Immunopositivity for histone macroH2A1 isoforms marks steatosis-associated hepatocellular carcinoma.
BACKGROUND
Hepatocellular 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.


METHODS
We 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.


RESULTS
Protein 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.


CONCLUSIONS
These 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.
Department of Experimental Biomedicine and Clinical Neurosciences, Section of Human Anatomy, University of Palermo, Palermo, Italy.
Francesca
F
Rappa
Azzura
A
Greco
Christine
C
Podrini
Francesco
F
Cappello
Michelangelo
M
Foti
Lucie
L
Bourgoin
Marion
M
Peyrou
Arianna
A
Marino
Nunzia
N
Scibetta
Roger
R
Williams
Gianluigi
G
Mazzoccoli
Massimo
M
Federici
Valerio
V
Pazienza
Manlio
M
Vinciguerra
D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D006528:Carcinoma, Hepatocellular / Q000209:etiology / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D059305:Diet, High-Fat; D004052:Diethylnitrosamine; D005234:Fatty Liver / Q000139:chemically induced / Q000150:complications / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation; D022781:Hepatocytes / Q000378:metabolism / Q000473:pathology; D006657:Histones / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D008113:Liver Neoplasms / Q000209:etiology / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D051059:PTEN Phosphohydrolase / Q000172:deficiency / Q000235:genetics; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D059016:Tumor Microenvironment / Q000235:genetics
D015415:Biomarkers; D006657:Histones; D020033:Protein Isoforms; C120756:macroH2A histone; D004052:Diethylnitrosamine; D051059:PTEN Phosphohydrolase