Comparison of the effects of fibronectin and laminin on tumor cells invasiveness. A. LM-2-4 cells (6 × 104cells/well) were seeded between two collagen layers as described in methods. Laminin (0.1 mg/ml) or fibronectin (0.1 mg/ml) were selectively added to the upper or lower collagen layers or to both collagen layers. The experiment was terminated after 3 days and invading cells stained in gels as described. B. LM2-4 cells that invaded the upper or lower collagen gels were counted as described in methods. Shown are the results of two independent experiments. At least twelve microscopic fields were counted to obtain individual average data points. C. The effects of laminin and fibronectin on the ability to invade collagen gels were measured as described under A. D. Quantification of the relative effects of laminin and fibronectin on the invasiveness of LM2-4 cells was performed as described under B. Error bars represent the standard error of the mean. *p < 0.05, *** p < 0.001.