Effects of empty vector on hHO-1 expression and hVEGF secretion. (a) hHO-1 expression, (b) VEGF secretion, and (c) luciferase expression after co-transfection with pLuci. The Dual plasmid and the VEGF plasmid were mixed with the same amount of the luciferase plasmid. The mixtures were transfected to H9C2 cells, and hHO-1 expression, hVEGF secretion, and luciferase activity were determined. Data represent mean ± SD (*p<0.05 and **p<0.01).