Hypoxia-inducible factors (HIFs) are transcription factors that respond to decreases in available oxygen in the cellular environment, or hypoxia. They also respond to instances of pseudohypoxia, such as thiamine deficiency. Both hypoxia and pseudohypoxia leads to impairment of adenosine triphosphate (ATP) production by the mitochondria.

Gregg Leonard Semenza is a pediatrician and Professor of Genetic Medicine at the Johns Hopkins School of Medicine. He serves as the director of the vascular program at the Institute for Cell Engineering. He is a 2016 recipient of the Albert Lasker Award for Basic Medical Research. He is known for his discovery of HIF-1, which allows cancer cells to adapt to oxygen-poor environments. He shared the 2019 Nobel Prize in Physiology or Medicine for "discoveries of how cells sense and adapt to oxygen availability" with William Kaelin Jr. and Peter J. Ratcliffe. Semenza has had ten research papers retracted due to falsified data.