Abstract A01: Centrosome amplification induces autophagy and sensitizes to chloroquine

Abstract

Abstract Autophagy is a catabolic process whereby autophagosomes engulf damaged organelles and proteins and deliver these contents to the lysosome for degradation and subsequent recycling. Proper autophagosome fusion with lysosomes depends on movement along intact microtubules, which are organized by centrosomes in human cells. We have discovered that autophagy is activated by centrosome amplification (CA), a numerical increase in centrosome number. CA is common in human cancers, particularly high-risk cancers, and higher autophagy is predicted to sensitize cancer cells with CA to autophagy inhibition. To test this hypothesis, we first evaluated autophagy in 341 human breast cancers with known CA status by quantifying p62/SQSTM1. Cancers with CA demonstrated a decrease in p62 expression, consistent with elevated autophagy. Next, we evaluated autophagy using western blot and immunofluorescence in two model cell lines of CA: doxycycline-inducible expression of polo-like kinase 4 (PLK4), an enzyme required for centrosome duplication. Cells with CA demonstrated elevated levels of autophagy by LC3 and p62 immunoblotting and immunofluorescence. Third, we tested autophagy inhibitors in our cell models of CA. Our results show that cells with CA are sensitized to the autophagy inhibitor chloroquine. Taken together, our results suggest that autophagy is upregulated by CA. We hypothesize that CA induces autophagy by increasing the number of lysosomal hubs (lysosomes tend to cluster around centrosomes) and facilitating transport to these hubs. These findings suggest CA as a biomarker for autophagy inhibition in high-risk cancers. Citation Format: Ryan A. Denu, Mark E. Burkard. Centrosome amplification induces autophagy and sensitizes to chloroquine. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Targeting the Vulnerabilities of Cancer; May 16-19, 2016; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(1_Suppl):Abstract nr A01.