CLDN1 and adenoma: Based on known biology relevant to cancer, the availability of known ligands, known structure activity relationships, or the level and breadth of expression in adenomas and adenocarcinomas relative to normal colon, six of the putative cell surface markers were selected for further validation by confirmation of protein expression in patient samples: CLDN1, GPR56, GRM8, LY6G6D/F, SLCO1B1/3/7 and TLR4. LY6G6D was not distinguished from LY6G6F by the Affymetrix probes.