title: Cyclooxygenase-2, player or spectator in cyclooxygenase-2 inhibitor-induced apoptosis in prostate cancer cells.
abstract: BACKGROUND
  The antitumor activity of cyclooxygenase-2 (COX-2) inhibitors is thought to involve COX-2 enzyme inhibition and apoptosis induction, but it is unclear whether COX-2 inhibition is required for apoptosis. Different COX-2 inhibitors have similar IC(50) values (concentration for 50% inhibition) for COX-2 inhibition but differ considerably in their abilities to induce apoptosis, suggesting the involvement of a COX-2-independent pathway in apoptosis. To test this hypothesis, we investigated the effect of COX-2 depletion on apoptosis and performed a structure-activity analysis of the COX-2 inhibitor celecoxib in the androgen-independent prostate cancer cell line PC-3.
  
  
  METHODS
  Tetracycline-inducible (Tet-On) COX-2 antisense clones were isolated to assess the effect of COX-2 expression on cell viability and sensitivity to apoptosis induced by COX-2 inhibitors. Untreated Tet-On clones differentially expressed COX-2, and doxycycline-treated clones were depleted of COX-2. We synthesized and characterized various celecoxib derivatives with various COX-2 inhibitory activities and determined their apoptotic activity in PC-3 cells. Apoptosis was assessed with four tests.
  
  
  RESULTS
  In contrast to the effect of COX-2 inhibitors, which induced apoptosis, COX-2 depletion did not induce cell death. Susceptibility to COX-2 inhibitor-induced apoptosis was independent of the level of COX-2 expression. Structure-activity analysis found no correlation between apoptosis induction and COX-2 inhibition. Some celecoxib derivatives that lacked COX-2 inhibitory activity facilitated apoptosis and vice versa. Moreover, celecoxib and apoptosis-active celecoxib derivatives mediated cell death by inhibiting the same pathway.
  
  
  CONCLUSIONS
  We have dissociated the apoptosis-inducing activity from the COX-2 inhibitory activity by structural modifications of the COX-2 inhibitor celecoxib. This separation of activities may provide a molecular basis for the development of new classes of apoptosis-inducing agents.
authors.affiliation: Division of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, USA.
authors.forename: Xueqin
authors.initials: X
authors.lastname: Song
authors.forename: Ho-Pi
authors.initials: HP
authors.lastname: Lin
authors.forename: Amy J
authors.initials: AJ
authors.lastname: Johnson
authors.forename: Ping-Hui
authors.initials: PH
authors.lastname: Tseng
authors.forename: Ya-Ting
authors.initials: YT
authors.lastname: Yang
authors.forename: Samuel K
authors.initials: SK
authors.lastname: Kulp
authors.forename: Ching-Shih
authors.initials: CS
authors.lastname: Chen
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis; D015153:Blotting, Western; D000068579:Celecoxib; D051546:Cyclooxygenase 2; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D015232:Dinoprostone / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004318:Doxycycline / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D015151:Immunoblotting; D007211:Indoles / Q000494:pharmacology; D020128:Inhibitory Concentration 50; D007527:Isoenzymes / Q000037:antagonists & inhibitors* / Q000502:physiology*; D007783:Lactones / Q000494:pharmacology; D008297:Male; D008565:Membrane Proteins; D008956:Models, Chemical; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D010766:Phosphorylation; D011451:Prostaglandin-Endoperoxide Synthases / Q000502:physiology*; D011471:Prostatic Neoplasms / Q000201:enzymology*; D011720:Pyrazoles; D013329:Structure-Activity Relationship; D013449:Sulfonamides / Q000494:pharmacology; D013450:Sulfones; D013997:Time Factors; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors; D007211:Indoles; D007527:Isoenzymes; D007783:Lactones; D008565:Membrane Proteins; D016376:Oligonucleotides, Antisense; D011720:Pyrazoles; D013449:Sulfonamides; D013450:Sulfones; C116926:rofecoxib; C007293:DAPI; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases; D000068579:Celecoxib; D015232:Dinoprostone; D004318:Doxycycline