Targeting FN1 to overcome gemcitabine resistance in gallbladder cancer: Mechanistic insights and an iRGD-modified PEG-PLGA nanoparticle delivery strategy.

Gallbladder cancer (GBC) is among the most lethal biliary malignancies because it is often diagnosed at an advanced stage, displays a highly desmoplastic tumor microenvironment, and shows intrinsic resistance to gemcitabine (GEM)-based chemotherapy. Fibronectin 1 (FN1), a major extracellular matrix component, is markedly upregulated in GBC and contributes to chemoresistance through activation of the PI3K/AKT signaling pathway. Tumor-penetrating iRGD-modified PEG-PLGA nanoparticles (iRGD-NPs) were engineered to encapsulate FN1 small interfering RNA (siRNA) for targeted stromal modulation. iRGD-NPs improved tumor penetration and enabled efficient intracellular delivery of siRNA in vitro and in orthotopic mouse models. FN1 silencing attenuated PI3K/AKT signaling, reduced tumor cell proliferation, and reshaped the immunosuppressive microenvironment by decreasing stromal density and increasing cytotoxic immune infiltration. Notably, the combination of iRGD-NPs with GEM markedly reduced tumor burden and reversed drug resistance, overcoming both intrinsic and acquired GEM resistance. These findings suggest that the nanoparticle platform may offer a strategy to remodel extracellular matrix-driven stromal barriers and enhance chemotherapy efficacy in GBC. Targeting the FN1-PI3K/AKT axis using iRGD nanoparticles may hold translational potential for other solid tumors with similar stromal-mediated resistance profiles.