Targeting genotoxic and proteotoxic stress-response pathways in human prostate cancer by clinically available PARP inhibitors, vorinostat and disulfiram

Prostate. 2019 Mar;79(4):352-362. doi: 10.1002/pros.23741. Epub 2018 Nov 29.

Abstract

Background: Castration-resistant prostate cancer (PCa) represents a serious health challenge. Based on mechanistically-supported rationale we explored new therapeutic options based on clinically available drugs with anticancer effects, including inhibitors of PARP1 enzyme (PARPi), and histone deacetylases (vorinostat), respectively, and disulfiram (DSF, known as alcohol-abuse drug Antabuse) and its copper-chelating metabolite CuET that inhibit protein turnover.

Methods: Drugs and their combination with ionizing radiation (IR) were tested in various cytotoxicity assays in three human PCa cell lines including radio-resistant stem-cell like derived cells. Mechanistically, DNA damage repair, heat shock and unfolded protein response (UPR) pathways were assessed by immunofluorescence and immunoblotting.

Results: We observed enhanced sensitivity to PARPi/IR in PC3 cells consistent with lower homologous recombination (HR) repair. Vorinostat sensitized DU145 cells to PARPi/IR and decreased mutant p53. Vorinostat also impaired HR-mediated DNA repair, as determined by Rad51 foci formation and downregulation of TOPBP1 protein, and overcame radio-resistance of stem-cell like DU145-derived cells. All PCa models responded well to CuET or DSF combined with copper. We demonstrated that DSF interacts with copper in the culture media and forms adequate levels of CuET indicating that DSF/copper and CuET may be considered as comparable treatments. Both DSF/copper and CuET evoked hallmarks of UPR in PCa cells, documented by upregulation of ATF4, CHOP and phospho-eIF2α, with ensuing heat shock response encompassing activation of HSF1 and HSP70. Further enhancing the cytotoxicity of CuET, combination with an inhibitor of the anti-apoptotic protein survivin (YM155, currently undergoing clinical trials) promoted the UPR-induced toxicity, yielding synergistic effects of CuET and YM155.

Conclusions: We propose that targeting genotoxic and proteotoxic stress responses by combinations of available drugs could inspire innovative strategies to treat castration-resistant PCa.

Keywords: PARP; disulfiram; prostate cancer; proteotoxic stress; vorinostat.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line, Tumor
  • DNA Repair / drug effects
  • Disulfiram / therapeutic use*
  • Gene Expression Regulation, Neoplastic / drug effects
  • Humans
  • Male
  • Molecular Targeted Therapy / methods
  • PC-3 Cells
  • PTEN Phosphohydrolase / genetics
  • Poly(ADP-ribose) Polymerase Inhibitors / therapeutic use*
  • Prostatic Neoplasms / drug therapy*
  • Radiation Tolerance
  • Recombinational DNA Repair / drug effects
  • Stress, Physiological / drug effects
  • Stress, Physiological / genetics
  • Tumor Suppressor Protein p53 / genetics
  • Vorinostat / therapeutic use*

Substances

  • Poly(ADP-ribose) Polymerase Inhibitors
  • Tumor Suppressor Protein p53
  • Vorinostat
  • PTEN Phosphohydrolase
  • PTEN protein, human
  • Disulfiram