A function for the integrin alpha6beta4 in the invasive properties of colorectal carcinoma cells
Chao, C.; Lotz, M.M.; Clarke, A.C.; Mercurio, A.M.
Cancer Research 56(20): 4811-4819
1996
ISSN/ISBN: 0008-5472 PMID: 8841003 Document Number: 459178
Expression of the integrin alpha-6-beta-4, a receptor for the laminin family of matrix proteins, has been correlated with the progression and metastatic potential of several different tumors, including colorectal carcinoma. For this reason, defining the mechanistic contribution of alpha-6-beta-4 to the aggressive behavior of colorectal and other carcinoma cells is an issue of timely importance for cancer biology. In the present study, we sought to gain insight into the function of alpha-6-beta-4 in colorectal carcinoma cells by studying the behavior of clone A cells, which express high surface levels of this integrin, and by restoring alpha-6-beta-4 expression in RKO cells, a beta-4-deficient rectal carcinoma cell line. The data obtained reveal that alpha-6-beta-4 expression increases the adhesive strength of these cells on laminin-1 matrices, although it does not increase their ability to migrate on such matrices. The RKO/beta-4 transfectants were considerably more spread on Matrigel, laminin-1, and collagen I than the mock transfectants and displayed numerous extensions suggestive of pseudopodia. More importantly, we discovered that expression of alpha-6-beta-4 facilitates the ability of colorectal carcinoma cells to invade both Matrigel and collagen I matrices. The alpha-6-beta-4-dependent increases in adhesion and invasion, as well as the observed morphological changes, required an intact beta-4 cytoplasmic domain. These data argue for a ligand-independent role for alpha-6-beta-4 in promoting cell invasion, and they have important implications for the involvement of this integrin in colorectal carcinoma progression.