Contents lists available at ScienceDirect International Journal of Biochemistry and Cell Biology journal homepage: www.elsevier.com/locate/biocel Metformin inhibits β-catenin phosphorylation on Ser-552 through an AMPK/PI3K/Akt pathway in colorectal cancer cells Gastón Amable a,b , Eduardo Martínez-León a,b , María Elisa Picco a,b , Nicolas Di Siervi a,c , Carlos Davio a,c,d , Enrique Rozengurt e , Osvaldo Rey a,b, ⁎ a Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad de Buenos Aires, Argentina b Instituto de Inmunología, Genética y Metabolismo, Facultad de Farmacia y Bioquímica, Hospital de Clínicas "José de San Martín", Caba, 1120, Argentina c Instituto de Investigaciones Farmacológicas, Facultad de Farmacia y Bioquímica, Argentina d Departamento de Farmacología, Caba, 1113, Argentina e Unit of Signal Transduction and Gastrointestinal Cancer, Division of Digestive Diseases, Department of Medicine, CURE: Digestive Diseases Research Center, Molecular Biology Institute and Jonsson Comprehensive Cancer Center, David Geffen School of Medicine, University of California at Los Angeles, CA, 90095-1786, USA ARTICLE INFO Keywords: Metformin β-Catenin Colorectal cancer AMPK PI3K/Akt ABSTRACT Several epidemiologic studies have revealed strong inverse associations between metformin use and risk of colorectal cancer development. Nevertheless, the underlying mechanisms are still uncertain. The Wnt/β-catenin pathway, which plays a central role in intestinal homeostasis and sporadic colorectal cancer development, is regulated by phosphorylation cascades that are dependent and independent of Wnt. Here we report that a non- canonical Ser 552 phosphorylation in β-catenin, which promotes its nuclear accumulation and transcriptional activity, is blocked by metformin via AMPK-mediated PI3K/Akt signaling inhibition. 1. Introduction Despite advances in early detection, surgery and chemotherapy, colorectal cancer (CRC) remains the second leading cause of cancer- related mortality in the U.S. and other developed countries. Novel targets and agents for therapy and chemoprevention are urgently needed. They most likely will arise from a clear understanding of the signaling pathways involved and the consequent repurposing of cur- rently used drugs. Considerable evidence has linked metabolic syndrome, obesity and type 2 diabetes mellitus (T2DM), conditions characterized by periph- eral insulin resistance and hyperinsulinemia, with an increase in the incidence of multiple malignancies, including CRC (Gonzalez et al., 2017). Consequently, antidiabetic therapies have emerged as possible new strategies in the prevention and treatment of different types of cancer such as CRC (Chang et al., 2018; Gonzalez et al., 2017; Ikhlas and Ahmad, 2017; Jackson and Garcia-Albeniz, 2018; Klil-Drori et al., 2017; Kobiela et al., 2018). In epidemiological studies, the adminis- tration of the biguanide metformin, the most commonly prescribed anti-diabetic agent (He and Wondisford, 2015; Rena et al., 2013), has been associated with lower CRC incidence and mortality in T2DM pa- tients (Zhang et al., 2011). Furthermore, a recent double-blind placebo- controlled, randomized trial that showed that low-dose metformin significantly decreased colorectal adenoma recurrence (Higurashi et al., 2016). Despite its potential clinical importance, the cellular and mo- lecular mechanism(s) by which metformin acts as a preventive agent in CRC and other malignancies remains poorly understood (Li et al., 2018). It is recognized that aberrant activation of β-catenin signaling plays a central role in the majority of sporadic colorectal tumors (Clevers, 2006; Clevers and Nusse, 2012; McDonald et al., 2006). In most cases, the Wnt/β-catenin pathway undergoes an early deregulation that leads to the nuclear accumulation of β-catenin and the constitutive activation of its target genes (Cheah, 2009; Huels et al., 2015; Kinzler and Vogelstein, 1996; Krausova and Korinek, 2014; Polakis, 2012; Sansom et al., 2004; Walther et al., 2009). Phosphorylation cascades that are dependent and independent of Wnt signaling play a critical role in the control of β-catenin stability, intracellular distribution and transcrip- tional activity (Clevers, 2006; Fang et al., 2007; He et al., 2007; Taurin et al., 2006, 2008; Vermeulen et al., 2010). For example, the canonical sequential phosphorylation of β-catenin in its N-terminal domain tar- gets β-catenin for proteosomal degradation (Clevers and Nusse, 2012) whereas its non-canonical phosphorylation at Ser 552 and Ser 675 pro- motes its nuclear translocation and transcriptional activity (Fang et al., 2007; Rey et al., 2012; Taurin et al., 2006). We hypothesized that phosphorylation of β-catenin at Ser 552 in response to insulin and IGF-1 https://doi.org/10.1016/j.biocel.2019.05.004 Received 11 March 2019; Received in revised form 6 May 2019; Accepted 8 May 2019 ⁎ Corresponding author at: Hospital de Clínicas "José de San Martín", INIGEM-CONICET/UBA, Avenida Córdoba 2351, 4° Piso, Sala 5, 1120, Caba, Argentina. E-mail address: osrey@ucla.edu (O. Rey). International Journal of Biochemistry and Cell Biology 112 (2019) 88–94 Available online 10 May 2019 1357-2725/ © 2019 Elsevier Ltd. All rights reserved. T