It should be noted that in some cancer cells the transsulfuration pathway can supply a portion of intracellular cysteine for GSH synthesis through de novo synthesis of cysteine (Zhu et al., 2019), and enzymes that are involved in or regulated by the transsulfuration pathway (Fig. 1), such as cystathionine β-synthase (CBS) and cysteinyl-tRNA synthetase (CARS), can modulate the susceptibility of cancer cells to ferroptosis (Hayano et al., 2016; Wang et al., 2018). The gene discussed is CBS; the disease is cancer.