CXCL12 and neoplasm: For example, CFA secretion of transforming growth factor-β (TGF-β) potentiates CXCR4 stimulation of AKT signaling in human prostate epithelial cells, which indicates that synergism between TGF-β, CXCL12, and CXCR4 in tumor stroma contributes to carcinogenesis (Ao et al., 2007).