Pericytes in sarcomas of bone.

Pericytes are mesenchymal cells that closely enwrap small blood vessels, lying in intimate association with the endothelium. Pericytes have recently gained attention as an important mediator of vascular biology and angiogenesis in cancer. Although better studied in carcinoma, pericytes have known interaction with sarcomas of bone, including Ewing's sarcoma, osteosarcoma, and chondrosarcoma. Best studied is Ewing's sarcoma (ES), which displays a prominent perivascular growth pattern. Signaling pathways of known importance in intratumoral pericytes in ES include Notch, PDGF/PDGFR-β, and VEGF signaling. In summary, pericytes serve important functions in the tumor microenvironment. Improved understanding of pericyte biology may hold significant implications for the development of new therapies in sarcoma.