title: Potential role of WAF1/Cip1/p21 as a mediator of TGF-beta cytoinhibitory effect.
abstract: Transforming growth factor-beta (TGF-beta) inhibits cell cycle progression of many types of human cells by arresting them in the G1 phase of the cell cycle. The arrest is mediated through interactions of various cyclin-dependent protein kinases (CDKs) and their inhibitors. We demonstrate that treatment with TGF-beta induces increased levels of WAF1/Cip1/p21, a potent inhibitor of various cyclin-CDK kinase activities, in two colon cancer cell lines (LS1034 and LS513), which are sensitive to TGF-beta-induced growth arrest. The induction in at least one of these cell lines (LS1034,p53-) is p53-independent. No WAF1 induction was observed after TGF-beta treatment in a third cell line (HT-29), which is completely insensitive to the cytoinhibitory effect of TGF-beta. In both LS513 and LS1034, WAF1 induction correlated with reduced cyclin E-associated kinase activity in vitro and suppression of the retinoblastoma susceptibility gene (Rb) protein phosphorylation in vivo. In addition, WAF1 was physically associated with cyclin E in the two sensitive cell lines. These results suggest that WAF1/Cip1/p21 is a mediator of cellular sensitivity to TGF-beta.
authors.affiliation: Laboratory of Radiobiology, Harvard School of Public Health, Boston, Massachusetts 02115.
authors.forename: C Y
authors.initials: CY
authors.lastname: Li
authors.forename: L
authors.initials: L
authors.lastname: Suardet
authors.forename: J B
authors.initials: JB
authors.lastname: Little
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D015152:Blotting, Northern; D015153:Blotting, Western; D002453:Cell Cycle / Q000187:drug effects / Q000528:radiation effects; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D003110:Colonic Neoplasms; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors*; D016213:Cyclins / Q000096:biosynthesis* / Q000235:genetics; D017931:DNA Primers; D005091:Exons; D016158:Genes, p53; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D006656:Protamine Kinase / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D016160:Retinoblastoma Protein / Q000032:analysis / Q000096:biosynthesis; D013997:Time Factors; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
chemical_list: C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D017931:DNA Primers; D012333:RNA, Messenger; D016160:Retinoblastoma Protein; D016212:Transforming Growth Factor beta; D006656:Protamine Kinase; D018844:Cyclin-Dependent Kinases