PECAM1 and neoplasm: Thus, IHC and quantification analyses were performed to examine the effect of ANG2 overexpression on CD31, a vascular marker that has an important role in angiogenesis.17 The results revealed increased expression of CD31 in tumor tissue groups of ANG2-overexpressing cells compared with the control groups, whereas reduced CD31 protein expression was observed in the groups with ANG2 inhibition (Figure 4d).