ObjectiveTo observe the effect of latent membrane protein 1 (LMP1) overexpression on TNFrelated apoptosisinducing ligand(TRAIL)induced apoptosis and TRAILactivated apoptotic pathway.MethodsLMP1 expression in CNE1 which was TRAILresistant LMP1 low expressive nasopharyngeal carcinoma (NPC) cell was upregulated by liposome mediated pGL6LMP1. The TRAIL sensitivities of CNE1LMP1 and CNE1 were measured by MTT and flow cytometry. The expression of death receptor (DR), activation of apoptotic pathway and mitochondrial transmembrane potential were detected by flow cytometry, Western blot and JC1 assessment, respectively.ResultsFlow cytometry showed no significant differences in expressions of DR4 and DR5 between CNE1 and CNE1LMP1 cell lines (all P>0.05). Moreover, after TRAIL (100 ng/ml) administration for 2, 4, 6, 12 hours, the expressions of caspase8 p43/p41, tathmin/oncoprotein 18p18 and caspase3 p17, p10 in CNE1 were higher than those in CNE1LMP1. However, there were no significant differences in expressions of tBid and caspase9 p35 between this two cell lines. JC1 assessment showed that TRAIL administration could not affect the mitochondrial transmembrane potential and there was no significant difference in mitochondrial transmembrane potential between CNE1 and CNE1LMP1.ConclusionLMP1 overexpression can inhibit apoptosis and extracellular apoptotic pathway, which indicates LMP1 may induce TRAILresistance in NPC cell through inhibiting extracellular apoptotic pathway.