Regulation of survivin and CDK4 by Epstein-Barr virus encoded latent membrane protein 1 in nasopharyngeal carcinoma cell lines.

Latent membrane protein 1 (LMP1), an important protein encoded by Epstein Barr virus (EBV), has been implied to link with the pathogenesis of nasopharyngeal carcinoma (NPC). Its dual effects of increasing cell proliferation and inhibiting cell apoptosis have been confirmed. In this study, we showed that the expression of Survivin and CDK4 protein in CNE-LMP1, a LMP1 positive NPC epithelial cell line, is higher than in LMP1 negative NPC epithelial cell line-CNE1, and the expression is LMP1 dosage-dependent. Although it was reported that Survivin specifically expressed in cell cycle G2/M phase, our studies suggested that LMP1 could promote the expression of Survivin in G0/G1, S and G2/M phase. It also showed that Survivin and CDK4 could be accumulated more in the nuclei triggered by LMP1. More interestingly, Survivin and CDK4 could form a protein complex in the nuclei of CNE-LMP1 rather than in that of CNE1, which demonstrated that the interaction between these two proteins could be promoted by LMP1. These results strongly suggested that the role of LMP1 in the regulation of Survivin and CDK4 may also shed some light on the mechanism research of LMP1 in NPC.

[Cross-talk between c-Jun/Ets1 involved in EB virus-encoded latent membrane protein 1 regulates expression of matrix metalloproteinase-9 in nasopharyngeal carcinoma].

OBJECTIVE: To investigate effect of AP-1 and Ets binding site adjacent to matrix metalloproteinase-9 (MMP-9) promoter on activation of MMP-9 transcription of nasopharyngeal carcinoma cells transfected with EBV-encoded latent membrane protein 1 (LMP1), and to ascertain if cross-talk between c-Jun and Ets1 is involved in LMP1-regulating expression of MMP-9. METHODS: Site-directed mutagenesis technique was used to establish a series of mutants, including MMP-9-CAT-Ets(-540)mt, MMP-9-CAT-AP-1(-533)mt and MMP-9-CAT-AP-1(-533)/Ets(-540)mt. After the mutants were transfected into LMP1-expressing NPC HNE2 cells regulated by Tet-on system (pTet-on-LMP1 HNE2), CAT activity of these mutants were assayed with induction of LMP1. With blockade of c-Jun or Ets1 antisense oligonucleotides, the activity of MMP-9 induced by LMP1 was assayed with gelatin zymography. RESULTS: The CAT activity of MMP-9-Ets(-540)mt-CAT, MMP-9-AP-1(-533)mt-CAT, MMP-9-AP-1(-533)/Ets(-540) mt-CAT decreased significantly compared to MMP-9-CAT wt. After blockade with c-Jun or Ets1 antisense oligonucleotides, activity of MMP-9 induced by LMP1 decreased significantly, especially with combined blockade of c-Jun and Ets1. CONCLUSION: The results suggest that transcription factor AP-1 and Ets play an crucial role in activation of MMP-9 transcription induced by LMP1, and cross-talk between c-Jun/Ets1 is involved in expression of MMP-9 mediated by LMP1.