Immunopositivity for Histone MacroH2A1 Isoforms Marks Steatosis-Associated Hepatocellular Carcinoma

Francesca Rappa,Arianna Marino,Manlio Vinciguerra,Lucie Bourgoin,Michelangelo Foti,Roger Williams,Francesco Cappello,Massimo Federici,Gianluigi Mazzoccoli,Nunzia Scibetta,Marion Peyrou,Christine Podrini,Azzura Greco,Valerio Pazienza

doi:10.1371/journal.pone.0054458

Abstract

BackgroundHepatocellular carcinoma (HCC) is one of the most common cancers worldwide. Prevention and risk reduction are important and the identification of specific biomarkers for early diagnosis of HCC represents an active field of research. Increasing evidence indicates that fat accumulation in the liver, defined as hepatosteatosis, is an independent and strong risk factor for developing an HCC. MacroH2A1, a histone protein generally associated with the repressed regions of chromosomes, is involved in hepatic lipid metabolism and is present in two alternative spliced isoforms, macroH2A1.1 and macroH2A1.2. These isoforms have been shown to predict lung and colon cancer recurrence but to our knowledge, their role in fatty-liver associated HCC has not been investigated previously.MethodsWe examined macroH2A1.1 and macroH2A1.2 protein expression levels in the liver of two murine models of fat-associated HCC, the high fat diet/diethylnistrosamine (DEN) and the phosphatase and tensin homolog (PTEN) liver specific knock-out (KO) mouse, and in human liver samples of subjects with steatosis or HCC, using immunoblotting and immunohistochemistry.ResultsProtein levels for both macroH2A1 isoforms were massively upregulated in HCC, whereas macroH2A1.2 was specifically upregulated in steatosis. In addition, examination of human liver samples showed a significant difference (p<0.01) in number of positive nuclei in HCC (100% of tumor cells positive for either macroH2A1.1 or macroH2A1.2), when compared to steatosis (<2% of hepatocytes positive for either isoform). The steatotic areas flanking the tumors were highly immunopositive for macroH2A1.1 and macroH2A1.2.ConclusionsThese data obtained in mice and humans suggest that both macroH2A1 isoforms may play a role in HCC pathogenesis and moreover may be considered as novel diagnostic markers for human HCC.

Highlights

The current pandemic in obesity/metabolic syndrome is a risk factor for many types of cancer
Regulation by macroH2A1 of oncogenes and/or tumor suppressors’ expression in hepatocytes could be relevant for fatty liver-associated Hepatocellular carcinoma (HCC), since the activities of these genes often link mechanistically hepatic steatosis to the onset of HCC, as we have previously shown for tumor suppressor phosphatase with tensin homology (PTEN) [23,24,25]
Mice fed with normal diet (ND) and treated with DEN injection at a low dose of 25 mg/kg did not display steatosis, they were indistinguishable from animal fed a ND and they were not retained for further analyses

Summary

Introduction

The current pandemic in obesity/metabolic syndrome is a risk factor for many types of cancer. Obesity is accompanied in up to 90% of cases by non-alcoholic fatty liver disease (NAFLD) [2] The latter is the consequence of an imbalance between lipid availability through fatty acid uptake and de novo lipogenesis, and lipid secretion and disposal via free fatty acid oxidation, resulting in hepatic accumulation of lipids (steatosis) [3]. MacroH2A1, a histone protein generally associated with the repressed regions of chromosomes, is involved in hepatic lipid metabolism and is present in two alternative spliced isoforms, macroH2A1.1 and macroH2A1.2. These isoforms have been shown to predict lung and colon cancer recurrence but to our knowledge, their role in fatty-liver associated HCC has not been investigated previously

Methods

Results

Conclusion