Myeloid-derived suppressor cells promote epithelial ovarian cancer cell stemness by inducing the CSF2/p-STAT3 signalling pathway.

Myeloid-derived suppressor cells (MDSCs) are known to contribute to tumour immune evasion, and studies have verified that MDSCs can induce cancer stem cells (CSCs) and promote tumour immune evasion in breast cancers, cervical cancers and glioblastoma. However, the potential function of MDSCs in regulating CSCs in epithelial ovarian cancer (EOC) progression is unknown. Our results indicated that compared to nonmalignant ovarian patients, EOC patients showed a significantly increased proportion of MDSCs in the peripheral blood. In addition, MDSCs dramatically promoted tumour sphere formation, cell colony formation and CSC accumulation, and MDSCs enhanced the expression of the stemness biomarkers NANOG and c-MYC in EOC cells during coculture. Moreover, the mechanisms by which MDSCs enhance EOC stemness were further explored, and 586 differentially expressed genes were found in EOC cells cocultured with or without MDSCs; during coculture, the expression level of colony-stimulating factor 2 (CSF2) was significantly increased in EOC cells cocultured with MDSCs. Furthermore, the depletion of CSF2 in EOC cells was successfully performed, the promotive effects of MDSCs on EOC cell stemness could be markedly reversed by downregulating CSF2 expression, p-STAT3 signalling pathway molecules were also altered, and the p-STAT3 inhibitor could markedly reverse the promotive effects of MDSCs on EOC cell stemness. In addition, the CSF2 expression level was correlated with EOC clinical staging. Therefore, MDSCs enhance the stemness of EOC cells by inducing the CSF2/p-STAT3 signalling pathway. Targeting MDSCs or CSF2 may be a reasonable strategy for enhancing the efficacy of conventional treatments. DATABASE: Gene expression data files are available in the GEO databases under the accession number(s) GSE145374.