title: Epstein-Barr Virus_Encoded LMP1 upregulates microRNA-21 to promote the resistance of nasopharyngeal carcinoma cells to cisplatin-induced Apoptosis by suppressing PDCD4 and Fas-L.
abstract: Approximately 30% of patients with Epstein-Barr virus (EBV)-positive advanced nasopharyngeal carcinoma (NPC) display chemoresistance to cisplatin-based regimens, but the underlying mechanisms are unclear. The Epstein-Barr virus (EBV)-encoded latent membrane protein 1 (LMP1), a functional homologue of the tumor necrosis factor receptor family, contributes substantially to the oncogenic potential of EBV through the activation of multiple signaling pathways, and it is closely associated with a poorer prognosis for NPC. Recent studies show that EBV infection can induce the expression of many cellular miRNAs, including microRNA-21, a biomarker for chemoresistance. However, neither a link between LMP1 expression and miR-21 upregulation nor their cross talk in affecting chemoresistance to cisplatin have been reported. Here, we observed that stable LMP1-transformed NPC cells were less sensitive to cisplatin treatment based on their proliferation, colony formation, the IC50 value of cisplatin and the apoptosis index. Higher levels of miR-21 were found in EBV-carrying and LMP1-positive cell lines, suggesting that LMP1 may be linked to miR-21 upregulation. These data were confirmed by our results that exogenous LMP1 increased miR-21 in both transiently and stably LMP1-transfected cells, and the knock down of miR-21 substantially reversed the resistance of the NPC cells to cisplatin treatment. Moreover, the proapoptotic factors programmed cell death 4 (PDCD4) and Fas ligand (Fas-L), which were negatively regulated by miR-21, were found to play an important role in the program of LMP1-dependent cisplatin resistance. Finally, we demonstrated that LMP1 induced miR-21 expression primarily by modulating the PI3K/AKT/FOXO3a signaling pathway. Taken together, we revealed for the first time that viral LMP1 triggers the PI3K/Akt/FOXO3a pathway to induce human miR-21 expression, which subsequently decreases the expression of PDCD4 and Fas-L, and results in chemoresistance in NPC cells.
authors.affiliation: Department of Experimental Research, State Key Laboratory of Oncology in South China, Cancer Center, Sun Yat-Sen University, Guangzhou, China.
authors.forename: Guang-Da
authors.initials: GD
authors.lastname: Yang
authors.forename: Tie-Jun
authors.initials: TJ
authors.lastname: Huang
authors.forename: Li-Xia
authors.initials: LX
authors.lastname: Peng
authors.forename: Chang-Fu
authors.initials: CF
authors.lastname: Yang
authors.forename: Ran-Yi
authors.initials: RY
authors.lastname: Liu
authors.forename: Hong-Bing
authors.initials: HB
authors.lastname: Huang
authors.forename: Qiao-Qiao
authors.initials: QQ
authors.lastname: Chu
authors.forename: Hong-Jie
authors.initials: HJ
authors.lastname: Yang
authors.forename: Jia-Ling
authors.initials: JL
authors.lastname: Huang
authors.forename: Zhen-Yu
authors.initials: ZY
authors.lastname: Zhu
authors.forename: Chao-Nan
authors.initials: CN
authors.lastname: Qian
authors.forename: Bi-Jun
authors.initials: BJ
authors.lastname: Huang
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins / Q000037:antagonists & inhibitors / Q000235:genetics; D015153:Blotting, Western; D002277:Carcinoma; D002460:Cell Line; D002945:Cisplatin / Q000494:pharmacology / Q000627:therapeutic use*; D003114:Colony-Forming Units Assay; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D053222:Fas Ligand Protein / Q000037:antagonists & inhibitors / Q000235:genetics; D005455:Fluorescent Antibody Technique; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D020128:Inhibitory Concentration 50; D008156:Luciferases; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D000077274:Nasopharyngeal Carcinoma; D009303:Nasopharyngeal Neoplasms / Q000188:drug therapy* / Q000821:virology; D016601:RNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D013778:Tetrazolium Salts; D013844:Thiazoles; D014763:Viral Matrix Proteins / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D051017:Apoptosis Regulatory Proteins; C037662:EBV-associated membrane antigen, Epstein-Barr virus; C505661:FASLG protein, human; C499517:FOXO3 protein, human; D053222:Fas Ligand Protein; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; C524940:MIRN21 microRNA, human; D035683:MicroRNAs; C114487:PDCD4 protein, human; D016601:RNA-Binding Proteins; D013778:Tetrazolium Salts; D013844:Thiazoles; D014763:Viral Matrix Proteins; D008156:Luciferases; C022616:thiazolyl blue; D002945:Cisplatin