HIF1α and HIF2α: sibling rivalry in hypoxic tumour growth and progression.

The α-subunits that form the oxygen-sensitive component of the hypoxia-inducible factor (HIF) transcription factor have unique and overlapping roles in mediating cellular responses to hypoxia. Surprisingly, they can also have opposing roles, and the differences between HIF1α and HIF2α are discussed in this Review.