Normal colonic epithelium adheres to carcinoembryonic antigen and type IV collagen

Background/Aims: Human colorectal carcinoma cells bind to collagen and laminin in the basement membrane as well as to carcinoembryonic antigen (CEA) on neighboring cells. The purpose of this study was to determine whether normal colonie epithelial cells bind to CEA, collagen, or laminin. Methods: Intact colonic crypts were isolated from normal mucosa in 13 specimens resected for colorectal carcinoma or colonic diverticulitis. Colonocytes were released from the crypts by treatment with collagenase and deoxyribonuclease and tested for adhesion to CEA, type IV collagen, and laminin in a solid-phase adhesion assay. Results: Twelve percent to 25% of colonocytes in all specimens bound to CEA. Colonocytes from seven specimens also bound to type IV collagen, but none of the colonocyte preparations bound significantly to laminin. Monoclonal antibodies to CEA and to the hyaluronate receptor CD44 and enzymatic removal of membrane CEA blocked the adhesion of colonocytes to CEA. Conclusions: First, colonocytes use the same epitopes on CEA and CD44 as colorectal carcinoma cells to adhere to solid-phase CEA. Second, colonocytes bind to solid-phase CEA through CEA-to-CEA homophilic binding. Third, CEA and type IV collagen, but not laminin, are adhesion ligands for human colonocytes.