Atsushi Kitabayashi

Transmembrane signaling through CD80 (B7-1) induces growth arrest and cell spreading of human B lymphocytes accompanied by protein tyrosine phosphorylation

We addressed the issue of the role for CD80 (B7-1) expressed on human B cells in transmembrane signaling. Cross-linking of CD80 on B lymphoma Raji cells induced tyrosine phosphorylation in 160-, 120-, 55-, 46- and 44-kDa proteins, which was inhibited by genistein. CD80-mediated signaling resulted in the inhibition of DNA replication of B cells and induced the changes in morphology like macrophages or fibroblasts. This cell spreading was inhibited by the pre-treatment of the cells with genistein. These results suggest that the CD80 antigen is involved in transmembrane outside-in signaling in B cells and its biological effects appear to be mediated by tyrosine kinases.

Bortezomib reduces the tumorigenicity of multiple myeloma via downregulation of upregulated targets in clonogenic side population cells.

Side population (SP) cells in cancers, including multiple myeloma, exhibit tumor-initiating characteristics. In the present study, we isolated SP cells from human myeloma cell lines and primary tumors to detect potential therapeutic targets specifically expressed in SP cells. We found that SP cells from myeloma cell lines (RPMI 8226, AMO1, KMS-12-BM, KMS-11) express CD138 and that non-SP cells include a CD138-negative population. Serial transplantation of SP and non-SP cells into NOD/Shi-scid IL-2γnul mice revealed that clonogenic myeloma SP cells are highly tumorigenic and possess a capacity for self-renewal. Gene expression analysis showed that SP cells from five MM cell lines (RPMI 8226, AMO1, KMS-12-BM, KMS-11, JJN3) express genes involved in the cell cycle and mitosis (e.g., CCNB1, CDC25C, CDC2, BIRC5, CENPE, SKA1, AURKB, KIFs, TOP2A, ASPM), polycomb (e.g., EZH2, EPC1) and ubiquitin-proteasome (e.g., UBE2D3, UBE3C, PSMA5) more strongly than do non-SP cells. Moreover, CCNB1, AURKB, EZH2 and PSMA5 were also upregulated in the SPs from eight primary myeloma samples. On that basis, we used an aurora kinase inhibitor (VX-680) and a proteasome inhibitor (bortezomib) with RPMI 8226 and AMO1 cells to determine whether these agents could be used to selectively target the myeloma SP. We found that both these drugs reduced the SP fraction, though bortezomib did so more effectively than VX-680 due to its ability to reduce levels of both phospho-histone H3 (p-hist. H3) and EZH2; VX-680 reduced only p-hist. H3. This is the first report to show that certain oncogenes are specifically expressed in the myeloma SP, and that bortezomib effectively downregulates expression of their products. Our approach may be useful for screening new agents with which to target a cell population possessing strong tumor initiating potential in multiple myeloma.

Invasive pulmonary mucormycosis with rupture of the thoracic aorta.

We report an acute myelogenous leukemia patient with mucormycosis who died of massive hemoptysis during antifungal therapy. The diagnosis was made postmortem and autopsy revealed that the pulmonary nodule consisting of mucorales protruded over the luminal surface of the aorta. Microscopic examination showed the invasion of mucor hyphae into the wall of the aortic arch. Surgical treatment may be indicated for patients with pulmonary mucormycosis refractory to amphotericin B therapy. Am. J. Hematol. 58:326–329, 1998.

Fluorescence In Situ Hybridization Monitoring of BCR-ABL-Positive Neutrophils in Chronic-Phase Chronic Myeloid Leukemia Patients during the Primary Stage of Imatinib Mesylate Therapy

We describe a method for monitoring chronic myeloid leukemia (CML) patients treated with imatinib that uses fluorescence in situ hybridization (FISH) to detect BCR- ABL in peripheral blood (PB) granulocytes. First, we compared this method, termed Neutrophil- FISH, with interphase FISH (i-FISH) analysis of bone marrow (BM), i-FISH analysis of PB mononuclear cells, and conventional cytogenetic analysis (CCA) of BM in 30 consecutive CML patients. We found the percentage of BCR- ABL-positive neutrophils as determined by Neutrophil-FISH to correlate best with the percentage of Philadelphia chromosome-positive metaphases in the BM determined by CCA (y = 0.8818x + 5.7249; r2 = 0.968). We then performed a serial Neutrophil-FISH study of 10 chronic-phase CML patients treated with imatinib and found that the technique could clearly separate imatinib responders from nonresponders within 12 weeks of drug administration. There was a significant difference in the percentages of BCR- ABL-positive neutrophils between responder (mean ± SD, 18.2% ± 11.8%) and nonresponder (82.4% ± 5.1%) groups at 12 weeks (P <.0001, Student t test). Together with real-time quantitative polymerase chain reaction analysis, Neutrophil-FISH represents another useful method for monitoring CML patients during the primary myelosuppressive stage of imatinib therapy because it is a quick, simple, and reliable method for assessing cytogenetic response.

Hypoxia-inducible microRNA-210 regulates the DIMT1-IRF4 oncogenic axis in multiple myeloma

Multiple myeloma (MM) is characterized by the accumulation of a population of malignant plasma cells within the bone marrow and its microenvironment. A hypoxic niche is located within the microenvironment, which causes myeloma cells to become quiescent, anti‐apoptotic, glycolytic, and immature. Cell heterogeneity may be related to distinct gene expression profiles under hypoxic and normoxic conditions. During hypoxia, myeloma cells acquire these phenotypes by downregulating interferon regulatory factor 4 (IRF4), an essential transcription factor in myeloma oncogenesis. To identify essential microRNAs and their targets regulated under hypoxic conditions, we undertook microRNA and cDNA microarray analyses using hypoxia‐exposed primary MM samples and myeloma cell lines. Under hypoxia, only miR‐210 was highly upregulated and was accompanied by direct downregulation of an 18S rRNA base methyltransferase, DIMT1. This inverse expression correlation was validated by quantitative RT‐PCR for primary MM samples. We further determined that DIMT1 has an oncogenic potential as its knockdown reduced tumorigenicity of myeloma cells through regulation of IRF4 expression. Notably, by analyzing gene expression omnibus datasets in the National Center for Biotechnology Information database, we found that DIMT1 expression increased gradually with MM progression. In summary, by screening for targets of hypoxia‐inducible microRNA‐210, we identified DIMT1 as a novel diagnostic marker and therapeutic target for all molecular subtypes of MM.

Extensive intraglomerular thrombi of monoclonal IgM-Κ in a patient with malignant lymphoma

Abstract We describe an 80-year-old man who developed malignant lymphoma (ML) complicated by extensive intraglomerular thrombi of immunoglobulin M (IgM)-Κ monoclonal immunoglobulin. The clinical picture was characterized by nephrotic syndrome and systemic lymphadenopathy. Laboratory examination showed mild anemia and a small amount of monoclonal IgM-Κ in the blood. The histopathologic findings and surface immunoglobulin analysis of the lymph node biopsy specimen were consistent with CD5-positive diffuse large B-cell (type, IgM-Κ) lymphoma. The subsequent renal biopsy showed a massive deposition of amorphous material in the glomerular capillary lumens, subendothelial areas, and mesangium. Nodular glomerulosclerosis was not found. An immunofluorescent study showed that the deposits consisted of IgM-Κ monoclonal immunoglobulin. Ultrastructurally, the deposits were composed of granular electron-dense material. Chemotherapy was effective for both the ML and nephrotic syndrome, and the patients urine analysis results returned to normal. The histopathologic manifestations of this case are rare, and the pathogenesis of these glomerular lesions was obviously associated with ML.

Autoreactive T Cell-Dependent Polyclonal Hypergammaglobulinemia in Mantle

We investigated the mechanism of polyclonal B cell differentiation in mantle cell lymphoma (MCL) using peripheral blood mononuclear cells (PBMC) from a patient with MCL in leukemic stage presenting polyclonal hypergammaglobulinemia. Patient T cells not only responded to autologous non-T cells but induced polyclonal production of IgG in vitro. Flow cytometric analysis of PBMC showed the increased conversion of CD4+ T cells from the naive to the memory state. We propose the possible mechanism that autoreactive T cells may be involved in polyclonal B cell differentiation in this monoclonal B cell disorder.