Centrosome amplification, the acquisition of three or more centrosomes, results in defective spindles, multipolar mitosis and aneuploidy. Aneuploidy generates a plethora of genetic alterations that culminates in cancer initiation and promotion. Centrosome amplification is present in most human tumors, including 80-90% human breast cancers and precursor mammary lesions. How that centrosome amplification arises is based on correlative evidence;for example, human breast cancers over-expressing Her2 (30% of all human cancers) have high frequencies of centrosome amplification. In addition, many altered gene products involved in human cancers result in centrosome amplification and chromosome instability in cell culture. Our published results showed that Ras induced centrosome amplification through the MAPK pathway in cultured cells. Our preliminary data showed that Ras, but not c-Myc induces centrosome amplification in precursor mammary lesions. Expression assays showed that human and mouse mammary epithelial cells expressing Her2, or Ras display ectopically expressed cyclin D1 and Nek2. Down-regulation of cyclinD1, Cdk4 and Nek-2 prevent Her2 and Ras- dependent centrosome amplification. We propose the following hypothesis: The Her2/Ras pathway trigger centrosome amplification and mammary tumor initiation by through a classical pathway involving Cdk4 phosphorylation of NPM, and through an alternative pathway involving ectopically-expressed Nek2.
In specific aim 1 we will distinguish between a classical and an alternative pathway to centrosome amplification.
In specific aim 2 we will assess how the alternative pathway impinges on centrosome amplification.
Specific aim 3 will address how interfering with the classical pathway in vivo prevents centrosome amplification in pre-malignancy and suppresses mammary tumorigenesis.

Public Health Relevance

Because most human cancers harbor centrosome amplification, identifying oncogene-deregulated centrosomal targets mediating centrosome amplification will provide the groundwork to patient treatment with existing or developing inhibitors specific to those mediators, including Cdk4, NPM and Nek2. Those inhibitors will prevent the centrosome amplification and aneuploidy responsible for tumor initiation and progression to malignancy.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA151521-04
Application #
8447579
Study Section
Molecular Oncogenesis Study Section (MONC)
Program Officer
Hildesheim, Jeffrey
Project Start
2010-07-01
Project End
2015-04-30
Budget Start
2013-05-01
Budget End
2014-04-30
Support Year
4
Fiscal Year
2013
Total Cost
$291,697
Indirect Cost
$102,498
Name
Emory University
Department
Radiation-Diagnostic/Oncology
Type
Schools of Medicine
DUNS #
066469933
City
Atlanta
State
GA
Country
United States
Zip Code
30322
Marina, Mihaela; Saavedra, Harold I (2014) Nek2 and Plk4: prognostic markers, drivers of breast tumorigenesis and drug resistance. Front Biosci (Landmark Ed) 19:352-65
Lee, Mi-Young; Moreno, Carlos S; Saavedra, Harold I (2014) E2F activators signal and maintain centrosome amplification in breast cancer cells. Mol Cell Biol 34:2581-99
Harrison Pitner, Mary Kathryn; Saavedra, Harold I (2013) Cdk4 and nek2 signal binucleation and centrosome amplification in a her2+ breast cancer model. PLoS One 8:e65971
Zeng, X; Shaikh, F Y; Harrison, M K et al. (2010) The Ras oncogene signals centrosome amplification in mammary epithelial cells through cyclin D1/Cdk4 and Nek2. Oncogene 29:5103-12