HUMAN ENTEROCYTE (CACO-2) MIGRATION IS MODULATED INVITRO BY EXTRACELLULAR-MATRIX COMPOSITION AND EPIDERMAL GROWTH-FACTOR

The modulation of enterocyte sheet migration was studied using Caco-2 cells, a well-differentiated human colonic cell line. Although Caco-2 cells attached and spread equivalently over collagen types I, III, IV, and V and laminin, migration over laminin was significantly slower than migration over the collagen types. Fibronectin was a poor substrate for attachment, spreading, and migration. Epidermal growth factor (EGF) stimulated migration over laminin but did not alter Caco-2 migration over collagen or fibronectin. This effect was independent of cell proliferation, which was stimulated equivalently on both laminin and collagen I. Expression and organization of cell surface receptors for matrix (integrins) were studied using antibodies specific for beta and alpha-integrin subunits. Integrin surface expression was assessed by immunoprecipitation of surface 125iodinated control and EGF-treated cells. Beta-1 surface pools did not change substantially in any condition studied. Alpha-1 subunit pools were decreased after EGF treatment on collagen I but alpha-1 pools increased after EGF treatment on laminin. Surface pools of alpha-2 subunits were increased following EGF treatment whether cells were cultured on laminin or collagen I. However, traditional immunofluorescent and laser confocal imaging demonstrated substantial differences in the character of alpha-2 subunit organization between collagen and laminin in the migrating cell front. Furthermore, a functional antibody to the alpha-2 subunit inhibited EGF stimulation of migration over laminin without substantial effects on basal migration over laminin or collagen I. Thus, EGF appears to exert a matrix-specific effect on enterocyte migration by modulation of integrin expression and organization.