Mitochondrial regulator CRIF1 deficiency induces Foxp3low inflammatory non-suppressive regulatory-T cells in tumors [ATAC-seq]

Foxp3low inflammatory non-suppressive (INS)-regulatory T cells (Tregs) were discovered recently. Unlike conventional Tregs, they produce proinflammatory-cytokines, exhibit reduced suppressiveness, and promote rather than impair anti-tumor immunity. The role of mitochondria in Foxp3low INS-Treg formation in vivo is unclear. We showed that the Foxp3low INS-Treg equivalents in human tumors demonstrate attenuated expression of CRIF1, a vital mitochondrial regulator. Mice with CRIF1 deficiency in Tregs bore Foxp3low INS-Tregs with mitochondrial dysfunction. The ?-ketoglutarate-mTORC1 axis was enhanced in these cells. This promoted proinflammatory-cytokine expression by inducing EOMES and SATB1 expression. Moreover, chromatin openness of the regulatory regions of the Ifng and Il4 genes was increased, which facilitated EOMES/SATB1 binding. The increased ?-ketoglutarate-derived 2-hydroxyglutarate downregulated Foxp3 expression by methylating the Foxp3-gene regulatory regions. Furthermore, CRIF1-deficiency-induced Foxp3low INS-Tregs suppressed tumor growth in an IFN-? dependent manner. Thus, CRIF1-mediated mitochondrial homeostasis is critical for inducing Foxp3low INS-Tregs that promote anti-tumor immunity. Overall design: Tregs were sorted by flow cytometry, and RNA-seq and ATAC-seq was performed.