Hepatocellular carcinoma cells remodel the pro-metastatic tumour microenvironment through recruitment and activation of fibroblasts via paracrine Egfl7 signaling.

The tumour microenvironment consists of a complex and dynamic milieu of cancer cells, including tumour-associated stromal cells (leukocytes, fibroblasts, vascular cells, etc.) and their extracellular products. During invasion and metastasis, cancer cells actively remodel the tumour microenvironment and alterations of microenvironment, particularly cancer-associated fibroblasts (CAFs), can promote tumour progression. However, the underlying mechanisms of the CAF formation and their metastasis-promoting functions remain unclear. Primary liver fibroblasts and CAFs were isolated and characterized. CAFs in clinical samples were identified by immunohistochemical staining and the clinical significance of CAFs was also analysed in two independent cohorts. A transwell coculture system was used to confirm the role of HCC cells in CAF recruitment and activation. qRT-PCR, western blotting and ELISA were used to screen paracrine cytokines. The role and mechanism of Egfl7 in CAFs were explored via an in vitro coculture system and an in vivo mouse orthotopic transplantation model. We showed that CAFs in hepatocellular carcinoma (HCC) are characterized by the expression of α-SMA and that HCC cells can recruit liver fibroblasts (LFs) and activate them to promote their transformation into CAFs. High α-SMA expression, indicating high CAF infiltration, was correlated with malignant characteristics. It was also an independent risk factor for HCC survival and could predict a poor prognosis in HCC patients. Then, we demonstrated that EGF-like domain multiple 7 (Egfl7) was preferentially secreted by HCC cells, and exhibited high potential to recruit and activate LFs into the CAF phenotype. The ability of Egfl7 to modulate LFs relies upon increased phosphorylation of FAK and AKT via the receptor ανβ3 integrin. Strikingly, CAFs activated by paracrine Egfl7 could further remodel the tumour microenvironment by depositing fibrils and collagen and in turn facilitate HCC cell proliferation, invasion and metastasis. Our data highlighted a novel role of Egfl7 in remodelling the tumour microenvironment: it recruits LFs and activates them to promote their transformation into CAFs via the ανβ3 integrin signaling pathway, which further promotes HCC progression and contributes to poor clinical outcomes in HCC patients. Video Abstract.

Sun B ，Lei X ，Cao M ，Li Y ，Yang LY ... -  《Cell Communication and Signaling》

Resolvin D1 prevents epithelial-mesenchymal transition and reduces the stemness features of hepatocellular carcinoma by inhibiting paracrine of cancer-associated fibroblast-derived COMP.

Sun L ，Wang Y ，Wang L ，Yao B ，Chen T ，Li Q ，Liu Z ，Liu R ，Niu Y ，Song T ，Liu Q ，Tu K ... -  《JOURNAL OF EXPERIMENTAL & CLINICAL CANCER RESEARCH》

Cancer-associated fibroblasts promote the stemness of CD24(+) liver cells via paracrine signaling.

Li Y ，Wang R ，Xiong S ，Wang X ，Zhao Z ，Bai S ，Wang Y ，Zhao Y ，Cheng B ... -  《-》

Emerging Role of Cancer-Associated Fibroblasts in Progression and Treatment of Hepatocellular Carcinoma.

Akkız H 《INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES》

IL-6/STAT3 axis initiated CAFs via up-regulating TIMP-1 which was attenuated by acetylation of STAT3 induced by PCAF in HCC microenvironment.

Aberrant tumor microenvironment is involved closely in tumor initiation and progression, in which cancer associated fibroblasts (CAFs) play a pivotal role. Both IL-6/STAT3 signaling and TIMP-1 have been found to modulate the crosstalk between tumor cells and CAFs in tumor microenvironment, however, the underlying mechanism remains unclear. Here, we showed that IL-6/STAT3 signaling was activated aberrantly in HCC tissues and correlated with poor post-surgical outcome. The in vitro experiments confirmed that activation of IL-6/STAT3 pathway enhanced TIMP-1 expression directly via phosphorylated STATs (p-STAT3)-binding with TIMP-1 promoter in Huh7 cells. Furthermore, activation of IL-6/STAT3 pathway in HCC cells was shown to induce the transformation from normal liver fibroblasts (LFs) to CAFs via up-regulating TIMP-1 expression. Co-culture with CAFs promoted the growth of Huh7 cells both in vitro and in vivo. Finally, by co-Immunoprecipitation and immunoblotting assessments, PCAF, a well-known acetyltransferase, was revealed to acetylate cytoplasmic STAT3 protein directly and regulate TIMP-1 expression negatively in Huh7 cells. In summary, this investigation indicated that there was a positive IL-6/TIMP-1 feedback loop controlling the crosstalk between HCC cells and its neighbouring fibroblasts. The data here also identified that PCAF repressed TIMP-1 expression via acetylation of STAT3. In conclusion, this investigation demonstrated that CAFs promoted HCC growth via IL-6/STAT3/AKT pathway and TIMP-1 over-expression driven by IL-6/STAT3 pathway in HCC cells brought in more CAFs through activating LFs. Finally, PCAF could block this positive feedback by acetylating STAT3 in HCC cells.

Zheng X ，Xu M ，Yao B ，Wang C ，Jia Y ，Liu Q ... -  《-》