The effect of Phloretin on human γδ T cells killing colon cancer SW-1116 cells

Objective: To explore the effect and mechanism of Phloretin on human gamma delta T cells killing colon cancer SW-1116 cells. Methods: gamma delta T cells were amplified in vitro from human peripheral blood mononuclear cells through isopentenyl pyrophosphate method (IPP). After cocultured different concentrations of Phloretin with gamma delta T cells or SW-1116 cells for 48 h respectively, MTT assay was used to test the growth curve of these two cells; Flow cytometry to test the expression of Granzyme B (GraB), perforin (PFP), CD107a and IFN-gamma of gamma delta T cells; Lactate dehydrogenase (LDH) release assay to test the cytotoxic activity of the gamma delta T cells on SW-1116 cells; and Western blot to test the Wnt3a expression of the gamma delta T cells. Results: After cultured with IPP for ten days, the percentage of gamma delta T cells increased from 3.31 +/- 3.00% to 78.40 +/- 1030%. Compared to the control group, when the concentration of Phloretin increased from 235 mu g/ml to 18.75 mu g/ml, it could significantly proliferate the gamma delta T cell growth (P<0.05) and inhibit the growth of SW-1116 cells in dose-response, and the expression of GraB, PFP, CD107a and Wnt3a significantly increased (P<0.05). Significant positive relationships were observed among CD107a and PFP, GraB, cytotoxicity (P<0.05). The percentage of IFN-gamma producing gamma delta T cells treated with Phloretin was significantly higher than control group. Conclusion: Phloretin can enhance the killing effect of gamma delta T cells on SW-1116 cells; the mechanism may be that Phloretin could proliferate the gamma delta T cell growth, increase the expression of PIP and GraB, activate the Wnt signaling pathway, and produce higher level of IFN-gamma. Indeed CD107a expression probably correlates quite well with antitumor activity. (C) 2012 Elsevier B.V. All rights reserved.