The first human tumor derived protein with in vivo angiogenic activity to be 
obtained in pure form has been isolated from serum-free supernatants of an 
established human adenocarcinoma cell line (HT-29) and named angiogenin. It was 
purified by cation-exchange and reversed-phase high-performance liquid 
chromatography; the yield was approximately 0.5 microgram/L of medium. 
Biological activity of angiogenin was monitored throughout purification by using 
the chick embryo chorioallantoic membrane assay. Statistical evaluation 
demonstrates that it displays activity in this system with as little as 35 fmol 
per egg. Moreover, only 3.5 pmol is required to induce extensive blood vessel 
growth in the rabbit cornea. The amino acid composition of this basic 
(isoelectric point greater than 9.5), single-chain protein of molecular weight 
approximately 14 400 has been determined. The amino terminus is blocked, and the 
carboxyl-terminal residue is proline.