CXCL12 and cancer: Cancer cell hypoxia has become a well-established phenomenon for inducing angiogenesis, where hypoxia-driven pH changes to the TME can result in the recruitment of vascular cells by cancer cell-secreted proteins such as vascular endothelial growth factor (VEGF), transforming growth factor-beta (TGF-β), stromal cell-derived factor 1 (SDF-1/CXCL12), and angiopoietins as well as genetic material such as miRNAs (Figure 2)42–45.