Cyclooxygenase-2 mRNA is up-regulated in cirrhotic or chronic hepatitis liver adjacent to hepatocellular carcinoma

A study on construction of a prognosis model for liver cancer based on analgesic targets and screening therapeutic drugs

BACKGROUND

Liver cancer is one of the most malignant liver diseases in the world, and the 5-year survival rate of such patients is low. Analgesics are often used to cure pain prevalent in liver cancer. The expression changes and clinical significance of the analgesic targets (ATs) in liver cancer have not been deeply understood.

OBJECTIVE

The purpose of this study is to clarify the expression pattern of ATs gene in liver cancer and its clinical significance. Through the comprehensive analysis of transcriptome data and clinical parameters, the prognosis model related to ATs gene is established, and the drug information sensitive to ATs is mined.

METHODS

The study primarily utilized transcriptomic data and clinical information from liver cancer patients sourced from The Cancer Genome Atlas (TCGA) database. These data were employed to analyze the expression of ATs, conduct survival analysis, gene set variation analysis (GSVA), immune cell infiltration analysis, establish a prognostic model, and perform other bioinformatic analyses. Additionally, data from liver cancer patients in the International Cancer Genome Consortium (ICGC) were utilized to validate the accuracy of the model. Furthermore, the impact of analgesics on key genes in the prognostic model was assessed using data from the Comparative Toxicogenomics Database (CTD).

RESULTS

The study investigated the differential expression of 58 ATs genes in liver cancer compared to normal tissues. Patients were stratified based on ATs expression, revealing varied survival outcomes. Functional enrichment analysis highlighted distinctions in spindle organization, centrosome, and spindle microtubule functions. Prognostic modeling identified low TP53 expression as protective, while elevated CCNA2, NEU1, and HTR2C levels posed risks. Commonly used analgesics, including acetaminophen and others, were found to influence the expression of these genes. These findings provide insights into potential therapeutic strategies for liver cancer and shed light on the molecular mechanisms underlying its progression.

CONCLUSIONS

The collective analysis of gene signatures associated with ATs suggests their potential as prognostic predictors in hepatocellular carcinoma patients. These findings not only offer insights into cancer therapy but also provide novel avenues for the development of indications for analgesics.

Role of eicosanoids in liver repair, regeneration and cancer

Eicosanoids are lipid signaling molecules derived from the oxidation of ω-6 fatty acids, usually arachidonic acid. There are three major pathways, including the cyclooxygenase (COX), lipoxygenase (LOX), and P450 cytochrome epoxygenase (CYP) pathway. Prostanoids, which include prostaglandins (PG) and thromboxanes (Tx), are formed via the COX pathway, leukotrienes (LT) and lipoxins (LX) by the action of 5-LOX, and hydroxyeicosatetraenoic acids (HETEs) and epoxyeicosatrienoic acids (EETs) by CYP. Although eicosanoids are usually associated with pro-inflammatory responses, non-classic eicosanoids, as LX, have anti-inflammatory and pro-resolving properties. Eicosanoids like PGE₂, LTB₄ and EETs have been involved in promoting liver regeneration after partial hepatectomy. PGE₂ and LTB₄ have also been reported to participate in the regenerative phase after ischemia and reperfusion (I/R), while cysteinyl leukotrienes (Cys-LT) contribute to the inflammatory process associated with I/R and are also involved in liver fibrosis and cirrhosis. However, LX, another product of 5-LOX, have the opposite effect, acting as pro-resolving mediators in these pathologies. In liver cancer, most studies show that eicosanoids, with the exception of LX, promote the proliferation of hepatocellular carcinoma cells and favor metastasis. This review summarizes the synthesis of different eicosanoids in the liver and discusses key findings from basic research linking eicosanoids to liver repair, regeneration and cancer and the impact of targeting eicosanoid cascade. In addition, studies in patients are presented that explore the potential use of eicosanoids as biomarkers and show correlations between eicosanoid production and the course and prognosis of liver disease.

Hepatic cyclooxygenase-2 overexpression induced spontaneous hepatocellular carcinoma formation in mice

Cyclooxygenase (COX)-2 is upregulated in hepatocellular carcinoma (HCC). However, the direct causative effect of COX-2 in spontaneous HCC formation remains unknown. We thus investigate the role and molecular pathogenesis of COX-2 in HCC by using liver-specific COX-2 transgenic (TG) mice. We found spontaneous HCC formation with elevated inflammatory infiltrates and neovessels in male TG mice (3/21, 14.3%), but not in any of male WT mice (0/19). Reduced representation bisulfite sequencing (RRBS) and gene expression microarrays were performed in the HCC tumor and non-HCC liver tissues to investigate the molecular mechanisms of COX-2-driven HCC. By RRBS, DNA promoter hypermethylation was identified in HCC from TG mice. Induction of promoter hypermethylation was associated with reduced tet methylcytosine dioxygenase 1 (TET1) expression by COX-2. TET1 could catalyze the conversion of 5-methylcytosine into 5-hydroxymethylcytosine (5hmC) and prevents DNA hypermethylation. In keeping with this, loss of 5hmC was demonstrated in COX-2-induced HCC. Consistently, COX-2 overexpression in human HCC cell lines could reduce both TET1 expression and 5hmc levels. Integrative analyses of DNA methylation and gene expression profiles further identified significantly downregulated genes including LTBP1, ADCY5 and PRKCZ by promoter methylation in COX-2-induced HCC. Reduced expression of LTBP1, ADCY5 and PRKCZ by promoter hypermethylation was further validated in human HCCs. Bio-functional investigation revealed that LTBP1 inhibited cell proliferation in HCC cell lines, suggesting its potential role as a tumor suppressor in HCC. Gene expression microarrays revealed that signaling cascades (AKT (protein kinase B), STK33 (Serine/Threonine kinase 33) and MTOR (mechanistic target of rapamycin) pathways) were enriched in COX-2-induced HCC. In conclusion, this study demonstrated for the first time that enhanced COX-2 expression in hepatocytes is sufficient to induce HCC through inducing promoter hypermethylation by reducing TET1, silencing tumor-suppressive genes and activating key oncogenic pathways. Inhibition of COX-2 represents a mechanism-based target for HCC prevention.

Betulinic acid exerts anti-hepatitis C virus activity via the suppression of NF-κB- and MAPK-ERK1/2-mediated COX-2 expression

BACKGROUND AND PURPOSE

This study was designed to evaluate the effect of betulinic acid (BA), extracted from Avicennia marina, on the replication of hepatitis C virus (HCV) and to investigate the mechanism of this BA-mediated anti-HCV activity.

EXPERIMENTAL APPROACH

HCV replicon and infectious systems were used to evaluate the anti-HCV activity of BA. Exogenous COX-2 or knock-down of COX-2 expression was used to investigate the role of COX-2 in the anti-HCV activity of BA. The effects of BA on the phosphorylation of NF-κB and on kinases in the MAPK signalling pathway were determined. The anti-HCV activity of BA in combination with other HCV inhibitors was also determined to assess its use as an anti-HCV supplement.

KEY RESULTS

BA inhibited HCV replication in both Ava5 replicon cells and in a cell culture-derived infectious HCV particle system. Treatment with a combination of BA and IFN-α, the protease inhibitor telaprevir or the NS5B polymerase inhibitor sofosbuvir resulted in the synergistic suppression of HCV RNA replication. Exogenous overexpression of COX-2 gradually attenuated the inhibitory effect of BA on HCV replication, suggesting that BA reduces HCV replication by suppressing the expression of COX-2. In particular, BA down-regulated HCV-induced COX-2 expression by reducing the phosphorylation of NF-κB and ERK1/2 of the MAPK signalling pathway.

CONCLUSIONS AND IMPLICATIONS

BA inhibits HCV replication by suppressing the NF-κB- and ERK1/2-mediated COX-2 pathway and may serve as a promising compound for drug development or as a potential supplement for use in the treatment of HCV-infected patients.

Correlation of microRNA-16, microRNA-21 and microRNA-101 expression with cyclooxygenase-2 expression and angiogenic factors in cirrhotic and noncirrhotic human hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is a classical example of inflammation-linked cancer and is characterized by hypervascularity suggesting rich angiogenesis. Cycloxygenase-2 (COX-2) is a potent mediator of inflammation and is considered to upregulate angiogenesis. The aims of the study are (1) to analyze expression of Cox-2 mRNA, Cox-2 protein, miR-16, miR-21 and miR-101 in HCC and adjacent liver parenchyma in cirrhotic and noncirrhotic liver, (2) to investigate the relation between COX-2 expression, miR-21 expression and angiogenic factors in these tissues and (3) to investigate the association between miR-16 and miR-101 and COX-2 expression.

METHODS

Tissue samples of HCC and adjacent liver parenchyma of 21 noncirrhotic livers and 20 cirrhotic livers were analyzed for COX-2 expression at the mRNA level (qRT-PCR) and at the protein level by Western blot and immunohistochemistry. Gene expression of VEGFA, VEGFR1, VEGFR2, Ang-1, Ang-2 and Tie-2 were correlated with COX-2 levels. miR-16, miR-21 and miR-101 gene expression levels were quantified in HCC tumor tissue.

RESULTS

COX-2 mRNA and protein levels were lower in HCC as compared to adjacent liver parenchyma both in cirrhotic and noncirrhotic liver. COX-2 protein localized mainly in vascular and sinusoidal endothelial cells and in Kupffer cells. At the mRNA level but not at the protein level, COX-2 correlated with mRNA levels of angiogenic factors VEGFR1, Ang-1, and Tie2. miR-21 expression was higher in cirrhotic tissues versus noncirrhotic tissues. MiR-101 expression was lower in cirrhotic versus noncirrhotic adjacent liver parenchyma. None of the miRNAs correlelated with COX-2 expression. miR-21 correlated negatively with Tie-2 receptor in adjacent liver parenchyma.

CONCLUSIONS

In human HCC, COX-2 mRNA but not COX-2 protein levels are associated with expression levels of angiogenic factors. MiR-21 levels are not associated with angiogenic molecules. MiR-16 and miR-101 levels do not correlate with COX-2 mRNA and protein levels.

COX-2 polymorphisms -765G→C and -1195A→G and hepatocellular carcinoma risk

Cyclooxygenase-2 (COX-2) is overexpressed in hepatocellular carcinoma (HCC) and considered to play a role in hepatic carcinogenesis. Our aim was to examine the associations between polymorphisms in COX-2 -765G→C and -1195A→G and risk of HCC. We conducted a case-control study including 120 patients with HCC and 130 age- and gender-matched controls. Genotypes of the COX-2 polymorphisms -765G→C and -1195A→G were determined by polymerase chain reaction-based restriction fragment length polymorphism. No significant difference was observed in the genotype distribution of the -765G→C polymorphism between patients and controls. The -1195AA genotype was associated with an increased risk of developing HCC (OR, 2.5; 95%CI, 1.18-5.37). The A allele was present significantly more often in HCC patients (OR 1.5; 95%CI, 1.05-2.14). In conclusion, our results demonstrated that the -1195AA genotype and A allele have an important role in HCC risk in Egyptian patients.

Overexpression of cyclooxygenase-2 and transforming growth factor-beta 1 is an independent predictor of poor virological response to interferon therapy in chronic HCV genotype 4 patients

BACKGROUND/AIMS

COX-2 and TGF-β1 are overexpressed in hepatitis C virus (HCV) infection and are related to hepatitis pathogenesis and hepatic fibrosis. The current study investigated the relationship between pretreatment COX-2 and TGF-β1 hepatic expression in HCV genotype 4 and the virological response to interferon therapy.

PATIENTS AND METHODS

Liver biopsies of 55 patients with HCV infection genotype 4 were selected together with 10 liver biopsies as control. The patients' clinicopathological data were collected. Immunohistochemistry was done using anti-COX-2 and anti-TGF-β1 antibodies. Statistical tests were used to determine the association between both COX-2 and TGF-β1 expression in relation to clinicopathological parameters and response to interferon therapy.

RESULTS

COX-2 was upregulated especially in nonresponders and was an independent predictor of poor virological response. However, COX-2 showed no association with other clinicopathological features. TGF-β1 was upregulated and associated with nonresponders, histological activity, and fibrosis stage. There was no association between TGF-β1 and other clinicopathological features. There was an association between COX-2 and TGF-β1 immunoexpression.

CONCLUSION

Overexpression of COX-2 and TGF-β1 is an independent predictor for poor outcome of interferon and ribavirin therapy and these might be useful markers for the response to treatment. Both molecules are associated together; however, their role during hepatitis treatment has to be clarified.

Cyclooxygenase-2 and vascular endothelial growth factor in chronic hepatitis, cirrhosis and hepatocellular carcinoma

Background/Aims

Cyclooxygenase-2 (COX-2) and vascular endothelial growth factor (VEGF) are up-regulated in hepatocellular carcinoma (HCC). To investigate the levels of COX-2 and VEGF expression in chronic hepatitis (CH), cirrhosis, and HCC.

Methods

The immunohistochemical expressions of COX-2 and VEGF were evaluated in tissues from patients with CH (n=95), cirrhosis (n=38), low-grade HCC (LG-HCC; n=6), and high-grade HCC (HG-HCC; n=29).

Results

The COX-2 expression scores in CH, cirrhosis, LG-HCC, and HG-HCC were 3.3±1.9 (mean±SD), 4.2±1.7, 5.5±1.0, and 3.4±2.4, respectively (CH vs. cirrhosis, P=0.016; CH vs. LG-HCC, P=0.008; LG-HCC vs. HG-HCC, P=0.004), and the corresponding VEGF expression scores were 0.9±0.8, 1.5±0.7, 1.8±0.9, and 1.6±1.1 (CH vs. cirrhosis, P<0.001; CH vs. LG-HCC, P=0.011; LG-HCC vs. HG-HCC, P=0.075). Both factors were correlated with the fibrosis stage in CH and cirrhosis (COX-2: r=0.427, P<0.001; VEGF: r=0.491, P<0.001). There was a significant correlation between COX-2 and VEGF in all of the tissue samples (r=0.648, P<0.001), and between high COX-2 and VEGF expression scores and survival (COX-2: P=0.001; VEGF: P<0.001).

Conclusions

The expressions of both COX-2 and VEGF are significantly higher in cirrhosis and LG-HCC than in CH. High COX-2 and high VEGF expressions are associated with a high survival rate.

Evaluation of epigenetic modulation of cyclooxygenase-2 as a prognostic marker for hepatocellular carcinoma

Cyclooxygenases (COX-1 and 2) catalyze the first step in prostanoid biosynthesis. They are implicated in homeostatic processes with an important role in inflammation and carcinogenesis. In the liver, COX-2 expression is restricted to proliferation or dedifferentiation situations. The COX-2 promoter contains numerous CpG islands that, when hypermethylated, result in transcriptionally silencing thus regulating the growth of carcinoma cells. In this work, we investigated whether a correlation exists between COX-2 expression and methylation signatures at the 5'region of the gene in hepatoma cell lines and human hepatocellular carcinoma (HCC). We also examined the acetylation status of the COX-2 promoter and the effects of histone deacetylase (HDAC) inhibitors on COX-2 expression. Our results suggest a significant association between reduced COX-2 expression and promoter hypermethylation of COX-2 and histone deacetylation in some hepatoma cell lines and in HCC. Treatment with demethylating agents or HDAC inhibitors restored the expression of COX-2. Moreover, in an HCC cohort, a statistically significant inverse association was observed between COX-2 mRNA levels and promoter methylation. In agreement with these data, a reduction of overall survival of the patients was observed after decreased COX-2 expression by promoter hypermethylation and histone H3 hypoacetylation.

Reciprocal regulation of NADPH oxidases and the cyclooxygenase-2 pathway

The objective of this work was to analyze the possible association between cyclooxygenase-2 (COX-2) and NADPH oxidases (NOX) in liver cells, in response to various proinflammatory and toxic insults. First, we observed that treatment of Chang liver (CHL) cells with various COX-2 inducers increased reactive oxygen species (ROS) production concomitant with GSH depletion, phorbol 12-myristate 13-acetate (PMA) being the most effective treatment. Moreover, early changes in the oxidative status induced by PMA were inhibited by glutathione ethyl ester, which also impeded COX-2 induction. In fact, CHL cells expressed NOX1 and NOX4, although only NOX4 expression was up-regulated in the presence of PMA. Knock-down experiments suggested that PMA initiated a pathway in which NOX1 activation controlled COX-2 expression and activity, which, in turn, induced NOX4 expression by activation of the prostaglandin receptor EP4. In addition, CHL cells overexpressing COX-2 showed higher NOX4 expression and ROS content, which were decreased in the presence of the COX-2 inhibitor DFU. Interestingly, we found that addition of prostaglandin E(2) (PGE(2)) also induced NOX4 expression and ROS production, which might promote cell adhesion. Finally, we determined that NOX4 induction by PGE(2) was dependent on ERK1/2 signaling. Taken together, these results indicate that NOX proteins and COX-2 are reciprocally regulated in liver cells.

Cyclooxygenase-2 gene promoter polymorphisms affect susceptibility to hepatitis C virus infection and disease progression

AIM

  Because polymorphisms of cyclooxygenase-2 (COX-2) and osteopontin (OPN) promoter regions and a promoter/enhancer region of forkhead box protein 3 (FOXP3) gene are known to affect immune responses, we examined whether these polymorphisms can influence susceptibility to hepatitis C virus (HCV) infection and progression of liver disease.

METHODS

  Peripheral blood samples were obtained from 104 Japanese patients with chronic HCV infection and 74 healthy Japanese donors. Polymerase chain reaction single-stranded conformational polymorphism analysis of genomic DNA was performed to determine the polymorphisms.

RESULTS

  The risk of persistent HCV infection was decreased in subjects with -1195GG genotype of the COX-2 promoter region. However, in patients with chronic HCV infection, the -1195GG genotype was associated with advanced-stage liver disease. A luciferase reporter assay performed to analyze the effect of single nucleotide polymorphisms (SNP) (-1195A or -1195G) in COX-2 gene on transcriptional activity using the HepG2, Huh7 and HeLa cell lines indicated that the -1195G genotype showed higher transcriptional activity than the -1195A genotype. SNP of OPN and FOXP3 did not differ between patients with chronic HCV infection and controls. However, the -443TT genotype of the OPN promoter region was associated with increased inflammatory activity of the liver.

CONCLUSION

  These results suggest that the -1195GG genotype of the COX-2 promoter region protects against HCV infection in the Japanese. However, once chronic infection is established, the -443TT genotype of the OPN promoter region and the -1195GG genotype of the COX-2 promoter are thought to promote inflammation and contribute to the progression of liver disease.

Increased expression of cyclooxygenase-2 is associated with the progression to cirrhosis

BACKGROUND/AIMS

To investigate the degree of cyclooxygenase-2 (COX-2) protein expression in chronic hepatitis and cirrhosis.

METHODS

COX-2 protein expression was evaluated in 43 cases of chronic hepatitis and 24 cases of cirrhosis using immunohistochemical techniques. The COX-2 immunohistochemical staining score was assessed using the scoring systems of Pazirandeh et al and Qiu et al. and each scoring system was based on a sum of the parameters of staining intensity and distribution.

RESULTS

The mean COX-2 expression scores in chronic hepatitis and cirrhosis were 2.5 ± 1.3 vs. 3.3 ± 1.1 (p = 0.008), and 3.2 ± 2.0 vs. 4.5 ± 1.7 (p = 0.006), respectively, based on the Pazirandeh et al. and Qiu et al. scoring systems. The percentage samples of high COX-2 expression score (4 to 5) in chronic hepatitis and cirrhosis were 16.3% vs. 45.8% (p = 0.022), and 23.3% vs. 50% (p = 0.021), respectively, based on the two scoring systems. The mean COX-2 expression scores based on the severity of hepatic fibrosis scored using Ishak's modified staging system (fibrosis score 0 to 3 vs. 4 to 6) were 2.4 ± 1.3 vs. 3.2 ± 1.1 (p = 0.009), and 3.1 ± 2.0 vs. 4.3 ± 1.8 (p = 0.009), respectively, based on the two scoring systems.

CONCLUSIONS

COX-2 expression was significantly higher in liver cirrhosis group than in chronic hepatitis. COX-2 expression scores according to Ishak's staging was significantly higher in the advanced fibrosis group. COX-2 may play a role in the progression of hepatic fibrosis.

Overexpression of cyclooxygenase-2 in noncancerous liver tissue increases the postoperative recurrence of hepatocellular carcinoma in patients with hepatitis B virus-related cirrhosis

BACKGROUND

Many previous studies have evaluated the histopathological features of tumours as risk factors for postoperative recurrence in hepatitis B virus (HBV)-associated hepatocellular carcinoma (HCC). However, there have been few large studies investigating the relationship between cyclooxygenase-2 (COX-2) expression in noncancerous regions of the liver and postoperative recurrence in the remnant liver, especially in HBV-related HCC.

OBJECTIVE

To evaluate the significance of COX-2 expression levels in noncancerous liver regions as a prognostic indicator of HCC in patients with HBV-related cirrhosis.

METHODS

A total of 124 patients who underwent curative resection for HCC were reviewed retrospectively. Immunohistochemistry was used to evaluate the expression of COX-2 in noncancerous liver tissue. Clinicopathological variables were compared between patients with high COX-2 expression (n=58 [COX-2-positive group]) and patients with low COX-2 expression (n=66; [COX-2-negative group]). Univariate and multivariate analyses were performed to identify factors that affected disease recurrence.

RESULTS

There was a significant correlation between COX-2 expression and alanine aminotransferase levels and vascular invasion. The recurrence-free survival rates in the COX-2-positive group were significantly lower than the rates in the COX-2-negative group. On multivariate analysis, the overexpression of COX-2 in noncancerous liver regions was found to be an unfavourable prognostic indicator for the recurrence of HCC.

CONCLUSIONS

The results of the current study suggest that overexpression of COX-2 in noncancerous liver regions is an independent and significant indicator predictive of early recurrence of HCC in patients with HBV-related cirrhosis.

Transgenic expression of cyclooxygenase-2 in hepatocytes accelerates endotoxin-induced acute liver failure

Bacterial LPS (endotoxin) is implicated in the pathogenesis of acute liver failure and several chronic inflammatory liver diseases. To evaluate the effect of hepatocyte cyclooxygenase (COX)-2 in LPS-induced liver injury, we generated transgenic mice with targeted expression of COX-2 in the liver by using the albumin promoter-enhancer driven vector and the animals produced were subjected to a standard experimental protocol of LPS-induced acute fulminant hepatic failure (i.p. injection of low dose of LPS in combination with d-galactosamine (d-GalN)). The COX-2 transgenic mice exhibited earlier mortality, higher serum aspartate aminotransferase and alanine aminotransferase levels and more prominent liver tissue damage (parenchymal hemorrhage, neutrophilic inflammation, hepatocyte apoptosis, and necrosis) than wild-type mice. Western blot analysis of the liver tissues showed that LPS/d-GalN treatment for 4 h induced much higher cleavage of poly(ADP-ribose) polymerase, caspase-3, and caspase-9 in COX-2 transgenic mice than in wild-type mice. Increased hepatic expression of JNK-2 in COX-2 transgenic mice suggest that up-regulation of JNK-2 may represent a potential mechanism for COX-2-mediated exacerbation of liver injury. Blocking the prostaglandin receptor, EP(1), prevented LPS/d-GalN-induced liver injury and hepatocyte apoptosis in COX-2 transgenic mice. Accordingly, the mice with genetic ablation of EP(1) showed less LPS/d-GalN-induced liver damage and less hepatocyte apoptosis with prolonged survival when compared with the wild-type mice. These findings demonstrate that COX-2 and its downstream prostaglandin receptor EP(1) signaling pathway accelerates LPS-induced liver injury. Therefore, blocking COX-2-EP(1) pathway may represent a potential approach for amelioration of LPS-induced liver injury.

Constitutive expression of cyclo-oxygenase 2 transgene in hepatocytes protects against liver injury

The effect of COX (cyclo-oxygenase)-2-dependent PGs (prostaglandins) in acute liver injury has been investigated in transgenic mice that express human COX-2 in hepatocytes. We have used three well-established models of liver injury: in LPS (lipopolysaccharide) injury in D-GalN (D-galactosamine)-preconditioned mice; in the hepatitis induced by ConA (concanavalin A); and in the proliferation of hepatocytes in regenerating liver after PH (partial hepatectomy). The results from the present study demonstrate that PG synthesis in hepatocytes decreases the susceptibility to LPS/D-GalN or ConA-induced liver injury as deduced by significantly lower levels of the pro-inflammatory profile and plasmatic aminotransferases in transgenic mice, an effect suppressed by COX-2-selective inhibitors. These Tg (transgenic) animals express higher levels of anti-apoptotic proteins and exhibit activation of proteins implicated in cell survival, such as Akt and AMP kinase after injury. The resistance to LPS/D-GalN-induced liver apoptosis involves an impairment of procaspase 3 and 8 activation. Protection against ConA-induced injury implies a significant reduction in necrosis. Moreover, hepatocyte commitment to start replication is anticipated in Tg mice after PH, due to the expression of PCNA (proliferating cell nuclear antigen), cyclin D1 and E. These results show, in a genetic model, that tissue-specific COX-2-dependent PGs exert an efficient protection against acute liver injury by an antiapoptotic/antinecrotic effect and by accelerated early hepatocyte proliferation.

Elucidation of the role of COX-2 in liver fibrogenesis using transgenic mice

Hepatic COX-2 overexpression is sufficient to induce hepatitis, but its role on liver fibrosis remains unknown. We aim to elucidate possible biological effects of COX-2 in liver fibrosis using both gain-of-function and loss-of-function mouse models. COX-2 transgenic (TG) mice that specifically overexpress the human COX-2 cDNA in the liver, knockout (KO), and wild type (WT) mice were studied in two different murine fibrosis models induced by carbon tetrachloride (CCl(4)) injection or methionine and choline-deficient (MCD) diet. Liver injury was assessed by serum ALT and bilirubin levels and histological examination. Hepatic collagen content was determined by picrosirius red stain morphometry assay and quantitation of hydroxyproline. Hepatic stellate cell (HSC) activation was determined by immunohistochemical analysis of alpha-smooth muscle actin (alpha-SMA). mRNA expression of fibrogenic genes was assayed by real-time quantitative PCR. COX-2 protein was overexpressed in the liver of TG mice compared with WT littermates. CCl(4) or MCD-induced liver fibrotic injury was equally severe in TG and WT mice, as demonstrated by similar elevated levels of hepatic collagen contents. Enhanced COX-2 expression in TG liver did not affect HSC activation and fibrogenic gene expression upon CCl(4) or MCD treatment. Importantly, CCl(4)-treated KO mice did not show significant difference in liver fibrotic damage and fibrogenic gene expression compared with the WT counterparts. This is the first report on the effect of COX-2 in liver fibrosis based on genetic mouse models. The results suggest that COX-2 does not appear to mediate the development of liver fibrosis.

Response to antiviral therapy and hepatic expression of cyclooxygenases in chronic hepatitis C

OBJECTIVES

The aims of this study were to investigate the expression of cyclooxygenase-1 and cyclooxygenase-2 (COX-1 and COX-2) in chronic hepatitis C (CHC) by immunohistochemistry, based on the hypothesis that COXs expression could vary according to genotype, viral load, liver steatosis, BMI and response to therapy and to determine whether the addition of selective COX inhibitors could have a rationale in increasing the efficacy of antiviral therapy.

METHODS

We used 35 formalin-fixed, paraffin-embedded liver tissue samples obtained by needle biopsy from patients with CHC (17F/18M) with one of two types of genotype (1b and 3a). The presence of COX-1 and COX-2 in the cytoplasm of hepatocytes was scored on the basis of: (i) maximum intensity; (ii) dominant intensity; and (iii) extent.

RESULTS

No significant differences were found in COX-1 and COX-2 expression in CHC patients divided according to genotype or according to the type of response to combination therapy with pegylated-interferon and ribavirin. The only significant correlations were observed between the dominant intensity of COX-2 and the presence of histological steatosis (P<0.01) and an inverse correlation between COX-2 extent and the viral load (P<0.02).

CONCLUSIONS

The lack of correlation between COXs tissue expression and response to antiviral treatment suggests that there is no rationale to adding selective COX inhibitors to increase the efficacy of antiviral therapy, although further studies on larger patient populations are needed. On the contrary, there is a potential application for their use in the prevention and treatment of liver steatosis.

Cyclooxygenase-2 expression in chronic hepatitis C and the effect of interferon alpha treatment

BACKGROUND AND AIM

Cyclooxygenase-2 (COX-2), a target of aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs), is upregulated in chronic hepatitis B and may have a role in hepatocellular carcinoma. Little is known about the expression of COX-2 in chronic hepatitis C (HCV) infection. The aim the present study was to evaluate the extent of COX-2 expression in liver biopsies in patients with HCV infection and to determine the effect of treatment with interferon alpha (IFN).

METHODS

Percutaneous liver biopsy specimens were retrieved. Following formalin fixation and paraffin embedding, the biopsies were histologically evaluated for inflammation and fibrosis. The extent of COX-2 expression was measured by the avidin biotin immunohistochemical technique using a monoclonal COX-2 antibody. The extent of COX-2 expression was graded according to the number of hepatocytes expressing COX-2. Data were analyzed using Student's t-test.

RESULTS

Liver biopsies from 10 patients before and after treatment with IFN were obtained and compared with nine normal liver biopsies. All of the liver biopsies showed some COX-2 expression. COX-2 expression was confined to hepatocytes and bile duct epithelium and was not detected in vascular endothelium or inflammatory cells. The extent of COX-2 expression was greater in hepatitis C infected liver biopsies than in normal biopsies. Following treatment with IFN, there was a greater than threefold reduction in COX-2 expression (P < 0.01). This result was independent of the sustained virological response.

CONCLUSION

In this small pilot study we have shown that COX-2 is overexpressed in liver biopsies infected with HCV and COX-2 expression is reduced following treatment with IFN.

Overexpressed cyclo-oxygenase-2 in the background liver is associated with the clinical course of hepatitis C virus-related cirrhosis patients after curative surgery for hepatocellular carcinoma

BACKGROUND

The probable role of cyclo-oxygenase-2 (COX-2) in the development of hepatocellular carcinoma (HCC) in patients with chronic liver diseases has been accepted to be relevant. The purpose of the present study was to determine whether overexpressed COX-2 in the background liver affects the clinical course of hepatitis C virus (HCV)-related cirrhosis patients after curative surgery for HCC.

METHODS

Twenty-nine clinical stage I HCC patients with HCV-related cirrhosis, who underwent curative surgery, were enrolled in the present study (22 men and seven women, age range 53-73 years; follow-up period; range 22-159 months, median 61 months). The COX-2 expression in the cirrhotic liver was examined by immunohistochemistry using the avidin-biotin-peroxidase complex technique on paraffin-embedded formalin-fixed tissue. The COX-2 expression was scored, then correlated with monitored alanine aminotransferase (ALT) levels during the follow-up period after surgery, response to alternative therapy aiming to improve elevated ALT levels, and recurrence/survival after surgery.

RESULTS

The COX-2 expression scores were significantly higher in the high-ALT group than in the low-ALT group (Mann-Whitney, P = 0.010), and were significantly higher in non-responders to the alternative therapy than in responders (Mann-Whitney, P = 0.028). The higher COX-2 expression in the cirrhotic liver was the significant independent risk factor for residual liver recurrence (Cox multivariate analysis, P = 0.014), but not for survival.

CONCLUSIONS

Overexpressed COX-2 in the background liver may play an important role in prolonged acceleration of necroinflammation, resistance to the alternative therapy, and recurrence/new development of HCC in HCV-related cirrhosis patients.

Protection against Fas-induced liver apoptosis in transgenic mice expressing cyclooxygenase 2 in hepatocytes

Cyclooxygenase-2 (COX-2) is upregulated in many cancers, and the prostanoids synthesized increase proliferation, improve angiogenesis, and inhibit apoptosis in several tissues. To explore the function of COX-2 in liver, transgenic (Tg) mice were generated containing a fusion gene (LIVhCOX-2) consisting of human COX-2 cDNA under the control of the human ApoE promoter. Six lines were developed; all of them expressed the LIVhCOX-2 transgene selectively in hepatocytes. The Tg mice exhibited a normal phenotype, and the increased levels of PGE2 found were due to the constitutively expressed COX-2. Histological analysis of different tissues and macroscopic examination of the liver showed no differences between wild-type (Wt) and Tg animals. However, Tg animals were resistant to Fas-mediated liver injury, as demonstrated by low levels of plasmatic aminotransferases, a lesser caspase-3 activation, and Bax levels and an increase in Bcl-2, Mcl-1, and xIAP proteins, when compared with the Wt animals. Moreover, the resistance to Fas-mediated apoptosis is suppressed in the presence of COX-2-selective inhibitors, which prevented prostaglandin accumulation in the liver of Tg mice.

CONCLUSION

These results demonstrate that expression of COX-2-dependent prostaglandins exerted a protection against liver apoptosis.

Potential involvement of the cyclooxygenase-2 pathway in hepatocellular carcinoma-associated angiogenesis

Angiogenesis plays a crucial role in tumor development and growth. The present study was carried out to investigate the potential involvement of the cyclooxygenase-2 (Cox-2) pathway in the regulation of angiogenesis in hepatocellular carcinoma (HCC). We inhibited Cox-2 expression in HCC cell line HuH-7 by selective Cox-2 inhibitor (SC-58635) or Cox-2 siRNA. Conditioned media (CMs) from HuH-7 cells were used in angiogenic assays in vitro and in vivo. Compared with CMs from untreated and negative siRNA treated HuH-7 cells, CMs from SC-58635 and Cox-2 siRNA treated HuH-7 dramatically suppressed the proliferation, migration, and differentiation of human umbilical vein endothelial cells (HUVECs) in vitro and neovascularization in vivo. These inhibitory effects could be partially reversed by the addition of exogenous PGE2 to CMs. Furthermore, Cox-2 inhibition by SC-58635 resulted in PGE2 reduction accompanied by the down-regulation of four PGE2 receptor (EP receptor) subtypes. Treatment with SC-58635 led to the down-expression of proangiogenic factors such as VEGF, HGF, FGF2, ANGPT1 and ANGPT2 in HCC. An approximately 78% reduction of VEGF level has been found in the CM from SC-58635 treated HuH-7. Our results suggest an involvement of Cox-2 in the control of HCC-associated angiogenesis. PGE2 as a vital angiogenic factor may act directly on endothelial cells to promote HuH-7-stimulated angiogenic process. Moreover, Cox-2/PGE2/EP/VEGF pathway possibly also contributes to tumor angiogenesis in HCC. This study provides the rationale for clinical studies of Cox-2 inhibitors on the treatment or chemoprevention of HCC.

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.

The significance of cyclooxygenase-2 expression in human hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the five most common malignancies in the world and is the second leading cause of death in Hong Kong. Previous studies have shown increased levels of cyclooxygenase-2 (COX-2) in a variety of human malignancies including HCC, suggesting that abnormal COX-2 expression plays an important role in carcinogenesis. In addition, some evidence suggests that selective COX-2 inhibitors suppress the formation of tumors in experimental models. However, there are no data in the literature on using COX-2 as an inhibitor target in HCC. The main objective of this article was to give a brief summary of the recent findings of the role of COX-2 in HCC. We briefly reviewed the significance of COX-2 in varies cancers, and then focused on the recent findings of the significance of COX-2 in HCC. Finally, we further evaluated the possibility of using COX-2 as a therapeutic target in HCC.

Cyclooxygenase-2 in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth most common cancer and the third leading cause of cancer related mortality worldwide. The incidence of HCC is rising worldwide, especially in the United States. The overall survival of patients with HCC is grim and currently no efficient secondary prevention or systemic treatments are available. Recent evidence suggests that COX-2 signaling is implicated in hepatocarcinogenesis and COX-2 inhibitors prevent HCC cell growth in vitro and in animal models. However, given the recently reported side effect associated with some of the COX-2 inhibitors, it is imperative to develop chemotherapeutic strategy that simultaneously targets COX-2 and other related key molecules in hepatocarcinogenesis or to utilize agents inhibiting COX-2 signaling in conjunction with other standard chemotherapy or radiation therapy. Such combinational therapeutic approaches are expected to provide synergistic anti-tumor effect with lesser side effect. In this regard, the recently delineated interplay between COX-2-derived PG signaling and other growth-regulatory pathways such as EGFR, Met, iNOS, VEGF and n-3 polyunsaturated fatty acids is expected to provide important therapeutic implications. This review summarizes the recent advances in understanding the mechanisms for COX-2-derived PG signaling in hepatocarcinogenesis and focuses on the newly unveiled interactions between PG cascade and other key signaling pathways that coordinately regulate HCC growth. Understanding these mechanisms and interplays will facilitate the development of more effective chemopreventive and therapeutic strategies.

Tumor cyclooxygenase-2 levels correlate with tumor invasiveness in human hepatocellular carcinoma

AIM: Recent studies suggested that cyclooxygenase-2 (COX-2) enhances tumor angiogenesis via upregulation of vascular endothelial growth factor (VEGF). Although COX-2 expression has been demonstrated in hepatocellular carcinoma (HCC), the significance of COX-2 in progression of HCC remains unclear. This study evaluated the clinico-pathological correlation of COX-2 level and its relationship with VEGF level in HCC.

METHODS: Fresh tumor tissues were obtained from 100 patients who underwent resection of HCC. COX-2 protein expression was examined by immunohistochemistry, and quantitatively by an enzyme immunometric assay (EIA) of tumor cytosolic COX-2 levels. Tumor cytosolic VEGF levels were measured by an ELISA.

RESULTS: Immunostaining showed expression of COX-2 in tumor cells. Tumor cytosolic COX-2 levels correlated with VEGF levels (r = 0.469, P<0.001). Correlation with clinicopathological features showed significantly higher tumor cytosolic COX-2 levels in the presence of multiple tumors (P = 0.027), venous invasion (P = 0.030), microsatellite lesions (P = 0.037) and advanced tumor stage (P = 0.008). Higher tumor cytosolic COX-2 levels were associated with worse patient survival.

CONCLUSION: This study shows that elevated tumor COX-2 levels correlate with elevated VEGF levels and invasiveness in HCC, suggesting that COX-2 plays a significant role in the progression of HCC.

Distribution of constitutive (COX-1) and inducible (COX-2) cyclooxygenase in postviral human liver cirrhosis: a possible role for COX-2 in the pathogenesis of liver cirrhosis

AIMS

Prostaglandins produced by the action of cyclooxygenases (COX) are important mediators of systemic vasodilatation and inflammation in liver cirrhosis. The aim of this study was to investigate the distribution of COX-1 and COX-2 in postviral cirrhosis.

METHODS

The immunohistochemical expression of the constitutive (COX-1) and the inducible (COX-2) isoenzymes was investigated in 15 patients with cirrhosis after hepatitis B and C infection; three normal control livers were also analysed.

RESULTS

COX-2 was absent from normal liver but was highly expressed in cirrhosis, mainly in the inflammatory, sinusoidal, vascular endothelial, and biliary epithelial cells. Low amounts of COX-1 were expressed in both normal and cirrhotic livers, exclusively in sinusoidal and vascular endothelial cells, with no differences seen between normal and cirrhotic livers.

CONCLUSIONS

COX-2 is overexpressed in liver cirrhosis, and possibly contributes to prostaglandin overproduction, which may be a major component of the inflammation and hyperdynamic circulation associated with cirrhosis. Because COX-2 is thought to contribute to tumour development, high COX-2 production could be a contributor to hepatocellular carcinoma development in cirrhosis. The finding of COX-2 and not COX-1 upregulation in cirrhosis could provide a possible new role for selective COX-2 inhibitors in reducing inflammation and minimising the occurrence of hepatocellular carcinoma in patients with cirrhosis.

[Role of cyclooxygenase-2 in the pathogenesis of chronic liver diseases]

Cyclooxygenase (COX) is a crucial enzyme in the biosynthesis of prostaglandins. There are two COX isoforms: COX-1 is constitutively expressed in a number of cell types and is involved in the homeostatic functions of prostaglandins, whereas COX-2 is inducible by a variety of proinflammatory stimuli, such as cytokines and lipopolysaccharide. In the liver, COX-2 and prostaglandins production has been implicated in hepatic regeneration, liver matrix remodeling and portal hypertension. In animal models of alcoholic-induced liver disease has been demonstrated its relation with necro-inflammatory activity. In viral hepatitis, hepatocellular COX-2 expression was observed and associated with fibrosis progression. More interestingly it has been the demonstration of COX-2 role in the development of hepatocellular carcinoma and cholangiocarcinoma, such in experimental models as in human samples. It has also been demonstrated that COX-2 was implicated in carcinogenesis through apoptosis inhibition and increased proliferation of human tumor cells. Experimental evidences show that selective pharmacologic inhibition of COX-2 could be useful in chemoprevention of primary liver tumors.

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Hepatocellular carcinoma: is there a potential for chemoprevention using cyclooxygenase-2 inhibitors?

Inhibitors of cyclooxygenase-2 (COX-2) have proapoptotic and antiangiogenic effects on malignant tumors and inhibit their invasion to surrounding tissues. These properties are derived from COX-dependent and/or COX-independent signaling via peroxisome proliferator-activated receptor gamma. Although the role of COX-2 involvement in human hepatocarcinogenesis has not been determined yet, selective COX-2 inhibitors with COX-independent properties may potentially suppress hepatocarcinogenesis. This hypothesis should be confirmed in in vivo studies using animal models. These studies may provide insights into any application of the COX-2 inhibitor for primary and/or secondary chemoprevention.