Furthermore, while vessel densities significantly declined from treatment‐naive to bevacizumab‐treated GBM samples (120 CD31+ vessels/mm2 versus 40 CD31+ vessels/mm2, P < 0.005; Fig 6A and C), the vast majority of the remaining tumor vessels in the bevacizumab‐treated group showed strong Ang‐2 immunoreactivity (Fig 6B, D and E). Here, PECAM1 is linked to glioblastoma.