Tyrosine-protein kinase Fes/Fps also known as proto-oncogene c-Fes/Fps is an enzyme that in humans is encoded by the FES gene. FES was originally cloned as a retroviral oncogene from feline (v-FES) and avian (v-FPS) sarcomas. This triggered the subsequent identification and cloning of the cellular FES (c-FES) genes (also referred to as FPS) in birds and mammals.