Augmenting Immunotherapy Impact by Lowering Tumor TNF Cytotoxicity Threshold

New opportunities are needed to increase immune checkpoint blockade (ICB) benefit. Whereas the interferon (IFN)γ pathway harbors both ICB resistance factors and therapeutic opportunities, this has not been systematically investigated for IFNγ-independent signaling routes. A genome-wide CRISPR/Cas9 screen to sensitize IFNγ receptor-deficient tumor cells to CD8 T cell elimination uncovered several hits mapping to the tumor necrosis factor (TNF) pathway. Clinically, we show that TNF antitumor activity is only limited in tumors at baseline and in ICB non-responders, correlating with its low abundance. Taking advantage of the genetic screen, we demonstrate that ablation of the top hit, TRAF2, lowers the TNF cytotoxicity threshold in tumors by redirecting TNF signaling to favor RIPK1-dependent apoptosis. TRAF2 loss greatly enhanced the therapeutic potential of pharmacologic inhibition of its interaction partner cIAP, another screen hit, thereby cooperating with ICB. Our results suggest that selective reduction of the TNF cytotoxicity threshold increases the susceptibility of tumors to immunotherapy. [Display omitted] •TNF abundance is low in tumors at baseline and in ICB non-responding patients•CRISPR/Cas9 screen uncovers hits in the TNF pathway that sensitize to T cell attack•TRAF2 inactivation lowers tumor cytotoxicity threshold to T cell-derived TNF•Combined targeting of TRAF2/cIAP1 increases ICB impact New opportunities are needed to increase immune checkpoint blockade (ICB) impact for cancer patients. A genome-wide CRISPR/Cas9 screen uncovered several hits in the TNF pathway sensitizing tumor cells to T cell elimination. TNF antitumor activity was generally limited in tumors at baseline and in ICB non-responders, correlating with its low abundance. Selective inactivation of TNF signaling lowered melanoma and lung cancer thresholds to low TNF levels, thereby increasing tumor susceptibility to T cell attack and augmenting benefit from anti-PD-1 treatment.