Breakpoint Cluster region-Abelson Research Articles

Secondary thrombotic microangiopathy in two patients with Philadelphia-positive hematological malignancies treated with imatinib mesylate

Drug-mediated thrombotic microangiopathy may cause life-threatening medical emergencies. Novel targeted therapies have dramatically changed the prognosis of a number of oncological diseases. Tyrosine kinase inhibitors of the Breakpoint Cluster Region-Abelson (BCR-ABL) oncoprotein are used in patients with chronic myeloid leukemia or Philadelphia chromosome-positive acute lymphoblastic leukemia. Imatinib mesylate, which was the first anti-BCR-ABL tyrosine kinase inhibitor, has demonstrated a high tolerance profile and efficacy in these patients for many years. Good results have also been observed in patients with gastrointestinal stromal tumors. In this study, we describe two patients with Philadelphia chromosome-positive hematological malignancies who presented with secondary thrombotic microangiopathy that was most likely linked to the use of imatinib. Other potential causes of thrombotic microangiopathy were discarded, and the predisposing role of some comorbidities and potential short or long-term drug-drug interactions was assessed. The clinical and biological data were more indicative of atypical secondary hemolytic uremic syndrome in one of the cases and of secondary thrombotic microangiopathy with renal and cardiac impairment in the other, which is also categorized as secondary hemolytic uremic syndrome. The outcome was favorable after imatinib discontinuation and the treatment of severe cardiac and renal failures.

Hematologic, liver enzymes and electrolytes changes in chronic myeloid leukemia after Imatinib medication.

Chronic myeloid leukemia (CML), is the first malignancy that related to the chromosomal abnormality and include 15-20% of all adulthood leukemia. This study aimed to compare the hematologic, breakpoint cluster region-abelson (BCR-ABL) and liver function enzymes changes during treatment period of Imatinib. A noncurrent clinical trial study. New incident CML patients received Iranian made or Indian-made Imatinib after baseline measurement. Hematologic, BCR-ABL, electrolytes and liver function enzymes measured again after 24 weeks. Paired t-test and independent t-test was used to assess the effect of treatment in within and between groups, respectively. Imatinib has a decreasing impact on white blood cells and placates. While an increasing effect on hemoglobin concentration. Iranian made and Indian-made Imatinib has a same effect on improvement of hematologic, BCR-ABL, electrolytes in CML patients. However, the liver changes of Imatinib were not clinically significant. The Iranian-made Imatinib can be used as a replacement for Indian made ones without any statistical and clinical significant difference on Improvement of CML patients.

Monitoring of Disease Activity in Chronic Myeloid Leukemia-chronic Phase Patients Treated with Indian Generic Veenat (NATCO) Imatinib Mesylate: A Tertiary Care Experience

Aim: Real-time quantitative polymerase chain reaction (RT-PCR) is a sensitive technique to monitor treatment response in chronic myeloid leukemia (CML). Standardization of RT-PCR protocols and interpretation of results are important to maintain the reliability of this molecular test. Methods: We present the analysis of treatment monitoring after administration of Indian generic imatinib mesylate (IM) (Veenat) in 73 patients with CML-chronic phase using RT-PCR. Results: A consistent decrease in the median breakpoint cluster region-abelson1 (BCR-ABL1) percentage denoting a continued time-bound response to IM is observed. At 6 months, 87.5% patients showing ≥ 1-log reduction in BCR-ABL1 levels subsequently developed ≥ 3-log reduction as compared to 42.8% patients showing < 1-log reduction. All patients with ≥ 3-log reduction in BCR-ABL1 at 12 months maintained treatment response at 18 months. Conclusion: The efficacy of Veenat (NATCO) is comparable to Gleevac (Novartis). Patients who attain ≥ 1-log reduction at 6 months and ≥ 2-log reduction at 12 months are more likely to subsequently attain a major molecular response.

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

Myeloproliferative neoplasms: JAK2 signaling pathway as a central target for therapy.

The discovery of the JAK2V617F mutation followed by the discovery of other genetic abnormalities allowed important progress in the understanding of the pathogenesis and management of myeloproliferative neoplasms (MPN)s. Classical Breakpoint cluster region-Abelson (BCR-ABL)-negative neoplasms include 3 main disorders: essential thrombocythemia (ET), polycythemia vera (PV), and primary myelofibrosis (PMF). Genomic studies have shown that these disorders are more heterogeneous than previously thought with 3 main entities corresponding to different gene mutations: the JAK2 disorder, essentially due to JAK2V617F mutation, which includes nearly all PVs and a majority of ETs and PMFs with a continuum between these diseases and the myeloproliferative leukemia (MPL) and calreticulin (CALR) disorders, which include a fraction of ET and PMF. All of these mutations lead to a JAK2 constitutive activation. Murine models either with JAK2V617F or MPLW515L, but also with JAK2 or MPL germ line mutations found in hereditary thrombocytosis, have demonstrated that they are drivers of myeloproliferation. However, the myeloproliferative driver mutation is still unknown in approximately 15% of ET and PMF, but appears to also target the JAK/Signal Transducer and Activator of Transcription (STAT) pathway. However, other mutations in genes involved in epigenetics or splicing also can be present and can predate or follow mutations in signaling. They are involved either in clonal dominance or in phenotypic changes, more particularly in PMF. They can be associated with leukemic progression and might have an important prognostic value such as additional sex comb-like 1 mutations. Despite this heterogeneity, it is tempting to target JAK2 and its signaling for therapy. However in PMF, Adenosine Tri-Phosphate (ATP)-competitive JAK2 inhibitors have shown their interest, but also their important limitations. Thus, other approaches are required, which are discussed in this review.

Frequency of p190 and p210 BCR-ABL rearrangements and survival in Brazilian adult patients with acute lymphoblastic leukemia.

ObjectiveThis study investigated the occurrence of the p190 and p210 breakpoint cluster region-Abelson (BCR-ABL) rearrangements in adults with acute lymphoblastic leukemia and possible associations with clinical and laboratory characteristics and survival.MethodsForty-one over 18-year-old patients with acute lymphoblastic leukemia of both genders followed-up between January 2008 and May 2012 were included in this study. Clinical and laboratory data were obtained from the medical charts of the patients. Reverse transcription polymerase chain reaction (RT-PCR) using specific primers was employed to identify molecular rearrangements.ResultsAt diagnosis, the median age was 33 years, and there was a predominance of males (61%). The most common immunophenotype was B lineage (76%). BCR-ABL rearrangements was detected in 14 (34%) patients with the following distribution: p190 (28%), p210 (50%) and double positive (22%). Overall survival of patients with a mean/median of 331/246 days of follow up was 39%, respectively, negative BCR-ABL (44%) and positive BCR-ABL (28%).ConclusionThese results confirm the high frequency of BCR-ABL rearrangements and the low survival rate of adult Brazilian patients with acute lymphoblastic leukemia.

Diversity of breakpoints of variant Philadelphia chromosomes in chronic myeloid leukemia in Brazilian patients.

BackgroundChronic myeloid leukemia is a myeloproliferative disorder characterized by the Philadelphia chromosome or t(9;22)(q34.1;q11.2), resulting in the break-point cluster region-Abelson tyrosine kinase fusion gene, which encodes a constitutively active tyrosine kinase protein. The Philadelphia chromosome is detected by karyotyping in around 90% of chronic myeloid leukemia patients, but 5–10% may have variant types. Variant Philadelphia chromosomes are characterized by the involvement of another chromosome in addition to chromosome 9 or 22. It can be a simple type of variant when one other chromosome is involved, or complex, in which two or more chromosomes take part in the translocation. Few studies have reported the incidence of variant Philadelphia chromosomes or the breakpoints involved among Brazilian chronic myeloid leukemia patients.ObjectiveThe aim of this report is to describe the diversity of the variant Philadelphia chromosomes found and highlight some interesting breakpoint candidates for further studies.Methodsthe Cytogenetics Section Database was searched for all cases with diagnoses of chronic myeloid leukemia during a 12-year period and all the variant Philadelphia chromosomes were listed.ResultsFifty (5.17%) cases out of 1071 Philadelphia-positive chronic myeloid leukemia were variants. The most frequently involved chromosome was 17, followed by chromosomes: 1, 20, 6, 11, 2, 10, 12 and 15.ConclusionAmong all the breakpoints seen in this survey, six had previously been described: 11p15, 14q32, 15q11.2, 16p13.1, 17p13 and 17q21. The fact that some regions get more frequently involved in such rare rearrangements calls attention to possible predisposition that should be further studied. Nevertheless, the pathological implication of these variants remains unclear.

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.

ChemInform Abstract: Anticancer Activity of Pyrazole via Different Biological Mechanisms

AbstractReview: 109 refs.

HS-438, a new inhibitor of Imatinib-resistant BCR-ABL T315I mutation in chronic myeloid leukemia

Imatinib is a selective breakpoint cluster region-Abelson (BCR-ABL) tyrosine kinase inhibitor (TKI) that has significantly improved the prognosis of patients with chronic myeloid leukemia (CML). However, T315I gene mutations of the BCR-ABL kinase domain have been shown to confer resistance to imatinib. In the present study, we synthesized a novel BCR-ABL inhibitor, HS-438, and identified its anti-leukemic effects in vitro and in vivo. We found that HS-438 strongly inhibited the expression of BCR-ABL signaling pathways in wild-type BCR-ABL (BaF3/WT) cells as well as T315I-mutated BCR-ABL (BaF3/T315I) cells with resistance to imatinib. HS-438 induced cell cycle arrest, particularly during the G0/G1 cell cycle phase, and induced apoptosis. In BaF3/T315I xenograft models, HS-438 significantly delayed tumor growth, unlike imatinib. In summary, we suggest that HS-438 may be a novel drug candidate with the therapeutic potential to target BCR-ABL and overcome imatinib resistance in patients with CML.

Heterogeneity of BCR-ABL rearrangements in patients with Chronic Myeloid Leukemia in Pakistan

Breakpoint cluster region-Abelson (BCR-ABL) rearrangement or Philadelphia (Ph) chromosome in Chronic Myeloid Leukemia (CML) is derived from a reciprocal chromosomal translocation between ABL gene on chromosome 9 and BCR gene on chromosome 22. This chimeric protein has various sizes and therefore different clinical behaviour. The purpose of this study was to determine the heterogeneity of BCR-ABL rearrangement in patients with Ph(+)CML in Pakistan.The study was conducted at Civil Hospital and Baqai Institute of Hematology (BIH) Karachi. Blood samples from 25 patients with CML were collected. Multiplex reverse transcription polymerase chain reaction (RT-PCR) was performed to identify various BCR-ABL transcripts.All 25 samples showed BCR-ABL rearrangements. Out of these, 24 (96%) patients expressed p210 BCR-ABL rearrangements i.e. 60% (n=15) had b3a2 and 32% (n=8) had b2a2 rearrangements. Co-expression of b3a2 /b2a2 rearrangement and p190 (e1a3) rearrangement was also identified in two patients.It is apparent that majority of the patients had p210 BCR-ABL rearrangements. Frequency of co-expression and rare fusion transcripts was very low.

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.

ABCB1 haplotypes are associated with P-gp activity and affect a major molecular response in chronic myeloid leukemia patients treated with a standard dose of imatinib

Despite the high efficacy of imatinib mesylate (IM) treatment for chronic myeloid leukemia (CML) patients, some individuals develop resistance due to impaired bioavailability. It has been previously demonstrated that the haplotypes for ATP-binding cassette subfamily B member 1 (ABCB1)with c.1236C>T, c.3435C>T and c.2677G>T/A polymorphisms markedly affect the secondary structure of ABCB1 mRNA and its activity. These modifications may affect efflux transporter activity and response to treatment with IM. The aim of the present study was to investigate the influence of ABCB1 haplotypes on P-glycoprotein (P-gp) activity, IM plasma levels and IM response. In total, 28 chronic-phase CML patients treated with a standard dose of IM (400 mg/day) were studied. The patients were selected according to the haplotypes of ABCB1, with c.1236C>T, c.3435C>T and c.2677G>T polymorphisms, and were classified into two groups based on the presence of the mutated allele in each genotype for the three ABCB1 polymorphisms. In addition, expression of P-gp and breakpoint cluster region-abelson 1 (BCR-ABL1), ABCB1 and solute carrier family 22 member 1 (SLC22A1) mRNA were evaluated. The P-gp activity in the wild-type group was found to be higher than that in the mutated group (59.1 vs. 38.3%; P=0.001). Furthermore, the patients who did not achieve major molecular response (MMR) showed a higher rate of efflux mediated by P-gp when compared with individuals who achieved MMR (64.7 vs. 45.7%; P=0.001). All patients without MMR demonstrated effluxes of >60%. In addition, patients without MMR exhibited lower plasma concentrations of IM compared with those with MMR (0.51 vs. 1.42 μg/ml; P=0.001). Higher levels of SLC22A1 mRNA were observed in patients who achieved MMR and complete molecular response (P<0.05). In conclusion, the ABCB1 1236CT/3435CT/2677GT and 1236TT/3435TT/2677TT haplotypes are associated with reduced P-gp activity and MMR in chronic-phase CML patients treated with a standard dose of IM.

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.

Predicting Outcomes in Patients With Chronic Myeloid Leukemia at Any Time During Tyrosine Kinase Inhibitor Therapy

Current recommendations for monitoring patients with chronic myeloid leukemia (CML) provide recommendations for response assessment and treatment only at 3, 6, 12, and 18 months. These recommendations are based on clinical trial outcomes computed from treatment start. Conditional survival estimates take into account the changing hazard rates as time from treatment elapses as a continuum. We performed conditional survival analyses among patients with CML to improve prognostication at any time point during the course of therapy. We used 2 cohorts of patients with CML in chronic phase: 1 treated in the frontline DASISION (Dasatinib versus Imatinib Study in Treatment - Naïve CML) phase III study (n = 519) and another treated after imatinib treatment had failed in the dasatinib dose-optimization phase III CA180-034 study (n = 670). Conditional survival estimates were calculated. A modified Cox proportional hazards model was used to build a prognostic nomogram. As the time alive or free from events from commencement of treatment increased, conditional survival estimates changed. No differences were observed regarding future outcomes between patients treated with imatinib or dasatinib in the frontline setting for patients with the same breakpoint cluster region-abelson 1 (BCR-ABL1) transcript levels evaluated at the same time point. Age older than 60 years greatly affected future outcomes particularly in the short-term. Conditional survival-based nomograms allowed the prediction of future outcomes at any time point. In summary, we designed a calculator to predict future outcomes of patients with CML at any time point during the course of therapy.

Ponatinib: a miracle or a disaster in chronic myeloid leukemia

Chronic myeloid leukemia (CML), the most common myeloproliferative disorder, occurring due to balanced reciprocal translocation between chromosome 9 and 22 and resulting in a chimeric oncogene called breakpoint cluster region-abelson (BCR-ABL) whose protein product has tyrosine kinase activity, causes uncontrolled proliferation of the myeloid cells. Although, imatinib, the first-generation tyrosine kinase inhibitor (TKI) achieved an extremely high response rate, some patients developed resistance to it. Thus, second-generation TKIs such as nilotinib, dasatinib, bosutinib were developed which proved very useful, till the emergence of T315I point mutation which occurs in the BCR-ABL gene and renders CML resistant to previous TKIs. Ponatinib, a third generation TKI approved by the United States Food and Drug Administration (FDA), showed great promise as it was effective even against T315I point mutation. However, a recent increase in the incidence of blood clots observed in patients taking ponatinib has resulted in FDA temporarily suspending all trials, marketing and distribution of the drug. Hence, whether ponatinib evolves as a miracle or disaster for the patients of CML is yet to be answered.

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.

A comprehensive analysis of breakpoint cluster region-abelson fusion oncogene splice variants in chronic myeloid leukemia and their correlation with disease biology.

BACKGROUND:BCR-ABL fusion oncogene is a hallmark of Chronic Myeloid Leukemia (CML). It results due to translocation between chromosome 22 and chromosome 9 [t (9; 22)(q34; q11)]. It gives rise to translation of a 210 KDa chimeric protein (p210), leading to enhanced tyrosine kinase activity and activation of leukemogenic pathways, ultimately causing onset of CML. In case of CML, the classic fusions are b2a2 or b3a2, fusing exon 13 (b2) or exon 14 (b3) of BCR, respectively, to exon 2 (a2) of ABL. The type of BCR-ABL transcripts are thought to be have different prognosis and hence useful in clinical decision-making. The frequencies of different fusion oncogenes associated with leukemia can vary in different ethnic groups and geographical regions due to interplay of genetic variation in different ethnic populations, diverse environmental factors and living style. Moreover, earlier relevant studies from our region were carried out in small subset of patients. Therefore, objective of this study was to find out frequencies of different BCR-ABL splice variants in larger subset of CML patients.METHODS:A nested reverse transcriptase polymerase chain reaction (RT-PCR) was established to detect BCR-ABL splice variants in 130 CML patients. Sensitivity of RT-PCR and ability to detect BCR-ABL fusion gene in least possible time was studied.RESULTS:BCR-ABL detection using our optimized RT-PCR protocol could be completed in 8 hours, starting from RNA extraction to Gel electrophoresis. Sensitivity of RT-PCR assay was of the order of 10−6. Out of 130 Pakistani patients, 83 (63.84%) expressed b3a2 while 47 (36.15%) expressed b2a2 transcript.CONCLUSION:Our RT-PCR was proved to be very quick to detect BCR-ABL fusion oncogene in CML patients within one working day. Because of its sensitivity, it can be used to monitor complete molecular response in CML. BCR-ABL RT-PCR and BCR-ABL splice variants frequency in our study differs from other ethnic groups. It shows that ethnic and geographical differences exist in BCR-ABL splice variant frequency, which may have a profound effect on disease biology as well as implications in prognosis and clinical management of BCR-ABL positive leukemias.

BCR-ABL Splice Variants In Three Phases Of CML: Association With Disease Biology and Response To Imatinib

BackgroundPhiladelphia chromosome, a characteristic chromosomal translocation (breakpoint cluster region-Abelson [BCR–ABL]; t [9; 22] [q34; q11]) in chronic myeloid leukemia (CML) encodes a product, which is the target of tyrosine kinase inhibitors (TKIs). In most CML patients, during translocation, the break takes place within a 5.8-kb region on both sides of BCR exons12-16 (originally referred to as exons b1-b5), described as themajor breakpoint cluster region (M-bcr)1. It can be either between exons b2 and b3, or between exons b3 and b4. The ABL exon which is mostly inserted in break points of BCR is a2. As a result of alternativesplicing, fusion transcripts with either b2a2 or b3a2 splicing variantcan be produced. Occasionally, breakpoints occur in unusual places, resulting in generation of rare BCR-ABL transcripts (b2a3, b3a3, e1a2, e8a2, e19a2). Association of BCR-ABL splice variants with clinical outcome in different phases of CML has rarely been studied2. We studied BCR/ABL splice variants and their association with disease biology and response to imatinib in 3 phases of CML in 70 patients. MethodsTotal RNA was extracted and reverse transcribed. PCR primers and nested PCR protocol for the detection of BCR-ABL splice variants in CML patients were adopted from van Dongen et al., 1999 3. Data was analyzed using SPSS Software version 17. ResultsMedian age of the patients was 34 years; 10 patients were 18 or younger and there were 40 females. 26 patients were in chronic phase (CP), 26 in accelerated phase (AP) and 18 in blast phase (BP). Overall, the frequencies of BCR/ABL splice variants b3a2, b2a2 and b3a2+b2a2 were found in 49 (70%), 15 (21.4%) and 6 (8.6%) patients, respectively. No rare BCR-ABL transcripts were identified. Percentage of BCR-ABL splice variant b2a2 was similar in patients with CP (31) and BP (28) of CML and low in AP (7.75). While the percentage of BCR-ABL splice variant b3a2 was more common in AP (84.5) and BP (72) as compared to CP (54). The combined expression of both transcripts (b3a2 and b2a2) was found in 4 patients with CP and 2 in AP of CML but none in BP of CML (Table 1). The co-existence of b2a2 and b3a2 transcripts was observed only in male patients. The BCR-ABL transcripts had no correlation with the age. Patients with the splice variant b2a2 had a better response to imatinib treatment and better survival as compared to patients with b3a2. The patients expressing both transcripts (b3a2 and b2a2) also showed better survival as compared to patients with only b3a2 transcript (figure 1). [Display omitted] Discussion and ConclusionsWe found a higher percentage of BCR-ABL splice variant b3a2 in AP & BP as compared to CP. Patients with the BCR-ABL splice variant b2a2 had a better response to imatinib and better survival, which is in contrast to previous reports 4. Co-existence of two transcripts b3a2 and b2a2 was observed mostly in CP, and in some patients in AP; it was also associated with a better response to imatinib. Larger studies are needed to further define the role of BCR-ABL splice variants in different phases of CML and their association with response to TKIs and prognosis. Studies of BCR-ABL splice variants can provide further insights into CML biology and new targets for BCR-ABL positive leukemia treatment 1, 5.

Targeting autophagy potentiates the apoptotic effect of histone deacetylase inhibitors in t(8;21) AML cells

AbstractThe role of autophagy during leukemia treatment is unclear. On the one hand, autophagy might be induced as a prosurvival response to therapy, thereby reducing treatment efficiency. On the other hand, autophagy may contribute to degradation of fusion oncoproteins, as recently demonstrated for promyelocytic leukemia–retinoic acid receptor α and breakpoint cluster region–abelson, thereby facilitating leukemia treatment. Here, we investigated these opposing roles of autophagy in t(8;21) acute myeloid leukemia (AML) cells, which express the most frequently occurring AML fusion oncoprotein, AML1–eight-twenty-one (ETO). We demonstrate that autophagy is induced by AML1-ETO–targeting drugs, such as the histone deacetylase inhibitors (HDACis) valproic acid (VPA) and vorinostat. Furthermore, we show that autophagy does not mediate degradation of AML1-ETO but rather has a prosurvival role in AML cells, as inhibition of autophagy significantly reduced the viability and colony-forming ability of HDACi-treated AML cells. Combined treatment with HDACis and autophagy inhibitors such as chloroquine (CQ) led to a massive accumulation of ubiquitinated proteins that correlated with increased cell death. Finally, we show that VPA induced autophagy in t(8;21) AML patient cells, and combined treatment with CQ enhanced cell death. Because VPA and CQ are well-tolerated drugs, combinatorial therapy with VPA and CQ could represent an attractive treatment option for AML1-ETO–positive leukemia.