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Axl activates autocrine transforming growth factor-? signaling in hepatocellular carcinoma.

ABSTRACT: In hepatocellular carcinoma (HCC), intrahepatic metastasis frequently correlates with epithelial to mesenchymal transition (EMT) of malignant hepatocytes. Several mechanisms have been identified to be essentially involved in hepatocellular EMT, among them transforming growth factor (TGF)-? signaling. Here we show the up-regulation and activation of the receptor tyrosine kinase Axl in EMT-transformed hepatoma cells. Knockdown of Axl expression resulted in abrogation of invasive and transendothelial migratory abilities of mesenchymal HCC cells in vitro and Axl overexpression-induced metastatic colonization of epithelial hepatoma cells in vivo. Importantly, Axl knockdown severely impaired resistance to TGF-?-mediated growth inhibition. Analysis of the Axl interactome revealed binding of Axl to 14-3-3?, which is essentially required for Axl-mediated cell invasion, transendothelial migration, and resistance against TGF-?. Axl/14-3-3? signaling caused phosphorylation of Smad3 linker region (Smad3L) at Ser213, resulting in the up-regulation of tumor-progressive TGF-? target genes such as PAI1, MMP9, and Snail as well as augmented TGF-?1 secretion in mesenchymal HCC cells. Accordingly, high Axl expression in HCC patient samples correlated with elevated vessel invasion of HCC cells, higher risk of tumor recurrence after liver transplantation, strong phosphorylation of Smad3L, and lower survival. In addition, elevated expression of both Axl and 14-3-3? showed strongly reduced survival of HCC patients.Our data suggest that Axl/14-3-3? signaling is central for TGF-?-mediated HCC progression and a promising target for HCC therapy.

SUBMITTER: Reichl P

PROVIDER: S-EPMC4450343 | biostudies-literature | 2015 Mar

REPOSITORIES: biostudies-literature

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Axl activates autocrine transforming growth factor-β signaling in hepatocellular carcinoma.

Reichl Patrick P Dengler Mirko M van Zijl Franziska F Huber Heidemarie H Führlinger Gerhard G Reichel Christian C Sieghart Wolfgang W Peck-Radosavljevic Markus M Grubinger Markus M Mikulits Wolfgang W

Hepatology (Baltimore, Md.) 20150128 3

<h4>Unlabelled</h4>In hepatocellular carcinoma (HCC), intrahepatic metastasis frequently correlates with epithelial to mesenchymal transition (EMT) of malignant hepatocytes. Several mechanisms have been identified to be essentially involved in hepatocellular EMT, among them transforming growth factor (TGF)-β signaling. Here we show the up-regulation and activation of the receptor tyrosine kinase Axl in EMT-transformed hepatoma cells. Knockdown of Axl expression resulted in abrogation of invasive ...[more]

PMID: 25251599

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Project description:BACKGROUND: Diffuse-type gastric carcinoma is a cancer with poor prognosis that has high levels of transforming growth factor beta (TGF-beta) expression and thick stromal fibrosis. However, the association of TGF-beta signaling with diffuse-type gastric carcinoma has not been investigated in detail. METHODS: We used a lentiviral infection system to express a dominant-negative TGF-beta type II receptor (dnTbetaRII) or green fluorescent protein (GFP) as a control in the diffuse-type gastric carcinoma cell lines, OCUM-2MLN and OCUM-12. These infected cells and the corresponding parental control cells were subcutaneously or orthotopically injected into nude mice. Angiogenesis was inhibited by infecting cells with a lentivirus carrying the gene for angiogenic inhibitor thrombospondin-1 or by injecting mice intraperitoneally with the small-molecule angiogenic inhibitor sorafenib or with anti-vascular endothelial growth factor (VEGF) neutralizing antibody (six or eight mice per group). Expression of phospho-Smad2 and thrombospondin-1 was investigated immunologically in human gastric carcinoma tissues from 102 patients. All statistical tests were two-sided. RESULTS: Expression of dnTbetaRII into OCUM-2MLN cells did not affect their proliferation in vitro, but it accelerated the growth of subcutaneously or orthotopically transplanted tumors in vivo (eg, for mean volume of subcutaneous tumors on day 10 relative to that on day 0: dnTbetaRII tumors = 3.49 and GFP tumors = 2.46, difference = 1.02, 95% confidence interval [CI] = 0.21 to 1.84; P = .003). The tumors expressing dnTbetaRII had higher levels of angiogenesis than those expressing GFP because of decreased thrombospondin-1 production. Similar results were obtained with OCUM-12 cells. Expression of thrombospondin-1 in the dnTbetaRII tumor or treatment with sorafenib or anti-VEGF antibody reduced tumor growth, whereas knockdown of thrombospondin-1 expression resulted in more accelerated growth of OCUM-2MLN tumors than of GFP tumors (eg, mean tumor volumes on day 14 relative to those on day 0: thrombospondin-1-knockdown tumors = 4.91 and GFP tumors = 3.79, difference = 1.12, 95% CI = 0.80 to 1.44; P < .001). Positive association between phosphorylated Smad2 and thrombospondin-1 immunostaining was observed in human gastric carcinoma tissues. CONCLUSIONS: Disruption of TGF-beta signaling in diffuse-type gastric carcinoma models appeared to accelerate tumor growth, apparently through increased tumor angiogenesis that was induced by decreased expression of thrombospondin-1.

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Dataset Information

Axl activates autocrine transforming growth factor-? signaling in hepatocellular carcinoma.

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Axl activates autocrine transforming growth factor-β signaling in hepatocellular carcinoma.

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