The Wnt signaling pathway is a network of proteins best known for their roles in embryogenesis and cancer, but also involved in normal physiological processes in adult animals.The first Wnt gene was discovered by Roeland Nusse and Harold Varmus in 1982 when they observed activation of Int1 (integration 1) in the breast tumors of mice infected with mouse mammary tumor virus (MMTV), in which Int was identified as a vertebrate gene near several integration sites of MMTV.