Mitotic bypass and endocycling promote cancer cell survival after genotoxic chemotherapy

Genotoxic chemotherapies are central components of the treatment regimen for most cancers but are rarely curative. Drug-tolerant persister cells (DTPs) evade cell death during these treatments by accessing transient adaptive states and can contribute to cancer progression after treatment. Here, we demonstrate that cancer cells can survive genotoxic chemotherapy-induced stress by accessing a DTP state wherein stress-induced bypass of mitosis precipitates continued endocycling which promotes survival by allowing cells to evade mitotic catastrophe and cell death. Mechanistic studies indicate that persistent DNA damage signaling in endocycling persister cells triggers sustained p53-independent CDK1 inhibition by WEE1 and Myt1. Continued survival in endocycling persisters is dependent on activation of this G2 checkpoint, and disrupting WEE1 or Myt1 activity using clinical-stage small molecule inhibitors is sufficient to drive CDK1 reactivation, forcing mitotic entry, catastrophe, and cell death. Our results define endocycling DTPs as targetable mediators of cancer cell persistence after genotoxic therapy.