OBJECTIVETo investigate the synergistic effect between the N-terminus domain of the a2 isoform of vacuolar ATPase (a2NTD) and macrophage colony-stimulating factor (M-CSF) on modulating macrophage polarization and the impact of polarized macrophages on proliferation of gastric cancer cells.

METHODSPeripheral blood mononuclear cells were derived from healthy donor and induced into macrophages. Then macrophages were randomly divided into four groups: the control group (RPMI 1640), the experimental group I (M-CSF 100 μg/L), the experimental group II (a2NTD 500 μg/L) and the experimental group III (a2NTD 500 μg/L plus M-CSF 100 μg/L). After stimulation for 48 hours, double color immunofluorescence cytochemistry was adopted to detect the expression of cell membrane molecules on macrophages; ELISA was used to measure the secretion of cytokines IL-10 and IL-12; CCK-8 assay was used to evaluate the impact of macrophages on proliferation ability of gastric cancer cell strain SGC-7901.

RESULTSThe expression of CD68, also known as macrophage surface antigen, was detected on macrophage membrane in all four groups (+). The mean absorbance (A) was 0.092 ± 0.005 in control group, 0.095 ± 0.006 in group I, 0.094 ± 0.005 in group II, 0.094 ± 0.005 in group III, and no significant differences were observed among 4 groups (all P>0.05). Meanwhile, the expression of CD206, which mainly exists on M2 macrophage membrane, was hard to detect in control group (-) with A 0.025 ± 0.004; it was normal in groupI and group II (+) with A 0.191 ± 0.012 in group I and 0.197 ± 0.136 in group II (P=0.212), and it was up-regulated significantly in group III (+++) with A 0.285 ± 0.011. There were significant differences between either two groups except group I and group II (all P<0.01). Secretion of IL-10 in group I and group II [(85.65 ± 13.64) ng/L and (87.77 ± 14.25) ng/L] was significantly higher compared with control group [(71.67 ± 7.56) ng/L, P<0.01]. Secretion of IL-12 in group I and group II [(9.91 ± 1.50) ng/L and (10.15 ± 1.80) ng/L] was significantly lower compared with control group [(16.87 ± 1.10) ng/L, P<0.01]. Secretion of IL-10 in group III [(116.98 ± 14.27) ng/L] was the highest, and secretion of IL-12 [(5.31 ± 0.88) ng/L] was the lowest (all P<0.01). There was a synergistic effect between a2NTD and M-CSF on the secretion of both IL-10 and IL-12. Elevated proliferation of gastric cancer cell strain SGC-7901 was detected in all four groups, in which group III showed the greatest impact compared with other 3 groups (P<0.01).

CONCLUSIONSa2NTD and M-CSF show a synergistic effect in modulating macrophage phenotype and the secretion of IL-10 and IL-12. The polarized macrophage can significantly enhance proliferation of gastric cancer cell strain SGC-7901.