EDN1 and ductal breast carcinoma in situ: In another study comparing expression of the ET-axis in a series (n=88) of invasive breast carcinomas, concomitant DCIS, and normal breast tissue, we demonstrated a stepwise increase of ET-1 and ETAR expression with disease progression, suggesting that expression of these proteins correlates with the acquisition of malignant potential and invasive behaviour (Wülfing et al, 2004a).