Induction of autophagy promotes the growth of early preneoplastic rat liver nodules
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Marta Anna Kowalik1, Andrea Perra1, Giovanna Maria Ledda-Columbano1, Giuseppe Ippolito3, Mauro Piacentini2,3, Amedeo Columbano1 and Laura Falasca3
1 Department of Biomedical Sciences, University of Cagliari, Cagliari, Italy
2 Department of Biology, University of Rome “Tor Vergata”, Rome, Italy
3 National Institute for Infectious Disease, IRCCS “Lazzaro Spallanzani”, Rome, Italy
Mauro Piacentini, email:
Amedeo Columbano, email:
Keywords: preneoplastic nodules, autophagy, amiodarone, chloroquine, miR-224
Received: November 18, 2015 Accepted: December 23, 2015 Published: December 31, 2015
Although inhibition of autophagy has been implicated in the onset and progression of cancer cells, it is still unclear whether its dysregulation at early stages of tumorigenesis plays an oncogenic or a tumor suppressor role. To address this question, we employed the Resistant-Hepatocyte rat model to study the very early stages of hepatocellular carcinoma (HCC) development. We detected a different autophagy-related gene expression and changes in the ultrastructural profile comparing the most aggressive preneoplastic lesions, namely those positive for the putative progenitor cell marker cytokeratin-19 (KRT-19) with the negative ones. The ultrastructural and immunohistochemical analyses of KRT-19-positive preneoplastic hepatocytes showed the presence of autophagic vacuoles which was associated with p62, Ambra1 and Beclin1 protein accumulation suggesting that a differential modulation of autophagy occurs at early stages of the oncogenesis in KRT-19-positive vs negative lesions. We observed an overall decrease of the autophagy-related genes transcripts and a strong up-regulation of miR-224 in the KRT-19-positive nodules. Interestingly, the treatment with the autophagy inducer, Amiodarone, caused a marked increase in the proliferation of KRT-19 positive preneoplastic lesions associated with a strong increase of their size; by contrast, Chloroquine, an inhibitor of the autophagic process, led to their reduction. These results show that autophagy modulation is a very early event in hepatocarcinogenesis and is restricted to a hepatocytes subset in the most aggressive preneoplastic lesions. Our findings highlight the induction of autophagy as a permissive condition favouring cancer progression indicating in its inhibition a therapeutic goal to interfere with the development of HCC.
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