Study On The Influence Of Epstein-Barr Virus Infection On IGF2 Gene Methylation And Imprinting Expression

Objective: This study aimed to detect the influence of EBV infection on IGF2 gene promoter methylation and imprinting status and expression, and further explore the relationship of IGF2 gene and the occurrence and development of EBVa GC.Methods: The methylation staus of IGF2 gene promoter in EBV positive and negative cell lines and gastric cancer tissues were detected by bisulfite genomic sequencing(BGS).In order to analyze the imprinting status of IGF2, polymerase chain reaction-restriction fragment length polymorphism(PCR-RFLP) were carried out in EBVa GC and EBVn GC and normal adjacent tissues of gastric carcinoma samples, respectively. The m RNA expression of IGF2 in EBVa GC and EBVn GC was tested by real time quantitative PCR(real time q PCR). The expression of IGF2 protein in EBVa GC and EBVn GC and normal adjacent tissues of gastric carcinoma samples were tested by immunohistochemmistry.Results:(1)BGS results show high methylation rate both EBV positive and negative cell lines; the mean methylation rate of IGF2 gene promoter in EBVa GC is 38.17% and in EBVn GC is 23.06%. Statistical analysis showed that the methylation rate of IGF2 gene promoter in EBVa GC is significantly higher than EBVn GC(P<0.05).(2)IGF2 LOI rate in EBVa GC samples is 61.3%(61.3%, 19/31), and in EBVn GC samples is 33.3%(33.3%,15/45). The rate of IGF2 LOI in EBVa GC specimens was significantly higher than EBVn GC specimens(χ2 =5.803, P<0.05).(3)There is no significant difference of IGF2 m RNA expression in EBVa GC and EBVn GC(P>0.05).(4)There is no significant differences of IGF2 protein expression in EBVa GC and EBVn GC(P>0.05); however, the expression of IGF2 protein in gastric cancer specimens was significantly higher than normal adjacent tissues of gastric carcinoma samples(P<0.05).Conclusion:(1) EBV infection can induce hypermethylation of IGF2 gene promoter and loss of imprinting of IGF2.(2) The effects of EBV infection, methylation and imprinting state of IGF2 gene on the transcription and expression of IGF2 were not observed, which indicated that the regulation mechanism of IGF2 expression was more complex and might be regulated by many factors.(3) The high expression of IGF2 protein in gastric carcinoma showed that it might be involved in the occurrence and development of gastric cancer.