The relationship between the type of bcr-abl hybrid messenger RNA and thrombopoiesis in Philadelphia-positive chronic myelogenous leukemia

Acquired Factor V Deficiency: A New Cause of Bleeding in Patients with Chronic Myeloid Leukemia and Extreme Leukocytosis

Bleeding complications in patients with myeloproliferative neoplasms are known to be related to acquired von Willebrand disease or platelet dysfunction. Here, we describe two very similar cases of chronic phase chronic myeloid leukemia with extreme leukocytosis (>500,000/mcL) and deep tissue bleeding after a minor trauma, who had increased PT and PTT, normal VWF antigen and activity. The patients were found to have acquired factor V deficiency. Factor V deficiency as a cause of bleeding in patients with uncontrolled chronic myeloid leukemia has not yet been reported. Bleeding resolved after correction of hyperleukocytosis, and FV level improved. We conclude that acquired FV deficiency is possible in patients with uncontrolled chronic myeloid leukemia and extreme leukocytosis.

Improvement of platelet dysfunction in chronic myelogenous leukemia following treatment with imatinib: a case report

Introduction

In patients with chronic myeloid leukemia, tyrosine kinase inhibitors suppress the BCR-ABL⁺ clone and often induce complete molecular remissions. Megakaryocytes in such patients have been shown to be derived from the BCR-ABL⁺ clone, and abnormal platelet function is frequent in chronic myeloid leukemia. However, little is known about the influence of modern targeted therapy on chronic myeloid leukemia-associated platelet disorders.

Case presentation

We report the case of a massive hemorrhage in a 32-year-old Caucasian man caused by chronic myeloid leukemia-associated platelet dysfunction, which improved after treatment with imatinib.

Conclusion

This report demonstrates that platelet dysfunction and bleeding disorder in BCR-ABL⁺ chronic myeloid leukemia can successfully be treated with imatinib. We suggest the monitoring of platelet function in future studies using imatinib to treat patients with chronic myeloid leukemia.

Chronic Myelogenous Leukemia: From Molecular Biology to Clinical Aspects and Novel Targeted Therapies

The critical causative event in chronic myelogenous leukemia (CML) is the fusion of the head of the bcr gene with the body of the abl gene, named bcr/abl gene. This chimeric BCR/ABL molecule transforms primary myeloid cells to leukemic cells and induces a CML-like disease in mice. The mouse CML model expressing the BCR/ABL molecule has provided important new insights into the molecular pathophysiology of CML and has directly answered many questions regarding this disease. Furthermore, numerous clinical studies have demonstrated a correlation between leukemic clinical features and the position of the breakpoint in the BCR gene of the chimeric BCR/ABL gene. Understanding of the molecular pathogenesis of CML has led to the development of several novel therapies. The BCR/ABL molecule is unique oncogeneiety, having ABL tyrosine kinase activity, making it an ideal target for drug development. Subsequent clinical studies now realize the hypothesis that selective inhibition of the abl tyrosine kinase activity using imatinib mesylate might be useful for the treatment of CML. This article reviews the history of BCR/ABL molecular biology, including the CML model mouse, clinical molecular studies and the recent findings of imatinib mesylate and more potent tyrosine kinase inhibitors developed for the treatment of CML.

The possible influences of B2A2 and B3A2 BCR/ABL protein structure on thrombopoiesis in chronic myeloid leukaemia

The Philadelphia chromosome, t(9;22)(q34;q11) gives rise more frequently, in chronic myeloid leukaemia (CML), to two BCR/ABL chimeric transcripts differing only by the absence of 75 nucleotides and defined as b2a2 and b3a2 types, encoding two 210-kDa tyrosine kinase proteins differing only by the absence of 25 amino acids coded by the b3 exon. In the present study the two transcripts, detected by RT-PCR in 88 consecutive unselected CML patients, were correlated with haematological findings at diagnosis and with the megakaryocyte size and frequency by morphometric evaluation of 45 bone marrow biopsies. The secondary structure prediction and hydrophobicity of the b2a2 and b3a2 type BCR/ABL protein were also obtained. The prediction results for the b3 exon amino acids using GOR IV and NnPredict methods showed a short beta strand corresponding to the hydrophobic portion of the peptide. Significantly higher values were found in the platelet count of patients carrying b3a2 transcripts. The megakaryocyte size and frequency in bone marrow biopsies did not show significant differences between the two groups of patients. Stratifying the patients on the basis of white blood cell (WBC) count below or above 100x10(9)/l we still had, in both groups, a significant difference in the platelet count between the b2a2 and b3a2 patients. The possible relationships between the structure of b2a2 and b3a2 types of BCR/ABL fused protein and thrombopoiesis are discussed.

Chronic myeloid leukemia with thrombocythemic onset may be associated with different BCR/ABL variant transcripts

Ph-positive chronic myeloid leukemia (CML) mimicking essential thrombocythemia (ET) at onset seems to be a distinct clinical entity. Whether this rare clinical form of CML is associated with single, specific variants of BCR/ABL transcripts is a matter of debate. Among 82 consecutive patients with Ph-positive CML, we identified 3 patients in which the disease mimicked ET at presentation, because of marked thrombocytosis and moderate leukocytosis, with few immature myeloid cells in peripheral blood and blood basophilia in 2 of them. Molecular analysis with the reverse transcriptase-polymerase chain reaction technique showed the presence of b2a2, b3a2, and b3a2-b2a2 transcript variants in the three patients, respectively. The results of our study together with a review of literature data suggest that different BCR/ABL transcript variants may occur in CML mimicking ET, without an apparently significant prevalence of one type.

Relationship between the type of BCR-ABL rearrangement and bone marrow histopathological features in chronic myeloid leukemia

The aim of the present study was to characterize the type of BCR-ABL transcript and to correlate the molecular feature with bone marrow histology. For this purpose, we analysed the BCR-ABL rearrangement in 26 patients with chronic myeloid leukemia (CML) in the chronic phase by RT-PCR, and we also classified the bone marrow histology according to the predominance of granulocylic (GRAN) or granulocytic and megakaryocytic (GRAM/MEG) proliferation, after analysis of two independent observers. We did not find any significant difference in survival of patients presenting b2-a2 and b3-a2 transcripts or GRAN and GRAN/MEG bone marrow types, nor did we find any significant correlation of the type of BCR-ABL transcript with the bone marrow histological subgroups GRAN and GRAN-MEG (Fisher's test = 0.31). Thus, we conclude that the presence of exon b3 is not correlated to bone marrow histology in CML.

Analysis of molecular breakpoint and m-RNA transcripts in a prospective randomized trial of interferon in chronic myeloid leukaemia: no correlation with clinical features, cytogenetic response, duration of chronic phase, or survival

Two hundred and nineteen cases of Ph+ve CML and 15 Ph-ve, BCR+ve CML cases have been analysed to determine the breakpoint site and its relationship to clinical features, cytogenetic response, duration of chronic phase and survival. 119 cases have had RNA analysis performed to determine the type of BCR/ABL transcript and have also been analysed in a similar way. Presenting features at diagnosis including age, sex, white-cell count and platelet count showed no significant difference for those with 5' and 3' breakpoints and those with either b2a2 or b3a2 BCR/ABL transcripts. However, in a subgroup of patients whose presenting white-cell count was < 100 x 10(9)/l, those with b3a2 transcript did have a significantly higher platelet count. Analysis by Sokal risk grouping showed no difference for 5' or 3' breakpoints but a trend for lower stage among those with b2a2 transcripts. No correlation was found either for genomic breakpoint site or BCR/ABL RNA transcript in terms of duration of chronic phase or survival. When stratified by randomized therapy, either interferon-alpha or standard chemotherapy, no difference was noted in relation to genomic breakpoint site or BCR/ABL transcript. Cytogenetic response was not related to the molecular findings.

Detection by polymerase chain reaction of BCR/ABL transcripts in myeloproliferative diseases at time of diagnosis and for monitoring chronic myelogenous leukaemia patients after bone marrow transplantation

The Philadelphia chromosome t(9;22)(q34;q11) is a cytogenetic marker for chronic myelogenous leukaemia (CML), and is also present in some acute leukaemias. The translocation in CML gives rise to two BCR/ABL chimeric transcripts (b3a2 and b2a2) encoding a 210-kD tyrosine kinase protein. These leukaemia-specific transcripts can be detected easily by the reverse transcriptase polymerase chain reaction (PCR). PCR has improved the possibility of detecting minimal residual leukaemia cells in Ph-positive patients, especially after bone marrow transplantation (BMT). With PCR, we looked for BCR/ABL transcripts in 30 patients with CML and 4 with essential thrombocythaemia at time of diagnosis, finding a significant difference in the platelet counts of CML patients carrying b3a2 or b2a2 transcripts. The BCR/ABL transcript was monitored by PCR in 6 CML patients after BMT. The usefulness of PCR in clinical practice at time of diagnosis, and the biological and clinical significance of positive/negative PCR results, in patients with transplants, are discussed.