Figure 1. The regulation of tumor-infiltrating MDSCs by mast cells.

(A) Mast cells promoted the infiltration of MDSCs into tumor microenvironment. 5×10⁶ BMMCs with or without anti-SCF or c-kit antibodies, were injected into tumor-bearing mice by i.v. injection. Bone marrow cells were used as control. Seven days later, the tumor-infiltrating lymphocytes were used to analyze Gr-1⁺CD11b⁺ MDSCs by flow cytometry. The left shown was the representative of FACS profiles. The right shown was the combined reproducible data (n = 6). *, P<0.05, compared to control. (B) Mast cells promoted the suppressive function of MDSCs in tumor microenvironment. BMMCs with or without antibodies, were injected into tumor-bearing mice (n = 6). Seven days later, tumor-infiltrating MDSCs were isolated as described in Materials and Methods and the suppression assay was performed as described in Materials and Methods . (C and D) Mast cells upregulated the expressions of CCL2, IL-10 and IL-13 in tumor microenvironment. BMMCs were injected into tumor-bearing mice. Seven days later, tumor tissues were used to analyze CCL2, IL-10 and IL-13 expressions by real time RT-PCR (C) and ELISA (D). (E) The regulation of arginase 1 by mast cells. Lane 1–2: tumor tissues from BMMC group or control were used to analyze arginase 1 expression by real time-RT-PCR and western blot. Lane 3–5: the cultured MDSCs were treated with PBS or IL-10 (20 ng/ml) or IL-13 (20 ng/ml) for 48 h, and then used for the analysis of arginase 1 expression.