Hepatoblastoma (HBL) is the most common pediatric liver cancer, and the prognosis of high-risk cases with clinical poor-prognostic factors remains poor. However, the molecular basis of high-risk HBL is not fully understood. To address this issue, we subjected 59 HBL samples to multiomics analyses, including DNA methylome analysis and RNA sequencing. On the basis of DNA methylation patterns, HBL was classified into three clusters (F, E1, and E2), which exhibited remarkable correlation with clinical, histological, and genetic features. Cluster F was largely composed of cases with fetal histology and good outcome, whereas clusters E1 and E2 largely correspond to cases with embryonal or embryonal/fetal combined histology and poor prognosis. Clusters E1 and E2 had similar genetic profiles and were characterized by the hypermethylation of HNF4A/CEBPA-binding regions followed by fetal liver-like expression patterns, frequent copy-number gains, upregulation of the cell-cycle pathway, and overexpression of NQO1 and ODC1. In particular, ODC1 is the gene encoding the rate-limiting enzyme of the polyamine biosynthesis pathway and associated with a high turnover of tumor cells. In fact, when we performed ODC1 inhibition experiments in vitro, we found that the growth of ODC1-expressing HBL cells was significantly suppressed. From these results, we concluded that ODC1 is a key gene of the aggressive phenotype and a potential therapeutic target of high-risk HBL. The DNA-methylation-based classification of HBL disclosed the molecular basis of HBL, suggesting rational therapeutic strategies for high-risk HBL.

The current results of treatment strategies for high-risk neuroblastoma have been far from satisfactory. ALK inhibitors were greatly anticipated to cure this disease, but practically, a large proportion of the patients did not benefit from them. A new approach is required to make advances. Reprogramming of metabolism in cancer cells, also called cancer metabolism, has been recognized as an important hallmark of malignancy, as it is deeply related to tumor progression and treatment resistance. We analyzed several datasets of neuroblastoma including our institutional cohort and extracted PHGDH, which is the gene encoding phosphoglycerate dehydrogenase (PHGDH), as a candidate target gene, a high expression level of which correlates with poor prognosis in these multiple cohorts. PHGDH is the enzyme essential in serine metabolism, and the enhancement of its expression has been observed in several other malignancies. We further conducted functional analyses in vitro and confirmed that the inhibition of PHGDH suppressed cell growth in neuroblastoma cells with a high PHGDH expression level. Also, by conducting metabolome and transcriptome analyses, we found that arginine depletion by the prior administration of arginine deiminase enhanced the cytotoxic effect of the PHGDH inhibitor in a subset of neuroblastoma cells by altering cellular metabolism. In summary, our results suggest that manipulating cancer metabolism is a powerful approach to developing novel therapeutic strategies against aggressive neuroblastoma.

Cytopenic children during or after cancer chemotherapy or hematopoietic cell transplantation (HCT) are at a high risk of infections. Mycobacterial infections are quite rare compared with bacterial, viral or fungal infections in pediatric patients on cancer chemotherapy or HCT. However, their early diagnosis and appropriate management are required because of their severity and mortality. More than 30 species of nontuberculous mycobacteria have been reported in Japan, including slowly growing mycobacteria (SGM) and rapidly growing mycobacteria (RGM). SGM such as Mycobacterium avium, Mycobacterium kansasii, and Mycobacterium marinum often cause disseminated infection. RGM including Mycobacterium chelonae, Mycobacterium abscessus, and Mycobacterium fortuitum cause catheter-related infection. The number of pediatric patients infected with Mycobacterium tuberculosis is decreasing yearly to less than 100 of the annual incidences of newly diagnosed pediatric cases in Japan. Because of the low morbidity but high mortality of mycobacterial infections in immunocompromised children, accurate diagnosis and treatment are indispensable for their management in pediatric hematology and oncology.

Diamond–Blackfan anemia (DBA) is a congenital bone marrow failure syndrome characterized by diminished numbers of erythroid progenitors. Although it is known that the ribosome is involved in the DBA onset, the molecular pathogenesis of this disease remains unknown and there are no clinically effective treatments available. We developed a zebrafish model of DBA and analyzed the pathogenic mechanism of this disease using this model. Zebrafish has many advantages in studying disease mechanisms, including the fast development and transparency of its embryos and its features conserved in humans. In addition, in vivo chemical screenings enable us to efficiently identify drug candidates. In this review, we introduce our approach to understand the pathogenic mechanism of DBA and to discover drug candidates using zebrafish as an animal model.

Compared with adult cancers, pediatric tumors are rare, and limited access to tumor cells and tissues is a barrier to developing translational research. To overcome these limitations, there are international efforts to develop patient-derived xenograft (PDX) banks for pediatric leukemias and solid tumors. A PDX model can be developed by implanting tumor cells or tissues from a patient’s tumor into an immune-deficient mouse via the tail vein, subcutaneously or orthotopically, thereby preserving both cell–cell interactions and the tumor microenvironment within the limitation of cross talk between mouse and human cells. PDXs not only expand the tumor cells but also recapitulate the pathology of the human disease in vivo. In addition, the PDX model has shown advantages as a preclinical model in drug screening and preclinical trials. In Japan, Fukushima Medical University and Kyoto University established the first nationwide publicly available repository of PDXs transplanted with pediatric leukemias in 2013. This repository will enable investigators from both academic and industrial laboratories to conduct therapeutic tests using patient-derived samples. In this review, we will summarize the developmental history of immune-deficient mice, efforts of overcoming the limitations of PDXs, and current applications of this model in preclinical research.

Mouse bone marrow transplantation (BMT) models are powerful tools for investigating the mechanisms of development and malignant progression of acute myeloid leukemia (AML). AML induction is achieved by the purification of hematopoietic stem/progenitor cells (HSPCs) from the bone marrow of wild-type or genetically engineered mice, transduction of leukemia disease genes into HSPCs using retrovirus-mediated gene transfer, and transplantation of transduced cells into lethally irradiated recipients. The models well recapitulate the phenotypes of human AML, and they have been utilized for tracing the developmental of AML and as platforms of novel therapeutics. By generating the Hoxa9- and Meis1-expressing BMT model, we have identified Sytl1, which promotes engraftment to bone marrow and in vivo expansion of leukemic cells, and Trib1, which encodes pseudokinase functioning in C/EBPα degradation and enhancement of ERK phosphorylation. There are some biological analogies between AML and bone and soft tissue sarcoma (BSTS), for example, they are of mesenchymal origin, they show low mutational burdens, and oncogenic transcription factors play an important role in enhancer-reprograming causally associated tumorigenesis. To overcome technical difficulties in modeling BSTS, we purified embryonic mesenchymal cells, introduced sarcoma-specific fusion genes into the cells, and transplanted them into allogenic hosts. We have succeeded in generating six model lines and are investigating the molecular mechanisms of sarcomagenesis and functions of fusion gene products. In this review, we describe the principle of model generation and novel insights into the molecular mechanisms of leukemia and sarcoma development, which were clarified by analyzing the models.

How to manage clinical trials for rare cancer including pediatric cancer is a burning issue globally involving Japanese regulatory authorities. The conditions that can loosen limitations in study designs are as follows: (1) allowance for a one-arm trial design, (2) setting a surrogate endpoint (e.g., response rate), and (3) increasing type-I or type-II error probabilities. Also, several efficient study designs are suggested, such as study designs based on genomic information (e.g., umbrella design and basket design), N-of-1 design, adaptive designs, and Bayesian designs. The advantages of the Bayesian approach are as follows: (1) the interpretation for the probability is intuitive, (2) the flexibility that enables the probability update during the study is suitable for adaptive design, and (3) the variety of prior beliefs, which sometimes have clinically important meanings, can be explicitly integrated as a prior distribution. A trade-off exists between scientific validity and efficiency in trial designs. Therefore, the pros and cons of each design should be thoroughly discussed at the planning stage. Effective collaborations between clinicians and statisticians are necessary to improve the quality of trial design.

Allogeneic blood transfusion is technically less challenging than solid organ transplantation, but potential adverse events are of similar magnitude. Thus, inappropriate transfusion could be construed as medical malpractice. The Japan Society of Transfusion Medicine and Cell Therapy (JSTMCT) promulgates evidence-based guidelines for each blood product. Guidelines from Japan’s Ministry of Health, Labour and Welfare also exist, and have recently been updated. Papers pertaining to patients up to four months old and reported from 1994 to 2014 were collected and analyzed. Recommendations were weighted according to the strength of each paper’s evidence, with the goal of establishing consensus on three clinical questions: a trigger for red blood cell (RBC) transfusion, a trigger for platelet concentrate (PC) transfusion, and circumstances in which cytomegalovirus-safe (CMV-safe) blood products should be selected. Consensus statements are as follows. A hemoglobin (Hb) trigger for RBC transfusion is Hb 7 g/dL. A platelet count (PLT) trigger for PC transfusion is PLT 20,000–30,000/μL. Circumstances in which CMV-safe blood products should be selected include transfusion in utero until 28 days postpartum when the mother’s CMV titer is negative or unknown. For transfusion after 4 months of age, the standard JSTMCT guidelines for adults should be consulted. Moreover, note that the previous recommendation of a fibrinogen level≤150 mg/dL for fresh frozen plasma transfusion has been revised, and albumin infusion is no longer indicated for a number of conditions previously approved. Technical challenges in solid organ transplantation require teamwork. Although technical challenges may be less in allogeneic blood transfusion, teamwork is just as important, and team members, including physicians, should be well versed in the latest evidence-based transfusion guidelines.

Nonacog beta pegol (N9-GP, Refixia^®) is an extended half-life recombinant factor IX (FIX) product. Results of a global phase III clinical trial, paradigm 5, revealed the efficacy and safety of weekly prophylaxis with N9-GP in pediatric hemophilia B patients (FIX activity </=0.02 IU/mL), achieving a mean FIX trough level higher than 0.15 IU/mL. This study is a detailed analysis of three Japanese pediatric patients with severe hemophilia B who enrolled in the paradigm 5 study. The mean treatment duration was 3.29 years, during which seven bleeding events requiring treatment occurred in the three patients. All bleeding events were mild/moderate and responded well to a single administration of N9-GP. None of the patients developed target joints during the study period. The overall annualized bleeding rates and the annualized spontaneous bleeding rates were similar to the paradigm 5 results. There was no severe or serious adverse event, adverse event suspected to be related to the study treatment, or development of FIX inhibitors. The mean FIX trough level of the prophylactic treatment was 0.172 IU/mL, which was similar to that found in the paradigm 5 study. Only three patients were analyzed in this study; however, the results were not markedly different from those of the paradigm 5 study.

[Background] The number of adolescents and young adults with cancer treated by pediatricians is increasing because of the priority of the pediatric regimen in some diseases and many aspects that we can support, such as physical and mental immaturity, needs for studying, and relationship with their parents. Medical staff members might encounter various problems, but there are few studies and reports about their problems. [Purpose] The aims of this study are to comprehend the actual situation of pediatric staff members who treat teenagers or older patients with cancer and to address their problems. [Method] We carried out a questionnaire survey targeting medical staff members (n=93 at six institutions) who attend to teenagers or older patients with cancer, such as doctors, nurses, school teachers, psychologists, and other medical staff members. [Results] Medical staff members encountered much difficulty and various problems in attending to teenagers and older patients. Nurses and other staff members felt more difficulty than doctors. They strongly felt the need for more support for them. We also found insufficient support for the patients regarding psychological problems and worries about future life events and inconsistent opinions about the preservation of fertility before aggressive therapy. [Conclusion] Pediatric staff members have many difficulties when treating teenagers and older patients. Sharing these problems with various staff members in various institutions will achieve better treatment and care for them.

Here, we describe the case of a 4-year-old boy with cerebellar vermis tumor, which was diagnosed as medulloblastoma (classic medulloblastoma with desmoplasia, WHO grade IV, Chang stage classification M1). Following one course of chemotherapy, he developed cancerous meningitis. Therefore, we performed intrathecal injection (IT) of methotrexate (MTX)+dexamethasone (DEX) once/week for 3 weeks until the cerebrospinal fluid cytology results became negative. The patient underwent (1) chemotherapy (four courses), (2) radiotherapy (craniospinal irradiation, 24 Gy; focal irradiation, 51.2 Gy), and (3) high-dose chemotherapy with thiotepa (TEPA)+melphalan (MEL) combined with autologous stem cell transplantation. Maintenance therapy with oral etoposide was also administered. The patient was found to be surviving without relapse at 49 months after diagnosis. It is suggested that treatment by IT of MTX+DEX and high-dose chemotherapy with TEPA+MEL combined with autologous stem cell transplantation can be expected to have significant therapeutic effects on high-risk medulloblastomas with cancerous meningitis.

Introduction: Although the prognosis of pelvic peripheral neuroblastic tumors (PNTs) is good, chemotherapies are frequently chosen over a surgical operation as the initial treatment strategy because such tumors surround neurons and vessels with an anatomical regional problem.

Case: A 1.5-year-old girl had a pelvic solid tumor and the diagnosis based on the histopathological analysis of biopsy specimens was differentiating-subtype, low-mitosis-karyorrhexis-index (MKI) neuroblastoma of favorable histology (FH) type based on the International Neuroblastoma Pathology Classification (INPC). A mild chemotherapy was conducted because the tumor might arise from the sacral plexus and complete total resection was impossible. However, because there was no response to the first chemotherapy in terms of tumor size and tumor marker levels, we chose to perform surgery instead of several courses of chemotherapies.

Conclusion: The initial chemotherapy did not cause apoptosis of the PNTs, which means that the tumor cells had already started to differentiate, and there was a low probability of a decrease in tumor size. FH-type neuroblastoma is not essentially different from ganglioneuroblastoma, intermixed and ganglioneuroma, and surgical therapy should be a priority.

Reduced-intensity chemotherapy is often considered for Down syndrome (DS) patients with malignancies. Tolerance to conventional chemotherapy in DS patients with intracranial germ cell tumors (GCTs) is unclear. A 13-year-old boy with DS presented with headache and disturbed eye movement. He underwent cranial magnetic resonance imaging, which revealed a pineal tumor. The tumor was resected completely. Histopathological examination of the tumor led to the diagnosis of mixed GCT composed of immature teratoma with pineal choriocarcinoma. The patient received six courses of ifosfamide, carboplatin, and etoposide (ICE) regimen in combination with proton therapy. Considering toxicities, the first ICE course was decreased to 60% of the predetermined doses, and there were no severe adverse events. Therefore, the five remaining ICE courses were administered at full doses, without severe adverse events. This case indicated that conventional doses of the ICE regimen might be feasible and effective for intracranial GCTs in children with DS.

Children with Down syndrome (DS) are at a significantly increased risk of acute leukemia. We present a rare case of de novo acute lymphoblastic leukemia associated with DS (DS-ALL) after remission of myeloid leukemia associated with Down syndrome (ML-DS). At the age of 18 months, a girl with DS had anemia and thrombocytopenia. Her bone marrow aspirate showed 17% blasts expressing CD41, CD7, CD13, CD33, and GP-A, and having the GATA1 mutation. She was diagnosed as having ML-DS and was treated for AML, and she then showed long-term remission. At the age of 7 years, she had petechiae and thrombocytopenia again. Her bone marrow aspirate showed 96% blasts expressing CD10, CD19, CD20, and HLA-DR. However, these leukemic cells did not have the GATA1 mutation. She was diagnosed as having de novo DS-ALL and received treatment for ALL. Since the age of 14 years, she has been in complete remission of both ML-DS and DS-ALL.

The number of cases in which haploidentical hematopoietic stem cell transplantation (Haplo-HSCT) is performed in anticipation of a very strong graft versus leukemia (GVL) response for high-risk pediatric hematologic malignancies is increasing. However, it is known that extramedullary relapse (EMR) occurs after Haplo-HSCT, because the effectiveness of GVL is reduced. We encountered an acute myelogenous leukemia (AML) patient with multiple EMRs after related Haplo-HSCT. There are Haplo-HSCT cases in which leukemic cells escaped from graft surveillance recur from EMR, and it is known that the long-term prognosis of patients with EMR after Haplo-HSCT is poor. After Haplo-HSCT, careful follow up for not only bone marrow relapse but also EMR with imaging studies should be conducted.