title: IFN-gamma induction of p21(WAF1) is required for cell cycle inhibition and suppression of apoptosis.
abstract: Interferons (IFN) inhibit the growth of tumor cells by blocking the progression of their cell cycle. Recently, we showed that this cell cycle inhibition correlates with the ability of IFN to upregulate the cyclin-dependent kinase inhibitor p21(WAF1). This, however, is not proof of a causal relationship. Using p21(WAF1)-deficient cells derived from the HCT116 colon adenocarcinoma cell line, we now show that p21(WAF1) is indeed responsible for the antiproliferative effects of the type II IFN, IFN-gamma. IFN-gamma upregulated p21(WAF1) expression in a p53-independent manner, decreased cyclin-dependent kinase 2 activity, and inhibited entry into the S phase of the cell cycle in p21+/+ but not in p21-/- HCT116 cells. We additionally found that the lack of p21(WAF1) expression resulted in an increase in the ability of IFN-gamma to induce apoptosis, as reflected by an earlier induction of DNA fragmentation and caspase 3 activity in p21-/- cell. Our results indicate that p21(WAF1) expression is necessary for IFN-gamma-mediated cell cycle inhibition and suppression of IFN-gamma-induced apoptosis.
authors.affiliation: Department of Surgery, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: A C
authors.initials: AC
authors.lastname: Hobeika
authors.forename: W
authors.initials: W
authors.lastname: Etienne
authors.forename: B A
authors.initials: BA
authors.lastname: Torres
authors.forename: H M
authors.initials: HM
authors.lastname: Johnson
authors.forename: P S
authors.initials: PS
authors.lastname: Subramaniam
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D042846:CDC2-CDC28 Kinases; D002453:Cell Cycle / Q000187:drug effects*; D003110:Colonic Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D051357:Cyclin-Dependent Kinase 2; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D016213:Cyclins / Q000096:biosynthesis* / Q000172:deficiency / Q000235:genetics; D053938:DNA Fragmentation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018390:Gene Targeting; D016158:Genes, p53; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011994:Recombinant Proteins; D014407:Tumor Cells, Cultured
chemical_list: C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004791:Enzyme Inhibitors; D011994:Recombinant Proteins; D007371:Interferon-gamma; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases