Figure 6
From: Zoledronic acid impairs myeloid differentiation to tumour-associated macrophages in mesothelioma
ZA changes M1:M2 ratio and increases MO-MDSC in tumour-bearing mice. Mice were i.p. inoculated with AC29 tumour cells and treated daily with s.c. injection of ZA. (100 μg kg−1) or PBS as a control (n=6 each group). Mice were killed 25 days after tumour injection. The number of MDSC was analysed according to the subdivision as described in Figure 5. Macrophages were subdivided into M1 and M2 macrophages based on the co-expression of CD206, F4/80 and MHCII on the membrane. (A) Myeloid cell types in spleen of tumour-bearing mice. MO-MDSC were significantly increased in the spleen of ZA-treated animals (*P=0.0312). No difference was found in the percentage of PMN-MDSC and Gr-1low-MDSC (*P=0.77 and 0.75). The percentage of total macrophages in the spleen of ZA-treated mice was significantly lower compared with untreated mice (*P=0.0091). In the spleen of tumour-bearing mice, although not significant there was a trend towards a reduction in both M1 and M2 macrophages in ZA-treated mice. In addition, ZA treatment significantly lowers the MFI of CD206 on M2 macrophages (*P=0.0095). (B) Myeloid cell types in effusion fluid of tumour-bearing mice. MO-MDSCs were significantly increased in the effusion fluid of ZA-treated animals (*P=0.034). No difference was found in the percentage of PMN-MDSC and Gr-1low-MDSC or macrophages (*P=0.72 and 0.74). A significant increase in M1 macrophages was found (*P=0.035), and also an increase was found in the number of M2 macrophages (*P=0.33). ZA shifts the balance, leading to a significant difference in the ratio of M1:M2 macrophages (*P=0.011); a trend towards a lower MFI of CD206 was observed (*P=0.114). (C) Cytokines in effusion fluid of tumour-bearing mice. ELISA was performed on effusion fluid of tumour-bearing mice treated with ZA or PBS as a control. A significant increase in IL-6, IL-12 and IL-1β was found in ZA-treated mice (*P=0.049, 0.042 and 0.005, respectively). A significant reduction in VEGF and CCL-2 (MCP-1) expressions was found in ZA-treated mice (*P=0.05 and 0.039).
