NFE2L2 and cancer: While the cysteine decomposition is coupled with mitochondrial bioenergetics in the cells with intact KEAP1-NRF2 system, in NRF2-addicted cancer cells, most of the available cysteine appears to flow into the anabolic pathway, namely, glutathione synthesis and leaves the catabolic pathway in mitochondria, which is consistent with the observation that mitochondrial respiration is limited in NRF2-addicted cancer cells (Sayin et al. 2017).