Breakpoint Cluster region-Abelson Murine Leukemia Research Articles

The role of long noncoding RNA HOTAIR in the acquired multidrug resistance to imatinib in chronic myeloid leukemia cells

ABSTRACTObjectives: Imatinib, a breakpoint cluster region-Abelson murine leukemia tyrosine kinase inhibitor, has revolutionized the treatment of chronic myelogenous leukemia (CML). However, the development of multidrug resistance (MDR) limits the clinical application of imatinib. In this study, we aimed to investigate the mechanisms of long noncoding RNA (lncRNA) HOTAIR in CML resistance to imatinib.Methods: Thirty-four CML patients were divided into multidrug resistance protein 1 (MRP1)-low and MRP1-high groups according to the median expression. Real-time PCR (qPCR) was used to detect the expression of lncRNA HOTAIR in CML patients, and MTT assay and flow cytometry assay were employed to detect the biological function of silencing lncRNA HOTAIR on the cell survival rate and apoptotic rate. An imatinib-resistant human CML cell line K562 (K562-R) was established, and western blot was used to detect the impact of lncRNA HOTAIR on the activation of PI3K/Akt signaling pathway.Results: Our results showed that lncRNA HOTAIR was greatly upregulated in the MRP1-high patients as well as in the K562-imatinib-resistant cells compared with control. Knockdown of HOTAIR expression downregulated the MRP1 expression levels in the K562-imatinib cells and resulted in higher sensitivity to the imatinib treatment. In addition, the activation of PI3K/Akt was greatly attenuated when HOTAIR was knocked down in K562-imatinib cells.Discussions: These data suggest that the knockdown of HOTAIR may play a crucial role in improving acquired resistance to imatinib in CML K562-R cells via PI3K/Akt pathway.Conclusions: LncRNA HOTAIR modulates CML cell MDR in a PI3K/Akt-dependent way.

Role of the bone morphogenic protein pathway in developmental haemopoiesis and leukaemogenesis.

Myeloid leukaemias share the common characteristics of being stem cell-derived clonal diseases, characterised by excessive proliferation of one or more myeloid lineage. Chronic myeloid leukaemia (CML) arises from a genetic alteration in a normal haemopoietic stem cell (HSC) giving rise to a leukaemic stem cell (LSC) within the bone marrow (BM) 'niche'. CML is characterised by the presence of the oncogenic tyrosine kinase fusion protein breakpoint cluster region-abelson murine leukaemia viral oncogene homolog 1 (BCR-ABL), which is responsible for driving the disease through activation of downstream signal transduction pathways. Recent evidence from our group and others indicates that important regulatory networks involved in establishing primitive and definitive haemopoiesis during development are reactivated in myeloid leukaemia, giving rise to an LSC population with altered self-renewal and differentiation properties. In this review, we explore the role the bone morphogenic protein (BMP) signalling plays in stem cell pluripotency, developmental haemopoiesis, HSC maintenance and the implication of altered BMP signalling on LSC persistence in the BM niche. Overall, we emphasise how the BMP and Wnt pathways converge to alter the Cdx-Hox axis and the implications of this in the pathogenesis of myeloid malignancies.

Illegitimate RAG-mediated recombination events are involved in IKZF1 Δ3-6 deletion in BCR-ABL1 lymphoblastic leukaemia.

Breakpoint cluster region-Abelson murine leukaemia viral oncogene homologue 1 (BCR-ABL1), encoded by the Philadelphia (Ph) chromosome, is the characteristic of chronic myeloid leukaemia (CML) and a subset of acute lymphoblastic leukaemia (ALL). We demonstrated that expression of the Ik6 transcript, which lacked exons 3-6, was observed exclusively in BCR-ABL1(+) B ALL and lymphoid blast crisis CML (BC-CML) patients harbouring the IKZF1 Δ3-6 deletion. To confirm the hypothesis that illegitimate recombination activating gene protein (RAG)-mediated recombination events are involved in IKZF1 Δ3-6 deletion in BCR-ABL1 lymphoblastic leukaemia, we first demonstrated that the expression rates of RAG1 and RAG2, collectively called RAG, were higher in ALL and BC-CML (lymphoid). Notably, analysis of relationships among RAG, BCR-ABL1 and Ikaros 6 (Ik6) showed that Ik6 can be generated only if RAG and BCR-ABL1 are co-existing. The sequencing data showed that the deleted segments of introns 2 and 6 contained cryptic recombination signal sequences (cRSSs) and frequently had non-template nucleotides inserted between breakpoints. Furthermore, we used chromatin immunoprecipitation (ChIP) technology and demonstrated that the sequences directly flanking IKZF1 Δ3-6 deletion breakpoints have significantly higher levels of histone H3 lysine 4 trimethylation (H3K4me3) modifications. Overall, RAG expression, good-quality cRSS and a specific chromatin modification, H3K4me3, satisfy the conditions of RAG's off-target effects on IKZF1. Our work provides evidence for RAG-mediated IKZF1 Δ3-6 deletion. Our results raise the prospect that RAG is a valuable biomarker in disease surveillance. Dissecting the contribution of RAG should not only provide valuable mechanistic insights, but will also lead to a new therapeutic direction.

Wilms’ tumour antigen 1 Immunity via DNA fusion gene vaccination in haematological malignancies by intramuscular injection followed by intramuscular electroporation: a Phase II non-randomised clinical trial (WIN)

BackgroundIn the UK almost 7000 people are diagnosed with leukaemia each year, but despite continuing advances in diagnosis and treatment with new drugs, such as the tyrosine kinase inhibitors, the majority of these patients will eventually die from their disease. Until quite recently, the only treatment to offer the possibility of long-term disease-free survival was allogeneic stem cell transplantation. However, this carries a substantial risk of mortality and is available to only a minority of patients.ObjectivesThe aim of the study was to test the hypothesis that molecular and clinical responses, induced by T lymphocytes (T cells), can be predicted by increases in the number of CD8+ (cluster of differentiation 8-positive) T cells specific for the vaccine-encoded T-cell epitopes. This project also aimed to build on the established programme of deoxyribonucleic acid (DNA) fusion-gene vaccination delivered by intramuscular injection, exploiting a unique experience with electroporation, to induce durable immune responses with the aim of controlling disease by precision attack of the tumour by CD8+ T cells.MethodA non-randomised, open-label, single-dose-level Phase II clinical trial in two patient groups [chronic myeloid leukaemia (CML) and acute myeloid leukaemia (AML)] on stable doses of imatinib. Human leucocyte antigen A2-positive (HLA A2+) patients were vaccinated with two DNA vaccines: (1) p.DOM–WT1-37 (epitope sequence: VLDFAPPGA); and (2) p.DOM–WT1-126 (epitope sequence: RMFPNAPYL). The HLA A2-negative patients formed an unvaccinated control group. The sample size for the HLA A2+ group was originally determined following Simon’s optimal Phase II trial design (Simon R. Optimal two-stage designs for phase II clinical trials.Control Clin Trials1989;10:1–10). This was changed to A’Hern’s single-stage design during the course of the trial (A’Hern RP. Sample size tables for single-stage phase II designs.Stat Med2001;20:859–66), which was endorsed by the trial’s independent oversight committees.ResultsThe study included 12 patients with CML who were vaccinated and nine patients with CML who were unvaccinated as the control group. Both the vaccines and the electroporation were safe, with no new or unexpected toxicities. The evaluation adverse events of special interest (heart, bone marrow, renal) did not reveal safety concerns. TwoBCR–ABL(breakpoint cluster region–Abelson murine leukaemia viral oncogene homolog 1) responses were observed, both of which were defined as a major response, with one in each group. Two Wilms’ tumour antigen 1 (WT1) molecular responses were observed in the vaccinated group and one was observed in the control group. At an immunological level, the vaccine performed as expected.ConclusionsThe study met its primary decision-making target with one major molecular response inBCR–ABLtranscript levels. Overall, the data showed, in this clinical setting, the immunogenicity and safety of the vaccine.LimitationsThe study did not complete recruitment and there were multiple hurdles that contributed to this failure. This is disappointing given the robust induction immune responses againstWT1T-cell responses in 7 out of 10 evaluable patients.Future workEvaluation of the p.DOM–WT1 vaccines in AML remains attractive clinically, but it is unlikely to be feasible at this time. Combination of the DNA vaccine approach with strategies to expand T-cell responses with immunomodulatory antibodies is in development.Funding detailsThis project was funded by the Efficacy and Mechanism Evaluation (EME) programme, a Medical Research Council (MRC) and National Institute for Health Research (NIHR) partnership, and Bloodwise.

The pan-inhibitor of Aurora kinases danusertib induces apoptosis and autophagy and suppresses epithelial-to-mesenchymal transition in human breast cancer cells.

Danusertib (Danu) is a pan-inhibitor of Aurora kinases and a third-generation breakpoint cluster region-Abelson murine leukemia viral oncogene homolog 1 (Bcr-Abl) tyrosine kinase inhibitor, but its antitumor effect and underlying mechanisms in the treatment of human breast cancer remain elusive. This study aimed to investigate the effects of Danu on the growth, apoptosis, autophagy, and epithelial-to-mesenchymal transition (EMT) and the molecular mechanisms in human breast cancer MCF7 and MDA-MB-231 cells. The results demonstrated that Danu remarkably inhibited cell proliferation, induced apoptosis and autophagy, and suppressed EMT in both breast cancer cell lines. Danu arrested MCF7 and MDA-MB-231 cells in G2/M phase, accompanied by the downregulation of cyclin-dependent kinase 1 and cyclin B1 and upregulation of p21 Waf1/Cip1, p27 Kip1, and p53. Danu significantly decreased the expression of B-cell lymphoma-extra-large (Bcl-xl) and B-cell lymphoma 2 (Bcl-2), but increased the expression of Bcl-2-associated X protein (Bax) and p53-upregulated modulator of apoptosis (PUMA), and promoted the cleavage of caspases 3 and 9. Furthermore, Danu significantly increased the expression levels of the membrane-bound microtubule-associated protein 1A/1B-light chain 3 (LC3-II) and beclin 1 in breast cancer cells, two markers for autophagy. Danu induced the activation of p38 mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinases 1 and 2 (Erk1/2) and inhibited the activation of protein kinase B (Akt)/mammalian target of rapamycin (mTOR) signaling pathways in breast cancer cells. Treatment with wortmannin (a phosphatidylinositol 3-kinase inhibitor) markedly inhibited Danu-induced activation of p38 MAPK and conversion of cytosolic LC3-I to membrane-bound LC3-II. Pharmacological inhibition and small interfering RNA-mediated knockdown of p38 MAPK suppressed Akt activation, resulting in LC3-II accumulation and enhanced autophagy. Pharmacological inhibition and small interfering RNA-mediated knockdown of Erk1/2 also remarkably increased the level of LC3-II in MCF7 cells. Moreover, Danu inhibited EMT in both MCF7 and MDA-MB-231 cells with upregulated E-cadherin and zona occludens protein 1 (ZO-1) but downregulated N-cadherin, zinc finger E-box-binding homeobox 1 (TCF8/ZEB1), snail, slug, vimentin, and β-catenin. Notably, Danu showed lower cytotoxicity toward normal breast epithelial MCF10A cells. These findings indicate that Danu promotes cellular apoptosis and autophagy but inhibits EMT in human breast cancer cells via modulation of p38 MAPK/Erk1/2/Akt/mTOR signaling pathways. Danu may represent a promising anticancer agent for breast cancer treatment. More studies are warranted to fully delineate the underlying mechanisms, efficacy, and safety of Danu in breast cancer therapy.

Extramedullary T-lymphoblastic blast crisis in chronic myelogenous leukemia: A case report of successful diagnosis and treatment.

Extramedullary T-lymphoblastic blast crisis of chronic myelogenous leukemia (CML) is uncommon and the prognosis is poor. It was usually misdiagnosed as the co-existence of T-lymphoblastic lymphoma (T-LBL) and CML. In the present study, we report a patient with CML, who developed extramedullary T-lymphoblastic blast crisis and was successfully treated with human leukocyte antigen (HLA)-mismatched stem cell transplantation. The patient was a 44-year-old man who presented with lymphadenectasis and leucocytosis prior to diagnosis. The bone marrow smear, biopsy and fluorescence in situ hybridization (FISH) of Breakpoint Cluster Region/ Abelson murine leukaemia (BCR/ABL) supported the diagnosis of CML in the chronic phase, while the immunohistochemistry of lymph nodes supported the diagnosis of T-LBL. The FISH test for BCR/ABL in lymph node blast cells was performed and the result was positive; therefore, the patient was diagnosed with extramedullary T-lymphoblastic blast crisis of CML. After several courses of combined chemotherapy, the patient was treated with HLA-mismatched stem cell transplantation and obtained continuous remission for 51 months until the present (September 2013).

A case of chronic myeloid leukemia with the m-bcr (p190) molecular rearrangement identified during treatment

Chronic myeloid leukemia (CML) is a hematological malignancy in which a high percentage of patients cytogenetically express the Philadelphia chromosome. This chromosome results from the reciprocal translocation, t(9;22)(q34;q11.2). During this exchange, the Abelson gene (abl) on chromosome 9 and the breakpoint cluster region gene (bcr) on chromosome 22 generate the breakpoint cluster region-Abelson murine leukemia (BCR-ABL) fusion gene. The most frequent breakpoint on chromosome 22, located between exons 12 and 16, is called the major breakpoint cluster region (M-bcr) and with its counterpart in exon 2 of chromosome 9 results in the b2a2 and b3a2 transcripts that code for a 210 kDa protein. Less frequently, a second rearrangement, minor breakpoint cluster

Methylation analysis of the DAPK1 gene in imatinib-resistant chronic myeloid leukemia patients.

Death-associated protein kinase-1 (DAPK1) is a pro-apoptotic gene that induces cellular apoptosis in response to internal and external apoptotic stimulants. The silencing of DAPK1 can result in uncontrolled cell proliferation, indicating that it may have a role in tumor suppression. DAPK1 activity can be inhibited by the cytosine methylation that occurs in its promoter region. These methylation changes in the promoter region of DAPK1 have been reported in a range of solid and hematological malignancies. In the present study, DAPK1 methylation was investigated in chronic myeloid leukemia patients (n=43) using bisulfite conversion followed by methylation-specific polymerase chain reaction. The present study included a number of patients who were identified to be resistant to the common chemotherapeutic agent imatinib (STI571, Gleevec®, Glivec®), exhibiting at least one mutation in the breakpoint cluster region-Abelson murine leukemia (BCR-ABL) gene. Thus, the patients in the present study were divided into two groups according to their response to imatinib therapy: Non-resistant (n=26) and resistant (n=17) to imatinib. Resistant patients were characterized by the presence of single or multiple mutations of the BCR-ABL gene: i) T315I, ii) M351T, iii) E255K, iv) T315I and M351T or v) T315I, M351T and E255K. The present study identified that: i) The incidence of DAPK1 methylation was significantly higher in the resistant patients compared with the non-resistant patients; ii) the extent of resistance varied between mutation types; and iii) there was no DAPK1 methylation in any of the healthy controls. These findings indicate that DAPK1 methylation may be associated with a signaling pathway for imatinib resistance in chronic myeloid leukemia.

Clinical advances in the management of chronic myelogenous leukemia: focus on bosutinib and patient considerations.

The treatment for chronic myeloid leukemia has changed significantly over the past 15 years, and as of now, there are five BCR-ABL1 (breakpoint cluster region-Abelson murine leukemia viral oncogene homolog 1) tyrosine kinase inhibitors that have gained approval for treatment of this disease. All five are very effective drugs, and the decision surrounding which to use in specific patients is based on numerous factors. Bosutinib is one of the newer tyrosine kinase inhibitors to gain approval, and has been studied in the first-line setting as well as after failure of other tyrosine kinase inhibitors. It is an SRC-ABL1 (steroid receptor co-activator-ABL1) inhibitor that works in the presence of most kinase domain mutations. The primary side effects of bosutinib are gastrointestinal upsets. In the appropriate clinical setting, bosutinib can be considered a valuable addition to the armamentarium of treatments available for chronic myeloid leukemia.

Selectins and their ligands are required for homing and engraftment of BCR-ABL1+ leukemic stem cells in the bone marrow niche

AbstractWe investigated adhesion pathways that contribute to engraftment of breakpoint cluster region-Abelson murine leukemia viral oncogene homolog 1 (BCR-ABL1)–induced chronic myelogenous leukemia (CML)-like myeloproliferative neoplasia in a mouse retroviral transduction/transplantation model. Compared with normal stem/progenitor cells, BCR-ABL1+ progenitors had similar expression of very late antigen-4 (VLA4), VLA5, leukocyte functional antigen-1, and CXCR4 but lower expression of P-selectin glycoprotein ligand-1 (PSGL-1) and of L-selectin. Whereas vascular cell adhesion molecule-1 and P-selectin were not required, deficiency of E-selectin in the recipient bone marrow endothelium significantly reduced engraftment by BCR-ABL1–expressing stem cells following intravenous injection, with leukemogenesis restored by direct intrafemoral injection. BCR-ABL1–expressing cells deficient for PSGL-1 or the selectin ligand-synthesizing enzymes core-2 β1,6-N-acetylglucosaminyltransferase or fucosyltransferases IV/VII were impaired for engraftment, and destruction of selectin ligands on leukemic progenitors by neuraminidase reduced engraftment. BCR-ABL1–expressing L-selectin–deficient progenitors were also defective in homing and engraftment, with leukemogenesis rescued by coexpression of chimeric E/L-selectin. Antibody to L-selectin decreased the engraftment of BCR-ABL1–transduced stem cells. These results establish that BCR-ABL1+ leukemic stem cells rely to a greater extent on selectins and their ligands for homing and engraftment than do normal stem cells. Selectin blockade is a novel strategy to exploit differences between normal and leukemic stem cells that may be beneficial in autologous transplantation for CML and perhaps other leukemias.

Impact of tyrosine kinase inhibitors on minimal residual disease and outcome in childhood Philadelphia chromosome‐positive acute lymphoblastic leukemia

Breakpoint cluster region-Abelson murine leukemia viral oncogene homolog 1 (BCR-ABL1) tyrosine kinase inhibitors (TKIs) improve the outcome of patients with childhood Philadelphia chromosome (Ph)-positive acute lymphoblastic leukemia (ALL) when they are incorporated into postremission induction chemotherapy. To date, no data are available on the impact of TKIs on minimal residual disease (MRD) at the end of induction therapy among patients who have a poor early response to 2 weeks of induction therapy that does not include TKIs. The authors analyzed the early response to TKIs during remission induction in children with Ph-positive ALL who were treated at St. Jude Children's Research Hospital. MRD was measured on days 15 and 42 of induction. TKIs were incorporated into induction therapy on day 22 in the post-TKI era. TKIs produced a marked drop in MRD levels: at the end of remission induction, 9 of 11 patients who received imatinib or dasatinib and conventional induction chemotherapy achieved MRD-negative status compared with only 2 of 16 patients who received chemotherapy alone (P < .001). The 5-year event-free survival rate (± standard deviation) was 68.6% ± 19.2% for the 11 patients who received TKIs versus 31.6% ± 9.9% for the 19 patients who did not (P = .022); notably, 2 of the former group underwent hematopoietic stem cell transplantation versus 15 of the latter group (P = .002). MRD levels and outcomes did not differ significantly among 498 patients with standard-risk/high-risk, Ph-negative ALL who were treated in the pre-TKI or post-TKI eras. TKIs administered in the early phases of therapy can dramatically reduce MRD and improve the outcome of childhood Ph-positive ALL.

Myelofibrosis-associated complications: pathogenesis, clinical manifestations, and effects on outcomes

Myelofibrosis (MF) is a rare chronic BCR-ABL1 (breakpoint cluster region-Abelson murine leukemia viral oncogene homologue 1)-negative myeloproliferative neoplasm characterized by progressive bone marrow fibrosis, inefficient hematopoiesis, and shortened survival. The clinical manifestations of MF include splenomegaly, consequent to extramedullary hematopoiesis, cytopenias, and an array of potentially debilitating abdominal and constitutional symptoms. Dysregulated Janus kinase (JAK)-signal transducer and activator of transcription signaling underlies secondary disease-associated effects in MF, such as myeloproliferation, bone marrow fibrosis, constitutional symptoms, and cachexia. Common fatal complications of MF include transformation to acute leukemia, thrombohemorrhagic events, organ failure, and infections. Potential complications from hepatosplenomegaly include portal hypertension and variceal bleeding, whereas extramedullary hematopoiesis outside the spleen and liver – depending on the affected organ – may result in intracranial hypertension, spinal cord compression, pulmonary hypertension, pleural effusions, lymphadenopathy, skin lesions, and/or exacerbation of abdominal symptoms. Although allogeneic stem cell transplantation is the only potentially curative therapy, it is suitable for few patients. The JAK1/JAK2 inhibitor ruxolitinib is effective in improving splenomegaly, MF-related symptoms, and quality-of-life measures. Emerging evidence that ruxolitinib may be associated with a survival benefit in intermediate- or high-risk MF suggests the possibility of a disease-modifying effect. Consequently, ruxolitinib could provide a treatment backbone to which other (conventional and novel) therapies may be added for the prevention and effective management of specific MF-associated complications.

Bosutinib

To review clinical trials and main characteristics of bosutinib, a second-generation tyrosine kinase inhibitor (TKI) for treatment of chronic myelogenous leukemia (CML). Pertinent data were identified through a search of PubMed (January 1990-April 2013) using the primary search terms SKI-606, bosutinib, and CML. Additionally, preliminary reports published in abstract form by the American Society of Clinical Oncology and American Society of Hematology (January 1990-April 2013) were screened for inclusion. Clinical Phase 1, 2, and 3 studies reported in English evaluating the safety and efficacy of bosutinib in patients with CML were reviewed. Bosutinib is a TKI of the breakpoint cluster region/Abelson murine leukemia (BCR-ABL) gene approved by the Food and Drug Administration on September 4, 2012, for second-line treatment of chronic phase, accelerated phase, and blast phase CML. In the second-line setting, bosutinib is effective in some patients with CML resistant or intolerant to imatinib, dasatinib, and/or nilotinib, but it is not effective in patients whose disease expresses the T315I point mutation in BCR-ABL. Bosutinib also has been compared with imatinib, the standard first-line treatment, in 502 patients with newly diagnosed chronic phase CML in a Phase 3 trial. Complete cytogenetic response at 12 months, the primary efficacy end point, is similar between bosutinib and imatinib (p = 0.601); therefore, bosutinib is not indicated in the first-line setting. Common adverse events associated with bosutinib include diarrhea, nausea, and vomiting. Grade 3 and 4 adverse events reported in at least 5% of bosutinib-treated patients include elevated serum lipase and liver aminotransferases, anemia, thrombocytopenia, neutropenia, and diarrhea. Currently available clinical trials suggest that bosutinib is generally a safe and effective treatment option for patients with CML who have failed first-line TKIs and who do not express the T315I mutation; however, tolerability may be problematic for some patients.

Molecular characterization of canine BCR‐ABL–positive chronic myelomonocytic leukemia before and after chemotherapy

Genetic aberrations linked to tumorigenesis have been identified in both canine and human hematopoietic malignancies. While the response of human patients to cancer treatments is often evaluated using cytogenetic techniques, this approach has not been used for dogs with comparable neoplasias. The aim of this study was to demonstrate the applicability of cytogenetic techniques to evaluate the cytogenetic response of canine leukemia to chemotherapy. Cytology and flow cytometric techniques were used to diagnose chronic myelomonocytic leukemia in a dog. High-resolution oligonucleotide array comparative genomic hybridization (oaCGH) and multicolor fluorescence in situ hybridization (FISH) were performed to identify and characterize DNA copy number aberrations (CNAs) and targeted structural chromosome aberrations in peripheral blood WBC at the time of diagnosis and following one week of chemotherapy. At the time of diagnosis, oaCGH indicated the presence of 22 distinct CNAs, of which trisomy of dog chromosome 7 (CFA 7) was the most evident. FISH analysis revealed that this CNA was present in 42% of leukemic cells; in addition, a breakpoint cluster region-Abelson murine leukemia viral oncogene homolog (BCR-ABL) translocation was evident in 17.3% of cells. After one week of treatment, the percentage of cells affected by trisomy of CFA7 and BCR-ABL translocation was reduced to 2% and 3.3%, respectively. Chromosome aberrations in canine leukemic cells may be monitored by molecular cytogenetic techniques to demonstrate cytogenetic remission following treatment. Further understanding of the genetic aberrations involved in canine leukemia may be crucial to improve treatment protocols.

Additive antileukemia effects by GFI1B- and BCR–ABL-specific siRNA in advanced phase chronic myeloid leukemic cells

Previous studies demonstrated selective inhibition of the BCR-ABL (breakpoint cluster region-Abelson murine leukemia oncogene) tyrosine kinase by RNA interference in leukemic cells. In this study, we evaluated the effect of BCR-ABL small interfering RNA (siRNA) and GFI1B siRNA silencing on chronic myeloid leukemia (CML) cells in myeloid blast crises. The GFI1B gene was mapped to chromosome 9 and is, therefore, located downstream of the BCR-ABL translocation in CML cells. Co-transfection of BCR-ABL siRNA and GFI1B siRNA dramatically decreased cell viability and significantly induced apoptosis and inhibited proliferation in K562 cells (P<0.0001) and primary advanced phase CML cells (P<0.0001) versus controls. Furthermore, combining of BCR-ABL siRNA and GFI1B siRNA significantly modified the expression of several relevant genes including Myc, MDR1, MRP1 and tyrosyl-phosphoproteins in primary CML cells. Our data suggest that silencing of both BCR-ABL siRNA and GFI1B siRNA is associated with an additive antileukemic effect against K562 cells and primary advanced CML cells, further validating these genes as attractive therapeutic targets.

Mutations in the transmembrane and juxtamembrane domains enhance IL27R transforming activity

Cytokines and their receptors regulate haemopoiesis by controlling cellular growth, survival and differentiation. Thus it is not surprising that mutations of cytokine receptors contribute to the formation of haemopoietic disorders, including cancer. We recently identified transforming properties of IL27R, the ligand-binding component of the receptor for interleukin-27. Although wild-type IL27R exhibits transforming properties in haemopoietic cells, in the present study we set out to determine if the transforming activity of IL27R could be enhanced by mutation. We identified three mutations of IL27R that enhance its transforming activity. One of these mutations is a phenylalanine to cysteine mutation at residue 523 (F523C) in the transmembrane domain of the receptor. The two other mutations identified involve deletions of amino acids in the cytoplasmic juxtamembrane region of the receptor. Expression of each of these mutant IL27R proteins led to rapid cytokine-independent transformation in haemopoietic cells. Moreover, the rate of transformation induced by these mutants was significantly greater than that induced by wild-type IL27R. Expression of these IL27R mutants also induced enhanced activation of JAK (Janus kinase)/STAT (signal transducer and activator of transcription) signalling compared with wild-type. An activating deletion mutation of IL27R enhanced homodimerization of the receptor by a mechanism that may involve disulfide bonding. These transforming IL27R mutants displayed equal or greater transforming activity than bona fide haemopoietic oncogenes such as BCR-ABL (breakpoint cluster region-Abelson murine leukaemia viral oncogene homologue) and JAK2-V617F. Since IL27R is expressed on haemopoietic stem cells, lymphoid cells and myeloid cells, including acute myeloid leukaemia blast cells, mutation of this receptor has the potential to contribute to a variety of haemopoietic neoplasms.

Long‐term outcomes in the second‐line treatment of chronic myeloid leukemia

AbstractChronic myeloid leukemia (CML) is a progressive and often fatal myeloproliferative neoplasm. The hallmark of CML is an acquired chromosomal translocation known as the Philadelphia chromosome (Ph), which results in the synthesis of the breakpoint cluster region‐Abelson murine leukemia (BCR‐ABL) fusion oncoprotein, a constitutively active tyrosine kinase. The introduction of imatinib, a tyrosine kinase inhibitor (TKI) that is specific for BCR‐ABL, was a major breakthrough in CML therapy. Although most patients respond to first‐line imatinib therapy, some experience loss of response (resistance) or require treatment discontinuation because of toxicity (intolerance). For patients with CML, failure on standard‐dose imatinib therapy (400 mg daily), imatinib dose escalation (600‐800 mg daily) is a second‐line option. However, high‐dose imatinib is not an appropriate approach for patients who experience drug toxicity, and there remain questions over the durability of responses achieved with this strategy. Alternative second‐line options include the TKIs dasatinib and nilotinib. A substantial amount of long‐term data for these agents is available. Although both are potent and specific BCR‐ABL TKIs, dasatinib and nilotinib exhibit unique pharmacologic profiles and response patterns relative to different patient characteristics, such as disease stage and BCR‐ABL mutation status. To optimize therapeutic benefit, clinicians should select treatment based on each patient's historic response, adverse‐event tolerance, and risk factors. Cancer 2010. © 2010 American Cancer Society.

Intolerance to tyrosine kinase inhibitors in chronic myeloid leukemia

Tyrosine kinase inhibitor (TKI) treatment targeting breakpoint cluster region-Abelson murine leukemia virus, the cause of chronic myeloid leukemia (CML), has revolutionized therapy for patients with this disease. The majority of patients with CML maintain favorable responses with long-term imatinib therapy; however, the availability of the second-generation TKIs nilotinib and dasatinib limits the need for patients intolerant to imatinib to continue with therapy. Unfortunately, there is currently no standard definition of intolerance to imatinib. Common Toxicity Criteria for grading adverse events, designed to identify acute toxicities, are often used to determine intolerance. However, because CML therapies are long-term, patient quality of life may provide a better measure of true intolerance. Several general methods of quantifying patient quality of life are in use for patients with CML, and a CML-specific variant of the M. D. Anderson Symptom Inventory is in development. An appropriate and consistent definition of intolerance will provide clinicians with an algorithm for managing their patients with severe or chronic adverse events during treatment with imatinib. As more long-term data become available for newer TKIs, the definition of intolerance in the context of CML treatment will continue to evolve to maximize the likelihood of durable responses and superior quality of life for patients.

The flavonoid tangeretin activates the unfolded protein response and synergizes with imatinib in the erythroleukemia cell line K562

We explored the mechanism of cell death of the polymethoxyflavone tangeretin (TAN) in K562 breakpoint cluster region-abelson murine leukemia (Bcr-Abl+) cells. Flow cytometric analysis showed that TAN arrested the cells in the G(2)/M phase and stimulated an accumulation of the cells in the sub-G(0) phase. TAN-induced cell death was evidenced by poly(ADP)-ribose polymerase cleavage, DNA laddering fragmentation, activation of the caspase cascade and downregulation of the antiapoptotic proteins Mcl-1 and Bcl-x(L). Pretreatment with the pancaspase inhibitor Z-VAD-FMK_blocked caspase activation and cell cycle arrest but did not inhibit apoptosis which suggest that other cell killing mechanisms like endoplasmic reticulum (ER)-associated cell death pathways could be involved. We demonstrated that TAN-induced apoptosis was preceded by a rapid activation of the proapoptotic arm of the unfolded protein response, namely PKR-like ER kinase. This was accompanied by enhanced levels of glucose-regulated protein of 78 kDa and of spliced X-box binding protein 1. Furthermore, TAN sensitized K562 cells to the cell killing effects of imatinib via an apoptotic mechanism. In conclusion, our results suggest that TAN is able to induce apoptosis in Bcr-Abl+ cells via cell cycle arrest and the induction of the unfolded protein response, and has synergistic cytotoxicity with imatinib.

Hematopathologic and cytogenetic findings in imatinib mesylate treated chronic myelogenous leukemia patients: 2.5 years' experience

Imatinib mesylate, a tyrosine kinase inhibitor with specific activity against the breakpoint cluster region--Abelson murine leukemia (BCR-ABL) tyrosine kinase has been developed for treatment of chronic myelogenous leukemia (CML). Its hematologic and cytogenetic effects have been evaluated in a series of clinical trials. The aim of this study was to report hematologic and cytogenetic response in CML patients during the treatment with imatinib mesylate. A total of 21 patients were treated and observed from July 2006 to December 2008. The median time from CML diagnosis was no more than 12 months, so all the patients received previous treatment with hydroxyurea for which the median time was 3 months. The patients received imatinib mesylate in an effective oral dose of 400 to 800 mg daily, which was followed with peripheral blood counts, bone marrow examination, and cytogenetic studies at 6, 12, 18 and 24 months. Complete hematologic responses were reported for 19 (90.48%) of 21 patients studied. Among 19 patients who had a response, 16 (86%) did so within 3 months. The best cytogenetic response rate at any time during the study treatment with imatinib mesylate, among 14 patients in which cytogenetic response evaluated was: complete cytogenetic response in 7 (50%) patients, partial cytogenetic response in 6 (42.9%) patients and minor cytogenetic response in 1 (7.1%) patient. No patients had progressed to accelerated or blastic phase. The most frequent adverse effects that seemed to be related to treatment with imatinib mesylate were edema and musculoskeletal pain; overall, most were mild. Only one patient discontinued treatment because of hematologic toxic effects. The results obtained in this study confirm that imatinib mesylate induces a complete hematological and cytogenetic response in a high percentage of patients with chronic-phase CML.