Enhanced Selenium Effect on Growth Arrest by BiP/GRP78 Knockdown in p53-null Human Prostate Cancer Cells

Oncogene. 2006 Jan 26;25(4):546-54. doi: 10.1038/sj.onc.1209071.

Abstract

Redox modification of thiol/disulfide interchange in proteins by selenium could lead to protein unfolding. When this occurs in the endoplasmic reticulum (ER), a process known as unfolded protein response (UPR) is orchestrated for survival through activation of PERK-eIF2alpha (PERK: double-stranded RNA-activated protein kinase-like ER kinase; eIF2alpha: eucaryotic initiation factor 2alpha), ATFalpha (ATFalpha: activating transcription factor 6) and inositol requiring 1 (IRE1)-x-box-binding protein 1 (XBP1) signalings. All three UPR transducer pathways were upregulated very rapidly when PC-3 cells were exposed to selenium. These changes were accompanied by increased expression of UPR target genes, including immunoglobulin heavy chain-binding protein/glucose-regulated protein, 78 kDa and CCAAT/enhancer binding protein-homologous protein/growth arrest- and DNA damage-inducible gene (CHOP/GADD153). Induction of BiP/GRP78, an ER-resident chaperone, is part of the damage control mechanism, while CHOP/GADD153 is a transcription factor associated with growth arrest and apoptosis in the event of prolonged ER stress. Knocking down BiP/GRP78 induction by small interference RNA produced a differential response of the three transducers to selenium, suggesting that the signaling intensity of each transducer could be fine-tuned depending on BiP/GRP78 availability. In the presence of selenium, CHOP/GADD153 expression was raised even higher by BiP/GRP78 knockdown. Under this condition, the selenium effect on wild-type p53-activated fragment p21 (p21(WAF)), cyclin-dependent kinase (CDK)1 and CDK2 was also magnified in a manner consistent with enhanced cell growth arrest. Additional experiments with CHOP/GADD153 siRNA knockdown strongly suggested that CHOP/GADD153 may play a positive role in upregulating the expression of p21(WAF) in a p53-independent manner (PC-3 cells are p53 null). Collectively, the above findings support the idea that UPR could be an important mechanism in mediating the anticancer activity of selenium.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • CDC2 Protein Kinase / genetics
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Cyclin-Dependent Kinase Inhibitor p21 / genetics
  • Endoplasmic Reticulum / metabolism
  • Heat-Shock Proteins / physiology*
  • Humans
  • Male
  • Molecular Chaperones / physiology*
  • Organoselenium Compounds / pharmacology*
  • Prostatic Neoplasms / drug therapy*
  • Prostatic Neoplasms / pathology
  • Protein Folding
  • Signal Transduction
  • Transcription Factor CHOP / physiology
  • Tumor Suppressor Protein p53 / physiology*
  • eIF-2 Kinase / metabolism

Substances

  • Cyclin-Dependent Kinase Inhibitor p21
  • DDIT3 protein, human
  • Heat-Shock Proteins
  • Molecular Chaperones
  • Organoselenium Compounds
  • Tumor Suppressor Protein p53
  • Transcription Factor CHOP
  • methylselenic acid
  • PERK kinase
  • eIF-2 Kinase
  • CDC2 Protein Kinase
  • molecular chaperone GRP78