Abstract Background: Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) are the main therapy for advanced EGFR-mutant lung adenocarcinoma LUAD, but treatment response varies widely and options are limited once resistance develops. Mechanisms of primary EGFR-TKI resistance remain inadequately understood. We found that multiple bacteria of the Bacteroidetes phylum, including the periodontal pathogens Porphyromonas gingivalis (Pg), lead to EGFR-TKI resistance in vitro. Pg infection is implicated in the pathogenesis and progression of several malignancies, including lung cancer, likely through secreted virulence factors and immune modulation. This led us to investigate the effect of Pg on EGFR-TKI sensitivity in EGFR mutant lung cancer. Methods: EGFR-mut LUAD cells were treated with Pg preconditioned medium (PCM) under EGFR-TKI or control conditions, followed by evaluation of drug response, IGF1R signaling activation, and the contribution of Pg gingipains through mutant analyses and treatment with purified gingipains. The presence of Pg in human lung cancer was investigated using Fluorescence In Situ Hybridization (FISH) probes specific to Pg. Human EGFR-mut lung tumor tissue slices were used to assess the Pg effect on osimertinib resistance. Direct interaction between gingipains and IGF1R were analyzed by dot-blot and co-immunofluorescence assays. The equilibrium binding constants (Kd) for IGF1R binding to Kgp and RgpA were determined to quantify the strength of their non-covalent, reversible protein-protein interactions. Results: Infection with Pg significantly decreased the sensitivity of multiple EGFR-mut LUAD to EGFR-TKIs including osimertinib and lazertinib in both human and mouse EGFR-mutant lung cancer cells through activation of the IGF1R pathway. Pg infection with osimertinib showed higher pIGF1R levels and lower cleaved caspase-3 levels in human lung tumor slice versus osimertinib alone. Mutant gingipain-deficient Pg abolished the activation of IGF1R signaling and restored TKI sensitivity. Clinical isolates of Pg derived from individuals with periodontal disease were also led to dramatic decreases in EGFR-TKI sensitivity. Purified gingipains RgpA and Kgp both activate IGF1R pathway by directly binding to IGF1R protein. The Kd value showed strong binding interaction between IGF1R and RgpA, and moderate binding interaction between IGF1R and Kgp. Conclusion: Pg, commonly identified within LUAD tissues, induces EGFR-TKI resistance in EGFR-mut LUAD via Pg gingipain-dependent activation of IGF1R. Gingipains directly interact with IGF1R, revealing a new bacterium-tumor crosstalk mechanism that promotes drug resistance and suggesting potential therapeutic benefits of targeting bacterial enzymes or the IGF1R pathway. Additional studies on the effect of Pg on EGFR-TKI response in humans are needed. Citation Format: Wendong Li, Mahima Raul, Keqiang Zhang, Jan Potempa, Yuanyuan Gao, Dan Raz. Intra-tumoral Porphyromonas gingivalis mediates osimertinib resistance in EGFR-mutant lung adenocarcinoma through gingipain-mediated IGF1R activation abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 7031.
Li et al. (Fri,) studied this question.