The RGD peptide is the binding motif of fibronectin to cell adhesion molecules. RGD-4C is a double cyclic peptide that can bind preferentially to integrins at sites of tumor angiogenesis and inflamed synovium in vivo, and can be internalized into targeted cells. Recent applications include RGD-4C coupling to proapoptotic domains to treat tumors and inflammatory arthritis, or to radioactive labels for the broad spectrum imaging of tumor tissue.Sea Squirt: H-Ala-Cys-Asp-Cys-Arg-Gly-Asp-Cys-Phe-Cys-Gly-OH(Cys2-Cys10, Cys4-Cys8) or H-ACDCRGDCFCG-OH (Cys2-Cys10, Cys4-Cys8)