EFFECTS OF EB VIRUS ENCODED LMP1 ON DIFFERENTIATION OF NASOPHARYNGEAL CARCINOMA CELLS

Objective: To investigate the effects of Epstein- Barr virus (EBV) encoded latent membrane protein 1 (LMP1) expression on tumor cell differentiation in early-stage nasopharyngeal carcinoma (NPC). Methods: Thirty-one biopsies of early-stage NPC were collected from the Cancer Center, Sun Yat-sen University. All 31 NPCs were of non-keratinizing carcinoma in histological type. The Epstein-Barr virus early RNAs (EBERs) were detected by use of DAKO PNA Probe (Y5200) and PNA ISH Detection Kit (K5201). The LMP1, a-catenin, b-catenin, g-catenin, high- molecular and low-molecular weight cytokeratins were detected by immunohistochemistry. Results: All 31 carcinoma biopsies studied showed a considerable number of EBERs-positive tumor cells, and 19 out of 31 cases (61.29%) expressed LMP1. The mean percentage of g-catenin expression in LMP1 positive group (53.25±34.12% ) was significantly lower than that (80.42±15.77%) in LMP1 negative group, (P<0.01). The g-catenin expression was positively correlated with the expression of low molecular weight cytokeratin (r=0.440, P<0.05). There were positive correlations for the expression of a-catenin, b-catenin and g-catenin in between. Conclusion: The LMP1 could down-regulate the expression of g-catenin and thus inhibit the tumor cell differentiation in early-stage NPC.