title: P53-mediated induction of Cox-2 counteracts p53- or genotoxic stress-induced apoptosis.
abstract: The identification of transcriptional targets of the tumor suppressor p53 is crucial in understanding mechanisms by which it affects cellular outcomes. Through expression array analysis, we identified cyclooxygenase 2 (Cox-2), whose expression was inducible by wild-type p53 and DNA damage. We also found that p53-induced Cox-2 expression results from p53-mediated activation of the Ras/Raf/MAPK cascade, as demonstrated by suppression of Cox-2 induction in response to p53 by dominant-negative Ras or Raf1 mutants. Furthermore, heparin-binding epidermal growth factor-like growth factor (HB- EGF), a p53 downstream target gene, induced Cox-2 expression, implying that Cox-2 is an ultimate effector in the p53-->HB-EGF-->Ras/Raf/MAPK-->Cox-2 pathway. p53-induced apoptosis was enhanced greatly in Cox-2 knock-out cells as compared with wild-type cells, suggesting that Cox-2 has an abrogating effect on p53-induced apoptosis. Also, a selective Cox-2 inhibitor, NS-398, significantly enhanced genotoxic stress-induced apoptosis in several types of p53+/+ normal human cells, through a caspase-dependent pathway. Together, these results demonstrate that Cox-2 is induced by p53-mediated activation of the Ras/Raf/ERK cascade, counteracting p53-mediated apoptosis. This anti-apoptosis effect may be a mechanism to abate cellular stresses associated with p53 induction.
authors.affiliation: Cancer Biology Program, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Jeong A
authors.initials: JA
authors.lastname: Han
authors.forename: Jong-Il
authors.initials: JI
authors.lastname: Kim
authors.forename: Pat P
authors.initials: PP
authors.lastname: Ongusaha
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Hwang
authors.forename: Leslie R
authors.initials: LR
authors.lastname: Ballou
authors.forename: Alka
authors.initials: A
authors.lastname: Mahale
authors.forename: Stuart A
authors.initials: SA
authors.lastname: Aaronson
authors.forename: Sam W
authors.initials: SW
authors.lastname: Lee
mesh_terms: D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D051546:Cyclooxygenase 2; D004789:Enzyme Activation; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D006801:Humans; D007527:Isoenzymes / Q000235:genetics* / Q000502:physiology; D008565:Membrane Proteins; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009153:Mutagens / Q000494:pharmacology*; D011451:Prostaglandin-Endoperoxide Synthases / Q000235:genetics* / Q000502:physiology; D016159:Tumor Suppressor Protein p53 / Q000502:physiology*
chemical_list: D007527:Isoenzymes; D008565:Membrane Proteins; D009153:Mutagens; D016159:Tumor Suppressor Protein p53; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases; D020928:Mitogen-Activated Protein Kinases