Ranking among the most lethal tumour entities, pancreatic duct
adenocarcinoma cells invade neighbouring tissue resulting in high incidence of
metastasis. They are supported by tumour stroma fibroblasts which have undergone differentiation into cancer-associated fibroblasts (CAFs). Stiffness of cell substratum,
cytokines, such as
transforming growth factor-β (TGF-β), and stromal matrix
proteins, such as laminin-332, are factors which promote CAF differentiation. In a spheroid culture system, differentiation of CAFs was analysed for laminin-332 production,
laminin-binding
integrin repertoire, adhesion and migration behaviour, and, in heterospheroids, for their interplay with the pancreatic duct
adenocarcinoma AsPC-I cells. Our data reveal that CAFs produce laminin-332 thus contributing to its ectopic deposition within the tumour stroma. Moreover, CAF differentiation correlates with an increased expression of α3β1
integrin, the principal laminin-332-receptor. Beyond its role as novel CAF marker
protein,
integrin α3β1 crucially determines differentiation and maintenance of the CAF phenotype, as knock-out of the
integrin α3 subunit reversed the CAF differentiated state. AsPC-I cells co-cultured in heterospheroids with
integrin α3-deficient CAFs invaded less than from heterospheroids with wild-type CAFs. This study highlights the role of
integrin α3β1 integrin-laminin-332 interaction of CAFs which promotes and sustains differentiation of CAFs and promotes
carcinoma invasion.