TABLE 1.

Research progress of related treatment.

Classification	Drug	Mechanism	Result	References
Preclinical studies	Olaparib	Inhibition of MDSCs recruitment through the SDF1α/CXCR4 axis	Improvement of anti-tumor efficacy of CAR-T cells in mice with BC	Sun et al. (2021)
	Entinostat	Inhibition of MDSCs through activation of STAT3, also drives changes in the phenotype and function of tumor-infiltrating MDSCs and reduces the production of inhibitory factors through the NF-kB and OXPHOS pathways	Improvement of immunosuppressive TME and enhancement of response to ICIs in BC patients	Sidiropoulos et al. (2022)
	Melatonin and Doxorubicin	Immunomodulatory effects by decreasing MDSCs cell expression	Reduction of primary BC tumor growth and distant metastasis	Tanriover et al. (2022)
	Nifuroxazide	Reduction of MDSCs in the lungs of BC mice	Inhibition of BC lung metastasis	Yang et al. (2015)
	Ibrutinib	Induces conversion of MDSCs to DCs, increases the number of more mature DCs, and decreases the number of MDSCs	Reducing tumor burden, inhibiting BC progression and metastasis	Varikuti et al. (2020)
	Sulforaphane	Reduced PGE2 secretion triggered switching of MDSCs to an immunogenic phenotype and enhanced anti-tumor activity of CD8+ T cells	Reversing the BC immunosuppressive microenvironment and assisting in improving chemotherapy efficacy	Rong et al. (2020)
	Cabozantinib	Depleting MDSCs	Improved efficacy of anti-HER2 antibody immunotherapy in the 4T1-HER2 mouse BC model	Bakhtiarvand et al. (2022)
	Metformin	Significantly reduced M-MDSCs (CD11b+Gr-1+) and regulatory T cells (Tregs, CD4+CD25+Foxp3+), resulting in suppressed expression of the immune checkpoint molecule PD-1 on T cells	Enhanced local antitumor activity in BC TME	Jiang et al. (2023)
	ACT001	Upregulation of 2-associated X protein expression in B-cell lymphoma significantly reduced GM-CSF levels in 4T1 tumors, decreased the number of MDSCs, and inhibited angiogenesis	Induction of apoptosis in 4T1 cells	Liu et al. (2020)
	Aspirin	Inhibit platelet aggregation	Reduced BC invasion and metastasis	Pulcinelli et al. (2004)
	Ticagrelor	Significantly reduced tumor cell-platelet aggregation in the lungs	reduces tumor growth and metastasis	Gareau et al. (2018)
	Tamoxifen	Reduced platelet activation response and reduced vascular endothelial growth factor release	Reduced BC angiogenesis and metastatic potential	Johnson et al. (2017)
Clinical studies	(UMIN000022494) propagermanium	Inhibition of PMN formation by decreasing CCL2 and IL-6 concentrations	Inhibition of metastasis in perioperative patients with primary BC	Masuda et al. (2020)
	(NCT01740427 and NCT01942135) CDK4/6 inhibitor palbociclib and endocrine therapy	Significantly inhibited T-cell exhaustion and reduced MDSCs	CDK4/6 inhibitors enhance systemic anti-tumor immunity and are able to reduce patients' dNLR; neutrophil/[leukocyte-neutrophil] values thus predicting a better PFS.	Kim et al. (2023)
	Aspirin	Reversal of platelet activation of Akt signaling pathway in tumor cells leads to decreased IL-8 secretion	Ability to impair BC cell invasion, reduce the incidence of cancer over the age of 3, and enable tumor patients to demonstrate a higher probability of survival	Rothwell et al. (2012)
TCM	Ginsenoside Rg3	Inhibition of STAT3-dependent pathways, tumor-derived cytokines and NOTCH signaling pathways	Inhibition of cancer stemness and EMT induced by MDSCs in BC	Song et al. (2020)
	Epigallocatechin-3-gallate	Significantly reduced MDSCs accumulation and increased the proportion of CD4+ and CD8+ T cells in the spleen and tumor sites of 4T1 BC mice through the Arg-1/iNOS/Nox2/NF-κB/STAT3 signaling pathway	Improvement of BC immunosuppressive microenvironment	Xu et al. (2020)
	Artemisinin	Promoting T cell activation and suppressing immunosuppression of Tregs and MDSCs in tumors	Impedes the growth of 4T1 tumors in the body	Cao et al. (2019)
	α-Hederin	Disruption of PAF/PTAFR Axis Cascade STAT3/MMP-2 Expression	Inhibition of TAPs-activating factor-induced metastasis	Cao et al. (2022)
	Caulis Spatholobi Extract	Reversal of EMT triggered by tumor cell-platelet interaction by blocking platelet-derived PDGF-B release	Significantly inhibited BC invasion and metastasis	Sun et al. (2020)
	Shuang shen granules	Attenuates differentiation of BMCs into MDSCs and reduces CD11b+Ly6C + Ly6G + cells by inhibiting the mTOR/S6K1/Myc signaling pathway	Inhibition of BC lung metastasis	Wei et al. (2021)
	Shugan Jianpi Formula	Reduction of CD8+ T-lymphocyte apoptosis and tumor cell activity, enhancement of immune surveillance and inhibition of MDSCs proliferation	Modulation of the BC immunosuppressive microenvironment leading to prolonged survival of tumor-bearing mice	Lu et al. (2017)
	Xuanhusuo San	Reducing the ratio of PMN-MDSC in spleen, decreasing CD11b and Ly6G co-expression in spleen, down-regulating G-CSF mRNA level in 4T1 cells, impeding the differentiation of MDSC to PMN-MDSC through downregulation of G-CSF, and reconstructing the myeloid microenvironment of spleen	Fulfillment of the anti-BC role	Mao et al. (2023)
	Baoyuan Jiedu decoction	Inhibition of TGF-β, Smad2, Smad3, p-Smad2/3, Smad4, and CCL9 protein and gene expression in the TGF-β/CCL9 signaling pathway	Inhibition of MDSCs accumulation in the PMN of lungs	Tian et al. (2020)
New technologies	17-AAG	Significantly increased tumor-infiltrating T cells, decreased hypoxia levels, and reduced suppressive lymphocytes in the TME, such as tumor-associated macrophages and MDSCs	Reversing the BC immunosuppressive microenvironment and facilitating checkpoint blockade immunotherapy	Liu et al. (2020)
	LMWH-ATRA	Inhibits the recruitment of MDSCs by competitive binding to PS on the surface of VECs, while hydrophobic segment ATRA promotes the depletion of MDSCs by inducing their differentiation	Significantly improves the inflammatory and immunosuppressive microenvironment at lung and tumor sites and inhibits PMN formation	Lu et al. (2022)
	Nano-DOX	downregulated G-CSF and inhibited the expression and phenotype of MDSCs induced by 4T1 cells	Inhibition of 4T1 cells	Yuan et al. (2019)
	liposomal doxorubicin and liposomal vaccine containing E75 combination treatment	Reduced the expression of MDSCs and the level of ROS, as well as the expression of MDSCs-related genes of Arg1, iNOS, S100A8, and S100A9. Enhanced INF-γ production by immune splenocytes and enhanced the proportion of anti-tumor CD8+ and CD4+ T cells	Improved therapeutic effects of BC	Zamani et al. (2020)
	FA-CD@PP-CpG synergized with phototherapy (Phototherapy) and docetaxel	Promotes CTL infiltration, inhibits MDSC, and effectively polarizes MDSC toward the M1 phenotype	Enhancing the efficacy of anti-PD-L1 antibodies to enhance immunotherapy against BC	Chen et al. (2019)
	PM-NVs	PM-NVs efficiently accumulate at tumor sites and promote TRAIL interaction with platelet membranes	Significantly inhibited BC progression and reduced lung metastasis	Hu et al. (2015)