Rationale and feasibility of chemoprovention of hepatocellular carcinoma by cyclooxygenase-2 inhibitors

A novel TLR4 accessory molecule drives hepatic oncogenesis through tumor-associated macrophages

Tumor-associated macrophages (TAMs) play a crucial role in the tumor microenvironment, yet the roles and mechanisms of TAMs in inflammation-associated oncogenesis remain enigmatic. We report that protein canopy homolog 2 (CNPY2) functions as a novel TLR4 regulator, promoting cytokine production in macrophages. CNPY2 binds directly to TLR4. Cnpy2 deficiency reduces cell surface expression of TLR4, nuclear translocation of NFκB and cytokine production in macrophages. Macrophage-specific CNPY2 deficiency significantly decreases cytokine production in macrophages and reduces hepatocarcinogenesis in a diethylnitrosamine (DEN)-induced liver cancer model. RNA-sequencing analysis revealed Cnpy2 knockout decreased the mRNA level and cell surface expression of two VEGF receptors, Flt1 and Kdr, compared to those in WT counterparts, resulting in inhibition of macrophage tumor infiltration. Cnpy2 knockout inhibits NFκB2/p52-mediated transcription of Flt1 and Kdr in macrophages. These findings demonstrate that CNPY2 regulates macrophages in both inflammation and hepatocarcinogenesis and may serve as a therapeutic target for cancer.

Association of aspirin and nonaspirin NSAIDs therapy with the incidence risk of hepatocellular carcinoma: a systematic review and meta-analysis on cohort studies

According to the current research evidence, the therapy of nonsteroidal anti-inflammatory drugs (NSAIDs) might effectively decrease the risk of hepatocellular carcinoma (HCC) incidence. Investigations have been conducted on the relationship between NSAIDs (aspirin and nonaspirin NSAIDs) and the risk of HCC incidence. We searched the PubMed, Web of Science, Embase and Cochrane Library databases for cohort studies published prior to 15 March 2020 and screened eligible studies. There were a total of 12 eligible studies (published between 2012 and 2020). We observed a lower risk of HCC among aspirin users [hazard ratio 0.53; 95% confidence interval (CI), 0.43-0.65]. However, there were no statistically significant associations discovered between nonaspirin NSAID use and the risk of HCC incidence (hazard ratio 0.95; 95% CI, 0.79-1.15). Furthermore, aspirin use has also been found to reduce the risk of HCC in patients with cirrhosis or viral hepatitis compared to that in the general population (hazard ratio 0.15; 95% CI, 0.10-0.23; hazard ratio 0.65; 95% CI, 0.56-0.76, respectively). Moreover, no statistical associations were found between aspirin use and a higher risk of bleeding risk, with a hazard ratio value of 0.76 (95% CI, 0.51-1.13). In summary, the conducted meta-analysis reveals that aspirin, rather than nonaspirin NSAIDs, can significantly decrease the risk of HCC, particularly in patients with cirrhosis or viral hepatitis.

Interdependent and independent multidimensional role of tumor microenvironment on hepatocellular carcinoma

The novelty of an effective therapeutic targeting for hepatocellular carcinoma (HCC) is based on improved understanding of each component of tumor microenvironment (TME) and its correspondent interactions at biological and molecular levels. In this context, new expansions for the treatment against TME and its communication with HCC are under exploration. Despite of the fact that blockage of growth factor receptors has become a treatment of choice in late phases of HCC in clinical practice, still a precise targeted treatment should address all the components of TME. Targeting one specific element out of cellular (cancer associated fibroblasts, endothelial cells, hepatic stellate cells, Kupffer cells and lymphocytes) or non-cellular (extracellular matrix, growth factors, inflammatory cytokines, proteolytic enzymes) parts of TME may not be a successful remedy for the disease because of well-designed hindrances of each component and their functional alternativeness. Meanwhile there are some elements of TME like epithelial-mesenchymal transition and CAF, which are considerably important and need thorough investigations. Ascertaining the potential role of these elements, and a single or combinational drug therapy targeting these elements of TME simultaneously, may provide the appreciable considerations to eventually improve in clinical practices and may also minimize the chances of reoccurrence of HCC.

Evaluation of Cytotoxicity Effects of Chalcone Epoxide Analogues as a Selective COX-II Inhibitor in the Human Liver Carcinoma Cell Line

Objectives

Study of the mechanisms involved in cancer progression suggests that cyclooxygenase enzymes play an important role in the induction of inflammation, tumor formation, and metastasis of cancer cells. Thus, cyclooxygenase enzymes could be considered for cancer chemotherapy. Among these enzymes, cyclooxygenase 2 (COX-2) is associated with liver carcinogenesis. Various COX-2 inhibitors cause growth inhibition of human hepatocellular carcinoma cells, but many of them act in the COX-2 independent mechanism. Thus, the introduction of selective COX-2 inhibitors is necessary to achieve a clear result. The present study was aimed to determine the growth-inhibitory effects of new analogues of chalcone epoxide as selective COX-2 inhibitors on the human hepatocellular carcinoma (HepG2) cell line.

Methods

Estimation of both cell growth and the amount of prostaglandin E2 (PGE2) production were used to study the effect of selective COX-2 inhibitors on the hepatocellular carcinoma cell. Cell growth determination has done by MTT assay in 24 h, 48 h and 72 h, and PGE2 production has estimated by using ELYSA kit in 48 h and 72 h.

Results

The results showed growth inhibition of the HepG2 cell line in a concentration and time-dependent manner, as well as a reduction in the formation of PGE2 as a product of COX-2 activity. Among the compounds those analogues with methoxy and hydrogen group showed more inhibitory effect than others.

Conclusion

The current in-vitro study indicates that the observed significant growth-inhibitory effect of chalcone-epoxide analogues on the HepG2 cell line may involve COX-dependent mechanisms and the PGE2 pathway parallel to the effect of celecoxib. It can be said that these analogues might be efficient compounds in chemotherapy of COX-2 dependent carcinoma specially preventing and treatment of hepatocellular carcinomas.

Toll-like receptors in pathophysiology of liver diseases

Toll-like receptors (TLRs) are pattern recognition receptors that participate in host defense by recognizing pathogen-associated molecular patterns alongside inflammatory processes by recognizing damage associated molecular patterns. Given constant exposure to pathogens from gut, strict control of TLR-associated signaling pathways is essential in the liver, which otherwise may lead to inappropriate production of pro-inflammatory cytokines and interferons and may generate a predisposition to several autoimmune and chronic inflammatory diseases. The liver is considered to be a site of tolerance induction rather than immunity induction, with specificity in hepatic cell functions and distribution of TLR. Recent data emphasize significant contribution of TLR signaling in chronic liver diseases via complex immune responses mediating hepatocyte (i.e., hepatocellular injury and regeneration) or hepatic stellate cell (i.e., fibrosis and cirrhosis) inflammatory or immune pathologies. Herein, we review the available data on TLR signaling, hepatic expression of TLRs and associated ligands, as well as the contribution of TLRs to the pathophysiology of hepatic diseases.

Downregulation of discoidin domain receptor 2 decreases tumor growth of hepatocellular carcinoma

PURPOSE

Discoidin domain receptors (DDRs) have been identified as tyrosine kinase receptors for collagen, and the overexpression of DDR1 was correlated with hepatocellular carcinoma (HCC) progression in vitro. Little is known about DDR2 on HCC cells, and we investigated the expression and function of DDR2 in human HCC cells.

METHODS

Expression of DDR2 in human HCC cell lines and patient HCC tissues was observed. The suppression of DDR2 by siRNA against DDR2 was performed in vitro and in vivo study.

RESULTS

All of HCC cell lines expressed DDR2 mRNA, and all HCC tissues from the ten patients with HCC demonstrated DDR2 mRNA expression. Transfection of DDR2 siRNA significantly inhibits cell growth compared to cells with nontarget siRNA transfection in vitro (P < 0.001). In SNU182, Hep3B, and HeLa cell xenograft models, there was a significant difference in average tumor volumes after 12 days of the DDR2 siRNA injection (P < 0.05) in SNU182 xenograft mice. DDR2 siRNA injection decreased the mean tumor volume by 65.6 % compared to that of the control. The apoptosis analysis demonstrated that DDR2 siRNA treatment significantly increased apoptotic cells (P < 0.01). Cell migration (P < 0.05) and cell invasion (P < 0.01) were significantly decreased by DDR2 siRNA treatment.

CONCLUSIONS

The inhibition of DDR2 by RNA interference suppressed in vivo and in vitro growth of human HCC cells. Our results may support that the use of DDR2 as a novel target of HCC treatment through control of tumor apoptosis, migration, and invasion.

18-β Glycyrrhetinic acid alleviates 2-acetylaminofluorene-induced hepatotoxicity in Wistar rats

2-Acetylaminofluorene (2-AAF) is a known hepatic carcinogen which leads to tumour formation in rodents. 18-β Glycyrrhetinic acid (18 β-GA) derived from liquorice plant has various pharmacological properties such as anti-ulcer, anti-inflammatory, antiviral, hepatoprotective and antioxidant. This study is designed to elucidate the chemopreventive properties of 18 β-GA against 2-AAF-induced liver toxicity in Wistar rats and evaluated its effect on inflammatory and tumour promotion marker and activities of different oxidative stress enzymes. Administration of 2-AAF at the dose of (50 mg/kg body weight (b.w.) intraperitoneally (i.p.)) for five consecutive days induces hepatic toxicity, inflammation, oxidative stress and hyperproliferation. Pretreatment with 18 β-GA at two different doses (45 and 75 mg kg−1 b.w.) significantly ameliorates 2-AAF-induced increased lipid peroxidation, alanine transaminase and aspartate transaminase, xanthine oxidase activities and activities of phase-II detoxifying enzymes along with the levels of glutathione content. Administration of 18 β-GA also significantly restored the expressions of proliferating cell nuclear antigen, cyclooxygenase 2, inducible nitric oxide synthase and nuclear factor κB. Furthermore, histological observations also support the preventive effects of 18 β-GA. Our findings suggest that pretreatment with 18 β-GA showed potential hepatoprotective effects via attenuation of oxidative stress, inflammation and hyperproliferation.

The effect of celecoxib on the development of diethylnitrosamine-induced liver tumors in rats

BACKGROUND/AIMS

Hepatocellular carcinoma is one of the most commonly diagnosed malignant tumors in the world, and it typically has a poor prognosis. Extensive studies have examined the effects of non-steroidal anti-inflammatory drugs selective to COX-2 on the chemoprevention of various tumors. The objective of this study is to observe the effect of celecoxib on the development of liver tumors in rats.

MATERIAL AND METHODS

Hepatocellular carcinoma was induced in a group of 75 rats with the carcinogen diethylnitrosamine. The animals were divided into 5 groups. Three groups received various doses of celecoxib, one group received indomethacin, and a control group received no non-steroidal selective anti inflammatory drugs.

RESULTS

The experimental model was considered to be successful because 78% of the rats in the control group developed liver tumors. The number of neoplastic lesions was similar among the celecoxib, indomethacin and control groups, although the nodule diameter of the lesions was smaller in the celecoxib group. Better results were observed in animals that received celecoxib at doses of 6 and 9 mg/kg/ day; 4 rats in these groups did not show any neoplastic histological lesions, and a greater proportion of the nodules in the other animals in these groups were benign than in the groups that did not use celecoxib.

CONCLUSIONS

These results suggest that celecoxib may play a role in modifying the natural history of hepatocellular carcinoma development.

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.

Elevated expression of complement C3 protein in chemically induced hepatotumorogenesis in Wistar rats: a correlative proteomics and histopathological study

Liver cancer remains the leading cause of cancer-related mortality worldwide. Early detection of liver cancer is problematic due to the lack of a marker with high diagnosis sensitivity and specificity. The present study was designed to determine the differently expressed proteins at early stage in the serum of animals with liver cancer vis-à-vis controls and figure out the function of the proteins. One-dimensional electrophoresis (1D), two-dimensional electrophoresis (2DE) and liquid chromatography mass spectrometry (LC-MS/MS) were used to screen the serum proteins of liver cancer induced in animals by diethyl nitrosamine (DEN)+2-acetyl amino fluorine (2-AAF). From optimized 2DE image and computer assisted PD Quest analysis were found to be differentially expressed spots when the serum from normal and treated animals were compared. Among these, one spot was selected whose expression level was higher in DEN+2-AAF treated animal sera than in adjacent normal animal sera. The target spot was excised from the 2D gel of liver cancer sera and the peptide mass fingerprinting as obtained LC-MS/MS analysis after digesting the chosen protein spot. This was identified to be complement C3 protein. The changes in complement C3 expression level were validated by Western blot analysis. We reported that the changes in complement C3 concentration start at very early stage of tumorogenesis. The fully grown tumors were developed at 120 days and hepatotumorogenesis was confirmed by histopathological examination. This protein may therefore represent a powerful tool in search for candidate biomarkers for HCC.

Inhibitory effect of nimesulide on the development of N-ethyl-N-nitro-N-nitrosoguanidine-induced gastric precancerous lesions in rats

AIM: To investigate the inhibitory effect of nimesulide, a selective cyclooxygenase (COX)-2 inhibitor, on the development of N-ethyl-N-nitro-N-nitrosoguanidine (ENNG)-induced gastric precanerous lesions in rats.

METHODS: Six-week-old male Wistar rats were given 100 mg/L of ENNG in their drinking water for 14 wk and then fed a diet containing nimesulide at doses of 300 mg/L and 1200 mg/L for 12 or 24 wk. The rats were sacrificed 14, 26 and 38 wk after nimesulide feeding to detect the changes in the gastric mucosa. The expression of COX-2, Bcl-2 and PCNA in the gastric mucosa was detected by immunohitochemistry, and cell apoptosis was determined using TUNEL assay.

RESULTS: Nimesulide significantly reduced the incidence of gastric precancerous lesions compared to controls (P < 0.05). The positive rates of COX-2 and Bcl-2 protein expression and proliferation index in the nimesulde group were significantly lower than those in the control group (17.6% vs 60%, 35.3% vs 84%, 18.9 ± 4.57 vs 49.43 ± 7.92, all P < 0.05), while the apoptotic index was significantly higher in the nimesulde group than in the control group (13.6 ± 1.82 vs 2.12 ± 0.53, P < 0.05). The expression of COX-2 and Bcl-2 protein was associated with proliferation index and apoptotic index (P < 0.01).

CONCLUSION: Nimesulide has inhibitory effects on the development of ENNG-induced gastric precancerous lesions in rats possibly via mechanisms associated with reducing COX-2 and Bcl-2 expression, inhibiting proliferation and inducing apoptosis of gastric epithelial cells.

Dual action of a selective cyclooxygenase-2 inhibitor on vascular endothelial growth factor expression in human hepatocellular carcinoma cells: novel involvement of discoidin domain receptor 2

PURPOSE

Vascular endothelial growth factor (VEGF) greatly contributes to the progression of hepatocellular carcinoma (HCC). It is reported that a selective cyclooxygenase-2 (COX-2) inhibitor inhibits cellular proliferation and may attenuate VEGF expression in HCC. We propose that different cascades in the VEGF pathway respond to COX-2 inhibition, depending on the cell types.

METHODS

The six human HCC cell lines--Hep3B, SNU387, SNU182, SNU423, SNU449, and PLC/PRF5--were cultured under normoxic and hypoxic conditions. Cells were treated with a selective COX-2 inhibitor (NS-398) and discoidin domain receptor 2 (DDR2) siRNA, and microarray analysis was performed.

RESULTS

NS-398 inhibited HCC proliferation and decreased the expression level of VEGF in HCC cells only under normoxia conditions. In hypoxia conditions, VEGF expression level in Hep3B cell was suppressed, while that in SNU387 cell was increased by NS-398 (P < 0.001). The NS-398-induced increase in VEGF expression in SNU387 cell was associated with the up-regulation of the DDR2 gene. NS-398-treated SNU series cells and PLC/PRF5 cells displayed a robust increase in DDR2 mRNA expression. Also, transfection with DDR2 siRNA decreased the VEGF expression level of SNU387, 423, 449 cells under hypoxia conditions (P < 0.05). In vivo chromatin immunoprecipitation assay demonstrated that NS-398 induces the enhancement of HIF-1α binding on VEGF promoter, leading to the increase in VEGF gene expression in hypoxic conditions. There is strong evidence that it is related to the DDR2 gene expression in SNU387 cells.

CONCLUSION

These findings disclose a novel cell-dependent regulatory mechanism of VEGF involving DDR2 gene in HCC cells.

Efficient colonization and therapy of human hepatocellular carcinoma (HCC) using the oncolytic vaccinia virus strain GLV-1h68

Virotherapy using oncolytic vaccinia virus strains is one of the most promising new strategies for cancer therapy. In this study, we analyzed for the first time the therapeutic efficacy of the oncolytic vaccinia virus GLV-1h68 in two human hepatocellular carcinoma cell lines HuH7 and PLC/PRF/5 (PLC) in cell culture and in tumor xenograft models. By viral proliferation assays and cell survival tests, we demonstrated that GLV-1h68 efficiently colonized, replicated in, and did lyse these cancer cells in culture. Experiments with HuH7 and PLC xenografts have revealed that a single intravenous injection (i.v.) of mice with GLV-1h68 resulted in a significant reduction of primary tumor sizes compared to uninjected controls. In addition, replication of GLV-1h68 in tumor cells led to strong inflammatory and oncolytic effects resulting in intense infiltration of MHC class II-positive cells like neutrophils, macrophages, B cells and dendritic cells and in up-regulation of 13 pro-inflammatory cytokines. Furthermore, GLV-1h68 infection of PLC tumors inhibited the formation of hemorrhagic structures which occur naturally in PLC tumors. Interestingly, we found a strongly reduced vascular density in infected PLC tumors only, but not in the non-hemorrhagic HuH7 tumor model. These data demonstrate that the GLV-1h68 vaccinia virus may have an enormous potential for treatment of human hepatocellular carcinoma in man.

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.

Targeting the inflammation in HCV-associated hepatocellular carcinoma: a role in the prevention and treatment

Epidemiological, preclinical and clinical studies demonstrated that chronic inflammation induced by hepatitis C virus (HCV) is crucial in hepatocellular carcinogenesis. The interaction between hepatocytes and microenvironment regards virus, inflammatory and immunocompetent cells, chemo- and cyto-kines, reactive oxygen species (ROS) and nitric oxide (NO), generating cell transformation. We suggest hepatocarcinoma (HCC) as a model in which the targeting of microenvironment determine neoplastic transformation. The present review focuses on: the role of inflammation in carcinogenesis, the clinical impact of HCC and the inadequacy of the actual therapy, the chemoprevention targeting the microenvironment.

Toll-like receptors as therapeutic targets in gastrointestinal diseases

IMPORTANCE OF THE FIELD

Toll-like receptors (TLRs) are innate immunity receptors that recognize several different antigens, initiating immunological/inflammatory responses. Recent evidence associates numerous pathophysiological processes and diseases with dysregulated activation of these receptors, conferring a potential therapeutic value to their modulation.

AREAS COVERED IN THIS REVIEW

The aim of this systematic review that covers literature from the past 10 years is to address the role of TLRs in the pathophysiology of gastrointestinal (GI) diseases as well as the therapeutic potential of modulating TLRs' signaling pathways in GI pathology.

WHAT THE READER WILL GAIN

This review shows that TLRs play an important role in the pathophysiology of several GI diseases and that modulating TLRs signaling pathways may have an enormous therapeutic potential. Different methods for modulation of TLRs' activity in GI tract, with direct agonists/antagonists but also with non-specific substances, like antibiotics or probiotics, are presented.

TAKE HOME MESSAGE

Even though TLRs modulators have been used for therapy in some GI diseases, further research, particularly in humans, is needed in order to establish the precise role of the different TLRs in the diverse GI diseases and to motivate clinical trials that consider TLRs as therapeutic targets in GI pathology.

Prognostic markers and putative therapeutic targets for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth most frequent human cancer and a fatal disease. Therapies with pharmacological agents do not improve the prognosis of patients with unresectable HCC. This emphasizes the need to identify new targets for early diagnosis, chemoprevention, and treatment of the disease. Available evidence indicates that clinical outcome of HCC could reflect the genetic predisposition to cancer development and progression. Numerous loci controlling HCC progression have been identified in rodents. In this review, we describe results of recent studies on effector mechanisms of susceptibility/resistance genes, responsible for HCC progression, aimed at identifying new putative prognostic markers and therapeutic targets of this tumor. Highest c-myc amplification and overexpression, alterations of iNOS crosstalk with IKK/NF-kB and RAS/ERK signaling, ubiquitination of ERK and cell cycle inhibitors, and deregulation of FOXM1 and cell cycle key genes occur in rapidly progressing dysplastic nodules and HCC, induced in genetic susceptible rat strains, compared to the lesions of resistant rats. Notably, alterations of these mechanisms in human HCC subtypes with poorer or better prognosis, are similar to those present in genetically susceptible and resistant rats, respectively, and function as prognostic markers and therapeutic targets. Attempts to cure advanced HCC by molecular therapy directed against specific targets led to modest survival benefit. Thus, efforts are necessary to identify and test, in pre-clinical and clinical studies, new therapeutic targets for combined molecular treatments of HCC. They may take advantage from the comparative analysis of signal transduction in HCCs differently prone to progress, in rats and humans.

In-vivo effects and mechanisms of celecoxib-reduced growth of cyclooxygenase-2 (COX-2)-expressing versus COX-2-deleted human HCC xenografts in nude mice

We previously reported that celecoxib, a cyclooxygenase-2 (COX-2) inhibitor, suppresses growth of human hepatocellular carcinoma (HCC) cells through both COX-2 dependence and independence. Recently, we established COX-2-deleted human HCC cells, C2D-HuH7, and C2D-HuH7-bearing nude mice. Using this novel model, we examined the pharmacological effects and mechanisms of celecoxib on in-vivo growth of HCC xenografts in relation to COX-2 expression. After treatment with celecoxib, the mice bearing HuH7 or C2D-HuH7 xenografts were assessed for the pharmacological effects and mechanisms of celecoxib on HCC xenograft growth in relation to COX-2 expression. Celecoxib resulted in an effective and comparable growth reduction of both COX-2-expressing and COX-2-deleted HuH7 xenografts in association with decreased Ki-67 expression. These results demonstrated celecoxib's COX-2-independent in-vivo anti-HCC effects. Celecoxib increased peroxisome proliferator-activated receptor gamma predominantly in HuH7 xenografts, indicating its COX-2 dependency. Celecoxib reduced p-Rb and DP1/E2F1 complex predominantly via upregulated p21/CDK4 complex in HuH7 xenograft, but p27/CDK4 complex in C2D-HuH7 xenografts. The effects of celecoxib on phosphatase and tensin homolog deleted on chromosome ten/PI3K/Akt signaling were COX-2 independent, but its effects on extracellular-regulated kinase signaling seemed COX-2 dependent. In addition, the effects of celecoxib on AC-H3, AC-H4, and histone deacetylase 2 could be both COX-2 dependent and independent. In conclusion, celecoxib suppresses growth of HuH7 xenografts regardless of COX-2 expression, which may be mediated through different signaling.

From molecular biology to targeted therapies for hepatocellular carcinoma: the future is now

Hepatocellular carcinoma (HCC) is characterized as a highly chemoresistant cancer with no effective systemic therapy. Despite surgical or locoregional therapies, prognosis remains poor because of high tumor recurrence or tumor progression, and currently there are no well-established effective adjuvant therapies. The molecular biology of carcinogenesis and tumor progression of HCC has been increasingly understood with intense research in recent years. Several important intracellular signaling pathways such as the Ras/Raf/Mek/Erk pathway and PI3k/Akt/mTOR pathway have been recognized, and the role of several growth factors and angiogenic factors such as EGF and VEGF has been confirmed. Effective agents targeting these molecular abnormalities have been developed and widely tested in preclinical studies of HCC cell lines or xenograft models. Several agents have entered clinical trials in HCC patients, and recent data indicated that a multikinase inhibitor targeting Ras kinase and VEGFR-2, sorafenib, is effective in prolonging survival of patients with advanced HCC. The management of advanced HCC is entering the era of molecular targeting therapy, which is of particular significance for HCC in view of the lack of existing effective systemic therapy for this cancer.

Treatment of hepatocarcinoma

This article reviews the current developments and significant trends in the treatment of hepatocarcinoma (HCC). Prevention programs should be based on large vaccination campaigns and the use of immunologic or biologic molecules to delay the onset of HCC in already cirrhotic patients. Surgery remains the therapy of choice in patients with a small and limited number of tumor nodules. To date, no preoperative treatment has been proven useful. Adjuvant treatments involving systemic chemotherapy, intra-arterial infusion, or chemoembolization failed to improve survival, whereas immune therapy, retinoids, radiolabeled isotopes, and antiangiogenic agents seem promising. Such local treatments as percutaneous ethanol injection, cryotherapy, and radiofrequency are proposed for patients with limited hepatic function and should be combined with other treatment modalities to optimize their efficacy and limit their toxicity. Regional therapy should take a selective, subsegmental approach at intervals depending on tumor response and possibly combined with other treatment modalities. Systemic therapy with cytotoxic agents remains disappointing. Hormonal therapy with tamoxifen or antiandrogens has shown no efficacy and might even be detrimental. Further progress may be expected from targeted therapy.

Liver angiogenesis as a risk factor for hepatocellular carcinoma development in hepatitis C virus cirrhotic patients

AIM: To evaluate the predictive value of hepatocyte proliferation and hepatic angiogenesis for the occurrence of Hepatocellular carcinoma (HCC) in hepatitis C virus (HCV) cirrhotic patients.

METHODS: One hundred-five patients (69 males, 36 females; age range, 51-90 year; median 66 year) with biopsy proven HCV cirrhosis were prospectively monitored for HCC occurrence for a median time of 64 mo. Angiogenesis was assessed by using microvessel density (MVD), hepatocyte turnover by MIB1 and PCNA indexes at inclusion in liver biopsies.

RESULTS: Forty six patients (43.8%) developed HCC after a median time of 55 (6-120) mo while 59 (56.2%) did not. Patients were divided into two groups according to the median value of each index. The difference between patients with low (median MVD = 3; range 0-20) and high (median MVD = 7; range 1-24) MVD was statistically significant (χ² = 22.06; P < 0.0001) which was not the case for MIB1 or PCNA (MIB-1: χ² = 1.41; P = 0.2351; PCNA: χ² = 1.27; P = 0.2589). The median MVD was higher in patients who developed HCC than in those who did not. HCC-free interval was significantly longer in patients with the MVD ≤ 4 (P = 0.0006). No relationship was found between MIB₁ or PCNA and MVD (MIB-1 r² = 0.00007116, P = 0.9281; PCNA: r² = 0.001950; P = 0.6692). MVD only was able to predict the occurrence of HCC in these patients. Among other known risk factors for HCC, only male sex was statistically associated with an increased risk.

CONCLUSION: Liver angiogenesis has a role for in HCV-related liver carcinogenesis and for defining patients at higher risk.

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.

Cimetidine inhibits epidermal growth factor-induced cell signaling

BACKGROUND

Cimetidine, a histamine-2 (H2) receptor antagonist, has been demonstrated to have anticancer effects on colorectal cancer, melanoma and renal cell carcinoma. In the current study, we clarified that cimetidine inhibits both epidermal growth factor (EGF)-induced cell proliferation and migration in hepatocellular carcinoma (HCC) cell lines.

METHOD

HCC cell lines (Hep3B, HLF, SK-Hep-1, JHH-2, PLC/PRF/5 and HLE) were used and cell proliferation was assessed by [3H]-thymidine incorporation assay. Cell migration was measured by in vitro cell migration assay. Biological effects of cimetidine were assessed with human EGF receptor (EGFR)-expressing mouse fibroblast cells (NR6-WT). The autophosphorylation of EGFR and the activation of other downstream effectors were analyzed by immunoprecipitation and immunoblotting. The concentration of intracellular cyclic AMP (cAMP) was measured by competitive enzyme immunoassay.

RESULTS

Cimetidine inhibited both EGF-induced cell proliferation and migration in Hep3B, HLF, SK-Hep-1 and JHH-2, while cimetidine did not affect EGF-induced cell proliferation and migration in PLC/PRF/5 and HLE. Cimetidine was revealed to disrupt the EGF-induced autophosphorylation of EGFR and its downstream effectors, mitogen activated protein kinases and phospholipase C-gamma. To define the molecular basis of this negative regulation, we identified that cimetidine significantly decreased intracellular cAMP levels and that decrement of cAMP inhibited autophosphorylation of EGFR. The cell permeable cAMP analog, CPT-cAMPS reversed the cimetidine-induced inhibition of EGF-induced cell proliferation and cell migration by restoring autophosphorylation of EGFR.

CONCLUSION

Cimetidine inhibited EGF-induced cell proliferation and migration in HCC cell lines by decreasing the concentration of intracellular cAMP levels. Cimetidine may be a candidate chemopreventive agent for HCC.

Cyclooxygenase-2 expression in hepatocellular carcinoma, cirrhosis and chronic hepatitis in the United States

Aberrant expression of cyclooxygenase-2 in hepatocellular carcinoma was described in Asia. Using immunohistochemistry, we studied the expression of cyclooxygenase-2 in hepatocellular carcinoma, chronic hepatitis, and cirrhosis in a US institution. A staining score of 0-5 representing the sum of an intensity score and a distribution score was used. The mean scores were 2.2+/-1.60 for chronic hepatitis, 4.37+/-1.15 for cirrhosis, and 4.76+/-0.54 for hepatocellular carcinoma. We found a significant difference in mean staining scores between chronic hepatitis and cirrhosis (p < 0.0001), as well as between chronic hepatitis and hepatocellular carcinoma (p < 0.0001). Fibrosis correlated with cyclooxygenase-2 staining score (r=0.65).

IN CONCLUSION

(1) Cyclooxygenase-2 expression is higher in cirrhosis and hepatocellular carcinoma when compared to chronic hepatitis. (2) Cyclooxygenase-2 expression correlates with the stage of fibrosis. (3) These results imply that in chronic hepatitis and possibly in cirrhosis, hepatocarcinogenesis may be a cyclooxygenase-2 dependent mechanism.

H-Ras selectively up-regulates MMP-9 and COX-2 through activation of ERK1/2 and NF-kappaB: an implication for invasive phenotype in rat liver epithelial cells

One of the most frequent events in carcinogenesis is uncontrolled activation of Ras signaling pathway. A previous study demonstrated that the introduction of H-Ras into the normal WB-F344 rat liver epithelial (WB) cell line and adult male F344 rats resulted in tumorigenicity. The present study investigated whether H-Ras induced the invasive and migrative phenotypes in WB cells, and subsequently aimed at characterizing the underlying mechanisms. H-Ras induced the invasive and migrative phenotypes of WB cells with a selective up-regulation of matrix metalloproteinase (MMP)-9, but not MMP-2. Cyclooxygenase (COX)-2 and the subsequent production of prostaglandin E2 (PGE2) were also induced by H-Ras. Treatment of H-Ras WB cells with GM6001 and NS398, the inhibitors of MMPs and COX-2, respectively, significantly inhibited the H-Ras-induced invasive and migrative phenotypes. DNA binding activity of nuclear factor (NF)-kappaB, but not that of activator protein (AP)-1, was increased by H-Ras. Caffeic acid phenethyl ester and Bay 11-7082, specific inhibitors of NF-kappaB and IKK, respectively, significantly inhibited the expression of MMP-9 and COX-2, invasion and migration of H-Ras WB cells, revealing NF-kappaB as a transcriptional factor responsible for H-Ras-induced malignant phenotypic conversion of WB cells. Activation of ERKs pathway was critical for H-Ras-induced invasive and migrative phenotypes, up-regulation of MMP-9 and COX-2 as well as enhanced DNA binding activity of NF-kappaB in WB cells. Taken together, these results demonstrate that H-Ras up-regulates MMP-9 and COX-2 through activation of ERKs and IKK-IkappaBalpha-NF-kappaB signal pathway which may contribute to the malignant progression of WB rat liver epithelial cells.

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.

Evaluation of possible mechanisms of protective role of Tamarix gallica against DEN initiated and 2-AAF promoted hepatocarcinogenesis in male Wistar rats

We have previously reported that Tamarix gallica caused a marked inhibition of thioacetamide-induced hepatotoxicity, oxidative damage and early tumor promotion related events in the liver. These results strongly indicates that T. gallica may have chemopreventive potential. Therefore, in the present study, we examined the inhibitory effects of T. gallica methanolic extract on diethylnitrosamine (DEN) initiated and 2-acetyl aminofluorene (2-AAF) promoted liver carcinogenesis in male Wistar rats. Interestingly, it was found that T. gallica (25 and 50 mg/kg body wt.) resulted in a marked reduction of the incidence of liver tumors. The study was further histologically confirmed. Furthermore to understand the underlying mechanisms of chemopreventive action by T. gallica we evaluated the levels activities of hepatic antioxidant defense enzymes, ornithine decarboxylase activity and hepatic DNA synthesis as a marker for tumor promotion since direct correlation between these marker parameters and carcinogenicity have been well documented. Treatment of male Wistar rats for five consecutive days with 2-AAF i.p. induced significant hepatic toxicity, oxidative stress and hyperproliferation. Pretreatment of T. gallica extract (25 and 50 mg/kg body wt.) prevented oxidative stress by restoring the levels of antioxidant enzymes and also prevented toxicity at both the doses. The promotion parameters induced (ornithine decarboxylase activity and DNA synthesis) by 2-AAF administration in diet with partial hepatectomy (PH) were also significantly suppressed dose-dependently by T. gallica. Therefore, we can conclude that ultimately the protection against liver carcinogenesis by T. gallica methanolic extract might be mediated by multiple actions, which include restoration of cellular antioxidant enzymes, detoxifying enzymes, ODC activity and DNA synthesis.

New therapies for hepatocellular carcinoma

Hepatocellular carcinoma (HCC), one of the most common cancers worldwide, is often diagnosed at an advanced stage when most potentially curative therapies such as resection, transplantation or percutaneous and transarterial interventions are of limited efficacy. The fact that HCC is resistant to conventional chemotherapy, and is rarely amenable to radiotherapy, leaves this disease with no effective therapeutic options and a very poor prognosis. Therefore, the development of more effective therapeutic tools and strategies is much needed. HCCs are phenotypically and genetically heterogeneous tumors that commonly emerge on a background of chronic liver disease. However, in spite of this heterogeneity recent insights into the biology of HCC suggest that certain signaling pathways and molecular alterations are likely to play essential roles in HCC development by promoting cell growth and survival. The identification of such mechanisms may open new avenues for the prevention and treatment of HCC through the development of targeted therapies. In this review we will describe the new potential therapeutic targets and clinical developments that have emerged from progress in the knowledge of HCC biology, In addition, recent advances in gene therapy and combined cell and gene therapy, together with new radiotherapy techniques and immunotherapy in patients with HCC will be discussed.

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 (COX-2) is directly involved but not decisive in proliferation of human hepatocellular carcinoma cells

Expression of cyclooxygenase-2 (COX-2) is involved in the chronic inflammation-related development of hepatocellular carcinoma (HCC), and the use of selective COX-2 inhibitors might provide new chemoprevention strategies for HCC. However, the role of the COX-2 in hepatocarcinogenesis remains obscure, particularly as it has been primarily studied with selective COX-2 inhibitors that may affect other cellular proteins involved in cell proliferation. Therefore, we investigated the effects of the inhibition of COX-2 by the selective COX-2 inhibitor NS-398 as well as by COX-2 specific small interfering RNA (siRNA) in the human HCC cell lines Hep3B and SNU-387. These cell lines expressed COX-2, and NS-398 induced apoptosis of these cells. NS-398 inhibited more than 60% of prostaglandin E(2) (PGE2) production and cell proliferation in a concentration-dependent manner in these cells. The inhibition of proliferation was almost restored with PGE2 supplement, suggesting that NS-398 may inhibit cell growth partially through inhibition of COX-2 and PGE2 production in human HCC cells. However, treatment with NS-398 led to increased expression of COX-2 in Hep3B and SNU-387 cells. To examine the effect of COX-2 depletion on these cells, we electroporated COX-2-specific siRNAs into SNU-387 cells. We observed significant, sequence-specific reductions in COX-2 expression, PGE2 production, and cell proliferation, though the reduction in cell proliferation was less than that induced by NS-398. In conclusion, these data suggest that COX-2 itself is directly involved, though not decisively, in proliferation of human HCC cells. RNA interference may provide a useful tool for manipulating COX-2-related hepatocarcinogenesis in research and therapeutic settings.

In vitro and in vivo effects and mechanisms of celecoxib-induced growth inhibition of human hepatocellular carcinoma cells

PURPOSE

Cyclooxygenase-2 (COX-2) inhibitors cause growth inhibition of human hepatocellular carcinoma cells but it remains unclear whether this is both COX-2 dependent and independent. The related mechanisms remain to be determined. The present study was aimed to determine the effect of celecoxib on growth of hepatocellular carcinoma cells and xenografts and the related mechanisms.

EXPERIMENTAL DESIGN

Both low COX-2 expressing PLC/PRF/5 and high COX-2 expressing HuH7 cells, and nude mice bearing hepatocellular carcinoma xenografts were used to study the effect and mechanisms of celecoxib on hepatocellular carcinoma cell growth.

RESULTS

Celecoxib resulted in a comparable growth inhibition of both hepatocellular carcinoma cells that was associated with decreased production of prostaglandin E(2) and increased peroxisome proliferator-activated receptor gamma in both cells. Addition of prostaglandin E(2) only partially counteracted the effect of celecoxib on both cells. Celecoxib resulted in a significant reduction of retinoblastoma phosphorylation and DP1/E2F1 complex in both cells. Celecoxib caused a significant increase of apoptosis and activation of caspase-3 and caspase-9 in both cells. In nude mice inoculated with HuH7 cells, celecoxib resulted in decreased frequency and mean weight of hepatocellular carcinoma xenografts.

CONCLUSION

The present study showed that celecoxib causes COX-2-dependent and COX-2-independent growth inhibition of hepatocellular carcinoma cells and xenografts by (a) decreased retinoblastoma phosphorylation and DP1/E2F1 complex; (b) increased activation of caspase-3 and caspase-9; and (c) increased expression of proliferator-activated receptor gamma. The present study significantly extended our knowledge on the effect and mechanisms of celecoxib-induced inhibition of hepatocellular carcinoma cell growth.

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.

Prostaglandin E2 promotes migration and adhesion in hepatocellular carcinoma cells

The effect of the expression of cyclooxygenase-2 (COX-2) and prostaglandin E2 (PGE2) synthesis on cell migration, the secretion of matrix metalloproteinases (MMPs) and the adhesion of human hepatoma cell lines has been investigated. A close correlation was observed between the expression of COX-2 under basal conditions and the secretion of MMP-2 and MMP-9. Cell migration in HuH-7 cells, which express high constitutive levels of COX-2 was significantly inhibited by selective inhibitors of COX-2 and enhanced by exogenous addition of PGE2. Hepatocellular carcinoma (HCC) cells expressed beta1 and alphaV beta3 integrins, exhibiting an increase in cell adhesion onto fibronectin and vitronectin. Moreover, addition of PGE2 increased the beta1 integrin levels and adhesion on vitronectin in HuH-7 cells. Inhibitors of MEK/ERK, p38 MAPK, protein kinases A and C impaired the migration of HuH-7 cells induced by PGE2, indicating the involvement of multiple pathways in the process. Taken together, these results support the existence of a relationship between COX-2-derived PGE2 synthesis, and migration and adhesion through an integrin-dependent pathway in HCC cells.

Advances in Chemoprevention of Head and Neck Cancer

Head and neck squamous cell carcinoma is a devastating disease with a poor outcome in advanced stages, accounting for approximately 3% of all malignancies, with an estimated 37200 new cases and 11000 deaths annually in the U.S. Second primary tumors are estimated to occur at an annual rate of 3%-10% and are significant threats to long-term survivors. Chemoprevention is an appealing strategy, and its success has been demonstrated in breast cancer and familial adenomatous polyposis. High-dose retinoids have been shown to be active against oral premalignant lesions and in prevention of second primary tumors in the head and neck. New targets include the epidermal growth factor receptor, cyclooxygenase-2, and other molecular targets. Challenges in future head and neck cancer chemoprevention investigations include achieving long-lasting efficacy with retinoids and/or new agents, and determining the optimal dose and duration of therapy while maintaining acceptable toxicities.

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[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.

Hepatocellular carcinoma: updates in primary prevention

Hepatocellular carcinoma is a significant cause of mortality worldwide and a growing problem in the United States. Treatment options are often limited, and median survival is less than 1 year. Thus, prevention may provide the best opportunity to alter the natural history of this disease. Primary prevention is best exemplified by the successes of such public health measures as universal hepatitis B vaccination. Such antiviral therapies as interferon may also have a role. Lessons can be learned from complementary and alternative medicine. Nevertheless, more work is needed in understanding hepatocarcinogenesis and in developing models to assess potential chemopreventive agents.

Cyclooxygenase 2 (COX2)-prostanoid pathway and liver diseases

Cycloocygenases 2 (COX2)-prostanoid pathway plays important and complex roles in the pathogenesis of various liver diseases. Most studies indicated that COX2-prostanoid pathway might suppress hepatic fibrogenesis by decreasing proliferation, migration, and contractility of hepatic stellate cells (HSCs). In animal model, COX2-prostanoid pathway increases portal hypertension, which can be reduced by treatment with COX2 inhibitor. In cirrhosis, COX2-prostanoid pathway may reduce formation of ascites by enhancing free water excretion, and protect gastric mucosa from ulcerative insults. Aberrant expression of COX2 has been well associated with hepatocarcinogenesis. COX2 inhibitors can effectively suppress proliferation of hepatocellular carcinoma (HCC) cells. This provided rationale for further testing COX2 inhibitors as clinical agents for HCC chemoprovention. Further studies will be needed to examine how COX2 inhibitors affect pathogenesis of various liver diseases.

Inhibitory Effects of Lutein and Lycopene on Placental Glutathione S-Transferase-Positive Preneoplastic Lesions and DNA Strand Breakage Induced in Wistar Rats by the Resistant Hepatocyte Model of Hepatocarcinogenesis

Inhibitory effects of lutein (LUT) and lycopene (LYC) on hepatic preneoplastic lesions (PNLs) and DNA strand breakage induced in Wistar rats by the resistant hepatocyte (RH) model of hepatocarcinogenesis were investigated. Animals received by gavage during 8 consecutive weeks on alternate days 70 mg/kg body weight of LUT or LYC. Rats treated with only corn oil and submitted to this model were used as controls. At the end of the experiment, treatment of the animals with LUT or LYC resulted in an increase in the respective liver carotenoid concentrations (P < 0.05). Moreover, it tended to reduce the incidence, total number, and multiplicity of hepatocyte nodules compared with the control group, although the differences did not reach statistical significance. Animals treated with LUT or LYC presented also a lower number of hepatic placental glutathione S-transferase-positive (GST-P) PNLs (P < 0.05), which were smaller (P < 0.05) and occupied a smaller area of the liver section (P < 0.05). Finally, hepatic DNA strand breakage evaluated by the comet assay was lower (P < 0.05) in carotenoid-treated animals when compared with the control group. Therefore, the results indicate that LUT and LYC represent promising chemopreventive agents during hepatocarcinogenesis and whose anticarcinogenic actions could be related to a protection against DNA instability.

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.

Susceptibility and biomarker knowledge for improvement of environmental health

At the international level, environmental health problems are usually most serious in countries that have the least resources to deal with the problems. Therefore, international efforts have been initiated to achieve equitable environmental health globally. One approach is to conduct international collaborative studies. This approach has been successful in the building of scientific infrastructure in these countries so that they can address their own environmental health concerns and to sustain the environmental health programs. Using liver and oral cancers as models for discussion, examples of success in the identification of etiology and the mechanisms for the diseases are provided. For example, biomarkers are used to provide early warning signals for the disease. In addition, the application of the collected information for developing disease prevention and intervention programs is presented. Expertise in genetic susceptibility is used to provide a more precise understanding of the cancer process. With the precise knowledge, the information can potentially be used to screen for high-risk individuals and to develop "designer" intervention procedures against specific biochemical defects. Success in disease prevention is dependent upon multidisciplinary collaborations at the local and international levels.