Hypoxia-inducible factors: Mediators of cancer progression and targets for cancer therapy

Hypoxia-inducible factors (HIFs) mediate adaptive physiological responses to hypoxia. In human cancers that are accessible for O ₂ electrode measurements, intratumoral hypoxia is common and severe hypoxia is associated with increased risk of mortality. HIF activity in regions of intratumoral hypoxia mediates angiogenesis, epithelial-mesenchymal transition, stem-cell maintenance, invasion, metastasis, and resistance to radiation therapy and chemotherapy. A growing number of drugs have been identified that inhibit HIF activity by a variety of molecular mechanisms. Because many of these drugs are already FDA-approved for other indications, clinical trials can (and should) be initiated to test the hypothesis that incorporation of HIF inhibitors into current standard-of-care therapy will increase the survival of cancer patients.