Cryptic and atypical KMT2A-USP2 and KMT2A-USP8 rearrangements identified by mate pair sequencing in infant and childhood leukemia.

Infant leukemias are a rare group of neoplasms that are clinically and biologically distinct from their pediatric and adult counterparts. Unlike leukemia in older children where survival rates are generally favorable, infants with leukemia have a 5-year event-free survival rate of <50%. The majority of infant leukemias are characterized by KMT2A (MLL) rearrangements (~70 to 80% in acute lymphoblastic leukemia), which appear to be drivers of early leukemogenesis. In this report, we describe three cases: a 9-month-old female infant with B-acute lymphoblastic leukemia (B-ALL), an 8-month-old female presenting with B/myeloid mixed phenotype acute leukemia (MPAL), and a 16-month-old male with B-ALL. The first case had a normal karyotype and B-ALL FISH results consistent with an atypical KMT2A rearrangement. The second case had trisomy 10 as the sole chromosomal abnormality and a normal KMT2A FISH result. Case 3 had trisomy 8 and a t(11;15)(q23;q21), an atypical KMT2A rearrangement by FISH studies, and a focal deletion of 15q with a breakpoint within the USP8 gene by chromosomal microarray. Mate pair sequencing was performed on all three cases and identified a KMT2A-USP2 rearrangement (cases 1 and 2) or a KMT2A-USP8 rearrangement (case 3). These recently characterized KMT2A fusions have been described exclusively in infant and pediatric leukemia cases where the incidence varies vary according to leukemia subtype, are considered high-risk, with a high incidence of central nervous system involvement, poor response to initial prednisone treatment, and poor event free survival. Additionally, approximately half of cases are unable to be resolved using standard cytogenetic approaches and are likely under recognized. Therefore, targeted molecular approaches are suggested in genetically unresolved infant leukemia cases to characterize these prognostically relevant clones.

Multiple cells of origin in common with various types of mouse N-Myc acute leukemia.

Little is known regarding whether the cell of origin differs among different leukemia types. To address this fundamental issue, we determined the cell of origin in five distinct types of acute leukemia induced by N-Myc overexpression in mice. CD150+CD48-CD41-CD34-c-Kit+Sca-1+Lin- (KSL) (HSC1) cells, CD150-CD48-CD41-CD34-KSL (HSC2) cells, CD150+CD41+CD34-KSL (HPC1) cells, CD150+CD41+CD34+KSL (HPC2) cells, and CD150-CD41-CD34+KSL (HPC3) cells were purified from the bone marrow of adult C57BL/6 mice, transduced with the N-Myc retrovirus vector, and transplanted into lethally irradiated mice. B-cell acute lymphoblastic leukemia (B-ALL), T-cell acute lymphoblastic leukemia (T-ALL), acute myeloid leukemia (AML), acute undifferentiated leukemia (AUL), and mixed phenotype acute leukemia (MPAL) developed from five populations. RNA sequencing data supported the phenotypical diagnoses of leukemia, except that AUL appeared transcriptionally close to T-ALL. Whole-genome sequencing revealed that retroviral integration sites were irrelevant to the leukemia types and that T-ALL and AML of MPAL shared the same integration site and many gene mutations, suggesting their common origin. Additionally, leukemic stem cells were identified in the KSL cell population, suggesting that the phenotypes of leukemic stem cells are irrelevant to leukemia types. This study provides experimental evidence for the similar and multiple cells of origin in acute leukemia.

Mixed phenotype acute leukemia in a child associated with a NUP98-NSD1 fusion and NRAS p.Gly61Arg mutation.

BACKGROUND: Mixed phenotype acute leukemia (MPAL) is a rare subset of acute leukemia in the pediatric population associated with genetic alterations seen in both acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML). CASE: We describe a patient with MPAL with a NUP98 (nucleoporin 98)-NSD1 gene fusion (nuclear receptor binding SET domain protein1) and NRAS (neuroblastoma RAS viral oncogene homolog mutation) p.Gly61Arg mutation who was treated with upfront AML-based chemotherapy, received hematopoietic stem cell transplant (HSCT), but unfortunately died from relapsed disease. CONCLUSION: This case highlights the challenges faced in choosing treatment options in MPAL patients with complex genomics, with predominant myeloid features.

Leukemia With TCF3-ZNF384 Rearrangement as a Distinct Subtype of Disease With Distinct Treatments: Perspectives From A Case Report and Literature Review.

BACKGROUND: ZNF384 rearrangements are found in 5-10% of B-cell acute lymphoblastic leukemia (B-ALL) and 48% of B cell/myeloid mixed phenotype acute leukemia (B/M MPAL). ZNF384-rearranged B-ALL is prone to lineage conversion after chemotherapy. TCF3 is the second most common rearrangement partner of ZNF384 in B-ALL (27.5%) and the most common partner in B/M MPAL (53.3%). TCF3-ZNF384 fusion is related to a poor steroid response and a high frequency of relapse. It is mostly reported in children and adolescents but rarely seen in adults. PATIENTS AND METHODS: Here, we report a rare case of adult common B-ALL with TCF3-ZNF384 fusion in which the patient relapsed after one cycle of consolidation chemotherapy. Relapsed leukemia cells from the bone marrow were cultured for 72 hours ex vivo, and a panel of 156 kinds of cytotoxic drugs, targeted therapy drugs, combination chemotherapy drugs, etc., was used for sensitivity screening. The literature on TCF3-ZNF384 fusion was reviewed, and reported cases with TCF3-ZNF384 fusion were summarized. Clinical characteristics were compared between B-ALL and MPAL with TCF3-ZNF384 fusion. RESULTS: The relapsed lymphoblasts showed moderate sensitivity to both acute myelocytic leukemia (AML) - and acute lymphoblastic leukemia (ALL)-directed combination chemotherapy schemes, as well as to multiple targeted therapeutic drugs. The hyper-CVAD (B) scheme showed synergistic effects with multiple targeted compounds and had the highest sensitivity. The patient chose the hyper-CVAD (B) scheme combined with sorafenib and achieved complete remission (CR), then consolidated with myeloid-directed homoharringtonine+cytarabine+daunorubicin (HAD) scheme and gained molecular CR. By reviewing the literature, we found that both the genomic landscapes and gene expression profiles of ZNF384-rearranged B-ALL and MPAL are similar and that both diseases have lineage plasticity. The gene expression profile in TCF3-ZNF384-positive patients shows enrichment of hematopoietic stem cell features. No significant differences in clinical characteristics were found between TCF3-ZNF384-positive ALL and MPAL. CONCLUSION: TCF3-ZNF384-positive leukemia may be a distinct subtype of leukemia regardless of immunophenotype. Considering the frequent lineage switches and sensitivity to both ALL- and AML-directed schemes, a uniform strategy directed at both lymphoid and myeloid lineages or at hematopoietic stem cells may be better for TCF3-ZNF384-positive leukemia. Small molecule targeted therapies may be promising treatment options and deserve further investigation.

High-Risk Acute Promyelocytic Leukemia with Unusual T/Myeloid Immunophenotype Successfully Treated with ATRA and Arsenic Trioxide-Based Regimen.

We describe two patients with acute promyelocytic leukemia (APL) with an unusual immunophenotype with co-expression of myeloperoxidase (MPO) with cytoplasmic CD3 (cCD3) representing myeloid and T-lineage differentiation. Both harbored FLT3-ITD mutations. One additionally had a deletion in the PML gene affecting the primer binding site, thus limiting measurable residual disease (MRD) analysis during follow-up. Both patients achieved durable remission with all-trans retinoic acid (ATRA) and arsenic trioxide (ATO)-based therapy, thus mitigating the need for repetitive conventional chemotherapy cycles and allogeneic stem cell transplantation. Our report highlights the complexity and challenge of diagnosis and management of APL due to the variant immunophenotype and genetics, and underscores the importance of synthesizing information from all testing modalities. The association of the unusual immunophenotype and FLT3-ITD mutation illustrates the plasticity of the hematopoietic stem cell and the pathobiology of leukemia with mixed lineage or lineage infidelity.

Mixed phenotype acute leukemia, B/myeloid, NOS with near-tetraploidy: a case report.

Acute leukemia in adults is usually associated with a myeloid phenotype, and less commonly presents as an acute lymphocytic leukemia. Rarely, the leukemic blast cells express more than one lineage phenotype and satisfy the diagnostic criteria for an acute leukemia of ambiguous lineage (ALAL), further subclassified as mixed phenotype acute leukemia (MPAL). Near-tetraploidy is an unusual presentation of acute leukemia where the blasts contain 80-104 chromosomes. More commonly associated with acute lymphocytic leukemia, near-tetraploidy has been described in only a limited number of cases of acute myeloid leukemias, and near-tetraploid ALAL is rare. We describe the first report of near-tetraploid MPAL, B/myeloid, not otherwise specified.

Dual-targeting triplebody 33-3-19 mediates selective lysis of biphenotypic CD19+ CD33+ leukemia cells.

Simultaneous targeting of multiple tumor-associated antigens (TAAs) in cancer immunotherapy is presumed to enhance tumor cell selectivity and to reduce immune escape.The combination of B lymphoid marker CD19 and myeloid marker CD33 is exclusively present on biphenotypic B/myeloid leukemia cells. Triplebody 33-3-19 binds specifically to both of these TAAs and activates T cells as immune effectors. Thereby it induces specific lysis of established myeloid (MOLM13, THP-1) and B-lymphoid cell lines (BV173, SEM, Raji, ARH77) as well as of primary patient cells. EC50 values range from 3 pM to 2.4 nM. In accordance with our hypothesis, 33-3-19 is able to induce preferential lysis of double- rather than single-positive leukemia cells in a target cell mixture: CD19/CD33 double-positive BV173 cells were eliminated to a significantly greater extent than CD19 single-positive SEM cells (36.6% vs. 20.9% in 3 hours, p = 0.0048) in the presence of both cell lines. In contrast, equivalent elimination efficiencies were observed for both cell lines, when control triplebody 19-3-19 or a mixture of the bispecific single chain variable fragments 19-3 and 33-3 were used. This result highlights the potential of dual-targeting agents for efficient and selective immune-intervention in leukemia patients.

Children Diagnosed as Mixed-Phenotype Acute Leukemia Didn't Benefit from the CCLG-2008 Protocol, Retrospective Analysis from Single Center.

Mixed phenotype acute leukemia (MPAL) is a rare type of acute leukemia with a poor clinical outcome which lacks specific therapy. To evaluate the therapeutic efficiency of CCLG-2008 protocol used for acute lymphoblastic leukemia (ALL) in China on MPAL children who were initially diagnosed as ALL by morphology, we reviewed patients' database diagnosed as ALL and MPAL according to WHO classification and compared their outcomes from July 2008 to June 2012. Total newly enrolled ALL in this study were 309 cases by morphology, in which ten cases were identified as MPAL mainly by immunophenotyping: B+ myeloid (3/10), T+ myeloid (2/10), B + T (4/10), trilineage (1/10). Two cases were classified as intermediate risk (IR) and 8 cases were high risk (HR) according to the CCLG-2008 criteria. Only one case of IR survived and others died due to primary resistance of chemotherapy and relapse. Compared with MPAL, ALL children in IR and HR had a longer survival (28.1 vs 9.5 months, p < 0.0001) and lower relapse (16.3 vs 85.7 %, p = 0.0002). In a summary, our result indicated that MPAL in children is a poor-risk disease which needs personalized therapy to improve outcome.

A Newborn with Congenital Mixed Phenotype Acute Leukemia After In Vitro Fertilization.

Congenital leukemia is a rare disease. The majority of cases of this disease are acute myelogenous leukemia (AML). Congenital acute lymphoblastic leukemia (ALL) is rare and most often is of B cell lineage. Rarely, some cases have been designated biphenotypic or mixed phenotype acute leukemia (MPAL). Herein, we report a preterm newborn referred to us as a result of the appearance of blue-violaceous dermal nodules on her body at birth. She was a twin and the product of an in vitro fertilization (IVF) pregnancy. Physical examination showed jaundice, hepatosplenomegaly, and peripheral facial nerve palsy in addition to dermal nodules. Bone marrow aspiration showed 40% blasts of lymphoid lineage; skin biopsy and its immunohistochemistry revealed myeloblastic infiltration of the dermis. Cytogenetic analysis (46,XX), fluorescence in situ hybridization (FISH) analysis, and cranial magnetic resonance were normal. The patient was diagnosed with congenital MPAL, and an association between IVF and congenital leukemia was suggested.