TABLE 3.

Mechanisms of antitumor drug resistance mediated by MDSCs.

Tumor type	Drug resistance	Mechanisms	References
Breast cancer	Doxorubicin	Cancer cells secreting PGE2 and activating PGE2/miR-10/AMPK signals within MDSCs.	Rong et al., 2016
Cervical cancer	Platinum-based chemotherapy	Cancer cells expressing G-CSF, causing MDSCs accumulation and T cell suppression.	Kawano et al., 2015
HCC	5-FU, ADM	Cancer cells-derived IL-6 enhancing the activity and expansion of MDSCs.	Xu et al., 2017
Melanoma	PLX4720	Melanomas inducing expansion of CCR2-expressing monocytic-MDSCs in the TME by producing CCL2, activating MDSCs through MAPK signaling.	Steinberg et al., 2017
MM	5-FU, bortezomib	MDSCs inducing AMPK activation and MCL-1 and BCL-2 expression in myeloma cells.	De Veirman et al., 2019
Prostate cancer	Castration-resistance	IL-23 secreted by MDSCs activating IL-23-IL-23R-RORγ axis of androgen receptor pathway in prostate cancer cells.	Calcinotto et al., 2018

PGE2, prostaglandin E2; G-CSF, granulocyte-colony stimulating factor; HCC, hepatocellular cancer; 5-FU, 5-fluorouracil; ADM, adriamycin; MM, multiple myeloma.