MAP2K4 and cancer: Some studies have suggested MAP2K4 functions as a pro-oncogenic molecule in breast and pancreatic tumors (Wang et al., 2004), melanoma (Finegan and Tournier, 2010), and in prostate cancer tumors (Lotan et al., 2007; Pavese et al., 2014), whereas other early reports identified MAP2K4 as a putative tumor suppressor gene due to its frequent inactivation in human cancer cell lines and tumor tissues, including pancreatic, breast, ovarian, and colon cancer cells and tissues (Su et al., 1998; 2002; Nakayama et al., 2006; Ahn et al., 2011).