Laminin has been shown to promote the malignant phenotype and the expression of certain laminin receptors has been correlated with the malignant character of the tumors. Here new cell lines were isolated from a human colon cancer cell line (LCC-C1) based on their adhesiveness to laminin. The laminin-adherent subclone formed large tumors in nude mice, whereas the laminin-nonadherent subclone failed to form sizable tumors. Only the laminin-adherent subclone adhered to laminin and invaded through Matrigel-coated filters. The adhesive and invasive ability of the cells was almost completely blocked by low concentrations (1.0 microgram/ml) of anti-beta 1 integrin antibody. The amounts of total cellular beta 1 integrin protein were similar in the two subclones when compared by Western blot, and the mRNA levels also did not differ. The localization of beta 1 integrin laminin receptor varied in the two subclones; the laminin-adherent subclone showed a linear distribution along the cell-cell junctions, while the laminin-nonadherent subclone did not stain between the cells. Using laminin-Sepharose affinity chromatography, more beta 1 integrin was obtained from the laminin-adherent subclone. These findings suggest that alterations in the affinity of beta 1 integrin for laminin and in its membrane distribution might be involved in the increased tumorigenicity observed in colon cancer cells.