Table 3.

Potential therapeutic candidates for targeting MDSCs.

Strategy	Agents	References
Promote MDSCs differentiation to increase mature leukocytes and tumor-specific T cells	ATRA, 1α,25-dihydroxyvitamin D3, DNA-methylating agent 5-azacytidine, CpG oligonucleotides, chemotherapeutic agents (paclitaxel and docetaxel), RUNX1, casein kinase inhibitor (tetrabromocinnamic acid)	(130–136)
Directly block MDSC supprression of T cells	COX-2 inhibitors, Phosphodiesterase type 5 inhibitors (tadalafil and sildenafil)	(137–142)
Inhibit migration of myeloid cells from the bone marrow to the tumor microenvironment or peripheral lymphoid organs	CXCR2, CXCR4, CSF1R, and CCR2/5 inhibitors	(143–146)
Inhibit the production of MDSCs from progenitors or induce apoptosis of circulating MDSCs	5-fluorouracil, gemcitabine, sunitinib, and zolendronate	(125, 126, 147–149)
Block the production of TDF and its reach into the bone marrow	Targeting the IL-6 receptor (tocilizumab) and HDAC-11	(86, 150)
Cytokines targeting MDSC	S100A8/A9 inhibitor (paquinimod)	(151, 152)