The Synergistic Effect of Chemical Carcinogens Enhances Epstein-Barr Virus Reactivation and Tumor Progression of Nasopharyngeal Carcinoma Cells

Abstract

Seroepidemiological studies imply a correlation between Epstein-Barr virus (EBV) reactivation and the development of nasopharyngeal carcinoma (NPC). N-nitroso compounds, phorbols, and butyrates are chemicals found in food and herb samples collected from NPC high-risk areas. These chemicals have been reported to be risk factors contributing to the development of NPC, however, the underlying mechanism is not fully understood. We have demonstrated previously that low dose N-methyl-N’-nitro-N-nitrosoguanidine (MNNG, 0.1 µg/ml) had a synergistic effect with 12-O-tetradecanoylphorbol-13-acetate (TPA) and sodium butyrate (SB) in enhancing EBV reactivation and genome instability in NPC cells harboring EBV. Considering that residents in NPC high-risk areas may contact regularly with these chemical carcinogens, it is vital to elucidate the relation between chemicals and EBV and their contributions to the carcinogenesis of NPC. In this study, we constructed a cell culture model to show that genome instability, alterations of cancer hallmark gene expression, and tumorigenicity were increased after recurrent EBV reactivation in NPC cells following combined treatment of TPA/SB and MNNG. NPC cells latently infected with EBV, NA, and the corresponding EBV-negative cell, NPC-TW01, were periodically treated with MNNG, TPA/SB, or TPA/SB combined with MNNG. With chemically-induced recurrent reactivation of EBV, the degree of genome instability was significantly enhanced in NA cells treated with a combination of TPA/SB and MNNG than those treated individually. The Matrigel invasiveness, as well as the tumorigenicity in mouse, was also enhanced in NA cells after recurrent EBV reactivation. Expression profile analysis by microarray indicates that many carcinogenesis-related genes were altered after recurrent EBV reactivation, and several aberrations observed in cell lines correspond to alterations in NPC lesions. These results indicate that cooperation between chemical carcinogens can enhance the reactivation of EBV and, over recurrent reactivations, lead to alteration of cancer hallmark gene expression with resultant enhancement of tumorigenesis in NPC.

Pembrolizumab in Asia‐Pacific patients with advanced head and neck squamous cell carcinoma: Analyses from KEYNOTE‐012

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MiR‐17‐5p promotes cancer cell proliferation and tumorigenesis in nasopharyngeal carcinoma by targeting p21

“…NPC has the highest incidence rate in Southern China and Southeast Asia, represents a significant disease burden, and has an incidence of approximately 2/10,000 per year in endemic areas . Genetic susceptibility , EBV infection , and chemical carcinogens have been implicated in the pathogenesis of NPC. However, its pathogenesis is still not very clear.…”

A bacterial genotoxin causes virus reactivation and genomic instability in Epstein–Barr virus infected epithelial cells pointing to a role of co‐infection in viral oncogenesis

“…It has been speculated that the products of genes expressed during the productive cycle, including viral IL‐10 (vIL‐10) and cellular IL‐8, TGFβ, and VEGF, may establish a tumorigenic environment that sustains the proliferation of neighboring latently infected cells . In addition, viral proteins that cause DNA damage or interfere with the DDR may be expressed during abortive productive infection, as suggested by the finding that recurrent exposure to TPA/butyrate promoted the acquisition of chromosomal aberration and phenotypic properties of tumor progression in an EBV‐positive NPC cell line but not in the EBV‐negative parental cells . We have observed full reactivation of the productive virus cycle with expression immediate early, early, and late genes and presumably production of infectious virus following exposure of EBV positive epithelial cells to live Aa , bacterial culture supernatants or purified CDT.…”