Pancreatic ductal adenocarcinoma (PDAC) is characterized by high mortality and the frequent emergence of chemoresistance, particularly to gemcitabine (GEM). Recent studies have indicated that tumors exhibit increased malignancy following the acquisition of chemoresistance. However, the underlying molecular mechanisms remain poorly understood. This study aimed to elucidate the mechanisms by which PDAC cells acquire GEM resistance and how this resistance drives cancer progression, focusing on identifying the key molecular drivers involved in these processes. We established GEM-resistant PDAC cell lines (GEM-Panc-1 and GEM-MIA PaCa-2) and characterized their malignant phenotypes using migration, invasion, proliferation, and sphere-formation assays, as well as in vivo models for tumor growth, tumor initiation, and metastasis. The functional role of β4 integrin (encoded by ITGB4) was evaluated using stable knockdown and overexpression systems. To investigate the regulatory mechanisms, we employed RNA sequencing, chromatin immunoprecipitation (ChIP), and promoter reporter assays. Clinical relevance was assessed using TCGA datasets and Kaplan‒Meier analysis. GEM-resistant PDAC cells exhibited enhanced invasive potential, tumorigenicity, and stemness, which coincided with the upregulation of β4 integrin. Knockdown of β4 integrin in GEM-resistant cells attenuated these malignant properties and partially restored GEM sensitivity, whereas its ectopic expression in parental cells conferred aggressive phenotypes. Clinically, high expression of ITGB4 and its ligand, the laminin-332 subunit genes (LAMA3, LAMB3, and LAMC2), correlated with poor overall survival in PDAC patients. Mechanistically, the β4 integrin/laminin-332 axis promoted cell motility and GEM resistance via Src activation. Furthermore, acquired GEM resistance epigenetically supports the activation of ITGB4 transcription, which is associated with β-catenin nuclear translocation and p300-mediated histone H3 acetylation (H3K27ac) at the ITGB4 promoter. Our findings suggest that GEM-induced β4 integrin expression, potentially supported by β-catenin/p300-mediated epigenetic remodeling, is a critical determinant of GEM resistance and PDAC progression. Targeting the β4 integrin/laminin-332/Src signaling axis may provide a promising therapeutic strategy to overcome chemoresistance and improve clinical outcomes in patients with advanced PDAC.
Kariya et al. (Fri,) studied this question.