CXCL12 and cancer: The interaction of CXCR4 and its ligand stromal-derived factor 1α (SDF-1α, also known as CXCL12) mainly secreted by stromal cells promotes several aspects of cancer progression including angiogenesis, metastasis, relapse, drug resistance, and survival (Teicher and Fricker, 2010; Mortezaee, 2020).