The paracrine activation of fibroblasts, both in the case of tumor formation and during fibrogenesis, includes the action of the factors PDGF, TGF-β, IL-6, and connective tissue growth factor (CTGF) [134,135], and in both cases, tissue epithelial cells are considered as a source of activated fibroblasts due to the epithelial–mesenchymal transition (EMT). Here, CCN2 is linked to neoplasm.