Cancer-associated fibroblasts mediate differentiation of myeloid-derived suppressor cells in pancreatic cancer through IL-6/STAT3 pathway / 第二军医大学学报

ABSTRACT

Objective To explore the mechanism and biological significance of differentiation of myeloid-derived suppressor cells (MDSCs) mediated by cancer-associated fibroblasts (CAFs) in the pancreatic ductal adenocarcinoma (PDAC), so as to provide theoretical and experimental basis for revealing the roles of CAFs and MDSCs in promoting the progression of pancreatic cancer by remodeling the pancreatic cancer microenvironment. Methods We isolated and purified primary CAFs from PDAC tumor tissues, and screened the up-regulated cytokines in CAFs by quantitative real-time PCR and enzyme-like immunosorbent assay. The human foreskin fibroblasts (HFFs) were used as controls. Human peripheral blood mononuclear cells (PBMCs) were cultured with supernatant of CAFs and HFFs, respectively. The differentiation of PBMCs was observed and the mechanisms of the above cytokines in regulating the differentiation and recruitment of MDSCs were studied. Results The biomarkers (α-smooth muscle actin [α-SMA] and fibroblast activation protein a [FAPa]) were detected in the isolated primary CAFs, but not found in the HFFs. The expression levels of interleukin 6 (IL-6), stromal cell-derived factor 1 (SDF-1) and monocyte chemotactic protein 1 (MCP-1) in the culture supernatant were significantly gradually increased in the CAFs than those in the HFFs (all P0.01). Compared with culture supernatant of HFFs, the culture supernatant of CAFs promoted more PBMCs to differentiate into CD13-high expression neutrophil-like MDSCs (CD13hi-nMDSCs; P0.01). IL-6 human recombinant protein alone in the co-culture system could induce the differentiation of PBMCs into CD13hi-nMDSCs (P0.01). SDF-1 or MCP-1 human recombinant protein alone could not induce the increase of CD13hi-nMDSCs subpopulation. IL-6 neutralizing antibody or signal transducer and activator of transcription 3 (STAT3) blocker FLLL32 could significantly inhibit the differentiation induced by the culture supernatant of CAFs (P0.05). Conclusion CAFs can promote the differentiation of PBMCs into CD13hi-nMDSCs via the IL-6/STAT3 pathway.