Mast cells promote tumor growth with SCF/c-Kit–mediated chemotactic migration as the prerequisite. (A) SCF induces the migration of mast cells (MCs). The migration of MCs in transwell assay was determined in the presence of tumor tissues, antibodies, or SCF. *P < .05 compared with tumor tissue group. (B) Infiltration of circulating MCs into the tumor. CFSE-labeled BMMCs with or without antibodies were injected into tumor-bearing mice by the tail vein. The peripheral tumor tissues were surgically excised from mice 24 hours after the injection, and frozen sections were prepared and analyzed by fluorescence microscopy. (C) Mast cells promote tumor growth. BMMCs were injected into tumor-bearing mice by intravenous injection. Bone marrow cells were used as control. The growth of tumor was monitored. (D) Survival rate follow-up after the intravenous injection of BMMCs. The survival period of tumor-bearing mice in the BMMC injection group was significantly shortened, compared with that in the control groups (n = 12; P < .05, Kaplan-Meier analysis). The data were the representative of 2 independent experiments in which the similar results were obtained. (E) Dependence of tumor-promoting effect of MCs on the SCF/c-Kit axis. BMMCs, with or without antibodies, were injected into tumor-bearing mice by the tail vein. Both of 2 antibodies abolished the tumor-promoting effect of MCs. *P < .05, compared with the control group. Error bars represent SD.