Epstein-Barr virus infectious particles initiate B cell transformation and modulate cytokine response.

IMPORTANCE: The Epstein-Barr virus efficiently infects and transforms B lymphocytes. During this process, infectious viral particles transport the viral genome to the nucleus of target cells. We show here that these complex viral structures serve additional crucial roles by activating transcription of the transforming genes encoded by the virus. We show that components of the infectious particle sequentially activate proinflammatory B lymphocyte signaling pathways that, in turn, activate viral gene expression but also cause cytokine release. However, virus infection activates expression of ZFP36L1, an RNA-binding stress protein that limits the length and the intensity of the cytokine response. Thus, the infectious particles can activate viral gene expression and initiate cellular transformation at the price of a limited immune response.

The Epstein-Barr virus noncoding RNA EBER2 transactivates the UCHL1 deubiquitinase to accelerate cell growth.

The Epstein-Barr virus (EBV) transforms resting B cells and is involved in the development of B cell lymphomas. We report here that the viral noncoding RNA EBER2 accelerates B cell growth by potentiating expression of the UCHL1 deubiquitinase that itself increased expression of the Aurora kinases and of cyclin B1. Importantly, this effect was also visible in Burkitt's lymphoma cells that express none of the virus's known oncogenes. Mechanistically, EBER2 bound the UCHL1 messenger RNA (mRNA), thereby bringing a protein complex that includes PU.1, a UCHL1 transactivator, to the vicinity of its promoter. Although the EBV oncogene LMP1 has been suggested to induce UCHL1, we show here that EBER2 plays a much more important role to reach significant levels of the deubiquitinase in infected cells. However, some viruses that carried a polymorphic LMP1 had an increased ability to achieve full UCHL1 expression. This work identifies a direct cellular target of a viral noncoding RNA that is likely to be central to EBV's oncogenic properties.

Epstein-Barr virus ncRNA from a nasopharyngeal carcinoma induces an inflammatory response that promotes virus production.

The Epstein-Barr virus M81 strain, isolated from a nasopharyngeal carcinoma, induces potent spontaneous virus production in infected B cells. We found that the M81 non-coding Epstein-Barr-encoded RNA EBER2, which carries polymorphisms that are mainly restricted to viruses found in endemic nasopharyngeal carcinomas, markedly stimulated this process. M81 EBER2 increased CXCL8 expression, and this chemokine enhanced spontaneous lytic replication levels in M81-infected B cells. Both events resulted from the endocytosis of extracellular vesicles containing EBER2 that were generated by neighbouring M81-infected B cells, thereby generating a paracrine loop. These effects were strictly dependent on a functional Toll-like receptor 7 (TLR7), a sensor of single-stranded RNA located in the endosome of these cells. These unique properties of M81 EBER2 could be ascribed to its unusually high expression level and to the ability of its single-stranded region to activate TLR7; both of these properties were dependent on M81-specific polymorphisms. Thus, M81 induced chronic inflammation in its target cells and this resulted in increased virus production. These observations provide a mechanistic molecular link between M81 virus replication-a central viral function and a cancer risk factor-and the production of a chemokine involved in inflammation and carcinogenesis.

Multiple myeloma-derived Jagged ligands increases autocrine and paracrine interleukin-6 expression in bone marrow niche.

Multiple myeloma cell growth relies on intrinsic aggressiveness, due to a high karyotypic instability, or on the support from bone marrow (BM) niche.We and other groups have provided evidences that Notch signaling is related to tumor cell growth, pharmacological resistance, localization/recirculation in the BM and bone disease.This study indicates that high gene expression levels of Notch signaling members (JAG1, NOTCH2, HES5 and HES6) correlate with malignant progression or high-risk disease, and Notch signaling may participate in myeloma progression by increasing the BM levels of interleukin-6 (IL-6), a major player in myeloma cell growth and survival. Indeed, in vitro results, confirmed by correlation analysis on gene expression profiles of myeloma patients and immunohistochemical studies, demonstrated that Notch signaling controls IL-6 gene expression in those myeloma cells capable of IL-6 autonomous production as well as in surrounding BM stromal cells. In both cases Notch signaling activation may be triggered by myeloma cell-derived Jagged ligands. The evidence that Notch signaling positively controls IL-6 in the myeloma-associated BM makes this pathway a key mediator of tumor-directed reprogramming of the bone niche.This work strengthens the rationale for a novel Notch-directed therapy in multiple myeloma based on the inhibition of Jagged ligands.