p27Kip1 mediates addiction of ovarian cancer cells to MYCC (c-MYC) and their dependence on MYC paralogs

Tulsiram Prathapam, Alexey Aleshin, Yinghui Guan, Joe W. Gray, G. Steven Martin

Research output: Contribution to journalArticle

8 Scopus citations

Abstract

The MYCC (c-MYC) gene is amplified in 30-60% of human ovarian cancers. We assessed the functional significance of MYCC amplification by siRNA inhibition of MYCC or MYC paralogs in a panel of ovarian cancer cell lines expressing varying levels of MYCC. Inactivation of MYCC inhibited cell proliferation and induced replicative senescence only in lines with amplified MYCC, indicating that these cells are addicted to continued MYCC overexpression. In contrast, siRNA knockdown of all three MYC isoforms inhibited proliferation of MYCC nonamplified ovarian cancer cells without inducing replicative senescence, and did not inhibit the proliferation of telomerase-immortalized ovarian surface epithelial cells. The arrest induced by MYCC knockdown was accompanied by an increase in the level of the Cdk inhibitor p27Kip1 and a decrease in cyclin A expression and Cdk2 activity, and could be reversed by RNAi knockdown of p27Kip1 or Rb, or by overexpression of cyclin A/Cdk2. The arrest induced by knockdown of all three MYC isoforms could similarly be reversed by p27Kip1 knockdown. Our findings indicate that the addiction of MYCC-amplified ovarian cancer cells to MYCC differs from the dependence of MYCC non-amplified cancer cells on MYC paralogs, but both are mediated, at least in part, by p27Kip1. They also suggest that growth of ovarian cancers may be blocked by inhibition of MYCC or MYC paralogs.

Original languageEnglish (US)
Pages (from-to)32529-32538
Number of pages10
JournalJournal of Biological Chemistry
Volume285
Issue number42
DOIs
StatePublished - Oct 15 2010

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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