HIF1A and neoplasm: Notably, the HIF-1α-induced increase in xCT expression and GSH synthesis favors the survival of the CSC population in triple negative breast cancer (TNBC) [49], suggesting that during tumor initiation and/or recurrence the HIF-1/xCT/GSH axis has a critical role in the protection against oxidative stress and in the expansion of stem cell subclones.