Vasoactive Intestinal Peptide Promotes Immune Escape of MKN45 Cells by Inhibiting Antigen-Presenting Molecules of Dendritic Cells In Vitro

To investigate vasoactive intestinal peptide (VIP) effect on dendritic cells (DCs) to gastric cancer (GC) cells in vitro involving immune escape mechanism of GC, we observed DC-SIGN (CD209), Ii chain (CD74), MHC-II and collaborative costimulatory molecules CD40, CD80, CD86 expressions in DCs, which co-incubated with GC cells and VIP. Human umbilical cord blood (HUCB) were obtained from healthy volunteers and human mononuclear cells were isolated from HUCB by density gradient centrifugation. Monocytes were purified from mononuclear cells using adherence separation and were treated with recombinant human granulocyte–macrophage colony-stimulating factor (rh GM-CSF), recombinant human interleukin-4 (rh IL-4) to induce immature monocyte-derived DCs (moDCs). Recombinant human tumor necrosis factor (rh TNF-α) was added on the 5th day to induce mature moDCs. Mature moDCs were collected on the 10th day, and co-incubated with MKN45, VIP and mannan, respectively. CD1a and CD83 expressions were detected by immunocytochemistry. VIP, VPAC1, CD209, CD74, MHC-II, CD40, CD80 and CD86 expressions of DCs were detected by immunocytochemistry and RT-PCR. VPAC1 was detected in DCs, but VIP did not detected in DCs. When DCs were co-incubated with MKN45 cells, MKN45 cells could inhibit DCs’ expressions of CD209, CD74, MHC-II, CD40, CD80 and CD86 in the mRNA and protein levels (p < 0.05), and VIP could further inhibit CD209, CD74, MHC-II, CD40, CD80 and CD86 expressions of DCs in the mRNA and protein levels (p < 0.05). The inhibition could not been reversed by mannan. CD209 was positively correlated with CD74, MHC-II, CD40, CD80 and CD86 in mRNA level and protein expression intensity in DCs. VIP could inhibit CD209, CD74, MHC-II, CD40, CD80 and CD86 expressions of DCs, and inhibit antigen-presenting ability of DCs. VIP may promote immune escape of GC by inhibiting CD209, CD74, MHC-II, CD40, CD80 and CD86 expressions of DCs.