GPX4 and FSP1, key ferroptosis regulators, are critical for T cell functions and CAR-T antitumor activity

Induction of ferroptosis, an iron-dependent form of regulated cell death, holds promise as a strategy to overcome tumor resistance to conventional therapies and enhance immunotherapy responses. However, while the susceptibility of tumor cells to ferroptosis is extensively studied, limited data exists on the vulnerability of immune cells to disturbed iron balance and lipid peroxidation. Here, we found that T cell stimulation rewires iron and redox homeostasis and by increasing levels of reactive oxygen species and labile iron promotes lipid peroxidation and T cells’ ferroptosis. Upon stimulation, we detected substantial changes in the balance of ferroptosis-suppressive proteins, including GPX4 decrease and increase of FSP1, a phenomenon never described before. Subsequently, we identified GPX4 as a master regulator orchestrating T/CAR-T cells’ sensitivity to ferroptosis and demonstrated that GPX4 inhibitors impair T/CAR-T cells’ functions. Surprisingly, we observed that FSP1 regulates T cell antitumor activity independently of its ferroptosis-suppressive function. Specifically, FSP1 inhibition decreased oxidative phosphorylation and mitochondrial ATP production, reduced the amount of perforin and cytokines produced by T cells, and suppressed their proliferation. Altogether, our study for the first time indicates that GPX4 and FSP1, key regulators of ferroptosis, are critical for the antitumor cytotoxic potential of T/CAR-T cells. From our study FSP1 also emerges as a novel metabolic regulator in T cells, which inhibition profoundly affects T cells’ oxidative phosphorylation. Our findings are not only significant to understand metabolic vulnerabilities of T cells but may also hold particular significance from the standpoint of therapeutic development. In the context of our results, future anticancer therapies should be carefully designed to selectively induce ferroptosis of tumor cells without impeding cytotoxic cells’ antitumor efficacy.