Activation of mast cells by SCF is necessary for their tumor-promoting effect. (A) SCF-knockdown retards tumor growth. Mice (n = 8 per group) were inoculated with SCF-knockdown H22 cells and control WT H22 cells, respectively. The growth of tumor was monitored. (B,C) Mice (n = 8 per group) were inoculated with SCF-knockdown H22 tumor cells. When tumor size reached approximately 5 × 5 mm2, the mice received BMMCs either by intravenous (i.v.) injection or by intratumor (i.t.) injection (B), or received the intratumor injection of BMMCs pretreated with different concentrations of SCF and anti–c-kit antibody (20 μg/mL) as indicated (C). The growth of the tumor was promoted only by the intratumor injection of MCs pretreated with a higher concentration of SCF (200 ng/mL), which was abolished by anti–c-kit antibody. Error bars represent SD.
