Study in vitro of the down--regulating effects of As_(2)O_(3) on secretion of immunosuppressive molecules from Colon26 tumor cells
Objective To study in vitro the down-regulating effects of As_2O_3 on secretion of immunosuppressive molecules from Colon26 tumor cells. Methods Re-cultured supernatants of Colon26 after treated by As_2O_3 and the corresponding supernatants of Colon26 treated without As_2O_3 as control were collected. The concentrations of five immunosuppressive molecules(including TGF-β1, VEGF, IL-4, IL-6 and IL-10) in different supernatants were measured by quantitative ELISA. The effects of different supernatants on five immunofunctions of murine splenocytes(including NK killing and transformation induced by Con A detected by MTT, and expression levels of IL-2Rα, CD3e~+ζ~+ and CD3e~-ζ~+ detected by FCM) were determined. Results For supernatants of Colon26 treated without As_2O_3, all of five immunosuppressive molecules were found, the concentration of TGF-β1 was highest, and the significant inhibitions of five immunofunctions of murine splenocytes were showed. For Colon26 after treated by As_2O_3, the concentrations of five immunosuppressive molecules in the first re-cultured supernatant and its inhibition of the four immunofunctions except of CD3e~-ζ~+ expression decreased greatly. Compared with the first re-cultured supernatant, the concentrations of TGF-β1, VEGF and IL-4 in the second re-cultured supernatant and its inhibition of NK killing, transformation induced by Con A and CD3e~+ζ~+ expression increased highly, and others had no changes. The analysis of correlation indicated the positive correlations existed between TGF-β1 or IL-10 and inhibition of transformation induced by Con A or IL-2Rα expression, between IL-4 and inhibition of NK killing or transformation induced by Con A or CD3e~+ζ~+ expression, and not between VEGF or IL-6 and inhibition of five immunofunctions. Conclusion As_2O_3 can down-regulate secretion of immunosuppressive molecules by Colon26.The down-regulating effects on secretions of TGF-β1, VEGF and IL-4 can last for 48 h, and on secretions of IL-6 and IL-10 can last for 96 h at least. This effect should be one of anti-tumor mechanisms of As_2O_3.