The prognostic effects of tumor infiltrating regulatory T cells and myeloid derived suppressor cells assessed by multicolor flow cytometry in gastric cancer patients

The prognostic effects of tumor infiltrating lymphocytes (TILs), especially regulatory T cells (Tregs) and myeloid derived suppressing cells (MDSCs) are inconclusive in gastric cancers. We investigated the frequencies of TILs including CD8+ T cells, CD45+CD4+CD25+/- FOXP3+ Tregs, CD45+CD11b+CD14+ HLA-DR-MDSCs in 28 gastric cancer tissues by using multicolor flow cytometry. In gastric cancer tissue, the percentage of Tregs among the CD4+ T cell subset was substantially increased compared to that of Tregs among peripheral blood CD4+ T cells from the controls. High frequency of CD8+ T cells among CD3+ T cells correlated with increased overall survival (OS) (p = 0.005). High frequency of Tregs among CD4+ T cells correlated with increased OS (p < 0.001), and disease-free survival (DFS) (p = 0.039) and was an independent prognostic factor in OS (Hazard ratio: 0.047; 95% confidence interval, 0.006-0.372; p = 0.004). High frequency of MDSCs among total examined cells correlated with decreased OS (p = 0.027) and was an independent prognostic factor in OS (Hazard ratio 8.601; 95% confidence interval, 1.240-59.678; p = 0.029). We have demonstrated that high levels of Tregs among tumor-infiltrating CD4+ T cells were favorable, but an increased proportion of MDSCs was an adverse independent prognostic factor in gastric cancer. Our results may provide important insights for future immunotherapy in gastric cancer.