Clonal proliferations of cells infected with Epstein–barr virus in preinvasive lesions related to nasopharyngeal carcinoma

The Epstein–Barr virus (EBV) is consistently detected in patients with nasopharyngeal carcinoma. To determine whether EBV infection is an early, initiating event in the development of this malignant tumor, we screened nasopharyngeal-biopsy samples, most of which were archival, for preinvasive lesions, including dysplasia and carcinoma in situ. Preinvasive lesions were found in 11 samples, which were tested for the presence of EBV. EBV infection was detected with in situ hybridization for EBV-encoded RNAs (EBERs) and by immunohistochemical staining for latent membrane protein 1 (LMP-1). The larger samples were also tested for the EBV genome with the use of Southern blotting. The expression of specific EBV RNAs was determined by the amplification of complementary DNA with the polymerase chain reaction. Evidence of EBV infection was detected in all 11 tissue samples with dysplasia or carcinoma in situ. EBERs were identified in all eight samples tested, and LMP-1 was detected in all six of the tested samples. Six of the seven samples tested for the EBV termini contained clonal EBV DNA. Transcription of the latent EBV gene products, EBV nuclear antigen 1, LMP-1, LMP-2A, and the Bam HI-A fragment, was detected in most of the samples. Viral proteins characteristic of lytic lesions were not detected. Preinvasive lesions of the nasopharynx are infected with EBV. The EBV DNA is clonal, indicating that the lesions represent a focal cellular growth that arose from a single EBV-infected cell and that EBV infection is an early, possibly initiating event in the development of nasopharyngeal carcinoma. Preinvasive lesions contain EBV RNAs that are characteristic of latent infection but not the viral proteins that are characteristic of lytic infection. The detection of the EBV-transforming gene, LMP-1, in all the neoplastic cells suggests that its expression is essential for preinvasive epithelial proliferations associated with nasopharyngeal carcinoma. The Epstein–Barr virus (EBV) is an important factor in the development of nasopharyngeal carcinoma, an epithelial cancer.¹,² Nasopharyngeal carcinoma is rare in North American and European whites, with an age-adjusted incidence of 1 case per 100,000 population. In contrast, it is among the most common cancers in southern China and parts of southeast Asia. An age-adjusted incidence of 26 cases per 100,000 has been reported among males in Hong Kong. Genetic and environmental factors appear to contribute to the elevated risk of nasopharyngeal carcinoma among the Chinese. Patients with nasopharyngeal carcinoma have elevated titers of IgA antibodies to EBV.