AbstractAcute Megakaryoblastic Leukemia Research Articles

Abstract P02: Uncovering Tailored Therapies for Acute Myeloid Leukemia in Children with Down Syndrome

Abstract P02: Uncovering Tailored Therapies for Acute Myeloid Leukemia in Children with Down Syndrome

A Rare Pediatric Case Report With Review of Literature for the Diagnosis of Acute Megakaryoblastic Leukemia (FAB M7)

Acute megakaryoblastic leukemia (AMKL) is a subtype of acute myeloid leukemia (AML) accounting for 3%–10% of primary AML in childhood. Clinical manifestations of AML patients can include low grade of fever, diarrhea, easy bruising, failure to growth, and life-threatening clinical manifestations. Laboratory tests are very crucial to make a definitive diagnosis and treatment. We report here an uncommon case of AMKL in a 12-month-old boy who presented with general paleness and fatigue. Based on blood film investigation, bone marrow examination report, and immunophenotyping, he was diagnosed as a case of AMKL without Down syndrome.

Hematopoietic Cell Transplantation for Children with Acute Megakaryoblastic Leukemia without Down Syndrome

Abstract Acute megakaryoblastic leukemia (AMKL) accounts for 10% of childhood acute myeloid leukemia. Although AMKL patients with Down syndrome (DS-AMKL) have an excellent survival rate, patients with non-DS-AMKL experience poor outcomes. Despite therapeutic advances, including use of intensified treatment protocols, there is no consensus on the optimal treatment strategy for non-DS-AMKL. Some study groups recommend hematopoietic cell transplantation (HCT) for patients with non-DS-AMKL in the first complete remission (CR1); however, it is unclear whether HCT in CR1 improves outcomes of these patients. To assess outcomes and risk factors of HCT for patients with non-DS-AMKL, we retrospectively analyzed 203 patients with non-DS-AMKL (male, 95; female, 108) who underwent first HCT between 1986 and 2015 using data from the Japan Society for Hematopoietic Cell Transplantation. The median age at the time of HCT was 2 years (range, 0-16). Out of 203 patients, 12 had translocation t(1;22)(p13;q13), 18 had monosomy 7, 21 had complex karyotype, and 109 had other chromosomal abnormalities. Bone marrow transplantation (BMT) was performed for 114, cord blood transplantation (CBT) for 74, and peripheral blood stem cell transplantation (PBSCT) for 15 patients. Seventy-eight patients underwent HCT from related (HLA-matched, 43; HLA-mismatched, 35), 108 from unrelated (HLA-matched, 56; HLA-mismatched, 52), and 17 from autologous donors. Ninety-two patients underwent HCT in CR1, 21 in the second CR (CR2), and 90 in non-CR. Myeloablative conditioning (MAC) regimen was defined as the use of total body irradiation (TBI) ≥8 Gy, administration of busulfan >8 mg/kg or melphalan >140 mg/m2. All other regimens were included in reduced intensity conditioning (RIC) regimen. MAC regimen was used for 192 and RIC regimen for 11 patients. Median duration of follow-up after HCT was 713 days (range, 3-10008). Out of 203 patients, 183 (90%) exhibited engraftment. Sixteen out of 20 patients who did not exhibit engraftment underwent HCT in non-CR. In the entire cohort, 5-year overall survival (OS) and event free survival (EFS) rates were 43% and 38%, respectively. Seventy-two patients died of disease relapse and 42 died of transplantation-related complications. Five-year OS/EFS rates were not significantly different between BMT (48%/43%), CBT (35%/31%), and PBSCT (31%/27%) (p = 0.221/p = 0.087). In allogeneic HCT, 5-year OS/EFS rates were significantly lower in patients who underwent HCT from HLA-mismatched donors (27%/22%) than those from HLA-matched donors (52%/47%) (p < 0.001/p < 0.001). Five-year cumulative incidence (CI) of relapse after HLA-mismatched HCT (64%) was significantly higher than that after HLA-matched HCT (45%) (p = 0.006). Five-year OS/EFS rates were not significantly different between patients with translocation t(1;22)(p13;q13) (50%/42%), those with monosomy 7 (65%/59%), and those with complex karyotype (61%/52%) (p = 0.094/p = 0.111). Five-year OS/EFS rates of patients who underwent HCT in CR1 (72%/64%) were significantly higher than those of patients who underwent in CR2 (23%/13%) and non-CR (16%/16%) (p < 0.001/p < 0.001). Five-year CI of relapse was significantly lower in CR1 (28%) than in CR2 (73%) and non-CR (73%) (p < 0.001). Five-year non-relapse mortality was significantly higher in non-CR (27%) than in CR1 (15%) and CR2 (14%) (p = 0.022). Among the 92 patients who underwent HCT in CR1, 3-year CI of relapse in patients who received RIC (67%) was significantly higher than that in patients who received MAC regimen (25%) (p = 0.021). Five-year OS/EFS rates associated with HCT from HLA-mismatched (70%/63%) and HLA-matched donors (77%/59%) were not significantly different (p = 0.609/p = 0.761). In the multivariate analysis for 5-year OS, HCT in CR2 and non-CR was found to be a significant risk factor (hazard ratio, 5.16; 95% CI, 3.36-7.92; p < 0.001). In conclusion, multivariate analysis confirmed that HCT in CR1 was a good prognostic factor for 5-year OS. Risk stratification in patients with non-DS-AMKL should be established to determine the indication for HCT in CR1. Disclosures No relevant conflicts of interest to declare.

Abstract 4867: Identification of an inv(16)-encoded CBFA2T3-GLIS2 fusion protein in 34% of non-infant acute megkaryoblastic leukemias: A report from the Pediatric Cancer Genome Project

Abstract Acute Megakaryoblastic Leukemia (AMKL) accounts for ∼10% of childhood acute myeloid leukemia (AML). Although AMKL patients with Down syndrome (DS-AMKL) have an excellent 5 year event-free survival (EFS), non-DS-AMKL patients have an extremely poor outcome with a 3 year EFS < 40%. To define the landscape of mutations that occur in non-DS-AMKL, we performed transcriptome sequencing on diagnostic blasts from 14 cases. Our results identified chromosomal rearrangements resulting in the expression of novel fusion transcripts in 12/14 cases. Remarkably, in 7/14 cases, we detected an inversion on chromosome 16 [inv(16)(p13.3;q24.3)] that resulted in the juxtaposition of CBFA2T3, a member of the ETO family of transcription factors, next to GLIS2 resulting in a CBFA2T3-GLIS2 chimeric gene encoding an in frame fusion protein. GLIS2 is a member of the GLI family of transcription factors that mediate sonic hedgehog (SHH) signaling and has been demonstrated to play a role in regulating expression of GLI target genes. Evaluation of a recurrency cohort of 52 samples including 24 additional pediatric cases and 28 adult cases revealed 6 additional pediatric samples carrying the fusion for an overall frequency of 34% in pediatric AMKL. To gain insight into the mechanism whereby CBFA2T3-GLIS2 promotes leukemogenesis, we introduced the fusion into murine hematopoietic cells and assessed its effect on in vitro colony replating as a surrogate measure of self-renewal. Cells transduced with a mCherry expressing retrovirus failed to form colonies after the 2nd replating. By contrast, expression of either wild-type GLIS2 or CBFA2T3-GLIS2 resulted in a marked increase in the self-renewal capacity, with colony formation persisting through 12 replatings. Immunophenotypic analysis of the CBFA2T3-GLIS2 expressing colonies revealed evidence of megakaryocytic differentiation. GLI transcription factors modulate expression of multiple downstream targets including components of BMP, WNT, and SHH pathways. To interrogate these pathways as potential contributors to the enhanced self-renewal capacity, we conducted luciferase reporter assays and found that CBFA2T3-GLIS2 functioned as a strong activator of the BMP responsive element. Furthermore, expression of CBFA2T3-GLIS2 in Drosophila resulted in ectopic expression of endogenous dpp, the fly homolog of BMP4, and conferred a dpp gain of function phenotype. Taken together these data identify a novel inv(16)-encoded CBFA2T3-GLIS2 fusion protein as a recurrent driver mutation in ∼35% of non-infant pediatric non-DS-AMKLs. The alteration of a key transcriptional regulator within the SHH signaling pathways in a substantial percentage of pediatric AMKL raises the possibility that inhibition of this pathway or downstream activated pathways may have a therapeutic benefit in this aggressive form of AML. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4867. doi:1538-7445.AM2012-4867

De novo acute megakaryoblastic leukemia with p210 BCR/ABL and t(1;16) translocation but not t(9;22) Ph chromosome

Acute megakaryoblastic leukemia (AMKL) is a type of acute myeloid leukemia (AML), in which majority of the blasts are megakaryoblastic. De novo AMKL in adulthood is rare, and carries very poor prognosis. We here report a 45-year-old woman with de novo AMKL with BCR/ABL rearrangement and der(16)t(1;16)(q21;q23) translocation but negative for t(9;22) Ph chromosome. Upon induction chemotherapy consisting of homoharringtonine, cytarabine and daunorubicin, the patient achieved partial hematological remission. The patient was then switched to imatinib plus one cycle of CAG regimen (low-dose cytarabine and aclarubicin in combination with granulocyte colony-stimulating factor), and achieved complete remission (CR). The disease recurred after 40 days and the patient eventually died of infection. To the best of our knowledge, this is the first report of de novo AMKL with p210 BCR/ABL and der(16)t(1;16)(q21;q23) translocation but not t(9;22) Ph chromosome.

Target cell of leukemic transformation in acute megakaryoblastic leukemia

Acute megakaryoblastic leukemia (AMkL) is a newly defined acute leukemia in which the differentiation of proliferating blasts is arrested at the megakaryocytic precursor stage. In order to clarify whether a target cell of leukemic transformation in AMkL is a cell committed to megakaryocytic lineage, or a multipotential stem cell, we examined AMkL patients with regard to: a) the presence of myelodyplastic features in residual erythroid and granulocytic cells, b) coexistence of myeloperoxidase (MPO)-positive blasts with megakaryoblasts, and c) the presence of the same chromosomal abnormality in erythroid and granuloid colony-forming cells as seen in megakaryoblasts. Regarding the former two items, results were compared with those from megakaryoblastic crisis of chronic myelocytic leukemia (CML-MkBC) and transient myeloproliferative disorder in Down syndrome (DS-TMD), which are thought to be multipotential stem cell disorders. Among 18 patients with AMkL, three, all complicating myelofibrosis, had marked myelodysplastic changes of erythroid series and/or granulocytic series. In 4 out of 7 patients with CML-MkBC, 5 out of 8 patients with DS-TMD, and 7 out of 18 patients with AMkL, MPO-positive blasts, even though rare, were observed in addition to PPO-positive blasts. All except one of these patients with AMkL also showed complicating myelofibrosis. In one case of AMkL with myelofibrosis, chromosomal analysis of cultured cells of individual colonies revealed that all the analysable metaphases from both CFU-GM and BFU-E had the same chromosomal abnormality as megakaryoblasts. This study has clarified that a considerable proportion of AMkL cases, particularly those with complicating myelofibrosis or showing acute myelofibrosis, arise against the background of a multipotential stem cell disorder, even if blasts are exclusively megakaryocytic in phenotype.

Acute Megakaryoblastic Leukemia in Children Identified by Immunological Marker Studies

Acute megakaryoblastic leukemia (AMkL), defined by the presence of the platelet-associated glycoprotein IIb/IIIa complex on malignant cells, was diagnosed in 4 (4%) of 103 consecutive children with untreated acute leukemia or 4 (21%) of 19 children with acute nonlymphoblastic leukemia (ANLL). Particular features in the four children with AMkL were an age below 12 months at diagnosis (two patients), the absence of a significant hepatosplenomegaly (three patients), a leukocyte count below 20 x 10(9)/L with only a few blast cells in the peripheral blood (four patients), a technically difficult bone marrow aspiration (three patients), the presence of many megakaryocytes in marrow particles (two patients), and an inconclusive cytochemistry (four patients). The four children with AMkL were treated according to protocols for ANLL and a complete remission was obtained in all patients. One patient died from relapse after 3 months, one patient is a long-term survivor (38+ months), and two patients still on chemotherapy are disease-free for 11+ and 13+ months.

Myeloperoxidase-Positive Acute Megakaryoblastic Leukemia

Acute megakaryoblastic leukemia (FABM7) is an unusual but well recognized form of acute myelogenous leukemia in which the bone marrow blast cells are phenotypically recognized by the demonstration of cytoplasmic platelet peroxidase or surface staining for the IIb/IIIa platelet-specific glycoprotein. Herein, the authors report a case of acute megakaryoblastic leukemia that satisfies the accepted French-American-British criteria and in which the blast cells also exhibit evidence of myeloid differentiation, including surface MY7 (CD13) by flow cytometry and immunocytochemical positivity for myeloperoxidase. These findings suggest that megakaryoblasts may be closely related to myelomonoblasts, that they have the potential to partially differentiate along multiple phenotypic lines, and that aberrant phenotypes can occur that do not correspond to known stages of normal maturation. The authors illustrate the difficulty in classification of these aberrant phenotypes by standard cytochemical and morphologic criteria.