Arp2/3 complex and β1 integrin drive an invasive front through extracellular matrix adaptation in pancreatic cancer.

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest malignancies, due to its aggressive invasiveness and resistance to therapy. The dense, stiff extracellular matrix, composed primarily of collagen I and basement membrane components such as collagen IV and laminin, acts as a mechanical barrier that constrains PDAC invasion. We investigated whether the actin-related protein (Arp) 2/3 complex, a key actin nucleator, is essential for PDAC cells to overcome extracellular matrix stiffness and facilitate migration. CRISPR/Cas9 knockout of the Arpc4 gene in murine PDAC cell lines derived from Kras-driven transgenic mice resulted in substantially downregulated all Arp2/3 complex members. Inactivation of Arp2/3 significantly impaired PDAC cell migration, disrupted branched tubular structure formation in collagen I, and inhibited invasive front formation in organoid culture together with tumor-associated macrophages and fibroblasts. Mechanistically, β1 integrin signaling emerged as a key regulator of Arp2/3-dependent migration through collagen-rich matrices. Clinically, elevated expression of Arp2/3 complex components correlates with poor patient survival and basal-like differentiation subtypes, underscoring its role in disease progression. This study identifies the Arp2/3 complex and β1 integrin signaling as critical mediators of PDAC invasiveness and suggests them as potential therapeutic targets for mitigating PDAC progression.