Cancer immunotherapies benefit only a subset of patients, highlighting the need to define tumor-intrinsic mechanisms of immune evasion. Using a kinome-wide CRISPR-Cas9 screen, we identify MAP3K7 (transforming growth factor beta-activated kinase 1 [TAK1]) as a checkpoint that protects cancer cells from CD8T cell-mediated killing. TAK1 integrates tumor necrosis factor (TNF) and interferon gamma (IFNγ) signals to drive a cytoprotective response that blocks cytokine-induced death and prevents bystander killing by perforin-deficient T cells. Inhibition of TAK1 redirects TNF/IFNγ signaling toward apoptosis via RIPK1 and caspase-8 while simultaneously amplifying IFNγ outputs to further prime cells for cytokine-driven death. Mechanistically, TAK1 loss triggers proteasomal degradation of cFLIP, promoting complex II formation and undermining protective pathways. In immune-competent mice, TAK1 deficiency markedly impairs tumor growth, whereas immune-deficient hosts show little effect. Adoptive T cell therapy preferentially eliminates TAK1-deficient clones. These findings establish TAK1 as a tumor-intrinsic immune checkpoint and support TAK1 inhibition as a strategy to enhance cancer immunotherapy. +
