CXCR4 and neoplasm: These ideas are supported by the findings of Tan et al. who propose that overexpression of CXCR4 by tumor cells in the hepatic metastatic microenvironment stimulates the production of CXCL12 by stellate cells, which through a paracrine action, stimulates the secretion of TGF-β1 by tumor cells, necessary for the differentiation of hepatic stellate cells into CAFs [212].