Non-malignant and tumor-derived cells differ in their requirement for p27Kip1 in transforming growth factor-beta-mediated G1 arrest.
Transforming growth factor beta (TGF-beta) induces G(1) arrest in susceptible cells by multiple mechanisms that inhibit the G(1) cyclin-dependent kinases (Cdks), including Cdk2, Cdk4, and Cdk6. TGF-beta treatment of early passage finite lifespan human mammary epithelial cells (HMECs) led to an accumulation of p27(Kip1) in cyclin E1-Cdk2 complexes and kinase inhibition. The requirement for p27 in the G(1) arrest by TGF-beta was assessed by transfection of antisense p27 (ASp27) oligonucleotides into TGF-beta-treated HMECs. Despite a reduction in total and cyclin E-Cdk2 bound p27 after ASp27 transfection, HMECs remained arrested in the G(1) phase. Maintenance of the G(1) arrest was accompanied by increased association of the Cdk inhibitor p21(WAF-1/Cip-1) and the retinoblastoma family member p130(Rb2) in cyclin E1-Cdk2 complexes along with kinase inhibition. In contrast to the findings in HMECs, p27 was essential for G(1) arrest by TGF-beta in two tumor-derived lines. ASp27 transfection into two TGF-beta-responsive, cancer-derived lines was not associated with increased compensatory binding of p21 and p130 to cyclin E1-Cdk2, and these cell lines failed to maintain G(1) arrest despite the continued presence of TGF-beta. Progressive cell cycle deregulation leading to impaired checkpoint controls during malignant tumor progression may alter the role of p27 from a redundant to an essential inhibitor of G(1)-to-S phase progression.
Department of Molecular and Cell Biology, Sunnybrook & Women's College Health Sciences Centre, Toronto, Ontario M4N 3M5, Canada.
Jeffrey C H
JC
Donovan
Jeffrey M
JM
Rothenstein
Joyce M
JM
Slingerland
D042846:CDC2-CDC28 Kinases; D018797:Cell Cycle Proteins / Q000032:analysis; D019938:Cyclin D1 / Q000032:analysis; D019927:Cyclin E / Q000032:analysis; D051357:Cyclin-Dependent Kinase 2; D050762:Cyclin-Dependent Kinase Inhibitor p15; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000032:analysis; D018844:Cyclin-Dependent Kinases / Q000032:analysis; D016193:G1 Phase / Q000187:drug effects*; D006801:Humans; D008840:Microfilament Proteins / Q000032:analysis / Q000502:physiology*; D009124:Muscle Proteins; D010750:Phosphoproteins / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000032:analysis; D011506:Proteins; D050717:Retinoblastoma-Like Protein p130; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins
C493966:CDKN2B protein, human; D018797:Cell Cycle Proteins; D019927:Cyclin E; D050762:Cyclin-Dependent Kinase Inhibitor p15; D019941:Cyclin-Dependent Kinase Inhibitor p16; D008840:Microfilament Proteins; D009124:Muscle Proteins; D010750:Phosphoproteins; D011506:Proteins; C493837:RBL2 protein, human; D050717:Retinoblastoma-Like Protein p130; C058992:Tagln protein, mouse; D016212:Transforming Growth Factor beta; D025521:Tumor Suppressor Proteins; D019938:Cyclin D1; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases