Respective roles of laminin and fibronectin in adhesion of human carcinoma and sarcoma cells.

In a previous study, Ewing's sarcoma cells and colon carcinoma cells failed to attach to plastic and to dishes coated with various collagen types I, III and IV, but adhered rapidly to extracellular matrix (ECM) produced by cultured corneal endothelial cells. However, although carcinoma cells required ECM and did not adhere to fibronectin, the sarcoma cells adhered and flattened almost equally well on either substrate. Thus, different adhesive proteins may mediate the attachment of sarcoma- and carcinoma-derived cells to extracellular matrices, the most likely being fibronectin and laminin. Fibronectin stimulates the adhesion of fibroblasts, but not epidermal cells, to collagen type IV (ref. 7) and could mediate the attachment of sarcoma cells. Laminin is confined to the lamina lucida region of basement membranes and has been localized to cellular adhesion sites. Studies of the attachment of epidermal cells in vitro (V.P. Terranova, personal communication) suggest that it is adhesive for epithelial cells, and so could have the same role for carcinoma cells as that played by fibronectin for sarcoma cells. Cultured vascular endothelial cells secrete fibronectin and laminin into both the ECM and the culture medium, and we report here that pre-exposure of plastic dishes to such conditioned medium induces the attachment and flattening of both human colon carcinoma and Ewing's sarcoma cells. While laminin mediates the attachment and spreading of the former fibronectin is responsible for the attachment and flattening of the latter.