Background:Interleukin (IL)-27 has been reported to have anti-proliferate and anti-angiogenic activities on cancer cells.However,the involvement of IL-27 in malignant pleural effusion (MPE) remains unknown.Thus,in this research,we compared the immune functions of IL-27,interferon (IFN)-γ,and IL-17 on lung cancer cells and revealed the regulatory mechanism of IL-27 in MPE.Methods:The distribution ofIL-27 in both MPE and blood was evaluated by enzyme-linked immunosorbent assay and flow cytometry.The expressions of cytokine receptors and the levels of the phosphorylated signal transducer and activator of transcription (STAT) signalings were detected by flow cytometry.As well as the effects of proliferation,apoptosis,migration,and adherent activity of IL-27,IFN-γ,and IL-17 on lung cancer cells were also explored.Results:The expression of IL-27 was increased in MPE when compared with blood (147.3 ± 25.1 pg/ml vs.100.3 ± 13.9 pg/ml,P =0.04).IL-27 was noted to suppress both proliferation (18.33 ± 0.21 vs.27.77 ± 0.88,P =0.0005) and migration (1.82 ± 0.44 vs.3.13 ± 0.07,P =0.04) ofA549 cells,but obviously promoted apoptosis ofA549 cells (9.47 ± 1.14 vs.4.96 ± 0.17,P =0.02) by activating STAT1 signaling.Interestingly,IL-27 played totally opposite effects on A549 cells by activating STAT3 pathway.Moreover,IL-27 exerted different intercellular adherent activities ofA549 cells to pleural mesothelial cell monolayer by activating different STAT signalings.Conclusions:IL-27 might exert an important immune regulation on lung cancer cells in human pleural malignant environment.