Figure 6. Mechanisms of recruitment of Gr-1+CD11b+ cells to the tumor microenvironment.

A: Elevated production of CXCL5 in cell culture supernatant of PyVmT/Tgfbr2^MGKO mammary carcinomas. B: In vitro migration of Gr-1+CD11b+ cells in response to CXCL5. Gr-1+CD11b+ cells migration after 6–8 hr incubation were counted and plotted. Shown is one of the representative experiments of three performed. C: Inhibition of Gr-1+CD11b+ cell recruitment to PyVmT/Tgfbr2^MGKO tumors with CXCR2 antagonism. Percentage of Gr-1+CD11b+ cells in all cells from PyVmT/Tgfbr2^MGKO and control tumors were plotted. Mice bearing PyVmT/Tgfbr2^MGKO and control tumors were treated with a CXCR2 specific antagonist SB-265610 at 2 mg/kg/day for two weeks through I.P. D: Flow cytometry analysis of CXCR4 expression in infiltrating Gr-1+CD11b+ cells from 4T1 tumors as well as PyVmT/Tgfbr2^MGKO tumors, compared with those from spleens of the same tumor-bearing mice (as labeled). Histogram of CXCR4 expression was gated on Gr-1+CD11b+ double positive cells. Shown is one of the representative mice analyzed, n=3–5 mice per group. E: In vitro migration of Gr-1+CD11b+ cells in response to SDF-1. Gr-1+CD11b+ cells migration after 6–8 hr incubation were counted and plotted. Shown is one representative experiment of three performed. F: PyVmT/Tgfbr2^MGKO tumor metastasis with blockade of CXCR2 or CXCR4 alone or both. Tumor nodules in lung were counted after mice bearing 14-Day tumors were treated with CXCR2 or CXCR4 antagonists or both for 3 weeks. All results are presented as the mean ± SE.