Tumor endothelial markers (TEMs) display elevated expression during angiogenesis. Their associations with the cell surface membrane are of great interest for both biological and clinical research. G protein coupled receptor 124 (GPR124) is encoded as a seven pass transmembrane protein of 1331 amino acids and is most similar to the cadherin related Celsr1 proteins and members of the calcium independent alpha latrotoxin receptor family involved in transmitting signals across the cell membrane. GPCRs have been excellent drug targets because their natural ligands can often mimicked for agonistic or antagonistic purpose. The existence of tumour specific endothelial markers provides a resource for further understanding the mechanisms of tumour angiogenesis and encourages the development of antiangiogenic therapies in the future. ESTs for the gene that encodes GPR124 have been isolated primarily from amnion, connective tissue, ear, embryo, eye, ganglion, heart, lung, placenta, and skin libraries.