Spindle Assembly Checkpoint Inhibition Can Resensitize p53-Null Stem Cells to Cancer Chemotherapy

TP53 mutations are common in most human cancers, but few therapeutic options for TP53-mutant tumors exist. To identify potential therapeutic options for cancer patients with TP53 mutations, we profiled 127 FDA-approved chemotherapy drugs against human embryonic stem cells (hESC) in which we engineered TP53 deletion by genome editing. We identified 27 cancer therapeutic drugs for which TP53 mutations conferred resistance; most of these drugs target DNA synthesis or topoisomerase and cause DNA damage. We then performed a genome-wide CRISPR/Cas9 knockout screen in the TP53-null hESC in the presence and absence of sublethal concentrations of cisplatin and identified 137 genes whose loss selectively resensitized the p53-null cells to this chemotherapeutic agent. Gene ontology classification of the resensitizing loci revealed significant overrepresentation of spindle checkpoint pathway genes. Moreover, we confirmed that targeting ZNF207/BuGZ sensitizes p53-null hESC to cisplatin. These data indicate that targeted inhibition of spindle assembly checkpoints (SAC) and chromosomal organizing centers may provide a way to treat p53-deficient cancer cells with standard chemotherapy drugs. Development of small-molecule inhibitors of SAC proteins may be a useful strategy for rescuing DNA-damaging chemotherapeutics in TP53-mutant cancers. SIGNIFICANCE: These findings show that inhibition of spindle assembly checkpoints and chromosomal organizing centers may provide a new way to treat p53-deficient cancer cells with standard chemotherapy drugs.