CHEK1 and head and neck squamous cell carcinoma: Moreover, it has been previously shown that alternative Chk1 inhibitors (PF-00477736, LY2606368, CCT244747 and MK-8776) plus some limited evidence using the Wee1 inhibitor MK-1775 can effectively radiosensitise HNSCC cells to X-ray radiation [9, 11, 12, 25–29].