CHEK1 and neoplasm: In view of upregulation of DNA damage repair and activation of p-CHEK1 for cell survival in Ctdnep1-deficient cells, we then treated Ctdnep1-cKO tumor cells with prexasertib, a selective inhibitor of the checkpoint kinase CHEK1 currently under multiple clinical trials; prexasertib disrupts DNA replication and prevents DNA damage repair, causing cell death by replication catastrophe67,68.