EBV counteracts IL‐21‐induced apoptosis in an EBV‐positive diffuse large B‐cell lymphoma cell line

Abstract

Previously, interleukin (IL)-21 has been found to induce apoptosis by activating the signal transducer and activator of transcription 3 (STAT3) and concomitant upregulation of c-Myc in diffuse large B-cell lymphoma (DLBCL) lines with unknown Epstein-Barr virus (EBV) status. Here, as a first approach toward the characterization of the role of EBV in DLCBL, the EBV gene expression and the IL-21 sensitivity of the EBV-positive DLBCL line, Farage, have been examined. It was found that, surprisingly, despite c-Myc upregulation, IL-21 induced cell proliferation rather than apoptosis in Farage. Expression of a dominant-negative EBNA1 mutant and the consecutive downregulation of EBV gene expression antagonized the IL-21-induced proliferation of Farage and increased apoptosis. These findings reveal a previously unknown role of EBV in DLBCL that is of possible relevance for the current attempt to use IL-21 in therapy.Interleukin (IL)-21 was reported to induce apoptosis in diffuse large B-cell lymphoma (DLBCL) lines by activating the signal transducer and activator of transcription 3 (STAT3) and concomitant upregulation of c-Myc.1 This finding is of great interest in view of the potential use of IL-21 for DLBCL treatment.The potential usefulness of IL-21 in cancer therapy has been explored over the last few years.2-5 As a promising drug candidate in cancer therapy, IL-21 has been tested in Phase I and II clinical trials in metastatic melanoma, renal cell carcinoma (RCC) and non-Hodgkins' lymphoma (NHL). 2,6 DLBCLs are the most common group of malignant lymphomas that account for $30% of adult NHLs. They have a heterogeneous profile with defined subgroups that differ in their clinical course and response to therapy. 7,8 Epstein-Barr virus (EBV) is carried in almost all endemic Burkitt lymphomas and a variable proportion of other lymphoid malignancies.9,10 The expression pattern of the virus in latently infected lymphocytes is of three main types. Type I is characterized by the expression of EBNA1 only, Type II expresses EBNA1 and LMP1 and Type III expresses the full growth transformation program (EBNA1-6 and LMP1-2). 11About 10% of all DLBCLs carry EBV. 12 They occur mainly in elderly patients. Its prognosis is more unfavorable compared to the EBV-negative DLBCL. 13-18Although IL-21 has been suggested as a therapeutic agent for DLBCL, 1 the response of EBV1 and EBV2 DLBCLs has not been compared. IL-21 was found to induce apoptosis in nine DLBCL lines with unknown EBV status.1 In our study, we report that IL-21 induces cell proliferation rather than apoptosis in a DLBCL line, Farage, expressing a Type III EBV gene pattern. To investigate whether this behavior can be related to the presence of EBV, we have downregulated the viral gene expression with a tet-off dominantnegative EBNA1 (dnEBNA1) plasmid that can express dnEBNA1 conditionally. The EBV genome can be knocked out from the cells by inducing dnEBNA1 expression as the dnEBNA1 interrupts the viral episome maintenance function of EBNA1. 19 We show that the expression of ...

Epstein–Barr virus (EBV) provides survival factors to EBV+ diffuse large B‐cell lymphoma (DLBCL) lines and modulates cytokine induced specific chemotaxis in EBV+ DLBCL

“…Recently, IL‐21 was reported to induce apoptosis in DLBCL cell lines with unknown EBV carrier status through up‐regulation of c‐MYC . In a recent study, we found that EBV counteracts IL‐21‐induced apoptosis in Farage, indicating an important role of EBV in DLBCL . With the help of dnEBNA1, it was shown that EBV blocks apoptosis and induces proliferation in EBV‐positive BLs .…”

“…We have shown that IL‐21 stimulation of a type III DLBCL line (Farage) results in enhanced proliferation. When EBV genomes were eliminated, proliferation decreased and apoptosis increased …”

“…When EBV genomes were eliminated, proliferation decreased and apoptosis increased. 22 Chemokines play an important role in cell migration, inflammation, haematopoiesis and tumour growth. 23 The CXCR4-CXCL12 signalling pathway is involved in both tumour vasculature development and in the growth and metastatic spread of CXCR4-expressing tumours.…”

Effect of Interleukins on Antibody Production by Epstein-Barr Virus Transformed B Cells

“…(30) However, the survival in our set may have been promoted due to the presence of EBV transfection as was recently reported in EBV-positive diffuse large B-cell lymphoma cell line where EBV counteracts IL-21-induced apoptosis. (31) Our findings showed that of all the ILs added, singly or in combination, the blend of IL-2, IL-4, IL-6, and IL-21 induced the highest Ab production rates as well as the highest proliferation rates.…”

Does persistent HIV replication explain continued lymphoma incidence in the era of effective antiretroviral therapy?

“…Interestingly, Cubas et al demonstrated that Tfh from HIV-infected subjects displayed increased IL-21 production after ex vivo stimulation [22]. Given the well-documented effects of IL-21 on EBV latency and LMP1 expression [27-29], it is interesting to speculate that HIV-driven changes in Tfh function might enhance B cell transformation by EBV. Similarly, it was recently shown that expanded Tfh cell populations in individuals chronically infected with HIV are associated with an increase in germinal center B cells and plasma cells, decrease of memory B cells and IgG1 hypersecretion [30].…”