title: Metformin enhances the antiproliferative and apoptotic effect of bicalutamide in prostate cancer.
abstract: BACKGROUND
  Prostate cancer incidence and mortality vary dramatically by geographical location. Both are higher in developed countries. Some attribute this to westernized lifestyles of high-energy diets and limited physical activity with consequent obesity. Obesity and obesity-related diseases like diabetes cause hyperinsulinaemia, which upregulates pro-survival cell signalling. Previous work revealed diet-induced hyperinsulinaemia enhances prostate cancer xenograft growth in vivo. Metformin, an antidiabetic medication, reduces hyperinsulinaemia and also exhibits antineoplastic properties. Herein, we assess the potential additive benefit of combining bicalutamide antiandrogen therapy with metformin, in vitro and in vivo.
  
  
  METHODS
  Using clonogenic assays, we assessed the effect of bicalutamide and/or metformin on clonogenicity in prostate cancer cell lines. Western blot and cell cycle analyses were used to elucidate mechanisms of interaction between the drugs in androgen receptor (AR)-positive (LNCaP) and AR-negative (PC3) cell lines. The combination treatment regimen was assessed in vivo using an LNCaP murine xenograft model.
  
  
  RESULTS
  Micromolar bicalutamide or millimolar metformin caused a significant dose-dependent reduction in clonogenicity (P<0.001). Combination treatment further significantly reduced clonogenicity (P<0.005) with greater effects in AR-positive cells. Western blot and cell cycle analyses suggested differing mechanisms of interaction in AR-positive and -negative cell lines. Following combination treatment, LNCaP cells exhibited an altered cell proliferation (decreased phospho mammalian target of rapamycin expression) and perturbed cell cycle kinetics (G1/S cell cycle arrest). PC3 cells showed evidence of enhanced apoptosis (increased Bcl-2-associated X protein and decreased total caspase 3 expression). Markedly diminished tumour growth occurred following combination treatment in vivo (P<0.001).
  
  
  CONCLUSIONS
  Combining bicalutamide and metformin significantly reduces prostate cancer cell growth further than either monotherapy. In AR-positive cells, this effect appeared to be mediated by reducing proliferation rates, whereas in AR-negative cells the combination treatment appeared to promote apoptosis. This combination drug regimen may improve prostate-cancer-specific survival by the direct antineoplastic properties outlined.
authors.affiliation: Division of Urology, Department of Surgery, Sunnybrook Health Sciences Centre, Toronto, ON, Canada.
authors.forename: A J
authors.initials: AJ
authors.lastname: Colquhoun
authors.forename: N A
authors.initials: NA
authors.lastname: Venier
authors.forename: A D
authors.initials: AD
authors.lastname: Vandersluis
authors.forename: R
authors.initials: R
authors.lastname: Besla
authors.forename: L M
authors.initials: LM
authors.lastname: Sugar
authors.forename: A
authors.initials: A
authors.lastname: Kiss
authors.forename: N E
authors.initials: NE
authors.lastname: Fleshner
authors.forename: M
authors.initials: M
authors.lastname: Pollak
authors.forename: L H
authors.initials: LH
authors.lastname: Klotz
authors.forename: V
authors.initials: V
authors.lastname: Venkateswaran
mesh_terms: D000726:Androgen Antagonists / Q000008:administration & dosage; D000813:Anilides / Q000008:administration & dosage*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D019610:Cytoprotection / Q000187:drug effects; D004357:Drug Synergism; D006801:Humans; D007004:Hypoglycemic Agents / Q000008:administration & dosage; D008297:Male; D008687:Metformin / Q000008:administration & dosage*; D051379:Mice; D009570:Nitriles / Q000008:administration & dosage*; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000473:pathology; D014105:Tosyl Compounds / Q000008:administration & dosage*
chemical_list: D000726:Androgen Antagonists; D000813:Anilides; D007004:Hypoglycemic Agents; D009570:Nitriles; D014105:Tosyl Compounds; D008687:Metformin; C053541:bicalutamide