogenic mechanism of drug-resistant diseases.

• Clinical and Experimental Pediatrics
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• 제54권3호
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• pp.111-116
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• 2011

Childhood chronic myelogenous leukemia (CML) is a rare hematologic disease, with limited literature on the methods of treatment. Previously, allogeneic hematopoietic stem cell transplantation (HSCT) was considered the only curative treatment for this disease. Treatment with imatinib, a selective inhibitor of the BCR-ABL tyrosine kinase (TKI), has resulted in prolonged molecular response with limited drug toxicity. Imatinib is now implemented in the primary treatment regimen for children, but the paucity of evidence on its ability to result in permanent cure and the potential complications that may arise from long-term treatment with TKIs have prevented imatinib from superseding HSCT as the primary means of curative treatment in children. The results of allogeneic HSCT in children with CML are similar to those observed in adults; HSCT-related complications such as transplant-related mortality and graft-versus-host disease remain significant challenges. An overall consensus has been formed with regards to the need for HSCT in patients with imatinib resistance or those with advanced-phase disease. However, issues such as when to undertake HSCT in chronic-phase CML patients or how best to treat patients who have relapsed after HSCT are still controversial. The imatinib era calls for a reevaluation of the role of HSCT in the treatment of CML. Specific guidelines for the treatment of pediatric CML have not yet been formulated, underscoring the importance of prospective studies on issues such as duration of imatinib treatment, optimal timing of HSCT and the type of conditioning utilized, possible treatment pre-and post-HSCT, and the role of second-generation TKIs.

• Asian Pacific Journal of Cancer Prevention
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• 제15권11호
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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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• 제17권11호
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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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• 제15권4호
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• pp.1863-1869
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• 2014

The amplification of telomerase component (TERC) gene could play an important role in generation and treatment of haematological malignancies. This present study was aimed to investigate copy number amplification status of TERC gene in chronic myeloid leukaemia (CML) patients who were being treated with imatinib mesylate (IM). Genomic DNA was extracted from peripheral blood of CML-IM Resistant (n=63), CML-IM Respond (n=63) and healthy individuals (n=30). TERC gene copy number predicted (CNP) and copy number calculated (CNC) were determined based on $Taqman^{(R)}$ Copy Number Assay. Fluorescence in situ hybridization (FISH) analysis was performed to confirm the normal signal pattern in C4 (calibrator) for TERC gene. Nine of CML patients showed TERC gene amplification (CNP=3), others had 2 CNP. A total of 17 CML patients expressed CNC>2.31 and the rest had 2.31>CNC>1.5. TERC gene CNP value in healthy individuals was 2 and their CNC value showed in range 1.59-2.31. The average CNC TERC gene copy number was 2.07, 1.99 and 1.94 in CML-IM Resistant patients, CML-IM Respond and healthy groups, respectively. No significant difference of TERC gene amplification observed between CML-IM Resistant and CML-IM Respond patients. Low levels of TERC gene amplification might not have a huge impact in haematological disorders especially in terms of resistance towards IM treatment.

• 생명과학회지
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• 제23권2호
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• pp.197-206
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• 2013

본 연구에서는 K562 만성 골수성 백혈병 세포를 이용하여, 분화 유도에 의해 암 유지/개시 세포의 자기 재생능력이 소실되는 지를 조사하였다. K562 세포의 집락(colony) 형성 능력은 PMA 처리에 의하여 현저히 억제되었고, 1 nM 이상의 PMA 처리시에는 집락이 형성되지 않았으나, 약 40%의 세포는 여전히 연한천(soft agar)에서 살아 있었다. PMA 4 nM을 3일간 처리하고 제거한 후 분리한 집락 형성 세포에 다시 10 nM PMA를 3일간 처리하였을 때, 약 70% 정도의 세포가 분화되었고, 6주 후에 PMA를 처리하였을 때는 분화율이 약 90%로 K562 모세포에 PMA를 처리한 수준에 도달하였다. 한편, imatinib-내성 K562 변종 세포들은 연한천에서 집락을 형성하지 않았으며, 대부분의 세포가 CD44 양성이었다. Imatinib 무첨가 배지에서 4개월 배양 후, 이 세포들의 표면 CD44발현량은 감소하였고, K562/R3 imatinib-내성 변종 세포에서는 연한천에서 작은 집락이 형성되었다. 이 세포에서는 imatinib-내성 변종 세포에서 소실되었던 Bcr-Abl이 다시 발현되기 시작하였고, 다른 표현형들도 부분적으로 회복되었다. 이러한 결과는 백혈병 유지 세포가 분화에 내성을 나타내는 세포이며, 분화 유도제를 오랜 기간 동안 고농도로 처리할 수 있다면 백혈병 줄기 세포를 제거하기 위한 분화 요법이 백혈병 치료에 적용될 수 있음을 시사하였다.