cancers Article Overexpression of Mitochondrial IF1 Prevents Metastatic Disease of Colorectal Cancer by Enhancing Anoikis and Tumor Infiltration of NK Cells Lucía González-Llorente 1,2,3 , Fulvio Santacatterina 1,2,3 , Ana García-Aguilar 1,2,3 , Cristina Nuevo-Tapioles 1,2,3 , Sara González-García 1 , Zuzana Tirpakova 1 , María Luisa Toribio 1 and José M. Cuezva 1,2,3, * 1 Departamento de Biología Molecular, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid (CSIC-UAM), 28049 Madrid, Spain; lucia.ovi@gmail.com (L.G.-L.); fsantacatterina@cbm.csic.es (F.S.); ana.garcia@cbm.csic.es (A.G.-A.); cnuevo@cbm.csic.es (C.N.-T.); sgonzalez@cbm.csic.es (S.G.-G.); zuzana.tirpak@gmail.com (Z.T.); mtoribio@cbm.csic.es (M.L.T.) 2 Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), ISCIII, 28049 Madrid, Spain 3 Instituto de Investigación Hospital 12 de Octubre, Universidad Autónoma de Madrid, 28049 Madrid, Spain * Correspondence: jmcuezva@cbm.csic.es; Tel.: +34-91-196-4618; Fax: +34-91-196-4420 Received: 24 October 2019; Accepted: 13 December 2019; Published: 19 December 2019   Abstract: Increasing evidences show that the ATPase Inhibitory Factor 1 (IF1), the physiological inhibitor of the ATP synthase, is overexpressed in a large number of carcinomas contributing to metabolic reprogramming and cancer progression. Herein, we show that in contrast to the findings in other carcinomas, the overexpression of IF1 in a cohort of colorectal carcinomas (CRC) predicts less chances of disease recurrence, IF1 being an independent predictor of survival. Bioinformatic and gene expression analyses of the transcriptome of colon cancer cells with differential expression of IF1 indicate that cells overexpressing IF1 display a less aggressive behavior than IF1 silenced (shIF1) cells. Proteomic and functional in vitro migration and invasion assays confirmed the higher tumorigenic potential of shIF1 cells. Moreover, shIF1 cells have increased in vivo metastatic potential. The higher metastatic potential of shIF1 cells relies on increased cFLIP-mediated resistance to undergo anoikis after cell detachment. Furthermore, tumor spheroids of shIF1 cells have an increased ability to escape from immune surveillance by NK cells. Altogether, the results reveal that the overexpression of IF1 acts as a tumor suppressor in CRC with an important anti-metastatic role, thus supporting IF1 as a potential therapeutic target in CRC. Keywords: colorectal cancer; ATPase Inhibitor Factor 1; metastasis; immune surveillance; prognosis 1. Introduction Colorectal cancer is the third most common type of cancer worldwide [1] and the need for biomarkers that inform of disease progression is required. A large number of studies have highlighted the importance of metabolism in cancer initiation and progression [2,3]. Mitochondria play a central role in intermediary metabolism, the provision of metabolic energy and in cellular signaling [4,5]. A primary hub of mitochondrial activities is the ATP synthase, the engine of oxidative phosphorylation that utilizes the proton electrochemical gradient generated by the respiratory chain for the synthesis of ATP [4]. Inhibition of the ATP synthase results in the inhibition of mitochondrial respiration and the concurrent activation of aerobic glycolysis, which is a hallmark of proliferation in normal, cancer and stem cells [4,6–8]. An enhanced glycolytic flux provides the carbon skeletons and reductive power required for the biosynthesis of amino acids, lipids, nucleotides and energy that are necessary to sustain proliferation [9,10]. Cancers 2020, 12, 22; doi:10.3390/cancers12010022 www.mdpi.com/journal/cancers