Role of laminin in the attachment and metastasis of murine tumor cells.

We have studied the attachment of two murine metastatic cell lines and of a transformed, nonmetastatic sarcoma cell line to type IV (basement membrane) collagen. The metastatic cells attached preferentially to type IV collagen, whereas the nonmetastic cells attached best to type I collagen. Laminin increased both the rate and the number of metastatic cells attaching to type IV collagen, while fibronectin had no effect. Antibodies to laminin prevented the attachment of metastatic cells to type IV collagen, while antibodies to fibronectin prevented the attachment of the nonmetastatic cells. The number of pulmonary metastases which formed after i.v. injection of cells into C57BL mice was used to measure the metastatic propensity of these cell lines. A subpopulation of the metastatic cells selected for by their ability to attach to type IV collagen in the presence of laminin produced more metastases than did unattached cells or cells attached with fibronectin. In addition, incubation of metastatic cells with antibody to laminin prior to injection into mice markedly reduced the number of lung metastases. These data suggest that laminin promotes the attachment of metastatic tumor cells to basement membrane during the metastaatic process.