Abstract

The third‐generation EGFR tyrosine kinase inhibitor (TKI) osimertinib (AZD9291) has significantly improved the survival in EGFR‐mutant lung cancer patients. Our team developed limertinib (ASK120067), a novel third‐generation EGFR inhibitor with remarkable antitumor effects, which has been launched in China. Despite initial therapeutic responses, EGFR TKIs‐treated patients ultimately experience fatal metastatic recurrence and disease progression. However, the underlying mechanism of driving metastasis remains poorly understood. Here, we aim to investigate the pro‐metastatic mechanism following treatment with third‐generation EGFR TKIs. Transcriptomics analyses of EGFR TKI‐resistant tumor models revealed an aberrant upregulation of S1PR3, which conferred enhanced metastatic potential to lung cancer. S1PR3 inhibition dramatically reduced metastasis in resistant cells, while its overexpression potentiated metastatic abilities in parental cells. Notably, S1PR3 was highly enriched in clinical samples with AZD9291 resistance and correlates with poor prognosis. Mechanistically, we found that S1PR3 upregulated RAC1‐GTP expression to activate PAK1, thereby promoting epithelial‐mesenchymal transition (EMT) and enhancing metastatic capacity of resistant cells. Further studies identified that the overexpression of fibroblast growth factor receptor 1 (FGFR1) increased S1PR3 expression through signal transducer and activator of transcription 4 (STAT4) to promote the emergence of metastatic‐resistant cells. Importantly, targeting S1PR3 or FGFR1 blocks metastasis in EGFR TKI‐resistant models. • S1PR3 drives metastasis in EGFR TKI‐resistant lung cancer by activating RAC1‐PAK1 signaling and promoting EMT. • FGFR1‐STAT4 axis upregulates S1PR3, enabling metastatic escape in resistant tumors. • Targeting S1PR3 or FGFR1 suppresses metastasis, offering a therapeutic strategy for EGFR TKI‐res