Snail1 suppresses TGF-beta-induced apoptosis and is sufficient to trigger EMT in hepatocytes.

Although TGF-ß suppresses early stages of tumour development, it later contributes to tumour progression when cells become resistant to its suppressive effects. In addition to circumventing TGF-ß-induced growth arrest and apoptosis, malignant tumour cells become capable of undergoing epithelial-to-mesenchymal transition (EMT), favouring invasion and metastasis. Therefore, defining the mechanisms that allow cancer cells to escape from the suppressive effects of TGF-ß is fundamental to understand tumour progression and to design specific therapies. Here, we have examined the role of Snail1 as a suppressor of TGF-ß-induced apoptosis in murine non-transformed hepatocytes, rat and human hepatocarcinoma cell lines and transgenic mice. We show that Snail1 confers resistance to TGF-ß-induced cell death and that it is sufficient to induce EMT in adult hepatocytes, cells otherwise refractory to this transition upon exposure to TGF-ß. Furthermore, we show that Snail1 silencing prevents EMT and restores the cell death response induced by TGF-ß. As Snail1 is a known target of TGF-ß signalling, our data indicate that Snail1 might transduce the tumour-promoting effects of TGF-ß, namely the EMT concomitant with the resistance to cell death.