Abstract 3530: Investigating aneuploidy, CIN and mechanisms of DNA content reduction in cancer

Abstract

Abstract Chromosomal instability (CIN) is a form of genomic instability that refers to a dynamic state in which the cells are constantly changing the number and/or the structure of their chromosomes. CIN leads to aneuploidy, a state in which a cell's set of chromosomes deviates from the euploid set. Causes of aneuploidy include errors during DNA replication, mitosis and cell fusion events. Furthermore, aneuploidy has been shown to promote tumorigenesis and tumor progression, but also to reduce cell fitness or induce cell death, especially when high levels of aneuploidy are present. Nevertheless, antimitotic drugs that induce high levels of aneuploidy, such as Paclitaxel, are not always effective in the clinic. In this study, we aim to investigate the mechanisms by which cancer cells tolerate aneuploidy, to elucidate the mechanisms by which cell fusion can lead to aneuploidy and resistance to paclitaxel and to identify new targets in aneuploidy and CIN. Towards this direction, aneuploid clones of pseudo-diploid cancer cells were generated after treatment with anti-mitotic drugs and single cell sorting and were characterized by cell cycle profile, metaphase spreads and CGH or SNP profile. Furthermore, CIN was induced by inhibition of CENP-E or ATM or impairment of the SWI/ SNF complex and quantified by induction of chromosome missegregation and micronuclei formation. Interestingly, several near tetraploid clones that were isolated after anti-mitotic drug treatment, reduced their DNA content to near diploid during propagation in culture. Thus, we hypothesize that cancer cells may utilize specific mechanisms to change their DNA content and maintain tolerable levels of aneuploidy. By time-lapse microscopy, we observed that cells treated with Paclitaxel, can increase their DNA content by abortive mitosis, cytokinesis failure or by undergoing cell fusion. Interestingly, these multinucleated cells could reduce their DNA content by undergoing independent mitosis, independent nucleus catastrophe or independent nucleus separation (cell exodus). We identify cell exodus, as a potential mechanism by which cells can recover after treatment with Paclitaxel. Inhibition of ROCK pathway, that stabilizes actin filaments and prevents cellular contractility, reduced cell fusion and exodus events and delayed cell recovery after paclitaxel treatment. Finally, in order to identify new targets in CIN and aneuploidy, we setup sgRNA loss of function screening conditions in the generated CIN and aneuploid cell models and we aim to identify genes that are essential for the survival of aneuploid and/or CIN cancer cells. Citation Format: Mara Mandelia, Kostas Drosopoulos, Spiros Linardopoulos. Investigating aneuploidy, CIN and mechanisms of DNA content reduction in cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3530.