Chemoprevention of spontaneous development of hepatocellular carcinomas in fatty liver Shionogi mice by a cyclooxygenase-2 inhibitor

Insight into non-nucleoside triazole-based systems as viral polymerases inhibitors

Viruses have been recognized as the etiological agents responsible for many pathological conditions ranging from asymptomatic infections to serious diseases, even leading to death. For this reason, many efforts have been made to identify selective viral targets with the aim of developing efficient therapeutic strategies, devoid of drug-resistance issues. Considering their crucial role in the viral life cycle, polymerases are very attractive targets. Among the classes of compounds explored as viral polymerases inhibitors, here we present an overview of non-nucleoside triazole-based compounds identified in the last fifteen years. Furthermore, the structure-activity relationships (SAR) of the different chemical entities are described in order to highlight the key chemical features required for the development of effective antiviral agents.

MicroRNA-Based Prophylaxis in a Mouse Model of Cirrhosis and Liver Cancer

Most hepatocellular carcinomas (HCCs) arise in the context of chronic liver disease and/or cirrhosis. Thus, chemoprevention in individuals at risk represents an important but yet unproven approach. In this study, we investigated the ability of microRNA (miRNA)-based molecules to prevent liver cancer development in a cirrhotic model. To this end, we developed a mouse model able to recapitulate the natural progression from fibrosis to HCC, and then we tested the prophylactic activity of an miRNA-based approach in the model. The experiments were carried out in the TG221 transgenic mouse, characterized by the overexpression of miR-221 in the liver and predisposed to the development of liver tumors. TG221 as well as wild-type mice were exposed to the hepatotoxin carbon tetrachloride (CCl4) to induce chronic liver damage. All mice developed liver cirrhosis, but only TG221 mice developed nodular lesions in 100% of cases within 6 months of age. The spectrum of lesions ranged from dysplastic foci to carcinomas. To investigate miRNA-based prophylactic approaches, anti-miR-221 oligonucleotides or miR-199a-3p mimics were administered to TG221 CCl4-treated mice. Compared to control animals, a significant reduction in number, size, and, most significantly, malignant phenotype of liver nodules was observed, thus demonstrating an important prophylactic action of miRNA-based molecules. In summary, in this article, we not only report a simple model of liver cancer in a cirrhotic background but also provide evidence for a potential miRNA-based approach to reduce the risk of HCC development.

Novel Investigations of Flavonoids as Chemopreventive Agents for Hepatocellular Carcinoma

We would like to highlight the application of natural products to hepatocellular carcinoma (HCC). We will focus on the natural products known as flavonoids, which target this disease at different stages of hepatocarcinogenesis. In spite of the use of chemotherapy and radiotherapy in treating HCC, patients with HCC still face poor prognosis because of the nature of multidrug resistance and toxicity derived from chemotherapy and radiotherapy. Flavonoids can be found in many vegetables, fruits, and herbal medicines that exert their different anticancer effects via different intracellular signaling pathways and serve as antioxidants. In this review, we will discuss seven common flavonoids that exert different biological effects against HCC via different pathways.

The role of inflammation and liver cancer

Persistent inflammation is known to promote and exacerbate malignancy. Primary liver cancer, mostly hepatocellular carcinoma (HCC), is a clear example of inflammation-related cancer as more than 90 % of HCCs arise in the context of hepatic injury and inflammation. HCC represents the fifth most common malignancy and the third leading cause of cancer-related death worldwide with about one million new cases diagnosed every year with almost an equal number of deaths. Chronic unresolved inflammation is associated with persistent hepatic injury and concurrent regeneration, leading to sequential development of fibrosis, cirrhosis, and eventually HCC. Irrespective of the intrinsic differences among various etiological factors, a common denominator at the origin of HCC is the perpetuation of a wound-healing response activated by parenchymal cell death and the resulting inflammatory cascade. Hence, the identification of fundamental inflammatory signaling pathways causing transition from chronic liver injury to dysplasia and HCC could depict new predictive biomarkers and targets to identify and treat patients with chronic liver inflammation. This chapter critically discusses the roles of several major cytokines, chemokines, growth factors, transcription factors, and enzymes as well as a distinct network of inflammatory signaling pathways in the development and progression of HCC. It also highlights and analyzes preclinical animal studies showing innovative approaches of targeting inflammatory mediators and signaling by a variety of natural compounds and synthetic agents to achieve effective therapy as well as prevention of hepatic malignancy. Additionally, current limitations and potential challenges associated with the inhibition of inflammatory signaling as well as future directions of research to accelerate clinical development of anti-inflammatory agents to prevent and treat liver cancer are presented.

Modeling progressive non-alcoholic fatty liver disease in the laboratory mouse

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease in the world and its prevalence is rising. In the absence of disease progression, fatty liver poses minimal risk of detrimental health outcomes. However, advancement to non-alcoholic steatohepatitis (NASH) confers a markedly increased likelihood of developing severe liver pathologies, including fibrosis, cirrhosis, organ failure, and cancer. Although a substantial percentage of NAFLD patients develop NASH, the genetic and molecular mechanisms driving this progression are poorly understood, making it difficult to predict which patients will ultimately develop advanced liver disease. Deficiencies in mechanistic understanding preclude the identification of beneficial prognostic indicators and the development of effective therapies. Mouse models of progressive NAFLD serve as a complementary approach to the direct analysis of human patients. By providing an easily manipulated experimental system that can be rigorously controlled, they facilitate an improved understanding of disease development and progression. In this review, we discuss genetically- and chemically-induced models of NAFLD that progress to NASH, fibrosis, and liver cancer in the context of the major signaling pathways whose disruption has been implicated as a driving force for their development. Additionally, an overview of nutritional models of progressive NAFLD is provided.

Prostanoid EP1 receptor as the target of (-)-epigallocatechin-3-gallate in suppressing hepatocellular carcinoma cells in vitro

AIM

To investigate the effects of (-)-epigallocatechin-3-gallate (EGCG), an active compound in green tea, on prostaglandin E(2) (PGE(2))-induced proliferation and migration, and the expression of prostanoid EP(1) receptors in hepatocellular carcinoma (HCC) cells.

METHODS

HCC cell line HepG2, human hepatoma cell lines MHCC-97L, MHCC-97H and human hepatocyte cell line L02 were used. Cell viability was analyzed using MTT assay. PGE(2) production was determined with immunoassay. Wound healing assay and transwell filter assay were employed to assess the extent of HCC cell migration. The expression of EP(1) receptor and Gq protein were examined using Western blot assay.

RESULTS

PGE(2) (4-40000 nmol/L) or the EP(1) receptor agonist ONO-DI-004 (400-4000 nmol/L) increased the viability and migration of HepG2 cells in concentration-dependent manners. EGCG (100 μg/mL) significantly inhibited the viability and migration of HepG2 cells induced by PGE(2) or ONO-DI-004. HepG2 cells secreted an abundant amount of PGE(2) into the medium, and EGCG (100 μg/mL) significantly inhibited the PGE(2)production and EP(1) receptor expression in HepG2 cells. EGCG (100 μg/mL) also inhibited the viability of MHCC-97L cells, but not that of MHCC-97H cells. Both EGCG (100 μg/mL) and EP(1) receptor antagonist ONO-8711 inhibited PGE(2) 4 μmol/L and ONO-DI-004 400 nmol/L-induced growth and migration of HepG2 cells. Both EGCG (100 μg/mL) and ONO-8711 210 nmol/L inhibited PGE(2)- and ONO-DI-004-induced EP(1) expression. EGCG and ONO-8711 had synergistic effects in inhibiting EP(1) receptor expression. PGE(2), ONO-DI-004, ONO-8711, and EGCG had no effects on Gq expression in HepG2 cells, respectively.

CONCLUSION

These findings suggest that the anti-HCC effects of EGCG might be mediated, at least partially, through the suppressing EP(1) receptor expression and PGE(2) production.

Significance of COX-2 and C/EBP β expression in hepatocellular carcinoma

AIM: To investigate the expression of cyclooxygenase-2 (COX-2) and CCAAT/enhancer binding protein β (C/EBP β) and to analyze their correlation with the clinical pathological parameters in hepatocellular carcinoma (HCC).

METHODS: The expression of COX-2 and C/EBP β in 59 HCC tissue specimens and 18 normal hepatic tissue specimens were detected by immunohistochemistry.

RESULTS: The positive rate of COX-2 expression in HCC was 72.9% (P < 0.05). COX-2 expression was correlated with Child-Pugh classification, tumor diameter, TNM stage, vein invasion, lymph node metastasis, and distant metastasis (P < 0.05). The positive rate of C/EBP β expression in HCC was 47.5% (P < 0.05). C/EBP β expression was correlated with history of alcohol use, tumor diameter and TNM stage (P < 0.05). A close correlation was noted between the expression of COX-2 and C/EBP β (r = 0.580, P < 0.05).

CONCLUSION: COX-2 is overexpressed in HCC and may be involved in early hepatocarcinogenesis. C/EBP β-related signal pathway may up-regulate the expression of COX-2 in the early stage of HCC.

Differential expression of E-prostanoid receptors in human hepatocellular carcinoma

Recent studies have shown that inhibition of cyclooxygenases (e.g. COX-2) exerts antitumorigenic effects on hepatocellular carcinomas (HCCs), which are to a significant extent due to the abrogation of PGE(2) synthesis. PGE(2) acts via differentially regulated prostaglandin receptors (EP(1-4)). Our study was designed to investigate the expression pattern of EP-receptors in HCCs and to evaluate the therapeutic potential of selective EP-receptor antagonists. Using tissue microarrays including a total of 14 control livers, 17 liver cirrhoses, 22 premalignant dysplastic nodules (DNs) and 162 HCCs with different histological grades, the expression of COX-2, mPGES-1 and -2 and EP(1-4)-receptors was analyzed. Western immunoblot analyses were performed to confirm the expression in HCC cell lines. The effects of EP(1-4)-receptor antagonism on cell viability and apoptosis were investigated using MTT-assays and FACS-analyses, respectively. COX-2, mPGES-1 and -2 and EP(1-4)-receptors were expressed in all HCC tissues. COX-2 expression was highest in DNs and declined with loss of HCC-differentiation. With respect to COX-2 expression, a converse expression of EP(1-3) -receptors and mPGES-1 and -2 was found in DNs compared to HCCs. Selectively antagonizing EP(1)- and EP(3)-receptors reduced the viability of HCC cells in a dose-dependent manner, which was associated with apoptosis induction. Our results suggest a differential regulation of EP-receptor subtype expression with dedifferentiation of HCCs in which a converse expression pattern for COX-2 in comparison to EP(1-3)-receptors occurs. Of clinical interest, selectively antagonizing EP(1)- and EP(3)-receptors may provide a novel systemic therapeutic approach to the treatment of HCCs.

Targeting MEK is effective chemoprevention of hepatocellular carcinoma in TGF-alpha-transgenic mice

Hepatocellular carcinoma (HCC) causes 600,000 mortalities per year worldwide. Previous studies from our lab provide evidence for altered mitogen-activated protein kinase and extracellular signal-regulated kinase kinase (MEK) signaling in HCC pathogenesis. We hypothesized that pharmacologic targeting of MEK may prevent HCC. Transforming growth factor-alpha-transgenic mice (CD1-MT42) exposed to diethylnitrosamine were randomized to 20 (trial I) or 35 (trial II) weeks of MEK inhibitor PD0325901 (1, 10 mg/kg) or control via orogastric gavage. Ten HCC (44%) formed in trial I controls versus 0 in treatment arms (p<0.05). Fourteen HCC (50%) formed in trial II controls versus 1 (9%) in treatment arms (p<0.05). Mean HCC volume was 578 mm3 in control versus 46 mm3 in the single tumor formed in trial II. In trial I, foci of altered hepatocytes (FAH) formed in 78% of control versus 40% and 0% (1 and 10 mg/kg PD0325901) in treatment arms (p<0.05). In trial II, incidence of FAH was 80% in control versus 20% and 50% (1 and 10 mg/kg PD0325901) in treatment arms (p<0.05). Hepatocyte expression of phosphorylated extracellular signal-regulated kinase dose-dependently decreased in trial I but remained the same in trial II. Control and treated HCC demonstrated similar proliferation rates, but apoptosis appeared increased with treatment. MEK targeting is effective HCC chemoprevention, perhaps by lowering the apoptotic threshold.

Delayed progression of pancreatic intraepithelial neoplasia in a conditional Kras(G12D) mouse model by a selective cyclooxygenase-2 inhibitor

Pancreatic ductal adenocarcinomas are thought to arise from noninvasive, intraductal precursor lesions called pancreatic intraepithelial neoplasias (PanIN). The study of PanINs holds great promise for the identification of early detection markers and effective cancer-preventing strategies. Cyclooxygenase-2 (COX-2) represents an intriguing target for therapeutic and preventive approaches in various human malignancies. The aim of the present study was to evaluate the efficacy of a selective COX-2 inhibitor to prevent the progression of PanINs in a conditional Kras(G12D) mouse model. Offspring of LSL-KRAS(G12D) x PDX-1-Cre intercrosses were randomly allocated to a diet supplemented with the selective COX-2 inhibitor nimesulide (400 ppm) or a control diet. After 10 months, animals were sacrificed. Successful recombination in the pancreas was evaluated by PCR. The pancreas of KRAS(G12D);PDX-1-Cre mice was analyzed for the presence of murine PanINs. Animals fed the COX-2 inhibitor had significantly fewer PanIN-2 and PanIN-3 lesions than control animals (P < 0.05). Ten percent of all pancreatic ducts in the nimesulide-fed animals showed PanIN-2 or PanIN-3 lesions, whereas 40% of the pancreatic ducts in the control animals had PanIN-2 or PanIN-3 lesions. Intrapancreatic prostaglandin E(2) levels were reduced in nimesulide-fed animals. Immunohistochemistry confirmed COX-2 expression in early and late PanINs. In summary, we found that the selective COX-2 inhibitor nimesulide delays the progression of pancreatic cancer precursor lesions in a preclinical animal model. These data highlight the importance of COX-2 in the development of pancreatic cancer. Inhibition of COX-2 may represent an intriguing strategy to prevent pancreatic cancer in high-risk patients.