Although EGFR-mutant non-small cell lung cancer (NSCLC) initially responds well to osimertinib, a third-generation EGFR tyrosine kinase inhibitor (TKI), acquired resistance to this agent eventually emerges. While several genetic alterations responsible for resistance have been characterized, the molecular factors that drive the onset of such resistance have largely remained elusive.To uncover mediators of osimertinib resistance induction, we examined clinical samples from patients with EGFR-mutant NSCLC and employed cell lines such as PC-9 and H1975. Techniques included transcriptomic profiling and immunohistochemistry of pretreatment tumor samples, spatial transcriptomics, cell viability assays, immunofluorescence and quantitative PCR, RNA sequencing, immunoblotting, mass spectrometry-based comprehensive proteomics, co-immunoprecipitation and proximity ligation assays, as well as a mouse xenograft model.
Transcriptomic evaluation of pretreatment clinical samples revealed that IFITM3 (interferon-induced transmembrane protein 3) was distinctly overexpressed in patients exhibiting a suboptimal response to osimertinib. Immunohistochemical staining verified that individuals whose tumors expressed IFITM3 had significantly shorter progression-free survival during osimertinib therapy. Additional spatial transcriptomics and related experiments demonstrated that IFITM3 levels in cancer cells rose in reaction to cytokines secreted from the tumor microenvironment (TME) under osimertinib exposure. IFITM3 was shown to facilitate osimertinib resistance in NSCLC cell lines by interacting with MET and thereby activating the AKT pathway. Moreover, co-administration of a MET inhibitor prevented the emergence of osimertinib resistance in a mouse xenograft tumor model. The present study identifies cytokine-driven upregulation of IFITM3 in the TME as a novel, previously undescribed mechanism underlying osimertinib resistance. These results indicate that therapeutic targeting of the IFITM3-MET interaction could enhance outcomes of EGFR-TKI therapy in EGFR-mutant NSCLC.
