title: The molecular mechanisms of XBP-1 gene silencing on IRE1α-TRAF2-ASK1-JNK pathways in oral squamous cell carcinoma under endoplasmic reticulum stress.
abstract: BACKGROUND
  Proteasome inhibitor Carbobenzoxy-Leu-Leu-leucinal (MG132) induces the unfolded protein response (UPR) in oral squamous cell carcinoma (OSCC). X-box binding protein 1 (XBP1) is a key UPR component that regulates endoplasmic reticulum stress (ER) homeostasis. This study was aimed to investigate the activation of IRE1α-TRAF2-ASK1-JNK pathway by silencing the XBP1 expression in an OSCC cell line.
  
  
  METHODS
  The XBP1 specific short hairpin RNA (shRNA) plasmid vector was constructed and then transfected into the Tca-8113 cells. The effect of XBP-1 gene silencing on IRE1α-TRAF2-ASK1-JNK pathway under MG132 induced endoplasmic reticulum stress in Tca-8113 were investigated by real-time RT-PCR or western blot. Cell apoptosis was detected by flow cytometry.
  
  
  RESULTS
  XBP1 expression was reduced in transfected groups and MG132 groups. shRNA-XBP1 induces IRE1α-TRAF2-ASK1 signaling activation to activate pro-apoptotic ASK1-JNK signaling. Moreover, combined shRNA-XBP1 with MG132 further enhanced downregulated XBP1 expression and upregulated activation of ASK1-JNK signaling.
  
  
  CONCLUSIONS
  Silencing XBP1 expression under MG132 induced ER stress block the XBP1 survival pathway and synergism with MG132 to promote Tca8113 cell apoptosis. These findings provide a therapeutic option in oral squamous cell carcinoma by inhibition of proteasome and XBP1 splicing.
authors.affiliation: Oral Maxillofacial Head-Neck Key Laboratory of Medical Biology, and Central Laboratory of Liaocheng People's Hospital, Shandong 252000, China; Department of Pharmacy, Liaocheng University, Shandong 252000, China.
authors.forename: Haiying
authors.initials: H
authors.lastname: Chen
authors.affiliation: Oral Maxillofacial Head-Neck Key Laboratory of Medical Biology, and Central Laboratory of Liaocheng People's Hospital, Shandong 252000, China.
authors.forename: Hongli
authors.initials: H
authors.lastname: Yang
authors.affiliation: Oral Maxillofacial Head-Neck Key Laboratory of Medical Biology, and Central Laboratory of Liaocheng People's Hospital, Shandong 252000, China.
authors.forename: Li
authors.initials: L
authors.lastname: Pan
authors.affiliation: Oral Maxillofacial Head-Neck Key Laboratory of Medical Biology, and Central Laboratory of Liaocheng People's Hospital, Shandong 252000, China.
authors.forename: Weihua
authors.initials: W
authors.lastname: Wang
authors.affiliation: Department of Oral and Maxillofacial Surgery, Liaocheng People's Hospital, Shandong 252000, China.
authors.forename: Xianbin
authors.initials: X
authors.lastname: Liu
authors.affiliation: Oral Maxillofacial Head-Neck Key Laboratory of Medical Biology, and Central Laboratory of Liaocheng People's Hospital, Shandong 252000, China.
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Ren
authors.affiliation: Oral Maxillofacial Head-Neck Key Laboratory of Medical Biology, and Central Laboratory of Liaocheng People's Hospital, Shandong 252000, China.
authors.forename: Yihua
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Oral Maxillofacial Head-Neck Key Laboratory of Medical Biology, and Central Laboratory of Liaocheng People's Hospital, Shandong 252000, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Liu
authors.affiliation: Oral Maxillofacial Head-Neck Key Laboratory of Medical Biology, and Central Laboratory of Liaocheng People's Hospital, Shandong 252000, China.
authors.forename: Yingxin
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Oral and Maxillofacial Surgery, Liaocheng People's Hospital, Shandong 252000, China.
authors.forename: Licheng
authors.initials: L
authors.lastname: Jiang
authors.affiliation: Department of Oral and Maxillofacial Surgery, Liaocheng People's Hospital, Shandong 252000, China.
authors.forename: Keyi
authors.initials: K
authors.lastname: Li
authors.affiliation: Department of Oral and Maxillofacial Surgery, Liaocheng People's Hospital, Shandong 252000, China. Electronic address: Bin_zhanglc@yahoo.com.cn.
authors.forename: Bin
authors.initials: B
authors.lastname: Zhang
authors.affiliation: School of Biomedical Sciences, Charles Sturt University, Wagga Wagga, NSW 2650, Australia. Electronic address: lwang@csu.edu.au.
authors.forename: Le-Xin
authors.initials: LX
authors.lastname: Wang
mesh_terms: D017209:Apoptosis; D002294:Carcinoma, Squamous Cell / Q000235:genetics*; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000235:genetics*; D059865:Endoplasmic Reticulum Stress / Q000502:physiology*; D004722:Endoribonucleases / Q000378:metabolism; D020868:Gene Silencing; D006801:Humans; D007976:Leupeptins / Q000235:genetics*; D020935:MAP Kinase Signaling System / Q000502:physiology*; D009062:Mouth Neoplasms / Q000235:genetics*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D034741:RNA, Small Interfering; D000071701:Regulatory Factor X Transcription Factors; D015398:Signal Transduction; D047992:TNF Receptor-Associated Factor 2 / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics*; D000071717:X-Box Binding Protein 1
chemical_list: D004268:DNA-Binding Proteins; D007976:Leupeptins; D034741:RNA, Small Interfering; D000071701:Regulatory Factor X Transcription Factors; D047992:TNF Receptor-Associated Factor 2; D014157:Transcription Factors; D000071717:X-Box Binding Protein 1; C000605543:XBP1 protein, human; C528229:ERN1 protein, human; D017346:Protein Serine-Threonine Kinases; D004722:Endoribonucleases; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde
keywords: Apoptosis; MG132; Oral squamous cell carcinoma; Silencing; X-box binding protein 1