CHEK1 and head and neck squamous cell carcinoma: Prexasertib, an inhibitor of CHK1/2 (checkpoint kinase 1/2), reduced NOTCH signaling and Skp2, enhanced the in vitro and in vivo response of head and neck squamous cell carcinoma to cisplatin and radiation, in line with another study that claimed that Skp2 is a downstream target of NOTCH signaling [48,65].