CD274 and neoplasm: Meanwhile, Wang et al. further proved that the combination of cyst(e)inase (an engineered enzyme which depletes extracellular cystine and cysteine) with PD-L1 blockade synergistically inhibit cystine uptake through system Xc− in tumor cells, resulting in intracellular GSH deficiency and thus inducing potent tumor cell ferroptosis (Wang et al., 2019).