NOTCH4 and neoplasm: Cluster 2 ECs (tumor core EC type I: Co1) resembled endothelial angiogenic phenotypes as they have been mapped in both developmental and tumor angiogenesis, and included for example a gene signature associated with vascular basement membrane remodeling (COL4A1, COL4A2, LAMB1, LAMA4, HSPG2, PXDN, PLOD1, NID1, NID2), cytoskeletal rearrangements (CD93, MYO1B, SPARC, INSR), angiogenic sprouting (KDR, PGF, ANGPT2, NOX4, PTP4A3, FLT4), and endothelial tip cell formation (APLN, SOX4, ITGA5, PGF, NOTCH4) (Figure 3B, Supplemental Table 4, and Supplemental Figure 5).