CXCL12 and neoplasm: PC-derived chemokine CXCL12 (SDF-1) can trigger the EGF/CSF-1 paracrine invasion loop to mediate the co-migration of TAM and tumor cells, after binding to its receptor CXCR4 on both TAMs and tumor cells (Figure 1, process ➁) (Qian and Pollard, 2010).