S. Wehner

Smac mimetic and glucocorticoids synergize to induce apoptosis in childhood ALL by promoting ripoptosome assembly

Apoptosis resistance contributes to poor outcome in pediatric acute lymphoblastic leukemia (ALL). Here, we identify a novel synergistic combination of Smac mimetic BV6 and glucocorticoids (GCs) (ie, dexamethasone, prednisolone) to trigger apoptosis in ALL cells. BV6 and GCs similarly cooperate to induce apoptosis in patient-derived leukemia samples, underlining the clinical relevance. Importantly, BV6/dexamethasone cotreatment is significantly more effective than monotherapy to delay leukemia growth in a patient-derived xenograft model of pediatric ALL without causing additional side effects. In contrast, BV6 does not increase cytotoxicity of dexamethasone against nonmalignant peripheral blood lymphocytes, mesenchymal stromal cells, and CD34-positive hematopoietic cells. We identify a novel mechanism by showing that BV6 and dexamethasone cooperate to deplete cIAP1, cIAP2, and XIAP, thereby promoting assembly of the ripoptosome, a RIP1/FADD/caspase-8-containing complex. This complex is critical and is required for BV6/dexamethasone-induced cell death, because RIP1 knockdown reduces caspase activation, reactive oxygen species production, and cell death. Ripoptosome formation occurs independently of autocrine/paracrine loops of death receptor ligands, because blocking antibodies for TNFα, tumor necrosis factor-related apoptosis-inducing ligand, or CD95 ligand or knockdown of death receptors fail to rescue BV6/dexamethasone-induced cell death. This is the first report showing that BV6 sensitizes for GC-triggered cell death by promoting ripoptosome formation with important implications for apoptosis-targeted therapies of ALL.

Cytotoxic effects of treosulfan and busulfan against leukemic cells of pediatric patients

PurposeThe alkylating agent treosulfan exerts a high cytotoxic activity against various malignant cells. Due to limited non-hematological toxicity, treosulfan might be a promising compound in myeloablative therapy for hematopoietic transplantation in children. Since in vitro data regarding the activity of treosulfan against childhood leukemic cells are limited, we compared the effect of treosulfan and busulfan against pediatric leukemic and non-malignant cells.Experimental designBoth agents were tested alone and in combination with fludarabine by means of the MTT and/or a five color-flow cytometric assay. Moreover, the induction of apoptosis by treosulfan was investigated via regulation of the proteinase caspase 3.ResultsTreosulfan was more active against leukemic cells of 20 children as well as against 3 leukemia-derived cell lines than busulfan, with increasing IC50 values from initial diagnosis to relapse. Overall purified stem cells were most sensitive, followed by CD56+CD3− NK and CD3+ T cells. The combination of treosulfan with fludarabine resulted in a synergistic effect against leukemic cells. In malignant cells, treosulfan induced rapid cell apoptosis measured by the activation of the centrally proteinase caspase 3.ConclusionOur results indicate that treosulfan has activity against pediatric leukemic cells, myeloablative potential and immunosuppressive properties suitable for conditioning regimen in childhood malignancies.

wt1 Gene Expression in Childhood Leukemias

The expression of the Wilms’ tumor gene (wt1) was detected in various tissues during embryonic development. Mutations in the wt1 gene probably play an important role in certain tumors, e.g. the Wilms’ tumor. Furthermore the expression of wt1 gene was found in some human leukemias. In the present study we investigated the expression of wt1 gene in several types of childhood leukemia by reverse transcriptase-polymerase chain reaction. Bone marrow or peripheral blood of 61 pediatric patients (48 at initial diagnosis, 13 at first or second relapse) were analyzed. wt1 gene expression was detected in 35/48 patients (73%) with newly diagnosed leukemias and in 12/13 cases (92%) who had suffered from relapse. The expression levels were higher for AML than for ALL. The frequency of wt1 expression in different subtypes of acute leukemia was compared with results found in adult patients. Our results show that the frequency of wt1 gene expression in acute childhood leukemias is similar to previous data reported for adults.

Altered mucosal immune response after acute lung injury in a murine model of Ataxia Telangiectasia

BackgroundAtaxia telangiectasia (A-T) is a rare but devastating and progressive disorder characterized by cerebellar dysfunction, lymphoreticular malignancies and recurrent sinopulmonary infections. In A-T, disease of the respiratory system causes significant morbidity and is a frequent cause of death.MethodsWe used a self-limited murine model of hydrochloric acid-induced acute lung injury (ALI) to determine the inflammatory answer due to mucosal injury in Atm (A-T mutated)- deficient mice (Atm-/-).ResultsATM deficiency increased peak lung inflammation as demonstrated by bronchoalveolar lavage fluid (BALF) neutrophils and lymphocytes and increased levels of BALF pro-inflammatory cytokines (e.g. IL-6, TNF). Furthermore, bronchial epithelial damage after ALI was increased in Atm-/- mice. ATM deficiency increased airway resistance and tissue compliance before ALI was performed.ConclusionsTogether, these findings indicate that ATM plays a key role in inflammatory response after airway mucosal injury.

Immunological detection and definition of minimal residual neuroblastoma disease in bone marrow samples obtained during or after therapy

Immunological staining by the alkaline phosphatase/anti-alkaline phosphatase (APAAP) technique has been used to recognize low levels of neuroblastoma cells in bone marrow mononuclear cells. Immunological phenotyping with 11 well characterized monoclonal antibodies was performed on 16 children with neuroblastoma and BM involvement during or after therapy. Neuroblasts were detected in 11 of 16 patients (0.1-5%), whereas BM biopsies on six of these patients were classified as normal. Aspirates, stained conventionally, were positive for pathological cells in three patients only. The comparison of the phenotype of the neuroblastoma cells at the time of diagnosis to the phenotype of the residual cells within one patient revealed differences. The phenotype of residual disease in different patients on the other hand showed a unique pattern. The above mentioned results lead to the conclusion that the immunological procedure is particularly suitable for the analysis of minimal residual neuroblastoma since the technique allows very minor cell populations to be identified in BM samples.

Minimal residual disease in leukemia in children.

Many chromosomal translocations involved in leukemia have been defined at the molecular level in recent years. In addition to advancing the understanding of pathological mechanisms underlying the transformation process, the cloning and sequencing of the genes altered by the translocations have provided new tools for diagnosis and monitoring of patients. In particular, the polymerase chain reaction (PCR) method yields sensitive and accurate diagnostic and prognostic information. Minimal residual disease (MRD) is not clearly defined. In ALL we define MRD as fewer than 5% blast cells in the bone marrow by conventional cytology and proof of leukemic cells with more sensitive methods. The techniques for detecting MRD are imaging for detection of single leukemic cells in the blood, bone marrow, or other tissues by means of immunocytology or PCR/RT-PCR. Highly sensitive PCR, immunocytology, FACS analysis, or conventional cytology are important tools to use in the process of deciding on appropriate therapy. Detection limits at present are 10(-2) for cytology and FISH, up to 10(-4) for immunological procedures, and 10(-5) to 10(-6) for PCR. But multiple methods also imply the possibility of mistakes (e.g., PCR). The question must be raised what method should be decisive in assessing MRD for evaluating autologous peripheral blood stem cells (PBSC) or autologous bone marrow transplants? Prospective studies will have to answer the question whether MRD should be treated or not and whether purging of bone marrow or PBSC is useful or damaging. When applied, should a positive or a negative immunopurging or a chemotherapeutic purging be used? MRD refers to the organism of the patient as well as to the peripheral blood stem cells and autologous bone marrow that had been taken before myeloablative therapy and kept for retransfusion.

Tumorigenic and anti-proliferative properties of the TALE-transcription factors MEIS2D and MEIS2A in neuroblastoma

Neuroblastoma is one of only a few human cancers that can spontaneously regress even after extensive dissemination, a poorly understood phenomenon that occurs in as many as 10% of patients. In this study, we identify the TALE-homeodomain transcription factor MEIS2 as a key contributor to this phenomenon. We identified MEIS2 as a MYCN-independent factor in neuroblastoma and showed that in this setting the alternatively spliced isoforms MEIS2A and MEIS2D exert antagonistic functions. Specifically, expression of MEIS2A was low in aggressive stage 4 neuroblastoma but high in spontaneously regressing stage 4S neuroblastoma. Moderate elevation of MEIS2A expression reduced proliferation of MYCN-amplified human neuroblastoma cells, induced neuronal differentiation and impaired the ability of these cells to form tumors in mice. In contrast, MEIS2A silencing or MEIS2D upregulation enhanced the aggressiveness of the tumor phenotype. Mechanistically, MEIS2A uncoupled a negative feedback loop that restricts accumulation of cellular retinoic acid, an effective agent in neuroblastoma treatment. Overall, our results illuminate the basis for spontaneous regression in neuroblastoma and identify an MEIS2A-specific signaling network as a potential therapeutic target in this common pediatric malignancy.Significance: This study illuminates the basis for spontaneous regressions that can occur in a common pediatric tumor, with implications for the development of new treatment strategies. Cancer Res; 78(8); 1935-47. ©2018 AACR.

Identification of Minimal Residual Leukemia Applying Continuous Gating

Clonal expansion of hematopoietic progenitor cells arrested at various differentiation steps demonstrating defined antigen expressions are characteristic for acute leukemias. The detection of hyperdiploid leukemic blast cells are an independent prognostic factor strongly associated with favorable clinical outcome. Therefore a combination of immunophenotype and aneuploid DNA-index may be of great benefit for the detection of minimal residual disease in acute leukemias.

CD133/CD34 Expression on Hematopoietic Stem-/Progenitor Cells and Acute Leukemic Blasts

CD133, a recently discovered antigen on human progenitor cells, demonstrating 5-transmembra-neous domains is expressed by 30-60% out of all CD34+ cells. Our aim therefore was to investigate the extent of human stem-/progenitor cells expressing CD133 antigen in umbilical cord blood, peripheral blood without or following an application of granulocyte-colony stimulating factor (rhG-CSF). The main task was the investigation of bone marrow aspirates derived from children suffering from newly diagnosed acute leukemias, as well as from patients with a relapse or during a complete remission. The determination of antigen expression was done by application of flow cytometry (FACScan analyses) and the usage of newly developed monoclonal antibodies (CD133/1 and CD133/2; Miltenyi Biotec GmbH) in combination with monoclonal antibody directed against CD34-antigens (HPCA-2; BD).

Acute Lymphoblastic Leukemia in Childhood with an Unusual Immunophenotype (CD7 +/CD56 +/CD33 +)

We have identified and characterized an unusual and unrecognized type of acute leukemia with features of T-lymphoid, myeloid and natural killer cell (NK) associated markers in a five year old girl with morphologically and cytochemically undifferentiated acute leukemic blast cells. The bone marrow and peripheral blood smears showed ALL FAB-L1/2 morphology with immunological features of CD7 +, CD33 +, CD56 + myeloid/natural killer cell precursor type. The marker analysis exhibited the coexpression pattern of cyCD3, CD34, CD38, CD45, CD54, CD71 and HLA-DR antigens just as the neutrophil marker CD11b. In 50% of the blast cells cytoplasmic CD3 was detectable but on the other hand this leukemic entity failed to express other NK associated antigens (e.g. CD16/CD57) additionally no other expressions of T- and B-cell lineage associated markers could be observed. The blasts expressing the stem cell marker CD34 failed to express AC 133 and CD 117. This unusual phenotype seems to be very similar to the recently by Scott et al. [24] and by Suzuki et al. [20] proposed »myeloid/NK cell precursor acute leukemia« entity in adults. In comparison to our case the Scott’s type was characterized by mature myeloid morphology with MPO reactivity but without information about the expression of CD7. Their cases were described to be exclusively negative for HLA-DR. The phenotype of our case seems to be more identical to the recently reported entity by Suzuki et al. (1997), with exception of MPO expression and missing cyCD3 positivity in their cases of adults. CD7 is a T-cell marker which is expressed in immature NK cell progenitors and was a feature of the myeloid/NK cell precursor acute leukemia in our and Suzukius’ cases.