Rare TCF3 variants associated with pediatric B cell acute lymphoblastic leukemia.

Germline genetic variants influence development of pediatric B cell acute lymphoblastic leukemia (B-ALL). Genome-wide association studies (GWAS) have identified several pediatric B-ALL susceptibility loci. IKZF1 and PAX5, transcription factors involved in B cell development, have been reported as susceptibility genes for B-ALL development. Therefore, we hypothesized that rare variants of genes involved in B cell development would be candidate susceptibility loci for pediatric B-ALL. Thus, we sequenced TCF3, a key transcription factor gene involving in B cell development. Saliva DNA from 527 pediatric patients with pediatric B-ALL in remission who were registered with the Tokyo Children's Cancer Study Group (TCCSG) were examined. As a TCF3 gene-based evaluation, the numbers of rare deleterious germline TCF3 sequence variants in patients with pediatric B-ALL were compared with those in cancer-free individuals using data in public databases. As a TCF3 single-variant evaluation, the frequencies of rare deleterious germline TCF3 sequence variants in patients with pediatric B-ALL were also compared with those in control data. TCF3 gene-based analysis revealed significant associations between rare deleterious variants and pediatric B-ALL development. In addition, TCF3 variant-based analysis showed particularly strong association between variant rs372168347 (three in 521 TCCSG and three in the 15780 gnomAD whole genome analysis cohort, p = 0.0006) and pediatric B-ALL development. TCF3 variants are known to influence B cell maturation and may increase the risk of preleukemic clone emergence.

Plasma-derived factor VIIa and factor X mixture agent (MC710) prophylaxis in haemophilia B patients with inhibitors.

INTRODUCTION: Haemophilia B patients with factor IX inhibitors have particularly unmet needs for conventional therapy. AIM: Phase II/III clinical trial, multicentre, open-label, prospective, self-controlled study was conducted to assess MC710 prophylaxis in haemophilia B patients with inhibitors. METHODS: We enrolled haemophilia patients who had received episodic or prophylactic treatment with bypassing agents up to that time. The participants continued their conventional therapy for 24 weeks and then MC710 was prophylactically infused intravenously every 2 or 3 days at 60 to 120 µg as FVIIa per kilogram of body weight for 24 weeks. The primary endpoint was the annual bleeding rate (ABR) requiring bypassing agents, which was compared intraindividually between the conventional therapy period and the MC710 prophylaxis period. RESULTS: A total of 11 male haemophilia B patients were enrolled. The median ABR ratio for each participant (the prophylaxis period ABR divided by the conventional therapy period ABR) was .33 (2.1/6.5), range from .00 to 3.77. ABR ratios for 9 of the 11 patients ranged from .00 to .60, and 3 of the 9 patients had zero bleeding events during the prophylaxis period. Meanwhile, ABR ratios for the remaining two patients were 2.53 and 3.77, respectively. Although a fibrinogen decrease recovered by the dose reduction was reported for only one participant as the sole adverse drug reaction in this study, no thrombotic events or other safety concerns were reported. CONCLUSION: MC710 prophylaxis is considered to be decrease the bleeding rate in haemophilia B patients with inhibitors without safety concerns.

Basophil activation test for allergic and febrile non-haemolytic transfusion reactions among paediatric patients with haematological or oncological disease.

BACKGROUND AND OBJECTIVES: Allergic transfusion reactions (ATRs) and febrile non-haemolytic transfusion reactions (FNHTRs) are common, although their mechanisms remain unclear. Immunoglobulin E (IgE)-mediated type I hypersensitivity may be involved in the pathogenesis of ATR. A basophil activation test (BAT) may help elucidate this process. MATERIALS AND METHODS: The BAT was based on peripheral blood samples from paediatric patients with a haematological or oncological disease and on samples of residual blood products transfused in each case. Dasatinib was used to evaluate whether basophil activation was mediated by an IgE-dependent pathway. RESULTS: Twenty-seven patients with and 19 patients without ATR/FNHTR were included in this study, respectively. The median BAT values associated with ATR- (n = 41) and FNHTR-causing (n = 5) blood products were 22.1% (range = 6.1%-77.0%) and 27.8% (range = 15.2%-47.8%), respectively, which were higher than the median value of 8.5% (range = 1.1%-40.9%) observed in blood products without a transfusion reaction. Dasatinib suppressed basophil activity. BAT values were comparable in patients with ATR regardless of severity. Meanwhile, BAT values analysed with blood products non-causal for ATR/FNHTR were higher in patients with ATR/FNHTR than in those without. CONCLUSION: The IgE-mediated type I hypersensitivity may be involved in the pathogenesis of ATR and FNHTR. BAT analyses may help elucidate the underlying mechanisms and identify patients at risk.

A nationwide survey of late effects in survivors of juvenile myelomonocytic leukemia in Japan.

We conducted a cross-sectional study using a questionnaire to explore the late effects in survivors of allogenic hematopoietic stem cell transplantation (HSCT) for juvenile myelomonocytic leukemia (JMML). The attending pediatric hematologists/oncologists completed the questionnaires. Of the 30 survivors, approximately 83% showed more than one late effect. The identified late effects included endocrine, dental, skin, ophthalmologic, musculoskeletal, pulmonary, neurocognitive, and cardiovascular dysfunction. The prevalence of short stature, pulmonary, cardiovascular, and nephrological complications was significantly elevated among survivors who were 12 years or more lapsed after HSCT. Therefore, a multidisciplinary follow-up system for survivors of JMML is crucial.

Immature Platelet Fraction and Its Kinetics in Neonates.

Thrombocytopenia is a common abnormality encountered in the neonatal period, and immature platelet fraction (IPF) may be an informative indicator of thrombopoiesis; however, data on IPF in neonates are scarce. To define reference intervals (RIs) and factors affecting IPF in neonates, we measured the IPF of 533 consecutive neonates. With a multiple regression analysis of 330 newborns with normal platelet counts at birth, premature delivery, neonatal asphyxia, intrauterine infection, chromosomal abnormalities, and respiratory disorders were identified as independent factors for IPF%. The RIs of IPF% and absolute IPF value in neonates were determined to be 1.3% to 5.7% and 3.2 to 14.5×10 9 /L, respectively. On day 14 after birth, IPF% increased to twice the value at birth and thereafter returned to the previous value on day 28. Reticulocyte counts, in contrast, were the lowest at day 14. IPF% was increased in 16 thrombocytopenic patients with various clinical conditions, especially those with immune-mediated thrombocytopenia. IPF in neonates may be evaluated essentially based on the same RIs as in adults, although some precautions must be taken when evaluating IPF in neonates in the first 2 weeks of life. IPF may be useful for evaluating thrombopoiesis and thrombocytopenia in neonates.

Relationship between allergic transfusion reactions and allergic predisposition among pediatric patients with hematological/oncological disease.

BACKGROUND: Allergic transfusion reactions (ATRs) manifest frequently as transfusion reactions, and their onset may be related to a patient's allergic predisposition. Moreover, although pediatric patients with hematological/oncological disease are more susceptible to ATRs, the relationship between allergic predisposition and ATRs remains to be fully clarified. STUDY DESIGN AND METHODS: Patients who were diagnosed with pediatric hematological/oncological disease and received transfusion at the study institutions were included. We determined patient background information related to their allergy history, measured the levels of allergen-specific immunoglobulin E (IgE) using sera obtained on diagnosis, and analyzed their associations with ATR onset. RESULTS: Of the 363 patients analyzed, 144 developed ATRs. Multivariate analysis identified cases with high basophils in the peripheral blood, and Dermatophagoides pteronyssinus- and egg white-specific IgEs were involved in the development of ATR in all age groups. Meanwhile, a history of food allergies, and positivity for Japanese cypress- and D. pteronyssinus-specific IgEs were risk factors for developing ATRs in the <5 years age group. Moreover, patients aged 5-<10 years with a history of asthma, allergic rhinitis, pollinosis, or atopic dermatitis, and those aged ≥10 years with positivity for dog dander-specific IgE were at risk for developing ATRs. CONCLUSION: The allergic constitution of patients plays a role in ATR onset even in pediatric hematological/oncological diseases. Therefore, advance confirmation of a patient's allergic constitution may partly predict the onset of ATRs. However, since multiple allergic predispositions within complex mechanisms may be involved in the onset of ATRs, further verification is required.

Investigation of patient factors associated with the number of transfusions required during chemotherapy for high-risk neuroblastoma.

BACKGROUND: Blood transfusion is an important supportive care for high-risk neuroblastoma. When the number of transfusions increases, transfusion-associated adverse reactions may be more problematic. However, the factors determining the degree of myelosuppression and the number of transfusions during chemotherapy for high-risk neuroblastoma remain unclear. MATERIALS AND METHODS: We investigated patient factors determining the number of required transfusions in 15 high-risk neuroblastoma patients who received five courses of chemotherapy. Clinical data, cytokine profile and colony-forming assay with bone marrow samples at diagnosis were analysed. RESULTS: The required number of transfusions of both platelets and erythrocytes decreased once in the second course and then increased as the course progressed. The variability among cases increased as the chemotherapy course progressed. In cases of low peripheral blood platelet count and lower fibrinogen level at diagnosis, the number of platelet transfusions was higher during chemotherapy. In contrast, there was a negative correlation between the forming ability of granulocyte-macrophage or erythroid colonies and the number of erythrocyte transfusions in the latter period. CONCLUSION: In the early stages of chemotherapy, bone marrow infiltration in neuroblastoma and/or coagulopathy complication may cause thrombocytopenia and requirement of platelet transfusion; conversely, in the later stages, the number of erythrocyte transfusions may be defined by the patient's inherent hematopoietic ability. These factors may be useful in predicting the required number of transfusions.

Cancer among children, adolescents and young adults in the Hokushin region, Japan, between 2010 and 2015.

Adolescents and young adults with cancer encounter age-related challenges. Cancer treatment and support are not always tailored to the needs of each patient due to difficulty in the collection of accurate data. The present study aimed to investigate cancer among children and adolescents and young adults in the four adjacent prefectures of Japan (Toyama, Ishikawa, Fukui and Nagano) by analyzing data from a unique regional cancer database. We retrieved and analyzed the data of pediatric and adolescent and young adult patients aged between 0 and 39 years at cancer diagnosis (including carcinoma in situ), which was registered in the Hokushin Ganpro database between 2010 and 2015. A total of 5718 cases (1571 males and 4147 females) were identified during this period. The overall male-to-female ratio was 1:2.6. There was no distinct difference in the number of cancer cases per 100 000 population between males and females until 19 years of age. The difference became more pronounced after 20 years of age. The number of cancer cases (per 100 000 population) in the 0-14-, 15-19-, 20-29- and 30-39-year age groups was estimated to be 13.4, 14.5, 44.0 and 101.5, respectively. Carcinomas were the most common type of cancer in the adolescents and young adults (15-39 years) population (74%), whereas they were not the predominant cancer type in the pediatric (0-14 years) population. Although further research is needed to understand the needs of adolescents and young adults with cancer, we believe that our findings will help guide efforts to improve the management strategy for adolescents and young adults with cancer.

Prophylaxis Using a Mixture of Plasma-Derived Activated Factor VII and Factor X (pdFVIIa/FX) in a Patient with Hemophilia B Complicated by Inhibitors and Allergy to Factor IX Concentrates: A Case Report.

Treating patients with hemophilia and inhibitors is often problematic. The presence of inhibitors negatively impacts the effectiveness of treatment to achieve hemostasis especially in patients with hemophilia B, owing mainly to allergic reactions to factor IX (FIX) concentrates and the low success rate of immune tolerance therapy. A 9-month-old boy had intracranial hemorrhage and was diagnosed with hemophilia B. After replacement therapy, he developed inhibitors and an allergic reaction to FIX. Prophylactic therapy was initiated with recombinant activated factor VII (rFVIIa) and later switched to pdFVIIa/factor X (FX; 120 µg/kg as the FVII dose, every other day) because of a recurrence of intracranial hemorrhage. Since then, he remained well without life-threatening bleeding for more than 2 years. Our case suggests that pdFVIIa/FX may be useful for prophylactic therapy in hemophilia B complicated by inhibitors and allergic reaction to FIX concentrates.

Sequential Therapy of Inotuzumab Ozogamicin and Blinatumomab as a Bridge-to Hematopoietic Stem Cell Transplantation in a Pediatric Patient With Primary Refractory Acute Lymphoblastic Leukemia: A Case Report.

For relapsed/refractory (r/r) acute lymphocytic leukemia (ALL), there is a clinical question on how to combine blinatumomab and inotuzumab ozogamicin (InO), which are newly emerging immunotherapeutic agents, with conventional treatment. We report the case of an 11-year-old boy with B-cell ALL, who had a failed primary treatment and achieved molecular complete remission treated with a sequence therapy of InO and blinatumomab. Later, hematopoietic stem cell transplantation could be performed without major complications. Our case may suggest that the sequence therapy of InO and blinatumomab as a bridge-to hematopoietic stem cell transplantation could be effective in the treatment of pediatric r/r ALL.

Transfusion outcome for volume- and plasma-reduced platelet concentrates for pediatric patients.

BACKGROUND AND OBJECTIVES: Plasma reduction in platelet concentrate (PC) products has been reported to prevent large volume load and transfusion-related adverse reactions (TRARs). However, volume reduction might be associated with a poor transfusion response because of a deterioration in platelet (PLT) quality. Because PLT quality control and transfusion responses for recently washed PCs using PLT additive solutions are superior, we investigated the clinical safety and transfusion efficacy of volume-reduced washed PCs in pediatric patients. MATERIALS AND METHODS: We prepared a simplified resuspended PC product (RPC) as a washed PC. Regular RPC (R-RPC) included equivalent volumes of bicarbonate Ringer's solution and anticoagulant citrate dextrose solution A (BRS-A) as the resuspension solution. Half RPC (H-RPC) was prepared by adding a half volume of BRS-A. Twenty-four pediatric patients were scheduled for transfusions with R-RPC and H-RPC up to 4 times. R-RPC was transfused 42 times into 24 patients. H-RPC was transfused 41 times into 23 patients. RESULTS: Neither product was observed to cause TRARs. Although the calculated PLT recovery for H-RPC was significantly reduced, the posttransfusion corrected count increment (24 h) did not differ. Moreover, similar results were observed for vital signs during transfusion. CONCLUSION: Volume-reduced washed PC can be transfused without causing TRARs, differences in vital signs, or inferior transfusion responses. Volume-reduced washed PC also provides the advantages of shortened transfusion times and reduced volume loads. Although a standard technique for stable resuspension is necessary, volume-reduced washed PC may be a beneficial option for children, including neonates, or individuals with cardiovascular or renal problems.

Prophylactic piperacillin administration in pediatric patients with solid tumors following different intensities of chemotherapy.

BACKGROUND: Prophylactic antibiotics decrease mortality and morbidity in patients with hematological malignancies following intensive chemotherapy. However, the efficacy of prophylactic antibiotics for pediatric patients with solid tumors remains unclear. METHODS: We retrospectively assessed 103 neutropenic periods from 26 patients with neuroblastoma or brain tumors following three different intensity chemotherapy regimens (05A3, A, and B). While piperacillin was intravenously administered as prophylaxis (PIPC prophylaxis group), the historical control group received no prophylaxis. As patients exhibited a variable degree of myelosuppression based on the intensity of the chemotherapy regimen, we separately evaluated the frequency and severity of febrile neutropenia (FN) in each regimen. RESULTS: Following intensive chemotherapy, we observed a significantly lower frequency of FN in the PIPC prophylaxis group compared with the historical control group in both regimen 05A3 (20% vs 65%; P = 0.01) and regimen A (56% vs 93%; P = 0.02). We also observed a shorter duration of fever, lower maximum fever, and lower C-reactive protein levels in the PIPC prophylaxis group compared with the historical control group after regimens 05A3 and A. Conversely, the frequency and severity of FN were not different between the two groups after moderate-intensity chemotherapy (regimen B). However, a longitudinal routine surveillance study of Pseudomonas aeruginosa also indicated a reduction in the susceptibility to PIPC throughout the study period. CONCLUSIONS: Although PIPC prophylaxis might provide an advantage for severe neutropenia in pediatric patients with solid tumors, there is concern regarding bacterial resistance to antibiotics. Therefore, further careful examination is necessary for adaptation.

Essential role of PTPN11 mutation in enhanced haematopoietic differentiation potential of induced pluripotent stem cells of juvenile myelomonocytic leukaemia.

We established mutated and non-mutated induced pluripotent stem cell (iPSC) clones from a patient with PTPN11 (c.226G>A)-mutated juvenile myelomonocytic leukaemia (JMML). Both types of iPSCs fulfilled the quality criteria. Mutated iPSC colonies generated significantly more CD34+ and CD34+ CD45+ cells compared to non-mutated iPSC colonies in a culture coated with irradiated AGM-S3 cells to which four growth factors were added sequentially or simultaneously. The haematopoietic differentiation potential of non-mutated JMML iPSC colonies was similar to or lower than that of iPSC colonies from a healthy individual. The PTPN11 mutation coexisted with the OSBP2 c.389C>T mutation. Zinc-finger nuclease-mediated homologous recombination revealed that correction of PTPN11 mutation in iPSCs with PTPN11 and OSBP2 mutations resulted in reduced CD34+ cell generation to a level similar to that obtained with JMML iPSC colonies with the wild-type of both genes, and interestingly, to that obtained with normal iPSC colonies. Transduction of the PTPN11 mutation into JMML iPSCs with the wild-type of both genes increased CD34+ cell production to a level comparable to that obtained with JMML iPSC colonies harbouring the two genetic mutations. Thus, PTPN11 mutation may be the most essential abnormality to confer an aberrant haematopoietic differentiation potential in this disorder.

Prevention of transfusion-transmitted cytomegalovirus infection using leukoreduced blood components in patients receiving seronegative umbilical cord blood transplantation.

BACKGROUND: Leukoreduced blood components have been widely implemented to prevent transfusion-transmitted cytomegalovirus (TT-CMV) in transplantation. Recent progress in leukoreduction technology has helped reduce the risk of TT-CMV in hematopoietic stem cell transplantation; however, its efficacy in umbilical cord blood transplantation (CBT) has not been systematically studied. STUDY DESIGN AND METHODS: We retrospectively analyzed the incidence of CMV infection in patients treated with CBT who received prestorage leukoreduced, CMV-unselected blood components between 2007 and 2017 in a single Japanese pediatric center. Patients were monitored for CMV antigenemia at least once weekly. RESULTS: In total, 71 patients treated with CBT were identified. Two patients were excluded because of unknown CMV serostatus or early death after CBT. Of the remaining 69 patients, 24 developed CMV antigenemia. Among them, 3 received granulocyte transfusions (3 of 3; 100%), 2 were infants with severe combined immunodeficiency who had been infected with CMV before CBT (2 of 2; 100%), and 19 were CMV-seropositive patients (19 of 23, 82.6%). Conversely, of the remaining 45 patients in whom CMV antigenemia did not develop, 41 were seronegative (0 of 41; 0%) and were transfused with a total of 925 leukoreduced, CMV-unselected blood components. Among the 41 patients, 9 (22%) received in vivo T-cell depletion with antithymocyte globulin. None of the patients in the seronegative group has subsequently shown evidence of CMV infection or developed CMV disease. CONCLUSION: Using prestorage leukoreduction, no cases of CMV infection were detected in seronegative CBT patients. Our findings showed the safety of leukoreduction in preventing TT-CMV in this patient group.

Analysis of clinical presentations of allergic transfusion reactions and febrile non-haemolytic transfusion reactions in paediatric patients.

BACKGROUND AND OBJECTIVES: Like adults, children can have allergic transfusion reactions (ATRs) and febrile non-haemolytic transfusion reactions (FNHTRs). But published information about the incidence of paediatric ATR and FNHTR is scarce. MATERIALS AND METHODS: This retrospective study was conducted from April 2002 to June 2018 on children who had ATRs and/or FNHTRs to platelet (PLT), red blood cell (RBC) or washed PLT/RBC concentrate transfusions. We analysed ATR/FNHTR clinical presentations, such as severity, time of occurrence and other features when they occurred. RESULTS: During the study, 2742 children received 23 444 bags of PLT and RBC concentrate (including washed products). ATRs occurred in 100 cases (3·6% of total patients), caused by 201 products (0·9% of total products). In contrast, 28 patients (1·0% of total patients) had 42 FNHTRs caused by 42 products (0·2% of total products). Upon analysis of cases with detailed clinical information, the median onset time for ATRs and FNHTRs was 2·0 h after the start of transfusion. Of the 40% of ATRs that necessitated the discontinuation of blood transfusions, 10% escalated to anaphylaxis. Compared with minor ATRs, anaphylaxis tended to develop quickly. Moreover, 96% of patients with FNHTRs had a fever less than 39°C. There were no associations between blood product types and numbers or occurrence patterns of these reactions. CONCLUSION: The occurrence of ATRs and FNHTRs in children was variable, although there are common features such as severity and time of occurrence.

Analysis of the clinical characteristics of pediatric patients who experience ifosfamide-induced encephalopathy.

BACKGROUND: Several kinds of pediatric hematological and/or malignant diseases are treated with chemotherapy regimens including ifosfamide (IFO). IFO-induced encephalopathy (IIE) is one of the serious side effects, but there is not enough evidence regarding the clinical features of IIE in children. PROCEDURE: We performed a retrospective study on pediatric patients treated with chemotherapy regimens, including IFO, at a single center. We recorded the clinical characteristics of all patients; we compared the clinical characteristics between patients who developed IIE and those who did not. RESULTS: In total, 88 patients received a chemotherapy regimen including IFO. IIE developed in seven patients (8.0%). The median age of patients at the time of IIE development was 4.3 (range 1.4-6.5) years in the younger population. Six of seven patients with IIE improved with supportive therapy only; however, one patient died due to heart failure. Overall survival was not different between the two groups. Multivariable analysis revealed that the co-administration of cisplatin (CDDP) or carboplatin (CBDCA) was a significant risk factor associated with IIE. Although there was no significant difference in laboratory data between the groups before chemotherapy, patients who developed IIE showed exacerbation in several laboratory tests, including those for renal and liver functions. CONCLUSIONS: Renal dysfunction caused by the combination of nephrotoxic agents (IFO and CDDP/CBDCA) seems to be important for the development of pediatric IIE. It was thought to be difficult to predict IIE onset based on laboratory data before the initiation of chemotherapy regimens; however, careful observation of laboratory data during IFO chemotherapy regimens may help predict IIE onset and facilitate early treatment.

Successful hematopoietic stem cell transplantation from an HLA-mismatched parent for engraftment failure after unrelated cord blood transplantation in patients with juvenile myelomonocytic leukemia: Report of two cases.

JMML is an aggressive hematopoietic malignancy of early childhood, and allogeneic HSCT is the only curative treatment for this disease. Umbilical cord blood is one of donor sources for HSCT in JMML patients who do not have an HLA-compatible relative, but engraftment failure remains a major problem. Here, we report two cases of JMML who were successfully rescued by HSCT from an HLA-mismatched parent after development of primary engraftment failure following unrelated CBT. Both patients had severe splenomegaly and underwent unrelated CBT from an HLA-mismatched donor. Immediately after diagnosis of engraftment failure, both patients underwent HSCT from their parent. For the second HSCT, we used RIC regimens consisting of FLU, CY, and a low dose of rabbit ATG with or without TBI and additionally administered ETP considering their persistent severe splenomegaly. Both patients achieved engraftment without severe treatment-related adverse effects. After engraftment of second HSCT, their splenomegaly was rapidly regressed, and both patients showed no sign of relapse for over 4 years. These observations demonstrate that HSCT from an HLA-mismatched parent could be a feasible salvage treatment for primary engraftment failure in JMML patients.

Ovarian function after allogeneic hematopoietic stem cell transplantation in children and young adults given 8-Gy total body irradiation-based reduced-toxicity myeloablative conditioning.

BACKGROUND: The spectrum of late sequelae after hematopoietic stem cell transplantation (HSCT) includes infertility, which is the most frequent complication. Some reports suggested that ovarian function may be better preserved in females undergoing HSCT with reduced-intensity conditioning (RIC) than with conventional myeloablative conditioning (MAC). However, the impact of HSCT after 8-Gy TBI-based reduced-toxicity MAC (RTMAC), whose efficacy is between those of conventional MAC and RIC, on ovarian function remains unclear. PROCEDURE: A single-center retrospective analysis of data derived from patient information for all the children who underwent transplantation at the Shinshu University Hospital was carried out. Patients who underwent 8-Gy total body irradiation (TBI)-based RTMAC before HSCT were analyzed. RESULTS: A total of 36% (five of 14) of the patients developed primary ovarian insufficiency (POI) during the observation period, but serum follicle-stimulating hormone levels reduced to normal range with spontaneous menstruation in two, implying the reversal of POI. Furthermore, only one (10%) of the 10 prepubertal patients (71%; 10/14) at the time of HSCT suffered from POI at the last observation, but all three post-pubertal patients developed POI (100%), and two (67%) continued to suffer from POI at the last observation. CONCLUSIONS: Taken together, 8-Gy TBI-based RTMAC before HSCT may decrease the possibility of POI compared with conventional MAC, especially in prepubertal patients. A longer follow-up will be required to ascertain whether a normal pregnancy and delivery can occur in such patients.

Panobinostat inhibits the proliferation of CD34+ CD38- cells under stimulation of hematopoietic growth factors on AGM-S3 cells in juvenile myelomonocytic leukemia.

BACKGROUND: Encouraging responses to histone deacetylase inhibitors have been reported for hematologic malignancies. Here, we report effects of panobinostat and 5-azacytidine on the proliferation of juvenile myelomonocytic leukemia (JMML) CD34+ cells. PROCEDURE: We previously reported that stimulation of JMML CD34+ cells with stem cell factor and thrombopoietin on irradiated murine AGM-S3 cells led to substantial expansion of JMML CD34+ cells that contained leukemic stem cells capable of transplantation into immunodeficient mice. Using this culture system, we evaluated effects of panobinostat and 5-azacytidine on the proliferation of JMML CD34+ cells. RESULTS: Panobinostat dose dependently reduced the numbers of day 7 CD34+ cells generated under stimulation of hematopoietic growth factors on AGM-S3 cells in all eight patients with JMML. These patients possessed various genetic and/or karyotypic abnormalities. CD34+ CD38- cells were substantially more sensitive to panobinostat at 10 and 20 nM than CD34+ CD38+ cells. Panobinostat, however, failed to influence the ability of AGM-S3 cells to stimulate JMML CD34+ cell production. In contrast to HL60 cells, apoptosis and cell cycle arrest in panobinostat-mediated inhibition were at low levels in JMML. The inhibitor also suppressed the factor-dependent proliferation of normal CD34+ cells on AGM-S3 cells. Meanwhile, no substantial inhibitory effects of 5-azacytidine on the growth of JMML CD34+ cells were observed. CONCLUSIONS: These results demonstrate that panobinostat directly suppresses the growth of JMML CD34+ cells, in particular CD34+ CD38- cells, regardless of the genetic abnormality type, suggesting that it is a useful antileukemic drug to target JMML stem cells at a pretransplant stage.