Potent cell growth inhibitory effects in hepatitis B virus X protein positive hepatocellular carcinoma cells by the selective cyclooxygenase-2 inhibitor celecoxib

Knockdown of cyclooxygenase-2 leads to growth inhibition and cell cycle arrest in hepatocellular carcinoma cells

Background & aims: Cyclooxygenase-2 (COX-2) is proved to play important roles in the development and progression of various human tumors, including hepatocellular carcinoma (HCC). However, the antitumor effect of RNA interference (RNAi) technology targeting COX-2 in HCC has not yet been verified.

Methods: We silenced COX-2 expression using a lentivirus-mediated RNAi and further investigated the effects of COX-2 knockdown on cell growth and cell cycle in Huh7 and SMMC-7721 cells. COX-2 mRNA was detected by RT-PCR while COX-2 protein was detected by Western blotting. The cell proliferation was measured by MTT assay. The cell cycle was measured by flow cytometry. The tumorigenicity of HCC cells was evaluated using soft-agar clonogenic assay in vitro and nude mouse xenograft model in vivo.

Results: The down-regulation of COX-2 expression significantly inhibited cell proliferation and colony formation, and led to cell cycle arrest in vitro, and reduced the potential of tumorigenicity in vivo in both Huh7 and SMMC-7721 cells. Furthermore, PGE2 production was also decreased after COX-2 expression was suppressed. Finally, knockdown of COX-2 also induced the down-regulation of cell cycle-related protein, cyclinD1.

Conclusions: The abrogation of COX-2 expression can lead to potent antitumor activity and knockdown of COX-2 may be served as a prospective therapeutic strategy against HCC.

Prostaglandin E2 As a Modulator of Viral Infections

Viral infections are a major cause of infectious diseases worldwide. Inflammation and the immune system are the major host defenses against these viral infection. Prostaglandin E2 (PGE2), an eicosanoid generated by cyclooxygenases, has been shown to modulate inflammation and the immune system by regulating the expression/concentration of cytokines. The effect of PGE2 on viral infection and replication is cell type- and virus-family-dependent. The host immune system can be modulated by PGE2, with regards to immunosuppression, inhibition of nitrogen oxide (NO) production, inhibition of interferon (IFN) and apoptotic pathways, and inhibition of viral receptor expression. Furthermore, PGE2 can play a role in viral infection directly by increasing the production and release of virions, inhibiting viral binding and replication, and/or stimulating viral gene expression. PGE2 may also have a regulatory role in the induction of autoimmunity and in signaling via Toll-like receptors. In this review the known effects of PGE2 on the pathogenesis of various infections caused by herpes simplex virus, rotavirus, influenza A virus and human immunodeficiency virus as well the therapeutic potential of PGE2 are discussed.

Downregulation of mPGES-1 Expression via EGR1 Plays an Important Role in Inhibition of Caffeine on PGE2 Synthesis of HBx(+) Hepatocytes

We investigated the mechanism of caffeine in influencing HBx(+) hepatocytes to synthesize PGE₂. The inhibitory effect of caffeine on hepatocyte proliferation increased with increasing caffeine concentrations (200–800 μM) and treatment times (1–7 days), which was first observed at the second test time point (caffeine treatment for 4 days). The inhibition of caffeine on the growth of HL7702-HBx and HepG2-HBx cells was most obvious at 800 μM caffeine and at caffeine treatment for 7 days. The PGE₂ secretion and the expression of mPGES-1 and EGR1 were downregulated, whereas PPARγ expression was upregulated. The mPGES-1 promoter activity of HBx(+) hepatocytes decreased more significantly than that of HBx(−) hepatocytes. Moreover, the expression of EGR1 and PPARγ changed more significantly in HBx(+) hepatocytes cultured for 12 to 24 hours in the presence of 5 mM caffeine. This limited success may be attributed to caffeine releasing the binding of HBx and PPARγ and furthermore affecting the mPGES-1 expression by EGR1 in HBx(+) hepatocytes. The results indicate that caffeine could effectively reduce PGE₂ synthesis in HBx(+) hepatocytes by specifically blocking the PPARγ-EGR1-mPGES-1 pathway, thereby providing a new evidence of molecular biology for the hypothesis that drinking coffee is beneficial to HBV-infected patients.

The association between three cyclooxygenase-2 polymorphisms and hepatocellular carcinoma risk: a meta-analysis

BACKGROUND

A quantity of case-control studies have been performed to address the association between three cyclooxygenase-2(COX-2) polymorphisms (-1195G/A, -765G/C and +8473T/C) and the risk of hepatocellular carcinoma (HCC). However, previous research results are inconsistent. We conducted this meta-analysis to clarify the correlation between these COX-2 polymorphisms and HCC risk.

METHODS

The authors searched in PubMed, EMBASE, Google Scholar, CNKI and WanFang database for relevant articles up to April 28, 2014. The data were extracted by two independent reviewers. Odds ratios (ORs) and 95% confidence intervals were calculated.

RESULTS

A total of 8 studies consisting of 2182 cases and 3324 controls were included in this meta-analysis. For COX-2 polymorphism -1195G/A, an association with increased risk was observed under the heterogeneous, homozygous, dominant model. However, COX-2 polymorphisms (-765G/C and +8473T/C) were not related to HCC risk in this study. We also found a similar result in the subgroup analysis of Chinese population that -1195G/A polymorphism, instead of -765G/C or +8473T/C polymorphism, was correlated with the risk of HCC.

CONCLUSIONS

Polymorphism -1195G/A of COX-2 might be associated with susceptibility to HCC, but no similar correlations were observed between polymorphisms (-765G/C and +8473T/C) and HCC risk. Further large and well-designed studies are required to validate this association.

15-Deoxy-Δ(12,14)-prostaglandin J2 (15d-PGJ2) promotes apoptosis of HBx-positive liver cells

This study aims to investigate the inflammatory response characteristics of liver cells caused by HBV x protein (HBx) and the unique function of the PGE2 inhibitor on HBx-positive liver cells. Tetrazolium blue colorimetric method, flow cytometry, and Western blot were performed to detect the proliferation, cycle, and apoptosis protein expression of HBx-positive HL7702 liver and control cells. The effect of the PGE2 inhibitor 15-Deoxy-Δ(12,14)-prostaglandin J2 (15d-PGJ2) on the growth of HL7702-HBx was also observed. HBx induces the PGE2 accumulation in HL7702 liver cells and promotes their growth and inhibits their apoptosis. HL7702-HBx and HL7702 cells showed increased apoptosis rate, increased apoptosis-promoting protein expression, and reduced apoptosis-inhibiting protein expression under the effect of 15d-PGJ2, and the changes in HL7702-HBx cells were more significant than in HL7702 cells. HBx expression causes liver cells to be more sensitive to the apoptosis-promoting function of 15d-PGJ2. Therefore, the use of 15d-PGJ2 may be a new method for the prevention or treatment of inflammatory changes to cancer caused by HBV infection in liver cells.

Cholestatic hepatitis with small duct injury associated with celecoxib

Drug-induced liver injury (DILI) is a common clinical entity but is underreported due to various reasons. Cyclooxygenase-2 inhibitors like Celecoxib have been proven to be associated with lesser incidence of adverse drug reactions compared to other nonsteroidal anti-inflammatory drugs (NSAID). However, Celecoxib has been rarely reported to be associated with cholestasis and hepatitis. We present a young Hispanic female presented with cholestatic liver chemistries who has been taking Celecoxib for 3 weeks. Extensive workup did not support diagnosis of viral, autoimmune, or metabolic liver diseases. Liver biopsy revealed findings suggestive of secondary sclerosing cholangitis. Imaging studies were negative for large duct involvement, and endoscopy ruled out inflammatory bowel disease. Liver chemistries normalized after cessation of medication. We recommend that physician should be aware of this rare complication when prescribing Celecoxib.

Green tea polyphenol epigallocatechin-3-gallate enhances 5-fluorouracil-induced cell growth inhibition of hepatocellular carcinoma cells

AIM

  5-Fluorouracil (5-FU) is one of the most commonly used chemotherapeutic drugs. Resistance to 5-FU is a major cause of chemotherapy failure in advanced-stage hepatocellular carcinoma (HCC). Green tea polyphenol Epigallocatechin-3-gallate (EGCG) plays a critical role in growth inhibition and apoptotic induction in HCC cell lines. The aim of this study is to investigate whether EGCG can enhance 5-FU-induced cell growth inhibition and to explore its potential mechanisms.

METHODS

  3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was used to evaluate cell growth. Western blotting analysis was performed to detect the proteins expression in Hep3B cells. Small interfering RNA was used to suppress cyclooxygenase-2 (COX-2) expression. Furthermore, enzyme linked immunosorbent assay was used to test the prostaglandin E(2) (PGE(2) ) production in cell cultures.

RESULTS

  Epigallocatechin-3-gallate augmented the anti-tumor effect of 5-FU in Hep3B cells. Significant difference was observed between the treated groups and the control group (P < 0.05). EGCG (its concentrations at over 5 µmol/L) combined with 5-FU presented a synergic effect. Furthermore, the combination of EGCG and 5-FU abrogated the COX-2 overexpression and PGE(2) secretion induced by 5-FU. The upregulation of COX-2 expression decreased the phosphorylation of Akt (Thr(308) ) expression. These appeared to be followed by the AMPK hyperactivation.

CONCLUSION

  Epigallocatechin-3-gallate sensitizes HCC cells to 5-FU antitumor activity, and the combination of EGCG and 5-FU exhibits synergism in chemo-resistant cancer cells. The results suggest potential novel therapies for the treatment of advanced-stage liver cancer.

Celecoxib inhibits the expression of MMP-2 and ICAM-1 in hepatocellular carcinoma xenografts in nude mice

AIM: To investigate the antitumor effects of celecoxib (a selective cyclooxygenase-2 inhibitor) against hepatocellular carcinoma in vivo.

METHODS: Human hepatoma cells (HepG2, BEL-7402 and SMMC-7721) were injected beneath the hepatic capsule of six-week-old nude mice. The mice were then randomly divided into three groups: negative control group (intragastrically given normal saline), experimental group (intragastrically given celecoxib), and positive control group (intragastrically given normal saline and intraperitoneally injected with adriamycin). Three weeks later, tumor tissue samples were taken for immunohistochemical analysis to examine the expression of matrix metalloproteinase-2 (MMP-2), tissue inhibitor of metalloproteinases-2 (TIMP-2) and intercellular adhesion molecule-1 (ICAM-1).

RESULTS: Compared to the negative control group, the expression of MMP-2 was down-regulated (P < 0.05) and that of TIMP-2 was up-regulated (P < 0.05) in hepatocellular carcinoma xenografts derived from HepG2, BEL-7402 and SMMC-7721 cells in the experimental group. The expression of ICAM-1 was also down-regulated in hepatocellular carcinoma xenografts derived from BEL-7402 and SMMC-7721 cells in the experimental group when compared with the negative control group (P < 0.05).

CONCLUSION: Celecoxib may be able to inhibit the metastasis and improve the prognosis of hepatocellular carcinoma.

Treatment with cyclooxygenase-2 inhibitors enables repeated administration of vaccinia virus for control of ovarian cancer

Metastatic ovarian cancer is the leading cause of death among women with gynecologic malignancies in the United States. The lack of effective treatment for patients with advanced ovarian cancer warrants development of innovative therapies. Cancer therapy using oncolytic viruses represents a promising new approach for controlling tumors. Vaccinia virus has been shown to preferentially infect tumor cells but not normal tissue. However, oncolytic therapy using recombinant viruses faces the limitation of viral clearance due to generation of neutralizing antibodies. In the current study, we found that cyclooxygenase-2 (Cox-2) inhibitors circumvented this limitation, enabling repeated administration of vaccinia virus without losing infectivity. We quantified the antivaccinia antibody response using enzyme-linked immunosorbent assay (ELISA) and neutralization assays to show that treatment of Cox-2 inhibitors inhibited the generation of neutralizing antibodies. Furthermore, we showed that combination treatment of Cox-2 inhibitors with vaccinia virus was more effective that either treatment alone in treating MOSEC/luc tumor-bearing mice. Thus, the combination of Cox-2 inhibitors and vaccinia virus represents a potential innovative approach to controlling ovarian tumors.