[Effect of EB virus latent membrane protein 1 on mitosis control of nasopharyngeal carcinoma cell line CNE1].

Background & Objective: Epstein-Barr virus (EBV) latent membrane protein 1(LMP1)is the only one of approved oncogene coded by virus gene in nasopharyngeal carcinoma (NPC). LMP1 is involved in the regulation of cell cycle but it is still unknown if LMP1 induces the disturbance of mitosis control and mitotic checkpoint. The aim of this study was to investigate the effect of EBV-LMP1 on mitosis control of NPC cell line CNE1 and the related pathogenesis of NPC.

Methods: Cell cycle and the function of mitotic checkpoint were assayed by flow cytometry in human NPC cells cultured in vitro, including CNE1 cell line (well differentiated cells of NPC, WHO classified it as keratinizing squamous cell carcinoma), CNE1-GL cell strain (CNE1 cell line transfected with an eukaryotic plasmid PAT-GFP-LMP1) and CNE-2Z cell line (poorly differentiated cells of NPC, WHO classified it as differentiated non-keratinizing carcinoma). Before investigating expression of proteins, the cells were synchronized at mitosis phase. The expression of mitotic regulators, P34(cdc2), cyclin B1, and p53 was subsequently determined using Western blot analysis.

Results: The G(2)/M ratio of CNE1-GL was significantly elevated compared with CNE1 (P< 0.05). A defective mitotic checkpoint was identified in CNE1-GL, and this phenomenon was also known as "mitotic slippage". Western blot analysis showed that the expression levels of P34(cdc2) and cyclin B1 proteins in CNE1-GL were 1.22+/-0.04 and 2.12+/-0.07 times higher than that of those in CNE1, respectively,but there was no difference in the expression of p53 protein between CNE1-GL and CNE1.

Conclusion: LMP1 disturbs mitosis control and the function of mitotic checkpoint of CNE1 through up-regulating the expression of P34(cdc2) and cyclinB1 proteins.