Abstract

EGFR hotspot mutations (mEGFR), including primary L858R, exon 19 deletion, and secondary T790M, are pivotal oncogenic drivers in human non-small cell lung cancer (NSCLC). At the same time, NSCLC resistance to third-generation tyrosine kinase inhibitors (TKIs) is a major clinical challenge and remains mechanistically unresolved. Here, we uncover a previously unrecognized tumor cell-intrinsic mechanism in which mutant EGFR (mEGFR) exploits innate immune signaling via the cGAS–STING–TBK1 pathway to sustain oncogenic signaling and therapeutic resistance. Mechanistically, mutant EGFR kinase aberrantly associates with STING signalosomes and phosphorylates STING (Y245/Y314) and TBK1 (Y577/Y677), stabilizing and hyperactivating TBK1 and establishing an unexpected kinase loop critical for DNA damage repair. Genetic or pharmacological disruption of mEGFR–STING–TBK1 coupling sensitizes resistant patient-derived NSCLC organoids to chemotherapy. Combining TBK1 inhibition with cisplatin suppressed mEGFR-driven tumors in murine models of spontaneous and immunocompetent NSCLC and in patient-derived organoids. Our findings suggest a new function of cGAS–STING in DNA damage tolerance, its paradoxical exploitation by oncogenic driver mutations, and an innate immune therapeutic vulnerability in NSCLC.