Antioxidant metabolism in activated CD8+ T cells regulates stem-like human memory T cell formation and anti-tumor immunity

Adoptive T cell transfer (ACT) immunotherapy benefits from early-differentiated memory stem-like T (TSCM) cells capable to persist in the long term and to generate potent anti-tumor effectors. Due to their paucity ex vivo, TSCM can be derived from less differentiated naïve precursors but the molecular signals at the basis of their generation are ill-defined. We found that less differentiated human circulating CD8+ T cells display substantial antioxidant capacity ex vivo compared to more differentiated central and effector memory T cells. Limiting reactive oxygen species (ROS) metabolism with anti-oxidants during naïve T cell activation hindered terminal differentiation while allowing expansion and generation of TSCM cells. N-acetylcysteine, the most effective in this regard, induced a transcriptional network and a metabolic profile characteristic of self-renewing memory T cells. Upon ACT, the generated TSCM cells established long-term immunity in vivo and exerted more potent anti-tumor immunity in a xenogeneic model when redirected with CD19 CAR, highlighting the translational relevance of NAC as a simple and inexpensive method to improve ACT mRNA profiles of human CD8 T cells after 8 days of cell culture with or without N-acetyl cysteine (NAC)