Takuro Nishikawa

Outcomes of immunological interventions for mixed chimerism following allogeneic stem cell transplantation in children with juvenile myelomonocytic leukemia.

For children with juvenile myelomonocytic leukemia (JMML) who undergo stem cell transplantation (SCT), the role of immunological interventions including withdrawal of immunosuppressive therapy (IST) and donor lymphocyte infusion (DLI) for treatment of disease recurrence remains uncertain.

Mechanisms of Fatal Cardiotoxicity following High-Dose Cyclophosphamide Therapy and a Method for Its Prevention.

Observed only after administration of high doses, cardiotoxicity is the dose-limiting effect of cyclophosphamide (CY). We investigated the poorly understood cardiotoxic mechanisms of high-dose CY. A rat cardiac myocardial cell line, H9c2, was exposed to CY metabolized by S9 fraction of rat liver homogenate mixed with co-factors (CYS9). Cytotoxicity was then evaluated by 3-(4,5-dimethyl-2-thiazolyl)¬2,5-diphenyl¬2H-tetrazolium bromide (MTT) assay, lactate dehydrogenase release, production of reactive oxygen species (ROS), and incidence of apoptosis. We also investigated how the myocardial cellular effects of CYS9 were modified by acrolein scavenger N-acetylcysteine (NAC), antioxidant isorhamnetin (ISO), and CYP inhibitor β-ionone (BIO). Quantifying CY and CY metabolites by means of liquid chromatography coupled with electrospray tandem mass spectrometry, we assayed culture supernatants of CYS9 with and without candidate cardioprotectant agents. Assay results for MTT showed that treatment with CY (125–500 μM) did not induce cytotoxicity. CYS9, however, exhibited myocardial cytotoxicity when CY concentration was 250 μM or more. After 250 μM of CY was metabolized in S9 mix for 2 h, the concentration of CY was 73.6 ± 8.0 μM, 4-hydroxy-cyclophosphamide (HCY) 17.6 ± 4.3, o-carboxyethyl-phosphoramide (CEPM) 26.6 ± 5.3 μM, and acrolein 26.7 ± 2.5 μM. Inhibition of CYS9-induced cytotoxicity occurred with NAC, ISO, and BIO. When treated with ISO or BIO, metabolism of CY was significantly inhibited. Pre-treatment with NAC, however, did not inhibit the metabolism of CY: compared to control samples, we observed no difference in HCY, a significant increase of CEPM, and a significant decrease of acrolein. Furthermore, NAC pre-treatment did not affect intracellular amounts of ROS produced by CYS9. Since acrolein seems to be heavily implicated in the onset of cardiotoxicity, any competitive metabolic processing of CY that reduces its transformation to acrolein is likely to be an important mechanism for preventing cardiotoxicity.

Effect of myeloperoxidase inhibition on gene expression profiles in HL-60 cells exposed to 1,2,4,-benzenetriol.

While it is known that benzene induces myeloid leukemia in humans, the mechanism has yet to be clarified. Previously, we suggested that myeloperoxidase (MPO) was the key enzyme because it promotes generation of powerful oxidant hypochlorous acid (HOCl) which, reacting with DNA, causes leukemogenesis. In this study, using a whole-human-genome oligonucleotide microarray to clarify the relationships between myelotoxicity of benzene and MPO, we analyzed the genome-wide expression profiles of HL-60 human promyelocytic cell lines exposed to 1,2,4-benzenetriol (BT) with or without MPO inhibition. The microarray analysis revealed that short (1 h) and longer (4 h) exposure to BT changed the expression in HL-60 cells of 1,213 or 1,214 genes associated with transcription, RNA metabolic processes, immune response, apoptosis, cell death, and biosynthetic processes (|Z-score|> 2.0), and that these changes were dramatically lessened by MPO-specific inhibition. The presence of functionally important genes and, specifically, genes related to apoptosis, carcinogenesis, regulation of transcription, immune responses, oxidative stress, and cell-cycle regulation were further validated by real-time RT-PCR. Gene expression profiles along with Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway annotation analysis suggest that BT-induced DNA halogenation by MPO is a primary reaction in the leukemogenesis associated with benzene.

The second therapeutic trial for children with hematological malignancies who relapsed after their first allogeneic SCT: long-term outcomes.

Nishikawa T, Inagaki J, Nagatoshi Y, Fukano R, Nakashima K, Ito N, Sawa D, Kawano Y, Okamura J. The second therapeutic trial for children with hematological malignancies who relapsed after their first allogeneic SCT: Long‐term outcomes.

Bone marrow transplant for a girl with bone marrow failure and cerebral palsy.

Bone marrow transplantation (BMT) has been used with increasing frequency to treat congenital bone marrow failure syndrome (CBMFs) successfully. Decision to perform BMT, however, is difficult in the case of comorbidity because of regimen‐related toxicities. We describe here a child with CBMFs, severe cerebral palsy (CP) at Gross Motor Function Classification System level V and mental retardation (MR) who was transfusion dependent despite various medications. She underwent BMT from an HLA‐1 locus‐mismatched unrelated donor. Although engraftment was successful, no neurological improvement was seen 5 years after BMT. While CBMFs patients who have CP and MR could undergo transplantation safely, they may not benefit neurologically from BMT.

Ramsay Hunt syndrome in a girl with acute lymphoblastic leukemia during maintenance therapy.

A 5-year-old girl with precursor B-cell acute lymphoblastic leukemia developed peripheral-type right facial palsy and very faint erythema on her right pinna during maintenance therapy. Acyclovir was started for possible zoster infection. The following day, vesicles appeared and a diagnosis of Ramsay Hunt syndrome was made. Prednisolone was started on day 5 after onset. Her facial palsy recovered within 6 months. Ramsay Hunt syndrome is a rare cause of facial palsy in patients with acute lymphoblastic leukemia, and this is the first case report. Preemptive therapy with acyclovir before the development of vesicles should help the patient recover from facial palsy.

Successful treatment with plasma exchange for disseminated cidofovir-resistant adenovirus disease in a pediatric SCT recipient

Successful treatment with plasma exchange for disseminated cidofovir-resistant adenovirus disease in a pediatric SCT recipient