Abstract
The ErbB2 (Her2/neu epidermal growth receptor family) oncogene is overexpressed in 30% to 40% of human breast cancers. Cyclin D1 is the regulatory subunit of the holoenzyme that phosphorylates and inactivates the retinoblastoma (pRb) tumor suppressor and is an essential downstream target of ErbB2-induced tumor growth. Herein, we demonstrate that ErbB2 induces the activity of the Notch signaling pathway. ErbB2 induction of DNA synthesis, contact-independent growth, and mammosphere induction required Notch1.ErbB2-induced cyclin D1 and cyclin D1 expression was sufficient to induce Notch1 activity, and conversely, genetic deletion of Notch1 in mammary epithelial cells using floxed Notch (Notchfl/fl) mice demonstrated that cyclin D1 is induced by Notch1. Genetic deletion of cyclin D1 or small interfering RNA (siRNA) to cyclin D1-reduced Notch1 activity and reintroduction of cyclin D1 into cyclin D1-deficient cells restored Notch1 activity through the inhibition of Numb, an endogenous inhibitor of Notch1 activity. Thus, cyclin D1 functions downstream as a genetic target of Notch1, amplifies Notch1 activity by repressing Numb, and identifies a novel pathway by which ErbB2 induces Notch1 activity via the induction of cyclin D1.
Original language | English (US) |
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Pages (from-to) | 107-115 |
Number of pages | 9 |
Journal | Clinical and Translational Science |
Volume | 1 |
Issue number | 2 |
DOIs | |
State | Published - 2008 |
Keywords
- Cancer biology
- Oncogenes
- Signal transduction
ASJC Scopus subject areas
- Neuroscience(all)
- Biochemistry, Genetics and Molecular Biology(all)
- Pharmacology, Toxicology and Pharmaceutics(all)