title: The cytotoxic and pro-apoptotic activities of the novel fluoropyrimidine F10 towards prostate cancer cells are enhanced by Zn(2+) -chelation and inhibiting the serine protease Omi/HtrA2.
abstract: BACKGROUND
  Intracellular Zn(2+) levels decrease during prostate cancer progression and agents that modulate intracellular Zn(2+) are cytotoxic to prostate cancer cells by an incompletely described mechanism. F10 is a new polymeric fluoropyrimidine drug-candidate that displays strong activity with minimal systemic toxicity in pre-clinical models of prostate cancer and other malignancies. The effects of exogenous Zn(2+) or Zn(2+) chelation for enhancing F10 cytotoxicity are investigated as is the role of Omi/HtrA2, a serine protease that promotes apoptosis in response to cellular stress.
  
  
  METHODS
  To test the hypothesis that the pro-apoptotic effects of F10 could be enhanced by modulating intracellular Zn(2+) we investigated cell-permeable and cell-impermeable Zn(2+) chelators and exogenous Zn(2+) and evaluated cell viability and apoptosis in cellular models of castration-resistant prostate cancer (CRPC; PC3, C4-2). The role of Omi/HtrA2 for modulating apoptosis was evaluated by pharmacological inhibition and Western blotting.
  
  
  RESULTS
  Exogenous Zn(2+) initially reduced prostate cancer cell viability but these effects were transitory and were ineffective at enhancing F10 cytotoxicity. The cell-permeable Zn(2+) -chelator tetrakis-(2-pyridylmethl) ethylenediamine (TPEN) induced apoptosis in prostate cancer cells and enhanced the pro-apoptotic effects of F10. The pro-apoptotic effects of Zn(2+) -chelation in combination with F10 treatment were enhanced by inhibiting Omi/HtrA2 implicating this serine protease as a novel target for prostate cancer treatment.
  
  
  CONCLUSIONS
  Zn(2+) -chelation enhances the pro-apoptotic effects of F10 and may be useful for enhancing the effectiveness of F10 for treatment of advanced prostate cancer. The serine protease Omi/HtrA2 modulates Zn(2+) -dependent apoptosis in prostate cancer cells and represents a new target for treatment of CRPC. Prostate 75:360-369, 2015. © 2014 Wiley Periodicals, Inc.
authors.affiliation: Department of Cancer Biology, Wake Forest School of Medicine, Winston-Salem, North Carolina; Comprehensive Cancer Center, Wake Forest School of Medicine, Winston-Salem, North Carolina.
authors.forename: William H
authors.initials: WH
authors.lastname: Gmeiner
authors.forename: Olcay
authors.initials: O
authors.lastname: Boyacioglu
authors.forename: Christopher H
authors.initials: CH
authors.lastname: Stuart
authors.forename: Jamie
authors.initials: J
authors.lastname: Jennings-Gee
authors.forename: K C
authors.initials: KC
authors.lastname: Balaji
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D002614:Chelating Agents / Q000494:pharmacology; D005029:Ethylenediamines / Q000494:pharmacology; D005468:Fluorodeoxyuridylate / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D000074923:High-Temperature Requirement A Serine Peptidase 2; D006801:Humans; D008297:Male; D024101:Mitochondrial Proteins / Q000037:antagonists & inhibitors*; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D012697:Serine Endopeptidases; D015032:Zinc / Q000378:metabolism*
chemical_list: D002614:Chelating Agents; D005029:Ethylenediamines; C435305:FdUMP(10); D024101:Mitochondrial Proteins; D005468:Fluorodeoxyuridylate; D012697:Serine Endopeptidases; C000615914:HTRA2 protein, human; D000074923:High-Temperature Requirement A Serine Peptidase 2; D015032:Zinc; C044387:N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine
keywords: F10; Omi/HtrA2; Zn2+; castration-resistant prostate cancer; fluoropyrimidine