Dataset Information

SIRT4 silencing in tumor-associated macrophages promotes HCC development via PPAR? signalling-mediated alternative activation of macrophages.

ABSTRACT:

Background

The activation of tumour-associated macrophages (TAMs) contributes to the progression of hepatocellular carcinoma (HCC). SIRT4 acts as a tumour suppressor of tumour growth by regulating cell metabolism, inflammation, and anti-tumourigenesis. However, the involvement of SIRT4 in the activation of TAMs is unknown. Based on previous findings, the expression of SIRT4 in distinct groups of TAMs as well as the effect of SIRT4 silencing on macrophage polarization was investigated.

Methods

The expression of SIRT4 in HCC tissues and peritumour tissues was tested by qRT-PCR, western blotting and histological analysis. A Kaplan-Meier survival curve was generated based on the expression of SIRT4 in the HCC samples. Next, immunofluorescence staining was used to evaluate distinct groups of TAMs in human HCC samples, and the expression of SIRT4 in M1 and M2 TAMs was examined by flow cytometry. A homograft mouse model was used to assess the effect of SIRT4 silencing in TAMs on the development of HCC cells.

Results

SIRT4 was significantly downregulated in HCC tumour tissues, and the expression of SIRT4 in peritumour tissues was positively associated with survival in patients. We further found that downregulation of SIRT4 was associated with increased macrophage infiltration and a high ratio of M2/M1 macrophages in HCC peritumour tissues. Using gene interference, we found that SIRT4 silencing in TAMs significantly modulated the alternative activation of macrophages and promoted in vitro and in vivo HCC cell growth. Mechanistically, we revealed that HCM restricted the expression of SIRT4 in macrophages and promoted alternative activation of macrophages via the FAO-PPAR?-STAT3 axis. Furthermore, we also revealed that elevated MCP-1 expression induced by SIRT4 downregulation was responsible for increased TAM infiltration in peritumour tissues.

Conclusions

Overall, our results demonstrate that downregulation of SIRT4 in TAMs modulates the alternative activation of macrophages and promotes HCC development via the FAO-PPAR?-STAT3 axis. These results could provide a new therapeutic target for the treatment of HCC.

SUBMITTER: Li Z

PROVIDER: S-EPMC6862746 | biostudies-literature | 2019 Nov

REPOSITORIES: biostudies-literature

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Publications

SIRT4 silencing in tumor-associated macrophages promotes HCC development via PPARδ signalling-mediated alternative activation of macrophages.

Li Zhi Z Li He H Zhao Zhi-Bo ZB Zhu Wei W Feng Pan-Pan PP Zhu Xi-Wen XW Gong Jian-Ping JP

Journal of experimental & clinical cancer research : CR 20191119 1

<h4>Background</h4>The activation of tumour-associated macrophages (TAMs) contributes to the progression of hepatocellular carcinoma (HCC). SIRT4 acts as a tumour suppressor of tumour growth by regulating cell metabolism, inflammation, and anti-tumourigenesis. However, the involvement of SIRT4 in the activation of TAMs is unknown. Based on previous findings, the expression of SIRT4 in distinct groups of TAMs as well as the effect of SIRT4 silencing on macrophage polarization was investigated.<h4 ...[more]

PMID: 31744516

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Project description:BACKGROUND:Gut microbiota and the tumor microenvironment are thought to be critical factors that modulate the processes of liver diseases, including hepatocellular carcinoma (HCC). Interleukin-25 (IL-25) promotes type 2 immunity via alternative activation of macrophages, and is closely associated with inflammation-related diseases, even malignancies. However, it is not clear which role IL-25 plays in the development of HCC, and whether gut microbiota are involved. METHODS:IL-25 was detected by ELISA, Western blotting (WB), and immunohistochemistry. Chemokines were measured by RT-qPCR and WB. After co-culture with IL-25-stimulated macrophages, the cell growth, migration, invasion and EMT marker of HCC cell lines (MHCC97L and HepG2) were evaluated by Brdu proliferation, Transwell assays and WB. An antibody neutralization assay of chemokine CXCL10 was performed to confirm its role in HCC development. Furthermore, the effects of IL-25 in HCC were investigated in vivo. Dysbiosis of gut microflora was induced by antibiotics (vancomycin, cefoperazone or combination of ampicillin, neomycin, metronidazole, and vancomycin). We used feces suspension to treat colonic epithelial NCM460 cells, and detected IL-25 and tuft cell marker DCLK1 using WB and immunofluorescence staining. RESULTS:We found that the level of IL-25 was significantly elevated in HCC patients, and was negatively correlated with survival rate after hepatectomy. However, IL-25 did not directly promote the development of HCC cells. Then, we observed the significant positive correlation between IL-25 level and M2 percentage (CD206/CD68) in HCC tumors. In vitro and in vivo, IL-25 induced alternative activation of macrophages promoted HCC cell migration, invasion and tumorigenesis, increased the expression of vimentin, Snail and phospho-ERK, and decreased the expression of E-cadherin in HCC cells. After IL-25 treatment, chemokine CXCL10 was increased in macrophages. Neutralizing CXCL10 in macrophage-conditioned medium reversed the IL-25-mediated effect on HCC cells. Vancomycin-induced dysbiosis promoted the growth of orthotopic HCC homograft. Surprisedly, we found the hyperplasia of colonic epithelial tuft cells, from which more IL-25 was secreted . CONCLUSIONS:IL-25 promotes the progression of HCC through inducing alternative activation and CXCL10 secretion of macrophages in tumor microenvironment, and IL-25 secretion may partly result from hyperplastic epithelial tuft cells in colon, induced by gut microbiota dysbiosis.