Increased expression of cyclooxygenase-2 protein during rat hepatocarcinogenesis caused by a choline-deficient, L-amino acid-defined diet and chemopreventive efficacy of a specific inhibitor, nimesulide

Royal Jelly and Chlorella vulgaris Mitigate Gibberellic Acid-Induced Cytogenotoxicity and Hepatotoxicity in Rats via Modulation of the PPARα/AP-1 Signaling Pathway and Suppression of Oxidative Stress and Inflammation

Gibberellic acid (GA3) is a well-known plant growth regulator used in several countries, but its widespread use has negative effects on both animal and human health. The current study assesses the protective effect of royal jelly (RJ) and Chlorella vulgaris (CV) on the genotoxicity and hepatic injury induced by GA3 in rats. Daily oral administration of 55 mg/kg GA3 to rats for 6 constitutive weeks induced biochemical and histopathological changes in the liver via oxidative stress and inflammation. Co-administration of 300 mg/kg RJ or 500 mg/kg CV with GA3 considerably ameliorated the serum levels of AST (aspartate aminotransferase), ALT (alanine aminotransferase), ALP (alkaline phosphatase), γGT (gamma-glutamyl transferase), total bilirubin, and albumin. Lowered malondialdehyde, tumor necrosis factor α (TNF-α), and nuclear factor κB (NF-κB) levels along with elevated SOD (superoxide dismutase), CAT (catalase), and GPx (glutathione peroxidase) enzyme activities indicated the antioxidant and anti-inflammatory properties of both RJ and CV. Also, they improved the histological structure and reduced cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) expressions along with up-regulating peroxisome proliferator activated receptor α (PPARα) and down-regulating activator protein 1 (AP-1) gene expression. Additionally, chromosomal abnormalities and mitotic index were nearly normalized after treatment with RJ and CV. In conclusion, RJ and CV can protect against GA3-induced genotoxicity and liver toxicity by diminishing oxidative stress and inflammation, and modulating the PPARα/AP-1 signaling pathway.

Mitochondrial Genetic and Epigenetic Regulations in Cancer: Therapeutic Potential

Mitochondria are dynamic organelles managing crucial processes of cellular metabolism and bioenergetics. Enabling rapid cellular adaptation to altered endogenous and exogenous environments, mitochondria play an important role in many pathophysiological states, including cancer. Being under the control of mitochondrial and nuclear DNA (mtDNA and nDNA), mitochondria adjust their activity and biogenesis to cell demands. In cancer, numerous mutations in mtDNA have been detected, which do not inactivate mitochondrial functions but rather alter energy metabolism to support cancer cell growth. Increasing evidence suggests that mtDNA mutations, mtDNA epigenetics and miRNA regulations dynamically modify signalling pathways in an altered microenvironment, resulting in cancer initiation and progression and aberrant therapy response. In this review, we discuss mitochondria as organelles importantly involved in tumorigenesis and anti-cancer therapy response. Tumour treatment unresponsiveness still represents a serious drawback in current drug therapies. Therefore, studying aspects related to genetic and epigenetic control of mitochondria can open a new field for understanding cancer therapy response. The urgency of finding new therapeutic regimens with better treatment outcomes underlines the targeting of mitochondria as a suitable candidate with new therapeutic potential. Understanding the role of mitochondria and their regulation in cancer development, progression and treatment is essential for the development of new safe and effective mitochondria-based therapeutic regimens.

Disease Progression and Pharmacological Intervention in a Nutrient-Deficient Rat Model of Nonalcoholic Steatohepatitis

BACKGROUND

There is a marked need for improved animal models of nonalcoholic steatohepatitis (NASH) to facilitate the development of more efficacious drug therapies for the disease.

METHODS

Here, we investigated the development of fibrotic NASH in male Wistar rats fed a choline-deficient L-amino acid-defined (CDAA) diet with or without cholesterol supplementation for subsequent assessment of drug treatment efficacy in NASH biopsy-confirmed rats. The metabolic profile and liver histopathology were evaluated after 4, 8, and 12 weeks of dieting. Subsequently, rats with biopsy-confirmed NASH were selected for pharmacological intervention with vehicle, elafibranor (30 mg/kg/day) or obeticholic acid (OCA, 30 mg/kg/day) for 5 weeks.

RESULTS

The CDAA diet led to marked hepatomegaly and fibrosis already after 4 weeks of feeding, with further progression of collagen deposition and fibrogenesis-associated gene expression during the 12-week feeding period. Cholesterol supplementation enhanced the stimulatory effect of CDAA on gene transcripts associated with fibrogenesis without significantly increasing collagen deposition. Pharmacological intervention with elafibranor, but not OCA, significantly reduced steatohepatitis scores, and fibrosis-associated gene expression, however, was unable to prevent progression in fibrosis scores.

CONCLUSION

CDAA-fed rats develop early-onset progressive NASH, which offers the opportunity to probe anti-NASH compounds with potential disease-modifying properties.

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.

Persistent fibrosis in the liver of choline-deficient and iron-supplemented L-amino acid-defined diet-induced nonalcoholic steatohepatitis rat due to continuing oxidative stress after choline supplementation

Nonalcoholic steatohepatitis (NASH) is characterized by combined pathology of steatosis, lobular inflammation, fibrosis, and hepatocellular degeneration, with systemic symptoms of diabetes or hyperlipidemia, all in the absence of alcohol abuse. Given the therapeutic importance and conflicting findings regarding the potential for healing the histopathologic features of NASH in humans, particularly fibrosis, we investigated the reversibility of NASH-related findings in Wistar rats fed a choline-deficient and iron-supplemented l-amino acid-defined (CDAA) diet for 12weeks, with a recovery period of 7weeks, during which the diets were switched to a choline-sufficient and iron-supplemented l-amino acid-defined (CSAA) one. Analysis showed that steatosis and inflammation were significantly resolved by the end of the recovery period, along with decreases in AST and ALT activities within 4weeks. In contrast, fibrosis remained even after the recovery period, to an extent similar to that in continuously CDAA-fed animals. Real-time reverse transcriptase-polymerase chain reaction, Western blot, and immunohistochemical investigations revealed that expression of some factors indicating oxidative stress (CYP2E1, 4-HNE, and iNOS) were elevated, whereas catalase and SOD1 were decreased, and a hypoxic state and CD34-positive neovascularization were evident even after the recovery period, although the fibrogenesis pathway by activated α-SMA-positive hepatic stellate cells via TGF-β and TIMPs decreased to the CSAA group level. In conclusion, persistent fibrosis was noted after the recovery period of 7weeks, possibly due to sustained hypoxia and oxidative stress supposedly caused by capillarization. Otherwise, histopathological features of steatosis and inflammation, as well as serum AST and ALT activities, were recovered.

DEN+2-AAF-induced multistep hepatotumorigenesis in Wistar rats: supportive evidence and insights

Diethylnitrosamine (DEN), found in many commonly consumed foods, has been reported to induce cancers in animals and humans. Several models have been developed to study multistage carcinogenesis in rat liver; these include the Solt-Farber-resistant hepatocyte model. In the Solt-Farber model, the initiation consists of either a necrogenic dose of a hepatocarcinogen or a non-necrogenic dose in conjunction with partial hepatectomy (PH). We report a novel protocol for tumor induction in liver which eliminates the need for PH. Male Wistar rats were injected with single i.p. dose of DEN (200 mg/kg body weight), controls received saline only. After 1 week of recovery, the DEN-treated animals were administered with the repeated doses of 2-acetyamino fluorine (150 mg/kg body weight) orally in 1 % carboxymethyl cellulose that served as promoting agent. Thirty days after the DEN administration, hepatocellular damage was observed as evident by histopathological analysis. The marker enzyme analysis showed elevated levels of serum AST, ALT, and alkaline phosphatase and a decrease in the levels of liver superoxide dismutase and catalase. The oxidative stress in liver was confirmed by elevated levels of lipid peroxidation and a decrease in antioxidant parameters.

Spontaneous amphophilic focus in the liver of a young Sprague-Dawley rat

Altered hepatocellular focus was histopathologically observed in the liver of a 6-week-old Sprague-Dawley rat. The hepatocytes within this lesion had diffusely eosinophilic cytoplasm with scattered basophilia and slightly enlarged nuclei with prominent nucleoli. Based on these cytological characteristics, the lesion of these hepatocytes was classified as an amphophilic focus. This is the first report to describe spontaneous amphophilic focus in a young rat.

Cyclooxygenase 2 and Prostaglandin E2 are not Involved in N-Nitrosodiethylamine-Initiated Early Rat Hepatocarcinogenesis

The present study was undertaken to investigate the effect of dietary supplementation with nimesulide or eugenol on N-nitrosodiethylamine (DEN)-initiated early hepatocarcinogenesis in F344 male rats. Both compounds did not alter the expression of cytochrome P450 (CYP) 2E1, the enzyme that plays a major role in the activation of DEN to genotoxic products; however, nimesulide induced the expression of CYP1A1. Western blot analysis revealed that COX-1 and COX-2 protein expressions were not modulated by DEN compared with normal controls. Furthermore, post-initiation feeding with nimesulide or eugenol did not modulate COX-2 protein expression in normal or DEN-treated rats, whereas eugenol significantly increased the liver prostaglandin E₂ (PGE₂) levels of DEN-injected animals compared with the DEN controls. Ultimately, nimesulide or eugenol did not modify DEN-induced hepatocarcinogenesis as evidenced by insignificant changes in the number and size of preneoplastic placental glutathione S-transferase (GST-P) positive liver foci compared with the DEN controls. These results suggest that COX-2, as well as prostaglandin E₂, may play no role in the post-initiation development of DEN-induced rat hepatocarcinogenesis at an early stage.

Advancements of cyclooxygenase inhibitor in the prevention and treatment of hepatoma

It was reported that the cyclooxygenase-2 (COX-2) and its products were over-expressed in many malignant tumors. Non-steroidal anti-inflammatory drugs (NSAIDs) can inhibit COX activity, and also can reduce proliferation, enhance apoptosis, decrease angiogenesis and invasiveness of tumor cells. Hepatoma is one of common malignancies worldwide, and its prognosis is still extremely poor and the cellular mechanisms contributing to hepatic carcinogenesis are relatively unknown. Therefore, the prevention and treatment of liver cancer are limited. At present, it is important to find new drugs and investigate their action mechanisms. This article provides a brief review on the research progress of COX inhibitor in the prevention and treatment of hepatoma.

Potential inhibitory effects of D-allose, a rare sugar, on liver preneoplastic lesion development in F344 rat medium-term bioassay

D-allose, the C-3 epimer of d-glucose, is a monosaccharide present in minute quantities in nature and a rare sugar. The effects of D-allose on diethyl nitrosamine (DEN)-induced hepatocarcinogenesis were examined in male F344 rats by a rat medium-term bioassay based on the two-step model of hepatocarcinogenesis (experiment 1). In addition, a DNA microarray analysis was employed to clarify possible mechanisms of action of D-allose (experiment 2). The antioxidation potential of D-allose solution itself or of serum in rats treated with D-allose was also examined directly by measuring Cu(+)-reducing antioxidation power (experiment 3). Furthermore, to investigate the effects of D-allose in vivo under conditions of oxidative stress, it was administered with a choline-deficient, L-amino acid-defined diet (CDAA) in the medium-term liver carcinogenesis bioassay (experiment 4). Experiment 1 demonstrated no effects of D-allose on the development of glutathione S-transferase placental form (GST-P) positive foci in the liver. From DNA microarray analysis, several mRNA markers were found to be altered with functions related to apoptosis and cell proliferation (experiment 2), although D-allose itself and serum in vivo exhibited no antioxidation power directly (experiment 3). When D-allose was administered with the CDAA diet, decreases in the area and number of GST-P positive foci were noted with P values of 0.158 for area (%) and 0.061 for number (/cm(2)) (experiment 4). These results suggest the potential inhibitory effect of D-allose on liver carcinogenesis, particularly under oxidative stress conditions.

Depression of T cell-mediated immunity reduces sulfadimethoxine-induced capsular inflammation and inhibits associated development of invasive thyroid follicular cell carcinomas in rats

We previously demonstrated that thyroid capsular inflammation induced by continuous treatment with the antithyroidal agent sulfadimethoxine is associated with development of invasive follicular cell carcinomas in rats initiated with N-bis(2-hydroxypropyl)nitrosamine (DHPN). The inflammatory changes are characterized by large numbers of macrophages and lymphocytes as well as fibroblasts and we hypothesized that it might be enhanced by interplay between macrophages and T cells. To clarify this hypothesis, a comparative study was conducted between athymic nude (rnu/rnu) rats and euthymic (rnu/+) littermates initiated with DHPN (2800 mg/kg, s.c.) followed by sulfadimethoxine treatment in drinking water (0.1%) for 10 weeks. In rnu/+rats, marked capsular thickening with inflammation was induced along with invasive follicular cell carcinomas (2.8 +/- 1.3/rat). In rnu/rnu rats, limited fibrous capsular thickening was noted with or without minimal inflammatory change, and the multiplicity of invasive carcinomas was significantly lower (1.1 +/- 1.0/rat, P < 0.01). Inducible nitric oxide synthase expression in the inflamed lesions was detected in three of 10 rnu/+rats but in none of the rnu/rnu animals. The results thus suggest that development of invasive carcinomas is enhanced by capsular inflammation mediated by T cells, and inducible nitric oxide synthase induction may play a role in tumor progression.

Mitochondrial DNA mutations in human cancer

Somatic mitochondrial DNA (mtDNA) mutations have been increasingly observed in primary human cancers. As each cell contains many mitochondria with multiple copies of mtDNA, it is possible that wild-type and mutant mtDNA can co-exist in a state called heteroplasmy. During cell division, mitochondria are randomly distributed to daughter cells. Over time, the proportion of the mutant mtDNA within the cell can vary and may drift toward predominantly mutant or wild type to achieve homoplasmy. Thus, the biological impact of a given mutation may vary, depending on the proportion of mutant mtDNAs carried by the cell. This effect contributes to the various phenotypes observed among family members carrying the same pathogenic mtDNA mutation. Most mutations occur in the coding sequences but few result in substantial amino acid changes raising questions as to their biological consequence. Studies reveal that mtDNA play a crucial role in the development of cancer but further work is required to establish the functional significance of specific mitochondrial mutations in cancer and disease progression. The origin of somatic mtDNA mutations in human cancer and their potential diagnostic and therapeutic implications in cancer are discussed. This review article provides a detailed summary of mtDNA mutations that have been reported in various types of cancer. Furthermore, this review offers some perspective as to the origin of these of mutations, their functional consequences in cancer development, and possible therapeutic implications.

Cyclooxygenases in hepatocellular carcinoma

Many epidemiological studies demonstrate that treatment with non-steroidal anti-inflammatory drugs (NSAIDs) reduce the incidence and mortality of certain malignancies, especially gastrointestinal cancer. The cyclooxygenase (COX) enzymes are well-known targets of NSAIDs. However, conventional NSAIDs non-selectively inhibit both the constitutive form COX-1, and the inducible form COX-2. Recent evidence indicates that COX-2 is an important molecular target for anticancer therapies. Its expression is undetectable in most normal tissues, and is highly induced by pro-inflammatory cytokines, mitogens, tumor promoters and growth factors. It is now well-established that COX-2 is chronically overexpressed in many premalignant, malignant, and metastastic cancers, including hepatocellular carcinoma (HCC). Overexpression of COX-2 in patients with HCC is generally higher in well-differentiated HCCs compared with less-differentiated HCCs or histologically normal liver, suggesting that COX-2 may be involved in the early stages of hepatocarcinogenesis, and increased expression of COX-2 in noncancerous liver tissue has been significantly associated with shorter disease-free survival in patients with HCC.

In tumors, overexpression of COX-2 leads to an increase in prostaglandin (PG) levels, which affect many mechanisms involved in carcinogenesis, such as angiogenesis, inhibition of apoptosis, stimulation of cell growth as well as the invasiveness and metastatic potential of tumor cells.

The availability of novel agents that selectively inhibit COX-2 (COXIB), has contributed to shedding light on the role of this molecule. Experimental studies on animal models of liver cancer have shown that NSAIDs, including both selective and non-selective COX-2 inhibitors, exert chemopreventive as well as therapeutic effects. However, the key mechanism by which COX-2 inhibitors affect HCC cell growth is as yet not fully understood.

Increasing evidence suggests the involvement of molecular targets other than COX-2 in the anti-proliferative effects of COX-2 selective inhibitors. Therefore, COX-inhibitors may use both COX-2-dependent and COX-2-independent mechanisms to mediate their antitumor properties, although their relative contributions toward the in vivo effects remain less clear.

Here we review the features of COX enzymes, the role of the expression of COX isoforms in hepatocarcinogenesis and the mechanisms by which they may contribute to HCC growth, the pharmacological properties of COX-2 selective inhibitors, the antitumor effects of COX inhibitors, and the rationale and feasibility of COX-2 inhibitors for the treatment of HCC.

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

Cyclooxygenase 2 (COX-2) and retinoid X receptor alpha (RXRalpha) are suggested to have roles in carcinogenesis. COX-2 inhibitors have been reported to suppress growth of hepatocellular carcinoma (HCC) cell lines in vitro. However, little is known about the preventive effect of these drugs on spontaneous hepatocarcinogenesis in vivo. Etodolac exists in a racemic mixture containing S- and R-etodolac. S-etodolac is responsible for COX-2 inhibitory activity and R-etodolac is related to the downregulation of RXRalpha. Here, the effect of etodolac on spontaneous development of HCC in fatty liver Shionogi mice is evaluated. Etodolac was administered at a low (2 mg/kg) or high (10 mg/kg) dose three times a week for 16 months starting at the age of 3 months. The development of HCC was suppressed slightly in the high-dose group, and suppressed markedly in the low-dose group, although the development of fatty liver was not inhibited in either group. Plasma prostaglandin E2 levels were also decreased significantly in the low-dose group, consistent with the suppression of HCC. The expression of RXRalpha and proliferating cell nuclear antigen in non-tumorous liver tissues was decreased significantly in both the low-dose and high-dose groups. These findings show that etodolac treatment at an optimum dose suppresses hepatocarcinogenesis in vivo, and may be useful for preventing the development of HCC in humans.

Expression of inducible nitric oxide (NO) synthase but not prevention by its gene ablation of hepatocarcinogenesis with fibrosis caused by a choline-deficient, L-amino acid-defined diet in rats and mice

Expression of inducible nitric oxide synthase (iNOS) and effects of iNOS gene ablation on the hepatocarcinogenesis associated with fibrosis caused by a choline-deficient, L-amino acid-defined (CDAA) diet, were examined in male F344 rats and C57BL/6J wild-type and iNOS-/- mice. Western blot, RT-PCR and immunohistochemical analyses revealed increased expression of iNOS protein and mRNA in the livers of rats and wild-type mice fed a CDAA diet for 12-80 weeks, associated with elevated serum NO(x) and liver nitrotyrosine levels. iNOS-/- mice demonstrated greater liver injury and fibrosis in the early stage than their wild-type counterparts, but this did not significantly affect the incidence and multiplicity of altered foci, adenomas and hepatocellular carcinomas in spite of immunohistochemical iNOS expression in these lesions. Results suggested no major determinant roles of the expressed iNOS in the development of liver tumors caused by the CDAA diet.

Early induction of TGF-beta1 through a fasting-re-feeding regimen promotes liver carcinogenesis by a sub-initiating dose of diethylnitrosamine

We previously reported that a sub-necrogenic dose (20 mg/kg) of diethylnitrosamine (DENA) can induce the development of liver cancer when rats undergo a fasting-re-feeding regimen. The present study was undertaken to establish whether fasting followed by re-feeding builds up mechanisms able to trigger liver fibrosis, eventually leading to cirrhosis and cancer. Adult male rats, for fasted 4 days, were given 20 mg/kg of DENA after 1 day of re-feeding; in parallel, consistently fed animals receiving 20 mg/kg (sub-necrogenic) or 200 mg/kg (necrogenic dose) of DENA were used as negative and positive controls, respectively. All three groups were then subjected to the 2-acetylaminofluorene/carbon tetrachloride promoting regimen. Fasting induced moderate apoptosis in liver tissue, as evidenced by increased levels of transforming growth factor-beta1 (TGF-beta1) and Bax proteins and by a dramatic drop in the level of Bcl-2. Subsequent re-feeding caused all changes to revert except TGF-beta1 up-regulation. Histological findings of inflammation and fibrosis were consistently associated with increased production of TGF-beta1, the inflammatory cytokine with the most pronounced profibrogenic action. Thus, up-regulation of TGF-beta1 expression appears as a major mechanism by which the fasting-re-feeding regimen predisposes to initiation and promotion of liver carcinogenesis in rats. Avoiding fasting-re-feeding could be considered in the nutritional status of patients with liver fibrosis.

Temporal correlation of pathology and DNA damage with gene expression in a choline-deficient model of rat liver injury

Hepatocellular carcinoma (HCC) is the terminal event in chronic liver diseases with repeated cycles of cellular injury and regeneration. Although much is known about the cellular pathogenesis and etiological agents leading to HCC, the molecular events are not well understood. The choline-deficient (CD) model of rodent HCC involves the consecutive emergence of a fatty liver, apoptosis, compensatory proliferation, fibrosis, and cirrhosis that is markedly similar to the sequence of events typified by human HCC. Moreover, oxidative stress is thought to play a pivotal role in the progression of the disease. Here, we hypothesize that gene expression profiling can temporally mirror the histopathology and oxidative DNA damage observed with this model. We show that clusters of highly co-regulated genes representing distinct cellular pathways for lipid biosynthesis and metabolism, apoptosis, cell proliferation, and tissue remodeling temporally correlate with the well-defined sequential emergence of pathological alterations in the progression of liver disease. Additionally, an oxidative stress signature was observed that was corroborated in a time-dependent manner with increases in oxidized purines and abasic sites in DNA. Collectively, expression patterns were strongly driven by pathology, demonstrating that patterns of gene expression in advanced stages of liver disease are primarily driven by histopathological changes and to a much lesser degree by the original etiological agent. In conclusion, gene expression profiling coupled with the CD model of HCC provides a unique opportunity to unveil the molecular events associated with various stages of liver injury and carcinogenesis and to distinguish between causal and consecutive changes.

Overexpression of cyclooxygenase-2 in human HepG2, Bel-7402 and SMMC-7721 hepatoma cell lines and mechanism of cyclooxygenase-2 selective inhibitor celecoxib-induced cell growth inhibition and apoptosis

AIM: To investigate the cyclooxygenase-2 (COX-2) expression level in human HepG2, Bel-7402 and SMMC-7721 hepatoma cell lines and the molecular mechanism of COX-2 selective inhibitor celecoxib-induced cell growth inhibition and cell apoptosis.

METHODS: Hepatoma cells were cultured and treated with celecoxib. Cell in situ hybridization (ISH) and immunocytochemistry were used to detect COX-2 mRNA and protein expression. Proliferating cell nuclear antigen and phosphorylated Akt were also detected by immunocytochemistry assay. Cell growth rates were assessed by 3-(4, 5-dimethylthiazol-2-yl-2, 5-diphenylte-trazolium (MTT) bromide colorimetric assay. Celecoxib-induced cell apoptosis was measured by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) and flow cytometry (FCM). The phosphorylated Akt and activated fragments of caspase-9, caspase-3 were examined by Western blotting analysis.

RESULTS: Increased COX-2 mRNA and protein expression were detected in all three hepatoma cell lines. Celecoxib could significantly inhibit cell growth and the inhibitory effect was in a dose- and time-dependent manner evidenced by MTT assays and morphological changes. The apoptotic index measured by TUNEL increased correspondingly with the increased concentration of celecoxib and the reaction time. With 50 μmol/L celecoxib treatment for 24 h, the apoptotic index of HepG2, BEL-7402 and SMMC-7721 cells was 25.01±3.08%, 26.40±3.05%, and 30.60±2.89%, respectively. Western blotting analysis showed remarkable activation of caspase-9, caspase-3 and dephosphorylation of Akt (Thr308). Immunocytochemistry also showed the reduction of PCNA expression and phosphorylation Akt (Thr308) after treatment with celecoxib.

CONCLUSION: COX-2 mRNA and protein overexpression in HepG2, Bel-7402 and SMMC-7721 cell lines correlate with the increased cell growth rate. Celecoxib can inhibit proliferation and induce apoptosis of hepatoma cell strains in a dose- and time-dependent manner.

Sinusoidal endothelial COX-1-derived prostanoids modulate the hepatic vascular tone of cirrhotic rat livers

CCl(4) cirrhotic rat liver exhibits a hyperresponse to the alpha(1)-adrenergic agonist methoxamine (Mtx) that is associated with enhanced thromboxane A(2) (TXA(2)) production and is abrogated by indomethacin. To further elucidate the molecular mechanisms involved in the hyperresponse to vasoconstrictors, portal perfusion pressure dose-response curves to Mtx were performed in CCl(4) cirrhotic rats livers after preincubation with vehicle, the cyclooxygenase (COX)-1 selective inhibitor SC-560, and the COX-2 selective inhibitor SC-236. TXA(2) production was determined in samples of the perfusate. COX-1 expression was analyzed and quantified in hepatocytes, Kupffer cells, sinusoidal endothelial cells (SEC), and hepatic stellate cells (HSC) isolated from control and cirrhotic rat livers by double-immunofluorescence staining, with specific markers for each population using flow cytometry or Western blot analysis. COX-1 protein levels were not significantly increased in cirrhotic livers, but COX-2 protein expression was increased. COX-1 inhibition, but not COX-2, significantly attenuated the response to Mtx and prevented the increased production of TXA(2). Cirrhotic livers showed an increased expression of COX-1 in SEC and reduced expression in HSC compared with control livers, whereas COX-1 was similarly distributed in Kupffer cells. Despite abundant hepatic COX-2 expression, the increased response to Mtx of cirrhotic livers is mainly dependent of COX-1. Upregulation of COX-1 in cirrhotic SEC may be responsible for the hyperesponse to Mtx.

Effect of a selective cyclooxygenase-2 inhibitor, nimesulide, on the growth of lung tumors and their expression of cyclooxygenase-2 and peroxisome proliferator- activated receptor-gamma

PURPOSE

The objectives of this study were to evaluate the effect of a cyclooxygenase (COX)-2 inhibitor, nimesulide, on the growth inhibition of s.c. human lung A549 adenocarcinoma tumors and to assess the effect of nimesulide on the expression of COX-2 and peroxisome proliferator-activated receptor (PPAR)-gamma in lung tumors harvested from mice.

EXPERIMENTAL DESIGN

Female nu/nu mice were xenografted with s.c. A549 lung tumors, and 1 day after tumor implantation, the mice were fed with a diet containing nimesulide at 250-1500 ppm doses. Tumor dimensions were monitored twice weekly, and tumor samples isolated from mice were used to determine prostaglandin E(2) (PGE(2)) levels by enzyme immunoassay, expression of COX-2 and PPAR-gamma by Western blotting and immunohistochemistry. Furthermore, the induction of apoptosis in tumor specimens was determined by terminal deoxynucleotidyl transferase-mediated nick end labeling staining.

RESULTS

Nimesulide treatment showed a dose-dependent growth-inhibitory effect of A549 tumors with a maximum of 77.7% inhibition at 1500 ppm of nimesulide. Western blotting experiments showed similar expression of COX-2 in both control and nimesulide (250-1500 ppm)-treated mice tumor tissues. PPAR-gamma was found to be overexpressed as a result of 1500 ppm nimesulide treatment and was not detected in tumors from control or 250-1000 ppm nimesulide-treated mice. Nimesulide (1500 ppm) significantly reduced intratumor PGE(2) levels (P < 0.001) and induced apoptosis in 25% of tumor cells as compared with control tumors.

CONCLUSIONS

Nimesulide (1500 ppm) induced growth inhibition of A549 lung tumors is associated with the reduction of intratumor PGE(2) levels but without affecting the expression of COX-2. Nimesulide-induced enhancement of the expression of PPAR-gamma may also contribute to its antitumor effect, which needs to be further investigated.

Herpes simplex virus thymidine kinase gene transduction enhances tumor growth rate and cyclooxygenase-2 expression in murine colon cancer cells

Transduction of tumor cells with herpes simplex virus thymidine kinase (HSV-tk) gene and subsequent treatment with the prodrug ganciclovir (GCV) is the most common system utilized to date for "suicide" gene therapy of cancer. In the current report, we show that HSV-tk gene transduction enhances tumor growth rate of murine colon cancer cells, that are implanted subcutaneously in syngeneic mice, and enhances cyclooxygenase-2 (COX-2) protein expression and prostaglandin E(2) (PGE(2)) release in vitro and in vivo. It is further shown that the observed phenomenon is related to the presence of the HSV-tk sequence insert in the retroviral vector used for HSV-tk gene delivery. Transduction of murine colon cancer cells with control vector, carrying the neomycin-resistance gene alone, failed to increase tumor growth rate and COX-2 protein expression or PGE(2) production. On the contrary, it even decreased tumor growth, COX-2 protein expression and PGE(2.) The growth rate of HSV-tk-transduced murine tumors was significantly reduced by treatment with the selective COX-2 inhibitor nimesulide. Additionally, we demonstrate herein that both enhanced growth rate of HSV-tk-transduced murine tumors and increased levels of PGE(2) in HSV-tk-transduced cells persist upon the development of GCV resistance. Taken together, these results provide a better understanding of the direct effect of HSV-tk gene transduction on tumor cell biology and target tumor development.

Inhibition of the development of hepatocellular carcinomas by phenyl N-tert-butyl nitrone in rats fed with a choline-deficient, l-amino acid-defined diet

Effects of phenyl N-tert-butyl nitrone (PBN), a spin-trapping agent, on the development of frank cancers were examined in male Wistar rats fed with a choline-deficient, l-amino acid-defined (CDAA) diet for 70 weeks. PBN (0.065% in the drinking water) reduced incidences, multiplicities and possibly sizes of both hepatocellular adenomas and carcinomas when administered for all 70 weeks or only for the first 26 weeks, and those of carcinomas but not adenomas, when administered only for the last 44 weeks. These results indicate that PBN can prevent the development of frank HCCs in the CDAA diet model. The anti-carcinogenic effect of PBN may be ascribed to the prevention of both the development of HCAs and their malignant conversion to HCCs. If such findings can be generalized, PBN may be able to serve as a good tool to investigate molecular mechanisms underlying carcinogenic processes.

Novel combination of cyclooxygenase-2 and MEK inhibitors in human hepatocellular carcinoma provides a synergistic increase in apoptosis

Cyclooxygenase-2 (COX-2) and ERK-MAPK mitogenic signaling pathways are important in human hepatocellular carcinoma. We investigated the effect of COX-2 inhibition on ERK-MAPK signaling and the effect of combining MEK (MAPK kinase) and COX-2 inhibitors in human hepatocellular carcinoma in vitro. COX and ERK expression were determined by immunoblot in HepG2 and Hep3B cells. COX-2 and MEK activity were determined by prostaglandin E(2) assay and phosphospecific immunoblot, respectively. Cell growth was determined by cell proliferation and cell counts. Apoptosis was determined by DNA fragmentation enzyme-linked immunosorbent assay and flow cytometry. Cell cycle was determined by flow cytometry. HepG2 and Hep3B cells do not express COX-1 or COX-2. Correspondingly, basal and agonist (arachidonic acid, lipopolysaccharide)-stimulated COX-2 activity is undetectable. Treatment of HepG2 and Hep3B cells with NS398 resulted in an increase in ERK1/2 phosphorylation (MEK activity) in a concentration-dependent fashion (NS398, 1 to 100 micromol/L). Treatment with the COX-2 inhibitor NS398 in the presence of U0126 (MEK inhibitor) effectively suppressed ERK1/2 phosphorylation as determined by phosphospecific ERK1/2 immunoblot. Total ERK1/2 and COX-2 were unchanged with NS398 and U0126 treatments. In HepG2 cells, NS398 (1 to 100 micromol/L) decreased apoptosis as determined by DNA fragmentation enzyme-linked immunosorbent assay. Relative apoptosis was increased with U0126 alone or in combination with NS398 (9 to 10 times the control value), eliminating the anti-apoptotic effect of NS398. In Hep3B cells, apoptosis was unchanged with NS398 (1 to 50 micromol/L) or U0126 (1 to 10 micromol/L) alone. The combination of NS398 and U0126 in Hep3B cells resulted in a synergistic increase in apoptosis (10 times the control value). Relative apoptosis in both cell lines strongly correlated with changes in the expression of the antiapoptotic protein Bcl-xL. Cellular growth was assessed by colorimetric proliferation assay and cell counts. HepG2 and Hep3B cells had concentration-dependent inhibition of cell growth with NS398 or U0126 treatment alone. The combination of NS398 and U0126 resulted in complementary inhibitory effects on growth. Growth inhibitory effects in HepG2 and Hep3B cells with combination treatment appear to be, in part, secondary to the induction of G(0)/G(1) and G(2)/M cell cycle arrest, respectively, as determined by flow cytometry. Despite differential signaling in HepG2 and Hep3B cells, the sum effect of combining the COX-2 inhibitor NS398 and the MEK inhibitor U0126 results in enhanced antitumor actions. This novel combination may be useful for in vivo studies of hepatocellular carcinoma.

Inhibitory effects of selective cyclooxygenase-2 inhibitors, nimesulide and etodolac, on the development of squamous cell dysplasias and carcinomas of the tongue in rats initiated with 4-nitroquinoline 1-oxide

The present study was conducted to examine the effects of selective cyclooxygenase (COX)-2 inhibitors, nimesulide and etodolac, on early stages of tongue carcinogenesis due to 4-nitroquinoline 1-oxide(4-NQO). Fischer 344 rats, 6 weeks old, were given 15 ppm of 4-NQO in their drinking water for 8 weeks followed by diet containing either nimesulide or etodolac at the doses of 150 and 300 ppm for 16 weeks. Rats were sacrificed at 24 weeks and tongue lesions were histologically examined. Nimesulide dose-dependently reduced the incidence and multiplicity of squamous cell dysplasias and carcinomas (SCCs), with significance at the 300 ppm dose. This suppression was associated with an increased incidence and multiplicity of hyperplasias. Etodolac exhibited similar but less extensive suppressive effects. The results suggest that COX-2 is involved in the progression of hyperplasia to dysplasia and from dysplasia to SCCs.

Synergistic effects of nimesulide and 5-fluorouracil on tumor growth and apoptosis in the implanted hepatoma in mice

AIM: To compare the effect of nimesulide or/and 5-fluorouracil (5-FU) on tumor growth inhibition and apoptosis in mice with the implanted hepatoma and to observe their possible interactions.

METHODS: The inhibitory effects on tumor growth was evaluated by inhibition rate. Apoptosis was assessed by the ultrastructural, flow cytometry features and the DNA ladder demonstrated by agarose gel electrophoresis. PGE₂ level was determined by radioimmunoassay. Expression levels of c-jun, c-fos and p53 were evaluated by western blotting.

RESULTS: Nimesulide or 5-FU alone inhibited the growth of hepatoma, while a synergistic effect was observed for a combined use of both. More pronounced morphologic changes for tumor cell apoptosis and the DNA ladder were found for the latter treatment. Expression levels of c-jun and p53 were found to be elevated for the tumors from mice treated with nimesulide and 5-FU comparing to those with either of them, but a reduced PGE₂ level was observed only for the treatment with nimesulide. No change was detected on c-fos expression.

CONCLUSION: Nimesulide and 5-FU appear to have synergistic effects for the growth inhibition and apoptosis induction. Both were found to be overexpressed in p53 and c-jun proteins, rather than that of c-fos, associations with the resulted apoptosis.

Effects of phenyl N-tert-butyl nitrone and its derivatives on the early phase of hepatocarcinogenesis in rats fed a choline-deficient, L-amino acid-defined diet

The present study examined the effects of various derivatives of a radical trapping agent, phenyl N-tert-butyl nitrone, on the early phase of hepatocarcinogenesis in male Wistar rats fed a choline-deficient, L-amino acid-defined diet for 16 weeks. The derivatives used were 4-hydroxyphenyl (a physiologically major metabolite), 3-hydroxyphenyl, 2-hydroxyphenyl and 2-sulfoxyphenyl N-tert-butyl nitrone, and their effects were studied in a comparison with those of the parent compound, phenyl N-tert-butyl nitrone. The sizes of putatively preneoplastic, glutathione S-transferase placental form-positive lesions and the levels of extra-nuclear oxidative injury of hepatocytes, using the formation of 2-thiobarbituric acid-reacting substances as a parameter, were decreased by all doses (0.009%, 0.045% and 0.090% in diet) of 4-hydroxyphenyl N-tert-butyl nitrone and only by the highest dose of 3-hydroxyphenyl N-tert-butyl nitrone and phenyl N-tert-butyl nitrone. While 4-hydroxyphenyl N-tert-butyl nitrone, 3-hydroxyphenyl N-tert-butyl nitrone and phenyl N-tert-butyl nitrone all enhanced and inhibited hepatocellular apoptosis in preneoplastic lesions and their surrounding tissue, respectively, only 4-hydroxyphenyl N-tert-butyl nitrone additionally inhibited hepatocyte proliferation both in preneoplastic lesions and their surrounding tissue. 2-Hydroxyphenyl or 2-sulfoxyphenyl N-tert-butyl nitrone did not exert any of the above effects. These results suggest that the selective induction of apoptosis in preneoplastic hepatocyte populations plays a crucial role in the inhibition of hepatocarcinogenesis derived by phenyl N-tert-butyl nitrone and its effective derivatives. Further, the metabolic conversion to 4-hydroxyphenyl N-tert-butyl nitrone may also be important for the inhibitory effects of phenyl N-tert-butyl nitrone on hepatocarcinogenesis.

Inhibition of the expression of alpha-smooth muscle actin in human hepatic stellate cell line, LI90, by a selective cyclooxygenase 2 inhibitor, NS-398

Cyclooxygenase 2 (COX-2) has been thought to be associated with liver fibrosis whereas it is well known that hepatic stellate cells (HSC) play a central role in the pathogenesis of liver fibrosis. There is little evidence of how COX-2 regulates the activation of human HSC or the mechanism involved. In this study, we investigated the effect of a COX-2 inhibitor, NS-398, on a line of human HSC, LI90. Our findings demonstrated that alpha-smooth muscle actin (alpha-SMA) protein expression was inhibited in a dose-dependent manner by treatment with NS-398. Proliferation cell nuclear antigen (PCNA) expression and cell growth were partially down-regulated. The generation of PGE2, IL-8, IL-6, and hyaluronan in the cultured medium was also inhibited. In conclusion, our findings imply that a selective COX-2 inhibitor might be a potential drug for the chemoprevention and treatment of liver fibrosis by inhibiting the activation of HSC.

COX-2 - a target for preventing hepatic carcinoma?

Hepatocellular carcinoma (HCC) is one of the most common reasons for malignancy-related death in Africa and Asia and is still recognised as the leading cancer in men in Taiwan. Despite enthusiastic efforts in early diagnosis, aggressive surgical treatment and application of additional nonoperative modalities, its prognosis is still dismal. This emphasises the necessity to develop new measures and strategies for its prevention. Inducible cyclooxygenease 2 (COX-2) is an immediate-early (IE) response gene and extensive studies conducted over the past few years have recognised its overexpression in several carcinomas and thus its implication in carcinogenesis. Recent studies have suggested that overexpression of COX-2 might be one of the leading factors in hepatic carcinogenesis. COX-2 can induce angiogenesis via vascular endothelial growth factor (VEGF) and prostaglandin production and can also inhibit apoptosis by inducing the antiapoptotic factor Bcl-2 as well as activating antiapoptotic signalling through Akt/PKB. Therefore, the use of selective inhibitors for the downregulation of COX-2 activity might be a target for preventing hepatic carcinoma development.

Development of hepatocellular adenomas and carcinomas associated with fibrosis in C57BL/6J male mice given a choline-deficient, L-amino acid-defined diet

Development of hepatocellular carcinomas in rats caused by a choline-deficient, L-amino acid-defined (CDAA) diet, usually associated with fatty liver, fibrosis, cirrhosis and oxidative DNA damage, has been recognized as a useful model of hepatocarcinogenesis caused by endogenous factors. In the present study, in order to further explore involved factors and genes, we established an equivalent model in spontaneous liver tumor-resistant C57BL/6J mice. Six-week-old males and females were continuously fed the CDAA diet and histological liver lesions and oxidative DNA damage due to 8-hydroxydeoxyguanosine (8-OHdG) were examined after 22, 65 and 84 weeks. In male mice, fatty change and fibrosis were evident at 22 weeks, and preneoplastic foci of altered hepatocytes were seen at an incidence of 8/8 (100%) and a multiplicity of 6.6 +/- 4.0 per mouse at 65 weeks. Hepatocellular adenomas and carcinomas developed at incidences of 16/24 (66.7%) and 5/24 (20.8%), and multiplicities of 1.42 +/- 1.32 and 0.29 +/- 0.62, respectively, at 84 weeks. The female mice exhibited resistance to development of these lesions. The CDAA diet also increased 8-OHdG levels in male but not female mice. These results indicate that a CDAA diet causes hepatocellular preneoplastic foci, adenomas and carcinomas associated with fibrosis and oxidative DNA damage in mice, as in rats, providing a hepatocarcinogenesis model caused by endogenous factors in mice.