CDC20 determines the sensitivity to spindle assembly checkpoint (SAC) inhibitors

Spindle assembly checkpoint (SAC) inhibitors are a recently developed class of drugs that perturb the regulation of chromosome segregation during division, induce chromosomal instability (CIN), and eventually lead to cell death. While they are currently in clinical trials for solid cancers, biomarkers to predict the response to SAC inhibitors are still lacking. We recently reported that aneuploid cancer cells are preferentially sensitive to SAC inhibition. Here, we investigated the molecular determinants of the response to SAC inhibition that underlies the differential sensitivity of aneuploid cells to these drugs. We found that this response was largely driven by the expression of CDC20, a main activator of the anaphase-promoting complex (APC/C), rather than by APC/C itself. Mechanistically, we discovered that CDC20 depletion prolonged metaphase duration, diminished mitotic errors, and reduced sensitivity to SAC inhibition. Aneuploid cells expressed high levels of CDC20 and experienced shorter metaphases and multiple mitotic errors, resulting in increased long-term sensitivity to SAC inhibition. Our findings propose high CDC20 expression as a favorable biomarker for SAC inhibition therapy and as an aneuploidy-induced therapeutic vulnerability. ### Competing Interest Statement The authors have declared no competing interest.