Association of Epstein-Barr virus with oral cancers.

Epstein-Barr virus (EBV) persists in the epithelial cells of oral mucosa and often replicates on them. EBV is known to be a causative agent of nasopharyngeal carcinoma. We suspect that EBV may be associated with oral cancers, and thus examined EBV expression on 28 tongues and 9 other oral cancers. We also examined 6 metastatic lesions in the lymph nodes. All cancers were squamous cell carcinoma (SCC). We used mRNA in situ hybridization, immunofluorescence staining, reverse transcriptase-polymerase chain reaction (RT-PCR), and polymerase chain reaction (PCR). The mRNA in situ hybridization using a probe comprising the transcripts of the BamHIW fragment of the EBV genome demonstrated EBV mRNA in the majority of tumor cells in all cases of oral cancer, but in none of the normal tissues. RNA in situ hybridization using an EBER1 probe detected RNAs in 16 out of 24 cancers. Also, mRNA in situ hybridization using a probe of the EBV-determined nuclear antigen-2 (EBNA2) region detected positive signals in 9 out of 12 cancers. Furthermore, EBNA2, latent membrane protein-1 (LMP1) and BZLF1 were detected in these cancers by immunofluorescence staining, but were not detected in any of the epithelial cells of the normal tissues. Four out of 6 metastatic tissues showed stronger fluorescence than that in the primary tissues. RT-PCR analysis also showed EBER1 expression in 1 of the 3 tongue cancers. PCR detected the BamHIW sequence of EBV DNA in all cases, including the normal tissues tested. These findings indicate that EBV may be involved in neoplastic transformation in oral cancers, such as nasopharyngeal carcinoma.