title: Nitrogen containing bisphosphonates induce apoptosis and inhibit the mevalonate pathway, impairing Ras membrane localization in prostate cancer cells.
abstract: OBJECTIVE
  Metastasis to bone is an important cause of morbidity in advanced prostate cancer. Despite the typically sclerotic nature of prostatic bone metastases osteolysis has a significant role in the pathogenesis of this disease. The nitrogen containing bisphosphonates (N-BPs), such as pamidronate and zoledronic acid, have greatly enhanced potency for inhibiting bone resorption and inducing apoptosis in osteoclasts. We investigated the effects of N-BPs on prostate cancer cells.
  
  
  METHODS
  Cell viability was determined with an MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymeyhoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) dye reduction assay. Cell cycle analysis, DNA fragmentation and caspase 3 activity were assessed using flow cytometry. Ras, Bcl-2 and Bax were quantified by Western blotting.
  
  
  RESULTS
  Pamidronate and zoledronic acid decreased cell viability in the 3 human cell lines DU145, PC3 and LNCaP. These effects were associated with changes in cell cycle distribution, induction of DNA fragmentation and a decrease in the Bcl-2-to-Bax ratio, which are features of apoptotic cell death. Pre-incubation with caspase inhibitors attenuated the effects of zoledronic acid and caspase 3 activity was demonstrated in treated DU145 cells. Zoledronic acid induced loss of cell viability in DU145 cells was prevented by co-treatment with farnesol, suggesting that N-BPs cause inhibition of the mevalonate pathway and Ras prenylation. A decrease in active, membrane bound Ras in zoledronic acid treated DU145 cells was shown by Western blot analysis.
  
  
  CONCLUSIONS
  N-BPs induce apoptosis in prostate cancer via a caspase dependent mechanism. They have effects on protein prenylation via inhibition of the mevalonate pathway and impair membrane localization of Ras in prostate cancer cells.
authors.affiliation: Department of Urology, St. George's Hospital and Medical School, First Floor, Ingleby House, Blackshaw Road, London SW17 0QT, UK.
authors.forename: Grenville M
authors.initials: GM
authors.lastname: Oades
authors.forename: Siddhika G
authors.initials: SG
authors.lastname: Senaratne
authors.forename: Ian A
authors.initials: IA
authors.lastname: Clarke
authors.forename: Roger S
authors.initials: RS
authors.lastname: Kirby
authors.forename: Kay W
authors.initials: KW
authors.lastname: Colston
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D053938:DNA Fragmentation / Q000187:drug effects; D004164:Diphosphonates / Q000494:pharmacology*; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D008297:Male; D008798:Mevalonic Acid / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000077268:Pamidronate; D011471:Prostatic Neoplasms / Q000378:metabolism / Q000503:physiopathology*; D017368:Protein Prenylation / Q000187:drug effects; D000077211:Zoledronic Acid; D018631:ras Proteins / Q000378:metabolism*
chemical_list: D000970:Antineoplastic Agents; D004164:Diphosphonates; D007093:Imidazoles; D000077211:Zoledronic Acid; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D018631:ras Proteins; D000077268:Pamidronate; D008798:Mevalonic Acid