Neuroblastoma is one of the most common solid tumors in children and has a diverse clinical behavior that largely depends on the tumor biology. Neuroblastoma exhibits unique features, such as early age of onset, high frequency of metastatic disease at diagnosis in patients over 1 year of age and the tendency for spontaneous regression of tumors in infants. The high-risk tumors frequently have amplification of the MYCN oncogene as well as segmental chromosome alterations with poor survival. Recent advanced genomic sequencing technology has revealed that mutation of ALK, which is present in ~10% of primary tumors, often causes familial neuroblastoma with germline mutation. However, the frequency of gene mutations is relatively small and other aberrations, such as epigenetic abnormalities, have also been proposed. The risk-stratified therapy was introduced by the Japan Neuroblastoma Study Group (JNBSG), which is now moving to the Neuroblastoma Committee of Japan Children's Cancer Group (JCCG). Several clinical studies have facilitated the reduction of therapy for children with low-risk neuroblastoma disease and the significant improvement of cure rates for patients with intermediate-risk as well as high-risk disease. Therapy for patients with high-risk disease includes intensive induction chemotherapy and myeloablative chemotherapy, followed by the treatment of minimal residual disease using differentiation therapy and immunotherapy. The JCCG aims for better cures and long-term quality of life for children with cancer by facilitating new approaches targeting novel driver proteins, genetic pathways and the tumor microenvironment.

Congenital amegakaryocytic thrombocytopenia (CAMT) is caused by the loss of thrombopoietin receptormediated (MPL-mediated) signaling, which causes severe pancytopenia leading to bone marrow failure with onset of thrombocytopenia and anemia prior to leukopenia. Because Mpl -/-mice do not exhibit the human disease phenotype, we used an in vitro disease tracing system with induced pluripotent stem cells (iPSCs) derived from a CAMT patient (CAMT iPSCs) and normal iPSCs to investigate the role of MPL signaling in hematopoiesis. We found that MPL signaling is essential for maintenance of the CD34 + multipotent hematopoietic progenitor (MPP) population and development of the CD41 + GPA + megakaryocyte-erythrocyte progenitor (MEP) population, and its role in the fate decision leading differentiation toward megakaryopoiesis or erythropoiesis differs considerably between normal and CAMT cells. Surprisingly, complimentary transduction of MPL into normal or CAMT iPSCs using a retroviral vector showed that MPL overexpression promoted erythropoiesis in normal CD34 + hematopoietic progenitor cells (HPCs), but impaired erythropoiesis and increased aberrant megakaryocyte production in CAMT iPSC-derived CD34 + HPCs, reflecting a difference in the expression of the transcription factor FLI1. These results demonstrate that impaired transcriptional regulation of the MPL signaling that normally governs megakaryopoiesis and erythropoiesis underlies CAMT.

The development of large-scale suspension cell cultures using microcarriers has long been a focus of attention in the fields of pharmacy and biotechnology. Previously, we developed cell-detachable microcarriers based on temperature-responsive poly(N-isopropylacrylamide) (PIPAAm)-grafted beads, on which adhering cells can be noninvasively harvested by only reducing the temperature without the need for proteolytic enzyme treatment. In this study, to improve the cell harvest efficiency from bead surfaces while maintaining cell adhesion and proliferation properties, we prepared temperature-responsive cationic copolymer-grafted beads bearing a copolymer brush consisting of IPAAm, positively charged quaternary amine monomer (3-acrylamidopropyl trimethylammonium chloride; APTAC), and hydrophobic monomer (N-tert-butylacrylamide; tBAAm). The incorporation of positively charged APTAC into the grafted copolymer brush facilitated bead dispersibility in a cell culture system containing Chinese hamster ovary (CHO-K1) cells and consequently allowed for enhanced cell proliferation in the system compared to that of unmodified CMPS and conventional PIPAAm homopolymer-grafted beads. Additionally, P(IPAAm-co-APTAC-co-tBAAm) terpolymer-grafted beads exhibited the most rapid and efficient cell detachment behavior after the temperature was reduced to 20 °C, presumably because the highly hydrated APTAC promoted the overall hydration of the P(IPAAm-co-APTAC-co-tBAAm) chains. Therefore, P(IPAAm-co-APTAC-co-tBAAm) terpolymer-grafted microcarriers are effective in facilitating both cell proliferation and thermally induced cell detachment in a suspension culture system.

Hemophagocytic lymphohistiocytosis (HLH) is characterized by uncontrolled activation of T cells and macrophages with overproduction of cytokines. Familial HLH type2 (FHL2) is the most common form of primary HLH and is caused by mutations in PRF1. We have recently described a significant increase in the subpopulation of CD8 + T cells with clonal expansion and CD5 down-regulation in Epstein-Barr virus associated-HLH, which represented a valuable tool for its diagnosis. However, this unusual phenotype of CD8 + T cells has not been investigated fully in patients with FHL2. We performed immunophenotypic analysis of peripheral blood and measured serum proinflammatory cytokines in 5 patients with FHL2. All patients showed significantly increased subpopulations of activated CD8 + T cells with down-regulation of CD5, which were negligible among normal controls. Analysis of T-cell receptor Vβ repertoire suggested the reactive and oligoclonal expansion of these cells. The proportion of the subset declined after successful treatment concomitant with reduction in the serum levels of cytokines in all patients except one who continued to have a high proportion of the subset and died. These findings suggest that down-regulation of CD5 on activated CD8 +

Familial hemophagocytic lymphohistiocytosis (FHL) is a disorder of immune homeostasis characterized by fever, cytopenias, hepatosplenomegaly, and coagulopathy. We studied the outcomes of 13 FHL patients who underwent the first unrelated cord blood transplantation (UCBT) after non-myeloablative conditionings. The major regimen consisted of fludarabine (FLU; n 5 12) 1 melphalan (MEL; n 5 11) ± low-dose total body irradiation (TBI 2-4 Gy; n 5 6). The median age at presentation and period to UCBT were 6 and 5 months, respectively. Central nervous system (CNS) disease developed in one infant at diagnosis, and in two others until UCBT. HLH activity was controlled in all but one at the time of UCBT. Ten patients had early engraftment on median day 21 with no grade >2 treatment-related toxicity and two controllable grade >2 acute GVHD. Two patients with early rejection successfully underwent subsequent UCBT after myeloablative conditioning. Two others had late graft failure following mixed donor chimerism. Two deaths occurred from HLH; early liver failure and late CNS disease. Of 11 FLU1MEL-conditioned patients, the frequency of disease-free complete engraftment was higher for MEL ( 120 mg/m 2 )1TBI, or high-dose MEL (180 mg/m 2 ) than for others (83% vs. 25%, p 5 0.036). The FLU1MEL-based non-myeloablative regimen was acceptable for FHL infants undergoing UCBT, although further studies will be needed for confirmation.Hemophagocytic lymphohistiocytosis (HLH) is a disorder of immune homeostasis characterized by fever, cytopenias, hepatosplenomegaly, hyperferritinemia, and disseminated intravascular coagulopathy [1]. The lifethreatening condition arises from uncontrolled activation of proliferating lymphocytes, hemophagocytosing macrophages, and hypercytokinemia. The genetic basis of primary HLH resides in the defective cytotoxicity of Tcells and natural killer cells, although secondary HLH can occur in patients with infection, malignancy, or autoimmune disease. Familial HLH (FHL) is an autosomal recessive disease. Affected patients develop HLH mostly in childhood as the sole phenotype of the disease and require allogeneic hematopoietic stem cell transplantation (SCT) for a complete cure. The causal genes of FHL account for the structure, function, and metabolism of cytotoxic granules, such as PRF1 (FHL2), UNC13D (FHL3), STX11 (FHL4), and STXBP2 (FHL5) [2]. A potential risk of developing HLH is also a part of the clinical expressions of X-linked lymphoproliferative disease (XLP1 and XLP2), Chediak-Higashi syndrome, and Griscelli syndrome [3].Recent advances in SCT procedures have improved the survival rate of patients with FHL who undergo SCT after myeloablative conditioning, which now range from 45 to 65% [4][5][6][7][8][9][10][11]. However, there remain critical problems with SCT for FHL; early death from treatment-related events often associated with venoocclusive disease, and neurological sequelae in survivors. The early age at diagnosis also raises a clinical dilemma concerning the timing, preparative regimen, and al...

Tissue-engineered bone has attracted much attention as an alternative material for bone grafting; however, implantable bone tissue of an appropriate size and shape for clinical use has not yet been developed due to a lack of vascularization, which results in necrosis of the seeded cells in vivo. This is the first report of bone tissue engineering associated with vascularization by co-culturing bone marrow mesenchymal stem cells (MSCs) with MSC-derived endothelial cells (ECs) within a porous scaffold using a rotating wall vessel (RWV) bioreactor. MSC-derived ECs were identified by immunofluorescence staining for von Willebrand factor (vWF) and by flow cytometry for CD31 expression. The tissue obtained was histochemically analyzed using toluidin blue, hematoxylin and eosin, anti-osteopontin antibody, anti-osteocalcin antibody, and tomato-lectin stain. Results showed that bone tissue containing vascular-like structures was generated. Three-dimensional culture condition created by medium flow in the RWV vessel and the interaction of MSCs with MSC-derived ECs might provide the cells an advantage in the construction of three-dimensional bone tissue with blood vessels.

MicroRNAs (miRNAs) regulate cell proliferation and differentiation by controlling the expression of proteins involved in many signaling pathways. Recent studies have shown that dysregulation of miRNA expression is associated with increased tumorigenicity and a poor prognosis in several types of cancers. The miRNA let-7b is one of the severely downregulated miRNAs in mixed-lineage leukemia (MLL)-rearranged acute lymphoblastic leukemia (ALL) patients. In vitro transfection of leukemogenic MLL fusion genes into human embryonic kidney-293 cells suppressed let-7b expression. In leukemic cells with an MLL fusion gene, the regulatory region for let-7b expression was hypermethylated, and its expression was partially recovered after culturing the cells with the demethylating agent 5-azacitidine. These results suggest that loss of let-7b expression may be one of the consequences of oncogenic MLL fusion proteins, and contributes to leukemogenesis possibly through the upregulation of let-7b-regulated target genes with leukemogenic potential in hematopoietic cells. The enforced expression of let-7b in ALL cell lines with an MLL fusion gene inhibited their growth, indicating the possible use of let-7b as a new therapeutic tool for refractory infant ALL with an MLL fusion gene.

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