The Prostacyclin Receptor is a NRF2-regulated Immune Checkpoint in CD8 T cells

Immune checkpoint inhibitor (ICI) therapies revitalize anti-cancer responses by intercepting protein-protein interactions between exhausted CD8 T (Tex) cells and cancer cells (e.g. PD-1:PD-L1). However, up to 50% of patients receiving ICIs relapse, warranting further interrogation of the underpinnings of Tex. We conducted RNA-seq meta-analysis of Tex versus effector (Teff) mouse CD8 T cells, and highlighted NRF2 transcriptional targets as the most upregulated gene set in Tex cells. LCMV or cancer inoculation of mice bearing NRF2 hyperactive—or Keap1-/- (NRF2 negative regulator)—T cells demonstrated that NRF2 drives Tex; evidenced by increased co-inhibitory marker (PD-1/TIM-3) expression and reduced cytokine (IFN-g/Granzyme-B) production. RNA-seq of Keap1-/- highlight Ptgir—which encodes the prostacyclin lipid receptor— as the most upregulated gene versus WT T cells. Accordingly, PTGIR knockout in NRF2-hyperactive/ Tex cells decreased PD-1/TIM-3 expression, increased cytokine production, and attenuated tumor growth. Our data underscore PTGIR as a NRF2-regulated Tex driver and illuminate an unconventional immune checkpoint class potentially based on protein-lipid interactions