Abstract 1751: The E2F activators signal centrosome amplification in breast cancer cells through centrosome regulatory molecules.

Abstract

Abstract Based on the elevated frequencies of centrosome amplification in premalignant breast lesions and in breast tumors, centrosome amplification is proposed to play a role in breast tumorigenesis. The coordination between cell and centrosome cycles is of paramount importance to maintain genomic stability and to the prevention of mammary tumorigenesis. Thus, both cell cycle regulators and molecules that regulate centrosome duplication work together to prevent abnormal centrosome duplication. E2Fs are transcription factors that regulate various cellular processes, such as DNA replication, DNA repair, cell proliferation and apoptosis; their role on centrosomal and mitotic regulation is understood poorly. We hypothesize that the E2F activators (E2F1, E2F2, E2F3a) play key roles in regulating centrosome amplification in HER2 positive breast cancer cells. We found that the E2Fs activators are deregulated or overexpressed in HER2 positive breast cancer cells displaying centrosome amplification, since serum withdrawal does not downregulate the E2F activators (which occurs in control MCF10A cells upon serum-withdrawal). Upregulated E2Fs correlated with the transcriptional overexpression of cell cycle and centrosome regulatory targets, including cylin D, cyclin E, Nek2 and Plk4. Knockdown of E2Fs in HER2 positive cells decreased centrosome amplification without affecting the cell cycle, or entry into S phase. The chromatin immunoprecipitation (ChIP) assay showed binding of E2F1, E2F2 and E2F3 into the promoter of Nek2 and between exons 1 and 2 of Plk4. In two out of three of the Her2+ breast cancer cell lines displaying centrosome amplification, extinguishing E2F expression leads to downregulation of Nek2 and cyclin D1 -potent inducers of centrosome amplification-. In conclusion, centrosome amplification in Her2+ breast cancer cells is dependent on the E2Fs activators and is mediated by molecules that play critical roles in centrosome duplication. We have identified a novel mechanism where E2F-generated centrosome amplification may contribute to breast carcinogenesis. Citation Format: Mi-Young Lee, Harold Ivan Saavedra. The E2F activators signal centrosome amplification in breast cancer cells through centrosome regulatory molecules. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1751. doi:10.1158/1538-7445.AM2013-1751