EDN1 and breast cancer: In a companion paper Wacnik et al. (December 2001) reported elevated release from the tumor of the peptide endothelin-1 (ET-1), the most potent vasoconstrictor known.12 This finding was consistent with previous studies that had implicated the peptide in the transmission of nociceptive information [67,68,69,70,71,72] as well as studies that found the peptide secreted in high concentrations by metastatic prostate and breast cancer cells [73] and in the plasma of men with prostate cancer [74].