Primary Effusion Lymphoma Tumor Research Articles

Inhibition of KSHV infected primary effusion lymphomas in NOD/SCID mice by γ-secretase inhibitor

Primary effusion lymphoma (PEL) is a common cancer in AIDS patients closely associated with Kaposi’s sarcoma-associated herpesvirus (KSHV). Previously, we showed that KSHV latency associated nuclear antigen (LANA) stabilizes intracellular activated Notch1 (ICN) involved in maintenance of the malignant phenotype of KSHV infected PEL cells in vitro. The γ-secretase inhibitor (GSI) which specifically blocks the production of ICN slows down the proliferation of the KSHV infected PEL cell lines BCBL1, BC3 as well as JSC1 in vitro. In this study, we extended these studies to explore the possibility that manipulation of the Notch signaling by GSI would prevent the growth of the PEL tumors in vivo. We observed that the onset of tumorigenesis of KSHV infected PELs was significantly delayed in GSI treated SCID mice harboring the PEL cell lines. We also found that GSI treatment resulted in necrosis as well as apoptosis in tumors generated by the xenotransplanted KSHV positive PEL cell lines. In contrast, GSI had no effect on mice harboring BJAB cells, a KSHV negative Burkitt’s lymphoma cell line where ICN levels were negligible. Our study provides further evidence to suggest that targeted down-regulation of abnormal Notch signaling has therapeutic potential for KSHV related primary effusion lymphomas.

Transient induction of lytic Kaposi's sarcoma-associated herpesvirus (KSHV) genes in KSHV-infected endothelial cells exposed to hypoxia

Kaposi's sarcoma-associated herpesvirus (KSHV), also called human herpesvirus-8 (HHV-8) is the causative agent of Kaposi's sarcoma (KS), primary effusion lymphoma (PEL), and a form of multicentric Castleman's disease (MCD). Two of these tumors, KS and PEL, tend to arise in areas of the body that are relatively hypoxic. Exploring this phenomenon, our group has previously found that KSHV in PEL tumor cell lines is activated to lytic replication by hypoxia and that certain KSHV genes are activated by hypoxia inducible factors (HIF-1 and HIF-2) through functional hypoxia response elements (HRE) (Davis et al., Blood, 2001, 15, 3244–50; Haque et al., J. Virol., 2006, 80, 7037–51). KS tumor cells are thought to be derived from endothelial cells or their precursors, and in the current study, we have addressed the question of whether KSHV was similarly activated to lytic replication in KSHV-infected endothelial cells. To investigate this, we infected primary dermal microvascular endothelial cells (DMEC) derived from human foreskin with a recombinant KSHV (rKSHV.219) that was engineered to contain red fluorescent protein (RFP) controlled by the lytic PAN RNA promoter as a lytic marker and green fluorescent protein under the control of human elongation factor 1-α promoter as a latent marker (gift of Dr. Jeff Vieira). Short-term ( 24 hours, there was a subsequent downregulation of KSHV lytic genes and of the production of virus despite continued upregulation of HIF-2 in the cells. We hypothesized that this late downregulation might be from production of one or more cellular factors with KSHV-suppressive activity in these cells upon exposure to hypoxia. We focused on IL-1β, IL-6, IL-8, tumor necrosis factor alpha (TNFα) and vascular endothelial growth factor (VEGF), as these are known to be produced by hypoxic endothelial cells and to be expressed by KSHV-infected cells in vitro and in KS lesions. IL-6, IL-1β and VEGF had no effect on lytic replication and IL8 increased replication in the KSHV-infected DMEC. However, TNFα blocked the expression of RTA, vIL6, ORF45 and K5 proteins and suppressed production of KSHV virions in the supernatant. Furthermore, when the cells were treated with blocking antibodies directed against human TNFα, KSHV lytic activation in the hypoxic DMEC was partially restored. Interestingly, established monolayers of KSHV-infected DMEC cells cultured in hypoxia out-survived normoxic cells cultured in parallel; this provided evidence that suppression of KSHV by TNFα was not simply from cell killing. These results suggest that production of TNFα by KSHV-infected endothelial cells may limit activation of lytic KSHV replication by hypoxia and that this effect may promote survival of KSHV-infected cells under hypoxic conditions and contribute to the pathogenesis of KS. This research was supported in part by the Intramural Research Program of the NIH, NCI.

Extracavitary tumor after primary effusion lymphoma: relapse or second distinct lymphoma?

HHV-8-associated solid lymphomas which develop in extracavitary sites during the course of primary effusion lymphoma (PEL) could represent the relapse of original PEL tumors in different anatomical sites, or newly occurring distinct HHV-8-associated lymphomas, such as multicentric Castleman disease-related microlymphomas. HHV-8 episome clonality might help identify which event takes place.

Mono/oligoclonal pattern of Kaposi Sarcoma‐associated herpesvirus (KSHV/HHV‐8) episomes in primary effusion lymphoma cells

Primary effusion lymphoma (PEL) is a rare lymphoma of B-cell origin, developed in serous cavities. PEL tumor cells are latently infected with Kaposi sarcoma-associated herpesvirus (KSHV) and in most cases co-infected with Epstein-Barr virus (EBV). In 15 primary PEL tumors including 10 EBV-positive cases, we analyzed the fused terminal repeat (TR) regions of KSHV episomes using pulsed-field gel electrophoresis and Southern blot. On the same genomic DNA samples, the cellular clonality was assessed by Southern blot and PCR detection of monoclonal immunoglobulin heavy chain (IGH) VDJ gene rearrangements, associated in the EBV-infected cases, with Southern blot analysis of the fused termini of EBV episomes. Monoclonal IGH gene rearrangements were detected in 13 tumors using Southern blot, in 11 cases using PCR, and in all cases considering both methods. EBV infection was monoclonal in all EBV-positive cases. However, only 5 PEL tumors were found to be monoclonally infected with KSHV. In the 10 other cases, we found a biclonal (2 bands; n = 4) or an oligoclonal pattern (3-6 bands; n = 6) of KSHV episomes. We hypothesized that the apparent discrepancy between viral and cellular clonalities in PEL might be due to several phenomena including complex mechanisms of genomic recircularization, insertion of duplicated sequences into the TR region and simultaneous infection of tumor cells with defective KSHV variants. KSHV infection of contaminating nontumoral cells, superinfection from lytically infected cells or viral integration events might also explain the oligoclonal pattern of KSHV infection. Several of these mechanisms, not mutually exclusive, might coexist in a single tumor.

Kaposi's Sarcoma-Associated Herpesvirus/Human Herpesvirus Type 8-Positive Solid Lymphomas: A Tissue-Based Variant of Primary Effusion Lymphoma

Kaposi's sarcoma-associated herpesvirus (KSHV), also termed human herpesvirus type 8, is consistently identified in Kaposi's sarcoma, primary effusion lymphoma (PEL), and multicentric Castleman's disease. Here we report four cases of KSHV-bearing solid lymphomas that occurred in AIDS patients (cases 1 to 3) and in a human immunodeficiency virus (HIV)-seronegative person (case 4). The patients presented extranodal masses in the abdomen (cases 1, 3, and 4) or skin (case 2), and nodal involvement, together with Kaposi's sarcoma (case 3). The gastrointestinal tract was involved in two patients (cases 1 and 3). The patients did not develop a lymphomatous effusion. KSHV was detected in the tumor cells of all cases by immunohistochemistry and by polymerase chain reaction. Epstein-Barr virus was detected in two of the HIV-related cases. All KSHV-positive solid lymphomas exhibited PEL-like cell morphology. To investigate the relationship of these disorders to PEL and to other AIDS-associated diffuse large cell lymphomas, KSHV-positive solid lymphomas were tested for the expression of a set of genes that were previously shown by gene profiling analysis to define PEL tumor cells. The results showed that expression of this set of genes in KSHV-positive lymphomas is similar to that of PEL but distinct from KSHV-negative AIDS-associated diffuse large cell lymphomas. Because pathobiological features of KSHV-positive solid lymphomas closely mimic those of PEL, our results suggest that KSHV-positive solid lymphomas should be considered as a tissue-based variant of classical PEL, irrespective of HIV status.

Oligoclonal/Multiclonal Pattern of Kaposi Sarcoma-Associated Herpesvirus (KSHV/HHV-8) Episomes in Primary Effusion Lymphoma Cells.

Primary effusion lymphoma (PEL) is a rare non-Hodgkin lymphoma of B-cell lineage origin, developed in the serous body cavities and mostly observed in the course of HIV infection. PEL tumor cells are latently infected with Kaposi sarcoma-associated herpesvirus (KSHV) and in most cases, co-infected with Epstein-Barr virus (EBV). As a virological marker of clonality in PEL, we analyzed the fused terminal repeat regions (TR) of KSHV episomes using pulsed-field gel electrophoresis and Southern blot hybridization, in 15 primary PEL tumors including 10 EBV+ cases, and in 6 PEL cell lines. The cellular clonality was assessed on the same genomic DNA samples, by Southern blot and PCR detection of monoclonal immunoglobulin heavy chain (IgH) VDJ gene rearrangements, associated in the co-infected PEL with Southern blot analysis of the fused termini of EBV episomes. Monoclonal IgH gene rearrangements were detected in 87% (13/15) of primary PEL tumors using Southern blot, in 73% (11/15) using PCR analysis, and in all tumors considering both methods. All the co-infected PEL also displayed a monoclonal EBV infection. However, only 5 primary PEL tumors were found to be monoclonally infected with KSHV. In the 10 remaining cases, as well as in the KSHV+/EBV-negative BC-3 cell line, we found a biclonal (2 bands)(n=3) or an oligoclonal/multiclonal pattern (3–6 bands)(n=7) of KSHV episomes. KSHV infection of non-tumoral contaminating cells, superinfection mechanisms from lytically infected tumor cells, or viral integration events might explain such discordant findings between the viral and cellular clonality of PEL.

Gene expression profile analysis of AIDS-related primary effusion lymphoma (PEL) suggests a plasmablastic derivation and identifies PEL-specific transcripts

AbstractAIDS-related primary effusion lymphoma (PEL) is an HIV-associated malignancy characterized by the ability of the tumor cells to specifically home in the serous body cavities. Here we used gene expression profile analysis (about 12 000 genes) to further define the phenotype of PEL and to investigate the lymphoma relationship to normal B cells and to other tumor subtypes, including non-Hodgkin lymphomas (NHLs) of immunocompetent hosts and AIDS-associated NHL (AIDS-NHL). The results showed that PEL displayed a common gene expression profile that is clearly distinct from all NHLs of immunocompetent hosts and AIDS-NHL subtypes and, in contrast to those, is not related to germinal center (GC) or memory B cells. The gene expression profile of PEL was defined as plasmablastic because it showed features of both immunoblasts identified by Epstein-Barr virus (EBV)–transformed lymphoblastoid cell lines and AIDS immunoblastic lymphoma, and plasma cells, as defined by multiple myeloma cell lines. Finally, our results identify a set of genes specifically expressed in PEL tumor cells. Their expression was validated at the protein level, suggesting their potential pathogenetic and clinical significance.

Patterns of Gene Expression and a Transactivation Function Exhibited by the vGCR (ORF74) Chemokine Receptor Protein of Kaposi's Sarcoma-Associated Herpesvirus

The ORF74 or vGCR gene encoded by Kaposi's sarcoma-associated herpesvirus (KSHV; also called human herpesvirus 8) has properties of a ligand-independent membrane receptor signaling protein with angiogenic properties that is predicted to play a key role in the biology of the virus. We have examined the expression of vGCR mRNA and protein in primary effusion lymphoma (PEL) cell lines, PEL and multicentric Castleman's disease (MCD) tumors, Kaposi's sarcoma lesions and infected endothelial cell cultures. The vGCR gene proved to be expressed in PEL cell lines as a large spliced bicistronic mRNA of 3.2 kb that also encompasses the upstream vOX2 (K14) gene. This mRNA species was induced strongly by phorbol ester (TPA) and sodium butyrate treatment in the BCBL-1 cell line, but only weakly in the HBL6 cell line, and was classified as a relatively late and low-abundance delayed early class lytic cycle gene product. A complex bipartite upstream lytic cycle promoter for this mRNA was nestled within the intron of the 5'-overlapping but oppositely oriented latent-state transcription unit for LANA1/vCYC-D/vFLIP and responded strongly to both TPA induction and cotransfection with the KSHV RNA transactivator protein (RTA or ORF50) in transient reporter gene assays. A vGCR protein product of 45 kDa that readily dimerized was detected by Western blotting and in vitro translation and was localized in a cytoplasmic and membrane pattern in DNA-transfected Vero and 293T cells or adenovirus vGCR-transduced dermal microvascular endothelial cells (DMVEC) as detected by indirect immunofluorescence assay (IFA) and immunohistochemistry with a specific rabbit anti-vGCR antibody. Similarly, a subfraction of KSHV-positive cultured PEL cells and of KSHV (JSC-1) persistently infected DMVEC cells displayed cytoplasmic vGCR protein expression, but only after TPA or spontaneous lytic cycle induction, respectively. The vGCR protein was also detectable by immunohistochemical staining in a small fraction (0.5 to 3%) of the cells in PEL and MCD tumor and nodular Kaposi's sarcoma lesion specimens that were apparently undergoing lytic cycle expression. These properties are difficult to reconcile with the vGCR protein's playing a direct role in spindle cell proliferation, transformation, or latency, but could be compatible with proposed contributions to angiogenesis via downstream paracrine effects. The ability of vGCR to transactivate expression of both several KSHV promoter-driven luciferase (LUC) reporter genes and an NFkappaB motif containing the chloramphenicol acetyltransferase (CAT) reporter gene may also suggest an unexpected regulatory role in viral gene expression.

Monoclonality or oligoclonality of human herpesvirus 8 terminal repeat sequences in Kaposi's sarcoma and other diseases.

Infection with human herpesvirus 8 (HHV8), also termed Kaposi's sarcoma (KS)-associated herpesvirus, is associated with all forms of KS, with primary effusion lymphoma (PEL), and with some forms of multicentric Castleman's disease (MCD), but the pathogenic role of HHV8 in these tumors and the clonal nature of KS are still unclear. The purpose of this study was to examine whether the number of terminal repeats (TRs) contained in the fused TR region of HHV8 could be used as a marker of clonality in HHV8-associated tumors. Pulsed-field gel electrophoresis (PFGE) and multiple-probe Southern blot analysis of the HHV8 TR region were performed on high-molecular-weight DNA obtained from tumoral KS, PEL, and MCD lesions. These analysis showed that the fused TR region contains a large but variable number of TR units (ranging from 16 to 75) and that the viral genome is present as extrachromosomal circular DNA in these tumors in vivo, with occasional ladders of heterogeneous linear termini reflecting lytic replication. All PEL tumors and PEL-derived cell lines as well as some KS tumors contained monoclonal or oligoclonal fused TR fragments; however, the TR region appeared polyclonal in MCD tumors and in a few KS lesions. Several KS and PEL lesions are monoclonal expansions of a single infected cell, suggesting that HHV8 infection precedes tumor growth and thus supporting an etiologic role of latent HHV8 in these proliferations. Our finding that nodular KS lesions display all possible patterns of clonality supports the model according to which KS begins as a polyclonal disease with subsequent evolution to a monoclonal process.