CHEK1 and cancer: We observed that AZD1775 and dl922-947, both alone and in combination, activated the DDR pathway, as indicated by the increase in expression of γ-H2AX, phospho-RPA32 Ser 4/Ser 8, and phospho-CHK1 Ser 345, and in line with what was previously found in other cancer cell types [27,28,44,68,69,70,71,72,73].