A Paired Tumor Organoid-Stroma Biobank Reveals PLAU⁺ Fibroblasts as Drivers of Chemoresistance in Lung Adenocarcinoma

Abstract Chemotherapy is a standard treatment for lung adenocarcinoma (LUAD), yet the efficacy is often limited, highlighting the need to elucidate and the underlying mechanisms of chemoresistance. Given the important role of the tumor microenvironment in LUAD progression, we established a biobank of patient-derived LUAD organoids (LCOs) paired with cancer-associated fibroblasts (CAFs) from treatment naïve tumors and found that co-culture with CAFs reduced drug sensitivity of LCOs. Plasminogen activator urokinase (PLAU) was identified as a specific marker of chemoresistance-associated CAFs linked with poor survival in LUAD patients. Tumor cells induced polarization of fibroblasts toward a PLAU+ chemoresistant state that secreted CXCL5 to upregulate the ER chaperone calmegin (CLGN) in tumor cells. CLGN ablation restored drug sensitivity, whereas CLGN expression was elevated in chemotherapy-resistant LUAD and correlated with pathological progression. Together, these findings identify the PLAU⁺ CAF-CXCL5-CLGN axis that drives LUAD chemoresistance and suggest that CLGN inhibition could be a promising therapeutic strategy to overcome chemoresistance in advanced LUAD.