Cancer-associated Fibroblasts Confer Osimertinib Resistance in Non-small Cell Lung Cancer Cells via NRG1-mediated HER3/AKT Signaling

Osimertinib is a third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI); it has achieved favorable progression-free survival (PFS) in non-small cell lung cancer (NSCLC) patients with EGFR mutation, however, the resistance occurs in most patients, and the underlying mechanism remain to be elucidated. Cancer-associated fibroblasts (CAFs) are major stromal cells in tumor microenvironment. Despite accumulating evidence suggests that CAFs contribute to drug resistance, the role of CAFs in osimertinib resistance in NSCLC is not fully understood. Here, we reported that CAFs promoted the resistance of NSCLC cells to osimertinib through enhancing stemness of NSCLC cells and reducing apoptosis induced by osimertinib. CAFs possessed a high level of Neuregulin-1 (NRG1), and CAFs-secreted NRG1 mediated the promoting effect of CAFs on osimertinib resistance, demonstrated by applying recombinant human NRG1 (rhNRG1) and NRG1 knockdown. We also found that osimertinib stimulated NRG1 secretion by CAFs, which may further enhance osimertinib resistance. Further study revealed that CAFs promoted the resistance of NSCLC cells to osimertinib via NRG1-mediated HER3/AKT/NF-κB pathway. Moreover, the mouse xenograft study demonstrated that CAFs enhanced osimertinib-treated tumor growth <i>in vivo</i>. Our finding highlights the potential value of CAFs-derived NRG1 as a novel therapeutic target for osimertinib resistance in lung cancer.