Human breast adenocarcinoma cell lines promote angiogenesis by providing cells with uPA-PAI-1 and by enhancing their expression.

During angiogenesis, endothelial cells use uPA and PAI-1 to migrate and degrade the basement membrane surrounding capillary blood vessels. Invasive tumor cells produce a large amount of uPA that could bind uPAR present at the endothelial cell surface to facilitate their invasion. To verify this hypothesis, endothelial cells were incubated with conditioned medium (CM) from two breast cancer cell lines (MCF7 and MDA MB 231 cells).