94 Interestingly, ECM stiffness correlated with the level of inclusion of an alternatively spliced region in the fibronectin pre-mRNA known as the extra domain B (ED-B).94 Inclusion of ED-B is prevalent in numerous types of aggressive solid tumors and is considered a biomarker of tumor angiogenesis.95–97 Endothelial cells plated on stiff substrates (10 kPa) exhibited higher levels of fibronectin variants containing ED-B versus total fibronectin than cells plated on compliant substrates (1 kPa). This evidence concerns the gene FN1 and neoplasm.