Carcinogenesis, Teratogenesis & Mutagenesis ›› 2018, Vol. 30 ›› Issue (5): 333-338,344.doi: 10.3969/j.issn.1004-616x.2018.05.001

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A variant of Epstein-Barr virusencoded small RNA 2 enhanced resistance to apoptosis by inhibiting the PKR pathway in nasopharyngeal carcinoma cell lines

HE Huijing1, LIU Jincheng1, LIU Qianqian2, WANG Yun1   

  1. 1. School of Pathogenic Biology, Qingdao University, Qingdao 266021;
    2. Department of Clinical Laboratory, Laigang Hospital, Laiwu 271126, Shandong, China
  • Received:2018-05-01 Revised:2018-09-06 Online:2018-09-30 Published:2018-09-30

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Abstract: OBJECTIVE:Previous studies demonstrated that the EB-8m variant of Epstein-Barr virus (EBV)-encoded small RNA 2 (EBER2) might be associated with nasopharyngeal carcinoma (NPC). The aim of this study was to investigate whether the variant EBER2 would confer resistance to apoptotic by enhancing inhibition of RNA-activated protein kinase (PKR) in NPC cell lines. METHODS:The cell anti-apoptosis observation induced by 10 000 IU/mL interferon-α(IFN-α) or 2μg/mL cisplatin was conducted in EBV-negative NPC cell lines (CNE1 and HONE1) with stable expression of wild type or EB-8m variant EBER2 gene under the control of lentivirus vector transfection group. Western blotting was performed to determine phosphorylation of PKR, eIF2α and c-Jun (which are down streams of PKR activation),expression of Bcl-2 in IFN-α-treated cells with stable expression of EBER2 and control cells. RNA-binding protein immunoprecipitation against PKR was assayed in cells with stable expression of EBER2 to detect the fold enrichment of EBER2 with PKR. RESULTS:EBER2 -expressing NPC cells enhanced anti-apoptosis ability in contrast to the control cells (P < 0.05 or P < 0.01),and the cells expressing variant EBER2 showed higher anti-apoptosis ability compared with those expressing wild type EBER2 (P < 0.05). Compared with the control cells,EBER2-expressing cells showed lower level of phosphorylation of PKR, eIF2α and c-Jun and elevation of Bcl-2 (P < 0.05). The levels of phosphorylated PKR in variant EBER2 transfected HONE1 and CNE1 cells were significantly lower than that in wild type EBER2 transfected cells (P < 0.05). That of phosphorylated eIF2α in variant EBER2 transfected HONE1 cells was also significantly lower than that in wild type EBER2 transfected cells (P < 0.05). EBER2 could be detected in immunoprecipitation against PKR, and the variant EBER2 had higher fold enrichment than wild type EBER2 (P < 0.05). CONCLUSION:The EB-8m variant EBER2 demonstrated its inhibition of PKR,and of phosphorylation of eIF2α and c-Jun,and up-regulated Bcl-2 expression,thus enhanced the anti-apoptosis ability of NPC cell lines.

Key words: Epstein-Barr virus, EBER2, nasopharyngeal carcinoma, gene variation, RNA-activated protein kinase

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