Chronic Myeloid Leukemia with an e6a2 BCR-ABL1

A minority of chronic myeloid leukemia patients (CML) express a variety of atypical BCR-ABL1 fusion variants and, of these, the e6a2 BCR-ABL1 fusion is generally associated with an aggressive disease course. Progression of CML to blast crisis is associated with acquisition of additional somatic mutations yet these events have not been elucidated in patients with the e6a2 BCR-ABL1 genotype. Moreover, molecular monitoring is only sporadically performed in CML patients with atypical BCR-ABL1 fusion transcripts due to lack of consensus approaches or standardization. A case of CML is described in which comprehensive molecular analysis, including targeted next-generation sequencing, revealed a single ASXL1 mutation cooperating with an e6a2 BCR-ABL1 fusion transcript at blast crisis. A quantitative molecular monitoring approach was devised and adopted that reflected the disease response from initial treatment through allogeneic stem cell transplantation which resulted in undetectable e6a2 BCR-ABL1 transcripts. This case emphasizes the requirement for molecular monitoring in CML patients with atypical BCR-ABL1 fusion transcripts and emphasizes that comprehensive sequencing has the potential to identify targets for novel therapies in CML patients with advanced disease

Allogeneic Hematopoietic Stem Cell Transplantation for a BCR-FGFR1

Hematopoietic myeloproliferative neoplasms (MPNS) with rearrangements of the receptor tyrosine kinase FGFR1 gene, located on chromosome 8p11, are uncommon and associated with diverse presentations such as atypical chronic myeloid leukemia, acute myeloid leukemia, or an acute T- or B-lymphoblastic leukemia, reflecting the hematopoietic stem cell origin of the disease. A review of MPN patients with the t(8;22) translocation that results in a chimeric BCR-FGFR1 fusion gene reveals that this disease either presents or rapidly transforms into an acute leukemia that is generally unresponsive to currently available chemotherapeutic regimens including tyrosine kinase inhibitors (TKIS). The first case of a rare BCR-FGFR1 MPN presenting in a B-acute lymphoblastic phase who underwent allogeneic hematopoietic stem cell transplantation (HSCT) with a subsequent sustained complete molecular remission is described. Allogeneic HSCT is currently the only available therapy capable of achieving long-term remission in BCR-FGFR1 MPN patients

Impact of prior JAK-inhibitor therapy with ruxolitinib on outcome after allogeneic hematopoietic stem cell transplantation for myelofibrosis: a study of the CMWP of EBMT.

JAK1/2 inhibitor ruxolitinib (RUX) is approved in patients with myelofibrosis but the impact of pretreatment with RUX on outcome after allogeneic hematopoietic stem cell transplantation (HSCT) remains to be determined. We evaluated the impact of RUX on outcome in 551 myelofibrosis patients who received HSCT without (n = 274) or with (n = 277) RUX pretreatment. The overall leukocyte engraftment on day 45 was 92% and significantly higher in RUX responsive patients than those who had no or lost response to RUX (94% vs. 85%, p = 0.05). The 1-year non-relapse mortality was 22% without significant difference between the arms. In a multivariate analysis (MVA) RUX pretreated patients with ongoing spleen response at transplant had a significantly lower risk of relapse (8.1% vs. 19.1%; p = 0.04)] and better 2-year event-free survival (68.9% vs. 53.7%; p = 0.02) in comparison to patients without RUX pretreatment. For overall survival the only significant factors were age > 58 years (p = 0.03) and HLA mismatch donor (p = 0.001). RUX prior to HSCT did not negatively impact outcome after transplantation and patients with ongoing spleen response at time of transplantation had best outcome

Myelodysplastic Syndrome/Acute Myeloid Leukemia Arising in Idiopathic Erythrocytosis

The term “idiopathic erythrocytosis (IE)” is applied to those cases where a causal clinical or pathological event cannot be elucidated and likely reflects a spectrum of underlying medical and molecular abnormalities. The clinical course of a patient with IE is described manifesting as a persistent erythrocytosis with a low serum erythropoietin level, mild eosinophilia, and with evidence of a thrombotic event. The patient subsequently developed a myelodysplasic syndrome (MDS) and acute myeloid leukemia (AML), an event not observed in erythrocytosis patients other than those with polycythemia vera (PV). Application of a next-generation sequencing (NGS) approach targeted for myeloid malignancies confirmed wild-type JAK2 exons 12–15 and identified a common SH2B3 W262R single-nucleotide polymorphism associated with the development of hematological features of myeloproliferative neoplasms (MPNs). Further NGS analysis detected a CBL L380P mutated clone expanding in parallel with the development of MDS and subsequent AML. Despite the absence of JAK2, MPL exon 10, or CALR exon 9 mutations, a similarity with the disease course of PV/MPN was evident. A clonal link between the erythrocytosis and AML could be neither confirmed nor excluded. Future molecular identification of the mechanisms underlying IE is likely to provide a more refined therapeutic approach

BCR-ABL Kinase Domain Mutations & SNPs in Imatinib Resistant or Intolerant Chronic Myeloid Leukaemia Patients.

Abstract The Philadelphia chromosome, is formed as a result of a reciprocal translocation between chromosomes 9 and 22 and results in the formation of the hybrid oncoprotein BCR-ABL which is pathognomic of Chronic Myeloid Leukaemia (CML). Imatinib Mesylate (IM), a tyrosine kinase inhibitor that specifically binds BCR-ABL in its inactive conformation and functions as a competitive inhibitor of ATP binding, has revolutionized therapy for patients with CML. However, resistance develops in a significant proportion of cases and is predominantly mediated by single base-pair substitutions within the BCR-ABL kinase domain leading to changes in the amino acid composition and conformational changes in the kinase domain that inhibit IM binding whilst retaining BCR-ABL phosphorylation capacity. Second generation tyrosine kinase inhibitors such as Dasatinib and Nilotinib retain activity in IM-resistant patients due to less stringent binding requirements and represent viable alternatives for IM-resistant or intolerant CML patients. In this study, we undertook to examine the molecular mechanisms underlying IM resistance. A cohort of 33 patients with either primary or acquired resistance (n=31) to IM or intolerance to IM (n=2) was identified by persistently high or increasing levels of BCR-ABL transcripts determined by standardised real-time quantitative PCR. An initial allele-specific PCR screen was used to sensitively detect the clinically significant T315I mutation, which renders patients insensitive to currently available tyrosine kinase inhibitors: four (11.8%) IM resistant/intolerant patients were T315I positive. To further characterise the molecular mechanisms of mutation induced resistance, the BCR-ABL kinase domain was then screened for the presence of a mutation using a sensitive denaturing high performance liquid chromatography (dHPLC) approach. dHPLC can detect a single base pair substitution within the BCR-ABL kinase domain based on hybridization to a non-mutated wild type control. Mutated samples display reduced hybridization capacity to the dHPLC column and elute at an earlier time-point. Sensitivity of dHPLC (0.1–10%) is significantly greater than that of sequencing (15–25%). Following dHPLC analysis, samples showing evidence of mutation were examined by direct sequencing to identify the mutation(s) present. Kinase domain mutations have been identified in 18 of the 33 (55%) patients examined to date and these include p-loop mutations (M244V, G250E, Q252H), IM-binding domain mutations (T315I &amp; F317L), catalytic domain mutations (M351T &amp; E355G), and an activation-loop mutation (L387M). Three previously unreported mutations that may be associated with IM resistance (T267A, L273M, K291Q) were identified. The L273M positive patient also has an M244V mutation and has shown primary resistance to IM &amp; is currently being treated with Nilotinib; the T267A patient has rising BCR-ABL transcripts, while the K291Q patient has had a 3 log reduction of BCR-ABL transcripts following IM dose escalation. In addition to the above mutations, 2 SNPs were identified at E275E and at L248L, which may not be clinically relevant. The identification of clinically significant mutations facilitates selection of alternative approaches to therapy such as IM dose escalation, second generation tyrosine kinase inhibitors or allogeneic stem cell transplantation, if eligible, allowing patient specific approaches to therapy.</jats:p