12 We found that FGF17 and FGF18 stimulate replicative DNA synthesis in MF cells. A similar effect was evident on the DNA replication of endothelial cells that were isolated from human tumor-bearing livers (Fig. 6). Furthermore, all three FGFs induced tube formation of endothelial cells, which is a further necessary step in

neoangiogenesis. This suggests that FGF8 subfamily members favor the formation of new blood vessels in HCC directly and indirectly via the multiplication of vEGF-producing MFs. Here we show for the first time that FGF8, FGF17, and FGF18 have more or less equal potency in enhancing neoangiogenesis and the aggressive behavior of malignant hepatocytes. Accordingly, at least one of these FGFs was up-regulated in the majority of the investigated HCC cases. This implies that the FGF8 subfamily members are crucial components in autocrine and paracrine loops supporting the autonomous growth of advanced stages Selleckchem Deforolimus of hepatocarcinogenesis, as outlined in the following. In this study, we found pronounced overexpression of FGF18 in a subset of human HCC cases. The human FGF18 gene harbors T cell factor/lymphoid enhancer-binding factor binding sites in the promoter region. Accordingly, FGF18 transcription is under the control of the β-catenin T cell factor/lymphoid enhancer-binding

factor complex, as shown recently by our group and others.16, 27 In human HCC, the wnt/wingless signaling http://www.selleckchem.com/products/i-bet-762.html cascade often is activated by mutations in AXIN1, AXIN2, or the gene coding for β-catenin [catenin (cadherin-associated protein) β1] (CTNNB1) and/or through epigenetic silencing of wnt antagonists, such as the secreted frizzled-related protein.9, 10, 13 These disturbances in the wnt signaling cascade may contribute to the observed up-regulation of FGF18 in human HCC. Here we found that the withdrawal of serum or oxygen is a potent inducer of all FGF8 subfamily members in HCC-1.2, HepG2, and Hep3B cells. These regimens simulate the conditions in rapidly expanding HCC with an inadequate blood supply. Generally, such conditions alter signaling cascades and gene expression selleck patterns of the affected cells

and lead to increased neoangiogenesis and glycolysis and decreased mitochondrial respiration. In our experiments, serum deprivation clearly elevated the phosphorylation of GSK3β at serine 9 in the hepatocarcinoma cells, and this may lead to reduced phosphorylation and degradation of β-catenin and increase the probability of β-catenin entering the nucleus and activating the transcription of FGF18. The molecular mechanisms underlying the induction of FGF8 and FGF17 by serum withdrawal are still unclear. In comparison with serum withdrawal, hypoxia is a more specific stimulus transduced by members of several transcription factor families, including the hypoxia inducible factor (HIF), aryl hydrocarbon receptor (AHR), E twenty-six (ETS), and metal-responsive transcription factor (MTF) families.