Regulation of inflammatory cytokines by Epstein-Barr virus latent membrane protein 1 (LMP1)

• Main Authors: Siao-Jing Lai, 賴曉菁
• Other Authors: Hsiao-Sheng Liu
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/54417185377885715959

碩士 === 國立成功大學 === 微生物及免疫學研究所 === 96 === Chronic inflammation can promote tumor cell proliferation, survival, and metastasis through inflammatory cytokines. Inflammation-like microenvironment and production of inflammatory cytokines have also been observed in Epstein-Barr virus (EBV)-associated nasopharyngeal carcinoma (NPC), but the contribution of EBV infection to this phenomenon is not fully understood. EBV latent membrane protein 1 (LMP1) has been considered an oncoprotein and can regulate many cellular genes through triggering multiple cell signaling pathways, so we wondered whether LMP1 can regulate expression of inflammatory cytokines in NPC cells. First, we utilized a protein array to examine the cytokine expression profiles, and eight cytokines were found to be upregulated by LMP1. Among these cytokines, MIP-1 alpha, MIP-1 beta, and GM-CSF were novel target genes of LMP1, so they were chosen for further study. We found that exogenous LMP1 induced production of MIP-1 alpha, MIP-1 beta, and GM-CSF in NPC and Hodgkin’s lymphoma cells, and also demonstrated that endogenous LMP1 enhanced expression of the three cytokines in EBV-infected NPC cells. Analyzing the signaling pathways activated by LMP1 in NPC cells, we found that the canonical nuclear factor-kappa B (NF-kappa B), non-canonical NF-kappa B and c-Jun N-terminal kinase (JNK) signaling pathways can be activated significantly and consistently. Within the intracellular carboxyl terminus of LMP1, two C-terminal activating regions (CTARs), CTAR1 and CTAR2, are responsible for activation of signal transduction. We also observed that CTAR1 was important for non-canonical NF-kappa B pathway, and CTAR2 was important for canonical NF-kappa�羠 and JNK pathways. LMP1 mutants with deletion at CTAR1 or CTAR2 significantly lost their ability to induce MIP-1 alpha, MIP-1 beta, and GM-CSF. Using inhibitors of NF-kappa B or JNK signaling pathways, we found that activation of NF-kappa B and JNK pathways were required for LMP1-induced production of the three cytokines. It has been reported that MIP-1 alpha and MIP-1 beta can recruit various immune cells, including T lymphocytes, which are dominant in the infiltrates in NPC. MIP-1 beta and GM-CSF may also act as immuregulatory factors in some circumstances. Therefore, our data suggest that LMP1 may modulate local immune responses in NPC tissues through upregulation of the inflammatory cytokines.