PECAM1 and head and neck squamous cell carcinoma: Tumor-derived exosomes (TEX) from head and neck squamous cell carcinoma (HNSCC) lines such as PCI-13 and SCCVII induced angiogenic remodeling in HUVECs after rapid internalization, with increased tube formation, proliferation, and migration, along with increased expression of CD31+ endothelial structures and α-SMA+ pericyte coverage.