Based on the evidence that the G protein-coupled cholecystokinin B receptor (CCKBR) is constitutively overexpressed on the surface of human pancreatic cancer cells, and plays a role in tumor cell proliferation [108], Clawson et al. identified and characterized high-affinity DNA aptamers to the CCKBR, and reported the efficacy of delivering diagnostic or therapeutic agents to pancreatic cancer cells with minimal side effects, using dual SELEX selection from a pool of multiple DNA aptamers [109]. Here, CCKBR is linked to familial pancreatic carcinoma.