Direct analysis of pancreatic tumor tissue from Pdx1-Cre;LSL-KrasG12D/+;Trp53fl/+ and Pdx1-Cre;LSL-KrasG12D/+;LSL-Trp53R172H/+ mice showed that tumors had increased Ido1 expression versus normal pancreas tissue, and that certain tumors expressed high levels of Ido1 (Figures 1B and 1C). Here, IDO1 is linked to pancreatic neoplasm.