CXCR4 and neoplasm: HIF proteins induce the expression of several genes involved in tumor phenotypes, such as platelet-derived growth factor (PDGF), transforming growth factor alpha and beta (TGF-α, TGF-β), matrix metallopeptidase 1 (MMP1), C-X-C chemokine receptor type 4 (CXCR4) [195].