Lymphoid preponderance and the absence of basophilia and splenomegaly are frequent in m-bcr-positive chronic myelogenous leukemia

Chronic Myelogenous Leukemia with Double Philadelphia Chromosome and Coexpression of p210 and p190 Fusion Transcripts

The Philadelphia (Ph+) chromosome, t(9;22)(q34;q11.2), originates from a chimeric gene called BCR-ABL and is present in more than 90% of CML patients. Most patients with CML express the protein p210 BCR-ABL and, with a frequency lower than 5%, express rare isoforms, the main one being p190. In the transition from the chronic phase to the blast phase (BP), additional chromosomal abnormalities, such as the presence of the double Ph+ chromosome, are revealed. Of the 1132 patients analyzed via molecular biology in this study, two patients (0.17%) showed the co-expression of the p210 and p190 isoforms for the BCR-ABL transcript, with the concomitant presence of a double Ph+ chromosome, which was observed via conventional cytogenetics and confirmed by fluorescent in situ hybridization. The BCR-ABL/ABL% p210 and p190 ratio increased in these two patients from diagnosis to progression to blast crisis. To our knowledge, this is the first report in the literature of patients who co-expressed the two main BCR-ABL transcript isoforms and concomitantly presented Ph+ chromosome duplication. The evolution from the chronic phase to BP often occurs within 5 to 7 years, and, in this study, the evolution to BP was earlier, since disease-free survival was on average 4.5 months and overall survival was on average 9.5 months. The presence of the p190 transcript and the double Ph+ chromosome in CML may be related to the vertiginous progression of the disease.

High incidence of minor and micro breakpoints in Chronic Myeloid Leukaemia with additional cytogenetic abnormalities at diagnosis – the Western Australian series

Introduction and objective

Chronic Myeloid Leukaemia (CML) is defined by the presence of the Philadelphia chromosome, a balanced translocation between chromosomes 9 and 22 that results in the constitutively active tyrosine kinase, BCR-ABL1. Additional chromosomal abnormalities (ACAs) at diagnosis occur in 5–10% of CML patients, and are important for prognosis. They are classified as major or minor route. The purpose of our study was to determine the frequency and type of ACAs in 193 newly diagnosed CML patients, and to evaluate patient characteristics, treatment response, and survival.

Methods

Medical records, in conjunction with data from the PathWest cytogenetics and molecular laboratories, were analysed.

Results

ACAs were present in 14 (7.3%) of patients at diagnosis. Seven patients had major-route abnormalities, with additional chromosome 8 (+8) the most common. All patients were treated with tyrosine kinase inhibitors (TKIs). Three patients presented in blast crisis; two patients have died. Of note, there was a high incidence of the rare minor and micro BCR-ABL1 fusion transcripts.

Conclusions

Frequency of ACAs at diagnosis was similar to that of previous reports. These patients consist a higher-risk cohort, and require individualised treatment, with consideration of frontline and secondary TKIs, adjunct chemotherapy, novel agents, and allogeneic stem cell transplant.

Genetic Landscape of Myeloproliferative Neoplasms with an Emphasis on Molecular Diagnostic Laboratory Testing

Chronic myeloproliferative neoplasms (MPNs) are hematopoietic stem cell neoplasms with driver events including the BCR-ABL1 translocation leading to a diagnosis of chronic myeloid leukemia (CML), or somatic mutations in JAK2, CALR, or MPL resulting in Philadelphia-chromosome-negative MPNs with constitutive activation of the JAK-STAT signaling pathway. In the Philadelphia-chromosome-negative MPNs, modern sequencing panels have identified a vast molecular landscape including additional mutations in genes involved in splicing, signal transduction, DNA methylation, and chromatin modification such as ASXL1, SF3B1, SRSF2, and U2AF1. These additional mutations often influence prognosis in MPNs and therefore are increasingly important for risk stratification. This review focuses on the molecular alterations within the WHO classification of MPNs and laboratory testing used for diagnosis.

Impact of the Breakpoint Region on the Leukemogenic Potential and the TKI Responsiveness of Atypical BCR-ABL1 Transcripts

Chronic Myeloid Leukemia (CML) is a hematological disorder characterized by the clonal expansion of a hematopoietic stem cell carrying the Philadelphia chromosome that juxtaposes the BCR and ABL1 genes. The ensuing BCR-ABL1 chimeric oncogene is characterized by a breakpoint region that generally involves exons 1, 13 or 14 in BCR and exon 2 in ABL1. Additional breakpoint regions, generating uncommon BCR-ABL1 fusion transcripts, have been detected in various CML patients. However, to date, the impact of these infrequent transcripts on BCR-ABL1-dependent leukemogenesis and sensitivity to tyrosine kinase inhibitors (TKIs) remain unclear. We analyzed the transforming potential and TKIs responsiveness of three atypical BCR-ABL1 fusions identified in CML patients, and of two additional BCR-ABL1 constructs with lab-engineered breakpoints. We observed that modifications in the DC2 domain of BCR and SH3 region of ABL1 affect BCR-ABL1 catalytic efficiency and leukemogenic ability. Moreover, employing immortalized cell lines and primary CD34-positive progenitors, we demonstrate that these modifications lead to reduced BCR-ABL1 sensitivity to imatinib, dasatinib and ponatinib but not nilotinib. We conclude that BCR-ABL1 oncoproteins displaying uncommon breakpoints involving the DC2 and SH3 domains are successfully inhibited by nilotinib treatment.

Characterization of p190-Bcr-Abl chronic myeloid leukemia reveals specific signaling pathways and therapeutic targets

The oncogenic protein Bcr-Abl has two major isoforms, p190^Bcr-Abl and p210^Bcr-Abl. While p210^Bcr-Abl is the hallmark of chronic myeloid leukemia (CML), p190^Bcr-Abl occurs in the majority of Philadelphia-positive acute lymphoblastic leukemia (Ph + ALL) patients. In CML, p190^Bcr-Abl occurs in a minority of patients associating with distinct hematological features and inferior outcomes, yet the pathogenic role of p190^Bcr-Abl and potential targeting therapies are largely uncharacterized. We employed next generation sequencing, phospho-proteomic profiling, and drug sensitivity testing to characterize p190^Bcr-Abl in CML and hematopoietic progenitor cell line models (Ba/f3 and HPC-LSK). p190^Bcr-Abl CML patients demonstrated poor response to imatinib and frequent mutations in epigenetic modifiers genes. In contrast with p210^Bcr-Abl, p190^Bcr-Abl exhibited specific transcriptional upregulation of interferon, interleukin-1 receptor, and P53 signaling pathways, associated with hyperphosphorylation of relevant signaling molecules including JAK1/STAT1 and PAK1 in addition to Src hyperphosphorylation. Comparable to p190^Bcr-Abl CML patients, p190^Bcr-Abl cell lines demonstrated similar transcriptional and phospho-signaling signatures. With the drug sensitivity screening we identified targeted drugs with specific activity in p190^Bcr-Abl cell lines including IAP-, PAK1-, and Src inhibitors and glucocorticoids. Our results provide novel insights into the mechanisms underlying the distinct features of p190^Bcr-Abl CML and promising therapeutic targets for this high-risk patient group.

A Case of Childhood Blastic Phase Chronic Myeloid Leukemia With Minor BCR-ABL

Chronic myeloid leukemia (CML) is commonly associated with major BCR-ABL transcript. We present a child with blastic phase CML associated with minor BCR-ABL transcript without prior CML diagnosis. Diagnosis was achieved by fluorescence in situ hybridization of peripheral blood neutrophils, which identified 90% as BCR-ABL positive. The patient received chemotherapy with imatinib followed by dasatinib and underwent reduced-intensity hematopoietic allogeneic stem cell transplantation with prophylactic posttransplant dasatinib for 2 years and has remained in complete molecular remission. Our intensified treatment regimen was effective compared with previous studies on minor BCR-ABL CML describing inferior outcomes with tyrosine kinase inhibitor therapy.

T-cell blast crisis of chronic myelogenous leukemia presented with coexisting p210 and p190 BCR-ABL transcripts and t(10;11)(q11;p15)

Background

Blast transformation of chronic myelogenous leukemia (CML) to T lymphoblastic lymphoma/acute lymphoblastic leukemia (T‐LBL/ALL) is rare, and the molecular mechanism is still unclear.

Case report

A 28‐year‐old woman who developed T‐ALL with coexpressing both p210 and p190 BCR‐ABL transcripts five years after the initial diagnosis of CML in chronic phase. The proliferation of bone marrow was extremely active with blast cells over 20%. Chromosome analysis revealed t(9;22)(q34;q11) and t(10;11)(q25;p15). Flow immunophenotyping showed that blasts expressed CD4, CD7, CD11b, CD38, CD34, CD33, and cCD3.

Conclusion

It is the first T‐cell blast of CML case with coexisting p210 and p190 as well as additional chromosome translocations. Through review this case and previous reports, we will reveal that CML patients with T‐lymphocyte transformation depend on potential molecular and pathological mechanism.

How I investigate basophilia in daily practice

Basophilia is a rare disorder of the complete blood count (CBC) and its management in daily practice remains unclear. Two main factors explain this situation. On the one hand, the reliability of the basophil count is insufficient, whether it is performed by a microscopic slide examination or by a hematology analyser. On the other hand, our knowledge of conditions associated with basophilia is largely based on few case reports and on reviews that refer to older reviews. The association between basophilia and myeloid neoplasm, especially chronic myeloid neoplasm, is well established. Conversely, there are conflicting data on some benign medical conditions and it remains unclear where basophilia may be present. In this review, we have investigated the medical literature to define which medical conditions can lead to basophilia and which cannot, and we propose a practical approach to manage basophilia divided into 3 steps. First, we have to check the real existence of the basophilia by getting rid of spurious basophilia. Then, we have to look for symptoms that suggest reactive basophilia and for clue of a neoplastic cause. Finally, in case of suspicion of a myeloid neoplasm or persistence of the basophilia in the absence of a reactive cause, we have to decide which examinations need to be prescribed to confirm a neoplastic basophilia.

Chronic Myeloid Leukemia With P190 BCR-ABL Translocation and Persistent Moderate Monocytosis: A Case Report

Chronic myeloid leukemia (CML) with p190 BCR-ABL is rare. In some cases it is associated with peripheral monocytosis, while bone marrow shows features intermediate between CML and chronic myelomonocytic leukemia. The prognosis is controversial, but in the most recent literature p190 BCR-ABL CML seems associated with a poor outcome. We report a case of p190 BCR-ABL CML characterized by moderate monocytosis, without deep molecular response (DMR) to an initial imatinib treatment. After imatinib was replaced by dasatinib, a DMR was achieved, however without appreciable effects on monocytosis.

Childhood chronic myeloid leukemia with monocytosis

We report two cases of chronic myeloid leukemia (CML) in childhood presenting with monocytosis. History, physical examination and laboratory findings were in favor of juvenile myelomonocytic leukemia in both the cases, but reverse transcriptase polymerase chain reaction (RT-PCR) detected b2a2 and b3a2 transcript of p210 bcr-abl protein characteristic of major BCR breakpoint. Presence of monocytosis in early childhood suggests a viral infection or JMML but a possibility of CML with monocytosis needs to be considered.

Chronic myeloid leukemia (CML) with P190 BCR-ABL: analysis of characteristics, outcomes, and prognostic significance

The most common BCR-ABL transcripts in chronic myeloid leukemia (CML) are e13a2(b2a2) and e14a2(b3a2). Other transcripts such as e1a2 are rare and their outcome with tyrosine kinase inhibitors (TKI) therapy is undefined. We analyzed 1292 CML patients and identified 14 with only e1a2 transcripts, 9 in chronic phase (CP), 1 in accelerated phase (AP), and 4 in blast phase (BP). Of the CP, 4 achieved complete hematologic response (CHR); 2, complete cytogenetic response (CCyR); 2, partial cytogenetic response (PCyR), and 1 did not respond to imatinib. Five patients progressed to myeloid BP (3), lymphoid BP (1), or AP (1). The AP patient received various TKIs sequentially and achieved only CHR. BP patients received hyper-CVAD (hyperfractionated cyclophosphamide, vincristine, adriamycin, dexamethasone) plus imatinib/dasatinib or idarubicin plus cytarabine (Ara-C); 2 did not respond, 1 had CCyR, and 1 short-lasting complete molecular response (CMR). Overall, cytogenetic responses lasted 3 to 18 months; only 2 achieved major molecular response (MMR) on TKI. P190(BCR-ABL) CML is rare and is associated with an inferior outcome to therapy with TKI. These patients need to be identified as high-risk patients.

First and second line imatinib treatment in chronic myelogenous leukemia patients expressing rare e1a2 or e19a2 BCR–ABL transcripts

During the formation of the Philadelphia (Ph) chromosome, in the majority of chronic myelogenous leukemia (CML) patients, the chromosome 22 breakpoint is located in the major breakpoint cluster region of the BCR gene (M-bcr). Minor and micro breakpoint cluster regions (m-bcr with e1a2 transcript and micro-bcr with e19a2 transcript) are rarely affected and have been suggested to be associated with peculiar CML phenotypes. Despite the different clinical characteristics, it is currently not established, whether different therapeutic options are preferably recommended for the treatment of e1a2 or e19a2 CML. Here we report two patients with e1a2 and one patient with e19a2 translocations, treated with different approaches including imatinib. First and second line imatinib treatments induced haematologic response in all of the three patients, and major cytogenetic response in one patient with e1a2, as well as in the patient with e19a2 CML. However, relapse occurred in the patient with e19a2 CML, possibly caused by the presence of additional chromosomal abnormalities such as an extra Ph chromosome, and loss of chromosome Y. Stem cell transplantation (SCT) therapy caused complete haematologic response with molecular remission; however, the patient died of infectious complication. We conclude that in patients with rare BCR-ABL variants, the effectiveness of imatininb treatment may be influenced by the CML stage besides the actual molecular type of the rare transcript. However, this conclusion cannot be generalized to larger patient groups with rare BCR-ABL variants for which further studies may be needed.

Lineage involvement in chronic myeloid leukaemia: comparison between MBCR/ABL+ and mBCR/ABL+ cases

The relationship between different Abelson/breakpoint cluster region (BCR/ABL+) gene rearrangements and the involvement of different haematopoietic cell lineages were investigated in 15 chronic myeloid leukaemia patients. Analysis of purified cell populations confirmed the involvement of the neutrophil (89%), monocytic (89%), eosinophil (88%), erythroid (100%), and CD34(+) cells (100%) in virtually all patients, without differences between minor BCR/ABL+ and major BCR/ABL+ cases; BCR/ABL+ B- and natural killer (NK)-cells were detected in 43% and 31% of cases, respectively, whereas BCR/ABL+ T-cells were rare (7%). All three minor BCR/ABL+ patients showed involvement of both B- and NK-cells, which was infrequent (27%, P = 0.06 and 10%, P = 0.01) among major BCR/ABL+ cases.

A child with Philadelphia positive (Ph+)-acute leukemia with myeloid morphology: one case of stem cell origin

Philadelphia positive (Ph+) acute myeloid leukemia (AML) is a rare and heterogeneous condition, mainly reported in adults, associated to poor prognosis and unfavorable response to therapy. Here we report clinical and laboratory findings in an 8-year-old patient diagnosed with Ph+ acute leukemia with myeloid (FAB M4) morphology. The patient consistently expressed variable levels of m-bcr, e1a2 transcripts during a 42-month follow-up after two different stem cell transplantation protocols. An immunophenotypic switch was documented, from a mixed, myeloid-lymphoid lineage to a full lymphoid phenotype following stem cell transplants, in association with an immature B-cell gene rearrangement profile and clonal instability during clinical progression. This report indicates a stem cell origin as previously suggested for Ph+ AML.