Polymorphism On EBERs Gene Of Epstein-Barr Virus In Nasopharyngeal Carcinomas And Healthy Donors From Guangdong

Background and Objective:Epstein-Barr virus(EBV)-encoded small RNAs(EBERs,EBER1 and EBER2)are the most highly expressed transcripts in all EBV-associated tumors and are involved in both lymphoid and epithelioid carcinogenesis.Our previous study on polymorphism of EBERs in isolates from EBV-associated tumors and healthy donors in Shandong area identified new EBER variants(EB-8m and EB-10m)which were less common but relatively more frequent nasopharyngeal carcinoma(NPC)cases than healthy donors.The purpose of this study is to characterize the variations of EBERs gene in NPC and healthy donors from Guangdong area,where NPC is endemic,and to explore the association of EBERs variation with NPC by comparison with the data from isolates in Shandong area and the data from sequenced EBV genomes from diseased and normal people from around the world.Methods:PCR and DNA sequencing were used to detect the sequences of the EBERs gene in isolates from NPC tissues and throat washing specimens of healthy donors in Guangdong as well as in isolates from new samples in Shandong.The sequences of EBERs gene in isolates and EBV genomes registered within GenBank were analyzed by Lasergene and MEGA software and classified according to the signature changes and the phylogenetic tree.The distributions of EBERs variants were compared between NPC and healthy donors and between different areas.The linkage between BamHI F polymorphism(F/f variant)and EBERs polymorphism was also analyzed.Results:(1)According to the phylogenetic tree,four EBER variants(EB-6m,EB-8m,EB-10m and B95-8)were identified.EB-6m was dominant in all population groups except for NPC group in Guandong,in which EB-8m was dominant.EB-8m was more common in NPC cases from Guangdong(82.0%,41/50)than NPC cases from Shandong(33.7%,32/95)(?2=30.590,P<0.0001),and it was also more frequent in healthy donors from endemic area(32.4%,24/74)than healthy donors from non-endemic area(1.1%,1/92)(?2=31.501,P<0.0001).More importantly,the EB-8m was more prevalent in NPC cases than healthy donors in both areas(Guangdong,?2=29.395,P<0.0001;Shandong,?2=34.173,P<0.0001).(2)The distribution of EBERs variants in genomes between different areas had some differences.The EB-8m variant was only prevalent in genomes from southern China and the frequency of it in EBV genomes from endemic NPC cases was up to 86.5%(32/37).EB-6m was dominant in genomes from northern China,Europe,America and Australia,while both EB-8m and B95-8 variants were common in African genomes.B95-8 had the highest frequency in African genomes,followed by genomes in Europe,Americas and Australia,and the lowest in Asian genomes.(3)The f variant only showed high frequency in NPC cases from Guangdong(70.9%,39/55)and in EBV genomes from southern China(56.8%,21/37).The combinational genotype f/EB-8m in NPC cases from Guangdong(64.0%,32/50)was significantly higher than that in healthy donors from Guangong(21.0%,13/62)(?~2=21.325,P<0.0001).The distribution of EBERs variants in cases with type f EBV was different from that in cases with type F(P<0.0001).The cases with type F mainly corresponded to EB-6m variant,whereas the cases with type f mainly corresponded to EB-8m variant.The frequency of EB-8m variant in NPC cases in southern China was higher than f variant(?2=13.136,P=0.0003,OR=10,95%CI,2.878-34.735).Conclusions:(1)EBERs gene shows different variation spectrum between different areas.The EB-6m is the most common variant in detected areas.The EB-8m is only prevalent in NPC cases in southern China,and it may be associated with NPC especially endemic NPC.(2)The f variant demonstrates preferential linkage with EB-8m in isolates from southern China,however,the EB-8m variant seems to be more specific to NPC isolates than f variant as a marker of the representative EBV strains prevalent in endemic NPC.