ABSTRACT
Objective:To analyze the effect of microRNA-506 (miR-506) on M2 macrophages polarization and immune intervention in pancreatic cancer mice.Methods:Macrophages from peripheral blood of healthy volunteers were cultured in vitro, polarized into M1 or M2 type macrophages, and transfected with miR-506 or control sequence (miR-ctrl), respectively. Polarized macrophages from M1+ miR-ctrl group, M1+ miR-506 group, M2+ miR-ctrl group and M2+ miR-506 group were collected. The relative expression of marker genes of M1 and M2 type macrophages of four groups were analyzed by qRT-PCR. The characteristic functions of M1 and M2 type macrophages of four groups were also detected, such as phagocytosis and nitric oxide (NO) synthesis (characteristic function of M1 type macrophages), arginase 1 activity and the secretion of vascular endothelial growth factor (VEGF), transforming growth factor-β (TGF-β), interleukin-10 (IL-10) (characteristic function of M2 type macrophages). Sixty healthy male C57BL/6 mice without specific pathogen, weighing 20-25 g, were randomly divided into miR-ctrl programmed death-1 (PD-1) group, miR-506 PD-1 group, miR-ctrl iso group, and miR-506 iso group. They were injected with miR-506, miR-ctrl, PD-1 antibodies, and isotype control antibodies, with 15 in each group. The tumor volume, tumor weight, Ki-67 and interferon γ expression were analyzed three weeks later. Results:Compared with M2+ miR-ctrl group, the relative expression of M1 type macrophage marker genes increased, and the relative expression of M2 type macrophage marker genes decreased in M2+ miR-506 group, with significant difference (all P<0.05). Compared with M2+ miR-ctrl group, the phagocytic function and NO synthesis of macrophages in M2+ miR-506 group increased, the activity of arginase 1 and the secretion of VEGF, TGF-β and IL-10 decreased, with significant difference (all P<0.05). There was no significant differences in tumor weight, volume, Ki-67, and interferon γ expression between miR-ctrl iso and miR-ctrl PD-1 group (all P>0.05). The tumor weight, tumor volume and Ki-67 in miR-506 PD-1 group were lower than those in miR-ctrl PD-1 group [(0.32±0.13) g vs (0.85±0.24) g; (0.72±0.23) cm 3 vs (2.03±0.21) cm 3; (25.9±10.3)% vs (55.6±12.5)%], while interferon-γ expression was significantly higher than that in miR-ctrl PD-1 group [(122.4±15.3) ng/g vs (82.4±22.2) ng/g] (all P<0.05). Conclusion:miR-506 inhibits the polarization of M2 macrophages and increases the anti PD-1 immunotherapy sensitivity in pancreatic cancer.