In vivo imaging of human colon cancer xenografts in immunodeficient mice using a guanylyl cyclase C--specific ligand.

Unlabelled: Guanylyl cyclase C (GC-C) is a transmembrane receptor expressed by human intestinal cells and primary and metastatic colorectal adenocarcinomas but not by extraintestinal tissues or tumors. The Escherichia coli heat-stable enterotoxin analog, STa (5--18), is a 14--amino acid peptide that selectively binds to the extracellular domain of GC-C with subnanomolar affinity. This study examined the utility of a radiolabeled conjugate of STa (5--18) to selectively target and image extraintestinal human colon cancer xenografts in vivo in nude mice.