[Latency of Epstein-Barr virus and its relationship to nasopharyngeal carcinomas]

Non-radioactive in situ hybridization and image analysis were used to study the distribution of Epstein-Barr virus (EBV) DNA and expression of the EBV latent genes, BNLF1, and BamH1 W sequence, in biopsy specimens of nasopharyngeal carcinoma (NPC) and chronic nasopharyngitis. The results showed that the high copy numbers of EBV genome and the expression of BamH1 W sequence, which was related to the transcription of EBV nuclear antigen 1 (EBNA 1) and the initiation of viral replication, occurred almost simultaneously in all poorly- or un-differentiated NPC. Furthermore, latent membrane protein (LMP) mRNA was expressed even in the nasopharyngeal epithelium with atypical hyperplasia. These results suggested that enormous replication of EBV episomes occurred with the progression of NPC and might be resulted from the activation of the viral promoter in the poorly- or un-differentiated stage of NPC. The inappropriate expression of LMP might be responsible for the proliferation and de-differentiation of nasopharyngeal epithelium.