. 2020 Aug 7;11:1526. doi: 10.3389/fimmu.2020.01526

Table 1.

The phenotype markers and functional characteristics of MDSCs as published in various studies on human CRC.

Orgin/Tumor stage	Phenotype	Suppressive activity	References
Circulating/I-IV	Lin⁻ HLA-DR⁻ CD11b⁺ CD33⁺ CD13⁺ CD115^low CD117^low CD124^low CD14⁻ CD15⁻ CD66b⁻ CD34⁻ CD39⁺ CD73⁻ PD-L1^low PD-L2⁻ PD-1⁻	MDSCs correlate with tumor metastasis. Inhibition of CFSE-labeled autologous CD3+ T cell proliferation at 2:1 ratios with MDSCs in the absence or presence of CD3/CD28 antibody stimulation for 3 days.	(26)
CD33+ from PBMC were co-cultured with SW480/SW620 cells to induce tumor MDSCs	CD33+ CD11b+ HLA-DR⁻, CD14⁺ CXCR4⁺ CD39⁺ ARG-1⁺ iNOS⁺ ROS⁺ PD-L1⁺ CD73⁻ CD117^+/− CD34^+/− CD66b^+/− CD15^weak	Tumor-induced MDSCs promoted SW480 and SW620 cell growth in a co-culture system in vitro. Tumor-induced MDSCs suppressed the proliferation of PBMCs labeled with CFSE more strongly than CD33⁺ cells cultured in medium alone.	(70)
Circulating/tumor tissue	CD33⁺ CD11b⁺ HLA-DR⁻ CD14⁺ CXCR4^+/− CD39^+/− ARG-1⁺ iNOS⁺ PD-L1⁺ ROS⁺ CD73⁻ CD117^+/− CD34^+/− CD66b^+/− CD15^weak MDSCs from tumor tissue have higher PD-L1 expression	Advanced disease stage was associated with an elevated level of circulating MDSCs; also, tumor resection reduces the level of circulating MDSCs and Tregs measured 7 days after surgery.
Circulating/IV	CD14+ HLA-DR^−/low S100A9^high iNOS⁺	–	(71)
Circulating/tumor tissue/III IV	CD124⁺CD14⁺ CD124⁺CD15⁺ tumor tissue CD15⁺ CD14⁺	Mixed lymphocyte reactions in which gamma-irradiated PBMC, CD14⁺, CD14⁻, and PMN from CRC patients were added as stimulator to responder PBMC derived from healthy donors. These experiments showed two main subpopulations with suppressive activity present among CD14⁺ monocytes in one and among PMN in the other.	(93)
Colorectal tumor/III	PMN-MDSCs CD45⁺ Lin⁻ HLA-DR⁻ CD11b⁺ CD33⁺ CD66b⁺ Mo-MDSCs CD45⁺ Lin⁻ HLA-DR⁻ CD11b⁺ CD33⁺ CD14⁺	PMN-MDSCs isolated from tumor inhibited the proliferation of activated autologous CFSE-labeled T cells and IFN-γ production in medium containing CD3 and CD28.	(94)
Circulating	CD33⁺ HLA-DR⁻ CD11b⁺ CD15⁺ CD33⁺HLA-DR⁻CD11b⁺CD15⁻ CD33⁺HLA-DR^−/lowCD14⁺	Upregulated plasma levels of IL-6 and IL-10, where IL-6 correlates with 15⁺ MDSCs and IL-10 with 15⁻ MDSCs. Also, CD15⁺ and CD15⁻ MDSCs correlated with reduced IFN-α responsiveness in CD4⁺ T cells.	(95)
Circulating/Metastasis	PMN-MDSCs CD33⁺ HLA-DR^−/low CD15⁺ CD124⁺ PD-L1⁺ CD73⁺ CD39⁺ Mo-MDSCs CD33⁺ HLA-DR^−/low− CD14⁺ PD-L1⁺ CD73⁺ CD39⁺	Accumulation of PMN-MDSCs was associated with poor prognosis; also, PMN-MDSCs have higher levels of PD-L1, CD39, and CD73 expression and a stronger immunosuppressive function than Mo-MDSCs. Reduced TNF-α production and Ki67 proliferation marker of CD3⁺ T cells, especially by PMN-MDSCs.	(89)
Circulating/I-IV	CD33⁺ CD11b⁺ HLA-DR^−/low CD15⁻CD14⁺ ARG-1⁺ CD33⁺ CD11b⁺ HLA-DR⁻ CD15⁺ CD14⁻ARG-1⁺⁺	–	(96)
Tumor tissue/I-IV	CD33⁺ CD11b⁺ HLA-DR^−/low CD15⁻CD14⁺ ARG-1⁺ CD33⁺ CD11b⁺ HLA-DR⁻ CD15⁺ CD14⁻ARG-1⁺ CD33⁺ CD11b⁺ HLA-DR⁻ CD15⁻ CD14⁻	–
Circulating	PMN-MDSCs CD14⁻CD33⁺HLA-DR⁻CD66b⁺	Human MDSCs increase fatty acid uptake and expression of FAO-related enzymes, and, in mice, inhibition of FAO blocked the tolerogenic function and immunosuppressive mechanisms of MDSCs. Inhibition of CFSE-labeled CD3⁺ T-cell proliferation after co-culturing with MDSCs from mice in the presence of anti-CD3.	(86)
Circulating	Mo-MDSCs CD14⁺HLA-DR^−/lo PMN-MDSCs CD33⁺ CD11b⁺ CD14⁻ CD15⁺ SSC^hi	Mo-MDSC population was significantly expanded in CRC patients; the immunosuppressive capacity of these cells was evaluated in a T-cell suppression assay using a 3-way allogenic mixed leukocyte reaction (MLR).	(92)
Circulating/cancer and adenoma	Total MDSCs: CD11b⁺HLA-DR^−/low CD33⁺ PMN-MDSCs: CD11b⁺HLA-DR^−/low CD33⁺ CD15⁺ CD14⁻ Mo-MDSCs: CD11b⁺HLA-DR^−/low CD33⁺ CD15⁻ CD14⁺ e-MDSCs: CD11b⁺HLA-DR^−/low CD33⁺ CD14⁻ CD15⁻	PMN-MDSCs are the main immunosuppressive population, as depletion of CD15⁺ cells spares Mo-MDSCs and eliminates most of the suppression of T-cell proliferation and interferon production. MDSC levels negatively correlated with anti-MUC1 IgG levels.	(27)