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The influence of highly recurrent EBV reactivation on genetic copy number alterations

ABSTRACT: We proposed that the frequency of EBV reactivation may be crucial for its pathogenic role and highly recurrent EBV reactivations exert a profound influence on genome instability. Recurrent reactivations were induced in the EBV-latently infected NPC cells (NA cells) by treating with 12-o-tetradecanoylphorbol-13-acetate (TPA) and sodium n-butyrate (SB) once per passage periodically. Genome-wild oligoarray-based comparative genomic hybridization (CGH) technology was applied to investigate the copy-number aberrations in response for different frequencies of EBV reactivation. The results showed that the NR15 cells, NA cells with the highest frequency (15 times) of reactivation, exhibit extensive genomic copy-number alterations (CNAs) mostly involving chromosome 3p, 3q, 8p, 8q, 9p and 9q, whereas limited number of CNAs were observed both in NR1 cells where only the initial reactivation take place and NP15 cells which were culture in parallel with NR15 cells without EBV-reactivation. We concluded that it is the highly recurrent reactivations of EBV, but neither just a primary reactivation nor EBV-latent infection, may intimately involve in carcinogenesis of nasopharyngeal epithelial cells with the progressive genome instabilities and the accumulation of genetic mutations. Keywords: array-based comparative genomic hybridization, reactivation of EBV, incidence, frequency, recurrent, genome instability, copy-number alterations, carcinogenesis, and nasopharyngeal carcinoma (NPC).

ORGANISM(S): Homo sapiens

PROVIDER: GSE6472 | GEO | 2007/05/30

SECONDARY ACCESSION(S): PRJNA98707

REPOSITORIES: GEO

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Project description:We proposed that the frequency of EBV reactivation may be crucial for its pathogenic role and highly recurrent EBV reactivations exert a profound influence on genome instability. Recurrent reactivations were induced in the EBV-latently infected NPC cells (NA cells) by treating with 12-o-tetradecanoylphorbol-13-acetate (TPA) and sodium n-butyrate (SB) once per passage periodically. Genome-wild oligoarray-based comparative genomic hybridization (CGH) technology was applied to investigate the copy-number aberrations in response for different frequencies of EBV reactivation. The results showed that the NR15 cells, NA cells with the highest frequency (15 times) of reactivation, exhibit extensive genomic copy-number alterations (CNAs) mostly involving chromosome 3p, 3q, 8p, 8q, 9p and 9q, whereas limited number of CNAs were observed both in NR1 cells where only the initial reactivation take place and NP15 cells which were culture in parallel with NR15 cells without EBV-reactivation. We concluded that it is the highly recurrent reactivations of EBV, but neither just a primary reactivation nor EBV-latent infection, may intimately involve in carcinogenesis of nasopharyngeal epithelial cells with the progressive genome instabilities and the accumulation of genetic mutations. Experiment Overall Design: Samples of four sources were analyzed. The NP1 cells denoted the EBV-latently infected nasopharyngeal carcinoma cell lines, NA cells, with low-passage-number and mock-treated. The NR1 denoted the NA cells harboring one time of EBV reactivation. The NR15 cells denoted the NA cells harboring fifteen times of EBV reactivation. The NP15 cells denoted the NA cells cultured in parallel with NR15 (experienced 15 times of passages) without EBV-reactivation. Genomic DNAs extracted from NP15, NR1 and NR15 cells were used as experimental samples and subjected to Cy5-labeling reactions. Genomic DNAs extracted from NP1 cells were used as the common reference samples subjected to Cy3-labeling reactions. All three experiments were verified by dye-swap design where the targets labeling conditions were exchanged, NP1 labeled with Cy5, and NP15, NR1 or NR15 labeled with Cy3.

Project description:Seroepidemiological studies imply a correlation between Epstein-Barr virus (EBV) reactivation and the development of nasopharyngeal carcinoma (NPC). Phorbol esters, butyrates and N-nitroso compounds are known chemical carcinogens in foodstuffs and cigarettes that have been implicated as risk factors contributing to the development of NPC. We have demonstrated previously that low dose N-methyl-N'-nitro-N-nitrosoguanidine (MNNG, 0.1 microg/ml) had a synergistic effect with 12-O-tetradecanoylphorbol-13-acetate (TPA) and sodium butyrate (SB) in enhancing EBV reactivation (Chem Biol Interact 188: 623-634). Since residents of areas with a high risk of NPC are reported to contact with these carcinogens (TPA, SB or nitrosamines) frequently, we sought to determine the consequence of repeated exposure of EBV-harboring nasopharyngeal cells to these carcinogens in a long-term, low dose, repeated manner. An NPC cell line latently infected with EBV, NA, was periodically treated with TPA/SB combined with MNNG for recurrent EBV reactivation. After 10 times of chemically-induced recurrent reactivation of EBV, the expression profile analysis indicates that many carcinogenesis-related genes were altered in recurrent reactivated NA cells when compared to the parental NA cells. The expression profile was analyzed in the recurrent EBV reactivated NA cells and the parental NA cells. The expression profile of two NA cells, NA-P10/TS-MG and NA-P1/mock, were analyzed in this study. NA-P10/TS-MG cells were subject to 10 times of repeated chemical exposure by incubating these cells periodically with TPA/SB (10 ng/ml and 1.0 mM) in combination with MNNG (0.1 microg/ml). The NA cells at the beginning of this experiment were defined as passage 0 (P0) cells. 24 h after seeding, the cells were subjected to a 24 h period of mock or chemical treatment. After this 24 hr treatment, the cells were recovered by replacing the medium with fresh (treatment-free) medium and incubation for a further 48 h. The resulting cells were defined as passage 1 (P1) cells. Cells from P1 were trypsinized and transferred and the process repeated again to obtain the P2 cells. A total of ten treatments were applied to the cells in this study. M-bM-^@M-^\NA-P10/TS-MGM-bM-^@M-^] refers to NA cells with 10 times of combined TPA/SB and MNNG (TS-MG) treatments. NA-P1/mock is mock-treated NA cells with one time of passage that was used as reference in this study. Replicates were included for each samples.

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The influence of highly recurrent EBV reactivation on genetic copy number alterations

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