Non-malignant and Tumor-derived Cells Differ in Their Requirement for p27Kip1 in Transforming Growth Factor-β-mediated G1 Arrest

• Published in: The Journal of biological chemistry Vol. 277; no. 44; p. 41686
• Main Authors: Jeffrey C. H. Donovan, Jeffrey M. Rothenstein, Joyce M. Slingerland
• Format: Journal Article
• Language: English
• Published: American Society for Biochemistry and Molecular Biology 01-11-2002
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M204307200

Transforming growth factor β (TGF-β) 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-β 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-β was assessed by transfection of antisense p27 (ASp27) oligonucleotides into TGF-β-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-β in two tumor-derived lines. ASp27 transfection into two TGF-β-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-β. 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.