Expression of its sister peptides Pyy and Ppy was unchanged or undetectable in KPR172HC cancer cells relative to KPfloxC cancer cells (Fig. 4, Bii and Biii), further confirming that Npy, and not its sister peptides, may have a role in the metastatic spread in the KPR172HC mouse model of PC. Here, PPY is linked to pachyonychia congenita.