Mitogen-activated protein kinase (MAPK) kinase 4/c-Jun NH2-terminal kinase (JNK)-activating kinase (MKK4/JNKK1/SEK1), referred to as MKK4, was initially characterized as a metastasis suppressor in prostate and ovarian cancers [21,22]. The gene discussed is MAP2K4; the disease is ovarian carcinoma.