AXL and error-prone DNA replication confer drug resistance and offer strategies to treat EGFR-mutant lung cancer.

Anti-cancer therapies have been limited by emergence of mutations and other adaptations. In bacteria, antibiotics activate the SOS response, which mobilizes error‐prone factors that allow for continuous replication at the cost of mutagenesis. We investigated whether treatment of lung cancer with EGFR inhibitors (EGFRi) similarly engages hypermutators. In cycling drug-tolerant persister (DTP) cells and in EGFRi-treated patients presenting residual disease we observed upregulation of GAS6, while ablation of GAS6’s receptor, AXL, eradicated resistance. Reciprocally, AXL overexpression enhanced DTP survival and accelerated the emergence of T790M, an EGFR mutation typical to resistant cells. Mechanistically, AXL induces low-fidelity DNA polymerases and activates their organizer, RAD18, by promoting neddylation. Metabolomics uncovered another hypermutator, AXL-driven activation of MYC and increased purine synthesis that is unbalanced by pyrimidines. Aligning anti-AXL combination treatments with the transition from DTPs to resistant cells cured patient-derived xenografts. Hence, similar to bacteria, tumors tolerate therapy by engaging pharmacologically targetable endogenous mutators. AXL knock out PC9 cells were generatred. Single cells were sorted to a plate. From two cells, B11 and D11 cell culure were grown. Biological groups: control (3 replicates) and KO: B11 and D8 (2 replicates for each).