Study On Methylation Of The Epstein-Barr Virus Latent Gene Promoters In Gastric Carcinoma And Nasopharyngeal Carcinoma

Epstein-Barr virus (EBV) is an important DNA virus of the y-herpesvirus family, which has a close relationship with many kinds of human malignant tumor. The restricted expression of EBV genes showed in EBV-associated gastric carcinoma (EBVaGC) and EBV positive nasopharyngeal carcinoma (NPC) tissues, may be associated with the epigenetic regulation of EBV gene promoters, in particular DNA methylation. As studies shown, EBV latent gene promoters are hypermethylated in EBV positive tumors; methylation of the regulatory region can block the activity of these promoters and inhibit the expression of the corresponding EBV gene. The transcriptional regulation of EBV genes plays a profound role in allowing the virus to persist for the lifetime of the host in the face of a potent immune response against the proteins it encodes. So targeting epigenetic changes in EBV genome will likely represent a new method in EBV positive tumor treatment.Objective To study and analyze the methylation status of EBV latent gene promoters in EBVaGCs and EBV positive NPC..Methods In our study,32 EBVaGCs and 20 NPCs were selected as research objects, and EBV positive cell lines(Raji, B95-8and Akata) were selected as experimental control. We systematically examine the methylation status of specific CpG sites within the regulation region of Cp, Wp, Qp, LMP1 and LMP2A promoters in tumor specimens and cell lines by a combination of bisulfite genomic sequencing (BGS) and methylation-specific PCR (MSP).Results①Our experiment results of the methylation status of EBV latent gene promoters in EBV postive cell lines (B95-8, Raji and Akata) were in line with previous studies:Cp was unmethylated in B95-8 cell line, hypermetylated in Raji cell line, but partially methylated in Akata cell line; Wp was hypermethylated in Raji and Akata cell lines, but partially methylated in B95-8 cell line; Qp, LMPlp and LMP2Ap were unmethylated in the three cell lines.②The methylation status of these promoters was consistent with different latency types of EBVaGC and NPC:Wp and Cp was methylated, whereas EBNA 1 transcripts were initiated at the unmethylated Qp.③Methylation patterns of LMPlp and LMP2Ap were different:the methyl ation rates of LMP1p and LMp2Ap in EBVaGC were significantly higher than those in NPC (LMP1:χ2=19.1462, P<0.0001; LMP2A:χ2=11.0139, P=0.0009).Conclusion The methylation status of EBV latent gene promoters in EBVaGC and NPC is different, methylation is one of important mechanisms in regularing the activity of EBV latent gene promoters.