Blocking transforming growth factor–beta up-regulates E-cadherin and reduces migration and invasion of hepatocellular carcinoma cells

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Abstract
Hepatocellular carcinoma (HCC) treatment is challenging because the mechanisms underlying tumor progression are still largely unknown. Transforming growth factor (TGF)–β1 is considered a crucial molecule in HCC tumorigenesis because increased levels of patients' serum and urine are associated with disease progression. The aim of the present study was to investigate the inhibition of TGF-β signaling and its impact on HCC progression. Human HCC cell lines were treated with a TGF-β receptor kinase inhibitor (LY2109761) whose selectivity was determined in a kinase assay. Exogenous TGF-β1 phosphorylates the TGF-β receptor, consequently activating Smad-2, whereas the drug selectively blocks this effect and dephosphorylates autocrine p-Smad-2 at concentrations ranging from 0.001 to 0.1 μM. A cytotoxic effect documented by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT), trypan blue, and propidium iodide staining assays was observed at 10μM, whereas the drug inhibits ( P < 0.001) the migration of HCC cells on fibronectin, laminin-5, and vitronectin and invasion through Matrigel ( P < 0.001) at concentrations up to 0.1 μM. LY2109761 up-regulates ( P < 0.001) E-cadherin mRNA and protein levels. This increase was localized at the cellular membrane where E-cadherin mediates anchorage that is cell–cell dependent. Consistently, a functional monoclonal antibody that inhibits E-cadherin–dependent cell–cell contact restores the migratory and invasive activity. Finally, nonmetastatic HCC tissues from 7 patients were cultured with TGF-β1 in the presence or absence of LY2109761. E-cadherin expression was reduced by TGF-β1 and was significantly ( P < 0.0001) increased by LY2109761 treatment, measured by quantitative real-time PCR on microdissected tissues and by immunohistochemistry on serial sections. In 72 patients, E-cadherin tissue expression was more weakly expressed in metastatic than in nonmetastatic HCC ( P < 0.0001). Conclusion: LY2109761 blocks migration and invasion of HCC cells by up-regulating E-cadherin, suggesting that there could be a mechanistic use for this molecule in clinical trials.
Funding Information
  • Italian association for cancer research (AIRC)
  • Eli Lilly Co. (GNN 110/2007)