Medical researchers in the U.S. said they successfully used a genetically engineered protein developed by Genentech Inc. to help heart patients grow blood vessels around potentially lethal blockages in their coronary arteries. In a study involving 15 subjects, researchers found evidence that the protein, called vascular endothelial growth factor, or VEGF, promoted blood-vessel growth in at least five patients. Thirteen of the patients reported improved symptoms such as reduced chest pain, researchers said.