Yuhei Kamada

University of Tsukuba, Tsukuba, Ibaraki, Japan

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Publications (7)48.69 Total impact

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    ABSTRACT: TET2 (Ten Eleven Translocation 2) is a dioxygenase that converts methylcytosine (mC) to hydroxymethylcytosine (hmC). TET2 loss-of-function mutations are highly frequent in subtypes of T-cell lymphoma that harbor follicular helper T (Tfh)-cell-like features, such as angioimmunoblastic T-cell lymphoma (30-83%) or peripheral T-cell lymphoma, not otherwise specified (10-49%), as well as myeloid malignancies. Here, we show that middle-aged Tet2 knockdown (Tet2(gt/gt)) mice exhibit Tfh-like cell overproduction in the spleen compared with control mice. The Tet2 knockdown mice eventually develop T-cell lymphoma with Tfh-like features after a long latency (median 67 weeks). Transcriptome analysis revealed that these lymphoma cells had Tfh-like gene expression patterns when compared with splenic CD4-positive cells of wild-type mice. The lymphoma cells showed lower hmC densities around the transcription start site (TSS) and higher mC densities at the regions of the TSS, gene body and CpG islands. These epigenetic changes, seen in Tet2 insufficiency-triggered lymphoma, possibly contributed to predated outgrowth of Tfh-like cells and subsequent lymphomagenesis. The mouse model described here suggests that TET2 mutations play a major role in the development of T-cell lymphoma with Tfh-like features in humans.
    Full-text · Article · Dec 2014 · Blood Cancer Journal
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    ABSTRACT: In leukemogenesis, Notch signaling can be up- and down-regulated in a context-dependent manner. The transcription factor hairy and enhancer of split-1 (Hes1) is well characterized as a downstream target of Notch signaling. Hes1 encodes a basic helix-loop-helix-type protein, and represses target gene expression. Here we report that deletion of the Hes1 gene in mice promotes acute myeloid leukemia (AML) development induced by the MLL-AF9 fusion protein. We then found that Hes1 directly bound to the promoter region of the FMS-like tyrosine kinase 3 (FLT3) gene and down-regulated the promoter activity. FLT3 was consequently up-regulated in MLL-AF9-expressing immortalized and leukemia cells with a Hes1- or RBPJ-null background. MLL-AF9-expressing Hes1-null AML cells showed enhanced proliferation and ERK phosphorylation following FLT3 ligand stimulation. FLT3 inhibition efficiently abrogated proliferation of MLL-AF9-induced Hes1-null AML cells. Furthermore, an agonistic anti-Notch2 antibody induced apoptosis of MLL-AF9-induced AML cells in a Hes1-wild type but not a Hes1-null background. We also accessed two independent databases containing mRNA expression profiles and found that the expression level of FLT3 mRNA was negatively correlated with those of HES1 in patient AML samples. These observations demonstrate that Hes1 mediates tumor suppressive roles of Notch signaling in AML development, probably by down-regulating FLT3 expression.Leukemia accepted article preview online, 19 September 2014. doi:10.1038/leu.2014.281.
    No preview · Article · Sep 2014 · Leukemia
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    ABSTRACT: Angioimmunoblastic T cell lymphoma (AITL) is a distinct subtype of peripheral T cell lymphoma characterized by generalized lymphadenopathy and frequent autoimmune-like manifestations. Although frequent mutations in TET2, IDH2 and DNMT3A, which are common to various hematologic malignancies, have been identified in AITL, the molecular pathogenesis specific to this lymphoma subtype is unknown. Here we report somatic RHOA mutations encoding a p.Gly17Val alteration in 68% of AITL samples. Remarkably, all cases with the mutation encoding p.Gly17Val also had TET2 mutations. The RHOA mutation encoding p.Gly17Val was specifically identified in tumor cells, whereas TET2 mutations were found in both tumor cells and non-tumor hematopoietic cells. RHOA encodes a small GTPase that regulates diverse biological processes. We demonstrated that the Gly17Val RHOA mutant did not bind GTP and also inhibited wild-type RHOA function. Our findings suggest that impaired RHOA function in cooperation with preceding loss of TET2 function contributes to AITL-specific pathogenesis.
    No preview · Article · Jan 2014 · Nature Genetics
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    ABSTRACT: Single-nucleotide polymorphism genotyping microarray (SNP array) analysis provides detailed information on chromosomal copy number aberrations. To obtain detailed information on genomic abnormalities related to pathogenesis or prognosis of multiple myeloma (MM), we performed 250K SNP array analysis in 39 MM patients and 11 cell lines. We identified an accumulation of deletions and uniparental disomies at 22q12.1. Among the hyperdiploid MM cases, chromosomal imbalance at this locus was associated with poor prognosis. On sequencing, we also found a mutation in the seizure-related 6 homolog (mouse)-like (SEZ6L) gene located at ch.22q12.1 in an MM cell line, NOP1. We further found isolated deletions in 17 genes, five of which are known tumor suppressor genes. Of these, deletion of protein tyrosine phosphatase, receptor type D (PTPRD) was found in three samples, including two patients. Consistent with previous reports, non-hyperdiploid MM, deletion of 13q (del13q) and gain of 1q in non-hyperdiploid MMs were predictive of poor prognosis (p = 0.039, p = 0.049, and p = 0.013, respectively). However, our analysis revealed that unless accompanied by gain of 1q, the prognosis of non-hyperdiploid MM was as good as that of hyperdiploid MM. Thus, SNP array analysis provides significant information useful to understanding the pathogenesis and prognosis of MM.
    No preview · Article · Sep 2012 · International journal of hematology
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    ABSTRACT: We report the case of a 37-year-old woman who had a relapse of acute myeloid leukemia (AML) during treatment for chronic graft versus host disease (cGVHD) after allogeneic bone marrow transplantation. She was originally suspected of having autoimmune pancreatitis. Relapse of AML often occurs at extramedullary sites. Whereas the pancreas is rare as an organ of AML relapse, physicians should be aware that enlargement of the pancreas could be a sign of relapsed AML when excluding autoimmune pancreatitis, particularly during active cGVHD after allogeneic stem cell transplantation.
    Full-text · Article · Jan 2011
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    ABSTRACT: We report a rare case of autoimmune hemolytic anemia (AIHA) complicated by idiopathic interstitial pneumonia (IIP). A sixty-year-old man was diagnosed as having IIP in January 2009. In March, when he was hospitalized for the introduction of home oxygen therapy, severe anemia was detected. Based on the findings showing elevated levels of lactate dehydrogenase and indirect bilirubin, a decreased level of haptoglobin, positive Coombs test, and splenomegaly, a diagnosis of AIHA was made. Although anti-DNA antibody was found, diagnostic criteria for systemic lupus erythematosus and other collagen diseases were not fulfilled. Therefore, we concluded that AIHA coexisted with IIP. Treatment with prednisolone led to improvement of both AIHA and IIP. There has not been any exacerbation even after a gradual reduction of prednisolone to 7.5 mg/day. Coexistence of AIHA and IIP is rare, and accumulation of case reports is needed to gain a better understanding of this condition.
    No preview · Article · Jan 2011 · [Rinshō ketsueki] The Japanese journal of clinical hematology
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    ABSTRACT: Human T-cell lymphotropic virus type 1 (HTLV-1) causes adult T-cell leukemia and inflammatory disorders. Aberrant activation of nuclear factor-κB (NF-κB) has been linked to HTLV-1 pathogenesis and to various kinds of cancers, including adult T-cell leukemia. NF-κB-inducing kinase (NIK) is critical for non-canonical activation of NF-κB and for the development of lymphoid organs. HTLV-1 activates NF-κB by the non-canonical pathway, but examination of the role of NIK in proliferation of HTLV-1-infected cells in vivo has been hindered by lack of a suitable animal model. Alymphoplasia (aly/aly) mice bear a mutation of NIK, resulting in defects in the development of lymphoid organs and severe deficiencies in both humoral and cell-mediated immunity. In the present study we therefore used a mouse model of HTLV-1 infection with aly/aly mice. The number of HTLV-1-infected cells in the reservoir organs in aly/aly mice was significantly smaller than in the control group 1 month after infection. In addition, aly/aly mice did not maintain provirus for 1 year and antibodies against HTLV-1 were undetectable. These results demonstrate that the absence of functional NIK impairs primary HTLV-1 proliferation and abolishes the maintenance of provirus. Interestingly, clonal proliferation of HTLV-1-infected mouse cells was not detected in aly/aly mice, which is consistent with the lack of HTLV-1 persistence. These observations imply that the clonal proliferation of HTLV-1-infected cells in secondary lymphoid organs might be important for HTLV-1 persistence. (Cancer Sci 2008; 99: 872–878)
    Full-text · Article · May 2008 · Cancer Science