CXCR4 and neoplasm: Autocrine activation of PDGFRα induced tumorigenesis and metastasis in advanced skin squamous cell carcinomas (SCCs) via upregulation and secretion of SDF-1α, and then SDF-1/CXCR4 induced PDGFR-induced tumor cell invasion and metastasis (Bernat-Peguera et al., 2019).