The alpha 3 beta 1 integrin is associated with mammary carcinoma cell metastasis, invasion, and gelatinase B (MMP-9) activity

The alpha 3 beta 1 integrin is elevated in several types of metastatic tumo r and has been associated with increased migration and invasion. Our analys is of a series of mammary carcinomas of different histotypes and their corr esponding metastases demonstrated significantly increased expression of alp ha 3 beta 1 I in the tumor metastases. We therefore studied alpha 3 beta 1 expression of several human breast carcinoma cell lines and its association with the invasive phenotype. The MDA-MB-231 cell line expressed high level s of the beta 1, alpha 2, alpha 3, alpha 5, and alpha 6 integrin subunits a long with moderate levels of the alpha v beta 3 integrin, This line was hig hly migratory and the most invasive using a chemo-invasion assay. In contra st, the other lines tested, MDA-MB-145, MCF-7, and SK-BR-3, showed lower mi gratory and invasive activity and reduced alpha 3 integrin subunit expressi on. Metalloproteases capable of degrading collagen IV are necessary for the invasive process. RT-PCR showed that MDA-MB-231 cells expressed MMP-9, but not MMP-2, gelatinase/collagenase IV. Gelatin zymography demonstrated that invading MDA-MB-231 cells released high levels of MMP-9 gelatinase activit y. A direct role for this gelatinase in MDA-MB-231 cell invasion was confir med by inhibition of invasion using the metalloprotease inhibitor Batimasta t. Treatment of MDA-MB-231 cells with a function-blocking anti-alpha 3 anti body strongly inhibited migration and invasion. This correlated with a mark ed reduction in MMP-9 activity produced by MDA-MB-231 cells, suggesting a r ole for alpha 3 beta 1 ligand binding in cell signaling and regulation of e xtracellular matrix degradation. Int. J. Cancer 87:336-342, 2000. (C) 2000 Wiley-Liss, Inc.