PECAM1 and neoplasm: Furthermore, several cell markers using IHC methods further confirmed that combined treatment triggered cell apoptosis (cleaved caspase-3 staining), inhibited angiopoiesis (CD31 staining), activated p53 phosphorylation (Ser15-p53 staining) and inhibited tumor xenografts cell proliferation (Ki67 staining) (Fig. 6B).