Metabolic reprogramming identifies the most aggressive lesions at early phases of hepatic carcinogenesis.

// Marta Anna Kowalik 1, * , Giulia Guzzo 2, * , Andrea Morandi 3, * , Andrea Perra 1 , Silvia Menegon 4 , Ionica Masgras 2 , Elena Trevisan 2 , Maria Maddalena Angioni 1 , Francesca Fornari 5 , Luca Quagliata 6 , Giovanna Maria Ledda-Columbano 1 , Laura Gramantieri 5 , Luigi Terracciano 6 , Silvia Giordano 4 , Paola Chiarugi 3 , Andrea Rasola 2 , Amedeo Columbano 1 1 Department of Biomedical Sciences, University of Cagliari, 09124, Cagliari, Italy 2 Department of Biomedical Sciences, University of Padova, 35122, Padova, Italy 3 Department of Experimental and Clinical Biomedical Sciences, University of Florence, 50134 Firenze and Tuscan Tumor Institute, Florence, Italy 4 Department of Oncology, University of Torino School of Medicine, Candiolo Cancer Institute-FPO, IRCCS, 10060, Candiolo, Italy 5 Azienda Ospedaliero-Universitaria Policlinico S. Orsola Malpighi, 40138, Bologna, Italy 6 Molecular Pathology Division, Institute of Pathology, University Hospital of Basel, CH-4003, Basel, Switzerland * These authors have contributed equally to this work Correspondence to: Amedeo Columbano, email: columbano@unica.it Andrea Rasola, email: andrea.rasola@unipd.it Keywords: TRAP1, NRF2, HCC, oxidative phosphorylation, pentose phosphate pathway Received: January 15, 2016     Accepted: March 28, 2016     Published: April 7, 2016 ABSTRACT Metabolic changes are associated with cancer, but whether they are just bystander effects of deregulated oncogenic signaling pathways or characterize early phases of tumorigenesis remains unclear. Here we show in a rat model of hepatocarcinogenesis that early preneoplastic foci and nodules that progress towards hepatocellular carcinoma (HCC) are characterized both by inhibition of oxidative phosphorylation (OXPHOS) and by enhanced glucose utilization to fuel the pentose phosphate pathway (PPP). These changes respectively require increased expression of the mitochondrial chaperone TRAP1 and of the transcription factor NRF2 that induces the expression of the rate-limiting PPP enzyme glucose-6-phosphate dehydrogenase (G6PD), following miR-1 inhibition. Such metabolic rewiring exclusively identifies a subset of aggressive cytokeratin-19 positive preneoplastic hepatocytes and not slowly growing lesions. No such metabolic changes were observed during non-neoplastic liver regeneration occurring after two/third partial hepatectomy. TRAP1 silencing inhibited the colony forming ability of HCC cells while NRF2 silencing decreased G6PD expression and concomitantly increased miR-1; conversely, transfection with miR-1 mimic abolished G6PD expression. Finally, in human HCC patients increased G6PD expression levels correlates with grading, metastasis and poor prognosis. Our results demonstrate that the metabolic deregulation orchestrated by TRAP1 and NRF2 is an early event restricted to the more aggressive preneoplastic lesions.