PRCP is a serine protease that localizes mainly in the lysosome but can also be extracellular.23 PRCP is known to regulate blood pressure and appetite control through its cleavage of peptide substrates angiotensin II and α-MSH.24–26 A role for PRCP in breast cancer or other cancers has, to date, not been widely recognized. This evidence concerns the gene STAMBP and cancer.