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First published online January 10, 2008
doi: 10.1242/10.1242/jcs.017012
Research Article |

1 Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6084, USA
2 Department of Bioengineering, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6084, USA
3 Department of Pathology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6084, USA
Author for correspondence (e-mail: rka{at}pharm.med.upenn.edu)
Accepted 25 October 2007
Integrin-mediated adhesion to substratum is required for cyclin D1 induction in mesenchymal cells, but we show here that the induction of cyclin D1 persists despite blockade of ECM-integrin signaling in MCF10A mammary epithelial cells. E-cadherin-mediated cell-cell adhesion also supports cyclin D1 induction in these cells, and the combined inhibition of both E-cadherin and integrin adhesion is required to prevent the expression of cyclin D1 mRNA and protein. Our previous studies described a pro-proliferative effect of E-cadherin in MCF10A cells, mediated by Rac, and we now show that Rac is required for cyclin D1 mRNA induction by both E-cadherin and integrin engagement. The levels of p21Cip1 and p27Kip1, Cdk inhibitors that are also targets of integrin signaling, are not affected by E-cadherin-mediated cell-cell adhesion. Finally, we show that the increased expression of cyclin D1 mRNA associated with E-cadherin-dependent cell-cell adhesion is causally linked to an increased entry into S phase. Our results identify Rac signaling to cyclin D1 as a crucial pro-proliferative effect of E-cadherin-mediated cell-cell adhesion.
Key words: G1 phase, Cell cycle, Proliferation
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