Angiogenin (ANG), a angiogenic ribonuclease, is a member of the vertebrate-specific, secreted RNASE superfamily. Angiogenin, originally identified as a tumor angiogenic factor, was related with the growth and metastasis of numerous tumors. Angiogenin is also a component of normal human plasma and follicular Xuid. Its widespread expression in human tissues suggests angiogenin may have biological functions in addition to the promotion of angiogenesis. Recently, its biological activity has been extended to stimulating cell proliferation and promoting cell survival. It is a 17 kDa precursor which is cleaved to generate the 14 kDa mature protein.