Figure 5

The immunological and non-immunological functions of tumor-induced MDSCs. The suppressive ability of the tumor-induced MDSCs on T cells in vitro was measured using a CFSE-labeled PBMC proliferation assay. M-MDSC: CD33⁺ cells cultured in medium alone; T-MDSC: tumor-induced MDSCs. The CFSE-labeled PBMCs were cocultured with M-MDSCs or T-MDSCs at a ratio of 1:1 or 1:2, respectively, in OKT3-coated 96-well plates. After 3 days, the cells were collected, stained with anti-human mAbs against CD4 and CD8 and quantified via flow cytometry. The proliferation of PBMCs, CD4⁺ T cells and CD8⁺ T cells was dramatically suppressed by T-MDSCs compared with M-MDSCs. (A and B) Shown are representative FACS density plots from one of 5 experiments, (C) A graph of the statistical analyses is shown. The error bars represent the SEM. *P < 0.05. (D) Tumor-induced MDSCs promoted the growth of SW480 and SW620 cells. SW480 or SW620 cells were seeded into a 96-well plate at 5 × 10³ or 2.5 × 10³ cells/well and cultured with T-MDSCs for 5 days at different ratios or in medium alone. The number of cells was counted every day. The statistical graph shows the mean value of three experiments. The number of SW480 or SW620 cells after coculture with T-MDSCs was significantly increased compared with the number of SW480 or SW620 cells cultured in medium alone. The error bars represent the SEM. *P < 0.05; **P < 0.01.