EPSTEIN-BARR-VIRUS INFECTION IN THE PATHOGENESIS OF NASOPHARYNGEAL-CARCINOMA

Nasopharyngeal carcinomas (NPC) belong to the most frequent malignant tumours in certain parts of the world, e.g., south-east Asia, while th ey occur infrequently in western Europe. The association of NPCs with Epstein-Barr virus (EBV),a transforming human herpes virus, is well es tablished. The current WHO classification recognises two major NPC his totypes, non-keratinising NPC and squamous cell NPC. EBV is invariably present in non-keratinising NPCs and the viral oncoprotein LMP-1 (lat ent membrane protein-1) is expressed in some cases. The tumour cells o f: non-keratinising NPCs show phenotypic features which are inducible by LMP-1 in vitro. These may contribute to the development of the lymp hoid stroma which is characteristic of this tumour type. Furthermore,t he virus is detectable in nasopharyngeal carcinoma in situ. Thus,the v irus is likely to be involved in the pathogenesis of non-keratinising NPCs. By contrast, the association of squamous cell NPCs with EBV disp lays a geographical variability. It appears, therefore, that squamous cell NPCs are a heterogenous group of tumours distinct from non-kerati nising NPCs.