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C/EBPα-dependent preneoplastic tumor foci are the origin of hepatocellular carcinoma and aggressive pediatric liver cancer.

ABSTRACT: Recent publications show that classic hepatoblastoma (HBL) is the result of failure of hepatic stem cells to differentiate into hepatocytes, while hepatocellular carcinoma (HCC) is caused by the dedifferentiation of hepatocytes into cancer stem cells. However, the mechanisms of aggressive HBL and the mechanisms that cause dedifferentiation of hepatocytes into cancer stem cells are unknown. We found that, similar to HCC but opposite to classic HBL, aggressive HBL is the result of dedifferentiation of hepatocytes into cancer stem cells. In both cases of liver cancer, the dephosphorylation of tumor suppressor protein CCAAT/enhancer binding protein α (C/EBPα) at Ser193 (Ser190 in human protein) or mutation of Ser193 to Ala results in a modified protein with oncogenic activities. We have investigated liver cancer in a mouse model C/EBPα-S193A, in a large cohort of human HBL samples, and in Pten/p53 double knockout mice and found that these cancers are characterized by elevation of C/EBPα that is dephosphorylated at Ser190/193. We found that dephosphorylated C/EBPα creates preneoplastic foci with cancer stem cells that give rise to HCC and aggressive HBL. C/EBPα-dependent dedifferentiation of hepatocytes into cancer stem cells includes increased proliferation of hepatocytes, followed by generation of multinucleated hepatocytes and subsequent appearance of hepatocytes with delta-like 1 homolog-positive intranuclear inclusions. We further isolated C/EBPα-dependent multinucleated hepatocytes and found that they possess characteristics of tumor-initiating cells, including elevation of stem cell markers. C/EBPα-dependent cancer stem cells are observed in patients with aggressive HBL and in patients with a predisposition for liver cancer.

Conclusion

The earliest steps of adult HCC and aggressive pediatric liver cancer have identical features that include conversion of the tumor suppressor C/EBPα into an oncogenic isoform, which further creates preneoplastic foci where hepatocytes dedifferentiate into cancer cells, giving rise to liver cancer. (Hepatology 2018;67:1857-1871).

SUBMITTER: Cast A

PROVIDER: S-EPMC8221081 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Development of a new carcinoma cell line (HC-AFW1) derived from a pediatric liver tumor The cell line HC-AFW1 was derived from a 4 year old boy suffering from HCC through culturing and passage into immuno-deficient mice. The cell line is stable now for over 8 months of culture with a doubling time of 40 h. The tumor cells show an epithelial histology and express hepatoma proteins such as Alpha-fetoprotein (AFP), Glypican 3, E-cadherin, CD10, CD326, HepPar1, Vimentin and Desmin. Catenin beta shows a deletion of 49 amino acids in the exon 3 involving the phosphorylation sites of GSK3 and is detectable in the cell nuclei. Cytogenetic analysis revealed large anomalies in the chromosomal map including chromosomal aberrations found in hepatoblastoma as well as in adult HCC. Copy number analysis of two different passages of HC-AFW1 cells Two tumor specimens were used for tissue culture and xenotransplantation into NSG mice. Tumor cells derived from xenografts were cultured and designated as HC-AFW1. DNA was analyzed from the passage 2 (2P2). HC-AFW2 was derived from tissue culture without transfer in to mice. Primary tissue samples were minced into pieces of 3x3 mm and cultured on 6 well plates (Becton Dickenson, Frankfurt, Germany) in DMEM (GIBCO BRL, Carlsbad, CA) supplemented with 10% FCS (growth medium). Cell cultures were maintained in a humidified atmosphere containing 5% CO2 at 37°C. For subculturing cells were detached from the culture surface using accutase in Dulbecco´s PBS containing 0.5mM EDTA (PAA Laboratories GmbH, Cölbe, Germany) for 2-3 minutes at 37°C. A sub-cultivation ratio of 1:4 and 1:6 was performed twice per week. Cells were stored in liquid nitrogen as a suspension in complete growth medium with 10% DMSO. DNA from patient blood and tumor samples was isolated with the QiaAmp DNA mini Kit according to manufacturer's instructions (Qiagen, Hilden, Germany). Single nucleotide polymorphism (SNP) and copy number polymorphism (CNP) genotyping were performed using the Genome-Wide Human SNP Array 6.0 and Genotyping Console (GTC) software (Affymetrix, Santa Clara, CA).

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C/EBPα-dependent preneoplastic tumor foci are the origin of hepatocellular carcinoma and aggressive pediatric liver cancer.

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