25 Mar 2014 --- A protein known to promote cancer appears to give the blood vessels strength and shape, researchers report. When yes-associated protein, or YAP, is deleted from vascular smooth muscle cells during development, the protein makes thin-walled blood vessels that over-dilate in response to the usual pressure of blood flow, said Dr. Jiliang Zhou, vascular biologist at the Medical College of Georgia at Georgia Regents University.