Background
Accumulation of myeloid-derived suppressor cells (MDSCs) constitutes a key mechanism of tumor immune evasion in gastric cancer (GC). Therefore, searching for more accurate prognostic factors affecting their immunosuppressive role has become a growing interest in cancer immunotherapy research. Increased expression of microRNA-494 was noticed in MDSCs from tumor-bearing mice, suggesting another new therapeutic
Conclusion
These results indicate that tumor-derived MDSCs but not circulatory MDSCs have an immunosuppressive effect on T cells, potentially involving TGF-β mediated stimulation. Results also suggest a role for miRNA-494 in GC progression. Therefore, control of TGF-β and miRNA-494 may be used as a treatment strategy to downregulate the immunosuppressive effect of MDSCs.<br />.
Methods
Freshly obtained GC tumor tissue samples and peripheral blood were used for isolation of CD33+11b+HLADR- MDSCs cells from 40 GC patients and 31 corresponding controls using flow cytometry. MDSCs were co-cultured with isolated autologous T cells to assess proliferation and cytokine production in the presence and absence of rTGF-β. Real-time PCR and Enzyme linked immunosorbent assay were used to evaluate tumor expression of miRNA-494 and TGF-β respectively.
Results
Results showed that rTGF-β markedly increased the suppressive ability of tumor MDSCs on proliferation of autologous T cells and interferon gamma production. However, no inhibitory effect was observed for MDSCs from circulation. In addition, infiltration of MDSCs in tumors is associated with the prognosis of GC. MiRNA-494 was also extensively expressed in tumor samples with a significant correlation to MDSCs.