CXCR4/TGF-β1 mediated hepatic stellate cells differentiation into carcinoma-associated fibroblasts and promoted liver metastasis of colon cancer

Abstract

Background: Liver metastasis of colon cancer is strongly affected by the tumor microenvironment (TME), with interactions between tumor cells and cancer-associated fibroblasts (CAFs) in particular. TGFβ is well known for its ability to mediate the CAF phenotype, and CXCR4 expression is closely correlated to poor prognosis in CRC. The relationship between these two signaling pathways remains to be delineated in liver metastasis of colon cancer. Methods: Immunohistochemistry was employed to investigate CXCR4 expression in 45 human specimens of primary colorectal cancer (CRC) and liver metastasis. The functions of SDF-1 released by hepatic stellate cells (HSCs) on CXCR4 and TGF-β1 in CRC cells were investigated in vitro. The effects of CRC on HSCs differentiation into CAFs were confirmed using co-culture technology and expression analysis of CAFs markers by qPCR, western blot and immunofluorescence. The involvement of CXCR4 and TGF-β1 was verified with addition of CXCR4 inhibitor AMD3100 and TGF-β1 inhibitor cyclophosphamide (Cy) both in vitro and in vivo. Results: There were more CXCR4-positive cells at the liver metastatic tissues compared to the primary sites. CRC cells activated and transformed HSCs to CAFs after co-cultivating with HSCs. Activated HSCs stimulated TGF-β1 secretion from CRC cells after co-culture with CRC cells in vitro. Moreover, the expression of CAFs markers was increasing in the activated HSCs. In a mouse hepatic metastasis model, treated with AMD3100 or Cy blocked the metastatic potential of HCT116 cells and the hepatic CAFs differentiation. Conclusions: These results indicated that CXCR4/TGF-β1 axis plays an important role in CRC liver metastasis through mediating HSCs differentiation into CAFs, providing preclinical evidences that blockade of the axis might be beneficial for anti-metastasis therapy in CRC.

TGF‐β signaling in liver metastasis

“…28,29,48,49 Through tumor-stroma crosstalk, tumor cells are able to recruit and activate surrounding liver microenvironmental cells into myofibroblasts. 10,28,32,48,50,51 TGF-β signaling is key in this crosstalk. Activation of HSCs into aHSCs leads to secretion of cytokines, including platelet derived growth factor (PDGF), HGF, TGF-β, stromal derived factor (SDF), ECM proteins fibronectin and collagen, and matrix metalloproteases (MMPs).…”

“…In the liver, various cell types are a source of TGF-β, including tumor cells, myofibroblasts, and local immune cells. 14,50,60,90 Below, we will describe the current knowledge of TGF-β during the different phases of hepatic colonization. A schematic overview of different functions of TGF-β during liver metastasis is shown in Figure 3.…”

“…For example, SDF-1 secretion by aHSCs was found to bind C-X-C chemokine receptor type 4 (CXCR4), promoting TGF-β signaling and secretion by CRC tumor cells. 50 Blocking CXCR4 or TGF-β in vivo decreased the metastatic potential of CRC cell lines and reduced HSC activation. 50 Calon and colleagues tested the effect of TGF-β secretion by TGF-β-deficient CRC cells, inducing stromal TGF-β signaling, during liver metastasis formation in mice.…”

Identifying cancer-associated fibroblasts as emerging targets for hepatocellular carcinoma

“…Tan et al . previously reported that human HSC cell line LX2 could be converted into α-SMA(+)/FSP1(+) CAFs with exposure to tumor-derived TGF-β in vitro [ 38 ]. A recent transgenic model also suggested that the hepatocyte-derived platelet derive growth factor-C (PDGF-C) transformed HSCs into myofibroblast-like cells, which in turn produced cytokines to promote the development of HCC [ 39 ].…”

Inflammation in Primary and Metastatic Liver Tumorigenesis–Under the Influence of Alcohol and High-Fat Diets

“…Unsurprisingly, HSCs are also present within CRC liver metastatic nodules, with the activated myofibroblast phenotype also associated with a metastasis-supportive niche [186,187]. Other resident cells within the hepatic microenvironment provide a source of pro-fibrogenic cytokines, in particular TGF-β, VEGF, PDGF and connective tissue growth factor (CTGF) [46], and activation of HSCs can also be directly induced by CRC cells [188]. Secretion of ECM remodeling factors from myofibroblasts such as matrix metalloproteinases (MMPs) generates a reactive stroma, permissive to tumor cell seeding and proliferation and suitable for neovascularization and angiogenesis [153,189].…”