– WIF1, also known as WIF-1 and wnt inhibitory factor 1, is a secreted protein that binds WNT proteins and inhibits their activities. It contains a WNT inhibitory factor (WIF) domain and 5 epidermal growth factor (EGF)-like domains. WNT proteins are extracellular signaling molecules involved in the control of embryonic development. WIF1 may be involved in mesoderm segmentation and can be detected in fish, amphibia and mammals. WIF-1 is a recurrent target in human salivary gland oncogenesis. Downregulation of WIF1 takes part in the development and progression of pleomorphic adenomas. WIF1 also is a tumor suppressor, and has been found to be epigenetically silenced in various cancers, specifically in nonfunctioning pituitary tumors. WIF1 are expected to have molecular function (protein tyrosine kinase activity) and to localize in various compartments (extracellular space, extracellular region).