FAK activity in cancer-associated fibroblasts is a prognostic marker and a druggable key metastatic player in pancreatic cancer

Cancer-associated fibroblasts (CAFs), although considered as the most abundant pancreatic ductal adenocarcinoma (PDAC) stromal cells playing a critical role in tumor progression and chemoresistance, are not yet directly druggable. Here we report that focal adhesion kinase (FAK) activity (evaluated based on 397 tyrosine phosphorylation level) in CAFs is highly increased compared to its activity in fibroblasts from healthy pancreas. Fibroblastic FAK activity is an independent prognostic marker for disease free and overall survival of PDAC patients (cohort of 120 PDAC samples). Genetic inactivation of FAK within fibroblasts (FAK-kinase-dead, KD) reduces fibrosis and immunosuppressive cell number within primary tumor and dramatically decreases tumor spread. Mechanistically, pharmacologic and genetic fibroblastic FAK inactivation reduces fibroblast migration/invasion, decreases extracellular matrix (ECM) expression and deposition by CAFs, and negatively impacts M2 macrophage polarization and migration. Thus, FAK activity within CAFs appears as an independent PDAC prognostic marker and a druggable driver of tumor cell invasion.