Correlation between DNA damage and EB virus infection in nasopharyngeal carcinoma]

To explore the correlation between the expression of phosphorylated histone H2AX (γ-H2AX) and Epstein-Barr virus (EBV) infection in nasopharyngeal carcinoma (NPC) specimens, and to investigate the role and mechanism of EBV-induced DNA damage in NPC tumorigenesis and development in vitro.We enrolled 50 cases of NPC and 20 cases of nasopharyngitis (NPI) specimens to test the expressions of γ-H2AX and EBV latent membrane protein 1 (LMP1) by immunohistochemical method (IHC). And then in LMP1-negative samples, we detected the EBV-encoded RNA (EBER) using in situ hybridization. The γ-H2AX level was detected in NPC cells CNE1 before and after EBV infection using Western blotting.γ-H2AX was expressed in most NPC specimens (94%), which was much higher than that in NPI (40%), and EBV was presented in 94% of NPC but only 30% in NPI. Moreover, γ-H2AX was positive in 97.9% of the EBV-positive specimens, which indicated the close correlation between γ-H2AX expression and EBV infection (P<0.05). Finally, Western blotting showed that γ-H2AX level significantly increased in CNE1 cells after EBV infection.This study demonstrated that an intimate connection existed between γ-H2AX expression and EBV infection in NPC both in vivo and in vitro. EBV infection might induce DNA damage in CNE1 cells, which causes genome instability and initiates or promotes the tumorigenesis and development of NPC.