Involvement of p27(Kip1) in G1 arrest by high dose 5α-dihydrotestosterone in LNCaP human prostate cancer cells

J. Tsihlias, W. Zhang, N. Bhattacharya, M. Flanagan, L. Klotz, J. Slingerland

Research output: Contribution to journalArticle

49 Scopus citations

Abstract

The cell cycle is governed by cyclin dependent kinases (cdks), which are activated by binding of cyclins, inhibited by cdk inhibitors and regulated by phosphorylation and dephosphorylation. Exposure to high dose dihydrotestosterone (DHT) inhibits population growth of the human prostate carcinoma cell line, LNCaP. To determine the mechanism of growth arrest by high dose DHT, we assayed the changes in cell cycle profile and the cell cycle regulators that mediate these effects. Treatment of asynchronously growing LNCaP cells with 100 nM DHT caused a G1 arrest. The proportion of cells in S phase fell from 22 to 2%, while the G1 fraction rose from 74 to 92% by 24 h. Loss of phosphorylation of the retinoblastoma protein was noted and cdk4 and cyclin E/ cdk2 activities fell. Inhibition of these G1 cyclin dependent kinases was not due to loss of either cyclin or cdk proteins nor to increases in the cdk inhibitors p16(INK4A) and p21(Cip1). p21(Cip1) protein levels remained constant, and cyclin E-associated p21(Cip1) fell, suggesting that p21(Cip1) is not relevant to this form of cyclin E/cdk2 inhibition. Of note, total p27(Kip1) levels and cyclin E-associated p27(Kip1) increased as cells arrested and the amount of the CAK activated cdk2 bound to cyclin E decreased, p27(Kip1) immunodepletion experiments demonstrated that the DHT-mediated increase in p27(Kip1) was sufficient to fully saturate and inhibit target cyclin E/cdk2. The inhibition of cyclin E/cdk2 by p27(Kip1) contributes to G1 arrest of LNCaP following high dose DHT. p27(Kip1) may be a key effector of androgen dependent growth modulation in prostate cancer cells.

Original languageEnglish (US)
Pages (from-to)670-679
Number of pages10
JournalOncogene
Volume19
Issue number5
DOIs
StatePublished - Feb 3 2000
Externally publishedYes

Keywords

  • Androgen
  • Cell cycle
  • Cyclin E/cdk2
  • p27
  • Prostate cancer

ASJC Scopus subject areas

  • Cancer Research
  • Genetics
  • Molecular Biology

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