In this paper, we demonstrate that a chondroitin sulfate proteoglycan purified from a rat yolk sac tumor alters the adhesion of the tumor cells to substrata containing fibronectin or type I collagen. In the presence of the proteoglycan, these substrata were much less adhesive and did not promote cell spreading. The inhibitory effect of the proteoglycan was reversible and more pronounced during the early stages of cell attachment in vitro. The effect of the proteoglycan was selective in that it depended on the ability of the adhesive substratum to bind the proteoglycan. The proteoglycan did not inhibit the attachment of the cells to type IV collagen, which bound 12 times less proteoglycan than did type I collagen. Similarly, attachment of the cells to fibronectin fragments which did not bind the proteoglycan was not affected by it. The selective effects of the proteoglycan on the adhesion of cells to extracellular matrices suggest that such proteoglycans may promote tumor invasion by reducing interaction of cells with interstitial extracellular matrices while permitting attachment to basement membranes.
This work was supported by Grant CA 28101 and Cancer Center Support Grant CA 30199 from the National Cancer Institute, Department of Health and Human Services.