Helicobacter pylori enhances cyclooxygenase 2 expression via p38MAPK/ATF-2 signaling pathway in MKN45 cells

Increased ATF2 expression predicts poor prognosis and inhibits sorafenib-induced ferroptosis in gastric cancer

Sorafenib, a tyrosine kinase inhibitor, has an important antitumor effect as a ferroptosis inducer in multiple cancers, including gastric cancer (GC). However, the status of sorafenib as a ferroptosis inducer has recently been questioned. There is very limited information about the relationship between ferroptosis and ATF2, and the role of ATF2 in sorafenib-induced ferroptosis has not been studied. In this study, we investigated the role and underlying molecular mechanisms of ATF2 in sorafenib-induced ferroptosis in GC. We found that ATF2 was significantly upregulated in GC tissues and predicted a poor clinical prognosis. Silencing ATF2 significantly inhibited the malignant phenotype of GC cells. In addition, we observed that ATF2 was activated during sorafenib-induced ferroptosis in GC cells. ATF2 knockdown promoted sorafenib-induced ferroptosis, while ATF2 overexpression showed the opposite results in GC cells. Using ChIP-Seq and RNA-Seq, we identified HSPH1 as a target of ATF2 and further validated it by ChIP‒qPCR analysis. HSPH1 can interact with SLC7A11 (cystine/glutamate transporter) and increase its protein stability. Importantly, knockdown of HSPH1 partly reversed the effects caused by ATF2 overexpression on sorafenib-induced ferroptosis in GC cells. In addition, the results from the tumor xenograft model showed that ATF2 knockdown can effectively enhance sorafenib sensitivity in vivo. Collectively, our study reveals a novel mechanism by which sorafenib induces ferroptosis in GC.

Association Between Aspirin Use and Gastric Adenocarcinoma: A Prospective Cohort Study

Prospective data examining the association of aspirin use, according to dose and duration, with long-term risk of gastric adenocarcinoma in non-Asian cohorts are lacking. We evaluated the association between aspirin use and risk of gastric adenocarcinoma in two large prospective U.S. cohort studies, the Nurses' Health Study and the Health Professionals Follow-up Study. Cox proportional hazards regression models were used to calculate multivariable adjusted HRs and 95% confidence intervals (CI). Among the 159,116 participants, we documented 316 gastric adenocarcinoma cases (176 women, 140 men) over 34 years encompassing 4.5 million person-years. Among women, regular aspirin use (at least two times or more per week) was significantly associated with lower risk of gastric adenocarcinoma (multivariable HR, 0.52; 95% CI, 0.37-0.73) compared with nonregular use. However, regular aspirin use was not associated with gastric adenocarcinoma risk among men (multivariable HR, 1.08; 95% CI, 0.77-1.52; Pheterogeneity for sex = 0.003). Among women, the lower risk of gastric adenocarcinoma was more apparent with increasing duration of aspirin use (Ptrend < 0.001) and more than five tablets per week (multivariable HR, 0.51; 95% CI, 0.31-0.84). Regular, long-term aspirin use was associated with lower risk of gastric adenocarcinoma among women, but not men. The benefit appeared after at least 10 years of use and was maximized at higher doses among women. The heterogeneity by sex in the association of aspirin use with risk of gastric adenocarcinoma requires further investigation.

PREVENTION RELEVANCE

Novel prevention is urgently needed to reduce incidence and mortality of gastric cancer. We found that regular aspirin use was associated with lower risk of gastric adenocarcinoma among women, but not men. The benefit appeared after at least 10 years of use and was maximized at higher doses among women. See related Spotlight, p. 213.

Emerging therapeutic targets for gastric cancer from a host-Helicobacter pylori interaction perspective

INTRODUCTION

Gastric cancer (GC) has the higher genetic, cytologic, and architectural heterogeneity compared to other gastrointestinal cancers. By inducing gastric inflammation, Helicobacter pylori (HP) may lead to GC through combining bacterial factors with host factors. In this regard, identification of the major therapeutic targets against the host-HP interactions plays a critical role in GC prevention, diagnosis, and treatment.

AREAS COVERED

This study offers new insights into the promising therapeutic targets against the angiogenesis, invasion, or metastasis of GC from a host-HP interaction perspective. To this end, MEDLINE, EMBASE, LILACS, AIM, and IndMed databases were searched for relevant articles since 1992.

EXPERT OPINION

Wnt signaling and COX pathway have a well-documented history in the genesis of GC by HP and might be considered as the most promising targets for early GC treatment. Destroying HP may decrease the risk of GC, but it cannot fully hinder the GC development induced by HP infection. Therefore, targeting HP-activated pathways, especially COX-2/Wnt/beta-catenin/VEGF, TLR2/TLR9/COX-2, COX2-PGE2, and NF-κB/COX-2, as well as EPHA2, MMPs, and miR-543/SIRT1 axis, can be an effective measure in the early treatment of GC. However, different clinical trials and large, multi-center cohorts are required to validate these potentially effective targets for GC therapy.

Genetic variant of cyclooxygenase-2 in gastric cancer: More inflammation and susceptibility

Gastric cancer accounts for the majority cancer-related deaths worldwide. Although various methods have considerably improved the screening, diagnosis, and treatment of gastric cancer, its incidence is still high in Asia, and the 5-year survival rate of advanced gastric cancer patients is only 10%-20%. Therefore, more effective drugs and better screening strategies are needed for reducing the incidence and mortality of gastric cancer. Cyclooxygenase-2 (COX-2) is considered to be the key inducible enzyme in prostaglandins (PGs) synthesis, which is involved in multiple pathways in the inflammatory response. For example, inflammatory cytokines stimulate innate immune responses via Toll-like receptors and nuclear factor-kappa B to induce COX-2/PGE2 pathway. In these processes, the production of an inflammatory microenvironment promotes the occurrence of gastric cancer. Epidemiological studies have also indicated that non-steroidal anti-inflammatory drugs can reduce the risk of malignant tumors of the digestive system by blocking the effect of COX-2. However, clinical use of COX-2 inhibitors to prevent or treat gastric cancer may be limited because of potential side effects, especially in the cardiovascular system. Given these side effects and low treatment efficacy, new therapeutic approaches and early screening strategies are urgently needed. Some studies have shown that genetic variation in COX-2 also play an important role in carcinogenesis. However, the genetic variation analysis in these studies is incomplete and isolated, pointing out only a few single nucleotide polymorphisms (SNPs) and the risk of gastric cancer, and no comprehensive study covering the whole gene region has been carried out. In addition, copy number variation (CNV) is not mentioned. In this review, we summarize the SNPs in the whole COX-2 gene sequence, including exons, introns, and both the 5' and 3' untranslated regions. Results suggest that COX-2 does not increase its expression through the CNV and the SNPs in COX-2 may serve as the potential marker to establish risk stratification in the general population. This review synthesizes emerging insights of COX-2 as a biomarker in multiple studies, summarizes the association between whole COX-2 sequence variation and susceptibility to gastric cancer, and discusses the future prospect of therapeutic intervention, which will be helpful for early screening and further research to find new approaches to gastric cancer treatment.

Inflammatory myofibroblastic tumor in the head and neck-a neoplasm with both tumor features and inflammation

OBJECTIVE

The aim of this study was to unveil the reciprocal relation of tumor characteristics and inflammation in inflammatory myofibroblastic tumor in the head and neck.

STUDY DESIGN

The study included a retrospective cohort of patients with inflammatory myofibroblastic tumors treated between 2005 and 2017 in a tertiary hospital. Tumor features and inflammation were assessed through the expression of anaplastic lymphoma kinase (ALK), the degree of inflammation and cyclooxygenase-2 (COX-2) expression. The prognostic factors were analyzed for overall survival (OS) and disease-free survival (DFS) in univariate and multivariate analyses.

RESULTS

Forty-one patients diagnosed with inflammatory myofibroblastic tumors were followed up, and 41 paraffin sections were obtained. The positive rate of ALK expression was 21 (51.2%) of 41 patients. Nineteen patients had high-grade ALK expression, and 22 patients had low-grade ALK expression. Thirty-nine patients had high-grade inflammation, and 2 had low-grade inflammation. The positive rate of COX-2 expression was 100%. Tumors with both high-grade ALK expression and inflammation had worse DFS (P = .015). The multivariate Cox analysis showed that the grades of ALK expression and inflammation (P = .004) were independent risk factors for DFS.

CONCLUSIONS

Because of the latent synergistic effects of ALK and inflammation in the tumorigenesis of inflammatory myofibroblastic tumor, the combined therapy of ALK and COX-2 inhibitors shows promise.

Hydroxysafflor yellow A suppresses angiogenesis of hepatocellular carcinoma through inhibition of p38 MAPK phosphorylation

The antitumor effect of hydroxysafflor yellow A (HSYA), an active ingredient of the herb Carthamus tinctorius L. (Asteraceae) (safflower), was investigated in the current work. Researches of HSYA on vasculogenesis inhibition, along with the related molecular mechanisms, including the expression of MMP-2, MMP-9, and p38MAPK (COX-2, ATF-2, p-p38MAPK, and p38MAPK) signaling pathway in H22 tumor-bearing mice or HepG2 cells were performed. The animal experiments proved the level of MMP-2 and MMP-9 in H22-transplanted tumor tissue in mice markedly decreased by HSYA, and results both in vivo and in vitro confirmed that COX-2 expression was reduced significantly via p38MAPK|ATF-2 signaling pathway. According to the outcomes, HSYA suppressed p38MAPK phosphorylation in a concentration-dependent manner, while exerting no effect on the total p38MAPK protein expression. It was also showed that suppression of p38 activation by SB203580 decreased the HepG2 cell viability, proliferation, and migration, wherein HSYA exhibited a similar effect. Furthermore, Western blot analysis on caspase-3 and cleaved-caspase-3 revealed that HSYA could induce apoptosis of HepG2 cells. These findings provided experimental evidences that HSYA might be a promising anticancer agent for HCC.

Helicobacter pylori promotes invasion and metastasis of gastric cancer by enhancing heparanase expression

AIM

To detect the mechanisms of Helicobacter pylori (H. pylori) infection in the invasion and metastasis of gastric cancer (GC).

METHODS

Specimens from 99 patients with GC were collected. The correlation among H. pylori infection, heparanase (HPA) and mitogen-activated protein kinase (MAPK) expression, which was determined by immunohistochemistry, and the clinical features of GC was analysed using SPSS 22.0. Overall survival (OS) and relapse-free survival (RFS) of GC patients were estimated by the Kaplan-Meier method. Independent and multiple factors of HPA and MAPK with prognosis were determined with COX proportional hazards models. HPA and MAPK expression in MKN-45 cells infected with H. pylori was analysed using Western blot.

RESULTS

H. pylori infection was observed in 70 of 99 patients with GC (70.7%), which was significantly higher than that in healthy controls. H. pylori infection was related to lymph metastasis and expression of HPA and MAPK (P < 0.05); HPA expression was relevant to MAPK expression (P = 0.024). HPA and MAPK expression in MKN-45 cells was significantly upregulated following H. pylori infection and peaked at 24 h and 60 min, before decreasing (P < 0.05). SB203580, an inhibitor of MAPK, significantly decreased HPA expression. HPA was related to lymph metastasis and invasive depth. HPA positive GC cases and H. pylori positive GC cases showed poorer prognosis than HPA negative cases (P < 0.05). COX models showed that the prognosis of GC was connected with HPA expression, lymph metastasis, tissue differentiation, and invasive depth.

CONCLUSION

H. pylori may promote the invasion and metastasis of GC by increasing HPA expression that may associate with MAPK activation, thus causing a poorer prognosis of GC.

Molecular Signaling in Tumorigenesis of Gastric Cancer

Gastric cancer (GC) is regarded as the fifth most common cancer and the third cause of cancer-related deaths worldwide. Mechanism of GC pathogenesis is still unclear and relies on multiple factors, including environmental and genetic characteristics. One of the most important environmental factors of GC occurrence is infection with Helicobacter pylori that is classified as class one carcinogens. Dysregulation of several genes and pathways play an essential role during gastric carcinogenesis. Dysregulation of developmental pathways such as Wnt/β-catenin signaling, Hedgehog signaling, Hippo pathway, Notch signaling, nuclear factor-kB, and epidermal growth factor receptor have been found in GC. Epithelial-mesenchymal transition, as an important process during embryogenesis and tumorigenesis, is supposed to play a role in initiation, invasion, metastasis, and progression of GC. Although surgery is the main therapeutic modality of the disease, the understanding of biological processes of cell signaling pathways may help to develop new therapeutic targets for GC.

miR-30a acts as a tumor suppressor by double-targeting COX-2 and BCL9 in H. pylori gastric cancer models

Helicobacter pylori (H. pylori) is one of the most important factors that affect the development of gastric cancer, and its mechanism remains un-elucidated. Our present study found that, miR-30a is crucial for regulating the growth and migration of H. pylori infected gastric cancer in vitro by targeting COX-2 and BCL9. In details, double-stranded miR-30a precursor produced two single-stranded and matured miRNAs including miR-30a-3p and miR-30a-5p, which played significant biological functions in two different manners. First, miR-30a-3p inhibited COX-2 expression and regulated nuclear translocation of β-catenin, and second, miR-30a-5p targeted BCL9 to regulate TCF/LEF promoter activity followed by affecting β-catenin downstream target gene expression. In vivo, miR-30a knockout mice were successfully achieved using CRISPR/Cas9 gene editing technology. Compared with H. pylori-infected wild-type mice, H. pylori-infected miR-30a knockout mice showed increased incidence of chronic gastritis, chronic atrophic gastritis, atypical hyperplasia, and other precancerous lesions or adenocarcinoma manifestations in the antral or gastric mucosa of mice, as well as regulation of genes closely associated with tumor development. Taken together, miR-30a acts as a tumor suppressor by double-targeting COX-2 and BCL9, and significantly affects the development of H. pylori-induced gastric cancer, shedding new light on the mechanisms underlying H. pylori-associated gastric cancer.

Helicobacter pylori promotes angiogenesis depending on Wnt/beta-catenin-mediated vascular endothelial growth factor via the cyclooxygenase-2 pathway in gastric cancer

Background

Helicobacter pylori is an important pathogenic factor in gastric carcinogenesis. Angiogenesis (i.e., the growth of new blood vessels) is closely associated with the incidence and development of gastric cancer. Our previous study found that COX-2 stimulates gastric cancer cells to induce expression of the angiogenic growth factor VEGF through an unknown mechanism. Therefore, the aim of this study was to clarify the role of angiogenesis in H. pylori-induced gastric cancer development.

Methods

To clarify the relationship between H. pylori infection and angiogenesis, we first investigated H. pylori colonization, COX-2, VEGF, beta-catenin expression, and microvessel density (MVD) in gastric cancer tissues from 106 patients. In addition, COX-2, phospho-beta-catenin, and beta-catenin expression were measured by western blotting, and VEGF expression was measured by ELISA in H. pylori-infected SGC7901 and MKN45 human gastric cancer cells.

Results

H. pylori colonization occurred in 36.8 % of gastric carcinoma samples. Furthermore, COX-2, beta-catenin, and VEGF expression, and MVD were significantly higher in H. pylori-positive gastric cancer tissues than in H. pylori-negative gastric cancer tissues (P < 0.01). H. pylori infection was not related to sex or age in gastric cancer patients, but correlated with the depth of tumor invasion, lymph node metastasis, and tumor–node–metastasis stage (P < 0.05) and correlated with the COX-2 expression and beta-catenin expression(P < 0.01). Further cell experiments confirmed that H. pylori infection upregulated VEGF in vitro. Further analysis revealed that H. pylori-induced VEGF expression was mediated by COX-2 via activation of the Wnt/beta-catenin pathway.

Conclusions

The COX-2/Wnt/beta-catenin/VEGF pathway plays an important role in H. pylori-associated gastric cancer development. The COX-2/Wnt/beta-catenin pathway is therefore a novel therapeutic target for H. pylori-associated gastric cancers.

Both HDAC5 and HDAC6 are required for the proliferation and metastasis of melanoma cells

Background

Histone deacetylase (HDAC) inhibitors are widely used in clinical investigation as novel drug targets. For example, panobinostat and vorinostat have been used to treat patients with melanoma. However, HDAC inhibitors are small-molecule compounds without a specific target, and their mechanism of action is unclear. Therefore, it is necessary to investigate which HDACs are required for the proliferation and metastasis of melanoma cells.

Methods

We used overexpression and knocking down lentivirus to clarify the influence of HDAC5 and HDAC6 in melanoma development. Also, we introduced stable HDAC5 or HDAC6 knockdown cells into null mice and found that the knockdown cells were unable to form solid tumors. Finally, we tested HDAC5 and HDAC6 expression and sub-location in clinical melanoma tissues and tumor adjacent tissues.

Results

In this study, and found that HDAC5 and HDAC6 were highly expressed in melanoma cells but exhibited low expression levels in normal skin cells. Furthermore, we knocked down HDAC5 or HDAC6 in A375 cells and demonstrated that both HDAC5 and HDAC6 contributed to the proliferation and metastasis of melanoma cells.

Conclusions

This study demonstrated both HDAC5 and HDAC6 were required for melanoma cell proliferation and metastasis through different signaling pathways.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0753-0) contains supplementary material, which is available to authorized users.

Berberine Inhibits Invasion and Metastasis of Colorectal Cancer Cells via COX-2/PGE2 Mediated JAK2/STAT3 Signaling Pathway

Berberin, extracted from Chinese herbal medicine Coptis chinensis, has been found to have anti-tumor activities. However, the underlying mechanisms have not been fully elucidated. Our current study demonstrated that berberin inhibited the in vitro and in vivo growth, migration/invasion of CRC cells, via attenuating the expression levels of COX-2/PGE₂, following by reducing the phosphorylation of JAK2 and STAT3, as well as the MMP-2/-9 expression. We further clarified that an increase of COX-2/PGE₂ expression offset the repressive activity of Berberin on JAK2/STAT3 signaling, and a JAK2 inhibitor AZD1480 blocked the effect of COX-2/PGE₂ on MMP-2/-9 expression. In summary, Berberin inhibited CRC invasion and metastasis via down-regulation of COX-2/PGE₂- JAK2/STAT3 signaling pathway.

Helicobacter pylori infection, gastrin and cyclooxygenase-2 in gastric carcinogenesis

Gastric cancer is one of the most frequent neoplasms and a main cause of death worldwide, especially in China and Japan. Numerous epidemiological, animal and experimental studies support a positive association between chronic Helicobacter pylori (H. pylori) infection and the development of gastric cancer. However, the exact mechanism whereby H. pylori causes gastric carcinogenesis remains unclear. It has been demonstrated that expression of cyclooxygenase-2 (COX-2) is elevated in gastric carcinomas and in their precursor lesions. In this review, we present the latest clinical and experimental evidence showing the role of gastrin and COX-2 in H. pylori-infected patients and their possible association with gastric cancer risk.

Helicobacter pylori cytotoxin-associated gene A protein upregulates α-enolase expression via Src/MEK/ERK pathway: implication for progression of gastric cancer

Persistent infection with Helicobacter pylori confers an increased risk for the development of gastric cancer. In our previous investigations, we found that ENO1 was overexpression in cagA-positive H. pylori-infected gastric epithelial AGS cells by proteomic method, in contrast to the isogenic cagA knock out mutant H. pylori-infected cells. ENO1 is a newly identified oncoprotein overexpressed in some cancer. However, the relationship between H. pylori infection and ENO1 expression still remains undefined. The AGS gastric cancer cells were transfected with WT-cagA plasmid and PR-cagA plasmids. Expression of ENO1 mRNA and protein were measured by real-time quantitative PCR and western blot analysis. Signal protein inhibitor treatment was used to investigate the signal pathways. It was found that the ENO1 mRNA and protein overexpression levels were dependent on cagA gene expression and CagA protein phosphorylation. Further analysis revealed that the Src, MEK and ERK pathway was involved in this upregulation effect. Our data suggest that ENO1 was upregulated by CagA protein through activating the Src and MEK/ERK signal pathways, thereby providing a novel mechanism underlying H. pylori-mediated gastric diseases.

p50-associated COX-2 extragenic RNA (PACER) activates COX-2 gene expression by occluding repressive NF-κB complexes

Deregulated expression of COX-2 has been causally linked to development, progression, and outcome of several types of human cancer. We describe a novel fundamental level of transcriptional control of COX-2 expression. Using primary human mammary epithelial cells and monocyte/macrophage cell lines, we show that the chromatin boundary/insulator factor CTCF establishes an open chromatin domain and induces expression of a long non-coding RNA within the upstream promoter region of COX-2. Upon induction of COX-2 expression, the lncRNA associates with p50, a repressive subunit of NF-κB, and occludes it from the COX-2 promoter, potentially facilitating interaction with activation-competent NF-κB p65/p50 dimers. This enables recruitment of the p300 histone acetyltransferase, a domain-wide increase in histone acetylation and assembly of RNA Polymerase II initiation complexes. Our findings reveal an unexpected mechanism of gene control by lncRNA-mediated repressor occlusion and identify the COX-2-lncRNA, PACER, as a new potential target for COX-2-modulation in inflammation and cancer.

DOI:http://dx.doi.org/10.7554/eLife.01776.001

To produce a protein a cell must first transcribe the DNA in a gene to make a messenger RNA molecule, which is then translated to make the protein. However, cells also produce other types of RNA molecules which do not become proteins. MicroRNAs, for example, regulate the expression of genes as proteins, while the role of other RNA molecules called long non-coding RNAs (lncRNAs) is not well understood.

Now Krawczyk and Emerson have found an lncRNA that controls a gene called COX-2 that is often implicated in breast, colon, prostate, and lung cancer. This RNA molecule, which is called PACER, originates near the start of the COX-2 gene, but it cannot be messenger RNA because it does not contain the instructions to make the COX-2 protein, and it is too long to be a microRNA. Further experiments showed that the newly discovered lncRNA activates the expression of the COX-2 gene.

Krawczyk and Emerson found that PACER attracts enzymes that spotlight genes that need to be activated, thus increasing the transcription of these genes to make messenger RNA. Genes can also be switched on and off by various molecules binding to nearby DNA, and PACER encourages the activation of COX-2 by keeping away the molecules that might switch it off.

In addition to shedding new light on the role of lncRNAs, these results suggest that PACER could be a suitable therapeutic target in cancers that involve the COX-2 gene.

DOI:http://dx.doi.org/10.7554/eLife.01776.002

Helicobacter pylori enhances CIP2A expression and cell proliferation via JNK2/ATF2 signaling in human gastric cancer cells

Helicobacter pylori (H. pylori) infection plays an important role in the development of gastric carcinomas. Cancerous inhibitor of protein phosphatase 2A (CIP2A) is a novel human oncoprotein that functions as an important regulator of cell growth and malignant transformation. In the present study, we aimed to investigate the potential mechanisms by which H. pylori upregulates the expression of CIP2A and the functional impact of H. pylori-induced CIP2A in gastric cancer cells. We demonstrated that infection of MKN-45 cells with H. pylori led to a marked increase in the expression of CIP2A at the mRNA and protein levels. H. pylori-induced CIP2A was associated with increased cell proliferation. In addition, H. pylori was found to activate the JNK2 pathway. Importantly, both H. pylori-induced CIP2A production and cell proliferation were partially reversed by inhibition of JNK2 signaling. Similarly, the blockade of H. pylori-induced CIP2A expression by siRNA against CIP2A also inhibited cell proliferation. Thus, H. pylori appears to stimulate the expression of CIP2A and proliferation of gastric cancer cells via JNK2 signaling. These findings suggest that H. pylori-induced upregulation of CIP2A contributes to the development and progression of gastric cancer. Further in vivo studies are warranted to explore the biological role of CIP2A and its interaction with JNK2 signaling in gastric cancer.

Role of cyclooxygenase-2 in gastric cancer development and progression

Although the incidence of gastric cancer has been declining in recent decades, it remains a major public health issue as the second leading cause of cancer death worldwide. In China, gastric cancer is still the main cause of death in patients with malignant tumors. Most patients are diagnosed at an advanced stage and mortality is high. Cyclooxygenase-2 (COX-2) is a rate-limiting enzyme in prostanoid synthesis and plays an important role in the development and progression of gastric cancer. The expression of COX-2 in gastric cancer is upregulated and its molecular mechanisms have been investigated. Helicobacter pylori infection, tumor suppressor gene mutation and the activation of nuclear factor-kappa B may be responsible for the elevated expression of COX-2 in gastric cancer. The mechanisms of COX-2 in the development and progression of gastric cancer are probably through promoting the proliferation of gastric cancer cells, while inhibiting apoptosis, assisting angiogenesis and lymphatic metastasis, and participating in cancer invasion and immunosuppression. This review is intended to discuss, comment and summarize recent research progress on the role of COX-2 in gastric cancer development and progression, and elucidate the molecular mechanisms which might be involved in the carcinogenesis.

Expression and significance of cyclooxygenase-2 mRNA in benign and malignant ascites

AIM: To investigate the mRNA expression of cyclooxygensae-2 (COX-2) in benign and malignant ascites, and to explore the difference in COX-2 mRNA expression among different diseases.

METHODS: A total of 36 samples were collected from the Fifth Affiliated Hospital of Sun Yat-Sen University and divided into two experimental groups: benign ascites (n = 21) and malignant ascites (n = 15). Benign ascites included cirrhotic ascites (n = 10) and tuberculous ascites (n = 5). Malignant ascites included oophoroma (n = 7), cancer of colon (n = 5), cancer of the liver (n = 6), gastric cancer (n = 2), and bladder carcinoma (n = 1). The mRNA expression of COX-2 in ascites was examined with reverse transcriptase polymerase chain reaction (RT-PCR) technology, and the positive rate of COX-2 mRNA was compared between different diseases.

RESULTS: The positive rate of COX-2 mRNA in malignant ascites was 42.9% (9/21), which was significantly higher than in benign ascites, 6.7% (1/15), difference being significant between these two groups (χ² = 4.051, P = 0.044). The proportion of the positive rate in the malignant ascites was as follows: ovarian cancers 57.1% (4/7), colon cancer 40.0% (2/5), liver cancer 33.3% (2/6), gastric cancer 50.0% (1/2), and bladder cancer 0.00% (0/1). However, there was no significant difference in COX-2 mRNA expression among various tumors with malignant ascites (χ² = 1.614, P = 0.806). Among the benign ascites, COX-2 mRNA levels were different between the tuberculous ascites (0/5) and cirrhotic ascites (1/10), but there was no significant difference (P = 1.000).

CONCLUSION: COX-2 mRNA, detected by RT-PCR, is useful in the differential diagnosis of benign and malignant ascites, which also has potential value in the clinical diagnosis of tumors.

Cyclooxygenase-2 and gastric cancer

Gastric cancer remains a leading cause of cancer-related deaths worldwide, although its incidence has been steadily declining during recent decades. Expression of cyclooxygenase-2 (COX-2) is elevated in gastric carcinomas and in their precursor lesions. COX-2 expression associates with reduced survival in gastric cancer patients, and it has also been shown to be an independent factor of poor prognosis. Several molecular mechanisms are involved in the regulation of COX-2 expression in gastric cancer cell lines, including signal transduction pathways activated by Helicobacter pylori. In gastric tumor models in vivo the role of COX-2 seems to be predominantly to facilitate tumor promotion and growth.

Helicobacter pylori infection increases the transcriptional activity of COX-2 promoter via the p38MAPK signal transduction pathway in MKN45 cells

AIM: To investigate the effect of Helicobacter pylori (H.pylori) infection on the transcriptional activity of cyclooxygenase-2 (COX-2) promoter in gastric cancer MKN45 cells and to explore potential mechanisms involved.

METHODS: The recombinant vector pGL3-Basic-COX-2-promoter and a control vector (pRL-SV40) was transiently co-transfected into MKN45 cells. Twelve hours later, the transfected cells were infected with H.pylori (100 times the number of cells) for different durations. The COX-2 promoter activity was detected using the dual luciferase assay. The activation of p38MAPK pathway was evaluated by Western blot. The p38MAPK signal transduction pathway was then blocked with a specific inhibitor SB203580 to detect the effect of H.pylori infection on COX-2 promoter activity.

RESULTS: After transient transfection, the activity of COX-2 promoter in MKN45 cells was increased with time. At 40 h after transfection, the activity of dual-luciferase was 3.5 folds higher than that at 8 h (P < 0.05). H.pylori infection significantly increased the activity of dual-luciferase compared with control cells (all P < 0.05 or 0.01). The activity of dual-luciferase in cells infected with H.pylori at 40 h after transfection was 5 folds higher than that at 8 h (P < 0.01). The expression of p38MAPK was up-regulated at 20 min after infection and reached the peak at 60 min. Blockage of the p38MAPK signal transduction pathway with SB203580 significantly reduced the COX-2 promoter activity.

CONCLUSION: H.pylori infection increases the transcriptional activity of COX-2 promoter via the p38MAPK signal transduction pathway, which may be one of the important mechanisms by which H.pylori infection causes gastric cancer.

Helicobacter pylori gamma-glutamyl transpeptidase is a pathogenic factor in the development of peptic ulcer disease

BACKGROUND & AIMS

gamma-Glutamyl transpeptidase (GGT) has been reported to be a virulence factor of Helicobacter pylori associated with bacterial colonization and cell apoptosis. But its mechanism of pathogenesis is not firmly established. This study aims to examine its role in H pylori-mediated infection.

METHODS

Various H pylori isogenic mutants were constructed by a polymerase chain reaction (PCR) approach. H pylori native GGT protein (HP-nGGT) was purified with ion-exchange and gel-filtration chromatography. Generation of H2O2 was measured with fluorimetric analysis, whereas nuclear factor-kappaB (NF-kappaB) activation was determined by luciferase assay and Western blot. Cytokine production was examined by enzyme-linked immunoabsorbent assay and real-time PCR. DNA damage was assessed with comet assay and flow cytometry. The GGT activity of 98 H pylori isolates was analyzed by an enzymatic assay.

RESULTS

Purified HP-nGGT generated H2O2 in primary gastric epithelial cells and AGS gastric cancer cells, resulting in the activation of NF-kappaB and up-regulation of interleukin-8 (IL-8) production. In addition, HP-nGGT caused an increase in the level of 8-OH-dG, indicative of oxidative DNA damage. In contrast, Deltaggt showed significantly reduced levels of H2O2 generation, IL-8 production, and DNA damage in cells compared with the wild type (P<.05). The clinical importance of GGT was indicated by significantly higher (P<.001) activity in H pylori isolates obtained from patients with peptic ulcer disease (n=54) than isolates from patients with nonulcer dyspepsia (n=44).

CONCLUSION

Our findings provide evidence that GGT is a pathogenic factor associated with H pylori-induced peptic ulcer disease.

Establishment of a mouse model of chronic Helicobacter pylori infection-induced gastric adenocarcinoma and investigation of the effect of Helicobacter pylori infection on angiogenesis

AIM: To investigate the carcinogenicity of long-term Helicobacter pylori (H.pylori) infection in C57BL/6 mice and to investigate the role of angiogenesis in the pathogenesis of H.pylori infection-induced gastric cancer.

METHODS: Eighty male C57BL/6 mice of SPF grade were equally and randomly divided into normal group and model group. The normal group was fed normally, while the model group was inoculated by oral gavage with H.pylori SS1. Mice were sacrificed at weeks 10, 25, 45 and 72 after the last inoculation. H.pylori infection was analyzed by rapid urease test and Giemsa staining. The pathological changes in the gastric mucosa of mice were assessed by hematoxylin-eosin staining. Microvessel density (MVD) was detected by immunohistochemistry.

RESULTS: No H.pylori infection was detected in the gastric antrum, gastric body and duodenal mucosa in the normal group. The rates of H.pylori colonization were 88.9%, 100%, 100% and 100% at weeks 10, 25, 45 and 72 in the model group. At week 72, the incidence rates of chronic gastritis, atrophic gastritis, intestinal metaplasia, dysplasia and gastric cancer were 100%, 88.9%, 77.8%, 33.3% and 22.2% in the model group, respectively. The MVD in the gastric mucosa in the model group was 18.56 ± 2.62, significantly higher than that in the normal group (P < 0.01).

CONCLUSION: A mouse model of chronic H.pylori infection-induced gastric adenocarcinoma has been established successfully. H.pylori infection can increase the MVD in the gastric mucosa in C57BL/6 mice and therefore play an important role in the development of gastric cancer.

Helicobacter pylori CagA upregulation of CIP2A is dependent on the Src and MEK/ERK pathways

Helicobacter pylori is classified as a class I carcinogenic factor and its persistent colonization in the stomach induces gastric cancer. Cancerous Inhibitor of PP2A (CIP2A) is a newly identified oncoprotein overexpressed in gastric cancer. Serving as a key oncoprotein, CIP2A also participates in regulation of senescence and proliferation of gastric cells. The combination of aberrant CIP2A expression inducing unlimited cell proliferation, and H. pylori infection eliciting aberrant expression of some key proteins, results in the onset of gastric tumorigenesis. However, the relationship between H. pylori infection and CIP2A expression still remains undefined. The aim of our study was to verify the effect of H. pylori infection on CIP2A expression levels and identify H. pylori signalling molecules and corresponding pathways influencing CIP2A expression. Following plasmid-mediated expression of CagA in human gastric cell lines, the cells were infected with H. pylori and CIP2A expression levels were examined by immunoblotting. Signal inhibitors were used to verify which signal pathways were involved. We also performed CIP2A depletion and H. pylori infection after depletion in AGS cells. H. pylori infection-induced CIP2A expression was dependent on cagA gene expression and CagA phosphorylation. Bacterial oncoprotein CagA upregulated CIP2A expression and this upregulation effect was dependent on Src and Ras/mitogen-activated protein kinase kinase/extracellular signal-regulated kinase pathways. H. pylori infection-induced Myc stabilization was partially attenuated by CIP2A depletion. The results of our study provide further information for understanding the mechanism of H. pylori carcinogenesis.