title: p21(Waf1/Cip1) protects against p53-mediated apoptosis of human melanoma cells.
abstract: The tumor suppressive effect of p53 is believed to be rooted in its two primary functions: the implementation of cellular growth arrest and the execution of apoptotic cell death. While p53-regulated expression of the cyclin-dependent kinase inhibitor p21(Waf1/Cip1) appears to be central for the implementation of G1 arrest, the participation of p21(Waf1/Cip1) in p53-triggered cell death remains controversial. In the present study, overexpression of p53 in human melanoma SK-MEL-110 cells through use of an adenoviral expression vector (AdCMV.p53) was found to result in apoptosis, while similar infection of primary vascular smooth muscle cells (VSMC) instead resulted in a moderate inhibition of growth. Expression of p21(Waf1/Cip1) was strongly elevated in VSMC, but showed little change in SK-MEL-110 cells, although expression of another p53-regulated gene (GADD45) was comparable in both AdCMV.p53-infected cell types. Evidence that p21(Waf1/Cip1) expression may be required for surviving p53-induced cell death was further supported by the finding that p53 overexpression was highly toxic for p21-deficient mouse embryonal fibroblasts (p21-/- MEFs). In both SK-MEL-110 and p21-/- MEFs, adenovirus-driven ectopic expression of p21(Waf1/Cip1) resulted in a substantial protection against p53-induced apoptosis, indicating that p21(Waf1/Cip1) rescued cells from a path of programmed cell death to one of enhanced survival.
authors.affiliation: Laboratory of Cellular and Molecular Biology, National Institutes of Health, Baltimore, Maryland 21224, USA.
authors.forename: M
authors.initials: M
authors.lastname: Gorospe
authors.forename: C
authors.initials: C
authors.lastname: Cirielli
authors.forename: X
authors.initials: X
authors.lastname: Wang
authors.forename: P
authors.initials: P
authors.lastname: Seth
authors.forename: M C
authors.initials: MC
authors.lastname: Capogrossi
authors.forename: N J
authors.initials: NJ
authors.lastname: Holbrook
mesh_terms: D000818:Animals; D017209:Apoptosis; D002478:Cells, Cultured; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000502:physiology*; D015870:Gene Expression; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008545:Melanoma / Q000473:pathology*; D051379:Mice; D018345:Mice, Knockout; D011506:Proteins / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000502:physiology*; D000097642:GADD45 Proteins
chemical_list: D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D047908:Intracellular Signaling Peptides and Proteins; D011506:Proteins; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53; D000097642:GADD45 Proteins; C493956:CDKN1A protein, human; C493957:Cdkn1a protein, mouse