19 Given its implication as a tumor suppressor in different human cancers, we analyzed the role of mig-6 in human liver cancer cell lines. Importantly, the EGFR and its ligands have been described to be frequently expressed in human liver cancer, thereby contributing to liver tumor development.25–27 In this study, we show that mig-6 is efficiently induced upon EGF stimulation and acts as an endogenous inhibitor of EGFR activity in human liver cancer cell lines. Mig-6 is able to bind to the activated EGFR, thereby most likely regulating receptor activation and stability. Venetoclax manufacturer However, it is important to note that mig-6 could not be induced in primary

hepatocytes upon EGF stimulation (Fig. 1B). This may be because mig-6 levels are already relatively high in unstimulated cells, which may be caused by the activation process that hepatocytes undergo during isolation and culture. Nevertheless, we were able to show that loss of mig-6 in primary hepatocytes leads to increased activation of EGFR signaling (Fig. 1B), suggesting that mig-6 contributes to EGFR regulation. Unexpectedly, we could show that mig-6 is a negative regulator of EGF-induced cell migration in HepG2 cells. Suppression of mig-6 by a specific siRNA led to a marked increase in EGFR-AKT signaling. As a consequence,

mig-6 knockdown cells display increased cell migration toward EGF. This observation was surprising, U0126 because mig-6 was primarily implicated Buspirone HCl in the suppression of EGF-induced cell

proliferation rather than migration. A previous study, however, showed that mig-6 is a negative regulator of HGF/MET-induced cell migration in neurons and especially in cells of hepatic origin,13 suggesting that mig-6 might be a negative regulator of growth factor–induced cell migration in liver cells. In primary HCCs, mig-6 was found to be down-regulated in a significant number of cases and that correlates with increased EGFR expression. These data suggest that loss of mig-6 in primary human liver tumors might be sufficient to generate increased EGFR signaling, which may lead to tumor formation and progression. Interestingly, mig-6 knockout mice are susceptible to Di-ethyl nitrosamine–induced liver tumor formation, further suggesting that mig-6 is a suppressor of hepatocarcinogenesis (data not shown). It will be the aim of future studies to investigate the exact role and the regulation of mig-6 in HCCs and whether it can serve as a possible marker for EGFR-dependent liver carcinogenesis. In conclusion, we have demonstrated that mig-6 is a negative regulator of EGFR signaling in mouse hepatocytes and have identified mig-6 as a suppressor of EGFR signaling in human liver cancer cell lines. We thank Rüdiger Klein and Sonia Paixao from the Max-Planck Institute of Neurobiology, Martinsried, for providing reagents and for their generous help with hepatocyte isolation. Additional Supporting Information may be found in the online version of this article.