ATR and pancreatic ductal adenocarcinoma: In previous studies, we demonstrated that ATR/Chk1 inhibitors selectively enhanced F10 but not 5-FU cytotoxicity in human CRC cell lines [34], while inhibitors of the ATR/Chk1/Wee1 pathway enhanced CF10 but not 5-FU cytotoxicity in pancreatic ductal adenocarcinoma [35].