CDK4 and melanoma: Other genes that were manipulated to develop genetic mouse models of melanoma were: RET—a proto-oncogene that enciphers glial cell-derived neurotrophic factor-specific receptor tyrosine kinase and interferes in the progression stage of melanoma [50]; Mt1-hepatocyte growth factor/scatter factor—Mt1-HGF/SF [94,98]; G-protein-coupled receptor GRM-1 (metabotropic glutamate receptor-1) [79]; guanine nucleotide-binding protein G(q) subunit α (GNAQ) [80]; and cyclin-dependent kinase 4 (CDK4) [2,20,95].