Oxidative stress enables Epstein–Barr virus-induced B-cell transformation by posttranscriptional regulation of viral and cellular growth-promoting factors

Abstract

Infection of human B lymphocytes by Epstein-Barr virus (EBV) leads to the establishment of immortalized lymphoblastoid cell lines (LCLs) that are widely used as a model of viral oncogenesis. An early consequence of infection is the induction of DNA damage and activation of the DNA damage response, which limits the efficiency of growth transformation. The cause of the DNA damage remains poorly understood. We have addressed this question by comparing the response of B lymphocytes infected with EBV or stimulated with a potent B-cell mitogen. We found that although the two stimuli induce comparable proliferation during the first 10 days of culture, the EBV-infected blasts showed significantly higher levels of DNA damage, which correlated with stronger and sustained accumulation of reactive oxygen species (ROS). Treatment with ROS scavengers decreased DNA damage in both mitogen-stimulated and EBV-infected cells. However, while mitogen-induced proliferation was slightly improved, the proliferation of EBV-infected cells and the establishment of LCLs were severely impaired. Quenching of ROS did not affect the kinetics and magnitude of viral gene expression but was associated with selective downregulation of the viral LMP1 and phosphorylated cellular transcription factor STAT3 that have key roles in transformation. Analysis of the mechanism by which high levels of ROS support LMP1 expression revealed selective inhibition of viral microRNAs that target the LMP1 transcript. Our study provides novel insights into the role of EBV-induced oxidative stress in promoting B-cell immortalization and malignant transformation.

Limited nucleotide pools restrict Epstein–Barr virus-mediated B-cell immortalization

“…21 Others have found that these cells also display elevated reactive oxygen species and telomere dysfunction that may induce ATM pathway activation. 19, 26, 27 Early-infected cells also display aberrant karyotypes, but as infected cells grow out over a period of weeks into LCLs the DNA damage signaling wanes and these cells display stable karyotypes. 28 …”

DNA Oncogenic Virus‐Induced Oxidative Stress, Genomic Damage, and Aberrant Epigenetic Alterations

“…EBV latency genes play an important role in gastric cancer by independently promoting genomic instability that triggers DNA damage by abnormally regulating cell cycle machinery and DNA repair of infected cells. Exposure of EBV-infected cells correlates with increased DNA damage induced by ROS-induced NOX and NADPH oxidase [138]. Several studies demonstrated that oxidative stress facilitates EBV-induced B-cell transformation through posttranscriptional regulation of viral ( LMP1 ) and host ( STAT3 ) genes, which are critical for promoting B-cell immortalisation, malignant transformation, and tumorigenesis [132, 138, 139].…”

“…Exposure of EBV-infected cells correlates with increased DNA damage induced by ROS-induced NOX and NADPH oxidase [138]. Several studies demonstrated that oxidative stress facilitates EBV-induced B-cell transformation through posttranscriptional regulation of viral ( LMP1 ) and host ( STAT3 ) genes, which are critical for promoting B-cell immortalisation, malignant transformation, and tumorigenesis [132, 138, 139]. IFI16 inflammasome with adaptor ASC protein was shown to be activated upon sensing of latent EBV infection in all types of latency, and this leads to induction of IL-1 β , IL-18, and IL-33 maturation [140].…”

“…Although EBV is not integrated into host genome, its materials such as EBNA1 and BZLF1 seem to interact with various cellular promoters and induce epigenetic alterations. Epigenetic regulation of viral and host cellular growth-promoting factors such as EBNA1, BZLF1, STAT3, XIAP-associated factor 1 (XAF1), and DNA inducible factor 45 alpha (GADD45 α ) induces oxidative stress and expedites EBV-induced B-cell transformation [132, 138, 139, 144]. EBV-induced elevated level of ROS promotes excessive production of receptor activator of NF- κ B ligand (RANKL) that interacts with RANK receptor in the periapical area leading to bone resorption and apical periodontitis [145].…”

Effect of mitochondrially targeted carboxy proxyl nitroxide on Akt-mediated survival in Daudi cells: Significance of a dual mode of action

“…The immortalization of normal B-cells into the Daudi cell line involves the cellular transformation termed Latency III [ 2,3 ]. This is mediated by EBV proteins, including five nuclear proteins (EBNA-1, -2, -3, -5, and -6) and one latent membrane protein (LMP-1) [ 4,5 ]. For example, Epstein-Barr nuclear antigen 1 (EBNA 1), a regularly detected protein of all EBV-associated malignancies, transcriptionally activates the expression of nicotinamide adenine dinucleotide phosphate-oxidase (NADPH) oxidase 2 (NOX2), a key generator of reactive oxygen species (ROS) that is elevated under Latency III [ 6,7 ].…”