CXCL12 and neoplasm: To substantiate the functional significance of CXCL12-CXCR4 in the recruitment of mast cells, mast cell chemotaxis assay was performed and showed that TTCS induced significantly more tumor-infiltrating mast cell migration than NTCS from the same GC patients, and this effect was lost upon pre-treatment with neutralizing antibodies against CXCL12 and/or CXCR4 (Fig. 2d).