CXCL12 and neoplasm: TAMs participate in the tumour angiogenesis by secreting pro‐angiogenic factors, including VEGF‐A, EGF, PlGF, TGF‐β, TNF‐α, IL‐1β, IL‐8, CCL2, CXCL8 and CXCL12, and enable tumour metastasis by up‐regulated N‐cadherin and Snail, whereas down‐regulated E‐cadherin.44