Unexpectedly, BCRP staining was positive in CD31+ blood vessels in s.c. pHGG xenografts (Figure 5F and S6A), while it was negative in all the PDX models derived from extra-CNS cancers, suggesting that pHGG cells, but not other cancers, favor the expression of BBB markers in the vasculature of the microenvironment (Figure 5F). Here, PECAM1 is linked to central nervous system cancer.