Regulation of the breast cancer stem cell phenotype by hypoxia-inducible factors.

The small subpopulation of breast cancer cells that possess the capability for self-renewal and formation of secondary tumours that recapitulate the heterogeneity of the primary tumour are referred to as tumour-initiating cells or BCSCs (breast cancer stem cells). The hypoxic tumour microenvironment and chemotherapy actively induce the BCSC phenotype. HIFs (hypoxia-inducible factors) are required and molecular mechanisms by which they promote the BCSC phenotype have recently been delineated. HIF inhibitors block chemotherapy-induced enrichment of BCSCs, suggesting that their use may improve the response to chemotherapy and increase the survival of breast cancer patients.