Clinical conditions and risk factors for inhibitor-development in patients with haemophilia: A decade-long prospective cohort study in Japan, J-HIS2 (Japan Hemophilia Inhibitor Study 2).

BACKGROUND: Inhibitor-development is a serious complication in patients with haemophilia (PwH). Previous studies reported that therapeutic and genetic factors could be associated with these alloantibodies. Relevant clinical features such as genetic-background and different treatment regimens in Japan remain unclear, however. AIMS: To analyse a nation-wide Japanese registry for PwH, and to examine risk factors for inhibitor-development. METHODS AND RESULTS: Newly diagnosed patients with haemophilia A (PwHA) or haemophilia B (PwHB) without inhibitors after 2007, and with treatment records traceable from 0 to 75 exposure days (ED), were enrolled in the Japan Hemophilia Inhibitor Study 2 (J-HIS2) initiated in 2008. Of 417 patients (340 PwHA, 77 PwHB) from 46 facilities, 83 (76 PwHA, 7 PwHB) were recorded with inhibitors by July 2020. Inhibitors were observed in 31.0% of severe PwHA, 8.0% moderate and 1.6% mild and in 17.1% of severe PwHB. The majority of inhibitors (89.7% in severe PwHA and 71.4% in severe PwHB) were detected on or before 25ED (median 12ED in PwHA and 19ED in PwHB). Genotyping in these severe patients identified an association between inhibitor-development and null variants of F8 (P < .01) or F9 (P < .05). A lower incidence of inhibitors was recorded in severe PwHA treated with prophylaxis than in those treated on-demand (P < .01). A past-history of intracranial-haemorrhage appeared to be associated with inhibitor-development, while FVIII-concentrates infusion and routine vaccination on the same day was not related to inhibitor-development. CONCLUSION: The J-HIS2 study has identified significant clinical variables associated with inhibitor-development in Japanese PwH, consistent with other global studies.

BCG vaccination in patients with severe combined immunodeficiency: complications, risks, and vaccination policies.

BACKGROUND: Severe combined immunodeficiency (SCID) is a syndrome characterized by profound T-cell deficiency. BCG vaccine is contraindicated in patients with SCID. Because most countries encourage BCG vaccination at birth, a high percentage of patients with SCID are vaccinated before their immune defect is detected. OBJECTIVES: We sought to describe the complications and risks associated with BCG vaccination in patients with SCID. METHODS: An extensive standardized questionnaire evaluating complications, therapeutics, and outcomes regarding BCG vaccination in patients given a diagnosis of SCID was widely distributed. Summary statistics and association analysis was performed. RESULTS: Data on 349 BCG-vaccinated patients with SCID from 28 centers in 17 countries were analyzed. Fifty-one percent of the patients had BCG-associated complications, 34% disseminated and 17% localized (a 33,000- and 400-fold increase, respectively, over the general population). Patients receiving early vaccination (≤1 month) showed an increased prevalence of complications (P = .006) and death caused by BCG-associated complications (P < .0001). The odds of experiencing complications among patients with T-cell numbers of 250/µL or less at diagnosis was 2.1 times higher (95% CI, 1.4-3.4 times higher; P = .001) than among those with T-cell numbers of greater than 250/µL. BCG-associated complications were reported in 2 of 78 patients who received antimycobacterial therapy while asymptomatic, and no deaths caused by BCG-associated complications occurred in this group. In contrast, 46 BCG-associated deaths were reported among 160 patients treated with antimycobacterial therapy for a symptomatic BCG infection (P < .0001). CONCLUSIONS: BCG vaccine has a very high rate of complications in patients with SCID, which increase morbidity and mortality rates. Until safer and more efficient antituberculosis vaccines become available, delay in BCG vaccination should be considered to protect highly vulnerable populations from preventable complications.

Immunosuppressive therapy with horse anti-thymocyte globulin and cyclosporine as treatment for fulminant aplastic anemia in children.

Patients with severe aplastic anemia (SAA) and an absolute neutrophil count (ANC) of 0 typically have fatal outcomes. We defined fulminant AA (FAA) as ANC = 0 for at least 2 weeks prior to and after immunosuppressive therapy (IST). We analyzed the outcomes of 35 children with FAA among 288 children who enrolled in a prospective study for AA (AA-97 study). AA was classified as FAA (n = 35), very SAA (vSAA; n = 129), or SAA (n = 124). All of the children received the IST with horse anti-thymocyte globulin (ATG) and cyclosporine (CsA). A significantly lower response rate at 6 months was seen in children with FAA when compared to those with vSAA or SAA (40.0, 63.6, and 63.7 %, respectively; p = 0.027). Of 20 nonresponder patients in the FAA group, 11 were rescued by alternative donor transplantation, and 5 patients showed a late response after 6 months. Consequently, no significant difference was noted in overall survival when comparing the FAA, vSAA, and SAA groups (88.5, 95.8, and 96.8 %). These findings indicate that IST with ATG and CsA is justified as a first-line treatment for children with FAA who lack a human leukocyte antigen-matched sibling donor.

Allogeneic Hematopoietic Cell Transplantation for Juvenile Myelomonocytic Leukemia with a Busulfan, Fludarabine, and Melphalan Regimen: JPLSG JMML-11.

Juvenile myelomonocytic leukemia (JMML), which is classified as a myelodysplastic/myeloproliferative neoplasm, is a rare hematologic malignancy of childhood. Most patients with JMML require allogeneic hematopoietic cell transplantation (HCT) as a curative therapy. A Japanese retrospective analysis demonstrated favorable outcomes for a busulfan (BU) + fludarabine (FLU) + melphalan (MEL) regimen, with an overall survival (OS) of 72% and an event-free survival (EFS) of 53%. To further validate the efficacy and safety of this regimen, the Japan Pediatric Leukemia/Lymphoma Study Group (JPLSG) conducted a nationwide prospective study, JMML-11. Between July 2011 and June 2017, 28 patients with newly diagnosed JMML were enrolled in JMML11. Low-dose chemotherapy for tumor control before HCT was recommended, and patients treated with AML-type chemotherapy and azacitidine were excluded. The conditioning regimen comprised i.v. BU, 16 doses administered every 6 h, with dose adjustment based on pharmacokinetic (PK) studies on days -11 to -8; FLU, 30 mg/m2/day or 1 mg/kg/day for patients <10 kg or age <1 year on days -7 to -4; and MEL, 90 mg/m2/day or 3 mg/kg/day for patients <10 kg or <1 year on days -3 to -2. The donor was selected by the physician in charge. A family donor was available for 7 patients (3 HLA-matched siblings, 3 HLA-1-antigen mismatched parents, and 1 haploidentical father). Overall, 21 patients received grafts from unrelated donors, including 8 HLA-matched donors and 13 HLA-mismatched donors. The graft source was related bone marrow (BM) for 7 patients, unrelated BM for 14 patients, and unrelated cord blood for 7 patients. Neutrophil engraftment was achieved in 21 of 28 patients (75%), with a median of 20.5 days (range, 11 to 39 days) after transplantation. The 3-year OS, 3-year EFS, 3-year relapse rate, and 3-year transplantation-related mortality were 63% (95% confidence interval [CI], 42% to 78%), 52% (95% CI, 32% to 69%), 18% (95% CI, 6% to 34%), and 21% (95% CI, 9% to 38%), respectively. WBC count before the conditioning regimen (≥7.0 × 109/L) was significantly associated with inferior EFS and OS. Body surface area ≥.5 m2, spleen size <4 cm before conditioning, and HLA-matched unrelated BM donors were significantly associated with better OS. Adverse effects related to the conditioning regimen included febrile neutropenia (86%), diarrhea (39%), hypoxemia (21%), and mucositis (18%). BU-associated toxicity, including sinusoidal obstruction syndrome (SOS) and thrombotic microangiopathy (TMA), occurred in 7 patients (25%; SOS, n = 6; TMA, n = 2). Retrospective analysis of PK data after the first BU dose in 23 patients, including 6 with SOS and 17 without SOS, did not show significant differences between groups. The JMML-11 study confirms the positive results of previous retrospective analyses. BU+FLU+MEL might become a standard conditioning regimen for patients with JMML.

Outcome of children with refractory anaemia with excess of blast (RAEB) and RAEB in transformation (RAEB-T) in the Japanese MDS99 study.

We report the outcome of 16 children with refractory anaemia with excess of blasts (RAEB; n = 4) and RAEB in transformation (RAEB-T; n = 12) following induction therapy with etoposide, cytarabine and mitoxantrone (ECM) prior to haematopoietic stem cell transplantation (HSCT). The median observation period was 77 months (range 5-123). Complete remission rate was 81% following induction; no toxic deaths occurred. Eight-year event-free survival and overall survival was 50% and 56%, respectively. None of the three patients with a complex karyotype survived, suggesting karyotype is a crucial prognostic factor for survival. This study indicates the safety and high remission rate of ECM and high survival rates after HSCT for paediatric RAEB and RAEB-T.

Impact of the mobilization regimen and the harvesting technique on the granulocyte yield in healthy donors for granulocyte transfusion therapy.

BACKGROUND: Granulocyte mobilization and harvesting, the two major phases of granulocyte collection, have not been standardized. STUDY DESIGN AND METHODS: The data on 123 granulocyte collections were retrospectively investigated for the effect of the mobilization regimen and the harvesting technique. After a single subcutaneous dose (600 µg) of granulocyte-colony-stimulating factor (G-CSF) with (n = 68) or without (n = 40) 8 mg of orally administered dexamethasone, 108 granulocyte donors underwent granulocyte collections. Moreover, 15 peripheral blood stem cell (PBSC) donors who had received 400 µg/m2 or 10 µg/kg G-CSF for 5 days underwent granulocyte collections on the day after the last PBSC collections (PBSC-GTX donors). Granulocyte harvesting was performed by leukapheresis with (n = 108) or without (n = 15) using high-molecular-weight hydroxyethyl starch (HES). RESULTS: Granulocyte donors who received mobilization with G-CSF plus dexamethasone produced significantly higher granulocyte yields than those who received G-CSF alone (7.2 × 10(10) ± 2.0 × 10(10) vs. 5.7 × 10(10) ± 1.7 × 10(10) , p = 0.006). PBSC-GTX donors produced a remarkably high granulocyte yield (9.7 × 10(10) ± 2.3 × 10(10) ). The use of HES was associated with better granulocyte collection efficiency (42 ± 7.8% vs. 10 ± 9.1%, p < 0.0001). CONCLUSION: G-CSF plus dexamethasone produces higher granulocyte yields than G-CSF alone. Granulocyte collection from PBSC donors appears to be a rational strategy, since it produces high granulocyte yields when the related patients are at a high risk for infection and reduces difficulties in finding granulocyte donors. HES should be used in apheresis procedures.

Mutations profile of polycythemia vera and essential thrombocythemia among Japanese children.

BACKGROUND: Acquired somatic mutations of JAK2 have been reported to play a pivotal role in the pathogenesis of BCR-ABL1-negative myeloproliferative neoplasm (MPN). However, the molecular characteristics of childhood MPN remain to be elucidated. PATIENT AND METHODS: We investigated a group of pediatric patients diagnosed either with essential thrombocythemia (ET; N = 9) or polycythemia vera (PV; N = 4) according to WHO criteria (median age = 10 years; range 1.5-15 years) in whom direct sequencing was performed for the existence of genetic alterations in JAK2, MPL, TET2, ASXL1, CBL, IDH1, and IDH2. More sensitive allele specific polymerase chain reaction was used for JAK2(V617F) genotyping. RESULTS: We found three patients harbor JAK2(V617F) mutation (2/9 ET and 1/4 PV). Bone marrow examination showed small and large megakaryocytes with dysplastic features in JAK2(V617F)-positive ET patients compared to those without JAK2(V617F). We identified a previously unrecognized missense mutation at codon 1230 in exon 12 of ASXL1 gene in ET and PV patients (1/9 ET and 1/4 PV). Otherwise, no genetic alterations could be detected in JAK2 exon 12, MPL, TET2, CBL, IDH1, and IDH2 in all ET and PV patients. CONCLUSION: Although JAK2 mutations in childhood ET and PV are not as frequent as reported in adult patients, JAK2 is the most frequently mutated gene in childhood MPN known so far. Owing to the presence of childhood MPN without any genetic alterations in JAK2, MPL, TET2, ASXL1, CBL, IDH1, and IDH2, new biological markers have to be found.

[Hepatic arterial infusion of liposomal amphotericin B for multiple fungal abscesses in the liver of a patient with chronic granulomatous disease].

A 26-year-old man with chronic granulomatous disease complicated by multiple liver abscess was admitted to our hospital for hepatic resection and allogeneic bone marrow transplantation (BMT) from an HLA-matched sibling. We diagnosed the patient with Aspergillus liver abscesses based on computed tomographic findings, elevated serum levels of beta-D-glucan, positive test for galactomannan antigen, and the findings of laboratory cultures. Since the liver abscess could not be treated by drainage and administration of antifungals, we resected the posterior segments of the liver, which contained the abscess (S1, S6). However, abscess recurred in the remaining part of the liver 1 month later. The patient received allogeneic BMT from an HLA-matched sibling. During BMT, we continuously administered liposomal amphotericin B (L-AMB) via the hepatic artery (25 mg/day) to treat the liver abscess. There were no adverse effects during hepatic arterial infusion of L-AMB, and the liver abscess disappeared after BMT. These results suggest that hepatic arterial infusion of L-AMB is effective in treating fungal abscess in the liver.

Identification of severe combined immunodeficiency by T-cell receptor excision circles quantification using neonatal guthrie cards.

OBJECTIVE: To assess the feasibility of T-cell receptor excision circles (TRECs) quantification for neonatal mass screening of severe combined immunodeficiency (SCID). STUDY DESIGN: Real-time PCR based quantification of TRECs for 471 healthy control patients and 18 patients with SCID with various genetic abnormalities (IL2RG, JAK3, ADA, LIG4, RAG1) were performed, including patients with maternal T-cell engraftment (n = 4) and leaky T cells (n = 3). RESULTS: TRECs were detectable in all normal neonatal Guthrie cards (n = 326) at the levels of 10(4) to 10(5) copies/microg DNA. In contrast, TRECs were extremely low in all neonatal Guthrie cards (n = 15) and peripheral blood (n = 14) from patients with SCID, including those with maternal T-cell engraftment or leaky T cells with hypomorphic RAG1 mutations or LIG4 deficiency. There were no false-positive or negative results in this study. CONCLUSION: TRECs quantification can be used as a neonatal mass screening for patients with SCID.

Treatment of children with refractory anemia: the Japanese Childhood MDS Study Group trial (MDS99).

BACKGROUND: Although hematopoietic stem cell transplantation (HSCT) is offered as a curative therapy for pediatric myelodysplastic syndrome (MDS), it may cause severe complications and mortality. Several reports have shown the efficacy of immunosuppressive therapy (IST) in adult patients with refractory anemia (RA), but its safety and efficacy remains to be fully elucidated in childhood RA. PROCEDURE: Eleven children diagnosed with RA and enrolled on a prospective multicenter trial conducted by the Japanese Childhood MDS Study Group were eligible for analysis. If patients showed transfusion dependent or suffered from infection due to neutropenia, they received IST consisting of antithymocyte globulin (ATG), cyclosporine (CyA), and methylprednisolone (mPSL). RESULTS: Eight children received IST, 2 received only supportive therapy, and one underwent HSCT without IST. Five (63%) of eight children who received IST showed hematological response. Of note, one patient showed the disappearance of monosomy 7 after IST. Responders were significantly younger than non-responders (29 months vs. 140 months; P = 0.03). No severe adverse events related to IST were reported in this study. Of 6 children with chromosomal abnormalities who received IST, four showed hematological response. The probability of failure-free and overall survival at 5 years was 63 +/- 17% and 90 +/- 9% respectively. CONCLUSION: IST is likely to be a safe and effective modality for childhood RA.

A conditioning regimen of busulfan, fludarabine, and melphalan for allogeneic stem cell transplantation in children with juvenile myelomonocytic leukemia.

A pilot study was undertaken using a myeloablative conditioning with fludarabine, busulfan, and melphalan to improve the outcome of HSCT in 10 children, aged six months to six yr, with JMML. All patients were conditioned with oral busulfan (560 mg/m(2)), fludarabine (120 mg/m(2)), and melphalan (180-210 mg/m(2)) prior to HSCT, and received stem cells from bone marrow in seven cases, and from cord blood in three cases. Engraftment was documented in eight patients, whereas graft failure occurred in two, one of whom had received HLA-mismatched cord blood and other had received bone marrow from HLA-mismatched mother. Three patients, including two in who graft failure had occurred, relapsed. Five patients developed acute GVHD and two developed chronic GVHD. Seven patients are alive and in remission 27-69 months after transplantation. Thus, our study showed that HSCT following conditioning with fludarabine, busulfan, and melphalan was well tolerated and appeared to be effective for JMML.

The effect of donor leukocyte infusion on refractory pure red blood cell aplasia after allogeneic stem cell transplantation in a patient with myelodysplastic syndrome developing from Kostmann syndrome.

We describe the clinical course of a patient who experienced refractory pure red cell aplasia (PRCA) after undergoing HLA-matched allogeneic peripheral blood stem cell transplantation (allo-PBSCT) for refractory anemia with an excess of blasts in transformation that had evolved from Kostmann syndrome. The treatment for patients with myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML) developing from Kostmann syndrome has not been standardized. We treated this patient with allo-PBSCT using a regimen combining high-dose cytosine arabinoside with granulocyte colony-stimulating factor, in addition to total body irradiation and cyclophosphamide without preceding intensive chemotherapy. The donor was ABO incompatible. Myeloid and platelet recoveries were achieved rapidly. Erythroid engraftment was not evident, however, and the patient was given a diagnosis of PRCA. Regimen-related toxicity and graft-versus-host disease (GVHD) were limited. The PRCA did not respond to various therapies, including the discontinuation of immunosuppressants for the induction of chronic GVHD, human recombinant erythropoietin, immunosuppressive treatment with steroids, cyclosporin A, and human anti-CD20 antibody (rituximab). The patient received transfusions 48 times until the resolution of his anemia by donor leukocyte infusion (DLI) at 25 months after PBSCT. He is now clinically well (performance status, 100%) with normal blood cell counts at 5 years after SCT. An in vitro study demonstrated that serum from the recipient blocked the differentiation of erythroid cells in the bone marrow. The results indicate that the conditioning regimen we describe seems safe and effective for those who have MDS/AML and that DLI might be a valuable approach for refractory PRCA after ABO-incompatible SCT.

Occurrence of colon tumors in a 16-year-old Japanese boy after hematopoietic stem cell transplantation for Diamond Blackfan anemia at age of 4: a case report.

Diamond Blackfan anemia (DBA) is a congenital pure red cell aplasia mainly caused by a mutation in ribosomal protein genes. One of the proposed mechanisms for red cell aplasia in DBA is apoptosis caused by constitutive activation of tumor suppressor TP53 protein following defective ribosome biogenesis. Because of this close relationship between ribosome biogenesis and TP53 activation, patients with DBA are considered to be cancer-prone. The association between bone marrow failure and tumor susceptibility in DBA appears paradoxical. Also, the detailed information is lacking on malignancy occurring in patients with DBA. Here, we report a case of a 16-year-old Japanese boy suffering from multiple colon tumors during the follow-up after hematopoietic stem cell transplantation for DBA at the age of 4. Well differentiated tubular adenocarcinoma was detected at the rectum 12 years after the transplantation, followed by multiple tubular adenomas of low to high grade throughout the colon. Endoscopic submucosal dissection was performed for these tumors and the lesions were completely resected. These tumors did not show diffuse and strong TP53 positivity by immunohistochemistry, suggesting that TP53 mutation was not involved in the tumorigenesis as observed in conventional colorectal cancers. Microsatellite instability test and immunohistochemical examination of ß-catenin and MLH1 proteins of these tumors showed that WNT signaling or microsatellite instability was less likely to be involved in the present tumors as observed in conventional left-sided or right-sided colon cancers, respectively. To our knowledge, this is the first case report of colon tumors associated with DBA.

Transplantation for juvenile myelomonocytic leukemia: a retrospective study of 30 children treated with a regimen of busulfan, fludarabine, and melphalan.

We report the outcomes of 30 patients with juvenile myelomonocytic leukemia (JMML) who received unmanipulated hematopoietic stem cell transplantation (HSCT) with oral or intravenous busulfan, fludarabine, and melphalan between 2001 and 2011. Mutations in PTPN11 were detected in 15 patients. Six patients received human leukocyte antigen (HLA)-matched HSCT from related donors, and 24 patients received HSCT from alternative donors, including 13 HLA-mismatched donors. Primary engraftment failed in five patients, all of whom had received allografts from HLA-mismatched donors. HLA-mismatched HSCT resulted in poorer event-free survival than HLA-matched HSCT (28.8 vs. 70.6 %). Three patients died of transplantation-related causes, and eight patients experienced hematological relapse (including five patients who died due to disease progression). Eight patients received a second HSCT, and four of these patients have survived. The 5-year estimated overall survival for all patients was 72.4: 88.9 % for the patients without a mutation in PTPN11 (n = 10) and 58.3 % for the patients with a mutation in PTPN11 (n = 15) (P = 0.092). The conditioning regimen reported in the present study achieved hematological and clinical remission in >50 % of patients with JMML who received HSCT from alternative donors, and may also be effective for JMML patients with PTPN11 mutation.

Third International Symposium on Myelodysplastic Syndromes in Childhood.

This article summarizes presentations from the Third International Symposium on Myelodysplastic Syndromes in Childhood, April 27-29, 2003, in Stresa, Italy. Topics included epidemiology, pathology, cytogenetics, molecular biology, pathophysiology, and treatment. Dr. Susanna Fenu was the Meeting Chair.

Clinicopathological characteristics of erythroblast-rich RAEB and AML M6a in children.

The distinction between RAEB, RAEB-T and AML M6a is difficult when erythroblasts in the bone marrow (BM) exceed 50%. We analyzed 19 children (2 RAEB, 13 RAEB-T and 4 AML M6a) enrolled in a prospective pathological central review in Japan and divided them into two groups according to the myeloblasts percentage among non-erythroid cells in BM: group A (n = 8), 5-19% myeloblasts; group B (n = 11), 20% or more myeloblasts. Their characteristics were very similar except for the number of myeloblasts. The median WBC was in the range of 1.0-5.0 x 10(9) L(-1), the median Hb was around 7.5 g/dL, the median MCV was greater than 90 fL and both group had Auer rods at 60-65%. Severe multilineage dysplasia was observed in most of the patients in two groups. Six with group A and seven with group B treated with AML type chemotherapy achieved complete remission. Five with group A and seven with group B undergoing SCT are alive at a median of 3 years after diagnosis. Erythroblast-rich RAEB and AML M6a in children have similar characteristics and may belong to a single disease entity.

Spontaneous improvement of hematologic abnormalities in patients having juvenile myelomonocytic leukemia with specific RAS mutations.

Of 11 children with juvenile myelomonocytic leukemia (JMML) carrying RAS mutations (8 with NRAS mutations, 3 with KRAS2 mutations), 5 had a profound elevation in either or both the white blood cells and spleen size at diagnosis. Three patients had no or modest hepatosplenomegaly and mild leukocytosis at presentation but subsequently showed a marked increase in spleen size with or without hematologic exacerbation, for which nonintensive chemotherapy was initiated. The other three patients with NRAS or KRAS2 glycine to serine substitution received no chemotherapy, but hematologic improvement has been observed during a 2- to 4-year follow up. In the third group, all hematopoietic cell lineages analyzed had the RAS mutations at the time of hematologic improvement, whereas DNA obtained from the nails had the wild type. Additionally, numbers of circulating granulocyte-macrophage progenitors were significantly reduced during the clinical course. Thus, some patients with JMML with specific RAS mutations may have spontaneously improving disease.

RAS-blocking bisphosphonate zoledronic acid inhibits the abnormal proliferation and differentiation of juvenile myelomonocytic leukemia cells in vitro.

Juvenile myelomonocytic leukemia (JMML) is a clonal myeloproliferative/myelodysplastic disorder of early childhood with a poor prognosis. JMML cells are characterized by hypersensitivity to granulocyte-macrophage colony-stimulating factor (GM-CSF) caused by a continuously activated GM-CSF receptor-retrovirus-associated sequence (RAS) signal transduction pathway through various molecular mechanisms, resulting in spontaneous GM colony formation in vitro. Bisphosphonate zoledronic acid (ZOL), a RAS-blocking compound, suppressed colony formation from bone marrow (BM) cells of 8 patients with JMML and 5 healthy control subjects without and with GM-CSF (10 ng/mL), respectively, in a dose-dependent manner in clonal culture. At 10 microM ZOL, however, spontaneous GM colony formation from JMML BM cells decreased to 3%, but the formation of G colonies containing granulocytes, but no macrophages, was enhanced, whereas 40% of GM colonies were retained and G colony formation was not affected in culture of normal BM cells with GM-CSF. In suspension culture, cytochemical and flow cytometric analyses showed that 10 microM ZOL also inhibited spontaneous proliferation and differentiation along monocyte/macrophage lineage of JMML BM cells but not the development of normal BM cells by GM-CSF. The inhibitory effect of ZOL on JMML cells was confirmed at a single-clone level and observed even at 3 microM. The current result offers a novel approach to therapy in JMML.

Methylation status of the p15 and p16 genes in paediatric myelodysplastic syndrome and juvenile myelomonocytic leukaemia.

Aberrant DNA methylation is frequently observed in adults with myelodysplastic syndrome (MDS), and is recognized as a critical event in the disease's pathogenesis and progression. This is the first report to investigate the methylation status of p15 and p16, cell cycle regulatory genes, in children with MDS (n = 9) and juvenile myelomonocytic leukaemia (JMML; n = 18) by using a methylation-specific polymerase chain reaction. The frequency of p15 hypermethylation in paediatric MDS was 78% (7/9), which was comparable to that in adult MDS. In contrast, p15 hypermethylation in JMML was a rare event (17%; 3/18). In JMML, clinical and laboratory characteristics including PTPN11 mutations and aberrant colony formation were not different between the three patients with hypermethylated p15 and the others. Aberrant methylation of p16 was not detected in children with either MDS or JMML. Since p15 and p16 genes were unmethylated in two children with JMML, in whom the disease had progressed with an increased number of blasts, a condition referred to as blastic crisis, we infer that the aberrant methylation of these genes is not responsible for the progression of JMML. The results suggest that demethylating agents may be effective in most children with MDS and a few patients with JMML.