EDN1 and breast carcinoma: Studies have investigated expression of ET-1 in human breast carcinoma by applying radioimmunoassay (Yamashita et al, 1991; Yamashita et al, 1995), immunohistochemistry (Kojima and Nihei, 1995; Alanen et al, 2000), and quantitative RT–PCR (Alanen et al, 2000).