PDGF and PDGF receptors in glioma

The family of platelet-derived growth factors (PDGFs) plays a number of critical roles in normal embryonic development, cellular differentiation, and response to tissue damage. Not surprisingly, as it is a multi-faceted regulatory system, numerous pathological conditions are associated with aberrant activity of the PDGFs and their receptors. As we and others have shown, human gliomas, especially glioblastoma, express all PDGF ligands and both the two cell surface receptors, PDGFR-α and -β. The cellular distribution of these proteins in tumors indicates that glial tumor cells are stimulated via PDGF/PDGFR-α autocrine and paracrine loops, while tumor vessels are stimulated via the PDGFR-β. Here we summarize the initial discoveries on the role of PDGF and PDGF receptors in gliomas and provide a brief overview of what is known in this field

Different patterns of Epstein-Barr virus latency in endemic Burkitt lymphoma (BL) lead to distinct variants within the BL-associated gene expression signature

Epstein-Barr virus (EBV) is present in all cases of endemic Burkitt lymphoma (BL) but in few European/North American sporadic BLs. Gene expression arrays of sporadic tumors have defined a consensus BL profile within which tumors are classifiable as "molecular BL" (mBL). Where endemic BLs fall relative to this profile remains unclear, since they not only carry EBV but also display one of two different forms of virus latency. Here, we use early-passage BL cell lines from different tumors, and BL subclones from a single tumor, to compare EBV-negative cells with EBV-positive cells displaying either classical latency I EBV infection (where EBNA1 is the only EBV antigen expressed from the wild-type EBV genome) or Wp-restricted latency (where an EBNA2 gene-deleted virus genome broadens antigen expression to include the EBNA3A, -3B, and -3C proteins and BHRF1). Expression arrays show that both types of endemic BL fall within the mBL classification. However, while EBV-negative and latency I BLs show overlapping profiles, Wp-restricted BLs form a distinct subgroup, characterized by a detectable downregulation of the germinal center (GC)-associated marker Bcl6 and upregulation of genes marking early plasmacytoid differentiation, notably IRF4 and BLIMP1. Importantly, these same changes can be induced in EBV-negative or latency I BL cells by infection with an EBNA2-knockout virus. Thus, we infer that the distinct gene profile of Wp-restricted BLs does not reflect differences in the identity of the tumor progenitor cell per se but differences imposed on a common progenitor by broadened EBV gene expression

Loss of PIM2 enhances the anti-proliferative effect of the pan-PIM kinase inhibitor AZD1208 in non-Hodgkin lymphomas

Background A promising therapeutic approach for aggressive B-cell Non-Hodgkin lymphoma (NHL), including diffuse large B-cell lymphoma (DLBCL), and Burkitt lymphoma (BL) is to target kinases involved in signal transduction and gene regulation. PIM1/2 serine/threonine kinases are highly expressed in activated B-cell-like DLBCL (ABC-DLBCL) with poor prognosis. In addition, both PIM kinases have a reported synergistic effect with c-MYC in mediating tumour development in several cancers, c-MYC gene being translocated to one of the immunoglobulin loci in nearly all BLs. Methods For these reasons, we tested the efficiency of several PIM kinase inhibitors (AZD1208, SMI4a, PIM1/2 inhibitor VI and Quercetagetin) in preventing proliferation of aggressive NHL-derived cell lines and compared their efficiency with PIM1 and/or PIM2 knockdown. Results We observed that most of the anti-proliferative potential of these inhibitors in NHL was due to an off-target effect. Interestingly, we present evidence of a kinase-independent function of PIM2 in regulating cell cycle. Moreover, combining AZD1208 treatment and PIM2 knockdown additively repressed cell proliferation. Conclusion Taken together, this study suggests that at least a part of PIM1/2 oncogenic potential could be independent of their kinase activity, justifying the limited anti-tumorigenic outcome of PIM-kinase inhibitors in NHL

Über das sog. Sarcoma idiop. multiplex haemorrhagicum (Kaposi): Klinische und histologische Beiträge

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BCL-6 PROTEIN EXPRESSION IN HUMAN PERIPHERAL T-CELL NEOPLASMS IS RESTRICTED TO CD30+ ANAPLASTIC LARGE CELL LYMPHOMAS

The expression pattern of the BCL-6 transcription factor has been assessed in normal and neoplastic B-cell populations and in Hodgkin's disease. However, little is known about BCL-6 expression and its biological significance in T-cell neoplasms. In this study, a series of 59 lymphoma samples, including 27 CD30+ anaplastic large-cell lymphomas (ALCLs), 24 other peripheral T-cell neoplasms, and 8 T-cell lymphoblastic lymphomas (T-LBLs), as well as a panel of t(2;5)-positive lymphoma-derived human cell lines, were evaluated for BCL-6 protein expression by immunohistochemistry on frozen sections and cell smears. To define the relationship between BCL-6 protein and CD30 antigen in CD30+ ALCLs and in non-neoplastic lymph nodes, serial section immunohistochemistry and two-color staining were used in selected CD30+ ALCLs as well as in reactive lymph nodes with non-neoplastic T-cell proliferations. BCL-6 protein was expressed in 12 of 27 (45%) CD30+ ALCL cases, irrespective of their antigenic phenotypes (T-cell or null-cell type), and in the t(2;5)-positive cell lines. In contrast, the remaining 24 peripheral T-cell neoplasms as well as the 8 T-LBLs were considered negative for BCL-6 expression. Coexpression of CD30 and BCL-6, as detected in CD30+ ALCLs, was also found in a subset of non-neoplastic lymphoid elements, namely the large lymphoid cells scattered in the interfollicular areas of reactive lymph nodes. These findings suggest that CD30+ ALCLs may represent the neoplastic transformation of extrafollicular CD30+ cells and that BCL-6 may provide an additional marker for characterizing CD30+ ALCLs

BCL-6 PROTEIN EXPRESSION IN AIDS-RELATED NON-HODGKIN's LYMPHOMAS. INVERSE RELATIONSHIP WITH EPSTEIN-BARR VIRUS-ENCODED LATENT MEMBRANE PROTEIN-1 EXPRESSION

This study aimed at investigating the expression of the BCL-6 protein in acquired immune deficiency syndrome (AIDS)-related non-Hodgkin's lymphomas (AIDS-NHLs) and at comparing the expression pattern with the presence of Epstein-Barr virus (EBV) infection of the tumor clone. A total of 34 AIDS-NHL biopsies, including 16 AIDS-related diffuse large-cell lymphomas (AIDS-DLCLs) and 18 AIDS-related small-noncleaved-cell lymphomas (AIDS-SNCCLs) as well as 7 AIDS-SNCCL cell lines were immunostained with a BCL-6-specific monoclonal antibody. Expression of BCL-6 protein was detected in 9 of 16 AIDS-DLCLs, 18 of 18 AIDS-SNCCLs, and 3 of 7 AIDS-SNCCL cell lines. Expression of BCL-6 among AIDS-NHLs occurred independently of the presence of molecular lesions of the bcl-6 gene. Notably, among EBV-positive AIDS-NHL biopsies and cell lines, expression of BCL-6 was mutually exclusive with the expression of EBV-encoded transforming antigen latent membrane protein-1. The mutual exclusion between BCL-6 and latent membrane protein-1 expression was further confirmed by in vitro superinfection experiments of an AIDS-SNCCL cell line originally devoid of EBV sequences. Overall, the frequent association between AIDS-NHLs and expression of BCL-6, a protein selectively expressed by germinal center B cells, suggests that these lymphomas may originate from the germinal center

HIV-ASSOCIATED HODGKIN'S DISEASE DERIVES FROM POST-GERMINAL CENTER B-CELLS

Human immunodeficiency virus-associated Hodgkin's disease (HIV-HD) displays several peculiarities when compared with HD of the general population. These include overrepresentation of clinically aggressive histologic types and frequent infection of Reed-Sternberg (RS) cells by Epstein-Barr virus (EBV). Recently, we have reported that the histogenesis of HD of the general population may be assessed by monitoring the expression pattern of BCL-6, a transcription factor expressed in germinal center (GC) B cells, and of CD138/syndecan-1 (syn-1), a proteoglycan associated with post-GC, terminal B-cell differentiation. In this study, we have applied these two markers to the study of HIV-HD histogenesis and correlated their expression status to the virologic features of this disease. We have found that RS cells of all histologic categories of HIV-HD consistently display the BCL-6(-)/syn-1(+) phenotype and thus reflect post-GC B cells. Although BCL-6(-)/syn-1(+) RS cells of HIV-HD express CD40, they are not surrounded by CD40 ligand-positive (CD40L+) reactive T lymphocytes, which, in HD of the general population, are thought to regulate the disease phenotype through CD40/CD40L interactions. Conversely, RS cells of virtually all HIV-HD express the EBV-encoded latent membrane protein 1 (LMP1), which, being functionally homologous to CD40, may contribute, at least in part, to the modulation of the HIV-HD phenotype

EXPRESSION STATUS OF BCL-6 AND SYNDECAN-1 IDENTIFIES DISTINCT HISTOGENETIC SUBSETS OF HODGKIN'S DISEASE

The tumor cells in most cases of Hodgkin's disease (HD) have been recently recognized to originate from the B-cell lineage, but their precise differentiation stage is not fully clarified. Recently, we have reported that the histogenesis of B-cell lymphomas may be assessed by monitoring the expression pattern of BCL-6, a transcription factor expressed in germinal center (GC) B cells, and CD138/syndecan-1 (syn-1), a proteoglycan associated with post-GC, terminal B-cell differentiation. In this study, we have applied these two markers to the study of HD histogenesis. We have found that in nodular lymphocyte predominance HD (NLPHD) tumor cells consistently display the BCL-6(+)/syn-1(-) phenotype, indicating their derivation from GC B cells. Conversely, classic HD (CHD) is heterogeneous because the tumor cells of a fraction of CHD display the BCL-6(-)/syn-1(+) phenotype of post-GC B-cells, whereas another fraction of CHD is constituted by a mixture of tumor cells reflecting the GC (BCL-6(+)/syn-1(-)) or post-GC (BCL-6(-)/syn-1(+)) phenotypes. BCL-6(-)/syn-1(+) tumor cells of CHD are mostly found surrounded by T cells expressing CD40L, consistent with the observation that CD40 signaling downregulates BCL-6 expression. These data indicate that tumor cells of NLPHD uniformly display a GC B-cell phenotype, whereas the phenotype of tumor cells of CHD appears to be modulated by the surrounding cellular background, particularly CD40L+ reactive T cells