Natural killer cells regulate distinct CD8+ T cell differentiation program in cancer and contribute to resistance against immune checkpoint blockers

Immune checkpoint blockers (ICBs) targeting the PD-1/PD-L1 axis represent established therapies for many cancers. However, resistance occurs in most patients due to multiple complex immune-suppressive mechanisms in the tumor microenvironment (TME). Natural killer (NK) cells can play effector roles in tumor control, but their impact on T cell dysfunction and ICB efficacy remains controversial. Through genetic and antibody-mediated NK cell depletion, we found that NK cells play negative roles in ICB sensitivity; they further impede CD8+ T cell differentiation toward CD69+ BCL2+ EOMES+ GZMB+ TIM3- GITR- CTLA4- phenotype. Mechanistically, we identified that the retinoic acid receptor alpha (RARa)-dependent differentiation program in CD8+ T cells is hindered due to cytokine competition with NK cells. Finally, we observed that lower frequencies of NK cells correlate with better clinical response to ICBs in cancer patients. These findings suggest a potential avenue for enhancing CD8+ T cell-centered immunotherapy by targeting NK cells. Overall design: We conducted single-cell sequencing using the 10x Genomics platform to investigate the impact of NK cells on the differentiation program of CD8+ T cells. The MC38 tumor model was utilized, and CD8+ T cells were isolated from tumors of both control and NK cell-depleted mice. Our findings demonstrate that NK cells significantly influence the differentiation trajectory of CD8+ T cells.