Kosuke Chayama

Toyonaka Municipal Hospital, Toyonaka, Ōsaka, Japan

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Publications (6)6.99 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Clonal cytogenetic abnormalities (CCA) in Philadelphia chromosome (Ph)-negative cells have been reported in a small population of adult chronic myelogenous leukemia (CML) patients during the clinical course, but CCA in pediatric CML patients are rarely reported. We herein report the case of an 8-year-old boy from the onset of CML. Although he had relapse after unrelated bone marrow transplantation when 9 years old, he has since been in complete molecular response on imatinib mesylate treatment. Surprisingly, various CCA have been observed in this patient, including several reciprocal chromosomal translocations in Ph-negative cells for >12 years. Although dysplasia in the bone marrow cells was identified, no overt transformation to myelodysplastic syndrome or acute myeloid leukemia has been observed. The cause of the CCA remains unknown in this patient, and careful observation is required.
    Pediatrics International 11/2015; DOI:10.1111/ped.12739 · 0.73 Impact Factor
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    ABSTRACT: The tyrosine kinase inhibitor (TKI) imatinib mesylate (IM) revolutionized the treatment of Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph-ALL), which had showed poor prognosis before the dawn of IM treatment. However, if Ph-ALL patients showed IM resistance due to ABL kinase mutation, second-generation TKI, dasatinib or nilotinib, was recommended. We treated 4 pediatric Ph-ALL patients with both IM and bone marrow transplantation (BMT); however, 3 relapsed. We retrospectively examined the existence of ABL kinase mutation using PCR and direct sequencing methods, but there was no such mutation in all 4 diagnostic samples. Interestingly, two relapsed samples from patients who were not treated with IM before relapse did not show ABL kinase mutation and IM was still effective even after relapse. On the other hand, one patient who showed resistance to 3 TKI acquired dual ABL kinase mutations, F359C at the IM-resistant phase and F317I at the dasatinib-resistant phase, simultaneously. In summary, Ph-ALL patients relapsed with or without ABL kinase mutation. Furthermore, ABL kinase mutation was only found after IM treatment, so an IM-resistant clone might have been selected during the IM treatment and intensive chemotherapy. The appropriate combination of TKI and BMT must be discussed to cure Ph-ALL patients.
    International journal of hematology 03/2014; 99(5). DOI:10.1007/s12185-014-1565-3 · 1.92 Impact Factor
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    ABSTRACT: Activation of the phosphoinositide 3-kinase (PI3K)/Akt pathway, a pro-survival pathway, plays important roles in tumor cell growth. However, the role of Akt in the pathogenesis of pediatric B-precursor acute lymphoblastic leukemia (B-pre ALL) remains to be clarified. This study was undertaken to explore the clinical relevance and molecular mechanisms underlying the activation of Akt (i.e., phosphorylated Akt, P-Akt) in pediatric B-pre ALL. We evaluated the activation status of Akt in bone marrow samples from 21 children with newly diagnosed B-pre ALL and correlated the expression level of P-Akt with clinicopathologic and prognostic features. Additionally, we transfected the myristoylated Akt cDNA into the B-pre ALL cell line, Nalm-6, and examined the effect, in vitro, of Akt activation on the response to antitumor drugs. P-Akt expression in B-pre ALL blast cells at diagnosis was associated significantly with poor response to induction chemotherapy including prednisolone, dexamethasone, vincristine, and adriamycin in B-pre ALL patients. Both overall survival and relapse-free survival in patients with P-Akt expression were reduced significantly more than in patients without P-Akt expression. Activation of Akt reduced the extent of apoptosis induced by the antitumor drugs in Nalm-6 listed above. Activation of Akt did not induce expression of P-glycoprotein, a drug transporter that is capable of conferring multidrug resistance. These results support the contention that Akt activation is a mechanism of chemotherapeutic resistance in B-pre ALL and suggest that Akt can be a therapeutic target for the treatment of relapsed or refractory pediatric B-pre ALL.
    Pediatric Blood & Cancer 07/2012; 59(1):83-9. DOI:10.1002/pbc.24034 · 2.39 Impact Factor
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    ABSTRACT: Oral mucositis is a major toxicity in the high-dose methotrexate (HD-MTX) treatment for children with acute lymphoblastic leukemia (ALL). The first aim of this study was to evaluate the relationship between the MTX serum concentration and occurrence of oral mucositis in pediatric ALL patients. The second aim was to clarify the relationship between MTX exposure and epidermal keratinocyte cell injury using an in vitro study. 49 patients were treated according to the Japan Association of Childhood Leukemia Study (JACLS) ALL-HR02 protocol. This protocol involves HD-MTX treatment (3 g/m2 for 24-h i.v. infusion). The MTX serum concentrations were measured by a fluorescence polarization immunoassay. The relationship between oral mucositis and MTX serum concentrations 48 and 72 h after administration was determined. The cell toxicity of MTX for human epidermal keratinocytes was analyzed by using a cell viability assay (WST-1 assay). In addition, pharmacokinetic evaluation for clearance, AUC extrapolated from 48 h to infinity (AUC48h-inf) and elimination half-life (t1/2b) were done using the 1-compartmental models. Oral mucositis occurred in 24 patients (49.0%), in whom 20 patients (83.3% in oral mucositis group) showed WHO severity Grade 1 or 2. Only 4 patients (16.7% in oral mucositis group) showed Grade 3 severity. 22 patients (44.9%) had oral mucositis in the group with a concentration under 10-6 M 48 h after MTX administration. There was no significant deference among the cell viabilities in the concentrations of 10-6 M, 10-5 M and 10-4 M 48 h after the MTX exposure. However, the cell viability obtained 24 h after the MTX exposure was significantly different from the respective cell viability 48, 72 and 96 h after the MTX exposure. In the group with oral mucositis, the clearance decreased significantly (p = 0.042), and the t1/2b (p = 0.025) and AUC48h- yen (p = 0.025) increased significantly compared with the non-symptom group. It seems that there is no significant relationship between the serum MTX concentration and oral mucositis. This in vitro study has demonstrated that the cell injury was related to the duration of MTX exposure rather than a high MTX concentration.
    International journal of clinical pharmacology and therapeutics 12/2008; 46(11):584-90. DOI:10.5414/CPP46584 · 1.22 Impact Factor

  • Pediatrics International 07/2008; 50(3):388-91. DOI:10.1111/j.1442-200X.2008.02599.x · 0.73 Impact Factor
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    ABSTRACT: The prostate cancer HERV-K gag-related NGO-Pr-54 antigen was identified by SEREX analysis using autologous patient serum. NGO-Pr-54 mRNA was observed to be faintly expressed in normal prostate and strongly expressed in a variety of cancers, including ovarian cancer (5/8), prostate cancer (6/9), and leukemia (5/14). A phage plaque assay showed that a strong reaction was constantly observed with clone ZH042 in which the 5' end of NGO-Pr-54 is deleted, suggesting that it contained the sequence coding for the protein product. A TI-35 mAb was produced using a recombinant protein (438 aa) deduced from the sequence of ZH042. Transfection of clone ZH042 into 293T cells resulted in the production of an approximately 50-kDa molecule visualized by Western blotting. Natural production of the molecule was confirmed in a SK-MEL-23 melanoma cell line. An indirect immunofluorescence assay showed that NGO-Pr-54 protein was expressed on the cell surface as well as in the cytoplasm. Cell surface expression was confirmed by flow cytometry using the TI-35 mAb. The antibody response against NGO-Pr-54 was observed in patients with bladder (5.1%), liver (4.1%), lung (3.4%), ovarian (5.6%), and prostate (4.2%) cancer, as well as with malignant melanoma (13.2%).
    Cancer immunity: a journal of the Academy of Cancer Immunology 02/2008; 8:15.

Publication Stats

55 Citations
6.99 Total Impact Points


  • 2012-2015
    • Toyonaka Municipal Hospital
      Toyonaka, Ōsaka, Japan
  • 2008
    • Okayama University
      • Department of Pediatrics
      Okayama, Okayama, Japan