Of interest, N-terminal sequence of PrPc possesses extended poly-(L proline) II (PPII) helix37 and profilin family is known to bind to polyproline binding sites.38 Profilin-1 interactions with actin and polyproline ligands advance actin polymerization and cell motility,39 which becomes important during tumor progression. This evidence concerns the gene PFN1 and neoplasm.