Matrix stiffness-driven cytoskeletal remodeling and tumor progression in anaplastic thyroid cancer via integrin-focal adhesion kinase signaling.

Anaplastic thyroid cancer (ATC) is a highly lethal malignancy characterized by rapid progression and therapeutic resistance. This study uncovers the pivotal role of extracellular matrix (ECM) stiffness in driving ATC aggressiveness through mechanotransduction mediated by the Integrin α6β4/Focal Adhesion Kinase (FAK) axis. By engineering collagen-coated polyacrylamide hydrogels with tunable rigidity, we demonstrated that high ECM stiffness (60 kPa) markedly enhanced ATC cell proliferation, clonogenicity, migration, and invasion. Mechanistically, stiff matrices induced cytoskeletal reorganization, activated RhoA/Rac1/Cdc42 signaling, and upregulated Integrin α6β4-FAK pathway components, as validated by transcriptomic, proteomic, and functional assays. Pharmacological inhibition of FAK reversed stiffness-dependent tumor-promoting effects in vitro. In vivo, mice injected with tumor cells pre-cultured on high-stiffness ECM-mimicking hydrogels exhibited accelerated subcutaneous tumor growth and increased lung metastatic burden, which were significantly attenuated by FAK-targeted therapy. These findings establish ECM stiffness as a biomechanical determinant of ATC progression and metastasis, offering novel insights into microenvironment-driven malignancy and highlighting FAK as a promising therapeutic target to disrupt mechanosignaling in ATC.