A Smad3-PTEN regulatory loop controls proliferation and apoptotic responses to TGF-β in mouse endometrium

Abstract

The TGF-β/Smad and the PI3K/AKT signaling pathways are important regulators of proliferation and apoptosis, and their alterations lead to cancer development. TGF-β acts as a tumor suppressor in premalignant cells, but it is a tumor promoter for cancerous cells. Such dichotomous actions are dictated by different cellular contexts. Here, we have unveiled a PTEN-Smad3 regulatory loop that provides a new insight in the complex cross talk between TGF-β/Smad and PI3K/AKT signaling pathways. We demonstrate that TGF-β triggers apoptosis of wild-type polarized endometrial epithelial cells by a Smad3-dependent activation of PTEN transcription, which results in the inhibition of PI3K/AKT signaling pathway. We show that specific Smad3 knockdown or knockout reduces basal and TGF-β-induced PTEN expression in endometrial cells, resulting in a blockade of TGF-β-induced apoptosis and an enhancement of cell proliferation. Likewise Smad3 deletion, PTEN knockout prevents TGF-β-induced apoptosis and increases cell proliferation by increasing PI3K/AKT/mTOR signaling. In summary, our results demonstrate that Smad3-PTEN signaling axis determine cellular responses to TGF-β.

Supported by grants SAF2016-80157-R from Ministerio de Economía y Competitividad, PI13/00263 and PI13/01701 from Fondo de Investigaciones Sanitarias del Instituto de Salud Carlos III cofinanciado por Fondo Europeo de Desarrollo Regional (FEDER) (“Una manera de hacer Europa”), Red Temática de investigación en Cáncer RD12/0036/0013 and Red de Oncología (CIBERONC). Grups consolidats de la Generalitat de Catalunya (2009SGR794), Fundació La Marató de TV3, Grupos estables AECC, Catalunya contra el cáncer and programa de intensificación de la investigación, Instituto Carlos III.