Most importantly, inhibition of Stat5a/b blocked not only primary growth of PC xenograft tumors, but also recurrent growth of castrate-resistant tumors [177] demonstrated by pharmacological inhibition of Stat5a/b signaling by a potent Jak2 kinase inhibitor, AZD1480, in the CWR22Pc model of CRPC growth. Here, JAK2 is linked to pachyonychia congenita.