Mutant p53 suppresses innate immune signaling to promote tumorigenesis

Abstract

Mutations in the p53 tumor suppressor occur very frequently in human cancer. Often, such mutations lead to the constitutive overproduction of mutant p53 (mtp53) proteins, which can exert a cancer-promoting gain-of-function (GOF). We have identified a novel mechanism by which mtp53 controls both cell-autonomous and non-cell autonomous signaling to promote cancer cell survival and suppress tumor immune surveillance. Mtp53 interferes with the function of the cytoplasmic DNA sensing machinery, cGAS-STING-TBK1-IRF3, that controls the activation of the innate immune response. We find that mtp53, but not wildtype p53, binds to TANK binding protein kinase (TBK1) and inhibits both its basal and agonist-induced activity. The association of mtp53 with TBK1 prevents the formation of a trimeric complex between TBK1-STING-IRF3, which is required for activation, nuclear translocation and transcriptional activity of IRF3. Mtp53 knockdown restores TBK1 activity, resulting in the transcriptional induction of IRF3 target genes and IRF3-dependent apoptosis. Furthermore, inactivation of innate immune signaling by mtp53 alters cytokine production resulting in immune evasion. Restored TBK1 signaling was sufficient to bypass mtp53 and reactivate cell-autonomous and non-cell autonomous tumor control. Thus, overriding mtp53s inhibition of this cytosolic DNA sensing pathway may ultimately lead to restored immune cell function and cancer cell eradication.