Epstein-Barr virus small RNAs potentiate tumorigenicity of Burkitt lymphoma cells independently of an effect on apoptosis

The tumorigenic potential of the Burkitt lymphoma (BL) cell line Akata is dependent on the restricted latency program of Epstein-Barr virus (EBV) that is characteristically maintained in BL tumors. Within these cells, EBV-mediated inhibition of apoptosis correlates with an up-regulation of BCL-2 levels in concert with a down-regulation in c-MYC expression that occurs under growth-limiting conditions. Here we addressed whether EBV's effects on apoptosis and tumorigenicity are mediated by the EBV small RNAs EBER-1 and EBER-2. Stable expression of the EBERs in EBV-negative Akata BL cells, at levels comparable to those in EBV-positive cells, significantly enhanced the tumorigenic potential of EBV-negative BL cells in SCID mice, but did not fully restore tumorigenicity relative to EBV-positive Akata cells. Furthermore, wild-type or greater levels of EBER expression in EBV-negative Akata cells did not promote BL cell survival. These data therefore suggest that EBV can contribute to BL through at least two avenues: an EBER-dependent mechanism that enhances tumorigenic potential independent of a direct effect on apoptosis, and a second mechanism, mediated by an as-yet-unidentified EBV gene(s), that offsets the proapoptotic consequences of deregulated c-MYC in BL.     

Postinfectious glomerulonephritis and Epstein-barr virus co-infection

Contrary to group A beta-hemolytic streptococcus as the most common cause of postinfectious glomerulonephritis (PIGN), Epstein-Barr virus (EBV) is only occasionally associated with acute renal involvement. We describe an 11-year-old boy who presented with clinical signs of infective mononucleosis and acute glomerulonephritis characterized by edema, hypertension and dark colored urine with diminished renal function. Serology tests confirmed streptococcal infection and acute EBV infection. Persistently depressed C3 complement and gross hematuria indicated renal biopsy which shows PIGN-type picture and, in addition, acute interstitial nephritis, both conclusive of streptococcal infection. We performed tissue DNA extraction by polymerase chain reaction (PCR) and demonstrated EBV-DNA from the kidney specimen supporting EBV involvement in renal tissue. This is the first reported case of PIGN with serologically-proven streptococcal and simultaneously, acute EBV co-infection. EBV-DNA extraction supported the EBV involvement in renal tissue suggesting that both etiologic agents might have contributed to renal inflammation. Adding serology evaluation for EBV in cases with typical clinical signs of infective mononucleosis and renal symptoms, EBV might be more commonly associated with PIGN than is currently appreciated.     

Episomal and integrated copies of Epstein-Barr virus coexist in Burkitt lymphoma cell lines.

The Epstein-Barr virus genome is present in more than 95% of the African cases of Burkitt lymphoma. In this tumor, the viral genome is usually maintained in multiple episomal copies. Viral integration has been described only for Namalwa, a cell line lacking episomes. In this study, we have addressed the question of whether integrated and episomal copies can coexist in Burkitt lymphoma cells. Gel electrophoresis was used to demonstrate the presence of episomal as well as free linear DNA in three Burkitt lymphoma cell lines. The numbers of episomal copies per cell were estimated to be 5 to 10 in BL36 and BL137 cells and below 1 in BL60 cells, indicating that BL60 does not represent a homogeneous cell population. Fluorescence in situ hybridization was combined with chromosomal banding to study the association of the viral DNA with metaphase chromosomes. A symmetrical pattern of signals at both chromatids located at the same chromosomal sites in many if not all metaphases was taken as evidence for viral integration. In each of the three cell lines, one site of integration was identified: at chromosome 11p15 in BL36 cells, at chromosome 1p34 in BL137 cells, and at the site of a reciprocal t(11;19) translocation in BL60 cells. Integrated, episomal and linear copies of Epstein-Barr virus DNA thus coexist in Burkitt lymphoma cells. The biological significance of viral integration in Burkitt lymphoma cells remains to be elucidated.     

Epstein-barr virus (EBV)-associated antibodies in a case of Burkitt's lymphoma during 14 years of sustained remission

Summary A Burkitt's lymphoma (BL) patient who sustained remission for more than 14 years after chemotherapy was monitored by means of serial serum samplings. The sera were titrated for antibodies against the Epstein-Barr virus (EBV)-associated cell membrane antigen (MA), viral capsid antigens (VCA), early antigen complex (EA R/D), and nuclear antigen (EBNA), and also for reactivity in the antibody-dependent cellular cytotoxicity (ADCC) test. The initial serological profile corresponded to that of most BL patients with active disease. During remission, it changed to resemble that of normal persons with persistent, latent EBV infection, at least qualitatively. The prognostic and biological implications of the titer levels and their changes are discussed.Abbreviations ADCC antibody-dependent cellular cytotoxicity - BCG Bacillus Calmette-Guérin - BL Burkitt's lymphoma - D diffuse component of EA - EA Epstein-Barr virus-induced early antigens - EBNA Epstein-Barr virus-specific nuclear antigen - EBV Epstein-Barr virus - KCC Kenya Cancer Council Registry - MA EBV-associated cell membrane antigen complex - NK natural killer - R restricted component of EA - VCA EB viral capsid antigen complex     

Different activation of Epstein-Barr virus immediate-early and early genes in Burkitt lymphoma cells and lymphoblastoid cell lines.

Specific expression of the Epstein-Barr virus (EBV) immediate-early and early gene products Zta, Rta, I'ta, and MSta by a recombinant vaccinia virus system allowed us to analyze the first steps in the induction of the lytic cycle in EBV-infected Burkitt lymphoma (BL) cells and lymphoblastoid cell lines (LCLs). Significant differences in the induction of early genes were found between these cell types: whereas in BL cells the trans activator Zta was found to induce key steps of the early lytic cycle, only minor activities of Zta were noted in LCLs. Contrary to Zta, the trans activator Rta was found to be highly effective in LCLs. These observations suggest that Rta may play an important role in the activation of the early lytic cycle in LCLs, although it cannot be activated by Zta. The latter may be a reason for the lower tendency of LCLs to switch into the lytic cycle compared with BL cells or differentiated epithelial cells.     

Retracted: miR-150 might inhibit cell proliferation and promote cell apoptosis by targeting LMO4 in Burkitt lymphoma

This study aimed at investigating the effect of microRNA-150 (miR-150) on cell proliferation of Burkitt lymphoma and its molecular mechanism. Gene expression analysis was applied to identify target genes of miR-150 in Burkitt lymphoma cell line ST486 based on the dataset from the Gene Expression Omnibus (GEO) datasets GSE86432. miRNA mimics, inhibitor and small interfering RNA (siRNA) were fluorescently labeled by Cy3, whereas plasmid vector was labeled by EGFP. Cells were viewed by fluorescence microscope and transfection efficiency was evaluated through fluorescent cell percentage. Quantitative real-time polymerase chain reaction analysis (qRT-PCR) and western blot were applied to detect the expression level of miR-150 and LMO4. Cell proliferation, cell cycle, and apoptosis were explored by CCK-8, flow cytometry. Targeting relationship was validated by the Luciferase reporter assay. Tumor xenograft and immunohistochemical analysis were conducted in nude mice model. In Burkitt lymphoma cells, miR-150 expression was significantly lower than normal ones, whereas the expression of LMO4 was upregulated. miR-150 might inhibit cell proliferation and promoted apoptosis in Burkitt lymphoma deterioration by downregulating LMO4. The results of tumor xenograft further confirmed the role of miR-150 in Burkitt lymphoma. Targeting LMO4 is a significant mechanism by which miR-150 suppresses cell growth and promotes apoptosis in Burkitt lymphoma cells, thus may provide a novel target for Burkitt lymphoma therapy in the future.     

Cell softness regulates tumorigenicity and stemness of cancer cells

Identifying and sorting highly tumorigenic and metastatic tumor cells from a heterogeneous cell population is a daunting challenge. Here, we show that microfluidic devices can be used to sort marker‐based heterogeneous cancer stem cells (CSC) into mechanically stiff and soft subpopulations. The isolated soft tumor cells (< 400 Pa) but not the stiff ones (> 700 Pa) can form a tumor in immunocompetent mice with 100 cells per inoculation. Notably, only the soft, but not the stiff cells, isolated from CD133⁺, ALDH⁺, or side population CSCs, are able to form a tumor with only 100 cells in NOD‐SCID or immunocompetent mice. The Wnt signaling protein BCL9L is upregulated in soft tumor cells and regulates their stemness and tumorigenicity. Clinically, BCL9L expression is correlated with a worse prognosis. Our findings suggest that the intrinsic softness is a unique marker of highly tumorigenic and metastatic tumor cells.     

Epstein-barr virus latent membrane protein 1: Structure and functions

The Epstein-Barr virus latent membrane protein (LMP) 1 is a versatile protein that has profound effects on target cells through its effect on constitutive cellular proteins, e.g. TRAFs, TRADD, RIP, JAK3, BRAM1, and p85. LMP1 can stimulate or inhibit signaling pathways, resulting in transformation of rodent fibroblast cell lines, blockade of differentiation in epithelial cells, upregulation of anti-apoptotic proteins, production of cytokines, upregulation of cell surface markers, upregulation of DNA methyltransferase activity, and downregulation of cell adhesion molecules and cyclin-dependent kinases. Overall, this results in greater transformation and survival in LMP1-expressing cells. Within nasopharyngeal carcinoma biopsy tissues, a naturally occurring LMP1 variant has been identified as having a 10-amino acid deletion in the C-terminus that seems to confer greater transformation potential than non-deleted LMP1. The role of LMP1 as a viral oncogene and its interaction with cellular factors are discussed.     

Epstein-barr virus replication studies and their application to vector design

Vectors containing elements of the Epstein-Barr virus genome are used primarily to maintain cloned DNA inserts as plasmids in mammalian cells. However, Epstein-Bar-virus-based vectors have also been valuable tools in the hands of those studying the life cycle of Epstein-Barr virus. In this article, we discuss those characteristics of Epstein-Barr virus and its life cycle that have been used in vector construction and describe methods that are particularly applicable to the use of Epstein-Barr-virus-based vectors.     

Phosphoinositide phosphatase SHIP-1 regulates apoptosis induced by edelfosine, Fas ligation and DNA damage in mouse lymphoma cells

S49 mouse lymphoma cells undergo apoptosis in response to the ALP (alkyl-lysophospholipid) edelfosine (1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine), FasL (Fas ligand) and DNA damage. S49 cells made resistant to ALP (S49(AR)) are defective in sphingomyelin synthesis and ALP uptake, and also have acquired resistance to FasL and DNA damage. However, these cells can be re-sensitized following prolonged culturing in the absence of ALP. The resistant cells show sustained ERK (extracellular-signal-regulated kinase)/Akt activity, consistent with enhanced survival signalling. In search of a common mediator of the observed cross-resistance, we found that S49(AR) cells lacked the PtdIns(3,4,5)P(3) phosphatase SHIP-1 [SH2 (Src homology 2)-domain-containing inositol phosphatase 1], a known regulator of the Akt survival pathway. Re-sensitization of the S49(AR) cells restored SHIP-1 expression as well as phosphoinositide and sphingomyelin levels. Knockdown of SHIP-1 mimicked the S49(AR) phenotype in terms of apoptosis cross-resistance, sphingomyelin deficiency and altered phosphoinositide levels. Collectively, the results of the present study suggest that SHIP-1 collaborates with sphingomyelin synthase to regulate lymphoma cell death irrespective of the nature of the apoptotic stimulus.