Expression of Microglial Markers in Diffuse Large B-Cell Lymphomas of the Central Nervous System
A Sasaki, H Yamaguchi, M Ikeda, A Yokohama, Y Nakazato, M Shimizu. Saitama Medical University, International Medical Center, Hidaka, Saitama, Japan; Gunma University School of Health Science, Maebashi, Gunma, Japan; Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan
Background: Diffuse large B-cell lymphomas (DLBCL) are the most common type of primary central nervous system lymphoma (PCNSL). Our previous study indicated that the number of apoptotic cells were significantly higher in CNS DLBCL than in non-CNS DLBCL. The great majority of tumors that have been previously termed as microglioma actually represent PCNSL. In this study, we examined CNS DLBCL, non-CNS DLBCL and a human B cell lymphoma cell line to determine the relationship between microglia and lymphoma cells.
Design: Twenty cases of CNS DLBCL and 11 cases of non-CNS DLBCL were studied by immunohistochemistry (IHC) using antibodies against glucose transporter 5 (GLUT5), Iba1 and CD68 (PG-M1). Both double-labeling with terminal deoxynucleotidyl transferase-mediated dUTP-nick end labeling (TUNEL) and Iba1 IHC and double immunofluorescence analysis of GLUT5 and CD20 (L26) were performed in a representative case of CNS DLBCL. GLUT5 immunostaining in neoplastic cells of DLBCLs was semiquantitatively evaluated by counting the percentage of labeled cells. Immunocytochemical and Western blot analyses of GLUT5 expression were performed using the Raji cell line.
Results: In all cases of CNS-DLBCLs, activated microglia and macrophages were labeled with all three antibodies against GLUT5, Iba1 and CD68. Double labeling of TUNEL and Iba1 IHC showed some macrophages with phagocytosis of apoptotic cells. In all cases of CNS DLBCL, neoplastic lymphocytes were stained with GLUT5 antibody in a variable number in all cases, but not stained with either Iba1 or CD68 antibodies. Semi-quantitatively, five of 20 cases (25%) showed numerous GLUT5-positive lymphoma cells (more than 50% labeled cells). In double immunofluorescence staining for GLUT5 and L26, double-positive cells were observed. In non-CNS DLBCLs, lymphoma cells were stained with GLUT5, but not with Iba1 or CD68. The GLUT5 immunoreactivity was observed on Raji cells by both immunocytochemistry and Western blot analysis.
Conclusions: The present study indicated that CNS DLBCLs contain a large number of microglia and macrophages and that macrophages could be involved in the removal of apoptotic cells. Our findings demonstrated that expression of GLUT5 is frequently induced on lymphoma cells in the CNS, although this GLUT5 expression on lymphoma cells is unlikely to support the microglial origin of CNS lymphoma.
Tuesday, March 23, 2010 1:00 PM
Poster Session IV # 237, Tuesday Afternoon