CXCL12 and neoplasm: Cancer-associated fibroblasts (CAFs) are the most abundant cell types in the tumor microenvironment; they secrete various cytokines, such as CXCL12, IL-1, IL-8, IL-10, IL-6, TNF-α and MCP-l, through the paracrine pathway to act on tumor cells and promote tumorigenesis and the development of the tumor [6–10].