Expression of Epstein-Barr virus in mesopharyngeal and hypopharyngeal carcinomas

Epstein-Barr virus (EBV) causes various tumors, including nasopharyngeal carcinoma (NPC). There have been no reports as to whether the carcinogenicity of EBV is restricted to the nasopharynx or extends into the mesopharynx and hypopharynx. We attempted to ascertain the relation between EBV and mesopharyngeal (MPC) and hypopharyngeal carcinomas (HPC). Messenger RNA in situ hybridization showed that all 29 cases of MPC and 5 of 12 HPC expressed EBV mRNA. For further analysis, we established 7 cell lines from 5 MPC and 2 HPC. All cell lines and 5 tumors formed by these cultured cells in nude mice expressed EBV transcripts. Moreover, immunofluorescence staining showed expression of EBV-related nuclear antigen-2 and latent membrane protein-1 (LMP1) in the original tumors and the cell lines, as well as in nude mouse tumors. Study by reverse transcription polymerase chain reaction (RT-PCR) also showed EBER1 and LMP1 expression. Furthermore, lytic-cycle antigens of EBV were detectable in most cell lines. Nested PCR showed the EBV genome in 3 cases of MPC and 4 cases of HPC. These results suggest that EBV plays an important role in the development of MPC and HPC as well as in NPC.