M2-polarized tumor-associated macrophages promoted epithelial–mesenchymal transition in pancreatic cancer cells, partially through TLR4/IL-10 signaling pathway

Abstract

M2-polarized tumor-associated macrophages (TAMs) are key regulators of the link between inflammation and cancer. A negative correlation between infiltration intensity of M2-polarized TAMs and prognosis of pancreatic cancer has been reported. Epithelial-mesenchymal transition (EMT) is an important biological process in the progression of primary tumors toward metastasis. Inflammation-induced EMT has been previously shown, therefore, we hypothesized M2-polarized TAMs could induce EMT in pancreatic cancer. Toll-like receptor 4 (TLR4) signaling has an active role in tumor progression during chronic inflammation and the receptor is primarily expressed on macrophages. Activation of TLR4 on M2-polarized TAMs stimulates an increase in the cytokine interleukin-10 (IL-10); consequently, another aim was to investigate the potential role of TLR4/IL-10 signaling in the EMT of pancreatic cancer. Treatment with IL-4 (20 ng/ml) for 24 h successfully induced the polarization of macrophage cell line RAW 264.7 to M2 phenotype, IL-10 high , IL-12 low , and IL-23 low , and high expression of CD204 and CD206. A coculture system allowed investigation of the roles of M2-polarized TAMs and TLR4/IL-10 signaling in the EMT of Panc-1 and BxPC-3 pancreatic cancer cell lines. Our results showed that coculture with M2-polarized TAMs increased fibroblastic morphology, upregulated mesenchymal markers vimentin and snail at the mRNA and protein levels, and increased proliferation, migration, and metalloproteinase (MMP)2 and MMP9 proteolytic activity in pancreatic cancer cells. Simultaneously, coculture with M2-polarized TAMs decreased the expression of the epithelial marker E-cadherin. Coculture with pancreatic cancer cells increased TLR4 mRNA and protein expression in M2-polarized TAMs. Application of TLR4 siRNA and neutralizing antibodies against TLR4 and IL-10 markedly inhibited E-cadherin reduction and the upregulation of snail and vimentin. Furthermore, activation of TLR4 signaling by lipopolysaccharide profoundly increased the EMT of pancreatic cancer cells. In conclusion, M2-polarized TAMs promoted EMT in pancreatic cancer cells partially through TLR4/IL-10 signaling, suggesting novel therapeutic strategies and enhancing our understanding of M2-polarized TAMs. Pancreatic ductal adenocarcinoma is highly malignant and is resistant to chemo-and radiotherapeutics. 1 Recent evidence suggests the inflammatory environment of the tumor is critical for its progression. 2 Tumor-associated macrophages (TAMs) are derived from circulating monocytes, which are highly abundant within the tumor and provide a key link between inflammation and cancer. 3 TAMs develop a phenotype similar to M2-polarized macrophages and respond to recruitment to the tumor microenvironment. 4 Previous studies have commonly associated elevated numbers of TAMs with tumor progression and poor patient outcome. 5 This association is likely linked to the typical presence of M2-polarized TAMs during cancer invasion, 6 however, the exact mechanisms by which these cells influence the pr...

Hepatocellular carcinoma is accelerated by NASH involving M2 macrophage polarization mediated by hif-1αinduced IL-10

“…33 Importantly, these M2c macrophages have been shown to promote epithelial-mesenchymal transition in pancreatic cancer cells, partially through TLR4/IL-10 signaling pathway. 34 Consistent with this, we found a profound upregulation in EMT markers (vimentin, N-cadherin) in DEN C HF-HC-HSD mouse livers that showed the M2 macrophage phenotype. Based on their IL-10 high IL-12 low profile, the M2 macrophages in our experimental model resemble the M2c subtype.…”

Tumor Budding Correlates With the Protumor Immune Microenvironment and Is an Independent Prognostic Factor for Recurrence of Stage I Lung Adenocarcinoma

“…43,44 In particular, it has been reported that tumorassociated macrophages were found at signifi cant concentrations within the region of tumor budding at the tumor invasive front 22 and that they promoted cancer cell invasiveness via epithelial mesenchymal transition. [23][24][25] Figure We did not perform colocalization studies on the same slide using immunofl uorescent techniques, which was a limitation of our study. However, our prospective investigation of the invasive tumor edge and associated immune cells may help us better understand biologic mechanisms that underlie this association.…”

“…[19][20][21] More importantly, studies have demonstrated that tumor-associated macrophages-especially those of the tumor-promoting M2 phenotype-are frequently found within regions of tumor budding 22 and that they have contributed to induction of cancer cell epithelial mesenchymal transition at the tumor invasive front. [23][24][25] Prognostic signifi cance of tumor budding and its correlation with immune factors have yet to be investigated in early-stage lung adenocarcinoma. We demonstrated that stromal forkhead box P3 (FoxP3)/CD3 lymphocyte risk index, tumoral IL-7 receptor (IL-7R) overexpression, and loss of tumoral IL-12 receptor b 2 (IL-12R b 2) expression were independent prognostic factors of stage I lung adenocarcinoma.…”

A Three-Dimensional Chondrocyte-Macrophage Coculture System to Probe Inflammation in Experimental Osteoarthritis

“…It is also important to note that a number of studies have analyzed the response of human cells to murine RAW 264.7 cells, with results that frequently replicate key features of disease pathology. [85][86][87][88][89][90][91][92][93] Future studies will use primary human macrophages to further develop this coculture system. Eventual testing of new therapeutics, particularly those targeting macrophage activation, using our developed coculture system will also be a key focus of future work.…”