Hormonally Induced Hepatocellular Carcinoma in Diabetic Wild Type and Carbohydrate Responsive Element Binding Protein Knockout Mice.

Katrina Ehricke,Sharif Mortoga,Mohd Yasser,Diego F Calvisi,Jenny Zimmer,Christian Burkert,Majedul Karim,Frank Dombrowski,Silvia Ribback,Neetika Nath,Elisa Knuth,Stephan Singer,Christoph Metzendorf,Vincent Nuernberger

doi:10.3390/cells10102787

Abstract

Objective: In the rat, the pancreatic islet transplantation model is an established method to induce hepatocellular carcinomas (HCC), due to insulin-mediated metabolic and molecular alterations like increased glycolysis and de novo lipogenesis and the oncogenic AKT/mTOR pathway including upregulation of the transcription factor Carbohydrate-response element-binding protein (ChREBP). ChREBP could therefore represent an essential oncogenic co-factor during hormonally induced hepatocarcinogenesis. Methods: Pancreatic islet transplantation was implemented in diabetic C57Bl/6J (wild type, WT) and ChREBP-knockout (KO) mice for 6 and 12 months. Liver tissue was examined using histology, immunohistochemistry, electron microscopy and Western blot analysis. Finally, we performed NGS-based transcriptome analysis between WT and KO liver tumor tissues. Results: Three hepatocellular carcinomas were detectable after 6 and 12 months in diabetic transplanted WT mice, but only one in a KO mouse after 12 months. Pre-neoplastic clear cell foci (CCF) were also present in liver acini downstream of the islets in WT and KO mice. In KO tumors, glycolysis, de novo lipogenesis and AKT/mTOR signalling were strongly downregulated compared to WT lesions. Extrafocal liver tissue of diabetic, transplanted KO mice revealed less glycogen storage and proliferative activity than WT mice. From transcriptome analysis, we identified a set of transcripts pertaining to metabolic, oncogenic and immunogenic pathways that are differentially expressed between tumors of WT and KO mice. Of 315 metabolism-associated genes, we observed 199 genes that displayed upregulation in the tumor of WT mice, whereas 116 transcripts showed their downregulated expression in KO mice tumor. Conclusions: The pancreatic islet transplantation model is a suitable method to study hormonally induced hepatocarcinogenesis also in mice, allowing combination with gene knockout models. Our data indicate that deletion of ChREBP delays insulin-induced hepatocarcinogenesis, suggesting a combined oncogenic and lipogenic function of ChREBP along AKT/mTOR-mediated proliferation of hepatocytes and induction of hepatocellular carcinoma.

Highlights

Hepatocellular adenomas and carcinomas, proliferative activity, hepatocellular glycogen storage, blood glucose levels, and body weight were compared between these two strains
clear cell foci (CCF) of altered hepatocytes were detectable in liver acini downstream of the transplanted islets in diabetic transplanted wild type mice (WT) as well as Carbohydrate-response element-binding protein (ChREBP)-KO mice after 6 and 12 months
Hepatocytes of KO-CCF mice revealed massive glycogen but almost no lipid storage, suggesting inhibition of glycolysis in absence of ChREBP, and that reduction in glucose metabolism leads to glycogen accumulation in the liver (Figure 1C) [24]

Summary

Introduction

Alongside the well-known carcinogenesis related to alcohol abuse or hepatitis B or C virus infection with occurrence of cirrhosis and dysplastic nodules, epidemiologic studies have revealed an increasing association to risk factors like obesity and/or type 2 diabetes mellitus as part of the metabolic syndrome [3]. These metabolic disorders often lead to Non-Alcoholic Fatty Liver Disease (NAFLD), NonAlcoholic Steatohepatitis (NASH), and to HCC without development of cirrhosis in about. In different animal models of hepatocarcinogenesis, preneoplastic liver lesions often progress to hepatocellular adenomas (HCA) and HCC without pre-existing cirrhosis

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