Interaction of FGF9 with FGFR3‐IIIb/IIIc, a putative driver of growth and aggressive behaviour of hepatocellular carcinoma

Abstract

Background & Aims Recently, overexpression of the fibroblast growth factor receptor 3 (FGFR3) splice variants FGFR3‐IIIb and FGFR3‐IIIc was found in ~50% of hepatocellular carcinoma (HCC). Here, we aim to identify FGFR3‐IIIb/IIIc ligands, which drive the progression of HCC. Methods FACS, MTT assay and/or growth curves served to identify the FGFR3‐IIIb/IIIc ligand being most effective to induce growth of hepatoma/hepatocarcinoma cell lines, established from human HCC. The most potent FGF was characterized regarding the expression levels in epithelial and stromal cells of liver and HCC and impact on neoangiogenesis, clonogenicity and invasive growth of hepatoma/hepatocarcinoma cells. Results Among all FGFR3‐IIIb/IIIc ligands tested, FGF9 was the most potent growth factor for hepatoma/hepatocarcinoma cells. Replication and/or sprouting of blood/lymphendothelial cells was stimulated as well. FGF9 occurred mainly in stromal cells of unaltered liver but in epithelial cells of HCC. Every fifth HCC exhibited overexpressed FGF9 and frequent co‐upregulation of FGFR3‐IIIb/IIIc. In hepatoma/hepatocarcinoma cells FGF9 enhanced the capability for clonogenicity and disintegration of the blood and lymphatic endothelium, being most pronounced in cells overexpressing FGFR3‐IIIb or FGFR3‐IIIc, respectively. Any of the FGF9 effects in hepatoma/hepatocarcinoma cells was blocked completely by applying the FGFR1‐3‐specific tyrosine kinase inhibitor BGJ398 or siFGFR3, while siFGFR1/2/4 were mostly ineffective. Conclusions FGF9 acts via FGFR3‐IIIb/IIIc to enhance growth and aggressiveness of HCC cells. Accordingly, blockade of the FGF9‐FGFR3‐IIIb/IIIc axis may be an efficient therapeutic option for HCC patients.

Role of fibroblast growth factor signalling in hepatic fibrosis

“…Regarding its potential as therapeutic target, it is of particular interest that several studies have shown that FGF9 plays a detrimental role in HCC progression. [102][103][104]…”

“…9 In contrast, freshly isolated HSC do not express FGFR3B but FGFR3C, 92 and FGFR3C is upregulated in TGFβ treated LX2 cells. 132 Although FGFR3 plays an important role in HCC development and progression 9,103,137 and FGFR3 expression is elevated in human cirrhotic livers, 132 the functional role of FGFR3 and its isoforms has not yet been investigated in the context of hepatic fibrosis. A recent study revealed that FGF9-activated FGFR3 promoted fibrosis in systemic sclerosis through activation of profibrotic signalling pathways.…”

FGF/FGFR Signaling in Hepatocellular Carcinoma: From Carcinogenesis to Recent Therapeutic Intervention

“…FGF9 expression is often co-upregulated with FGFR3 IIIb/IIIc expression in HCC patients. Furthermore, FGF9 is the most dominant ligand for FGFR3 IIIb/IIIc in HCC [ 32 ]. FGF9 is secreted mainly by HSCs in normal and cirrhotic livers and acts by the paracrine mechanism to stimulate tumor cells.…”

“…However, both findings emphasize the tumorigenic role of FGF9 in HCC. FGF9 exerts its tumorigenic role by specifically binding to FGFR3, facilitating the proliferation and migration of HCC cell lines and promoting new blood and lymphatic capillary formation [ 32 ]. Moreover, FGF9 is involved in sorafenib resistance, indicating that FGF9 may be a promising target of HCC.…”

“…FGF9 binds to FGFR3 IIIb or IIIc and enhances cell line migration by inducing gaps in monolayers of blood or lymphatic endothelium, similar to tumor invasion into the circulation. Furthermore, treatment with recombinant FGF9 significantly enhanced HCC migration [ 32 ]. Moreover, FGF9 can regulate the HSC cell lines’ migration by creating an inflammatory microenvironment in NAFLD mice, contributing to liver fibrosis and HCC development [ 35 ].…”