CXCL12 and cancer: Both the PDGF/PDGFR and SDF-1/CXCR4 signaling pathways are involved in mediating EMT and angiogenesis, and thus, the regulation of tumor growth, invasion, and metastasis (Petit et al. 2007; Stumpf et al. 2018; Hu et al. 2014; Lange et al. 2018; Peng et al. 2017), but this is the first time the secretion of PDGFR-α (by protein microarray and ELISA) from cancer cells has been detected.