Pseudohypoxia

Pseudohypoxia is a state of constitutive activation of the hypoxia-inducible factor (HIF) signaling pathway that occurs independent of actual low tissue oxygen tension. The clearest example is clear cell renal cell carcinoma (ccRCC), where loss of the von Hippel-Lindau (VHL) tumor suppressor prevents the normal oxygen-dependent degradation of HIF-1α and HIF-2α, so these transcription factors remain active — driving angiogenesis and a hyper-vascular tumor phenotype — even when the tissue is not actually oxygen-deprived. Because pseudohypoxia mimics the downstream signaling of true hypoxia, distinguishing the two requires direct measurement of oxygen tension rather than relying on HIF pathway activity alone.