Figure 5

Modulators of arginine metabolism alter MDSC accumulation in the blood of tumor-bearing mice. BALB/c and C57BL/6 mice were challenged s.c. with C26GM and RMA cells, respectively. The same day, mice were randomly assigned to either one of the following treatments: L-NAME or sildenafil (given i.p. or dissolved in drinking water) or vehicle (PBS; V) i.p. (see Materials and Methods section for experimental details). Tumor-bearing BALB/c and C57BL/6 mice were killed 9 and 15 day later. Recruitment of CD11b⁺Gr1^- and CD11b⁺Gr1⁺ cells in the spleen (A, C) and blood (B, D) of tumor-bearing BALB/c (A, B) and C57BL/6 mice (C, D) was investigated by flow cytometry. Histograms report the percentage of CD11b⁺ Gr1^- and CD11b⁺ Gr1⁺ cells as aggregated data (average ± SD) for the experimental groups reported in the legend of Fig. 3. Alternatively, magnetic bead sorted CD11b⁺ cells from the spleen of RMA (E) tumor bearing mice were lysed and analyzed for relative Arg enzyme activity. Student's T test: ***p < 0.001, **0.001 < p < 0.05.