Specific patterns of PIWI-interacting small noncoding RNA expression in dysplastic liver nodules and hepatocellular carcinoma

// Francesca Rizzo 1, * , Antonio Rinaldi 1, * , Giovanna Marchese 2 , Elena Coviello 1 , Assunta Sellitto 1 , Angela Cordella 3 , Giorgio Giurato 1, 2 , Giovanni Nassa 1, 2 , Maria Ravo 1 , Roberta Tarallo 1 , Luciano Milanesi 4 , Anna Destro 5 , Guido Torzilli 6, 7 , Massimo Roncalli 5, 6 , Luca Di Tommaso 5, 6 , Alessandro Weisz 1 1 Laboratory of Molecular Medicine and Genomics, Department of Medicine, Surgery and Dentistry ‘Schola Medica Salernitana’, University of Salerno, Baronissi (SA), Italy 2 Genomix4life, University of Salerno, Baronissi (SA), Italy 3 Fondazione IRCCS SDN, Napoli, Italy 4 Institute for Biomedical Technologies, National Research Council, Milano, Italy 5 Pathology Unit, Humanitas Clinical and Research Center, Rozzano-Milan, Italy 6 Department of Biomedical Sciences, Humanitas University, Rozzano-Milan, Italy 7 Hepatobiliary and General Surgery Division, Humanitas Clinical and Research Center, Rozzano-Milan, Italy * These authors contributed equally to this work Correspondence to: Alessandro Weisz, email: aweisz@unisa.it Keywords: hepatocarcinogenesis, hepatocellular carcinoma, piRNAs, small non-coding RNA, smallRNA-seq Received: April 08, 2016      Accepted: June 06, 2016      Published: July 13, 2016 ABSTRACT Hepatocellular carcinoma (HCC) is the result of a stepwise process, often beginning with development within a cirrhotic liver of premalignant lesions, morphologically characterized by low- (LGDN) and high-grade (HGDN) dysplastic nodules. PIWI-interacting RNAs (piRNAs) are small noncoding RNAs (sncRNAs), 23–35 nucleotide-long, exerting epigenetic and post-transcriptional regulation of gene expression. Recently the PIWI-piRNA pathway, best characterized in germline cells, has been identified also in somatic tissues, including stem and cancer cells, where it influences key cellular processes. Small RNA sequencing was applied to search for liver piRNAs and to profile their expression patterns in cirrhotic nodules (CNs), LGDN, HGDN, early HCC and progressed HCC (pHCC), analyzing 55 samples (14 CN, 9 LGDN, 6 HGDN, 6 eHCC and 20 pHCC) from 17 patients, aiming at identifying possible relationships between these sncRNAs and liver carcinogenesis. We identified a 125 piRNA expression signature that characterize HCC from matched CNs, correlating also to microvascular invasion in HCC. Functional analysis of the predicted RNA targets of deregulated piRNAs indicates that these can target key signaling pathways involved in hepatocarcinogenesis and HCC progression, thereby affecting their activity. Interestingly, 24 piRNAs showed specific expression patterns in dysplastic nodules, respect to cirrhotic liver and/or pHCC. The results demonstrate that the PIWI-piRNA pathway is active in human liver, where it represents a new player in the molecular events that characterize hepatocarcinogenesis, from early stages to pHCC. Furthermore, they suggest that piRNAs might be new disease biomarkers, useful for differential diagnosis of dysplastic and neoplastic liver lesions.