title: The cyclin-dependent kinase inhibitor p21CIP/WAF is a positive regulator of insulin-like growth factor I-induced cell proliferation in MCF-7 human breast cancer cells.
abstract: To study the role of IGF-I receptor signaling on cell cycle events we utilized MCF-7 breast cancer cells. IGF-I at physiological concentrations increased the level of p21CIP/WAF mRNA after 4has well as protein after 8hby 10- and 6-fold, respectively, in MCF-7 cells. This IGF-1 effect was reduced by 50% in MCF-7-derived cells (SX13), which exhibit a 50% reduction in IGF-1R expression, demonstrating that IGF-1 receptor activation was involved in this process. Preincubation with the ERK1/2 inhibitor U0126 significantly reduced the IGF-1 effect on the amount of p21CIP/WAF protein in MCF-7 cells. These results were confirmed by the expression of a dominant negative construct for MEK-1 suggesting that the increase of the abundance of p21CIP/WAF in response to IGF-1 occurs via the ERK1/2 mitogen-activated protein kinase pathway. Using an antisense strategy, we demonstrated that abolition of p21CIP/WAF expression decreased by 2-fold the IGF-1 effect on cell proliferation in MCF-7. This latter result is explained by a delay in G1 to S cell cycle progression due partly to a reduction in the activation of some components of cell cycle including the induction of cyclin D1 expression in response to IGF-1. MCF-7 cells transiently overexpressing p21 showed increased basal and IGF-I-induced thymidine incorporation. Taken together, these results define p21CIP/WAF as a positive regulator in the cell proliferation induced by IGF-1 in MCF-7 cells.
authors.affiliation: Section on Molecular and Cellular Physiology, Diabetes Branch, NIDDK, National Institutes of Health, Bethesda, Maryland 20892-1758, USA.
authors.forename: Joëlle
authors.initials: J
authors.lastname: Dupont
authors.forename: Michael
authors.initials: M
authors.lastname: Karas
authors.forename: Derek
authors.initials: D
authors.lastname: LeRoith
mesh_terms: D001943:Breast Neoplasms / Q000473:pathology*; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D019938:Cyclin D1 / Q000378:metabolism; D051358:Cyclin-Dependent Kinase 4; D051361:Cyclin-Dependent Kinase 6; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D016213:Cyclins / Q000502:physiology*; D005260:Female; D016193:G1 Phase / Q000187:drug effects; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology; D010766:Phosphorylation; D011518:Proto-Oncogene Proteins; D016372:RNA, Antisense / Q000494:pharmacology; D016160:Retinoblastoma Protein / Q000378:metabolism
chemical_list: C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D011518:Proto-Oncogene Proteins; D016372:RNA, Antisense; D016160:Retinoblastoma Protein; D019938:Cyclin D1; D007334:Insulin-Like Growth Factor I; C495900:CDK4 protein, human; C495911:CDK6 protein, human; D051358:Cyclin-Dependent Kinase 4; D051361:Cyclin-Dependent Kinase 6; D018844:Cyclin-Dependent Kinases; D020928:Mitogen-Activated Protein Kinases