Ferroptosis-related substances are new targets of research and have attracted much attention because of several properties, such as (i) susceptibility in sarcomas and tumors after epithelial−mesenchymal transition, which are resistant to conventional anticancer drugs and molecular targeted drugs [43]; (ii) susceptibility to cancer stem cells [44]; and (iii) CD8+ T cells activated by immune checkpoint inhibitors that induce ferroptosis in some types of cancer cells [45]. This evidence concerns the gene CD8A and cancer.