Evidence for a Mesothelial Origin of Body Cavity Effusion Lymphomas.
ABSTRACT: Primary effusion lymphoma (PEL) is a Kaposi's sarcoma herpes virus (KSHV)-induced lymphoma that typically arises in body cavities of HIV-infected patients. PEL cells are often co-infected with Epstein-Barr virus (EBV). "PEL-like" lymphoma is a KSHV-unrelated lymphoma that arises in body cavities of HIV-negative patients. "PEL-like" lymphoma is sometimes EBV positive. The derivation of PEL/"PEL-like" cells is unclear.Mesothelial cells were cultured from body cavity effusions of 23 patients. Cell proliferation, cytokine secretion, marker phenotypes, KSHV/EBV infection, and clonality were evaluated by standard methods. Gene expression was measured by quantitative polymerase chain reaction and immunoblotting. A mouse model of PEL (3 mice/group) was used to evaluate tumorigenicity.We found that the mesothelia derived from six effusions of HIV-infected patients with PEL or other KSHV-associated diseases contained rare KSHV + or EBV + mesothelial cells. After extended culture (16-17 weeks), some mesothelial cells underwent a trans-differentiation process, generating lymphoid-type CD45 + /B220 + , CD5 + , CD27 + , CD43 + , CD11c + , and CD3 - cells resembling "B1-cells," most commonly found in mouse body cavities. These "B1-like" cells were short lived. However, long-term KSHV + EBV - and EBV + KSHV - clonal cell lines emerged from mesothelial cultures from two patients that were clonally distinct from the monoclonal or polyclonal B-cell populations found in the patients' original effusions.Mesothelial-to-lymphoid transformation is a newly identified in vitro process that generates "B1-like" cells and is associated with the emergence of long-lived KSHV or EBV-infected cell lines in KSHV-infected patients. These results identify mesothelial cultures as a source of PEL cells and lymphoid cells in humans.
Project description:The significance of inflammation in KSHV biology and tumorigenesis prompted us to examine the role of COX-2 in primary effusion lymphoma (PEL), an aggressive AIDS-linked KSHV-associated non-Hodgkin's lymphoma (NHL) using nimesulide, a well-known COX-2 specific NSAID. We demonstrate that (1) nimesulide is efficacious in inducing proliferation arrest in PEL (KSHV+/EBV-; BCBL-1 and BC-3, KSHV+/EBV+; JSC-1), EBV-infected (KSHV-/EBV+; Raji) and non-infected (KSHV-/EBV-; Akata, Loukes, Ramos, BJAB) high malignancy human Burkitt's lymphoma (BL) as well as KSHV-/EBV+ lymphoblastoid (LCL) cell lines; (2) nimesulide is selectively toxic to KSHV infected endothelial cells (TIVE-LTC) compared to TIVE and primary endothelial cells (HMVEC-d); (3) nimesulide reduced KSHV latent gene expression, disrupted p53-LANA-1 protein complexes, and activated the p53/p21 tumor-suppressor pathway; (4) COX-2 inhibition down-regulated cell survival kinases (p-Akt and p-GSK-3?), an angiogenic factor (VEGF-C), PEL defining genes (syndecan-1, aquaporin-3, and vitamin-D3 receptor) and cell cycle proteins such as cyclins E/A and cdc25C; (5) nimesulide induced sustained cell death and G1 arrest in BCBL-1 cells; (6) nimesulide substantially reduced the colony forming capacity of BCBL-1 cells. Overall, our studies provide a comprehensive molecular framework linking COX-2 with PEL pathogenesis and identify the chemotherapeutic potential of nimesulide in treating PEL.
Project description:Primary effusion lymphoma (PEL) is a B cell lymphoma that is always associated with Kaposi's sarcoma-associated herpesvirus (KSHV) and in many cases also with Epstein-Barr virus (EBV); however, the requirement for EBV coinfection is not clear. Here, we demonstrate that adding exogenous EBV to KSHV+ single-positive PEL leads to increased KSHV genome maintenance and KSHV latency-associated nuclear antigen (LANA) expression. To show that EBV was necessary for naturally coinfected PEL, we nucleofected KSHV+/EBV+ PEL cell lines with an EBV-specific CRISPR/Cas9 plasmid to delete EBV and observed a dramatic decrease in cell viability, KSHV genome copy number, and LANA expression. This phenotype was reversed by expressing Epstein-Barr nuclear antigen 1 (EBNA-1) in trans, even though EBNA-1 and LANA do not colocalize in infected cells. This work reveals that EBV EBNA-1 plays an essential role in the pathogenesis of PEL by increasing KSHV viral load and LANA expression.
Project description:Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiologic agent of primary effusion lymphoma (PEL). All PEL cell lines are infected with KSHV, and 70% are coinfected with Epstein-Barr virus (EBV). KSHV reactivation from latency requires promoter-specific transactivation by the KSHV Rta protein through interactions with RBP-Jk (CSL), the cellular DNA-binding component of the Notch signal transduction pathway. EBV transformation of primary B cells requires EBV nuclear antigen 2 (EBNA-2) to interact with RBP-Jk to direct the latent viral and cellular gene expression program. Although KSHV Rta and EBV EBNA-2 both require RBP-Jk for transactivation, previous studies have suggested that RBP-Jk-dependent transactivators do not function identically. We have found that the EBV latent protein LMP-1 is expressed in less than 5% of KSHV(+)/EBV(+) PEL cells but is induced in an Rta-dependent fashion when KSHV reactivates. KSHV Rta transactivates the EBV latency promoters in an RBP-Jk-dependent fashion and forms a ternary complex with RBP-Jk on the promoters. In B cells that are conditionally transformed by EBV alone, we show that KSHV Rta complements a short-term EBNA-2 growth deficiency in an autocrine/paracrine manner. Complementation of EBNA-2 deficiency by Rta depends on RBP-Jk and LMP-1, and Rta transactivation is required for optimal growth of KSHV(+)/EBV(+) PEL lines. Our data suggest that Rta can contribute to EBV-driven cellular growth by transactivating RBP-Jk-dependent EBV latency genes. However, our data also suggest that EBNA-2 and Rta induce distinct alterations in the cellular proteomes that contribute to the growth of infected cells.
Project description:During de novo infection of human dermal microvascular endothelial cells (HMVEC-d), Kaposi's sarcoma-associated herpesvirus (KSHV) induced the multifunctional angiogenin (ANG) protein, which entered the nuclei and nucleoli of infected cells and stimulated 45S rRNA gene transcription, proliferation, and tube formation, which were inhibited by blocking ANG nuclear translocation with the antibiotic neomycin (S. Sadagopan et al., J. Virol. 83:3342-3364, 2009). ANG was induced by KSHV latency protein LANA-1 (open reading frame 73 [ORF73]). Here we examined the presence and functions of ANG in KSHV-positive (KSHV(+)) primary effusion lymphoma (PEL/BCBL) cells. Significant ANG gene expression and secretion were observed in KSHV(+) (BCBL-1 and BC-3) and KSHV(+) and Epstein-Barr virus-positive (KSHV(+) EBV(+)) (JSC-1) PEL cells and in BJAB-KSHV cells but not in EBV(-) KSHV(-) lymphoma cells (Akata, Loukes, Ramos, and BJAB), EBV(+) lymphoma cells (Akata-EBV and Raji), and cells from an EBV(+) lymphoblastoid cell line, thus suggesting a specific association of ANG in KSHV biology. Inhibition of nuclear translocation of ANG resulted in reduced BCBL-1 and TIVE-LTC (latently infected endothelial) cell survival and proliferation, while EBV(-) and EBV(+) Akata cells were unaffected. Blocking nuclear transport of ANG inhibited latent ORF73 gene expression and increased lytic switch ORF50 gene expression, both during de novo infection and in latently infected cells. A greater quantity of infectious KSHV was detected in the supernatants of neomycin-treated BCBL-1 cells than 12-O-tetradecanoylphorbol-13-acetate (TPA)-treated cells. Neomycin treatment and ANG silencing inhibited phospholipase C? (PLC-?) and AKT phosphorylation, and in contrast, ANG induced ORF73 expression and PLC-? and AKT phosphorylation. Further studies provided evidence that blockage of PLC-? activation by neomycin appears to be mediating the inhibition of latent gene expression, since treatment with the conventional PLC-? inhibitor U73122 also showed similar results. Silencing of ANG also resulted in reduced cell survival, reduced ORF73 gene expression, and lytic gene activation in BCBL-1 and TIVE-LTC cells and during de novo infection. Taken together, these studies suggest that KSHV has evolved to exploit ANG for its advantage via a so-far-unexplored PLC-? pathway for maintaining its latency.
Project description:The peculiar localization of body cavity lymphomas implies a specific contribution of the intracavitary microenvironment to the pathogenesis of these tumors. In this study, primary effusion lymphoma (PEL) was used as a model of body cavity lymphoma to investigate the role of mesothelial cells, which line the serous cavities, in lymphoma progression. The crosstalk between mesothelial and lymphomatous cells was studied in cocultures of primary human mesothelial cells (HMC) with PEL cells and a xenograft mouse model of peritoneal PEL. PEL cells were found to induce type 2 epithelial-mesenchymal transition (EMT) in HMC, which converted into a myofibroblastic phenotype characterized by loss of epithelial markers (pan cytokeratin and E-cadherin), expression of EMT-associated transcriptional repressors (Snail1, Slug, Zeb1, Sip1), and acquisition of ?-smooth muscle actin (?-SMA), a mesenchymal protein. A progressive thickening of serosal membranes was observed in vivo, accompanied by loss of cytokeratin staining and appearance of ?-SMA-expressing cells, confirming that fibrosis occurred during intracavitary PEL development. On the other hand, HMC were found to modulate PEL cell turnover in vitro, increasing their resistance to apoptosis and proliferation. This supportive activity on PEL cells was retained after transdifferentiation, and was impaired by interferon-?2 b treatment. On the whole, our results indicate that PEL cells induce type 2 EMT in HMC, which support PEL cell growth and survival, providing a milieu favorable to lymphoma progression. Our findings provide new clues into the mechanisms involved in lymphoma progression and may indicate new targets for effective treatment of malignant effusions growing in body cavities.
Project description:Primary effusion lymphoma (PEL) is an incurable malignancy that develops in immunodeficient patients as a consequence of latent infection of B-cells with Kaposi's sarcoma-associated herpes virus (KSHV). Malignant growth of KSHV-infected B cells requires the activity of the transcription factor nuclear factor (NF)-?B, which controls maintenance of viral latency and suppression of the viral lytic program. Here we show that the KSHV proteins K13 and K15 promote NF-?B activation via the protease mucosa-associated lymphoid tissue lymphoma translocation protein-1 (MALT1), a key driver of NF-?B activation in lymphocytes. Inhibition of the MALT1 protease activity induced a switch from the latent to the lytic stage of viral infection, and led to reduced growth and survival of PEL cell lines in vitro and in a xenograft model. These results demonstrate a key role for the proteolytic activity of MALT1 in PEL, and provide a rationale for the pharmacological targeting of MALT1 in PEL therapy.
Project description:Analyze possible changes in the transcriptome of host cell line infected with a recombinant EBV virus. The recombinant virus is an Akata cell-derived NeoR EBV strain, previously used in PMID: 12969959 Overall design: 6 samples analyzed. Parental KSHV-infected Primary effusion lymphoma (PEL) cell lines or KSHV and EBV-infected PEL cells.
Project description:The majority of AIDS-associated primary effusion lymphomas (PEL) are latently infected with both Kaposi's sarcoma-associated herpesvirus (KSHV) and Epstein-Barr virus (EBV). PELs harboring two viruses have higher oncogenic potential, suggesting functional interactions between EBV and KSHV. The KSHV replication and transcription activator (K-RTA) is necessary and sufficient for induction of KSHV lytic replication. EBV latent membrane protein 1 (LMP-1) is essential for EBV transformation and establishment of latency in vitro. We show EBV inhibits chemically induced KSHV lytic replication, in part because of a regulatory loop in which K-RTA induces EBV LMP-1 and LMP-1 in turn inhibits K-RTA expression and furthermore the lytic gene expression of KSHV. Suppression of LMP-1 expression in dually infected PEL cells enhances the expression of K-RTA and lytic replication of KSHV upon chemical induction. Because LMP-1 is known to inhibit EBV lytic replication, KSHV-mediated induction of LMP-1 would potentiate EBV latency. Moreover, KSHV infection of EBV latency cells induces LMP-1, and K-RTA is involved in the induction. Both LMP-1 and K-RTA are expressed during primary infection by EBV of KSHV latency cells. Our findings provide evidence that an interaction between EBV and KSHV at molecular levels promotes the maintenance and possibly establishment of viral latency, which may contribute to pathogenesis of PELs.
Project description:The human herpesviruses Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV) are associated with Hodgkin's lymphoma (HL) and Primary effusion lymphomas (PEL), respectively, which are B cell malignancies that originate from germinal center B cells. PEL cells but also a quarter of EBV-positive HL tumor cells do not express the genuine B cell receptor (BCR), a situation incompatible with survival of normal B cells. EBV encodes LMP2A, one of EBV's viral latent membrane proteins, which likely replaces the BCR's survival signaling in HL. Whether KSHV encodes a viral BCR mimic that contributes to oncogenesis is not known because an experimental model of KSHV-mediated B cell transformation is lacking. We addressed this uncertainty with mutant EBVs encoding the KSHV genes K1 or K15 in lieu of LMP2A and infected primary BCR-negative (BCR(-)) human B cells with them. We confirmed that the survival of BCR(-) B cells and their proliferation depended on an active LMP2A signal. Like LMP2A, the expression of K1 and K15 led to the survival of BCR(-) B cells prone to apoptosis, supported their proliferation, and regulated a similar set of cellular target genes. K1 and K15 encoded proteins appear to have noncomplementing, redundant functions in this model, but our findings suggest that both KSHV proteins can replace LMP2A's key activities contributing to the survival, activation and proliferation of BCR(-) PEL cells in vivo.Several herpesviruses encode oncogenes that are receptor-like proteins. Often, they are constitutively active providing important functions to the latently infected cells. LMP2A of Epstein-Barr virus (EBV) is such a receptor that mimics an activated B cell receptor, BCR. K1 and K15, related receptors of Kaposi's sarcoma-associated herpesvirus (KSHV) expressed in virus-associated tumors, have less obvious functions. We found in infection experiments that both viral receptors of KSHV can replace LMP2A and deliver functions similar to the endogenous BCR. K1, K15, and LMP2A also control the expression of a related set of cellular genes in primary human B cells, the target cells of EBV and KSHV. The observed phenotypes, as well as the known characteristics of these genes, argue for their contributions to cellular survival, B cell activation, and proliferation. Our findings provide one possible explanation for the tumorigenicity of KSHV, which poses a severe problem in immunocompromised patients.
Project description:Primary effusion lymphoma is a rare distinct large B-cell neoplasm that is associated with Kaposi's sarcoma-associated herpesvirus (KSHV) infection. Over recent years, 9 KSHV-positive/Epstein-Barr virus (EBV)-negative PEL cell lines have been established.Tumor cells were collected from the pleural effusion of a 49-year-old male with AIDS. Cells were grown in RPMI1640 culture medium supplemented with 10 % fetus bovine serum. Single cell cloning was performed successfully by a limiting dilution method in a 96-well plate. The cell line obtained was designated SPEL.SPEL cells showed gourd-shaped morphology with a polarized nucleus, expressing CD38, CD138, and Blimp-1, but not B cell markers such as CD19 and CD20. Polymerase chain reaction analysis revealed that SPEL cells were positive for KSHV but negative for EBV. Tetradecanoylphorbol acetate induced expression of KSHV lytic proteins and the production of KSHV particles in SPEL cells. Subcutaneous inoculation of SPEL cells into severe combined immunodeficiency mice resulted in the formation of solid tumors. Next-generation sequencing revealed the 138 kbp genome sequence of KSHV in SPEL cells. Suberic bishydroxamate, a histone deacetylase inhibitor, induced the expression of KSHV-encoded lytic proteins and cell death in SPEL cells.A new KSHV-positive and EBV-negative PEL cell line, SPEL was established. This cell line may contribute to furthering our understanding of the pathogenesis of PEL and KSHV infection.