The molecular mechanisms of XBP-1 gene silencing on IRE1α-TRAF2-ASK1-JNK pathways in oral squamous cell carcinoma under endoplasmic reticulum stress

Biomed Pharmacother. 2016 Feb:77:108-13. doi: 10.1016/j.biopha.2015.12.010. Epub 2015 Dec 29.

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.

Keywords: Apoptosis; MG132; Oral squamous cell carcinoma; Silencing; X-box binding protein 1.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis
  • Carcinoma, Squamous Cell / genetics*
  • Cell Line, Tumor
  • DNA-Binding Proteins / genetics*
  • Endoplasmic Reticulum Stress / physiology*
  • Endoribonucleases / metabolism
  • Gene Silencing
  • Humans
  • Leupeptins / genetics*
  • MAP Kinase Signaling System / physiology*
  • Mouth Neoplasms / genetics*
  • Protein Serine-Threonine Kinases / metabolism
  • RNA, Small Interfering
  • Regulatory Factor X Transcription Factors
  • Signal Transduction
  • TNF Receptor-Associated Factor 2 / metabolism
  • Transcription Factors / genetics*
  • X-Box Binding Protein 1

Substances

  • DNA-Binding Proteins
  • Leupeptins
  • RNA, Small Interfering
  • Regulatory Factor X Transcription Factors
  • TNF Receptor-Associated Factor 2
  • Transcription Factors
  • X-Box Binding Protein 1
  • XBP1 protein, human
  • ERN1 protein, human
  • Protein Serine-Threonine Kinases
  • Endoribonucleases
  • benzyloxycarbonylleucyl-leucyl-leucine aldehyde