Dissecting the effect of targeting the epidermal growth factor receptor on TGF-β-induced-apoptosis in human hepatocellular carcinoma cells.

Transforming growth factor-beta (TGF-β) induces apoptosis in hepatocytes, a process that is inhibited by the epidermal growth factor receptor (EGFR) pathway. The aim of this work was to ablate EGFR in hepatocellular carcinoma (HCC) cells to understand its role in impairing TGF-β-induced cell death. Response to TGF-β in terms of apoptosis was analyzed in different HCC cell lines and the effect of canceling EGFR expression was evaluated. TGF-β induces apoptosis in some HCC cells (such as Hep3B, PLC/PRF/5, Huh7, or SNU449), but it also mediates survival signals, coincident with the up-regulation of EGFR ligands. Inhibition of the EGFR, either by targeted knock-down with specific siRNA or by pharmacological inhibition, significantly enhances apoptotic response. TGF-β treatment in EGFR targeted knock-down cells correlates with higher levels of the NADPH oxidase NOX4 and changes in the expression profile of BCL-2 and IAP families. However, other HCC cells, such as HepG2, which show over activation of the Ras/ERKs pathway, SK-Hep1, with an endothelial phenotype, or SNU398, where the TGF-β-Smad signaling is altered, show apoptosis resistance that is not restored through EGFR blockade. The inhibition of EGFR in HCC may enhance TGF-β-induced pro-apoptotic signaling. However, this effect may only concern those tumors with an epithelial phenotype which do not bear alterations in TGF-β signaling nor exhibit an over-activation of the survival pathways downstream of the EGFR.

Caja L ，Sancho P ，Bertran E ，Fabregat I ... -  《-》

Upregulation of the NADPH oxidase NOX4 by TGF-beta in hepatocytes is required for its pro-apoptotic activity.

Carmona-Cuenca I ，Roncero C ，Sancho P ，Caja L ，Fausto N ，Fernández M ，Fabregat I ... -  《JOURNAL OF HEPATOLOGY》

Overactivation of the MEK/ERK pathway in liver tumor cells confers resistance to TGF-{beta}-induced cell death through impairing up-regulation of the NADPH oxidase NOX4.

Caja L ，Sancho P ，Bertran E ，Iglesias-Serret D ，Gil J ，Fabregat I ... -  《-》

Suppression of TG-interacting factor sensitizes arsenic trioxide-induced apoptosis in human hepatocellular carcinoma cells.

Liu ZM ，Tseng JT ，Hong DY ，Huang HS ... -  《-》

The NADPH oxidase inhibitor VAS2870 impairs cell growth and enhances TGF-β-induced apoptosis of liver tumor cells.

Liver tumor cells show several molecular alterations which favor pro-survival signaling. Among those, we have proposed the NADPH oxidase NOX1 as a prosurvival signal for liver tumor cells. On the one side, we have described that FaO rat hepatoma cells show NOX1-dependent partial resistance to apoptosis induced by Transforming Growth Factor beta (TGF-β). On the other side, we have shown that FaO cells, as well as different human hepatocellular carcinoma (HCC) cell lines, are able to proliferate in the absence of serum through the activation of a NOX1-dependent signaling pathway. The aim of this work was to analyze the effects of NADPH oxidase pharmacological inhibition in liver tumor cells using the inhibitor VAS2870. This compound inhibits dose-dependently autocrine increase of cell number in FaO rat hepatoma cells, and almost completely blocked ROS production and thymidine incorporation when used at 25μM. Such inhibitory effect on autocrine growth is coincident with lower mRNA levels of EGFR (Epidermal Growth Factor Receptor) and its ligand TGF-α (Transforming Growth Factor-alpha), and decreased phosphorylation of the EGFR itself and other downstream targets, such as SRC or AKT. Moreover, NADPH oxidase pharmacological inhibition also effectively attenuates serum-dependent growth and phosphorylation of AKT and ERK. Importantly, these inhibitory effects on either autocrine or serum-dependent cell growth are observed in several human HCC cell lines. Finally, we have observed that VAS2870 is also effective in enhancing apoptosis induced by a physiological stimulus, such as TGF-β. In summary, NADPH oxidase pharmacological inhibition could be considered a promising tool in the treatment of liver cancer.

Sancho P ，Fabregat I 《-》