title: BCL-6 protein is expressed in germinal-center B cells.
abstract: Structural alterations of the 5' noncoding region of the BCL-6 gene have been found in 40% of diffuse large cell lymphoma (DLCL) and 5% to 10% of follicular lymphomas (FL), suggesting that deregulated BCL-6 expression may play a role in lymphomagenesis. Nucleotide sequencing of BCL-6 cDNA predicted a protein containing six zinc-finger domains, suggesting that it may function as a transcription factor. Using antisera raised against N- and C-terminal BCL-6 synthetic oligopeptides in immunoprecipitation, immunoblot, and immunocytochemical assays, this study identifies the BCL-6 gene product as a 95-kD nuclear protein. Western blot analysis of human tumor cell lines representative of various hematopoietic lineages/stages of differentiation showed that the BCL-6 protein is predominantly expressed in the B-cell lineage where it was found in mature B cells. Immunohistochemical analysis of normal human lymphoid tissues indicated that BCL-6 expression is topographically restricted to germinal centers including all centroblasts and centrocytes. The BCL-6 protein was also detectable in inter- and intra-follicular CD4+ T cells, but not in other follicular components including mantle-zone B cells, plasma cells, dendritic cells, and macrophages. Immunohistochemical analysis of DLCL and FL biopsy samples showed that the BCL-6 protein is detectable in these tumors independent of the presence of BCL-6 gene rearrangements. These results indicate that the expression of the BCL-6 gene is specifically regulated during B-cell differentiation and suggest a role for BCL-6 in germinal center development or function. Because DLCL derive from germinal-center B cells, deregulated BCL-6 expression may contribute to lymphomagenesis by preventing postgerminal center differentiation.
authors.affiliation: Department of Pathology, College of Physicians & Surgeons, Columbia University, New York, NY 10032, USA.
authors.forename: G
authors.initials: G
authors.lastname: Cattoretti
authors.forename: C C
authors.initials: CC
authors.lastname: Chang
authors.forename: K
authors.initials: K
authors.lastname: Cechova
authors.forename: J
authors.initials: J
authors.lastname: Zhang
authors.forename: B H
authors.initials: BH
authors.lastname: Ye
authors.forename: B
authors.initials: B
authors.lastname: Falini
authors.forename: D C
authors.initials: DC
authors.lastname: Louie
authors.forename: K
authors.initials: K
authors.lastname: Offit
authors.forename: R S
authors.initials: RS
authors.lastname: Chaganti
authors.forename: R
authors.initials: R
authors.lastname: Dalla-Favera
mesh_terms: D000595:Amino Acid Sequence; D000944:Antigens, Differentiation, B-Lymphocyte / Q000032:analysis; D016175:B-Lymphocyte Subsets / Q000378:metabolism*; D001854:Bone Marrow Cells; D002051:Burkitt Lymphoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D002454:Cell Differentiation; D002467:Cell Nucleus / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D054278:Embryonal Carcinoma Stem Cells; D015972:Gene Expression Regulation, Neoplastic; D006412:Hematopoietic Stem Cells / Q000378:metabolism; D006801:Humans; D016130:Immunophenotyping; D008198:Lymph Nodes / Q000166:cytology*; D016393:Lymphoma, B-Cell / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D008224:Lymphoma, Follicular / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D016403:Lymphoma, Large B-Cell, Diffuse / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000235:genetics; D014411:Neoplastic Stem Cells / Q000378:metabolism; D014066:Palatine Tonsil / Q000166:cytology*; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis* / Q000235:genetics; D051560:Proto-Oncogene Proteins c-bcl-6; D014157:Transcription Factors / Q000096:biosynthesis* / Q000235:genetics; D014407:Tumor Cells, Cultured
chemical_list: D000944:Antigens, Differentiation, B-Lymphocyte; D004268:DNA-Binding Proteins; D009363:Neoplasm Proteins; D011518:Proto-Oncogene Proteins; D051560:Proto-Oncogene Proteins c-bcl-6; D014157:Transcription Factors