Panc1 Mia PaCa2, and BxPC3 pancreatic ductal adenocarcinoma and the human embryonic kidney (HEK293) cell lines were purchased from American Type Culture Collection and used within six months of attainment. No additional authentication was performed on the cell lines following receipt. The human keratinocyte HaCat cell line was a gift from James Elder (University of Michigan). The ATM inhibitor KU55933 was provided by Graeme Smith (Cambridge University) and the Chk1/2 inhibitor AZD7762 by Meredith Morgan (University of Michigan). The MK2 inhibitor was purchased from EMD (Darmstadt, Germany) and the p38 inhibitor SB203580 from Cell Signaling Technology (Beverly, MA), the complementary DNA of human ATDC (provided by John Murnane, University of California, San Franscisco). ATDC mutants were generated using the QuikChange® II XL Site-Directed Mutagenesis Kit (Stratagene, La Jolla, CA). HEK293 cells with stable expression of ATDC, and Panc1 and BxPC3 cells with ATDC knockdown using shRNA have been described (18 (link)).