Dose-related induction of hepatic preneoplastic lesions by diethylnitrosamine in C57BL/6 mice

Glutathione and Selenium Supplementation Attenuates Liver Injury in Diethylnitrosamine-Induced Hepatocarcinogenic Mice by Enhancing Glutathione-Related Antioxidant Capacities

Excess oxidative stress and inadequate antioxidant capacities are critical features in the development of hepatocellular carcinoma. This study aimed to determine whether supplementation with glutathione (GSH) and/or selenium (Se), as antioxidants, attenuates diethylnitrosamine (DEN)-induced hepatocarcinogenesis in mice. C57BL/6J male mice were randomly assigned to control, DEN, DEN + GSH, DEN + Se, and DEN + GSH + Se groups for 20 weeks. Daily supplementation with GSH and/or Se commenced in the first experimental week and continued throughout the study. DEN was administered in weeks 2-9 and 16-19 of the experimental period. DEN administration induced significant pathological alterations of hepatic foci, evidenced by elevated levels of liver function, accompanied by high malondialdehyde (MDA) levels; low GSH levels; and glutathione peroxidase (GPx), glutathione reductase (GR), and glutathione S-transferase (GST) activities. Supplementation with GSH and Se significantly ameliorated liver pathological changes, reducing liver function and MDA levels while increasing GSH levels and GPx, GR, and GST activities. Notably, combined supplementation with GSH and Se more effectively increased the GSH/glutathione disulfide ratio and GPx activity than individual supplementation. Supplementation with GSH and Se attenuated liver injury in DEN-induced hepatocarcinogenic mice by enhancing GSH and its related antioxidant capacities, thereby mitigating oxidative damage.

Diethylnitrosamine-Induced Liver Tumorigenesis in Mice Under High-Hat High-Sucrose Diet: Stepwise High-Resolution Ultrasound Imaging and Histopathological Correlations

The hepatotoxic N-nitroso compound diethylnitrosamine (DEN) administered intraperitoneally (i.p.) induces liver neoplasms in rodents that reproducibly recapitulate some aspects of human hepatocarcinogenesis. In particular, DEN drives the stepwise formation of pre-neoplastic and neoplastic (benign or malignant) hepatocellular lesions reminiscent of the initiation-promotion-progression sequence typical of chemical carcinogenesis. In humans, the development of hepatocellular carcinoma (HCC) is also a multi-step process triggered by continuous hepatocellular injury, chronic inflammation, and compensatory hyperplasia that fuel the emergence of dysplastic liver lesions followed by the formation of early HCC. The DEN-induced liver tumorigenesis model represents a versatile preclinical tool that enables the study of many tumor development modifiers (genetic background, gene knockout or overexpression, diets, pollutants, or drugs) with a thorough follow-up of the multistage process on live animals by means of high-resolution imaging. Here, we provide a comprehensive protocol for the induction of hepatocellular neoplasms in wild-type C57BL/6J male mice following i.p. DEN injection (25 mg/kg) at 14 days of age and 36 weeks feeding of a high-fat high-sucrose (HFHS) diet. We emphasize the use of ultrasound liver imaging to follow tumor development and provide histopathological correlations. We also discuss the extrinsic and intrinsic factors known to modify the course of liver tumorigenesis in this model.

Loss of Krüppel-like factor-10 facilitates the development of chemical-induced liver cancer in mice

BACKGROUND

Krüppel-like factor 10 (KLF10) is involved in a positive feedback loop that regulates transforming growth factor β (TGFβ) signaling, and TGFβ plays an important role in the pathogenesis of liver disease. Here, we investigated whether KLF10 deletion affects the development of liver fibrosis and hepatocellular carcinoma (HCC).

METHODS

We induced KLF10 deletion in C57BL/6 mice. Liver fibrosis was induced by feeding a diet high in fat and sucrose (high-fat diet [HFD]), whereas HCC was produced by intraperitoneal administration of N-diethylnitrosamine (DEN). An in vitro experiment was performed to evaluate the role of KLF10 in the cancer microenvironment using Hep3B and LX2 cells. An immunohistochemical study of KLF10 expression was performed using human HCC samples from 60 patients who had undergone liver resection.

RESULTS

KLF10 deletion resulted in an increased DEN-induced HCC burden with significant upregulation of SMAD2, although loss of KLF10 did not alter HFD-induced liver fibrosis. DEN-treated mice with KLF10 deletion exhibited increased levels of mesenchymal markers (N-cadherin and SNAI2) and tumor metastasis markers (matrix metalloproteinases 2 and 9). KLF10 depletion in Hep3B and LX2 cells using siRNA was associated with increased invasiveness. Compared with co-culture of KLF10-preserved Hep3B cells and KLF10-intact LX2 cells, co-culture of KLF10-preserved Hep3B cells and KLF10-depleted LX2 cells resulted in significantly enhanced invasion. Low KLF10 expression in resected human HCC specimens was associated with poor survival.

CONCLUSION

The results of this study suggest that loss of KLF10 facilitates liver cancer development with alteration in TGFβ signaling.

Dyrk2 gene transfer suppresses hepatocarcinogenesis by promoting the degradation of Myc and Hras

Background & Aims

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide, and has a poor prognosis. However, the molecular mechanisms underlying hepatocarcinogenesis and progression remain unknown. In vitro gain- and loss-of-function analyses in cell lines and xenografts revealed that dual-specificity tyrosine-regulated kinase 2 (DYRK2) influences tumour growth in HCC.

Methods

To investigate the role of Dyrk2 during hepatocarcinogenesis, we developed liver-specific Dyrk2 conditional knockout mice and an in vivo gene delivery system with a hydrodynamic tail vein injection and the Sleeping Beauty transposon. The antitumour effects of Dyrk2 gene transfer were investigated in a murine autologous carcinogenesis model.

Results

Dyrk2 expression was reduced in tumours, and that its downregulation was induced before hepatocarcinogenesis. Dyrk2 gene transfer significantly suppressed carcinogenesis. It also suppresses Myc-induced de-differentiation and metabolic reprogramming, which favours proliferative, and malignant potential by altering gene profiles. Dyrk2 overexpression caused Myc and Hras degradation at the protein level rather than at the mRNA level, and this degradation mechanism was regulated by the proteasome. Immunohistochemical analyses revealed a negative correlation between DYRK2 expression and MYC and longer survival in patients with HCC with high-DYRK2 and low-MYC expressions.

Conclusions

Dyrk2 protects the liver from carcinogenesis by promoting Myc and Hras degradation. Our findings would pave the way for a novel therapeutic approach using DYRK2 gene transfer.

Impact and Implications

Hepatocellular carcinoma (HCC) is one of the most common cancers, with a poor prognosis. Hence, identifying molecules that can become promising targets for therapies is essential to improve mortality. No studies have clarified the association between DYRK2 and carcinogenesis, although DYRK2 is involved in tumour growth in various cancer cells. This is the first study to show that Dyrk2 expression decreases during hepatocarcinogenesis and that Dyrk2 gene transfer is an attractive approach with tumour suppressive activity against HCC by suppressing Myc-mediated de-differentiation and metabolic reprogramming that favours proliferative and malignant potential via Myc and Hras degradation.

Vitamin D ameliorates diethylnitrosamine-induced liver preneoplasia: A pivotal role of CYP3A4/CYP2E1 via DPP-4 enzyme inhibition

Growing evidence has indicated that vitamin D (Vit D) regulates cell proliferation and differentiation in cancer cells. Accordingly, the present study was conducted to investigate the possible beneficial effects of Vit D on diethylnitrosamine (DEN)-induced liver preneoplasia. The effect of Vit D on HepG2 cells was investigated using MTT assay. Additionally, liver preneoplasia was induced in Swiss male albino mice by giving overnight fasted animals 5 consecutive doses of DEN (75 mg/kg/week). Oral treatment with Vit D (200 IU/kg/day) was initiated either 2 weeks before DEN (first protocol) or 1 week after the first dose of DEN injection (second protocol). At the end of the experiment, tissue levels of GGT, DPP-4, TNF-α, IL-6, CYP2E1, and CYP3A4 were also estimated. Moreover, the histopathological study of liver tissue and immunohistochemical detection of GST-P, PCNA, and NF-κB were performed. Vit D exerted a significant cytotoxic effect on HepG2 cells via significantly increasing BAX, p53, and BAX/Bcl2 ratio, and significantly decreasing Bcl2 mRNA expression. In both in vivo protocols, Vit D was capable of normalizing relative liver weight, PCNA, altered hepatocellular foci, and ductular proliferation. Moreover, Vit D significantly reduced the DEN-induced elevation of AST, ALT, ALP, GGT, DDP-4, TNF-α, IL-6, CYP2E1, liver DNA damage, GST-P, NF-κB, nuclear hyperchromasia/pleomorphism, cholestasis, and inflammatory cell aggregates, but significantly increased CYP3A4 content. In conculsion, current results reflect the potential impact of Vit D in the management of early stages of liver cancer.

Limitations of Tamoxifen Application for In Vivo Genome Editing Using Cre/ERT2 System

Inducible Cre-dependent systems are frequently used to produce both conditional knockouts and transgenic mice with regulated expression of the gene of interest. Induction can be achieved by doxycycline-dependent transcription of the wild type gene or OH-tamoxifen-dependent nuclear translocation of the chimeric Cre/ER^T2 protein. However, both of these activation strategies have some limitations. We analyzed the efficiency of knockout in different tissues and found out that it correlates with the concentration of the hydroxytamoxifen and endoxifen-the active metabolites of tamoxifen-measured by LC-MS in these tissues. We also describe two cases of Cdk8^{floxed/floxed}/Rosa-Cre-ER^T2 mice tamoxifen-induced knockout limitations. In the first case, the standard scheme of tamoxifen administration does not lead to complete knockout formation in the brain or in the uterus. Tamoxifen metabolite measurements in multiple tissues were performed and it has been shown that low recombinase activity in the brain is due to the low levels of tamoxifen active metabolites. Increase of tamoxifen dosage (1.5 fold) and duration of activation (from 5 to 7 days) allowed us to significantly improve the knockout rate in the brain, but not in the uterus. In the second case, knockout induction during embryonic development was impossible due to the negative effect of tamoxifen on gestation. Although DNA editing in the embryos was achieved in some cases, the treatment led to different complications of the pregnancy in wild-type female mice. We propose to use doxycycline-induced Cre systems in such models.

Plasma and Liver Pharmacokinetics of the N-Acetylgalactosamine Short Interfering RNA JNJ-73763989 in Recombinant Adeno-Associated-Hepatitis B Virus-Infected Mice

JNJ-73763989 is an N-acetylgalactosamine conjugated short interfering RNA combination product consisting of two triggers in clinical development for chronic hepatitis B virus (HBV) infection treatment that induces a selective degradation of all HBV mRNA transcripts. Our aim is to characterize the plasma and liver pharmacokinetics (PK) of JNJ-73763989 after intravenous and subcutaneous administration in recombinant adeno-associated (rAAV) HBV infected mice. Forty-two male rAAV-HBV infected C57Bl/6 mice received JNJ-73763989 doses of 10 mg/kg i.v. or 1, 3 and 10 mg/kg s.c. Plasma and liver concentrations were analyzed simultaneously using nonlinear mixed-effects modeling with the NONMEM 7.4. A population PK model consisting of a two-compartment disposition model with transporter-mediated drug disposition, including internalization to the liver compartment, linear elimination from plasma and liver, and first-order absorption following subcutaneous administration, was suitable to describe both plasma and liver PK. After subcutaneous dosing, absolute bioavailability was complete and flip-flop kinetics were observed. JNJ-73763989 distributes from plasma to liver via transporter-mediated liver internalization in less than 24 hours, with sustained (>42 days) liver exposure. The saturation of transporter-mediated liver internalization was hypothesized to be due to asialoglycoprotein receptor saturation. Increasing the dose decreased the relative liver uptake efficiency in mice for intravenously and, to a lesser extent, subcutaneously administered JNJ-73763989. Lower dose levels administered subcutaneously in mice can maximize the proportion of the dose reaching the liver. SIGNIFICANCE STATEMENT: Pharmacokinetic modeling of JNJ-73763989 liver and plasma concentration-time data in mice indicated that the proportion of JNJ-73763989 reaching the liver may be increased by administering lower subcutaneous doses compared to higher intravenous doses. Model-based simulations can be applied to optimize the dose and regimen combination.

In Vivo and In Vitro Models of Hepatocellular Carcinoma: Current Strategies for Translational Modeling

Hepatocellular carcinoma (HCC) is the sixth most common cancer worldwide and the third leading cause of cancer-related death globally. HCC is a complex multistep disease and usually emerges in the setting of chronic liver diseases. The molecular pathogenesis of HCC varies according to the etiology, mainly caused by chronic hepatitis B and C virus infections, chronic alcohol consumption, aflatoxin-contaminated food, and non-alcoholic fatty liver disease associated with metabolic syndrome or diabetes mellitus. The establishment of HCC models has become essential for both basic and translational research to improve our understanding of the pathophysiology and unravel new molecular drivers of this disease. The ideal model should recapitulate key events observed during hepatocarcinogenesis and HCC progression in view of establishing effective diagnostic and therapeutic strategies to be translated into clinical practice. Despite considerable efforts currently devoted to liver cancer research, only a few anti-HCC drugs are available, and patient prognosis and survival are still poor. The present paper provides a state-of-the-art overview of in vivo and in vitro models used for translational modeling of HCC with a specific focus on their key molecular hallmarks.

The effect of capsaicin and diethylnitrosamine on mouse nephrotoxicity, hepatotoxicity and hepatocarcinogenesis

Diethylnitrosamine is well known for its toxic and carcinogenic properties affecting mainly liver and kidneys. Capsaicin has been proven in previous years as a promising protective agent against many health problems affecting modern people. In this study we used diethylnitrosamine induced mouse experimental model of liver and kidney damage to assess the potential chemopreventive effect of capsaicin in vivo. Fifty female ICR mice were randomly divided into five groups intraperitoneally administered 1% ethanol solution in controls, capsaicin to assess its toxicity, diethylnitrosamine alone, and diethylnitrosamine and capsaicin in combination in different manners in two groups. After 14 weeks all mice were sacrificed, complete necropsy was performed and liver and kidneys were used for further examination. Slides of both organs stained with haematoxylin and eosin were histologically evaluated and immunohistochemical detection of proliferating cell nuclear antigen and glutamine synthetase in the liver tissue was performed. Histological evaluation of the liver and kidneys revealed toxic damage of diethylnitrosamine treated animals, whereas mice that received the combination of the substances showed milder lesions. Proliferating cell nuclear antigen expression was lower in diethylnitrosamine treated animals compared to the control and capsaicin groups, pointing to a disruption of the proliferative activity of hepatocytes in the juvenile liver. Glutamine synthetase expression did not differ between the groups, indicating that no tumours were induced by any of the substances used in our study. In conclusion, our experiment demonstrated the toxic properties of diethylnitrosamine in mice liver and kidneys, with the promising beneficial effect of capsaicin.

Risk Factors, Pathogenesis, and Strategies for Hepatocellular Carcinoma Prevention: Emphasis on Secondary Prevention and Its Translational Challenges

Hepatocellular carcinoma (HCC) is a leading cause of cancer-associated mortality globally. Given the limited therapeutic efficacy in advanced HCC, prevention of HCC carcinogenesis could serve as an effective strategy. Patients with chronic fibrosis due to viral or metabolic etiologies are at a high risk of developing HCC. Primary prevention seeks to eliminate cancer predisposing risk factors while tertiary prevention aims to prevent HCC recurrence. Secondary prevention targets patients with baseline chronic liver disease. Various epidemiological and experimental studies have identified candidates for secondary prevention-both etiology-specific and generic prevention strategies-including statins, aspirin, and anti-diabetic drugs. The introduction of multi-cell based omics analysis along with better characterization of the hepatic microenvironment will further facilitate the identification of targets for prevention. In this review, we will summarize HCC risk factors, pathogenesis, and discuss strategies of HCC prevention. We will focus on secondary prevention and also discuss current challenges in translating experimental work into clinical practice.

Effect of protocatechuic acid-layered double hydroxide nanoparticles on diethylnitrosamine/phenobarbital-induced hepatocellular carcinoma in mice

Researchers investigating cancer chemotherapy and management continue to search for agents that selectively kill malignant cells and leave healthy neighboring cells intact. Natural products provide relevant resources for anti-cancer drug discovery. However, the physicochemical properties of these compounds limit their efficient uptake and bioavailability. We introduced a nanocarrier system, namely, zinc-aluminum-layered double hydroxide (ZnAl-LDH) intercalated with protocatechuic acid. In this study, the efficacy and toxicity of protocatechuic acid intercalated in zinc aluminum-layered double hydroxide nanoparticles (PCA-ZnAl) against diethylnitrosamine/phenobarbital (DEN/PB)-induced hepatocellular carcinoma (HCC) in BALB/c mice was evaluated. HCC in male mice was induced by a single-dose intraperitoneal administration of DEN and was promoted by the introduction of PB via drinking water for 12 weeks. HCC induction was confirmed after the DEN/PB introduction period by measurement of the elevated level of serum α-feto protein (AFP). The results showed that the level of α-fetoprotein was significantly reduced in PCA-ZnAl (350±43.90 ng/mL), doxorubicin (DOX) (290±20.52 ng/mL) and ZnAl-LDH (390±19.65 ng/mL) treated animals compared to HCC mice treated with normal saline (580.4± 52.04 ng/mL). Superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) levels were significantly increased, whereas the level of lipid peroxidation was significantly decreased in HCC mice treated with DOX, PCA-ZnAl and ZnAl-LDH compared with those in HCC mice treated with saline. Restoration of hepatocyte morphology was observed following treatment that was comparable to that in the normal control group. Deterioration of hepatic cells and a significant increase of aspartate transaminase (AST), alanine transaminase (ALT), and alkaline phosphatase (ALP) were observed in the cancer-induced untreated group compared with that in the groups treated with nanoparticles. The histopathological features of the liver obtained from PCA-ZnAl-treated mice showed a uniform size with a similar distribution of the nuclear-cytoplasmic ratio and nucleus centrally located in the cytoplasm, similar to the normal liver cells. The results underscored the potential of PCA-ZnAl for the treatment of hepatocellular carcinoma.

Fibrosis-associated hepatocarcinogenesis revisited: Establishing standard medium-term chemically-induced male and female models

Hepatocellular carcinoma causes ~10% of all cancer-related deaths worldwide, usually emerging in a background of liver fibrosis/cirrhosis (70%-90% of cases). Chemically-induced mouse models for fibrosis-associated hepatocarcinogenesis are widely-applied, resembling the corresponding human disease. Nonetheless, a long time is necessary for the development of preneoplastic/neoplastic lesions. Thus, we proposed an early fibrosis-associated hepatocarcinogenesis model for male and female mice separately, focusing on reducing the experimental time for preneoplastic/neoplastic lesions development and establishing standard models for both sexes. Then, two-week old susceptible C3H/HeJ male and female mice (n = 8 animals/sex/group) received a single dose of diethylnitrosamine (DEN, 10 or 50 mg/Kg). During 2 months, mice received 3 weekly doses of carbon tetrachloride (CCl4, 10% corn oil solution, 0.25 to 1.50 μL/g b.wt.) and they were euthanized at week 17. DEN/CCl4 protocols for males and females displayed clear liver fibrosis, featuring collagen accumulation and hepatic stellate cell activation (α-SMA). In addition, liver from males displayed increased CD68+ macrophage number, COX-2 protein expression and IL-6 levels. The DEN/CCl4 models in both sexes impaired antioxidant defense as well as enhanced hepatocyte proliferation and apoptosis. Moreover, DEN/CCl4-treated male and female developed multiple preneoplastic altered hepatocyte foci and hepatocellular adenomas. As expected, the models showed clear male bias. Therefore, we established standard and suitable fibrosis-associated hepatocarcinogenesis models for male and female mice, shortening the experimental time for the development of hepatocellular preneoplastic/neoplastic lesions in comparison to other classical models.

Chemopreventive and antitumor effects of benzyl isothiocynate on HCC models: A possible role of HGF /pAkt/ STAT3 axis and VEGF

BACKGROUND

Benzyl isothiocyanate (BITC) is a member of the isothiocyanate compounds that found in cruciferous vegetables. BITC has a potential anticancer effect in different types of tumors. Few studies referred to the antineoplastic effect of BITC against HCC. The mechanism of BITC concerning retardation of HCC progression is incompletely understood.

AIM OF THE WORK

This study evaluated the role of HGF, pAkt and STAT3 in BITC induced HCC growth retardation.

METHOD

HCC was induced in mice using diethylnitrosamine (DEN) 75 mg/kg once a week for 4 weeks. BITC 10 and 20 mg/kg was given to mice orally each day for 10 weeks. The HCC cell lines HepG2 and Huh-7 were also used to evaluate the effect of BITC on tumor cells behavior. Immunoassay was used to detect expressions of caspase-3 activity, VEGF, MMP-2, TNF-α, HGF and pAkt. STAT3 expression was detected in liver tissues using immunohistochemical staining.

RESULTS

BITC has a potential role in suppressing hepatic precancerous lesion progression in mice. The drug increased caspase-3 activity in tumor cells and inhibited the angiogenic marker VEGF. It also decreased the metastatic marker MMP-2. This anticancer effect of BITC was observed in DEN treated mice as well as in hepatoma cell lines. The reported antineoplastic activity was correlated with downregulation of HGF and its downstream molecules pAkt and STAT3.

CONCLUSION

The effect of BITC on HGF /pAkt/ STAT3 axis has a potential role in both chemopreventive and chemotherapeutic effects of BITC.

Diethylnitrosamine Increases Proliferation in Early Stages of Hepatic Carcinogenesis in Insulin-Treated Type 1 Diabetic Mice

Diethylnitrosamine (DEN) induces hepatocarcinogenesis, increasing mitotic hepatocytes and leading to chronic inflammation. In addition, type 1 diabetes mellitus (T1DM) is also characterized by a proinflammatory state and by requiring insulin exogenous treatment. Given the association of diabetes, insulin treatment, and cell proliferation, our specific goal was to determine whether the liver in the diabetic state presents a greater response to DEN-induced cell cycle alteration, which is essential for the malignant transformation. Male C57BL/6 mice (four-week-old) were divided into 4 groups: C, C + DEN, T1DM, and T1DM + DEN. Mice were euthanized ten weeks after DEN injection. DEN per se produced an increase in liver lipid peroxidation levels. Besides, in T1DM + DEN, we found a greater increase in the proliferation index, in comparison with C + DEN. These results are in agreement with the increased expression observed in cell cycle progression markers: cyclin D1 and E1. In addition, a proapoptotic factor, such as activated caspase-3, evidenced a decrease in T1DM + DEN, while the Vascular Endothelial Growth Factor (VEGF) and the protooncogene p53 showed a higher increase with respect to C + DEN. Overall, the results allow us to highlight a major DEN response in T1DM, which may explain in part the greater predisposition to the development of hepatocarcinoma (HCC) during the diabetic state.

Diethylnitrosamine induces lung adenocarcinoma in FVB/N mouse

Background

Diethylnitrosamine is a well known carcinogen that induces cancers of various organs in mice and rats. Using FVB/N mouse strain, here we show that diethylnitrosamine induces primarily lung adenocarcinomas with modest tumor development in the liver, offering a new model to study chemical carcinogenesis in the lung.

Methods

Animals were exposed to a single high dose of diethylnitrosamine, and more than 70% of the mice developed lung cancer. To obtain a new transplantable tumor line, pieces of primary tumors were inoculated and maintained subcutaneously in the same mouse strain. We used immunohistochemistry to characterize the tumor for main lung adenocarcinoma markers. We searched for mutations in KRAS exon 2 and EGFR exon 19, 21 with Sanger sequencing. We also compared the normal lung tissue with the diethylnitrosamine induced primary adenocarcinoma, and with the subcutaneously maintained adenocarcinoma using Western blot technique for main cell cycle markers and to identify the main pathways.

Results

Primary and subcutaneous tumors express cytokeratin-7 and thyroid transcription factor-1, markers characteristic to lung adenocarcinoma. In addition, no mutations were found in the hot spot regions of KRAS and EGFR genes. We found high mTOR activation, but the level of p-Akt Ser473 and p-Akt Thr308 decreased in the tumorous samples.

Conclusions

We established a new lung adenocarcinoma model using FVB/N mouse strain and diethylnitrosamine. We believe that this new model system would be highly useful in lung cancer research.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4068-4) contains supplementary material, which is available to authorized users.

Regulatory Forum Opinion Piece: Review-Toxicological Pathology Profile and Regulatory Expectations for Nonclinical Development of Insulins and Insulin Analogues

The toxicological profile of insulins is exclusively due to exaggerated pharmacology resulting in hypoglycemic findings. Insulin analogues displaying modifications and aimed at improving pharmacokinetics do not induce different toxicity. The main target is the brain displaying neuronal necrosis. Wallerian degeneration of nerves occurs rarely after severe hypoglycemia. These findings are of potential human relevance; nevertheless, these changes are induced in normoglycemic animals whereas diabetic patients suffer from hyperglycemia. Therefore, it is usually not difficult to achieve a therapeutic window for subsequent use in patients. Based upon this and in the absence of classical toxicity, there has been no scientific need for diabetic animal models. A greater challenge is the mitogenicity already inherent with regular insulin. Thus, the focus for preclinical safety evaluation of analogues is to demonstrate that modifications in regular insulin do not result in enhanced mitogenicity. The approaches used to assess the mitogenic potential of insulin analogues have changed over time driven by scientific progression and changes within the regulatory environment. Therefore, in vitro and in vivo evaluation of cell proliferation has become common practice, and to date there has been no evidence that the mitogenic potential of insulin analogues may be increased compared to regular insulin.

Inhibition of hepatocellular carcinoma growth by blockade of glycosphingolipid synthesis

Hepatocellular carcinoma (HCC) is one of the most frequent cancers. In vitro studies suggest that growth and response to therapy of human carcinomas may depend on glycosphingolipid (GSL) expression. Glucosylceramide synthase (GCS), encoded by the gene Ugcg, is the basic enzyme required for the synthesis of GSLs. Gene array analysis implied that Ugcg is significantly overexpressed in human HCC as compared to non-tumorous liver tissue. Therefore we have investigated whether tumor - genesis and - growth is altered in the absence of GSLs. An endogenous liver cancer model has been initiated by application of diethylnitrosamine in mice lacking Ugcg specifically in hepatocytes. We have now shown that hepatocellular tumor initiation and growth in mice is significantly inhibited by hepatic GSL deficiency in vivo. Neither the expression of cell cycle proteins, such as cyclins and pathways such as the MAP-kinase/Erk pathway nor the mTOR/Akt pathway as well as the number of liver infiltrating macrophages and T cells were essentially changed in tumors lacking GSLs. Significantly elevated bi-nucleation of atypical hepatocytes, a feature for impaired cytokinesis, was detected in tumors of mice lacking liver-specific GSLs. A reduction of proliferation and restricted growth of tumor microspheres due to delayed, GSL-dependent cytokinesis, analogous to the histopathologic phenotype in vivo could be demonstrated in vitro. GSL synthesis inhibition may thus constitute a potential therapeutic target for hepatocellular carcinoma.

Nicotinamide nucleotide transhydrogenase (NNT) deficiency dysregulates mitochondrial retrograde signaling and impedes proliferation

To study the physiological roles of NADH and NADPH homeostasis in cancer, we studied the effect of NNT knockdown on physiology of SK-Hep1 cells. NNT knockdown cells show limited abilities to maintain NAD⁺ and NADPH levels and have reduced proliferation and tumorigenicity. There is an increased dependence of energy production on oxidative phosphorylation. Studies with stable isotope tracers have revealed that under the new steady-state metabolic condition, the fluxes of TCA and glycolysis decrease while that of reductive carboxylation increases. Increased [α-ketoglutarate]/[succinate] ratio in NNT-deficient cells results in decrease in HIF-1α level and expression of HIF-1α regulated genes. Reduction in NADPH level leads to repression of HDAC1 activity and an increase in p53 acetylation. These findings suggest that NNT is essential to homeostasis of NADH and NADPH pools, anomalies of which affect HIF-1α- and HDAC1-dependent pathways, and hence retrograde response of mitochondria.

Therapeutic role of a synthesized calcium phosphate nanocomposite material on hepatocarcinogenesis in rats

Nanotechnology research is booming worldwide, and the general belief is that medical and biological applications will form the greatest sector of expansion over the next decade. With this in mind, this study was designed to evaluate the therapeutic effects of a synthesized tricalcium phosphate nanocomposite material (nano-TCP) on hepatocarcinoma in a rat model, as initiated with diethylnitrosamine (DEN) and promoted with phenobarbital (PB). Hepatocarcinoma was induced with intraperitoneal injections of DEN (50 mg·(kg body mass)(-1)) 3 times a week for 2 weeks. Three weeks after the last dose of DEN, the rats received PB (0.05 %, w/v) in their drinking water for a further 6 weeks. Nano-TCP (100 mg·(kg body mass)(-1)) was administered intraperitoneally 3 times per week to rats with HCC. At the end of the experimental period, liver samples were collected from all animals for biochemical and histopathological analysis. The degree of DNA fragmentation was analyzed, in addition to immune status, by measuring the levels of interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α), and interleukin-2 (IL-2). The activities of the most important free-radical scavengers of the antioxidant defense system as well as malondialdehyde (MDA) content and liver enzymes were measured. The levels of hepatic heat shock protein-70 (HSP-70), caspase-3, and metalloproteinase-9 were also measured as markers for inflammation and apoptosis. Histopathological examination of liver tissue was performed. The results revealed the potent efficacy of nano-TCP in repairing the fragmented DNA and ameliorating most of the investigated parameters by significant elevation in the levels of hepatic alanine aminotransferase (ALT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) activities. On the other hand, there was a significant decrease in hepatic gamma-glutamyl transpeptidase (γ-GT), MDA, IL-2, IFN-γ, TNF-α, matrix metalloproteinase-9 (MMP-9), HSP-70, and caspase-3 levels upon treatment. The findings form histopathological examination of the liver tissues agreed with the biochemical results and confirmed the difference between the control and treatment groups. In conclusion, nano-TCP succeeded in treating hepatocarcinoma efficiently, and presents a new hope for patients to get safe, fast, and effective treatment.

Altered methylation of specific DNA loci in the liver of Bhmt-null mice results in repression of Iqgap2 and F2rl2 and is associated with development of preneoplastic foci

Folate B₁₂-dependent remethylation of homocysteine is important, but less is understood about the importance of the alternative betaine-dependent methylation pathway-catalyzed by betaine-homocysteine methyltransferase (BHMT)-for establishing and maintaining adequate DNA methylation across the genome. We studied C57Bl/6J Bhmt (betaine-homocysteine methyltransferase)-null mice at age 4, 12, 24, and 52 wk (N = 8) and observed elevation of S-adenosylhomocysteine concentrations and development of preneoplastic foci in the liver (increased placental glutathione S-transferase and cytokeratin 8-18 activity; starting at 12 wk). At 4 wk, we identified 63 differentially methylated CpGs (DMCs; false discovery rate < 5%) proximal to 81 genes (across 14 chromosomes), of which 18 were differentially expressed. Of these DMCs, 52% were located in one 15.5-Mb locus on chromosome 13, which encompassed the Bhmt gene and defined a potentially sensitive region with mostly decreased methylation. Analyzing Hybrid Mouse Diversity Panel data, which consisted of 100 inbred strains of mice, we identified 97 DMCs that were affected by Bhmt genetic variation in the same region, with 7 overlapping those found in Bhmt-null mice (P < 0.001). At all time points, we found a hypomethylated region mapping to Iqgap2 (IQ motif-containing GTPase activating protein 2) and F2rl2 (proteinase-activated receptor-3), 2 genes that were also silenced and underexpressed, respectively.-Lupu, D. S., Orozco, L. D., Wang, Y., Cullen, J. M., Pellegrini, M., Zeisel, S. H. Altered methylation of specific DNA loci in the liver of Bhmt-null mice results in repression of Iqgap2 and F2rl2 and is associated with development of preneoplastic foci.

Photothermal therapy mediated by gum Arabic-conjugated gold nanoparticles suppresses liver preneoplastic lesions in mice

This study validates the utility of Gum Arabic-conjugated gold nanoparticles (GA-AuNPs) and laser to induce photothermal inhibition of hepatocarcinogenesis, via employing a diethylnitrosamine (DEN)-mediated hepatocellular carcinoma model. This work included both of in vitro and in vivo studies; to investigate the GA-AuNPs cytotoxicity and phototoxicity in hepatic cell line; to delineate the GA-AuNPs therapeutic efficiency in DEN-induced preneoplastic lesions (PNLs) in the liver of Balb-C mice. The therapeutic effects of GA-AuNPs on the mediators of apoptosis, inflammation, and tumor initiation, as well as the histopathological changes in preneoplastic liver have been investigated. Our results infer that GA-AuNPs in combination with laser irradiation led to a significant reduction in the cell viability and in histone deacetylase activity in hepatocarcinoma HepG2 cells. In chemically-induced PNLs mice model our results have demonstrated that GA-AuNPs, with or without laser irradiation, induced cancer cell apoptosis through the activation of death receptors DR5 and caspase-3 and inhibited both of the PNLs incidence and the initiation marker (placental glutathione S-transferase; GST-P). The laser-stimulated GA-AuNPs significantly reduced the tumor necrosis factor-α levels. In summary, GA-AuNPs with laser treatment inhibited liver PNLs via the induction of the extrinsic apoptosis pathway and the inhibition of inflammation.

Diethylnitrosamine (DEN)-induced carcinogenic liver injury in mice

The toxic properties of various nitrosamines in animals and humans are well established. The parenteral or oral administration of the smallest quantities of diethylnitrosamine (DEN) or dimethylnitrosamine (DMN) results in severe liver damage. Most prominent are intense neutrophilic infiltration, extensive centrilobular haemorrhagic necrosis, bile duct proliferation, fibrosis, and bridging necrosis that ends in hepatocarcinogenesis. Due to the robustness of the induced hepatic alterations, the application of DEN in rodents has become an attractive experimental model for studies aimed at understanding the pathogenetic alterations underlying the formation of liver cancer, which represents one of the most common malignancies in humans worldwide. However, several studies have shown that the hepatocarcinogenic effects of nitrosamines might vary with the genetic background of the animals, their sex, their age, and other factors that might impact the outcome of experimentation. We present general guidelines for working with DEN, and a detailed protocol that allows the establishment of highly reproducible liver cancer in mice. The outcome of liver injury after the application of DEN in mice, as estimated by the formation of cirrhosis and cancer, appears to be a suitable animal model for the analysis of some aspects and processes that promote the pathogenesis of hepatocellular carcinoma in humans.

Hepatotoxicity induced by neonatal exposure to diethylstilbestrol is maintained throughout adulthood via the nuclear receptor SHP

BACKGROUND

Liver physiology is sensitive to estrogens, which suggests that the liver might be a target of estrogenic endocrine disrupters (EED). However, the long-term consequences of neonatal exposure to EED on liver physiology have rarely been studied. The nuclear receptor small heterodimer partner (SHP) mediates the deleterious effects of neonatal exposure to diethylstilbestrol (DES) on male fertility.

OBJECTIVES

As SHP is involved in liver homeostasis, we aimed to determine whether neonatal estrogenic exposure also affected adult liver physiology through SHP. Male mouse pups were exposed to DES in the first 5 days of life.

RESULTS

DES exposure leads to alterations in the postnatal bile acid (BA) synthesis pathway. Neonatal DES-exposure affected adult liver BA metabolism and subsequently triglyceride (TG) homeostasis. The wild-type males neonatally exposed to DES exhibited increased liver weight and altered liver histology in the adult age. The use of deficient male mice revealed that SHP mediates the deleterious effects of DES treatment. These long-term effects of DES were associated with differently timed alterations in the expression of epigenetic factors.

CONCLUSIONS

However, the molecular mechanisms by which neonatal exposure persist to affect the adult liver physiology remain to be defined. In conclusion, we demonstrate that neonatal DES exposure alters adult hepatic physiology in an SHP-dependent manner.

Cytokeratin 7/19 expression in N-diethylnitrosamine-induced mouse hepatocellular lesions: implications for histogenesis

Hepatocellular carcinoma (HCC) is a common malignancy with poor clinical outcome, whose histogenesis is the subject of intense debate. Specifically, expression of cytokeratins (CKs) 7 and 19, associated with aggressive biological behaviour, is proposed to reflect a possible progenitor cell origin or tumour dedifferentiation towards a primitive phenotype. This work addresses that problem by studying CKs 7 and 19 expression in N-diethylnitrosamine (DEN)-induced mouse HCCs. ICR mice were divided into six DEN-exposed and six matched control groups. Samples were taken from each group at consecutive time points. Hyperplastic foci (13 lesions) occurred at 29-40 weeks (groups 8, 10 and 12) with diffuse dysplastic areas (19 lesions) and with one hepatocellular adenoma (HCA) (at 29 weeks). HCCs (4 lesions) were observed 40 weeks after the first DEN administration (group 12). CKs 7 and 19 showed identical expression patterns and located to large, mature hepatocytes, isolated or in small clusters. Hyperplastic foci and the single HCA were consistently negative for both markers, while dysplastic areas and HCCs were positive. These results support the hypothesis that CKs 7 and 19 expression in hepatocellular malignancies results from a dedifferentiation process rather than from a possible progenitor cell origin.

Biochemical/metabolic changes associated with hepatocellular carcinoma development in mice

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related mortality after lung and stomach cancers. This work was undertaken to investigate some of the biochemical mediators/pathways associated with or implicated in the pathogenesis of HCC. Male albino mice were classified into two groups: normal control group and HCC group. Early stage HCC was induced by injection of diethylnitrosamine (DEN) i.p. 200 mg/kg as a single dose, and after 2 weeks, the mice were given i.p. injection of thioacetamide (TAA) 100 mg/kg twice per week for 4 weeks. Mice were left for further 2 weeks without any treatment, after which, mice were sacrificed; blood and liver samples were collected. Serum was used for determination of activities of glucose-6-phosphate dehydrogenase (G6PDH) and aldolase as well as levels of insulin-like growth factor-1 (IGF-1) and epithelial cadherin (E-cadherin). One portion of the liver was used for histopathological examination and immunohistochemical staining of the tumor suppressor p53 protein. Another portion of the liver was used for determination of citrate synthase activity. Induction of HCC in mice resulted in significant increase in G6PDH and aldolase activities, and E-cadherin level, but significant decrease in IGF-1. HCC mice group showed moderate expression of p53 protein. These results suggest that the molecular pathogenesis of HCC in mice involves reduction of serum level of IGF-1 and increased serum level of E-cadherin accompanied by dysregulation of p53 protein expression. HCC was also associated with reprogrammed metabolic profile shifted toward increased glycolysis and lipogenesis.

Brain bioavailability of human intravenous immunoglobulin and its transport through the murine blood-brain barrier

Intravenous immunoglobulin (IVIg) is currently evaluated in clinical trials for the treatment of various disorders of the central nervous system. To assess its capacity to reach central therapeutic targets, the brain bioavailability of IVIg must be determined. We thus quantified the passage of IVIg through the blood-brain barrier (BBB) of C57Bl/6 mice using complementary quantitative and qualitative methodologies. As determined by enzyme-linked immunosorbent assay, a small proportion of systemically injected IVIg was detected in the brain of mice (0.009±0.001% of injected dose in the cortex) whereas immunostaining revealed localization mainly within microvessels and less frequently in neurons. Pharmacokinetic analyses evidenced a low elimination rate constant (0.0053  per hour) in the cortex, consistent with accumulation within cerebral tissue. In situ cerebral perfusion experiments revealed that a fraction of IVIg crossed the BBB without causing leakage. A dose-dependent decrease of brain uptake was consistent with a saturable blood-to-brain transport mechanism. Finally, brain uptake of IVIg after a subchronic treatment was similar in the 3xTg-AD mouse model of Alzheimer disease compared with nontransgenic controls. In summary, our results provide evidence of BBB passage and bioavailability of IVIg into the brain in the absence of BBB leakage and in sufficient concentration to interact with the therapeutic targets.

Hepatic loss of miR-122 predisposes mice to hepatobiliary cyst and hepatocellular carcinoma upon diethylnitrosamine exposure

Loss of miR-122 causes chronic steatohepatitis and spontaneous hepatocellular carcinoma. However, the consequence of miR-122 deficiency on genotoxic stress-induced liver pathogenesis is poorly understood. Here, we investigated the impact of miR-122 depletion on liver pathobiology by treating liver-specific miR-122 knockout (LKO) mice with the hepatocarcinogen diethylnitrosamine (DEN). At 25 weeks post-DEN injection, all LKO mice developed CK-19-positive hepatobiliary cysts, which correlated with DEN-induced transcriptional activation of Cdc25a mediated through E2f1. Additionally, LKO livers were more fibrotic and vascular, and developed larger microscopic tumors, possibly due to elevation of the Axl oncogene, a receptor tyrosine kinase as a novel target of miR-122, and several protumorigenic miR-122 targets. At 35 weeks following DEN exposure, LKO mice exhibited a higher incidence of macroscopic liver tumors (71%) and cysts (86%) compared to a 21.4% and 0% incidence of tumors and cysts, respectively, in control mice. The tumors in LKO mice were bigger (ninefold, P = 0.015) and predominantly hepatocellular carcinoma, whereas control mice mostly developed hepatocellular adenoma. DEN treatment also reduced survival of LKO mice compared to control mice (P = 0.03). Interestingly, induction of oxidative stress and proinflammatory cytokines in LKO liver shortly after DEN exposure indicates predisposition of a pro-tumorigenic microenvironment. Collectively, miR-122 depletion facilitates cystogenesis and hepatocarcinogenesis in mice on DEN challenge by up-regulating several genes involved in proliferation, growth factor signaling, neovascularization, and metastasis.

Definition of diethylnitrosamine-induced rat hepatic precancerous lesions with atypia index

AIM: To define diethylnitrosamine-induced hepatic precancerous lesions with atypia index in rats.

METHODS: After normalization of the body weight, 100 male Wistar rats were equally and randomly divided into five groups and were intraperitoneally injected with different doses of diethylnitrosamine in normal saline (0, 25, 50, 75, 100 mg/kg) twice weekly. The rats in each group were further divided into 10 subgroups with end-points ranging from d00 to d126 with an interval of 14 days. Liver samples were fixed, sectioned, and stained with hematoxylin and eosin. After being evaluated pathologically, the volume ratios of portal triad (R₁), hepatic cord (R₂) and hepatic nucleus (R₃) were obtained under an Olympus microscope with 10-, 20-, and 40-amplification, respectively, by use of Image-Pro Plus software. Hepatic mitotic figures were counted under high magnification. The atypia index of hepatocytes was calculated as the volume ratio of nucleus to cytoplasm in precancerous lesions using the formula [(1-R₁)^-1∙(R₂)^-1∙(R₃)]. By using Graph Pad Prism version 4 for Windows, the half effective durations and the area under curve of the atypia indexes were regressed in Sigmoidal time-response (variable slope) from the logarithm of end-point hours [11.4 + Time (d) ×24 h/d] for each of 5 doses, so did the half effective doses of the area under curves from the logarithm of dosages [10 + Dose (mg/kg) ×1000 (μg/kg)]. The atypia indexes were regressed linearly with the mitotic counts to confirm their specificity in predicting hepatic carcinogenesis.

RESULTS: From the atypia index of hepatocytes (corrected volume ratio of nucleus to cytoplasm), the half effective durations of diethylnitrosamine at 0, 25, 50, 75, and 100 mg/kg to induce hepatic precancerous lesions were 70 347, 1 734, 1 536, 1 530 and 1 183 h, respectively. The areas under curves were 0.0064, 0.0084, 0.0123, 0.0165 and 0.0167 [(atypia index) × log(h)], respectively. From the area under curve, the half effective dose of diethylnitrosamine to induce hepatic precancerous lesions was 48.225 mg/kg. The atypia indexes in rats treated with 50 mg/kg diethylnitrosamine correlated positively with mitotic counts in hepatic precancerous lesions (y = 0.0023x-0.0056, r = 0.9217, n = 10, P < 0.01).

CONCLUSION: The atypia index might be used to define hepatic precancerous lesions. A rat model of hepatic precancerous lesions could be replicated by intraperitoneal injection of diethylnitrosamine at a dose of 48.225 mg/kg twice a week for 9 wk. The specificity of the model to predict hepatic carcinogenesis can be confirmed with mitotic counts in hepatic precancerous lesions.

A multi-mineral natural product inhibits liver tumor formation in C57BL/6 mice

C57BL/6 mice were maintained for up to 18 months on high-fat and low-fat diets with or without a multi-mineral supplement derived from the skeletal remains of the red marine algae Lithothamnion calcareum. Numerous grossly observable liver masses were visible in animals on the "western-style" high-fat diet sacrificed at 12 and 18 months. The majority of the masses were in male mice (20 out of 100 males versus 3 out of 100 females; p = 0.0002). There were more liver masses in animals on the high-fat diet than on the low-fat diet (15 out of 50 on high-fat versus 5 out of 50 on low-fat; p = 0.0254). The multi-mineral supplement reduced the number of liver masses in mice on both diets (3 out of 25 male mice in the low-fat diet group without the supplement versus 1 out of 25 mice with supplement; 12 of 25 male mice in the high-fat diet group without the supplement versus 3 of 25 mice with supplement [p = 0.0129]). Histological evaluation revealed a total of 17 neoplastic lesions (9 adenomas and 8 hepatocellular carcinomas), and 18 pre-neoplastic lesions. Out of eight hepatocellular carcinomas, seven were found in unsupplemented diet groups. Steatosis was widely observed in livers with and without grossly observable masses, but the multi-mineral supplement had no effect on the incidence of steatosis or its severity. Taken together, these findings suggest that a multi-mineral-rich natural product can protect mice against neoplastic and pre-neoplastic proliferative liver lesions that may develop in the face of steatosis.