SMAD2 and neoplasm: To date, various reports have indicated the importance of several signalling pathways in governing the activated, tumour-promoting ability of CAFs, including those of TGF-β-Smad2/3, CXCL12/stromal cell-derived factor 1 (SDF-1)-CXCR4, interleukin 1β (IL-1β)-NF-κB, platelet-derived growth factor (PDGF)-PDGF receptor (PDGFR), phosphatase and tensin homologue (Pten)-v-ets erythroblastosis virus E26 oncogene homolog 2 (Ets2) and Sonic hedgehog (Shh)-Smoothened (Smo) [24,38,48,49,50].