Zhou Liang, Hang Xiaoling, Xie Lei
Department of Head Neck Surgery and Operation Suite, The Affiliated Sir Run Run Shaw Hospital, Zhejiang University School of Medicine Zhejiang, P. R. China.
Int J Clin Exp Pathol. 2020 Feb 1;13(2):153-162. eCollection 2020.
Epstein-Barr virus (EBV)-encoded latent membrane protein 1 (LMP1) activation of NF-κB is pivotal for EBV-infected B lymphocyte survival. Herein, we found that LMP1 markedly rescued the suppressed the proliferation of several nasopharyngeal carcinoma (NPC) cell lines caused by a Toll-like receptor 3 (TLR3) ligand poly (I:C). We profiled the expression alterations of TLR3 and LMP1 within these NPC cell lines in response to poly (I:C) treatment, and found a high correlation between them ws found, suggesting potential involvement of TLR3 in LMP1 signaling. Then, cells deficient in TLR3 were used to assess its role in poly (I:C)-induced inhibition of cell proliferation and LMP1-mediated NF-κB activation. NF-κB p65 activation and the consequent pro-inflammatory responses were unresponsive to poly (I:C) stimulation after TLR3 knockdown (KD), and NOS2 and MMP9 were substantially suppressed in CNE1-745, but nearly normal in LMP1-overexpressed CNE1-LMP1-745 cells. This suggests an alternative pathway that LMP1 may depend on, in terms of NOS2 and MMP9 regulation, whereas an unusual TLR3-dependent expression of c-Myc was identified. Consistently, poly (I:C)-induced retarded growth was reversed by TLR3 silencing, which was especially enhanced in LMP1-overexpressed cells. TLR3 is essential for poly (I:C)-incited NPC cell death, and occupies a critical role in LMP1-mediated NF-κB activation. Our findings provide new insight into the mechanism underlying LMP1-involved EBV-associated pathogenesis of refractory NPC, thereby potentially improving treatment outcome.
爱泼斯坦-巴尔病毒（EBV）编码的潜伏膜蛋白1（LMP1）激活核因子κB（NF-κB）对于EBV感染的B淋巴细胞存活至关重要。在此，我们发现LMP1显著挽救了由Toll样受体3（TLR3）配体聚肌苷酸-聚胞苷酸（poly (I:C)）导致的几种鼻咽癌（NPC）细胞系增殖受抑制的情况。我们分析了这些NPC细胞系中TLR3和LMP1在poly (I:C)处理后的表达变化，发现它们之间存在高度相关性，提示TLR3可能参与LMP1信号传导。然后，利用缺乏TLR3的细胞评估其在poly (I:C)诱导的细胞增殖抑制和LMP1介导的NF-κB激活中的作用。TLR3敲低（KD）后，NF-κB p65激活及随之的促炎反应对poly (I:C)刺激无反应，在CNE1-745细胞中一氧化氮合酶2（NOS2）和基质金属蛋白酶9（MMP9）被显著抑制，但在LMP1过表达的CNE1-LMP1-745细胞中接近正常。这表明就NOS2和MMP9调节而言，LMP1可能依赖的另一条途径，而c-Myc存在不寻常的TLR3依赖性表达。一致地，TLR3沉默逆转了poly (I:C)诱导的生长迟缓，在LMP1过表达的细胞中尤其明显。TLR3对于poly (I:C)引发的NPC细胞死亡至关重要，并且在LMP1介导的NF-κB激活中起关键作用。我们的发现为LMP1参与的难治性NPC的EBV相关发病机制的潜在机制提供了新见解，从而有可能改善治疗效果。
