Specifically, during melanoma progression, activated fibroblasts secrete abundant structural ECM proteins, such as collagens (especially type I collagen), fibronectin, laminin, and various proteoglycans accumulating around the tumors and leading to the formation of a denser extracellular matrix, rich in collagen fibers or, in some cases, a high proteoglycan content stroma [50]. The gene discussed is FN1; the disease is melanoma.