title: Cyclooxygenase-independent induction of p21WAF-1/cip1, apoptosis and differentiation by L-745,337, a selective PGH synthase-2 inhibitor, and salicylate in HT-29 cells.
abstract: In order to dissect out cyclooxygenase-dependent from cyclooxygenase-independent mechanisms in the antiproliferative effects of selective prostaglandin H synthase (PGHS)-2 inhibitors, we compared the effects of L-745,337 (a highly selective PGHS-2 inhibitor) with sodium salicylate (a weak PGHS inhibitor) on prostanoid production, induction of the cyclin-dependent kinase inhibitor p21WAF-1/cip1, mutant p53 (m273-p53) levels, apoptosis and differentiation in human colon adenocarcinoma HT-29 cells. L-745,337 dose-dependently suppressed the cyclooxygenase activity of HT-29 cells (IC50: 0.24 microM). Four-day treatment with L-745,337 caused a concentration-dependent inhibition of cell growth (IC50: 0.9 mM) associated with the induction of p21WAF-1/cip1 and an increase in the proportion of apoptotic nuclei (EC50: 0.1 and 0.34 mM, respectively) while reducing the levels of m273-p53 (IC50: 0.2 mM). Sodium salicylate, at the concentration of 10 mM that did not affect prostanoid formation, caused a 60% reduction of cell growth associated with a 3-fold induction of p21WAF-1/cip1 and a 60% increase in the proportion of apoptotic nuclei. Ultrastructural analysis showed that L-745,337 (0.5 mM) and sodium salicylate (10 mM) caused the induction of a differentiated phenotype. We conclude that high concentrations of L-745,337 and sodium salicylate inhibit colon cancer cell growth by a mechanism unrelated to cyclooxygenase inhibition that may involve p53-independent induction of the tumor suppressor p21WAF-1/cip1.
authors.affiliation: Department of Medicine, Division of Pharmacology, University of Chieta G. D'Annunzio School of Medicine, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Santini
authors.forename: M G
authors.initials: MG
authors.lastname: Sciulli
authors.forename: R
authors.initials: R
authors.lastname: Marinacci
authors.forename: O
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authors.lastname: Fusco
authors.forename: L
authors.initials: L
authors.lastname: Spoletini
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authors.initials: A
authors.lastname: Pace
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authors.initials: A
authors.lastname: Ricciardulli
authors.forename: C
authors.initials: C
authors.lastname: Natoli
authors.forename: A
authors.initials: A
authors.lastname: Procopio
authors.forename: J
authors.initials: J
authors.lastname: Maclouf
authors.forename: P
authors.initials: P
authors.lastname: Patrignani