CCKBR and pancreatic ductal adenocarcinoma: The pancreatic ductal adenocarcinoma (PDAC) constitutively expresses the G protein-coupled cholecystokinin B receptor (CCKBR) and dual SELEX selection against ‘exposed’ CCKBR peptides, and CCKBR-expressing PDAC cells screens for the biofouling of AP1153 to the surface of fluorescent particles, greatly facilitating the delivery of nanoparticles to PDAC cells in vivo [118].