Cytokine profiling in 128 patients with transient abnormal myelopoiesis: a report from the JPLSG TAM-10 trial.

Transient abnormal myelopoiesis (TAM) occurs in 10% of neonates with Down syndrome (DS). Although most patients show spontaneous resolution of TAM, early death occurs in approximately 20% of cases. Therefore, new biomarkers are needed to predict early death and determine therapeutic interventions. This study aimed to determine the association between clinical characteristics and cytokine levels in patients with TAM. A total of 128 patients with DS with TAM enrolled in the TAM-10 study conducted by the Japanese Pediatric Leukemia/Lymphoma Study Group were included in this study. Five cytokine levels [interleukin (IL)-1b, IL-1 receptor agonist, IL-6, IL-8, and IL-13] were significantly higher in patients with early death than in those with non-early death. Cumulative incidence rates (CIR) of early death were significantly associated with high levels of the five cytokines. Based on unsupervised consensus clustering, patients were classified into three cytokine groups: hot-1 (n = 37), hot-2 (n = 42), and cold (n = 49). The CIR of early death was significantly different between the cytokine groups [hot-1/2 (n = 79); cold (n = 49); CIR (95% confidence interval [CI]) = 16.5% (7.9%-24.2%); 2.0% (0.0%-5.9%), P = 0.013]. Furthermore, cytokine groups (hot-1/2 vs. cold) were independent poor prognostic factors in the multivariable analysis for early death [hazard ratio (95% CI) = 19.25 (2.056-180.3), P = 0.010]. These results provide valuable information that cytokine level measurement was useful in predicting early death in patients with TAM and might help to determine the need for therapeutic interventions.

Landscape of driver mutations and their clinical effects on Down syndrome-related myeloid neoplasms.

Transient abnormal myelopoiesis (TAM) is a common complication in newborns with Down syndrome (DS). It commonly progresses to myeloid leukemia (ML-DS) after spontaneous regression. In contrast to the favorable prognosis of primary ML-DS, patients with refractory/relapsed ML-DS have poor outcomes. However, the molecular basis for refractoriness and relapse, and the full spectrum of driver mutations in ML-DS remain largely unknown. We conducted a genomic profiling study of 143 TAM, 204 ML-DS, and 34 non-DS acute megakaryoblastic leukemia cases, including 39 ML-DS cases analyzed by exome sequencing. Sixteen novel mutational targets were identified in ML-DS samples. Of these, inactivations of IRX1 (16.2%) and ZBTB7A (13.2%) were commonly implicated in the upregulation of the MYC pathway and were potential targets for ML-DS treatment with bromodomain-containing protein 4 inhibitors. Partial tandem duplications of RUNX1 on chromosome 21 were also found, specifically in ML-DS samples (13.7%), presenting its essential role in DS leukemia progression. Finally, in 177 patients with ML-DS treated following the same ML-DS protocol (the Japanese Pediatric Leukemia and Lymphoma Study Group AML-D05/D11), CDKN2A, TP53, ZBTB7A, and JAK2 alterations were associated with a poor prognosis. Patients with CDKN2A deletions (n = 7) or TP53 mutations (n = 4) had substantially lower 3-year event-free survival [28.6% vs. 90.5%, P < 0.001; 25.0% vs. 89.5%, P < 0.001] than those without these mutations. These findings considerably change the mutational landscape of ML-DS, provide new insights into the mechanisms of progression from TAM to ML-DS, and help identify new therapeutic targets and strategies for ML-DS.

HLA-haploidentical T-cell receptor αßT/B-cell-depleted stem cell transplantation for Fanconi anemia.

HLA-haploidentical stem cell transplantation (haplo-SCT) using post-transplant high-dose cyclophosphamide (PT-CY) is an alternative choice when a suitable donors is unavailable. However, PT-CY is difficult in patients with Fanconi anemia (FA) due to their high vulnerability to alkylating agents. For FA, we prefer haplo-SCT by T-cell receptor αßT-cell and B-cell depletion (αßT/B-depleted haplo-SCT), which can reduce the risks of PT-CY-related complications and graft-versus-host disease (GVHD). An 11-year-old boy with diagnosed FA (FANCG mutation) and bone marrow failure was to receive αßT/B-depleted haplo-SCT from his father (HLA 4/8 allele matched) due to absence of an HLA-matched donors. αßT/B-depleted peripheral blood stem cells (CD34 + cell count, 1.17 × 107/kg; αß + T-cell count, 1.3 × 105/kg) were infused following conditioning consisting of fludarabine (150 mg/m2), cyclophosphamide (40 mg/kg), anti-thymocyte globulin (5 mg/kg), rituximab (375 mg/m2), and thoraco-abdominal irradiation (3 Gy). Tacrolimus was used for GVHD prophylaxis until day + 30. Neutrophil engraftment was achieved on day + 9, and complete chimerism was confirmed on days + 28 and + 96. At 12-month post-SCT, the patient was well without GVHD or any other complications. αßT/B-depleted haplo-SCT is a good choice not only for patients unsuitable for PT-CY, but also for all pediatric recipients to reduce SCT-related complications.

TBI, etoposide, and cyclophosphamide conditioning for intermediate-risk relapsed childhood acute lymphoblastic leukemia.

BACKGROUND: In children with intermediate-risk relapsed acute lymphoblastic leukemia (ALL), allogeneic hematopoietic stem cell transplantation (allo-HSCT) has markedly improved the outcome of patients with an unsatisfactory minimal residual disease (MRD) response. Total body irradiation (TBI), etoposide (ETP), and cyclophosphamide (CY) have been shown to be equivalent to or better than TBI + ETP for conditioning, so we hypothesized that even greater survival could be achieved due to recent advances in HSCT and supportive care. PROCEDURE: We prospectively analyzed the efficacy and safety of allo-HSCT with a unified conditioning regimen of TBI + ETP + CY in children with intermediate-risk relapsed ALL, based on MRD in the bone marrow after induction, from the Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG) ALL-R08-II nationwide cohort (UMIN000002025). RESULTS: Twenty patients with post-induction MRD ≥ 10-3 and two not evaluated for MRD underwent allo-HSCT. Engraftment was confirmed in all patients, and no transplantation-related mortality was observed. The 3-year event-free survival and overall survival rates after transplantation were 86.4% ± 7.3% and 95.5% ± 4.4%, respectively. CONCLUSION: Allo-HSCT based on post-induction MRD with TBI + ETP + CY conditioning was feasible in Japanese children with intermediate-risk relapsed ALL.

Acute monocytic leukemia with KMT2A::LASP1 developed 9 months after diagnosis of acute megakaryoblastic leukemia in a 2-year-old boy.

Acute myeloid leukemia (AML) is known as one of the subsequent malignant neoplasms that can develop after cancer treatment, but it is difficult to distinguish from relapse when the preceding cancer is leukemia. We report a 2-year-old boy who developed acute megakaryoblastic leukemia (AMKL, French-American-British classification [FAB]: M7) at 18 months of age and achieved complete remission with multi-agent chemotherapy without hematopoietic stem cell transplantation. Nine months after diagnosis and 4 months after completing treatment for AMKL, he developed acute monocytic leukemia (AMoL) with the KMT2A::LASP1 chimeric gene (FAB: M5b). The second complete remission was achieved using multi-agent chemotherapy and he underwent cord blood transplantation 4 months after AMoL was diagnosed. He is currently alive and disease free at 39 and 48 months since his AMoL and AMKL diagnoses, respectively. Retrospective analysis revealed that the KMT2A::LASP1 chimeric gene was detected 4 months after diagnosis of AMKL. Common somatic mutations were not detected in AMKL or AMoL and no germline pathogenic variants were detected. Since the patient's AMoL was different from his primary leukemia of AMKL in terms of morphological, genomic, and molecular analysis, we concluded that he developed a subsequent leukemia rather than a relapse of his primary leukemia.

Outcome of hematopoietic stem cell transplantation in pediatric patients with acute lymphoblastic leukemia not in remission enrolled in JACLS ALL-02.

Hematopoietic stem cell transplantation (HSCT) is only indicated for acute lymphoblastic leukemia (ALL) patients for whom other treatments are unlikely to be curative. However, outcomes of patients not in complete remission (CR) at HSCT remain very poor. To improve the outcomes of patients receiving HSCT, it is important to obtain detailed clinical information about patients with ALL receiving HSCT in CR and not in CR. Patients enrolled in the Japan Association of Childhood Leukemia Study ALL-02 who underwent HSCT and were not in CR (non-CR patients, n = 55) were examined. The 1-year overall survival (OS) rate of non-CR patients was 27.3%. Compared with CR patients, non-CR patients experienced very early and early relapse significantly more frequently and had poorer prognostic factors. Most interestingly, high hyperdiploid (HHD) patients showed an excellent 1-year OS of 80%. In addition, long-term survival among surviving HHD patients was longer than 5 years. All eight patients who survived after undergoing HSCT while not in CR were younger than 10 years at initial diagnosis and were negative for central nervous system involvement. While limited, these results suggest that a subset of patients may benefit from HSCT while not in CR.

Nelarabine, intensive L-asparaginase, and protracted intrathecal therapy for newly diagnosed T-cell acute lymphoblastic leukaemia in children and young adults (ALL-T11): a nationwide, multicenter, phase 2 trial including randomisation in the very high-risk group.

BACKGROUND: T-cell acute lymphoblastic leukaemia has distinct biological characteristics and a poorer prognosis than B-cell precursor acute lymphoblastic leukaemia. This trial aimed to reduce the rate of radiation and haematopoietic stem-cell transplantation (HSCT) while improving outcomes by adding nelarabine, intensified L-asparaginase, and protracted intrathecal therapy in the Berlin-Frankfurt-Münster (BFM)-type treatment. METHODS: In this nationwide, multicenter, phase 2 trial, we enrolled patients with newly diagnosed T-cell acute lymphoblastic leukaemia (age <25 years at diagnosis) conducted by Japan Children's Cancer Group and Japan Adult Leukemia Study Group. Patients were stratified into standard-risk, high-risk, and very-high-risk groups according to prednisolone response, CNS status, and end-of-consolidation minimal residual disease. We used the Associazione Italiana di Ematologia Oncologia Pediatrica (AIEOP)-BFM-ALL 2000-backbone chemotherapy. Nelarabine (650 mg/m2 per day for 5 days) was given to high-risk and very high-risk patients. All patients received, until the measurement of end-of-consolidation minimal residual disease, an identical therapy schedule, which included the prednisolone pre-phase remission induction therapy with dexamethasone (10 mg/m2 per day, for 3 weeks [for patients <10 years] or for 2 weeks including a 7-day off interval [for patients ≥10 years]) instead of prednisolone, and consolidation therapy added with Escherichia coli-derived L-asparaginase. On the basis of the stratification, patients received different intensities of treatment; L-asparaginase-intensified standard BFM-type therapy for standard risk and nelarabine-added high risk BFM-type therapy for high risk. In the very high-risk group, patients were randomly assigned (1:1) to group A (BFM-based block therapy) and group B (another block therapy, including high-dose dexamethasone) stratified by hospital, age (≥18 years or <18 years), and end-of-induction bone marrow blast percentage of M1 (<5%) or M2 (≥5%, <25%)+M3 (≥25%). Cranial radiotherapy was limited to patients with overt CNS disease at diagnosis (CNS3; >5 white blood cells per µL with blasts) and patients with no evidence of CNS disease received protracted triple intrathecal therapy. Only very high-risk patients were scheduled to receive HSCT. The primary endpoint was 3-year event-free survival for the entire cohort and the proportion of patients with disappearance of minimal residual disease between randomly assigned groups A and B in the very high-risk group. Secondary endpoints were overall survival, remission induction rate, and occurrence of adverse events. 3 years after the completion of patient accrual, a primary efficacy analysis was performed in the full analysis set and the per-protocol set. This study is registered with the Japan Registry of Clinical Trials, jRCTs041180145. FINDINGS: Between Dec 1, 2011, and Nov 30, 2017, of 349 eligible patients (median age 9 years [IQR 6-13]), 238 (68%) were male, and 28 (8%) patients had CNS3 status. 168 (48%) patients were stratified as standard risk, 103 (30%) as high risk, 39 (11%) as very high risk, and 39 (11%) as no risk (patients who had off protocol treatment before risk assessment. The composite complete remission (complete remission plus complete remission in suppression) rate after remission induction therapy was 89% (298 of 335 patients). HSCT was performed in 35 (10%) of 333 patients. With a median follow-up of 5·2 years (IQR 3·6-6·7), 3-year event-free survival was 86·4% (95% CI 82·3-89·7%) and 3-year overall survival was 91·3% (87·7-93·8%). The proportion of minimal residual disease disappearance was 0·86 (12 of 14 patients; 95% CI 0·57-0·98) in group A and 0·50 (6 of 12 patients, 0·21-0·79) in group B. Grade 3 peripheral motor neuropathy was seen in 11 (3%) of 349 patients and sensory neuropathy was seen in 6 (2%) patients. The most common grade 3 or worse adverse event was febrile neutropenia (294 [84%] of 349 patients). Treatment-related death occurred in three patients due to sepsis, gastric perforation, or intracranial haemorrhage during remission induction. INTERPRETATION: The ALL-T11 protocol produced encouraging outcomes with acceptable toxicities despite limited cranial radiotherapy and HSCT use. FUNDING: Ministry of Health, Labor and Welfare of Japan, and Japan Agency for Medical Research and Development. TRANSLATION: For the Japanese translation of the abstract see Supplementary Materials section.

Safety and efficacy of post-haematopoietic cell transplantation maintenance therapy with blinatumomab for relapsed/refractory CD19-positive B-cell acute lymphoblastic leukaemia: protocol for a phase I-II, multicentre, non-blinded, non-controlled trial (JPLSG SCT-ALL-BLIN21).

INTRODUCTION: Relapsed and refractory B-cell acute lymphoblastic leukaemia (R/R-B-ALL) is linked to a significant relapse rate after allogeneic haematopoietic cell transplantation (allo-HCT) in children, adolescents and young adults (CAYA). No standard treatment has been established to prevent relapse after allo-HCT for R/R-B-ALL, which is an unmet medical need. The administration of blinatumomab after allo-HCT is expected to enhance the antileukaemic effect on residual CD19-positive blasts by donor-derived CD3-positive T-cells. METHODS AND ANALYSIS: The goal of this multicentre, open-label, uncontrolled, phase I-II clinical trial is to assess the safety and effectiveness of post-transplant maintenance therapy with blinatumomab for CAYA patients (25 years old or younger) with CD19-positive R/R-B-ALL who have received allo-HCT beyond first complete remission (CR) and have CR with haematological recovery between 30 and 100 days after allo-HCT. Eighty-five paediatric institutions in Japan are participating in this study. Forty-one patients will enrol within 2.25-year enrolment period and follow-up period is 1 year. The primary endpoints are the treatment completion rate for phase I study and the 1-year graft-versus-host disease-free/relapse-free survival rate for phase II study, respectively. ETHICS AND DISSEMINATION: This research was approved by the Central Review Board at National Hospital Organization Nagoya Medical Center (Nagoya, Japan) on 21 January 2022 and was registered at the Japan Registry of Clinical Trials (jRCT) on 3 March 2022. Written informed consent is obtained from all patients and/or their guardians. The results of this study will be disseminated through peer-reviewed publications and conference presentations. TRIAL REGISTRATION NUMBER: jRCTs041210154.

Impact of asparaginase discontinuation on outcomes of children with acute lymphoblastic leukaemia receiving the Japan Association of Childhood Leukaemia Study ALL-02 protocol.

Asparaginase is an essential drug for acute lymphoblastic leukaemia (ALL) treatment, but has several side effects, and its discontinuation often compromises patient outcomes. In the prospective Japan Association of Childhood Leukaemia Study ALL-02 protocol, two major changes were made: (1) additional chemotherapies to compensate for the reduction of treatment intensity when asparaginase was discontinued and (2) more intensive concomitant corticosteroid administration, relative to our previous ALL-97 protocol. In ALL-02 study, 1192 patients were included and L-asparaginase was discontinued for 88 (7.4%). Discontinuation due to allergy was markedly decreased relative to the ALL-97 protocol (2.3% vs 15.4%). Event-free survival (EFS) among patients with T-ALL was compromised when L-asparaginase was discontinued, as well as among patients with high-risk B-cell ALL, especially when discontinued before maintenance therapy. Moreover, multivariate analysis identified discontinuation of L-asparaginase as an independent poor prognostic factor for EFS. In the current study, additional chemotherapies failed to fully compensate for L-asparaginase discontinuation, illustrating the difficulty of replacing asparaginase with other classes of drugs, although this study was not designed to evaluate the effect of these modifications. Concomitant intensive corticosteroid treatment may help to reduce allergy to asparaginase. These results will assist in further optimization of asparaginase use.

A novel Menin-MLL1 inhibitor, DS-1594a, prevents the progression of acute leukemia with rearranged MLL1 or mutated NPM1.

BACKGROUND: Mixed lineage leukemia 1-rearranged (MLL1-r) acute leukemia patients respond poorly to currently available treatments and there is a need to develop more effective therapies directly disrupting the Menin‒MLL1 complex. Small-molecule-mediated inhibition of the protein‒protein interaction between Menin and MLL1 fusion proteins is a potential therapeutic strategy for patients with MLL1-r or mutated-nucleophosmin 1 (NPM1c) acute leukemia. In this study, we preclinically evaluated the new compound DS-1594a and its salts. METHODS: We evaluated the preclinical efficacy of DS-1594a as well as DS-1594a·HCl (the HCl salt of DS-1594a) and DS-1594a·succinate (the succinic acid salt of DS-1594a, DS-1594b) in vitro and in vivo using acute myeloid leukemia (AML)/acute lymphoblastic leukemia (ALL) models. RESULTS: Our results showed that MLL1-r or NPM1c human leukemic cell lines were selectively and highly sensitive to DS-1594a·HCl, with 50% growth inhibition values < 30 nM. Compared with cytrabine, the standard chemotherapy drug as AML therapy, both DS-1594a·HCl and DS-1594a·succinate mediated the eradication of potential leukemia-initiating cells by enhancing differentiation and reducing serial colony-forming potential in MLL1-r AML cells in vitro. The results were confirmed by flow cytometry, RNA sequencing, RT‒qPCR and chromatin immunoprecipitation sequencing analyses. DS-1594a·HCl and DS-1594a·succinate exhibited significant antitumor efficacy and survival benefit in MOLM-13 cell and patient-derived xenograft models of MLL1-r or NPM1c acute leukemia in vivo. CONCLUSION: We have generated a novel, potent, orally available small-molecule inhibitor of the Menin-MLL1 interaction, DS-1594a. Our results suggest that DS-1594a has medicinal properties distinct from those of cytarabine and that DS-1594a has the potential to be a new anticancer therapy and support oral dosing regimen for clinical studies (NCT04752163).

Multi-omics analysis defines highly refractory RAS burdened immature subgroup of infant acute lymphoblastic leukemia.

KMT2A-rearranged infant acute lymphoblastic leukemia (ALL) represents the most refractory type of childhood leukemia. To uncover the molecular heterogeneity of this disease, we perform RNA sequencing, methylation array analysis, whole exome and targeted deep sequencing on 84 infants with KMT2A-rearranged leukemia. Our multi-omics clustering followed by single-sample and single-cell inference of hematopoietic differentiation establishes five robust integrative clusters (ICs) with different master transcription factors, fusion partners and corresponding stages of B-lymphopoietic and early hemato-endothelial development: IRX-type differentiated (IC1), IRX-type undifferentiated (IC2), HOXA-type MLLT1 (IC3), HOXA-type MLLT3 (IC4), and HOXA-type AFF1 (IC5). Importantly, our deep mutational analysis reveals that the number of RAS pathway mutations predicts prognosis and that the most refractory subgroup of IC2 possesses 100% frequency and the heaviest burden of RAS pathway mutations. Our findings highlight the previously under-appreciated intra- and inter-patient heterogeneity of KMT2A-rearranged infant ALL and provide a rationale for the future development of genomics-guided risk stratification and individualized therapy.

A phase III clinical trial evaluating efficacy and safety of minimal residual disease-based risk stratification for children with acute myeloid leukemia, incorporating a randomized study of gemtuzumab ozogamicin in combination with post-induction chemotherapy for non-low-risk patients (JPLSG-AML-20).

The purpose of this study is to establish a treatment with appropriate intensity for children (<16 years old at diagnosis) with de novo acute myeloid leukemia (excluding acute promyelocytic leukemia and myeloid leukemia associated with Down syndrome) according to a risk stratification based on recurrent leukemic cytogenetic abnormalities and flow-cytometric minimal residual disease at end of initial induction chemotherapy and to validate the safety and efficacy of gemtuzumab ozogamicin (GO)-combined post-induction chemotherapy for the non-low-risk (non-LR) patients. The primary endpoint of this phase III study is three-year disease-free survival rate, which will be compared between the GO and non-GO arms of the non-LR (intermediate-risk and high-risk [HR]) patients. All HR patients will be allocated to allogeneic hematopoietic stem cell transplantation in first remission. This trial has been registered at the Japan Registry of Clinical Trials (jRCTs041210015).

A pilot study of game-based learning programs for childhood cancer survivors.

BACKGROUND: Childhood cancer survivors lacking awareness on their potential risks of late effects often fail to seek adequate follow-up care. Patient education matching their preference is of great importance to improve their adherence to survivorship care. In this study, we developed two age-dependent game-based learning programs, which enable continuous approaches for childhood cancer survivors along their intellectual maturation. Then, we assessed the effectiveness of the programs. METHODS: Childhood cancer survivors over 10 years of age who regularly visited a long-term follow-up clinic were enrolled in this study. They were requested to play either of two different types of game tools, one for school children and another for adolescents and young adults, for one month at home. To evaluate the educational effects of the programs, they were examined for health management awareness, self-esteem, and knowledge on cancer-related late effects before and after the intervention with age-based questionnaires and knowledge tests. RESULTS: Among 83 participants, 49 (59.0%) completed the assessments over the period of 12 months. The health management awareness and knowledge levels increased significantly at 1-month after the intervention as compared to the baseline in both school children and adolescents/young adults (for health management awareness, p = 0.011 in elementary school children; p = 0.007 in junior high school children; p < 0.001 in adolescents/young adults; for knowledge levels, p < 0.001 in school children; p < 0.001 in adolescents/young adults). The effect was maintained for 12 months in school children while it decreased in adolescents and young adults with time. Self-esteem significantly increased at 1-month (p = 0.002 in school children; p = 0.020 in adolescents/young adults) and was maintained for 12 months in both age groups. CONCLUSION: The game-based learning programs enhanced health locus of control and self-esteem in childhood cancer survivors. The game-based learning programs could be applied effectively to survivorship care as a new modality of patient education. TRIAL REGISTRATION: This study was retrospectively registered in UMIN-CTR ( UMIN000043603 ) on March 12, 2021.

JACLS ALL-02 SR protocol reduced-intensity chemotherapy produces excellent outcomes in patients with low-risk childhood acute lymphoblastic leukemia.

Acute lymphoblastic leukemia (ALL) is the most common childhood cancer. As overall cure rates of childhood ALL have improved, reduction of overall treatment intensity while still ensuring excellent outcomes is imperative for low-risk patients. We report the outcomes of patients treated following the standard-risk protocol from the prospective Japan Association of Childhood Leukemia Study (JACLS) ALL-02 study, which was conducted between 2002 and 2008 for patients with newly diagnosed ALL aged 1-18 years. Of 1138 patients with B-cell precursor ALL, 388 (34.1%) were allocated to this protocol. Excellent outcomes were achieved despite the overall treatment intensity being lower than that of most contemporary protocols: 4 years event-free survival (EFS) was 92.3% and 4 years overall survival 98.2%. Patients with high hyperdiploidy (HHD) involving triple trisomy (trisomy of chromosomes 4, 10, and 17) or ETV6-RUNX1 had even better outcomes (4 years EFS 97.6% and 100%, respectively). Unique characteristics of this protocol include a selection of low-risk patients with a low initial WBC count and good early treatment response and reduction of cumulative doses of chemotherapeutic agents while maintaining dose density. In Japan, we are currently investigating the feasibility of this protocol while incorporating minimal residual disease into the patient stratification strategy.

Genetic features of precursor B-cell phenotype Burkitt leukemia with IGH-MYC rearrangement.

BACKGROUND: An atypical form of Burkitt leukemia/lymphoma (BL), BL with a phenotype of precursor B-cells (preBLL), is listed in the WHO Classification. Recent reports suggested that preBLL and classical BL could be distinguished by the differences in IG-MYC translocation architecture and an additional mutated genes profile. The characteristics of classical BL are IG-MYC by aberrant somatic hypermutation or class switch recombination, and BL-specific gene mutations such as MYC, ID3, and CCND3. Meanwhile, preBLL is characterized by IG-MYC due to aberrant VDJ recombination and mutations in NRAS and KRAS. However, it is not clear whether all preBLL cases can be differentiated. This report investigated the molecular characteristics of an infant preBLL case, with a more advanced stage of maturity than typical preBLL. CASE: The patient showed BL-like morphology with IGH-MYC rearrangement. In the immunophenotyping, CD20 and surface immunoglobulin were negative, whereas other markers were consistent with BL. To evaluate the genetic contribution, we performed whole-exome sequencing. The breakpoint analysis revealed the IG-MYC occurred due to an aberrant VDJ recombination. Meanwhile, additional somatic mutations were detected in FBXO11, one of the mutant genes specific to BL. In the analysis of the specimen in complete remission, mutation in KRAS, frequently mutated in preBLL, was detected with low frequency, suggesting somatic mosaicism. CONCLUSION: The present case showed the characteristics of both typical preBLL and classical BL. Because preBLL includes atypical cases such as the present case, further studies are required to elucidate preBLL features.

Successful hematopoietic stem cell transplantation with reduced dose of busulfan for Omenn syndrome.

Omenn syndrome (OS) is typically observed in the autosomal recessive form of severe combined immunodeficiency (SCID) with autoreactive manifestations, and it requires allogeneic hematopoietic stem cell transplantation. Unlike non-OS SCID, a conditioning regimen is usually required to eradicate T-cells; however, optimal conditioning regimens are not established mainly because of the rarity of OS. Here, we report a case of hematopoietic stem cell transplantation with a reduced dose of busulfan, as a conditioning regimen and successful engraftment with complete chimerism. OS was diagnosed in a one-month-old boy based on a diffuse erythematous rash, absent B-cells, and activated T-cells. Genetic analysis failed to identify causative mutations for OS/SCID, such as RAG1/2. Bone marrow transplantation was performed from his HLA-matched sister with a conditioning regimen consisting of targeted busulfan, fludarabine, and anti-thymocyte globulin. Cyclosporine had been administered before transplantation to control abnormal T-cell activation and continued for graft-versus-host disease (GVHD) prophylaxis. Engraftment was achieved on day 12, and no GVHD symptoms were observed. For stem cell transplantation for OS, prior control of autoreactive symptoms with immunosuppressants is important for safe transplantation and reduced intensity conditioning (RIC) can be an option to achieve sustained engraftment.