Figure 3.

Loss of IL33/ST2 signaling alters the tumor microenvironment. Analysis of tumors derived from murine MC38 colon cancer cells by fluorescent confocal microscopy showed that tumors are highly infiltrated with CD11b⁺Gr1⁺ myeloid derived suppressor cells (MDSCs) in wild type (WT) C57Bl/6 mice (top panel, WT). Loss of host ST2 receptor in ST2 knockout mice resulted in significant reduction of MDSCs in the TME and inhibition of tumor growth (lower panel, ST2^−/−). Macrophages, mast cells, and T_regs were similarly reduced in ST2^−/− mice indicating that loss of IL33/ST2 signaling alters the composition of the TME (Larsen and Peña, unpublished data; images were taken at 40× magnification on a Zeiss LSM510 META confocal scanning laser microscope, **** indicates a p value of < 0.0001).