Ko Kudo

Impaired hematopoietic differentiation of RUNX1-mutated induced pluripotent stem cells derived from FPD/AML patients

Somatic mutation of RUNX1 is implicated in various hematological malignancies, including myelodysplastic syndrome and acute myeloid leukemia (AML), and previous studies using mouse models disclosed its critical roles in hematopoiesis. However, the role of RUNX1 in human hematopoiesis has never been tested in experimental settings. Familial platelet disorder (FPD)/AML is an autosomal dominant disorder caused by germline mutation of RUNX1, marked by thrombocytopenia and propensity to acute leukemia. To investigate the physiological function of RUNX1 in human hematopoiesis and pathophysiology of FPD/AML, we derived induced pluripotent stem cells (iPSCs) from three distinct FPD/AML pedigrees (FPD-iPSCs) and examined their defects in hematopoietic differentiation. By in vitro differentiation assays, FPD-iPSCs were clearly defective in the emergence of hematopoietic progenitors and differentiation of megakaryocytes, and overexpression of wild-type (WT)-RUNX1 reversed most of these phenotypes. We further demonstrated that overexpression of mutant-RUNX1 in WT-iPSCs did not recapitulate the phenotype of FPD-iPSCs, showing that the mutations were of loss-of-function type. Taken together, this study demonstrated that haploinsufficient RUNX1 allele imposed cell-intrinsic defects on hematopoietic differentiation in human experimental settings and revealed differential impacts of RUNX1 dosage on human and murine megakaryopoiesis. FPD-iPSCs will be a useful tool to investigate mutant RUNX1-mediated molecular processes in hematopoiesis and leukemogenesis.

Two novel variants of MOZ-CBP fusion transcripts in spontaneously remitted infant leukemia with t(1;16;8)(p13;p13;p11), a new variant of t(8;16)(p11;p13)

Translocation t(8;16)(p11;p13) involving the MOZ/MYST3 gene (8p11) and the CBP/CREBBP gene (16p13) is associated with the FAB M4/M5 subtype of acute myeloid leukemia (AML) and a poor prognosis. Five types of MOZ-CBP and three types of CBP-MOZ fusion transcripts have been identified in adult and

Voriconazole for both successful treatment of disseminated Trichosporon asahii infection and subsequent cord blood transplantation in an infant with acute myelogenous leukemia

Voriconazole for both successful treatment of disseminated Trichosporon asahii infection and subsequent cord blood transplantation in an infant with acute myelogenous leukemia

Gene alterations involving the CRLF2-JAK pathway and recurrent gene deletions in Down syndrome-associated acute lymphoblastic leukemia in Japan

In Western countries, gene alterations involving the CRLF2‐JAK signaling pathway are identified in approximately 50–60% of patients with Down syndrome‐associated acute lymphoblastic leukemia (DS‐ALL), and this pathway is considered a potential therapeutic target. The frequency of BTG1 deletions in DS‐ALL is controversial. IKZF1 deletions, found in 20–30% of DS‐ALL patients, are associated with a poor outcome and EBF1 deletions are very rare (∼2%). We analyzed 38 patients to determine the frequencies and clinical implications of CRLF2‐JAK pathway genetic alterations and recurrent gene deletions in Japanese DS‐ALL patients. We confirmed a high incidence of P2RY8‐CRLF2 (29%) and JAK2 mutations (16%), though the frequency of P2RY8‐CRLF2 was slightly lower than that in Western countries (∼50%). BTG1 deletions were common in our cohort (25%). IKZF1 deletions were detected in 25% of patients and associated with shorter overall survival (OS). EBF1 deletions were found at an unexpectedly high frequency (16%), and at a significantly higher level in P2RY8‐CRLF2‐positive patients than in P2RY8‐CRLF2‐negative patients (44% vs. 4%, P = 0.015). Deletions of CDKN2A/B and PAX5 were common in P2RY8‐CRLF2‐negative patients (48 and 39%, respectively) but not in P2RY8‐CRLF2‐positive patients (11% each). Associations between these genetic alterations and clinical characteristics were not observed except for inferior OS in patients with IKZF1 deletions. These results suggest that differences exist between the genetic profiles of DS‐ALL patients in Japan and in Western countries, and that P2RY8‐CRLF2 and EBF1 deletions may cooperate in leukemogenesis in a subset of Japanese DS‐ALL patients.

Guillain-Barré syndrome mimicking acute methotrexate-associated encephalopathy in an adolescent patient with lymphoblastic lymphoma.

We describe an adolescent case of Guillain-Barré syndrome (GBS) mimicking acute methotrexate-associated encephalopathy during chemotherapy for lymphoblastic lymphoma. Although initial presentations of hemiparesis and irritability were suggestive of acute encephalopathy, the diminished deep tendon reflexes and subsequent rapid progression to flaccid triparesis with bulbar palsy were consistent with GBS. After the initiation of intravenous immunoglobulin therapy her symptoms improved rapidly, and the diagnosis of GBS was confirmed by nerve conduction studies and cerebrospinal fluid examination in recovery phase. GBS should be considered in the differential diagnosis of acute methotrexate-associated encephalopathy, although GBS is a rare neurologic complication.

CD7-positive acute myelomonocytic leukemia with trisomy 21 as a sole acquired chromosomal abnormality in two adolescents

Trisomy 21 is one of the most common acquired chromosomal bnormalities in myeloid malignancies, but is rarely found as a sole nomaly. It has been reported that only 0.3% of adult patients with cute myeloblastic leukemia (AML) or myelodysplastic syndrome ave trisomy 21 as a sole acquired abnormality [1]. Although sevral reports indicate that this karyotypic abnormality is associated ith the French–American–British (FAB) AML subtypes M2, M4 and 5 [2,3] and with a poor prognosis [3,4], its clinical and prognosic implications have not been fully evaluated. Some investigators ave focused on the association between this chromosomal abnorality and CD7 expression, and 4 adult patients with CD7-positive ML have been reported so far [5–8]. Although one report includes adolescent AML cases with trisomy 21 as a sole acquired abnorality [3], there have been no reports on pediatric CD7-positive ML patients with this anomaly. Here, we report 2 unique adolesent cases of CD7-positive acute myelomonocytic leukemia with risomy 21 as a minor clone and as a sole acquired chromosomal bnormality.

Diplotype analysis of NUDT15 variants and 6-mercaptopurine sensitivity in pediatric lymphoid neoplasms

Thiopurines are key to the treatment of acute lymphoblastic leukemia (ALL) and lymphoblastic lymphoma (LBL) in children and adults, and 6-mercaptopurine (6-MP) is commonly used in consolidation and maintenance therapy [1–3]. Leukopenia is a dose-limiting toxicity of 6-MP partly explained by hypomorphic variants of TPMT [2–5] and clinical importance of TMPT genotyping is well established. Recently, NUDT15 was identified as a novel thiopurine regulator conferring 6-MP sensitivity most prominently in Asians and Hispanics [4–9]. Patients with bi-allelic NUDT15 variants are extremely sensitive to 6-MP, and only 5–10% of the standard dose is sufficient to maintain the target leukocyte count [4, 8]. Thus far, a total of seven variants in NUDT15 with low diphosphatase activity resulting in excess myelosuppression by 6-MP have been identified [4, 10, 11] and haplotypes with different combinations of variants are known to exist (Fig. 1a). Given the clinical importance of NUDT15 genotyping for individualized dosing of 6-MP [6, 12], the diplotype should be precisely determined, especially for those with heterozygous genotype at multiple variants. For example, a case with heterozygous c.36_37insGGAGTC and c.415C>T, which is the most frequent combination [4], should be determined as compound heterozygosity (*3/*6) or mono-allelic variants (*1/*2), because the two diplotypes have significantly different impacts on total NUDT15 activity [4]. However, a convenient method to determine the diplotype of NUDT15 has not been established, and as shown in the previous study, the diplotype is currently inferred using a public catalog of human variants [4]. Herein we demonstrated a method for identifying the diplotype using droplet digital PCR (ddPCR), and confirmed the results by wildtype specific PCR by a restriction enzyme. In total 138 Japanese children with ALL or LBL were enrolled (Supplementary Table 1). Patients were treated at the National Center for Child Health and Development, the University of Tokyo Hospital, the Hirosaki University Hospital or the Saitama Children’s Medical Center. For maintenance therapy, the 6-MP and MTX dosages were adjusted to maintain a leukocyte count of 1500–3000 /μl by at least monthly blood tests. In this study, a tolerable 6-MP and MTX dose was defined as the average of the doses per day (per week for MTX) administered during the first These authors contributed equally: Shinichi Tsujimoto, Tomoo Osumi.

Classic Hodgkin lymphoma with osseous involvement mimicking Langerhans cell histiocytosis in a child

Hodgkin lymphoma (HL) commonly presents superficial lymphadenopathy. In addition, HL cells can arise in various organs including the liver and spleen as an extranodal lymphoma. HL in bone is unusual at the initial diagnosis, although some cases show late-stage localization of lymphoma cells to bone. We report the rare case of a young patient with cranial bone classic HL, presumably originating from the skull without any involvement of lymph nodes. As the main clinical manifestation was only tumor mass in the skull without osteoscopic pain, the tentative diagnosis of Langerhans cell histiocytosis was histologically confirmed by an excisional biopsy. Before the final pathological diagnosis as classic HL, we noticed several small lesions in extranodal regions through systemic surveys, suggesting that the cranial lesion appeared antecedent to those lesions. This is a rare and instructive case of cranial bone HL for which a histological diagnosis has been meticulously made.

Two siblings with familial neuroblastoma with distinct clinical phenotypes harboring an ALK germline mutation

The authors report two siblings with familial neuroblastoma with a germline R1275Q mutation of the tyrosine kinase domain of ALK. Whole exome sequencing and copy number variation assay were performed to investigate genetic alterations in the two cases. No common somatic mutations or gene polymorphisms related to the tumorigenesis of neuroblastoma were detected. A distinct pattern involving both segmental chromosomal alteration and MYCN amplification was detected. The diversity of biological behavior of familial neuroblastoma harboring a germline ALK mutation may depend on conventional prognostic factors, such as segmental chromosomal alterations and MYCN amplification, rather than additional acquired mutations.