The first evidence of Stat5a/b promotion of metastatic behavior of PC cells in vitro and in vivo [169] was provided using an experimental lung metastasis model; inoculation of nude mice with PC cells expressing an active Stat5 construct (Stat5aS710F) increased in vivo formation of lung metastases by 11-fold compared to β-galactosidase (LacZ)-expressing control cells [169]. Here, STAT5A is linked to pachyonychia congenita.