PECAM1 and neoplasm: In brain sections of GBM-bearing mice, IGFBP7 immunoreactivity detected by anti-IGFBP7 sdAb (clone 4.43) was enhanced and detected specifically in the tumours (Figure 2A), but not in normal brain (Figure 2B), and colocalised with the immunoreactivity against the vascular antigen, CD31 (Figure 2A).