Laminin receptor expression and function in small‐cell lung carcinoma

Interactions between tumor cells and laminin or other components of the extracellular matrix are thought to play a role in tumor invasion and metastasis. To analyze these interactions, we examined the expression of 5 types of laminin receptors on 11 cell lines derived from the highly malignant and metastatic tumor small‐cell lung cancer (SCLC). The integrins VLA‐I, VLA‐3, VLA‐6 and the 67 KDa monomeric receptor were expressed at various levels, whereas the VLA‐2 receptor was absent on the cell lines. Only one cell line expressed none of these laminin receptors. All cell lines co‐expressed α6β1 (VLA‐6) and the 67‐kDa molecule, the only receptors specific for laminin. Analysis of the ability of SCLC cells to bind radiolabeled laminin and to adhere to laminin substrata revealed a correlation between these 2 parameters and the expression of VLA‐6 and the 67‐kDa monomeric receptor. Cell adhesion was mediated by α6β1, as indicated by inhibition of adhesion using an anti‐VLA‐6 monoclonal antibody (MAb). Both VLA‐6 and the monomeric receptor were up‐regulated in vitro by laminin.