PECAM1 and neoplasm: As expected, we noted a significant decrease in CD31+ vessels in tumours developed in xenograft mice treated with regorafenib compared to the untreated xenograft mice (101.4 ± 4.55 vs. 141.3 ± 14 CD31+ vessels/mm2, p < 0.05) (Figure 2B and Supplementary Figure S1).