The TET2 methylcytosine dioxygenase regulates early and late transitions in exhausted CD8+ T-cell differentiation

Epigenetic reprogramming of CAR T-cells by targeting TET2, a methylcytosine deoxygenase that mediates active DNA demethylation, has shown therapeutic potential; however, the role of TET2 in TEX development is unclear. In both CAR T-cell exhaustion models in vitro and chronic LCMV infection in vivo, TET2 drove the conversion from memory-like, self-renewing TEX progenitors towards effector (TEFF)-like and terminally differentiated TEX. TET2-deficient terminally differentiated TEX retained aspects of TEX progenitor biology, including decreased expression of the transcription factor TOX, suggesting that TET2 is required for terminal exhaustion. Mice with chronic LCMV infection received WT or TET2KO P14 T cells. Naive and D15 T cells were isolated; D15 T cells were assessed in bulk, as well as in sorted subsets of Ly108+ and Ly108-. Bulk RNA-Seq and ATAC Seq were performed. Separately, human CAR T cells targeting CD19 were co-cultured with irradiated K562-CD19+ cells at a 1:1 ratio for 5 days, with fresh R10 media and newly irradiated K562 cells for 4-5 additional stimulations. Bulk RNA-Seq was performed.