title: Effect of cyclooxygenase-2 (COX-2) inhibitors on prostate cancer cell proliferation.
abstract: BACKGROUND
  The tricyclic cyclooxygenase-2 (COX-2) inhibitors celecoxib and rofecoxib exhibit different magnitudes of antiproliferative activity against the human prostate cancer cell lines LNCaP and PC-3. We investigated the correlation between the COX-2 inhibitory potencies, antiproliferative activities and the nature of the central ring system of novel tricyclic COX-2 inhibitors belonging to the diarylcycloalkyl and diarylheterocyclic classes possessing a central 3-membered cyclopropyl (1 and 2), a 5-membered isoxazoline (3), an isoxazole (4) or 2-(5H) furanone (5), and a 6-membered pyran-2-one (6a-c) ring system.
  
  
  METHODS
  Novel tricyclics were synthesized and evaluated in vitro for their COX-1/COX-2 inhibitory activities and their abilities to inhibit cell proliferation in prostate (AT3B-1, PC-3 and LNCaP) and breast (MCF-7) cancer cell lines. A molecular modeling study was carried out to characterize the electronic nature of the central ring systems of the novel tricyclic COX-2 inhibitors.
  
  
  RESULTS
  The isoxazoline (3), which exhibited excellent COX-2 inhibitory potency and selectivity, showed growth inhibition in all the cell lines tested with IC50 values of 349 microM (AT3B-1), 378 microM (PC-3), 100 microM (LNCaP) and 200 microM (MCF-7), respectively. The rofecoxib analog (5) and 6-membered pyran-2-ones (6a-c) showed weak inhibition (MCF-7, AT3-B-1 and PC-3) inspite of possessing good COX-2 inhibitory potencies and selectivities.
  
  
  CONCLUSIONS
  This study demonstrates that the antiproliferative activity profiles exhibited by the novel tricyclic COX-2 inhibitors is dependent on the electronic nature of the central ring system and is independent of their COX-2 inhibitory potencies and selectivities. Accordingly, the 2,3-dimethyl-5-(4-methylsulfonylphenyl)-4-phenyl-4-isoxazoline (3), which possesses an electron rich central 5-membered isoxazole ring, could serve as a lead compound to develop novel drugs to treat prostate cancer.
authors.affiliation: Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Canada T6G 2N8.
authors.forename: P
authors.initials: P
authors.lastname: Srinath
authors.forename: P N
authors.initials: PN
authors.lastname: Rao
authors.forename: Edward E
authors.initials: EE
authors.lastname: Knaus
authors.forename: M R
authors.initials: MR
authors.lastname: Suresh
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D051546:Cyclooxygenase 2; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D006571:Heterocyclic Compounds / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D020128:Inhibitory Concentration 50; D007527:Isoenzymes / Q000037:antagonists & inhibitors*; D008297:Male; D008565:Membrane Proteins; D008958:Models, Molecular; D011451:Prostaglandin-Endoperoxide Synthases; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D051381:Rats; D055672:Static Electricity
chemical_list: D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors; D006571:Heterocyclic Compounds; D007527:Isoenzymes; D008565:Membrane Proteins; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases