Published papers

Background: CD19-targeted chimeric antigen receptor (CAR)-T cell therapy involves administration of patient-derived T cells that target B cells, resulting in B-cell depletion and aplasia. In immunity against Pneumocystis jirovecii (Pj), CD4+ T cells and, more recently, B cells, are generally considered important. Antigen presentation by B cells to CD4+ T cells is particularly important. Trimethoprim-sulfamethoxazole (TMP/SMX) for Pj pneumonia (PJP) prophylaxis is generally discontinued when the CD4+ T-cell count is >200/μL. Here we report the first case, to our knowledge, of PJP in a patient with a CD4+ T cell count of >200/μL after CAR-T cell therapy. Case: A 14-year-old girl developed hemophagocytic lymphohistiocytosis (HLH) after cord blood transplantation (CBT) for relapsed precursor B-cell acute lymphoblastic leukemia (B-ALL). Twenty-one months after CBT, she was diagnosed with combined second relapse in the bone marrow and central nervous system. The patient was treated with CD19-targeted CAR-T cell therapy for the relapse. After CAR-T cell therapy, the patient remained in remission and continued to receive TMP/SMX for PJP prophylaxis. Seven months after CAR-T cell therapy, CD4+ T cells recovered and TMP/SMX was discontinued. The B-cell aplasia persisted. Ten months after CAR-T cell therapy, the patient developed PJP. The patient was also considered to have macrophage hyperactivation at the onset of PJP. Treatment with immunoglobulin, TMP/SMX, and prednisolone was initiated, and the patient's symptoms rapidly ameliorated. Conclusion: The patient in the present case developed PJP despite a CD4+ T-cell count of >200/μL after CAR-T cell therapy, probably because of inadequate CD4+ T-cell activation caused by B-cell depletion after CAR-T cell therapy and repeated abnormal macrophage immune responses after CBT. It is important to determine the duration of TMP/SMX for prophylaxis after CAR-T cell therapy according to each case, as well as the CD4+ T-cell count.

Chronic myeloid leukemia (CML) is a rare myeloproliferative disease in children. The primary cause of CML is the chimeric BCR::ABL1 gene in hematopoietic stem cells, which leads to leukocytosis, platelet proliferation, and splenomegaly. Lately, tyrosine kinase inhibitors (TKIs) have replaced hematopoietic cell transplantation, which was previously considered the only curative therapy, as the first-line treatment for chronic-phase CML. However, the clinical efficacy of TKIs, including those effective in adult CML, has not been well-investigated in pediatric CML. This review describes the recommended TKI-based management strategies for pediatric CML according to the literature and guidelines. Furthermore, we discuss the prospects for TKI discontinuation to avoid important adverse events, such as growth impairment, in children.

A 4-year-old boy with an abdominal mass extending from the spleen to the lower umbilicus was diagnosed with Burkitt lymphoma stage III. Because the fluorodeoxyglucose uptake on positron emission tomography (PET)-computed tomography of the residual splenic tumor remained elevated, splenectomy was performed. The PET-positive area was composed of inflammatory infiltrates, whereas the PET-negative area was composed of a viable tumor surrounded by necrotic or dying tumor cells. The residual tumor may have been false-negative for PET because of its poor proliferative potential. In this case, the comparison of PET-computed tomography and pathologic findings demonstrates the simultaneous presence of a false-positive inflammatory lesion and a false-negative residual tumor.

Anaplastic large cell lymphoma (ALCL) is a rare form of non-Hodgkin's lymphoma (NHL) in children, accounting for 10-15% of all NHL cases. ALCL is currently classified as follows: systemic anaplastic lymphoma kinase (ALK)-positive, systemic ALK-negative, primary cutaneous, and breast implant-associated ALCL. In children, systemic ALK-positive ALCL is the most common, and patients often present with extranodal involvement. We report a rare case of systemic ALK-positive ALCL with primary bone involvement in a 15-year-old male patient. Primary bone lymphoma is most commonly observed in diffuse large B-cell lymphoma and is extremely rare in systemic ALCL. Therefore, the clinical features and prognosis of primary bone ALCL remain unclear. Our patient had spontaneous remission of primary maxillary bone ALCL after gingival scraping but relapsed 12 months later with rib metastasis. Spontaneous remission of ALCL has been reported frequently in primary cutaneous ALCL and rarely in systemic ALCL. Our case demonstrates for the first time that systemic ALCL can also present as solitary bone involvement that can spontaneously remit. Because systemic ALCL is aggressive and has a risk of relapse, as in our case, it is important to consider ALCL in the differential diagnosis of primary bone lesions and to make a precise pathological diagnosis.

Purpose: Primary central nervous system (CNS) rhabdomyosarcoma is a rare mesenchymal tumor predominantly seen in children and associated with a poor outcome. We report a case of primary CNS rhabdomyosarcoma with PAX3-NCOA2 fusion and present a systematic meta-review of primary CNS rhabdomyosarcoma to characterize this rare tumor. Methods: We present the case of a 6-year-old boy with primary CNS rhabdomyosarcoma in the posterior fossa. In a systematic meta-review, we compare the demographic data of primary CNS rhabdomyosarcoma with data of rhabdomyosarcoma at all sites from the SEER database and analyze clinical factors associated with survival outcome. Results: Our patient underwent gross total resection and received vincristine, actinomycin-D, cyclophosphamide with early introduction of concurrent focal radiation and remained alive with no evidence of disease for 2 years after the end of therapy. Histopathological review revealed embryonal-type rhabdomyosarcoma, and whole-transcriptome analysis revealed PAX3 (EX6)-NCOA2 (EX12) fusion. In all, 77 cases of primary CNS rhabdomyosarcoma were identified through the meta-review. The demographic data of primary CNS rhabdomyosarcoma were similar to data of rhabdomyosarcoma at all sites. Overall and event-free survival outcomes were available for 64 and 56 patients, respectively, with a 3-year OS of 29.0% and a 3-year EFS of 25.7%. The group that received trimodal treatment exhibited better survival outcomes, with a 3-year OS of 57.4% and a 3-year EFS of 46.3%. Conclusions: Primary CNS rhabdomyosarcoma shares common histological, molecular, and demographic features with non-CNS rhabdomyosarcoma. A trimodal treatment approach with early introduction of radiation therapy may result in favorable survival outcomes.

Cytokine release syndrome (CRS) is one of the major acute complications caused by massive cytokine release after chimeric antigen receptor (CAR) T-cell therapy. Patients with tumor masses were considered at high risk of local CRS induced by the expansion of CAR T cells in the tumor masses. However, even patients without any tumor burden around the neck are at risk of developing cervical edema as local CRS, which can lead to life-threatening airway obstruction. Here, we present the case of a 15-year-old boy who developed cervical edema as a local CRS after CAR T-cell therapy for refractory acute lymphoblastic leukemia. Despite administration of tocilizumab and methylprednisolone for persistent fever as a symptom of systemic CRS after CAR T-cell therapy, cervical edema occurred and extended to the larynx, resulting in dysphagia and hoarseness. Dexamethasone was remarkably effective, and the laryngeal symptoms resolved within a few hours. Local cytokine syndrome showed exacerbation with tocilizumab but exhibited considerable improvement with dexamethasone administration.

Background: Patients with Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL) have a poor prognosis. In Ph+ALL04, allogeneic hematopoietic stem cell transplantation (HSCT) in first complete remission (CR) was indicated for all patients, and was performed in those who remained in CR at the scheduled time of transplantation, with 4-year event-free survival (EFS) and overall survival (OS) rates of 54% (95% confidence interval [CI]: 38%–68%) and 78% (95% CI: 62%–88%), respectively. Procedure: The Japan Children's Cancer Group conducted ALL-Ph13, a multicenter single-arm Phase 2 clinical trial, to improve outcomes and reduce HSCTs by using chemotherapy with tyrosine kinase inhibitors (TKIs) guided by minimal residual disease (MRD). The primary endpoint was the 3-year EFS rate. Results: Between 2013 and 2017, 41 of 43 enrolled patients with Ph+ ALL aged 1–19 years were eligible. Imatinib was started on Day 15 of induction and switched to dasatinib if MRD-positive after consolidation IB. TKIs were administered until the end of maintenance treatment (Week 104), with temporary discontinuation due to the severity of nonhematological adverse events and resumption at 80% of the original dose. When MRD was positive after the three HR blocks, HSCT was performed. Following four sepsis-related deaths, the protocol was amended in 2016, after which no such deaths occurred. Six patients (15%) underwent HSCT in the first CR, one per protocol indication and five without. The 3-year EFS and OS rates were 65% (95% CI: 48%–78%) and 85% (95% CI: 70%–93%), respectively. As several relapses occurred beyond 3 years, the 5-year EFS and OS rates were also calculated: 48% (95% CI: 30%–64%) and 85% (95% CI: 70%–93%), respectively. Conclusions: Compared with Ph+ALL04, HSCT was substantially reduced in ALL-Ph13 while maintaining comparable outcomes. Further optimization of treatment, particularly the duration of TKI administration, is needed to maintain long-term EFS.

Background: The feasibility of tyrosine kinase inhibitor (TKI) discontinuation in pediatric chronic myeloid leukemia (CML) remains to be fully elucidated. Procedures: TKI was prospectively discontinued in patients who were diagnosed with CML at <20 years of age, treated with TKI for ≥3 years, and sustained molecular response 4.0 (MR4.0) for ≥2 years. Molecular relapse was defined as a single loss of major molecular response (MMR) (BCR-ABL1IS >0.1%). Relapsed patients resumed the same TKI therapy administered before discontinuation. Results: Twenty-two patients with chronic-phase CML were enrolled, and the median ages at diagnosis and at TKI discontinuation were 9 (range: 1–14) years and 16 (5–26) years, respectively. The median follow-up time after TKI discontinuation was 37 months (range: 24–41 months). The median duration of TKI treatment before discontinuation was 100 (42–178) months, and that of MR4.0 was 53.5 (25–148) months. The treatment-free remission (TFR) rate at 12 months was 50.0% (90% confidence interval: 31.7%–65.8%). Eleven patients experienced loss of MMR within 4 months after TKI discontinuation and resumed TKI as originally prescribed. No progression was observed, and all 11 patients regained MR4.0 after TKI resumption. No patient had a withdrawal syndrome. The quality-of-life analysis suggested that successful TFR may improve academic performance in some patients. In patients who discontinued TKI therapy before puberty, the possibility of improvement in growth velocity upon TKI discontinuation was observed. Conclusions: TKI could be discontinued safely in patients with pediatric CML showing a sustained deep MR.

Chronic myeloid leukemia (CML) is a rare disease during childhood, and accelerated phase (AP) and blast phase (BP) CML, also called advanced phases, are even rarer. We retrospectively collected and analyzed clinical data of children younger than 20 years with de novo advanced-phase CML between 1996 and 2017 in Japan. Median follow-up time was 8.9 years for AP-CML (n = 15) and 3.7 years for BP-CML (n = 32). The 5-year overall survival (OS) was 93.3% for AP-CML, and 100.0% for patients who received tyrosine kinase inhibitors (TKIs) in first-line therapy (n = 10). Four of the ten patients who received TKIs in first-line therapy remained in molecular remission without transplantation (median follow-up 5.5 years). The 5-year OS of patients with BP-CML was 79.0%, and most patients received chemotherapy before transplantation, with regimen selection based on blast immunophenotype. Furthermore, among patients who received transplantation after TKI therapy, the 5-year OS was 100.0% for AP and 84.8% for BP. In conclusion, our study confirmed excellent outcomes in children with de novo advanced-phase CML, especially in the TKI-era.

The treatment strategy for children and adolescents with chronic myeloid leukemia in the chronic phase (CML-CP) has evolved from allogeneic hematopoietic stem cell transplantation (HSCT) to tyrosine kinase inhibitors (TKIs). With the advent of next-generation TKIs and new targeted therapies in the CML field, an international pediatric CML expert panel provides recommendations based on the medical literature (including previous pediatric guidelines), national standards, and treatment principles used in adults with CML-CP. Recommendations include diagnosis of the disease and details on managing the initial steps of care of children and adolescents with newly diagnosed CML-CP, including complications such as leukostasis. The treatment recommendations are based on the initiation of therapy with a first- or second-generation TKI according to the allocated European Treatment and Outcome Study (EUTOS) long-term survival score risk group of the patient. The subsequent steps are based on the results of recommended monitoring which can justify a switch to another TKI or a drug in development if there is resistance or toxicity. The panel also provides recommendations regarding the discontinuation criteria for TKIs in children and adolescents in sustained deep molecular response. Allogeneic HSCT is not recommended as the first-line of treatment for children with CML-CP but is to be considered in case of progression to the advanced phase or failure of several lines of treatment. The present treatment and management recommendations are intended to provide advice to clinicians in view of optimizing the care and the outcome of children and adolescents with CML-CP.

© 2019 by The American Society of Hematology. DISCLOSURES: Kada: Bayer Yakuhin: Other: personal fees for a member of independent data monitoring committee of clinical trials, outside of the submitted work.. Imai:Juno Therapeutics: Patents & Royalties.

© 2018 by The American Society of Hematology. Eradication of chemotherapy-resistant leukemia stem cells is expected to improve treatment outcomes in patients with acute myelogenous leukemia (AML). In a mouse model of AML expressing the MOZ-TIF2 fusion, we found that Ring1A and Ring1B, components of Polycomb repressive complex 1, play crucial roles in maintaining AML stem cells. Deletion of Ring1A and Ring1B (Ring1A/B) from MOZ-TIF2 AML cells diminished self-renewal capacity and induced the expression of numerous genes, including Glis2. Overexpression of Glis2 caused MOZ-TIF2 AML cells to differentiate into mature cells, whereas Glis2 knockdown in Ring1A/B-deficient MOZ-TIF2 cells inhibited differentiation. Thus, Ring1A/B regulate and maintain AML stem cells in part by repressing Glis2 expression, which promotes their differentiation. These findings provide new insights into the mechanism of AML stem cell homeostasis and reveal novel targets for cancer stem cell therapy.

Chromosomal translocations that involve the monocytic leukemia zinc finger (MOZ) gene are typically associated with human acute myeloid leukemia (AML) and often predict a poor prognosis. Overexpression of HOXA9, HOXA10, and MEIS1 was observed in AML patients with MOZ fusions. To assess the functional role of HOX upregulation in leukemogenesis by MOZ-TIF2, we focused on bromodomain-PHD finger protein 1 (BRPF1), a component of the MOZ complex that carries out histone acetylation for generating and maintaining proper epigenetic programs in hematopoietic cells. Immunoprecipitation analysis showed that MOZ-TIF2 forms a stable complex with BRPF1, and chromatin immunoprecipitation analysis showed that MOZ-TIF2 and BRPF1 interact with HOX genes in MOZ-TIF2-induced AML cells. Depletion of BRPF1 decreased the MOZ localization on HOX genes, resulting in loss of transformation ability induced by MOZ-TIF2. Furthermore, mutant MOZ-TIF2 engineered to lack histone acetyltransferase activity was incapable of deregulating HOX genes as well as initiating leukemia. These data indicate that MOZ-TIF2/BRPF1 complex upregulates HOX genes mediated by MOZ-dependent histone acetylation, leading to the development of leukemia. We suggest that activation of BRPF1/HOX pathway through MOZ HAT activity is critical for MOZ-TIF2 to induce AML. © The Japanese Society of Hematology 2013.

Objective: To determine the extent of growth impairment resulting from imatinib treatment in children with chronic myeloid leukemia (CML). Study design: Clinical records of 48 chronic-phase CML children administered imatinib as the first-line therapy between 2001 and 2006 were analyzed retrospectively. Cumulative change in height was assessed using the height height-SDS and converted height data from age- and sex-adjusted Japanese norms. Results: A decrease in height-SDS was observed in 72.9% of children, with a median maximum reduction in height-SDS of 0.61 during imatinib treatment. Median follow-up time was 34 months (range, 10-88 months). Growth impairment was seen predominantly in children who started imatinib at a prepubertal age compared with those who started at pubertal age. Growth velocity tended to recuperate in prepubertal children with growth impairment, as they reached pubertal age, suggesting that imatinib had little impact on growth during puberty. Conclusions: Growth impairment was a major adverse effect of long-term imatinib treatment in children with CML. We report the distinct inhibitory effect of imatinib on growth in prepubertal and pubertal children with CML. We should be aware of growth deceleration in children, especially in young children given imatinib before puberty and subjected to prolonged exposure. © 2011 Mosby Inc. All rights reserved.

Objective: Hematopoietic stem cells are kept in a quiescent state in the hypoxic area of the bone marrow, which is essential for hematopoietic stem cell maintenance. However, when and how hematopoietic stem cells acquire their hypoxic state and maintain quiescence has not been fully elucidated. The aim of this study was to understand this process in human hematopoietic stem cells after bone marrow transplantation. Materials and Methods: Human CD34-positive cord blood cells were transplanted into nonobese diabetic/severe combined immunodeficient interleukin-2 receptor γ chain knockout mice. Cell cycle and hypoxia assay analyses were performed, to identify changes in the characteristics of human hematopoietic stem cells following transplantation. Quantitative real-time reverse transcription polymerase chain reaction analysis was used to analyze the transcriptional changes accompanying this transition. Results: Engrafted primitive lineage-negative CD34-positive CD38-negative cells acquired hypoxic state and quiescence in the recipient bone marrow between 4 and 8 weeks, and between 8 and 12 weeks after transplantation, respectively. During 4 and 8 weeks after transplantation, changes in the transcription levels of G0 regulatory factors, such as CCNC and RBL1, and stem cell regulators, such as Flt3, were also seen, which may be related to the characteristic changes in the cell cycle or oxygenation state. Conclusions: Behavioral changes of hematopoietic stem cells in their cell cycle and oxygenation state during and after bone marrow engraftment may provide insights into hematopoietic stem cell regulation, mediating the improvement of clinical hematopoietic stem cell transplantation protocols and the eradication of leukemia stem cells. © 2010 ISEH - Society for Hematology and Stem Cells.

Hematopoietic stem cells (HSCs) are sustained in a specific microenvironment known as the stem cell niche. Mammalian HSCs are kept quiescent in the endosteal niche, a hypoxic zone of the bone marrow (BM). In this study, we show that normal HSCs maintain intracellular hypoxia and stabilize hypoxia-inducible factor-1α (HIF-1α) protein. In HIF-1α-deficient mice, the HSCs lost their cell cycle quiescence and HSC numbers decreased during various stress settings including bone marrow transplantation, myelosuppression, or aging, in a p16Ink4a/p19 Arf-dependent manner. Overstabilization of HIF-1α by biallelic loss of an E3 ubiquitin ligase for HIF-1α (VHL) induced cell cycle quiescence in HSCs and their progenitors but resulted in an impairment in transplantation capacity. In contrast, monoallelic loss of VHL induced cell cycle quiescence and improved BM engraftment during bone marrow transplantation. These data indicate that HSCs maintain cell cycle quiescence through the precise regulation of HIF-1α levels. © 2010 Elsevier Inc.

The relationship between trough plasma concentrations and daily doses of voriconazole was retrospectively analyzed in ≤18-year-old children because optimal oral voriconazole dosages for children, especially <2 years of age, is unknown. We demonstrated that the relationship changed around the age of 3 years, and that children <3 years of age required higher optimal daily doses with greater variations compared with those for older children, resulting in complicated optimal dose adjustments. Therefore, plasma concentration monitoring and individual dose adjustments are recommended for optimal and less toxic voriconazole treatments, especially for <3-year-old children, although additional studies are needed to validate this approach. © 2010 Wiley-Liss, Inc.

Leukemias and other cancers possess self-renewing stem cells that help to maintain the cancer. Cancer stem cell eradication is thought to be crucial for successful anticancer therapy. Using an acute myeloid leukemia (AML) model induced by the leukemia-associated monocytic leukemia zinc finger (MOZ)-TIF2 fusion protein, we show here that AML can be cured by the ablation of leukemia stem cells. The MOZ fusion proteins MOZ-TIF2 and MOZ-CBP interacted with the transcription factor PU.1 to stimulate the expression of macrophage colony-stimulating factor receptor (CSF1R, also known as M-CSFR, c-FMS or CD115). Studies using PU.1-deficient mice showed that PU.1 is essential for the ability of MOZ-TIF2 to establish and maintain AML stem cells. Cells expressing high amounts of CSF1R (CSF1R high cells), but not those expressing low amounts of CSF1R (CSF1R low cells), showed potent leukemia-initiating activity. Using transgenic mice expressing a drug-inducible suicide gene controlled by the CSF1R promoter, we cured AML by ablation of CSF1R high cells. Moreover, induction of AML was suppressed in CSF1R-deficient mice and CSF1R inhibitors slowed the progression of MOZ-TIF2-induced leukemia. Thus, in this subtype of AML, leukemia stem cells are contained within the CSF1R high cell population, and we suggest that targeting of PU.1-mediated upregulation of CSF1R expression might be a useful therapeutic approach.

Protein-losing enteropathy (PLE) is frequently complicated in patients with gastrointestinal tract-involved Langerhans cell histiocytosis (LCH); however, LCH per se is not generally included in the list of diseases that cause PLE. We report here a case of infantile PLE that presented with continuous diarrhea at the onset of LCH. She was initially diagnosed as having allergic gastroenteropathy and, thus, received intravenous prednisolone, which was thought to have induced immunodeficiency and consequently resulted in lifethreatening cytomegalovirus-associated hemophagocytic syndrome and disseminated intravascular coagulation. Because chemotherapy for hemophagocytic syndrome was transiently effective for underlying LCH as well, the diagnosis of LCH was delayed until its recurrence. Gastrointestinal tract-involved LCH, a rare but highly fatal disease, should be considered for infants with refractory gastrointestinal symptoms, especially for those with PLE; endoscopic biopsy is strongly recommended for immediate diagnosis. Copyright © 2010 by the American Academy of Pediatrics.