title: Protective role of p21(Waf1/Cip1) against prostaglandin A2-mediated apoptosis of human colorectal carcinoma cells.
abstract: Prostaglandin A2 (PGA2) suppresses tumor growth in vivo, is potently antiproliferative in vitro, and is a model drug for the study of the mammalian stress response. Our previous studies using breast carcinoma MCF-7 cells suggested that p21(Waf1/Cip1) induction enabled cells to survive PGA2 exposure. Indeed, the marked sensitivity of human colorectal carcinoma RKO cells to the cytotoxicity of PGA2 is known to be associated with a lack of a PGA2-mediated increase in p21(Waf1/Cip1) expression, inhibition of cyclin-dependent kinase activity, and growth arrest. To determine if cell death following exposure to PGA2 could be prevented by forcing the expression of p21(Waf1/Cip1) in RKO cells, we utilized an adenoviral vector-based expression system. We demonstrate that ectopic expression of p21(Waf1/Cip1) largely rescued RKO cells from PGA2-induced apoptotic cell death, directly implicating p21(Waf1/Cip1) as a determinant of the cellular outcome (survival versus death) following exposure to PGA2. To discern whether p21(Waf1/Cip1)-mediated protection operates through the implementation of cellular growth arrest, other growth-inhibitory treatments were studied for the ability to attenuate PGA2-induced cell death. Neither serum depletion nor suramin (a growth factor receptor antagonist) protected RKO cells against PGA2 cytotoxicity, and neither induced p21(Waf1/Cip1) expression. Mimosine, however, enhanced p21(Waf1/Cip1) expression, completely inhibited RKO cell proliferation, and exerted marked protection against a subsequent PGA2 challenge. Taken together, our results directly demonstrate a protective role for p21(Waf1/Cip1) during PGA2 cellular stress and provide strong evidence that the implementation of cellular growth arrest contributes to this protective influence.
authors.affiliation: Laboratory of Cellular and Molecular Biology, National Institute on Aging, National Institutes of Health, Baltimore, Maryland 21224, USA.
authors.forename: M
authors.initials: M
authors.lastname: Gorospe
authors.forename: X
authors.initials: X
authors.lastname: Wang
authors.forename: K Z
authors.initials: KZ
authors.lastname: Guyton
authors.forename: N J
authors.initials: NJ
authors.lastname: Holbrook
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D002277:Carcinoma / Q000235:genetics / Q000473:pathology*; D002455:Cell Division; D015179:Colorectal Neoplasms / Q000235:genetics / Q000473:pathology*; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000235:genetics*; D005786:Gene Expression Regulation; D006801:Humans; D011454:Prostaglandins A / Q000494:pharmacology*
chemical_list: C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D011454:Prostaglandins A; C100008:prostaglandin A2