Other factors secreted by tumor cells such as platelet-derived growth factor (PDGF), fibroblast growth factor (FGF), sonic hedgehog (SHH) and interleukin (IL) 1-β promote the conversion of resident fibroblasts into CAFs through activation of signaling pathways such as the extracellular signal regulated kinase (ERK), Shh/Smo (smoothened), or nuclear factor kappa-B (NFκB) pathways [26,27,28,29]. Here, SHH is linked to neoplasm.