DoesBCR/ABL1positive Acute Myeloid Leukaemia Exist?

Rare but authentic Philadelphia-positive acute myeloblastic leukemia: two case reports and a literature review of characteristics, treatment and outcome

The Philadelphia chromosome (Ph+), corresponding to translocation t(9;22), is found in chronic myeloid leukemia (CML) and acute lymphoblastic leukemia. Several cases of Ph+ acute myeloid leukemia (AML) have been reported in the literature. A retrospective study of Ph+ AML between 2001 and 2012 was conducted through a review of the literature. Among 400 AML patients, two cases of Ph+ AML (0.5%) were identified and treated with conventional chemotherapy with or without tyrosine kinase inhibitors (TKIs), followed by allogeneic hematopoietic stem cell transplantation (allo-HSCT). One patient had a complex karyotype including 7 monosomy (-7) and p190 BCR-ABL fusion transcript. Both patients remain in complete molecular remission. To date, 21 Ph+ AML cases treated with TKIs have been described in the literature with a median overall survival of 18months. One-third of the patients had additional karyotypic abnormalities, and 14% had -7. Molecular analysis showed 59% p210 and 41% p190 fusion protein. Relapse rate was observed in 38% of patients with p190 compared to 10% in patients with p210. Allo-HSCT was performed in eight patients; two relapsed (25%). Cytogenetic (-7) and molecular features help to distinguish Ph+ AML from CML. Survival improved with TKIs, particularly in association with conventional chemotherapy and allo-HSCT. Further studies of Ph+ AML patients are needed to better define this entity, its prognostic value, and therapeutic strategy.

Dominant-negative Ikaros cooperates with BCR-ABL1 to induce human acute myeloid leukemia in xenografts

Historically, our understanding of mechanisms underlying human leukemogenesis are inferred from genetically engineered mouse models. Relatively, few models that use primary human cells recapitulate the full leukemic transformation as assayed in xenografts and myeloid transformation is infrequent. We report a humanized experimental leukemia model where xenografts develop aggressive acute myeloid leukemia (AML) with disseminated myeloid sarcomas within 4 weeks following transplantation of cord blood transduced with vectors expressing BCR-ABL1 and a dominant-negative isoform of IKAROS, Ik6. Ik6 induced transcriptional programs in BCR-ABL1-transduced progenitors that contained repressed B-cell progenitor programs, along with strong stemness, proliferation and granulocyte-monocytic progenitor (GMP) signatures-a novel combination not induced in control groups. Thus, wild-type IKAROS restrains stemness properties and has tumor suppressor activity in BCR-ABL1-initiated leukemia. Although IKAROS mutations/deletions are common in lymphoid transformation, they are found also at low frequency in AML that progress from a prior myeloproliferative neoplasm (MPN) state. Our experimental system provides an excellent model to gain insight into these rare cases of AML transformation and the properties conferred by IKAROS loss of function as a secondary mutation. More generally, our data points to the importance of deregulated stemness/lineage commitment programs in human myeloid leukemogenesis.

Characteristics of hematologic malignancies with coexisting t(9;22) and inv(16) chromosomal abnormalities

Background

The coexistence of t(9;22)(q34;q11.2) and inv(16)(p13q22) chromosomal abnormalities is extremely uncommon, and only a small number of such cases have been reported. Here, we characterized 7 cases of hematologic malignancy exhibiting t(9;22) and inv(16) coexistence.

Methods

We reviewed the cytogenetic data for hematologic malignancies treated at the Catholic Blood and Marrow Transplantation Center between January 2004 and June 2013. We identified 7 cases exhibiting t(9;22) and inv(16) coexistence. In addition, we analyzed mutations in the IKZF1, NPM1, FLT3, N-RAS, K-RAS, c-KIT, and TP53 genes.

Results

Four cases of chronic myelogenous leukemia (CML; 1 chronic phase, 2 accelerated phase, and 1 blast phase) and 3 cases of acute myeloid leukemia (AML; 1 de novo and 2 therapy-related) were identified. The percentages of circulating blasts and bone marrow eosinophils were higher in AML cases than in CML cases (53% vs. 5% and 30% vs. 5.5%, respectively). The proportions of each chromosomal abnormality were used along with follow-up karyotyping results to identify secondary changes. In BCR/ABL, a p210 fusion transcript was associated with CML, whereas a p190 fusion transcript was associated with AML. One patient with AML harbored 2 mutations: c-KIT D816V and TP53 E11Q. All patients except 1 with CML blast phase sustained clinical remission after treatment, which included an imatinib mesylate regimen.

Conclusion

This study shows that observations of bone marrow morphology, initial and follow-up cytogenetic studies, and karyotyping of BCR/ABL1 and CBFB/MYH11 provide valuable information for characterizing hematologic malignancies exhibiting t(9;22) and inv(16) coexistence.