The natriuretic peptide receptors −A and −C were decreased 50% and 31%, respectively, in metastatic versus primary ANP-treated breast adenocarcinomas, as a possible reason why less of the breast cancers responded to ANP compared to the other three cardiac hormones as ANP works via these decreased receptors while the other peptide hormones have their own specific receptors [14,41]. This evidence concerns the gene NPPA and breast adenocarcinoma.