Illustration of the US physician and medical geneticist Gregg L. Semenza (born 1956). Semenza is best known for his work on the mechanisms underlying cellular responses to changes in oxygen availability. He discovered the genes that produced hypoxia-inducible factor (HIF) proteins, a family of proteins responsible for sensing and responding to a lack of oxygen (hypoxia) in the cellular environment. He went on the investigate the role of HIF in cancer, where it allows tumours to proliferate under hypoxic conditions. The discovery of HIF has lead to treatments for diseases including anaemia and could lead to novel cancer therapies. He was awarded a share of the 2019 Nobel Prize in Physiology or Medicine along with Peter Ratcliffe and William Kaelin Jr for his work.