Heterogeneity of HLA and EBER expression in Epstein-Barr virus-associated nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is an aggressive tumour of multifactorial ae tiology that, although rare in most parts of the world, poses a significant mortality problem in its high incidence area of Southern China. Improved t herapies ape an urgent requirement and, towards this end, immunotherapeutic methods are being developed in several centres, Such strategies are depend ent on the immune competence of the target tumour, in particular its expres sion of HLA class-I. We examined HLA class-I and -II expression in 27 prima ry NPC biopsies and found that 15% were extensively down-regulated for clas s-I expression with the majority of tumour cells appearing negative. Whilst HLA class-ii was expressed at high levels in the majority of tumours, 37% showed substantial down-regulation. NPC is associated with Epstein-Barr vir us (EBV), Expression of the virus-encoded EBER RNAs is accepted as a marker of EBV latency and is regarded as a valuable diagnostic criterion, EBER RN As were expressed in all samples, but in some the level was remarkably hete rogeneous, being barely detectable in many tumour cells. Our study reinforc es the concept of extensive phenotypic variation in NPC, There are morpholo gical differences between tumour cells. Some tumours express HLA class-I an d/or -II, whilst others are down-regulated or negative. Individual tumours may or may not express the EBV-encoded LMP-I protein, and individual tumour cells may express high levels of EBER, yet adjacent tumour cells express v ery little or none. Int. J, Cancer 88:949-955, 2000, (C) 2000 Wiley-Liss, I nc.