Nasopharyngeal carcinoma: recent studies and outlook for a viral etiology.

Abstract

Recent studies have brought new elements in assessing the role of the lymphotropic Epstein-Barr virus in the development of nasopharyngeal carcinoma (NPC). In electron microscopy, we noted close contacts between lymphoid and epithelial cells in the normal nasopharyngeal mucosa, in NPC biopsies, and in the in vitro growths derived from the NPC biopsies. Such close contacts with occasional loss of adjacent cell membrane continuity suggested that cell cooperation might play an important role in NPC development if a lymphotropic virus is involved. In serology, we observed that NPC sera exhibited 10-fold higher antibody titers than Burkitt's lymphoma sera, against a soluble complement-fixing (CF) antigen. Furthermore, while CF antibody titers fluctuated in Burkitt's lymphoma patients according to the clinical evolution, they were very high and stable in NPC patients regardless of the stage of the disease and of the clinical evolution. CF antibodies did not appear to be related to viral capsid or early antigen activities. Preliminary results indicate the presence of CF nuclear antigen in NPC biopsies. Our ongoing seroepidemiological program, although not completed, shows that adult Chinese males have lower viral capsid antigen antibody titers and higher CF antibody titers (against a soluble antigen) than Indian males. Etiological hypotheses and research priorities are presented which include: completion and analysis of the ongoing field studies, boosting of the laboratory investigations, i.e. , the development of an experimental model, the assessment of serological reactivities to disease development and continuation of immunogenetic studies in Singapore.