The first evidence for RKIP as a metastatic suppressor of PC started with the identification of RKIP downregulation in LNCaP cells-derived metastatic C4-2B cells compared to their parental cells [96]; functionally, downregulation of RKIP elevated metastatic potential of C4-2B cells [88]. The gene discussed is PEBP1; the disease is pachyonychia congenita.