DGKα/ζ inhibition lowers the TCR affinity threshold and potentiates anti-tumor immunity

Checkpoint blockade immunotherapies expand neoantigen- or virus-specific T cells, and poor responsiveness to immunotherapy is associated with lower mutational burden in tumors of non-viral origin. Although mouse models demonstrate that lower affinity T cells recognizing self-antigens can contribute to tumor control if sufficiently activated, therapeutic options for enhancing T cell priming are limited. Diacylglycerol kinases (DGKs) attenuate DAG signaling by converting DAG to phosphatidic acid, thereby suppressing pathways downstream of TCR signaling. Using a novel dual DGK alpha and zeta inhibitor (DGKi), tumor-specific CD8 T cells with different affinities (TRP1high and TRP1low), and a series of altered peptide ligands, we demonstrate that inhibition of DGKα/ζ can lower the signaling threshold for T cell priming. TRP1high and TRP1low CD8 T cells produced more IL-2, IFNγ, and other effector cytokines in the presence of cognate antigen and DGKi. Effector TRP1high- and TRP1low-mediated cytolysis of tumor cells with low antigen load was MHC-restricted, mediated by IFNγ, and augmented by DGKi. Adoptive T cell transfer into mice bearing pancreatic or melanoma tumors synergized with single-agent DGKi or DGKi and αPD1, with increased expansion of low-affinity T cells and increased cytokine production observed in tumor infiltrates of treated mice. Collectively, our findings highlight DGKα/ζ as therapeutic targets for augmenting tumor-specific CD8 T cell function.

Methods
Methods used are described in detail in the manuscript.