Endothelin-1 (ET-1) is a potent mitogen for a variety of cell types, including vascular smooth muscle cells, fibroblasts and endothelial cells, and is able to coordinate the proliferative effects of other peptide growth factors. The endothelin system has been implicated in the pathobiology of numerous human cancers including those of the prostate, lung, breast, colon and cervix, and plays a role in the aetiology of other pathologies such as hepatic fibrosis and atherosclerosis. ET-1 is generated via processing of inactive big-ET-1 by endothelin-converting enzyme-1 (ECE-1; EC 3.4.24.71). ECE-1 is upregulated in a number of cancers, including prostate cancer, leading to increased levels of ET-1 peptide[1].