title: Zoledronic acid produces antitumor effects on mesothelioma through apoptosis and S-phase arrest in p53-independent and Ras prenylation-independent manners.
abstract: BACKGROUND
  We examined whether zoledronic acid (ZOL), the third generation of bisphosphonates, produced cytotoxic effects on human mesothelioma cells in vitro and in vivo, and investigated a possible involvement of p53, Ras, and extracellular signal-regulated kinase1/2 (ERK1/2) pathways.
  
  
  METHODS
  Cytotoxicity and cell cycles were assessed with a colorimetric assay and flow cytometry, respectively. Expression levels of apoptosis-linked proteins and prenylation of small guanine-nucleotide-binding regulatory proteins were tested with p53-small interfering RNA, an ERK kinase1/2-inhibitor, and prenyl alcohols. The antitumor activity was examined in an orthotopic animal model.
  
  
  RESULTS
  ZOL treatments suppressed growth of mesothelioma cells bearing the wild-type p53 gene through apoptosis induction accompanied by activation of caspases, or S-phase arrest by up-regulated cyclin A and B1. ZOL induced p53 phosphorylation and subsequent activation of the downstream pathways. Down-regulated p53 expression with the small interfering RNA, however, showed that both apoptosis and S-phase arrest were irrelevant to the p53 activation. Geranylgeranyl but not farnesyl pyrophosphate inhibited ZOL-induced apoptosis and S-phase arrest, and the geranylgeraniol supplement decreased ZOL-mediated Rap1A but not Ras unprenylation. Inhibition of ERK1/2 pathways suppressed ZOL-induced apoptosis but not S-phase arrest. We further demonstrated that ZOL, administrated intrapleurally, inhibited the tumor growth in the pleural cavity.
  
  
  CONCLUSIONS
  These data indicate that ZOL induces apoptosis or S-phase arrest, both of which are independent of p53 activation and Ras unprenylation, and suggest that ZOL is a possible therapeutic agent to mesothelioma partly through non-Ras- and ERK1/2-mediated pathways.
authors.affiliation: Department of Biochemistry, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba, Japan.
authors.forename: Shinya
authors.initials: S
authors.lastname: Okamoto
authors.forename: Kiyoko
authors.initials: K
authors.lastname: Kawamura
authors.forename: Quanhai
authors.initials: Q
authors.lastname: Li
authors.forename: Makako
authors.initials: M
authors.lastname: Yamanaka
authors.forename: Shan
authors.initials: S
authors.lastname: Yang
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Fukamachi
authors.forename: Yuji
authors.initials: Y
authors.lastname: Tada
authors.forename: Koichiro
authors.initials: K
authors.lastname: Tatsumi
authors.forename: Hideaki
authors.initials: H
authors.lastname: Shimada
authors.forename: Kenzo
authors.initials: K
authors.lastname: Hiroshima
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kobayashi
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Tagawa
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D050071:Bone Density Conservation Agents / Q000494:pharmacology*; D020169:Caspases / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D004164:Diphosphonates / Q000494:pharmacology*; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D008654:Mesothelioma / Q000188:drug therapy* / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D054876:Prenylation / Q000187:drug effects*; D016196:S Phase / Q000187:drug effects*; D015398:Signal Transduction / Q000187:drug effects; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D000077211:Zoledronic Acid; D018631:ras Proteins / Q000378:metabolism*
chemical_list: D050071:Bone Density Conservation Agents; D004164:Diphosphonates; D007093:Imidazoles; D016159:Tumor Suppressor Protein p53; D000077211:Zoledronic Acid; C535150:MAPK1 protein, human; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020169:Caspases; D018631:ras Proteins