E1A stimulates FGF-2 release promoting differentiation of primary endothelial cells.

Basic Fibroblast Growth Factor (FGF-2) is a growth and survival factor and represents one of the most potent differentiation agents of vascular system. In the present study we describe that adenoviral oncoprotein E1A regulates FGF-2 production and determines the acquisition of a pro-angiogenic phenotype in primary bovine aortic endothelial cells (BAEC). Following their transfection, wild type E1A proteins 12S and 13S (wtE1A) stimulated BAEC to differentiate on reconstituted basement membrane matrix (Matrigel). This outcome was paralleled by invasion and migration enhancement in wtE1A-transfected cells. This stimulating effect was absent with the E1A mutant dl646N. Accordingly, zymography and RT - PCR analyses showed that matrix metalloproteinase-9 protein- and mRNA-levels increased following wtE1A transfection. Interestingly, wtE1A-transfected BAEC showed FGF-2 mRNA- and protein-levels higher than controls. Further, FGF-2 neutralization reduced the amount of MMP-9 released in the supernatant of E1A-transfected cells and strongly inhibited BAEC differentiation, thus suggesting that wtE1A activates BAEC by a mechanism, at least partially, dependent on a FGF-2 autocrine/paracrine loop.