Diethylnitrosamine Model Research Articles

Type I MET inhibitors cooperate with PD-1 blockade to promote rejection of hepatocellular carcinoma.

Blockade of the immune checkpoints programmed death-1 (PD-1) and cytotoxic lymphocyte antigen 4 has improved outcomes for patients with hepatocellular carcinoma (HCC), yet most still fail to achieve objective clinical benefit. MET plays key roles in both HCC tumorigenesis and immunosuppressive conditioning; however, inhibition of MET causes upregulation of PD-ligand 1 (PD-L1) suggesting the use of these inhibitors in the context of PD-1 blockade. We sought to investigate across the Hepa1-6, HCA-1 and diethylnitrosamine (DEN) models of HCC whether the combination of more specific type I versus more pleiotropic type II MET inhibitors would confer superior outcomes in combination with PD-1 blockade. While MET inhibition demonstrated cooperativity with αPD-1 across all three models, the type I MET inhibitor capmatinib showed optimal activity in combination and statistically significantly outperformed the combination with the type II inhibitor cabozantinib in the αPD-1 refractory DEN model. In both HCA-1 and DEN HCC, the capmatinib and αPD-1 combination enhanced CD8 T cell frequency and activation state while limiting intratumoral myeloid immune suppression. In vitro studies of antigen-specific T cell activation reveal significantly less inhibition of effector cytokine production and proliferation by capmatinib versus by type II or type III MET inhibitors. These findings suggest significant potential for clinical HCC combination studies of type I MET inhibitors and PD-1 blockade where prior trials using type II inhibitors have yielded limited benefit.

Proteomic analysis of DEN and CCl4-induced hepatocellular carcinoma mouse model.

Hepatocellular carcinoma (HCC) seriously threatens human health, mostly developed from liver fibrosis or cirrhosis. Since diethylnitrosamine (DEN) and carbon tetrachloride (CCl4)-induced HCC mouse model almost recapitulates the characteristic of HCC with fibrosis and inflammation, it is taken as an essential tool to investigate the pathogenesis of HCC. However, a comprehensive understanding of the protein expression profile of this model is little. In this study, we performed proteomic analysis of this model to elucidate its proteomic characteristics. Compared with normal liver tissues, 432 differentially expressed proteins (DEPs) were identified in tumor tissues, among which 365 were up-regulated and 67 were down-regulated. Through Gene Ontology (GO) analysis, Ingenuity Pathway Analysis (IPA), protein-protein interaction networks (PPI) analysis and Gene-set enrichment analysis (GSEA) analysis of DEPs, we identified two distinguishing features of DEN and CCl4-induced HCC mouse model in protein expression, the upregulation of actin cytoskeleton and branched-chain amino acids metabolic reprogramming. In addition, matching DEPs from the mouse model to homologous proteins in the human HCC cohort revealed that the DEN and CCl4-induced HCC mouse model was relatively similar to the subtype of HCC with poor prognosis. Finally, combining clinical information from the HCC cohort, we screened seven proteins with prognostic significance, SMAD2, PTPN1, PCNA, MTHFD1L, MBOAT7, FABP5, and AGRN. Overall, we provided proteomic data of the DEN and CCl4-induced HCC mouse model and highlighted the important proteins and pathways in it, contributing to the rational application of this model in HCC research.

Diethylnitrosamine Induction of Hepatocarcinogenesis in Mice.

Diethylnitrosamine (DEN) is a chemical hepatocarcinogenic agent that triggers a large array of oncogenic mutations after a single injection. Initiated hepatocytes subsequently undergo clonal expansion within a proliferative environment, rendering the DEN model a comprehensive carcinogen. In rodent studies, DEN finds extensive utility in experimental liver cancer research, mimicking several aspects of human hepatocellular carcinoma (HCC), including angiogenesis, metabolic reprogramming, immune exhaustion, and the ability to metastasize. Beyond the wealth of scientific insights gleaned from this model, the objective of this chapter is to review morphological, genomic, and immunological characteristics associated to DEN-induced HCC. Furthermore, this chapter provides a detailed procedural guide to effectively induce hepatocarcinogenesis in mice through a single intraperitoneal injection of DEN.

Cannabis sativa demonstrates anti-hepatocellular carcinoma potentials in animal model: in silico and in vivo studies of the involvement of Akt

BackgroundTargeting protein kinase B (Akt) and its downstream signaling proteins are promising options in designing novel and potent drug candidates against hepatocellular carcinoma (HCC). The present study explores the anti-HCC potentials of Cannabis sativa (C. sativa) extract via the involvement of Akt using both in silico and in vivo animal models of HCC approaches.MethodsPhytoconstituents of C. sativa extract obtained from Gas Chromatography Mass-spectrometry (GCSM) were docked into the catalytic domain of Akt-2. The Diethylnitrosamine (DEN) model of HCC was treated with C. sativa extract. The effects of C. sativa extract treatments on DEN model of hepatocellular carcinoma were assessed by One-way analysis of variance (ANOVA) of the treated and untreated groupsResultThe lead phytoconstituents of C. sativa extract, Δ-9-tetrahydrocannabinol (Δ-9-THC) and cannabidiol form stable hydrophobic and hydrogen bond interactions within the catalytic domain of Akt-2. C. sativa extract (15 mg/kg and 30 mg/kg) respectively gives a 3-fold decrease in the activities of liver function enzymes when compared with the positive control (group 2). It also gives a 1.5-fold decrease in hepatic lipid peroxidation and elevates serum antioxidant enzymes’ activities by 1-fold in HCC treated Wistar rats when compared with the positive control (group 2). In an animal model of hepatocellular carcinoma, C. sativa extract significantly downregulated Akt and HIF mRNAs in groups 3, 4, and 5 with 2, 1.5, 2.5-fold decrease relative to group 2. VEGF mRNA was downregulated by 1.5-fold decrease in groups 3-5 when compared to group 2. The expression of XIAP mRNA was downregulated by 1.5, 2, and 1.25-folds in groups 3, 4, and 5 respectively, in comparison with group 2. In comparison to group 2, COX-2 mRNA levels were downregulated by 1.5, 1, and 1-folds in groups 3–5. In groups 3–5, CRP mRNA was downregulated by 2-fold in comparison with group 2. In groups 3–5, p21 mRNA was upregulated by 2, 2.5, and 3-folds, respectively when compared with group 2. It upregulated p53 mRNA by 2.5, 3.5, and 2.5-folds in groups 3–5 in comparison with group 2. It downregulated AFP mRNA by 3.5, 2.5, .2.5-folds in groups 3, 4, and 5 respectively when compared with group 2. Histologic analysis showed that C. sativa extract reduced necrosis and inflammation in HCC.ConclusionC. sativa demonstrates anti-hepatocellular carcinoma potentials in an animal model of HCC and with the involvement of Akt. Its anticancer potential is mediated through antiangiogenic, proapoptotic, cycle arrest, and anti-inflammatory mechanisms.In future studies, the mechanisms of anti-HCC effects of Δ-9-tetrahydrocannabinol (Δ-9- THC) and cannabidiol via the PI3K-Akt signaling pathways should be explored.

Abstract 2257: Effect ofALDH1L1folate enzyme on hepatocellular carcinoma inachemical carcinogenesismodel

Abstract Background: ALDH1L1 (aldehyde dehydrogenase 1 family member L1, or cytosolic 10-formyltetrahydrofolate dehydrogenase) is an abundant enzyme in folate metabolism representing about 1% of total soluble protein in hepatocytes. Expression of this protein is strongly and ubiquitously downregulated in human cancers through the promoter methylation. Several studies indicate that patients with hepatocellular carcinoma who had low expression of ALDH1L1 had poorer prognosis than those with high expression. Hypothesis: We propose that in the absence of ALDH1L1, liver tumors proliferate faster and grow to a larger size. Methods: The effect of the Aldh1l1 knockout (Aldh1l1−/−) on hepatocellular carcinoma was investigated using DEN (diethyl nitrosamine) model of chemical carcinogenesis. Fifteen-days-old male Aldh1l1−/- mice and their wild-type littermate controls (Aldh1l1+/+) were injected intraperitoneally with DEN at the dose of 15 mg/kg body weight. Mice were sacrificed 10, 20, 28- and 36-weeks post-injection and livers were examined for for histopathology. Results: Significant reduction in total body weight was observed in the DEN-injected knockout compared to wild type animals at 28 and 36 weeks. Immunohistochemical analysis reveals that tumor size was significantly bigger in Aldh1l1−/− compared to Aldh1l1+/+ mice and also indicated fibrosis in livers of knockout vs wild-type mice. Vascular involvement, highlighted by reticulin staining, was present in both Aldh1l1−/− and Aldh1l1+/+ mice as early as 20 weeks after the injection. Tumor multiplicity did not differ significantly between the Aldh1l1−/− and Aldh1l1+/+ animals. Conclusion:. Aldh1l1 knockout promoted aggressiveness of liver tumors without affecting the tumor initiation. Acknowledgement: These studies were supported by the National Institutes of Health grants DK54388 and CA095030 (S.A.K.). Citation Format: Jaspreet Sharma, Natalia I. Krupenko, Peter Pediaditakis, Kristi Helke, Kyle C. Strickland, Sergey A. Krupenko. Effect ofALDH1L1folate enzyme on hepatocellular carcinoma inachemical carcinogenesismodel [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2257.

Inhibitory effect of Biejiajian pills against diethylnitrosamine-induced hepatocarcinogenesis in rats

To study the inhibitory effect of Biejiajian pills (BJJ) agaisnt diethylnitrosamine (DEN)-induced hepatocarcinogenesis and explore the relation between this effect and the inflammasome signaling pathway. Sixty-five male SD rats were randomly divided into control group, DEN model group, and 3 BJJ treatment groups at low, medium and high dose (with daily dose of 0.55, 1.1 and 2.2 g/kg, respectively, for 12 consecutive weeks starting from the 5th week after modeling). The pathological changes of the liver tissue were observed with HE and Masson staining, and serum levels of alanine transaminase (ALT), glutamic oxaloacetic transaminase (AST), alkaline phosphatase (ALP) and total bilirubin (TBIL) of the rats were detected using ELISA. Oxidation stress in the liver tissue was assessed with ELISA, and Western blotting and ELISA were used to detect the molecular expressions of inflammasome-related pathway. BJJ significantly inhibited tumor growth in the liver of the rats. HE and Masson staining showed that BJJ treatment obviously ameliorated liver fibrosis and reduced cancer cell and inflammatory cell infiltration in the liver. BJJ significantly reduced elevations of serum ALT, AST, ALP and TBIL levels, increased the contents of superoxide dismutase, catalase and glutathione peroxidase in the liver and suppressed malondialdehyde in Den-treated rats. BJJ also dose-dependently decreased the expressions of NLRP3, apoptosis-associated speck-like protein (ASC), caspase-1, pro-IL-1β, pro-IL-18, IL-1β and IL-18 in the liver of Den-treated rats. BJJ treatment can dose-dependently inhibit DEN-induced hepatocarcinogenesis by enhancing antioxidant capacity and down-regulating inflammatory-related pathways in rats.

Potential role of gut microbiota, the proto-oncogene PIKE (Agap2) and cytochrome P450 CYP2W1 in promotion of liver cancer by alcoholic and nonalcoholic fatty liver disease and protection by dietary soy protein

We have previously demonstrated promotion of diethylnitrosamine (DEN) initiated liver tumorigenesis after feeding diets high in fat or ethanol (EtOH) to male mice. This was accompanied by hepatic induction of the proto-oncogene PIKE (Agap2). Switch of dietary protein from casein to soy protein isolate (SPI) significantly reduced tumor formation in these models. We have linked EtOH consumption in mice to microbial dysbiosis. Adoptive transfer studies demonstrate that microbiota from mice fed ethanol can induce hepatic steatosis in the absence of ethanol suggesting that microbiota or the microbial metabolome play key roles in development of fatty liver disease. Feeding SPI significantly changed gut bacteria in mice increasing alpha diversity (P < 0.05) and levels of Clostidiales spp. Feeding soy formula to piglets also resulted in significant changes in microbiota, the pattern of bile acid metabolites and in inhibition of the intestinal-hepatic FXR/FGF19-SHP pathway which has been linked to both steatosis and hepatocyte proliferation. Moreover, feeding SPI also resulted in induction of hepatic PPARα signaling and inhibition of PIKE mRNA expression coincident with inhibition of steatosis and cancer prevention. Feeding studies in the DEN model with differing dietary fats demonstrated tumor promotion specific to the saturated fat, cocoa butter relative to diets containing olive oil or corn oil associated with microbial dysbiosis including dramatic increases in Lachnospiraceae particularly from the genus Coprococcus. Immunohistochemical analysis demonstrated that tumors from EtOH-fed mice and patients with alcohol-associated HCC also expressed high levels of a novel cytochrome P450 enzyme CYP2W1. Additional adoptive transfer experiments and studies in knockout mice are required to determine the exact relationship between soy effects on the microbiota, expression of PIKE, CYP2W1, PPARα activation and prevention of tumorigenesis.

Characterization of HCC Mouse Models: Towards an Etiology-Oriented Subtyping Approach.

Murine liver tumors often fail to recapitulate the complexity of human hepatocellular carcinoma (HCC), which might explain the difficulty to translate preclinical mouse studies into clinical science. The aim of this study was to evaluate a subtyping approach for murine liver cancer models with regard to etiology-defined categories of human HCC, comparing genomic changes, histomorphology, and IHC profiles. Sequencing and analysis of gene copy-number changes [by comparative genomic hybridization (CGH)] in comparison with etiology-dependent subsets of HCC patients of The Cancer Genome Atlas (TCGA) database were conducted using specimens (75 tumors) of five different HCC mouse models: diethylnitrosamine (DEN) treated wild-type C57BL/6 mice, c-Myc and AlbLTαβ transgenic mice as well as TAK1LPC-KO and Mcl-1Δhep mice. Digital microscopy was used for the assessment of morphology and IHC of liver cell markers (A6-CK7/19, glutamine synthetase) in mouse and n = 61 human liver tumors. Tumor CGH profiles of DEN-treated mice and c-Myc transgenic mice matched alcohol-induced HCC, including morphologic findings (abundant inclusion bodies, fatty change) in the DEN model. Tumors from AlbLTαβ transgenic mice and TAK1LPC-KO models revealed the highest overlap with NASH-HCC CGH profiles. Concordant morphology (steatosis, lymphocyte infiltration, intratumor heterogeneity) was found in AlbLTαβ murine livers. CGH profiles from the Mcl-1Δhep model displayed similarities with hepatitis-induced HCC and characteristic human-like phenotypes (fatty change, intertumor and intratumor heterogeneity). IMPLICATIONS: Our findings demonstrate that stratifying preclinical mouse models along etiology-oriented genotypes and human-like phenotypes is feasible. This closer resemblance of preclinical models is expected to better recapitulate HCC subgroups and thus increase their informative value.

Pioglitazone Reduces Hepatocellular Carcinoma Development in Two Rodent Models of Cirrhosis

BackgroundHepatocellular carcinoma (HCC) is one of the deadliest malignancies worldwide due to the lack of effective treatments. Chemoprevention in high-risk patients is a promising, alternative strategy. In this study, pioglitazone was investigated for its ability to prevent hepatocarcinogenesis in two rodent models of cirrhosis. MethodsIn the first model, male Wistar rats were given repeated, low-dose injections of diethylnitrosamine (DEN) to accurately recapitulate the progression of fibrosis to cirrhosis and HCC. In the second model, a single dose of DEN was administered to male C57Bl/6 pups at day fifteen followed by administration of a choline-deficient, L-amino acid defined, high-fat diet (CDAHFD) at week six for 24 weeks. Pioglitazone treatment started at the first signs of fibrosis in both models. ResultsPioglitazone effectively reduced fibrosis progression and HCC development in both models. Gross tumor nodules were significantly reduced after pioglitazone treatment (7.4±1.6 vs. 16.6±2.6 in the rat DEN model and 5.86±1.82 vs. 13.2±1.25 in the mouse DEN+CDAHFD model). In both models, pioglitazone reduced the activation of mitogen-activated protein kinase (MAPK) and upregulated the hepato-protective AMP-activated protein kinase (AMPK) pathway via increasing circulating adiponectin production. ConclusionPioglitazone is an effective agent for chemoprevention in rodents and could be repurposed as a multi-targeted drug for delaying liver fibrosis and hepatocarcinogenesis.

Abstract 4566: Differential reactivation of fetal/neonatal genes in mouse liver tumors induced in cirrhotic and non-cirrhotic conditions

Abstract Hepatocellular carcinoma (HCC) is usually associated with chronic liver injury, typically cirrhosis, although it could be developed in apparenty intact livers. To explore the tumorigenetic mechanisms underlying these different conditions, we compared mRNA expression profiles in mouse liver tumors induced by repeated injections of CCl4 (cirrhotic protocol) and a single diethylnitrosamine (DEN) injection at 2-week-old (non-cirrhotic protocol) using a cDNA microarray. In the CCl4 model, numerous small tumors appeared in cirrhotic liver parenchyma, while in the DEN model, multiple large tumors developed in a non-cirrhotic background. We identified tumor-specific genes that were differentially expressed in either CCl4 or DEN model, as well as expressed in both models. The levels and patterns of mRNA expression of these genes were verified by RT-qPCR analyses. The mRNA expression of Igf2, H19, Krt20, and Cbr3 were predominantly increased in CCl4 tumors; that of Gpc3, Tff3, Akr1c18, Afp, and Abcd2 were predominantly increased in DEN tumors; that of Ly6d, Cpe, Slpi, and Scd2 was increased at similar levels in CCl4 and DEN tumors. The mRNA expresion of Igf2bp3, which is known to be functionally correlated with Igf2, was also increased only in CCl4 tumors. A positive correlation was found between the expression of Igf2 mRNA and H19 mRNA. The mRNA expresion of these liver tumor-specific genes was not significantly correlated with the proliferative activity of tumor cells, as estimated by Ki-67 immunohistochemistry, either in CCl4 or DEN tumors. Interestingly, all of these genes, with only exception being Cbr3, were highly expressed in the mouse livers during the fetal/neonatal periods. We also examined mRNA expression of these genes in liver tumors induced by chronic thioacetamide (TAA) treatment, another cirrhotic liver tumor protocol, and found that TAA-induced tumors shared a similar pattern of expression profile as that of CCl4 tumors. We further investigated mRNA expression of the genes in mouse liver tumors induced by the Sleeping Beauty transposon-mediated somatic integration of active Akt (myrAkt) and mutant Hras (HrasV12) genes. Hydrodynamic tail vein injection of the oncogenes rapidly induced multiple liver tumors within 2 months without developing chronic liver injury or cirrhosis. These tumors overexpressed most of the above genes, except for Igf2, Igfbp3, H19, and Tff3. Our results show that mouse liver tumors reactivate numerous fetal/neonatal genes, some of which are specific to the cirrhotic (e.g., Igf2) and non-cirrhotic (e.g., Gpc3, Tff3, Akr1c18) modes of pathogenesis. Furthermore, the IGF2 axis, H19, and Tff3 might be specifically involved in the processes during the development of liver tumors, not simply reflecting neoplastic transformation of hepatocytes. Citation Format: Xi Chen, Masahiro Yamamoto, Kiyonaga Fujii, Yasuharu Nagahama, Bing Xin, Takako Ooshio, Yoko Okada, Yuji Nishikawa. Differential reactivation of fetal/neonatal genes in mouse liver tumors induced in cirrhotic and non-cirrhotic conditions. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4566. doi:10.1158/1538-7445.AM2015-4566

Differential reactivation of fetal/neonatal genes in mouse liver tumors induced in cirrhotic and non-cirrhotic conditions.

Hepatocellular carcinoma develops in either chronically injured or seemingly intact livers. To explore the tumorigenic mechanisms underlying these different conditions, we compared the mRNA expression profiles of mouse hepatocellular tumors induced by the repeated injection of CCl4 or a single diethylnitrosamine (DEN) injection using a cDNA microarray. We identified tumor-associated genes that were expressed differentially in the cirrhotic CCl4 model (H19, Igf2, Cbr3, and Krt20) and the non-cirrhotic DEN model (Tff3, Akr1c18, Gpc3, Afp, and Abcd2) as well as genes that were expressed comparably in both models (Ly6d, Slpi, Spink3, Scd2, and Cpe). The levels and patterns of mRNA expression of these genes were validated by quantitative RT-PCR analyses. Most of these genes were highly expressed in mouse livers during the fetal/neonatal periods. We also examined the mRNA expression of these genes in mouse tumors induced by thioacetamide, another cirrhotic inducer, and those that developed spontaneously in non-cirrhotic livers and found that they shared a similar expression profile as that observed in CCl4-induced and DEN-induced tumors, respectively. There was a close relationship between the expression levels of Igf2 and H19 mRNA, which were activated in the cirrhotic models. Our results show that mouse liver tumors reactivate fetal/neonatal genes, some of which are specific to cirrhotic or non-cirrhotic modes of pathogenesis.

Hepatocyte-specific Bid depletion reduces tumor development by suppressing inflammation-related compensatory proliferation.

Liver cancer is a major health-care concern and its oncogenic mechanisms are still largely unclear. Persistent hepatocyte cell death is a common feature among various chronic liver diseases, the blocking of which presents as logical treatment. Therefore, we aimed at investigating tumor development in mice with hepatocyte-specific Bid depletion--a BH3-only Bcl-2 family member that amplifies apoptotic death signals. Hepatocyte-specific conditional Bid-knockout mice (Bid(Δhep)) were injected with 25 mg/kg diethylnitrosamine (DEN) at 14 days of age, and liver tumorigenesis was investigated 9 months later. Additionally, different models of acute liver injury were used including: acute high-dose DEN challenge, 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) diet and carbon tetrachloride (CCL4) injection. Bid(Δhep) mice developed significantly fewer tumors, showed smaller maximal and average tumor size and reduced tumor incidence. In the acute DEN model, 48 h post injection we observed a significant reduction in liver injury in Bid(Δhep) animals, assessed via serum transaminases and liver histopathology. Furthermore, TNF-α, IL-1ß, cJUN and IL-6 mRNA expression was reduced. These findings were accompanied by reduced compensatory hepatocyte proliferation in Bid(Δhep) mice when compared with controls by immunohistochemistry for Ki67 and proliferating cell nuclear antigen 48 h after DEN injection. In the acute CCL4 model, Bid(Δhep) mice displayed reductions in liver injury and inflammation when compared with controls. No differences in liver injury and serum bilirubin levels were detected in Bid(Δhep) and Bid(flo/flo) mice fed with DDC, which induces bile duct injury and a ductular reaction. Our study demonstrates that in DEN-induced hepatocellular carcinoma, the inhibition of hepatocyte death pathways through Bid deletion protects animals from tumorigenesis. These results suggest that reducing hepatocyte cell death, liver inflammation and compensatory proliferation has a stronger beneficial effect than the potential side effect of enhancing tumor cell survival.

Lack of gp130 expression in hepatocytes attenuates tumor progression in the DEN model.

Chronic liver inflammation is a crucial event in the development and growth of hepatocellular carcinoma (HCC). Compelling evidence has shown that interleukin-6 (IL-6)/gp130-dependent signaling has a fundamental role in liver carcinogenesis. Thus, in the present study we aimed to investigate the role of gp130 in hepatocytes for the initiation and progression of HCC. Hepatocyte-specific gp130 knockout mice (gp130Δhepa) and control animals (gp130f/f) were treated with diethylnitrosamine (DEN). The role of gp130 for acute injury (0–144 h post treatment), tumor initiation (24 weeks) and progression (40 weeks) was analyzed. After acute DEN-induced liver injury we observed a reduction in the inflammatory response in gp130Δhepa animals as reflected by decreased levels of IL-6 and oncostatin M. The loss of gp130 slightly attenuated the initiation of HCC 24 weeks after DEN treatment. In contrast, 40 weeks after DEN treatment, male and female gp130Δhepa mice showed smaller tumors and reduced tumor burden, indicating a role for hepatocyte-specific gp130 expression during HCC progression. Oxidative stress and DNA damage were substantially and similarly increased by DEN in both gp130f/f and gp130Δhepa animals. However, gp130Δhepa livers revealed aberrant STAT5 activation and decreased levels of transforming growth factor-β (TGFβ), pSMAD2/3 and SMAD2, whereas phosphorylation of STAT3 at Tyr705 and Ser727 was absent. Our results indicate that gp130 deletion in hepatocytes reduces progression, but not HCC initiation in the DEN model. Gp130 deletion resulted in STAT3 inhibition but increased STAT5 activation and diminished TGF-dependent signaling. Hence, blocking gp130 in hepatocytes might be an interesting therapeutic target to inhibit the growth of HCC.

Activation of the transforming growth factor-β/SMAD transcriptional pathway underlies a novel tumor-promoting role of sulfatase 1 in hepatocellular carcinoma.

In vitro studies have proposed a tumor suppressor role for sulfatase 1 (SULF1) in hepatocellular carcinoma (HCC); however, high expression in human HCC has been associated with poor prognosis. The reason underlying this paradoxical observation remains to be explored. Using a transgenic (Tg) mouse model overexpressing Sulf1 (Sulf1-Tg), we assessed the effects of SULF1 on the diethylnitrosamine model of liver carcinogenesis. Sulf1-Tg mice show a higher incidence of large and multifocal tumors with diethylnitrosamine injection compared to wild-type mice. Lung metastases were found in 75% of Sulf1-Tg mice but not in wild-type mice. Immunohistochemistry, immunoblotting, and reporter assays all show a significant activation of the transforming growth factor-β (TGF-β)/SMAD transcriptional pathway by SULF1 both in vitro and in vivo. This effect of SULF1 on the TGF-β/SMAD pathway is functional; overexpression of SULF1 promotes TGF-β-induced gene expression and epithelial-mesenchymal transition and enhances cell migration/invasiveness. Mechanistic analyses demonstrate that inactivating mutation of the catalytic site of SULF1 impairs the above actions of SULF1 and diminishes the release of TGF-β from the cell surface. We also show that SULF1 expression decreases the interaction between TGF-β1 and its heparan sulfate proteoglycan sequestration receptor, TGFβR3. Finally, using gene expression from human HCCs, we show that patients with high SULF1 expression have poorer recurrence-free survival (hazard ratio 4.1, 95% confidence interval 1.9-8.3; P = 0.002) compared to patients with low SULF1. We also found strong correlations of SULF1 expression with TGF-β expression and with several TGF-β-related epithelial-mesenchymal transition genes in human HCC. Our study proposes a novel role of SULF1 in HCC tumor progression through augmentation of the TGF-β pathway, thus defining SULF1 as a potential biomarker for tumor progression and a novel target for drug development for HCC.

Lack of gp130 expression in hepatocytes attenuates tumor progression in the DEN model

Background & Aim: Chronic liver inflammation is a crucial event in the development and growth of hepatocellular carcinoma (HCC). Compelling evidence has shown that IL-6/gp130-dependent signaling plays a fundamental role in liver carcinogenesis. Thus, in the present study we aimed to investigate the role of gp130 in hepatocytes for the initiation and progression of HCC. Methods: Hepatocyte-specific gp130 knockout mice (gp130Δhepa) and control animals (gp130f/f) were treated with diethylnitrosamine (DEN). The role of gp130 for acute injury (0 – 5 days), tumor initiation (24 weeks) and progression (40 weeks) was analyzed. Results: After acute DEN-induced liver injury we observed a reduction in the inflammatory response as reflected by decreased IL-6 and oncostatin M (OSM) levels in gp130Δhepa animals. Loss of gp130 slightly attenuated the initiation of HCC 24 weeks after DEN-induced tumor initiation. In contrast, 40 weeks after DEN treatment, gp130Δhepa livers displayed smaller tumors and reduced tumor burden, indicating a role for hepatocyte-specific gp130 expression during HCC progression. We found increased oxidative stress and substantial DNA damage in animals after DEN injection, but no significant difference between gp130f/f and gp130Δhepa animals. However, while STAT3 phosphorylation was absent in gp130Δhepa hepatocytes we found STAT5 activation and decreased TGFβ-dependent activity in these livers. Conclusion: Our results indicate that gp130 deletion in hepatocytes reduces progression, but not HCC initiation in the DEN model. Gp130 deletion resulted in STAT3 inhibition but increased STAT5 activation and diminished TGFβ-dependent signaling. Hence, blocking gp130 in hepatocytes is an interesting therapeutic target to inhibit the growth of HCC.

Dietary effects on liver tumor burden in mice treated with the hepatocellular carcinogen diethylnitrosamine

Mice exposed to the hepatocellular carcinogen diethylnitrosamine at 2 weeks of age have a high risk of developing primary liver tumors later in life. Previous studies have demonstrated that diethylnitrosamine-treated mice have increased tumor burden when fed an obesigenic "Western" diet rich in lard fat and sugar. However, the role of dietary fats vs. sugars in the promotion of liver cancer is poorly understood. The aim of this study was to determine how altering dietary fats vs. sugars affects tumor burden in the diethylnitrosamine model. C57BL/6N mice were treated with diethylnitrosamine at 2 weeks of age and, from 6 to 32 weeks of age, fed one of five diets that differed in fat and sugar content, including normal chow, ketogenic, and Western diets. Mice fed sugar-rich diets had the greatest tumor burden irrespective of dietary fat content. In contrast, mice fed a high-fat low-sugar diet had the least tumor burden despite obesity and glucose intolerance. When evaluated as independent variables, tumor burden was positively correlated with hepatic fat accumulation, postprandial insulin, and liver IL-6, and inversely correlated with serum adiponectin. In contrast, tumor burden did not correlate with adiposity, fasting insulin, or glucose intolerance. Furthermore, mice fed high sugar diets had lower liver expression of p21 and cleaved caspase-3 compared to mice fed low sugar diets. These data indicate that dietary sugar intake contributes to liver tumor burden independent of excess adiposity or insulin resistance in mice treated with diethylnitrosamine.

CXCR7 is up-regulated in human and murine hepatocellular carcinoma and is specifically expressed by endothelial cells

Development of hepatocellular carcinoma (HCC) is a complex and progressive disease that involves cycles of liver cell death, inflammation, and tissue regeneration/remodelling. Chemokines and chemokine receptors play numerous and integral roles in the disease progression of HCC. Here we investigated the novel chemokine receptor CXCR7/RDC1 in HCC progression, its two known ligands CXCL12 and CXCL11, as well as the other CXCL12 receptor, CXCR4. Our results show that in a cohort of 408 human HCCs, CXCR7 and CXCL11 were significantly higher in tumours compared to normal liver controls (5- and 10-fold, respectively). Immunohistochemical (IHC) staining on human HCC sections confirmed that both CXCL11 and CXCR7 were much higher in cancer tissues. Furthermore, IHC staining revealed that CXCR7 protein was only expressed in endothelial cells whereas CXCL11 exhibited a much broader tissue expression. At the cellular level we observed that in vitro, human microvascular endothelial cells (HMEC-1) up-regulated CXCR7 under hypoxic and acidic pH conditions, which are well known characteristics of the HCC tumour micro-environment. As for its ligand, we observed that IFNγ robustly induced CXCL11 in hepatic stellate cells, hepatocytes, and HMEC-1s. In addition, in the mouse Diethylnitrosamine model of hepatocarcinogenesis we observed a very strong induction of CXCR7 and CXCL11 transcripts, confirming that CXCR7/CXCL11 up-regulation is conserved between human and mice liver cancer. Altogether, our results strongly support the hypothesis that the CXCL11/CXCR7 pathway is involved HCC progression.

BRE over-expression promotes growth of hepatocellular carcinoma

BRE, also known as TNFRSF1A modulator and BRCC45, is an evolutionarily highly conserved protein. It is a death receptor-associated protein in cytoplasm and a component of BRCA1/2-containing DNA repair complex in nucleus. BRE was found to have anti-apoptotic activity. Over-expression of BRE by transfection promoted survival of cell lines against apoptotic induction; whereas depletion of the protein by siRNA resulted in the opposite. In vivo anti-apoptotic activity of BRE was demonstrated by significant attenuation of Fas-induced acute fulminant hepatitis in transgenic mice expressing the human protein specifically in the liver. BRE was also implicated in tumor promotion by the accelerated tumor growth of Lewis Lung carcinoma transfected with human BRE; and by high expression of BRE specifically in the tumoral regions of human hepatocellular carcinoma (HCC). The present study was to test directly if transgenic expression of BRE in livers could promote HCC development in neonatal diethylnitrosamine model. By 8 months after tumor induction, the maximal sizes of tumor nodules of transgenic mice were significantly larger than those of the non-transgenic controls, although the numbers of tumor nodules between the two groups did not significantly differ. Importantly, as in human HCC, the mouse endogenous BRE level was up-regulated in mouse HCC nodules. These results show that BRE over-expression can indeed promote growth, though not initiation, of liver tumors. Furthermore, the common occurrence of BRE over-expression in human and mouse HCC suggests that up-regulation of BRE is functionally important in liver tumor development.

Deletion of Bid Impedes Cell Proliferation and Hepatic Carcinogenesis

Mechanisms that control the proliferation capability of the initiated cells during hepatocarcinogenesis are still largely unclear. We investigated the role of a pro-death Bcl-2 family protein, Bid, in liver tumor development using a neonatal diethylnitrosamine model. Diethylnitrosamine was administrated to 15-day-old wild-type and bid-null mice. The development of microfoci at the early stage and of gross tumors at the later stage was compared between the two groups of mice. Both microfoci and gross tumor development were significantly retarded in the bid-null mice, despite reduced cell death as measured by TUNEL staining. Further studies indicated that there were significantly less proliferating cells in diethylnitrosamine-treated bid-null livers. The regulation of cell proliferation by Bid was confirmed in two other systems not involving carcinogenesis. Hepatocyte proliferation following partial hepatectomy and T lymphocyte proliferation following anti-CD3 stimulation were both retarded in bid-null mice. Thus, these studies revealed a previously undisclosed function of Bid in regulating cell proliferation, which can be important to tumor development. Furthermore, the role of Bid in promoting hepatocarcinogenesis is in contrast to its reported role in suppressing myeloid leukemia and thus suggests an organ- and/or etiology-specific role of the Bcl-2 family proteins in regulating oncogenesis.

Demonstration of direct lineage between hepatocytes and hepatocellular carcinoma in diethylnitrosamine-treated rats

The question whether hepatocellular carcinoma (HCC) arises from dedifferentiation of mature hepatocytes or from proliferation of liver stem cells is still debated. In the present study, we used retroviral-mediated genetic labeling to investigate the fate of mature hepatocytes in rats after administration of diethylnitrosamine (DEN). Mature hepatocytes were genetically labeled by intravenous injection of retroviral vectors containing the Escherichia coli β-galactosidase gene coupled to a nuclear localization signal ( nls-LacZ) 1 day after partial hepatectomy. Liver biopsies performed after completion of hepatic regeneration showed that 18.3% of hepatocytes expressed the nls-LacZ transgene. Rats were then treated with DEN in drinking water for 12 weeks and sacrificed between 98 and 151 days after the onset of DEN administration. Clones of β-galactosidase positive cells were observed, half of which (53%) also expressed the placental form of glutathione- S-transferase (GSTp), a marker of preneoplastic cells. HCCs of various sizes expressing GSTp were present in all animals. Careful examination of 90 HCCs revealed that 16 (17.7%) also expressed nls-LacZ. This figure precisely matched the proportion of labeled hepatocytes before DEN treatment (18.3%). In conclusion, a random clonal origin of HCC from mature hepatocytes is seen in the DEN model of hepatocarcinogenesis. (H EPATOLOGY 2002;36:623-630.)