Atsushi Ogawa

TALEN-mediated single-base-pair editing identification of an intergenic mutation upstream of BUB1B as causative of PCS (MVA) syndrome

Significance A single nucleotide substitution in an intergenic region upstream of BUB1B (encoding BUBR1) was identified as a candidate mutation for premature chromatid separation with mosaic variegated aneuploidy [PCS (MVA) syndrome], a cancer-prone genetic disorder. To prove that this is the causal mutation, we designed a unique genome editing strategy, transcription activator-like effector nuclease–mediated two-step single-base-pair editing, to biallelically introduce this substitution into cultured human cells. The cell clones showed chromosomal instability in the form of PCS and MVA, which are cellular hallmarks of the syndrome, suggesting that this is indeed the underlying mutation. This single-base-pair editing technique will be useful for investigations of noncoding variants of unknown functional relevance. Cancer-prone syndrome of premature chromatid separation with mosaic variegated aneuploidy [PCS (MVA) syndrome] is a rare autosomal recessive disorder characterized by constitutional aneuploidy and a high risk of childhood cancer. We previously reported monoallelic mutations in the BUB1B gene (encoding BUBR1) in seven Japanese families with the syndrome. No second mutation was found in the opposite allele of any of the families studied, although a conserved BUB1B haplotype and a decreased transcript were identified. To clarify the molecular pathology of the second allele, we extended our mutational search to a candidate region surrounding BUB1B. A unique single nucleotide substitution, G > A at ss802470619, was identified in an intergenic region 44 kb upstream of a BUB1B transcription start site, which cosegregated with the disorder. To examine whether this is the causal mutation, we designed a transcription activator-like effector nuclease–mediated two-step single-base pair editing strategy and biallelically introduced this substitution into cultured human cells. The cell clones showed reduced BUB1B transcripts, increased PCS frequency, and MVA, which are the hallmarks of the syndrome. We also encountered a case of a Japanese infant with PCS (MVA) syndrome carrying a homozygous single nucleotide substitution at ss802470619. These results suggested that the nucleotide substitution identified was the causal mutation of PCS (MVA) syndrome.

Second allogeneic hematopoietic SCT for relapsed ALL in children

A second SCT is generally accepted as the only potentially curative approach for ALL patients that relapse after SCT, but the role of second SCT for pediatric ALL is not fully understood. We performed a retrospective analysis of 171 pediatric patients who received a second allo-SCT for relapsed ALL after allo-SCT. OS at 2 years was 29.4±3.7%, the cumulative incidence of relapse was 44.1±4.0% and non-relapse mortality was 18.8±3.5%. Relapse occurred faster after the second SCT than after the first SCT (117 days vs 164 days, P=0.04). Younger age (9 years or less), late relapse (180 days or more after first SCT), CR at the second SCT, and myeloablative conditioning were found to be related to longer survival. Neither acute GVHD nor the type of donor influenced the outcome of second SCT. Multivariate analysis showed that younger age and late relapse were associated with better outcomes. Our analysis suggests that second SCT for relapsed pediatric ALL is an appropriate treatment option for patients that have achieved CR, which is associated with late relapse after the first SCT.

Continuous and high-dose cytarabine combined chemotherapy in children with down syndrome and acute myeloid leukemia: Report from the Japanese children's cancer and leukemia study group (JCCLSG) AML 9805 down study.

The aim of the JCCLSG AML 9805 Down study was to evaluate the effect of continuous and high‐dose cytarabine combined chemotherapy on the survival outcome of acute myeloid leukemia (AML) with Down syndrome (DS).

Quantitative assessment of PTPN11 or RAS mutations at the neonatal period and during the clinical course in patients with juvenile myelomonocytic leukaemia.

To evaluate minimal residual disease (MRD) after chemotherapy and haematopoietic stem cell transplantation in juvenile myelomonocytic leukaemia (JMML), a locked nucleic acid‐allele specific quantitative polymerase chain reaction (LNA‐AS‐qPCR) was developed for 13 patients (four types of PTPN11 mutation and four types of RAS mutation). The post‐transplant MRD detected by LNA‐AS‐qPCR analysis was well correlated with chimerism assessed by short tandem repeat PCR analysis. Non‐intensive chemotherapy exerted no substantial reduction of the tumour burden in three patients. There was no significant difference in the quantity of RAS mutant DNA after spontaneous haematological improvement in 4 patients with NRAS or KRAS 34G > A during a 2‐ to 5‐year follow‐up. PTPN11, NRAS, or KRAS mutant DNA was detected from Guthrie card dried blood in five of seven patients (who were aged <2 years at diagnosis) at a level of 1·0–6·5 × 10−1 of the values at diagnosis. Accordingly, these five patients might have already reached a subclinical status at birth. Considering the negative correlation between mutant DNA level in neonatal blood spots and age at diagnosis, JMML patients with a larger tumour burden at birth appeared to show earlier onset.

Features and outcome of neonatal leukemia in Japan: Experience of the Japan Infant Leukemia Study Group

Neonatal leukemia characterized by early stem cell origin and extramedullary infiltration in the first 4 weeks of life is rare. We analyzed the features and outcome of neonatal leukemia in Japan to establish an appropriate treatment strategy for this rare disorder.

Comparison of Intravenous with Oral Busulfan in Allogeneic Hematopoietic Stem Cell Transplantation with Myeloablative Conditioning Regimens for Pediatric Acute Leukemia

Recent reports revealed that intravenous (iv) busulfan (BU) may not only reduce early nonrelapse mortality (NRM) but also improve overall survival (OS) probability in adults. Therefore, we retrospectively compared outcomes for 460 children with acute leukemia who underwent hematopoietic stem cell transplantation with either iv-BU (n = 198) or oral busulfan (oral-BU) (n = 262) myeloablative conditioning. OS at 3 years was 53.4% ± 3.7% with iv-BU and 55.1% ± 3.1% with oral-BU; the difference was not statistically significant (P = .77). OS at 3 years in 241 acute lymphoblastic leukemia and 219 acute myeloid leukemia patients was 56.4% ± 5.5% with iv-BU and 54.6% ± 4.1 with oral-BU (P = .51) and 51.0% ± 5.0% with iv-BU and 55.8% ± 4.8% with oral-BU (P = .83), respectively. Cumulative incidence of relapse at 3 years with iv-BU was similar to that with oral-BU (39.0% ± 3.6% and 36.4% ± 3.1%, respectively; P = .67). Cumulative incidence of NRM at 3 years was 16.6% ± 2.7% with iv-BU and 18.3% ± 2.5% with oral-BU (P = .51). Furthermore, multivariate analysis showed no significant survival advantage with iv-BU. In conclusion, iv-BU failed to show a significant survival advantage in children with acute leukemia.

Chaotic Dynamics During Slow Relaxation Process in Magnon Systems

Experimental evidence of chaotic dynamics during a slow relaxation process with very low frequency magnetization auto-oscillations in magnon systems is presented. A ferromagnetic resonance experiment using a sphere of pure yttrium iron garnet (YIG) at the X-band pumping frequency within the coincidence regime reveals a slow relaxation process with a long tail after a stepwise drop in external pumping power. The relaxation process is found to follow a power-law with time as a transient process involving a transition of local dynamics from a quasi-periodic state to a chaotic state as the collapse of torus.

Reduced intensity conditioning in allogeneic stem cell transplantation for AML with Down syndrome

Allogeneic hematopoietic stem cell transplantation (HSCT) has not been widely used in patients with acute myeloid leukemia (AML) and Down syndrome (DS) due to fear of transplantation‐related toxicity. A retrospective analysis of the outcome of allogeneic HSCT was conducted in 15 patients with AML and DS. The five patients transplanted with the reduced intensity conditioning (4 in complete remission (CR) and 1 in non‐CR) had a significantly better survival rate than 10 patients transplanted with a conventional conditioning (4 in CR and 6 in non‐CR) (3‐year EFS (95% confidence interval): 80.0% (20.4–96.9%) vs. 10.0% (0.6%–35.8%), P = 0.039). Pediatr Blood Cancer 2014;61:925–927.

PBSCT is associated with poorer survival and increased chronic GvHD than BMT in Japanese paediatric patients with acute leukaemia and an HLA-matched sibling donor.

Peripheral blood stem cells (PBSC) may be used as an alternative to bone marrow (BM) for allogeneic transplantation. Since peripheral blood stem cell bank from unrelated volunteer donor has been started in Japan, use of PBSC allografts may be increased. Therefore we surveyed the outcomes of Japanese leukemia children after PBSC and BM transplantation.

Comparison of continuous and twice‐daily infusions of cyclosporine A for graft‐versus‐host‐disease prophylaxis in pediatric hematopoietic stem cell transplantation

Cyclosporine A (CsA) is used widely for graft‐versus‐host disease (GVHD) prophylaxis in hematopoietic stem cell transplantation (HSCT); however, the optimal schedule of its administration has not been established. Although comparative studies of adult patients undergoing HSCT have demonstrated enhanced efficacy and safety of twice‐daily infusion (TD) compared with continuous infusion (CIF) of CsA, to our knowledge, similar studies have not yet been performed in pediatric groups.