Cyclooxygenase-2 expression and its association with angiogenesis, Helicobacter pylori, and clinicopathologic characteristics of gastric carcinoma

Linking dysbiosis to precancerous stomach through inflammation: Deeper than and beyond imaging

Upper gastrointestinal endoscopy is considered the gold standard for gastric lesions detection and surveillance, but it is still associated with a non-negligible rate of missing conditions. In the Era of Personalized Medicine, biomarkers could be the key to overcome missed lesions or to better predict recurrence, pushing the frontier of endoscopy to functional endoscopy. In the last decade, microbiota in gastric cancer has been extensively explored, with gastric carcinogenesis being associated with progressive dysbiosis. Helicobacter pylori infection has been considered the main causative agent of gastritis due to its interference in disrupting the acidic environment of the stomach through inflammatory mediators. Thus, does inflammation bridge the gap between gastric dysbiosis and the gastric carcinogenesis cascade and could the microbiota-inflammation axis-derived biomarkers be the answer to the unmet challenge of functional upper endoscopy? To address this question, in this review, the available evidence on the role of gastric dysbiosis and chronic inflammation in precancerous conditions of the stomach is summarized, particularly targeting the nuclear factor-κB (NF-κB), toll-like receptors (TLRs) and cyclooxygenase-2 (COX-2) pathways. Additionally, the potential of liquid biopsies as a non-invasive source and the clinical utility of studied biomarkers is also explored. Overall, and although most studies offer a mechanistic perspective linking a strong proinflammatory Th1 cell response associated with, but not limited to, chronic infection with Helicobacter pylori, promising data recently published highlights not only the diagnostic value of microbial biomarkers but also the potential of gastric juice as a liquid biopsy pushing forward the concept of functional endoscopy and personalized care in gastric cancer early diagnosis and surveillance.

Helicobacter pylori infection induces gastric precancerous lesions and persistent expression of Angpt2, Vegf-A and Tnf-A in a mouse model

Introduction

Helicobacter pylori colonizes the gastric mucosa and induces chronic inflammation.

Methods

Using a mouse model of H. pylori-induced gastritis, we evaluated the mRNA and protein expression levels of proinflammatory and proangiogenic factors, as well as the histopathological changes in gastric mucosa in response to infection. Five- to six-week-old female C57BL/6N mice were challenged with H. pylori SS1 strain. Animals were euthanized after 5-, 10-, 20-, 30-, 40- and 50-weeks post infection. mRNA and protein expression of Angpt1, Angpt2, VegfA, Tnf-α, bacterial colonization, inflammatory response and gastric lesions were evaluated.

Results

A robust bacterial colonization was observed in 30 to 50 weeks-infected mice, which was accompanied by immune cell infiltration in the gastric mucosa. Compared to non-infected animals, H. pylori-colonized animals showed an upregulation in the expression of Tnf-A, Angpt2 and VegfA at the mRNA and protein levels. In contrast, Angpt1 mRNA and protein expression was downregulated in H. pylori-colonized mice.

Conclusion

Our data show that H. pylori infection induces the expression of Angpt2, Tnf-A and Vegf-A in murine gastric epithelium. This may contribute to the pathogenesis of H. pylori-associated gastritis, however the significance of this should be further addressed.

The JMJD Family Histone Demethylases in Crosstalk Between Inflammation and Cancer

Inflammation has emerged as a key player in regulating cancer initiation, progression, and therapeutics, acting as a double edged sword either facilitating cancer progression and therapeutic resistance or inducing anti-tumor immune responses. Accumulating evidence has linked the epigenetic modifications of histones to inflammation and cancer, and histone modifications-based strategies have shown promising therapeutic potentials against cancer. The jumonji C domain-containing (JMJD) family histone demethylases have exhibited multiple regulator functions in inflammatory processes and cancer development, and a number of therapeutic strategies targeting JMJD histone demethylases to modulate inflammatory cells and their products have been successfully evaluated in clinical or preclinical tumor models. This review summarizes current understanding of the functional roles and mechanisms of JMJD histone demethylases in crosstalk between inflammation and cancer, and highlights recent clinical and preclinical progress on harnessing the JMJD histone demethylases to regulate cancer-related inflammation for future cancer therapeutics.

Interleukin-32: Frenemy in cancer?

Interleukin-32 (IL-32) was originally identified in natural killer (NK) cells activated by IL-2 in 1992. Thus, it was named NK cell transcript 4 (NK4) because of its unknown function at that time. The function of IL-32 has been elucidated over the last decade. IL-32 is primarily considered to be a booster of inflammatory reactions because it is induced by pro-inflammatory cytokines and stimulates the production of those cytokines and vice versa. Therefore, many studies have been devoted to studying the roles of IL-32 in inflammation-associated cancers, including gastric, colon cancer, and hepatocellular carcinoma. At the same time, roles of IL-32 have also been discovered in other cancers. Collectively, IL-32 fosters the tumor progression by nuclear factor-κB (NF-κB)-mediated cytokines and metalloproteinase production, as well as stimulation of differentiation into immunosuppressive cell types in some cancer types. However, it is also able to induce tumor cell apoptosis and enhance NK and cytotoxic T cell sensitivity in other cancer types. In this review, we will address the function of each IL-32 isoform in different cancer types studied to date, and suggest further strategies to comprehensively elucidate the roles of IL-32 in a context-dependent manner.

The Pattern of Signatures in Gastric Cancer Prognosis

Gastric cancer is one of the most common malignancies worldwide and it is a fourth leading cause of cancer-related death. Carcinogenesis is a multistage disease process specified by the gradual procurement of mutations and epigenetic alterations in the expression of different genes, which finally lead to the occurrence of a malignancy. These genes have diversified roles regarding cancer development. Intracellular pathways are assigned to the expression of different genes, signal transduction, cell-cycle supervision, genomic stability, DNA repair, and cell-fate destination, like apoptosis, senescence. Extracellular pathways embrace tumour invasion, metastasis, angiogenesis. Altered expression patterns, leading the different clinical responses. This review highlights the list of molecular biomarkers that can be used for prognostic purposes and provide information on the likely outcome of the cancer disease in an untreated individual.

Heterogeneity of COX-2 and Multidrug Resistance between Primary Tumors and Regional Lymph Node Metastases of Gastric Cancer

Aims and background

Cyclooxygenase-2 (COX-2) is involved in the progression of gastric cancer; however, the role of COX-2 in multidrug resistance (MDR) is still unclear. This study aimed to elucidate the relationship between COX-2 and MDR so as to show the heterogeneity of gastric primary tumors and regional lymph node metastases.

Methods

Between 2008 and 2009, 56 primary tumor samples and paired metastatic lymph node tissues from gastric cancer patients confirmed by surgery and pathological examination in our hospital were collected. The expression levels of COX-2 and MDR-associated factors such as P-glycoprotein (P-gp), glutathione S-transferase pi (GST-π) and topoisomerase II alpha (Topo-II-α) were determined by immunohistochemical staining. Tumor cells from these tissues were cultured and the cell chemosensitivities for 11 chemotherapeutic agents were measured by sulforhodamine B assay.

Results

The expression levels of COX-2, P-gp and GST-π were significantly higher in metastatic lymph node tissues than in primary tumors, while the expression level of Topo-II-α was lower in metastatic lymph node tissues than in primary tumors (all P <0.05). In primary tumors, COX-2 and GST-π were positively correlated and COX-2 and Topo-II-α were negatively correlated; in metastatic lymph node tissues, a positive correlation was found between COX-2 and P-gp (all P <0.05). The inhibition rates of eADM, VP-16, THP and MMC on cells from primary tumors were significantly lower than those on cells from metastatic lymph nodes, while the inhibition rates of HCPT, L-OHP and VCR on cells from metastatic lymph nodes were lower than those on cells from primary tumors.

Conclusion

The expression of COX-2 and MDR-associated factors as well as cell chemosensitivities are different in primary tumors and regional lymph node metastases of gastric cancer, and this may be an indication of their heterogeneity.

Clinical and prognosis relevance of COX-2 expression in Tunisian patients with primary gastric adenocarcinoma

BACKGROUND

Inflammation and hormonal signalling induce the cyclooxygenase-2 (COX-2) expression in various human cancers including Gastric Cancer (GC). GC remains among the human malignancies diagnosticated at advanced tumor stage and thus having a poor prognosis. COX-2 is a key protein in cancer progression which is involved in proliferation, invasion, and metastasis of tumor cells.

OBJECTIVE

The aim of this study was to investigate the expression of COX-2 and its association with clinico-patholocigal parameters and survival in Tunisian GC patients and to correlate COX-2 expression with others cancer-related proteins.

METHODS

The immunohistochemistry was used to study the expression of COX-2 on 93 patients with gastric adenocarcinoma.

RESULTS

Our results show that COX-2 immunostaining is negative to weak in 51.6%, moderate in 33.3%, and intense in 15.1% of tumor tissues. The expression of COX-2 associated significantly with tumor differentiation (p = 0.003), and histological type (p = 0.039). Furthermore, lack of COX-2 expression is significantly associated with 1-year (p= 0.005), 2-years (p= 0.000), and 5-years (p= 0.042) relapse free survival. In addition, Cox regression model, revealed that metastasis (p= 0.014), tumor site (p= 0.013), histotype (p = 0.02), and COX-2 expression (p = 0.003) are independent factors for prognosis. Regarding the relationship between COX-2 and cancer related proteins, we found that COX-2 expression is positively associated with APC (p = 0.006), and P53 (p = 0.026), supporting a cross link between these proteins in gastric carcinogenesis.

CONCLUSION

Our findings emphasize the importance of COX-2 as a potential marker of tumor progression and prognosis in GC, and that the inhibition of COX-2 activity may have a therapeutic benefit in GC.

Immunohistochemical angiogenic biomarkers in hepatocellular carcinoma and cirrhosis: correlation with pathological features

OBJECTIVE

To investigate immunohistochemical markers of angiogenesis and their association with pathological prognostic features in hepatocellular carcinoma and cirrhotic liver.

METHODS

Vascular endothelial growth factor, CD105, and cyclooxygenase-2 were immunohistochemically detected in 52 hepatocellular carcinoma tissue samples and 48 cirrhotic liver tissue samples. Semiquantitative measurements of vascular endothelial growth factor and cyclooxygenase-2 were evaluated considering the degree and intensity of immunostaining based on a 7-point final scoring scale. CD105 microvascular density (MVD-CD105) was measured using automated analysis. Morphological aspects evaluated in the hepatocellular carcinoma samples included size (≤2 and >2 cm), differentiation grade, and microvascular invasion.

RESULTS

The mean vascular endothelial growth factor immunoreactivity score was slightly higher in the hepatocellular carcinoma samples (4.83±1.35) than the cirrhotic liver (4.38±1.28) samples. There was a significant and direct correlation between these mean scores (rs=0.645, p=0.0001). Cyclooxygenase-2 was expressed in all the cirrhotic liver samples but was only found in 78% of the hepatocellular carcinoma samples. The mean cyclooxygenase-2 score was higher in the cirrhotic liver samples (4.85±1.38) than the hepatocellular carcinoma samples (2.58±1.68), but there was no correlation between the scores (rs=0.177, p=0.23). The mean CD105 percentage in the hepatocellular carcinoma samples (11.2%) was lower than that in the cirrhotic samples (16.9%). There was an inverse relationship in MVD-CD105 expression between the hepatocellular carcinoma and cirrhotic samples (rs=-0.78, p=0.67). There were no significant associations between vascular endothelial growth factor expression and morphological characteristics. Cyclooxygenase-2 and CD105 were associated with hepatocellular carcinoma differentiation grade (p=0.003 and p=0.05, respectively).

CONCLUSION

Vascular endothelial growth factor, cyclooxygenase-2, and MVD-CD105 were highly expressed in cirrhotic liver compared to hepatocellular carcinoma and might be involved in liver carcinogenesis. Additionally, cyclooxygenase-2 and CD105 might be involved in hepatocellular carcinoma differentiation grade.

Expression of cyclooxygenase 2 and vascular endothelial growth factor in gastric carcinoma: Relationship with clinicopathological parameters

BACKGROUND

Gastric cancer is one of the most common cancers and the second most common cause of cancer-related death worldwide. Identification of specific prognostic indicators might allow a better prognostic stratification and more effective therapy.

AIM

To assess the expression and relationship between COX-2 and VEGF protein in gastric adenocarcinoma and whether these markers are useful in predicting clinicopathological prognostic parameters.

MATERIALS AND METHODS

The study included 83 formalin-fixed paraffin embedded tissue samples of excised gastric adenocarcinoma and 20 non tumorous tissue controls. The slides were subjected to COX-2 and VEGF immunohistochemical staining using a streptavidin-biotinperoxidase according to the manufacturer's protocol. The results were assessed independently by two pathologists. The relationships among COX-2 and VEGF expression and clinicopathological parameters were statistically analyzed.

RESULTS

COX-2 and VEGF expressions were obviously higher in carcinoma tissues compared to normal mucosae (p<0.001). The expression rate of COX-2 was 54.2% and of VEGF was 68.7%. COX-2 positive tumors were significantly correlated with Lauren classification, tumor depth and Helicobacter pylori infection (p<0.001, p=0.008, p=0.035). VEGF was significantly associated with lymph node metastasis and tumor depth (p<0.001). There was a positive association between VEGF and COX-2 expression in gastric adenocarcinoma (Kappa value=0.55).

CONCLUSION

In gastric adenocarcinoma, COX-2 expression might serve as a powerful indicator for intestinal type carcinoma, locally advanced disease and H. pylori infection, while VEGF was related to loco-regional progression. COX-2 might be involved in the development of angiogenesis in gastric carcinoma through VEGF upregulation.

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.

Helicobacter pylori in gastric carcinogenesis

Gastric cancer still is a major concern as the third most common cancer worldwide, despite declining rates of incidence in many Western countries. Helicobacter pylori (H. pylori) is the major cause of gastric carcinogenesis, and its infection insults gastric mucosa leading to the occurrence of atrophic gastritis which progress to intestinal metaplasia, dysplasia, early gastric cancer, and advanced gastric cancer consequently. This review focuses on multiple factors including microbial virulence factors, host genetic factors, and environmental factors, which can heighten the chance of occurrence of gastric adenocarcinoma due to H. pylori infection. Bacterial virulence factors are key components in controlling the immune response associated with the induction of carcinogenesis, and cagA and vacA are the most well-known pathogenic factors. Host genetic polymorphisms contribute to regulating the inflammatory response to H. pylori and will become increasingly important with advancing techniques. Environmental factors such as high salt and smoking may also play a role in gastric carcinogenesis. It is important to understand the virulence factors, host genetic factors, and environmental factors interacting in the multistep process of gastric carcinogenesis. To conclude, prevention via H. pylori eradication and controlling environmental factors such as diet, smoking, and alcohol is an important strategy to avoid H. pylori-associated gastric carcinogenesis.

Expression and clinical significance of cyclooxygenase-2 and interleukin-32 in primary gastric B-cell lymphoma

Cyclooxygenase-2 (COX-2) and interleukin-32 (IL-32) expression has been examined in various carcinomas and inflammations, and has been suggested to be significant in tumor progression and prognosis. The present study was conducted to investigate the expression of COX-2 and IL-32 in primary gastric B-cell lymphoma in order to define their clinical significance and their association with Helicobacter pylori (Hp) infection. COX-2 and IL-32 protein expression was detected in 31 primary gastric B-cell lymphoma patients and 19 chronic gastritis patients with immunohistochemistry. COX-2 and IL-32 expression was significantly higher in primary gastric lymphoma (PGL) tissues compared with gastritis tissues (51.6 vs. 21.1% for COX-2, P=0.032; and 58.1 vs. 26.3% for IL-32, P=0.029) and was significantly higher in Hp⁺ lymphoma tissues compared with Hp^- lymphoma tissues (66.7 vs. 20% for COX-2, P=0.015; and 71.4 vs. 30% for IL-32, P=0.029). In the PGL tissues, the expression level of COX-2 was positively correlated with the expression level of IL-32, and the two were each positively correlated with Hp infection (P=0.004 for COX-2 and IL-32; P=0.01 for COX-2 and Hp infection; and P=0.003 for IL-32 and Hp infection). COX-2 expression was found to be significantly associated (P<0.05) with an aggressive tumor type, higher expression of Ki-67, frequent lymph node metastasis and advanced stage. IL-32 expression was found to be significantly correlated (P<0.05) with frequent lymph node metastasis and an advanced stage. The survival time was longer in the COX-2^- and IL-32^- lymphoma patients compared with the COX-2⁺ and IL-32⁺ lymphoma patients, but these differences were not statistically significant. These results suggested that Hp infection and the expression of COX-2 and IL-32 were closely linked with each other, and that the overexpression of COX-2 and IL-32 was correlated with tumor progression in primary gastric B-cell lymphoma, thus indicating potential novel therapeutic target.

Angiogenic and growth factors in gastric cancer

BACKGROUND

Antiangiogenic treatment is at the horizon in the palliative treatment of gastric cancer (GC), but data on proangiogenic biomarkers are still limited. The aim of this study was to analyze five proteins with a function in tumor angiogenesis: vascular endothelial growth factor (VEGF), angiopoietin-2 (Ang-2), follistatin, leptin, and platelet endothelial cell adhesion molecule 1 (CD31) in peripheral blood and corresponding tumor tissue.

MATERIAL AND METHODS

From 2008-2010, tumor tissue (n = 76) and corresponding preoperative serum (n = 69) of patients with localized GC were collected; 45 had perioperative chemotherapy. Protein serum or tumor lysate levels of these factors were measured by an angiogenesis multiplex immunoassay and correlated with response and survival.

RESULTS

Serum Ang-2 had prognostic relevance in the whole study population (P = 0.027). In subgroup analysis, serum VEGF and Ang-2 had prognostic relevance in primarily resected patients (P = 0.028; P = 0.048) but no association was found in neoadjuvantly treated patients. Follistatin concentration in the tumor tissue was associated with prognosis in all patients (P = 0.019). Tumor VEGF concentrations were correlated with histopathologic response (P = 0.011), with patients showing >50% remaining tumor having higher VEGF concentrations. The tissue Ang-2/VEGF ratio was significantly correlated with both clinical and histopathologic response (P = 0.029, P = 0.009). Additionally, the level of leptin in the tissue was associated with clinical response: nonresponding patients had higher leptin levels than those of responding patients (P = 0.032).

CONCLUSIONS

Our results show the importance of angiogenetic factors in serum and tumor tissue in GC for prognosis and treatment response. Further trials in larger patient populations are warranted for a further evaluation of proangiogenetic factors as biomarkers in gastrointestinal cancer.

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.

Cyclooxygenase-2 expression is associated with poor overall survival of patients with gastric cancer: a meta-analysis

BACKGROUND

Cyclooxygenase-2 (COX-2) is believed to be involved in gastric carcinogenesis. However, it is still controversial whether COX-2 expression can be regarded as a prognostic factor for gastric cancer patients.

AIM

To obtain a more accurate relationship between COX-2 overexpression and prognosis in gastric cancer by meta-analysis.

METHOD

Relevant articles published up to May 2013 were searched by use of several keywords in electronic databases. Separate hazard ratio (HR) estimates and 95 % confidence intervals (95 % CI) for COX-2 overexpression and overall survival (OS) and disease-free survival (DFS) with gastric cancer were extracted. Combined HR with 95 % CI was calculated by use of Stata11.0 software to estimate the size of the effect. Publication bias testing and sensitivity analysis were also performed.

RESULTS

A total of 27 studies which included 3,891 gastric cancer patients were combined in the final analysis. Combined results suggested that COX-2 overexpression was associated with an unfavorable OS (HR 1.58, 95 % CI 1.36-1.84) but not DFS (HR 1.15, 95 % CI 0.93-1.43) among patients with gastric cancer. Publication bias was absent. Sensitivity analysis suggested that the results of this meta-analysis were robust.

CONCLUSIONS

The results of this meta-analysis suggest that high COX-2 expression may be an independent risk factor for poor OS of patients with gastric cancer. More large prospective studies are now needed to further clarify the prognostic value of COX-2 expression for DFS in gastric cancer.

The Effect of Helicobacter pylori on Epidermal Growth Factor Receptor-Induced Signal Transduction and the Preventive Effect of Celecoxib in Gastric Cancer Cells

Background/Aims

Helicobacter pylori infection induces cyclooxygenase-2 (COX-2) and epidermal growth factor receptor (EGFR) overexpression, and these factors may engage in cross-talk. The aim of the present study was to evaluate the effect of H. pylori on EGFR signaling pathways and to determine whether celecoxib has an inhibitory effect on this pathway.

Methods

The AGS cell line was cocultured with H. pylori G27 and the isogenic cagE- mutant. The expression of COX-2, EGFR, heparin binding-epidermal growth factor (HB-EGF), and transforming growth factor-β (TGF-β) was measured by real time-polymerase chain reaction (RT-PCR). Next, Western blot analyses of COX-2, EGFR, total Akt, phosphorylated Akt (pAkt), and phosphorylated glycogen synthase kinase-3β (pGSK3β) were performed after incubating H. pylori-treated AGS cells for 24 hours with various concentrations of celecoxib (0, 10, 20, and 30 µmol/L).

Results

H. pylori infection upregulated the mRNA levels of COX-2, EGFR, HB-EGF, and TGF-β, as detected by RT-PCR. However, AGS cells treated with cagE- mutants, which have a defective type IV secretion system, did not exhibit EGFR upregulation. Celecoxib had inhibitory effects on the H. pylori-induced overexpression of COX-2 (p=0.015), EGFR (p=0.025), pAkt (p=0.025), and pGSK3β (p=0.029) by Western blot analysis.

Conclusions

H. pylori with an intact type IV secretion system activated the COX-2 and EGFR-Akt pathways in the AGS cell line. As celecoxib exhibited inhibitory effects on the EGFR signaling pathway, the cross-talk of COX-2 and EGFR likely mediates H. pylori-induced gastric cancer.

Involvement of nuclear factor κB (NF-κB) in the downregulation of cyclooxygenase-2 (COX-2) by genistein in gastric cancer cells

Genistein induces growth inhibition in various human cancer cell lines but its mechanism of action remains unknown. This study determined whether the effect of genistein is mediated via suppression of cyclo-oxygenase (COX)-2 protein, and elucidated the mechanism of action of this effect in the human gastric cancer cell line BGC-823. Genistein treatment inhibited cell proliferation and induced apoptosis in a dose- and time-dependent manner; Western blotting analysis indicated a significant dose-dependent decrease in COX-2 protein levels. Genistein treatment exerted a significant inhibitory effect on activation of the transcription factor nuclear factor κB (NF-κB). Additionally, the NF-κB inhibitor pyrrolidine dithiocarbamate caused a reduction in COX-2 protein levels and NF-κB activation, similar to the effect of genistein. Suppression of COX-2 protein may be important for the antiproliferative and proapoptotic effects of genistein in BGC-823 cells, and these effects may be partly mediated through the NF-κB pathway.

Inactivation of COX-2, HMLH1 and CDKN2A gene by promoter methylation in gastric cancer: relationship with histological subtype, tumor location and Helicobacter pylori genotype

OBJECTIVE

We aimed to evaluate the inactivation of COX-2, HMLH1 and CDKN2A by promoter methylation and its relationship with the infection by different Helicobacter pylori strains in gastric cancer.

METHODS

DNA extracted from 76 H. pylori-positive gastric tumor samples was available for promoter methylation identification by methylation-specific PCR and H. pylori subtyping by PCR. Immunohistochemistry was used to determine COX-2, p16(INK4A) and HMLH1 expression.

RESULTS

A strong negative correlation was found between the expression of these markers and the presence of promoter methylation in their genes. Among cardia tumors, negativity of p16(INK4A) was a significant finding. On the other hand, in noncardia tumors, the histological subtypes had different gene expression patterns. In the intestinal subtype, a significant finding was HMLH1 inactivation by methylation, while in the diffuse subtype, CDKN2A inactivation by methylation was the significant finding. Tumors with methylated COX-2 and HMLH1 genes were associated with H. pylori vacA s1 (p = 0.025 and 0.047, respectively), and the nonmethylated tumors were associated with the presence of the gene flaA.

CONCLUSIONS

These data suggest that the inactivation of these genes by methylation occurs by distinct pathways according to the histological subtype and tumor location and depends on the H. pylori genotype.

Gastric carcinogenesis

INTRODUCTION

In most patients, gastric cancer is diagnosed in advanced stage. Curative treatment options are limited and the mortality is high. The process of gastric carcinogenesis is triggered by Helicobacter pylori-driven gastritis and is further characterized by its complexity of interaction with other risk factors. Health care systems are challenged for the improvement of prevention, early diagnosis, and effective treatments.

METHODS

An extensive literature research has been performed to elucidate the interplay between etiological factors involved in gastric carcinogenesis.

RESULTS

H. pylori is the most important carcinogen for gastric adenocarcinoma. Evidence is provided by experiments including animal studies as well as clinical observational and interventional studies in humans. Eradication has the potential to prevent gastric cancer and offers the greatest benefit if performed before premalignant changes of the gastric mucosa have occurred. Bacterial virulence factors are essential players in modulating the immune response involved in the initiation of the carcinogenesis in the stomach. Host genetic factors contribute to the regulation of the inflammatory response and in the aggravation of mucosal damage. The harmful role of environmental factors is restricted to salt intake and smoking of tobacco. The ingestion of fruit and vegetables has some protective effect.

CONCLUSION

Infection with H. pylori is the major risk factor for gastric cancer development, and thus, eradication of the Helicobacter offers a promising best option for prevention of the disease. Bacterial virulence, host genetic factors, and environmental influences are interacting in the multifactorial process of gastric carcinogenesis.

Sinomenine inhibits proliferation of SGC-7901 gastric adenocarcinoma cells via suppression of cyclooxygenase-2 expression

Sinomenine (SIN) is a bioactive alkaloid extracted from the Chinese medicinal plant Sinomenium acutum. Results of studies have shown that the anti-inflammatory, immunosuppressive and anti-arthritic effects of SIN are partially attributed to the inhibition of cyclooxygenase-2 (COX-2) expression. COX-2 overexpression is associated with enhanced proliferation and angiogenesis of gastric cancer (GC). SGC-7901 cells were treated with different concentrations of SIN in order to observe its effect on the proliferation of human gastric adenocarcinoma cells and to explore the potential underlying molecular mechanism via the detection of COX-2 expression. Celecoxib was used as the positive control. Morphological alterations of the cells were observed microscopically. Cell proliferation was evaluated using MTT assay. COX-2 expression was detected using semi-quantitative RT-PCR and Western blotting. The results showed that SIN inhibited the proliferation of SGC-7901 cells in a time- and dose-dependent manner. In the presence of SIN or celecoxib, SGC-7901 cells became round and detached morphologically, indicating cell apoptosis. The expression of COX-2 was inhibited by SIN in a dose-dependent manner at both the mRNA and protein levels. Our findings indicate that the protective effects of SIN are mediated through the inhibition of COX-2 expression. These findings suggest a novel therapy to treat inflammation-mediated gastric adenocarcinomata.

Gastric cancer, Helicobacter pylori infection and other risk factors

Gastric cancer incidence is declining. However, it is too early to consider this neoplastic disease as rare and the worldwide mortality rate still remains high. Several risk factors have been identified for non-cardia gastric cancer and primary prevention is feasible since most of the risk factors can be removed. Helicobacter pylori eradication treatment reduces but does not abolish gastric cancer risk. Indeed, gastric cancer is a multifactorial disease and removing one factor does not therefore prevent all cases. Endoscopic surveillance is still needed, especially in subjects at higher risk. The definition of high-risk patients will be the future challenge as well as identifying the best surveillance strategy for such patients.

siRNA-mediated downregulation of COX-2 gene expression alters the proliferation of hepatocellular carcinoma HepG2 cells

AIM: To explore the effects of siRNA-mediated downregulation of COX-2 gene expression on the proliferation of hepatocellular carcinoma HepG2 cells.

METHODS: HepG2 cells were divided into four groups: COX-2 siRNA intervention group, control siRNA intervention group, empty liposome group and blank control group. COX-2 siRNA was transfected into HepG2 cells by lipofection. Cell proliferation inhibition was measured at 24, 48 and 72 h after transfection by MTT (thiazolyl blue) assay. The changes in cell cycle distribution were detected at 24 h after transfection by flow cytometry. The expression levels of COX-2 and ERK1/2 mRNAs and proteins were detected at 24 h after transfection by semiquantitative RT-PCR and Western blot, respectively.

RESULTS: The proliferation inhibition rate achieved in the COX-2 siRNA intervention group was higher than those in the control siRNA intervention group and empty liposome group (67.08% vs 2.45% and 1.56%, both P < 0.01). The percentage of HepG2 cells arrested at G₁ phase (DNA presynthetic phase) was increased in the COX-2 siRNA intervention group as compared to the control siRNA intervention group, empty liposome group and blank control group (72.80% vs 50.27%, 50.97% and 53.13%, all P < 0.05). Semiquantitative RT-PCR analysis showed that the expression levels of COX-2, ERK1 and ERK2 mRNAs in the COX-2 siRNA intervention group were significantly decreased as compared to the control siRNA intervention group, empty liposome group and blank control group (0.58 vs 0.83, 0.89 and 0.93; 0.32 vs 0.71, 0.64 and 0.76; 0.48 vs 0.65, 0.67 and 0.72; all P < 0.05). Similar results were obtained for protein expression as revealed by Western blot analysis.

CONCLUSION: siRNA can downregulate the expression of COX-2 gene in hepatocellular carcinoma HepG2 cells and inhibit their proliferation. COX-2 promotes the development of primary hepatic carcinoma perhaps through regulation of ERK1/2 pathway.

Molecular aspects in the diagnosis of gastric cancer

BACKGROUND

Gastric cancer (GC) represents the second most common cause of cancer-related death worldwide. The prognosis remains poor, with limited treatment options. A better understanding of the initiation and progression of GC would enable the development of general screening strategies and individualized treatment modalities.

OBJECTIVE

The assessment of tools and molecular markers for the early detection and diagnosis of GC.

METHODS

Human clinical studies published within the past 5 years are reviewed. Also, significant previous data on markers in clinical use or on relevant animal or cell culture experiments are considered.

RESULTS/CONCLUSION

Serum-based screening strategies are not ready for routine application but represent an opportunity for the identification of individuals at high risk with the need for primary gastroscopy and further surveillance, which would ultimately improve survival and prognosis of GC. Infection with Helicobacter pylori represents the principal risk factor for gastric carcinogenesis. Bacterial virulence and host genetic factors contribute to individual susceptibility. Key molecular alterations in gastric carcinogenesis are related to intra- and extracellular cascades that regulate cell proliferation, tumor invasion and metastastic spread. For the development of effective prevention and treatment modalities, it is essential to unravel the basic mechanisms of gastric carcinogenesis.

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

The over-expression of COX-2 (Cyclooxygenase 2) protein has been reported to play a key role in the incidence and development of Helicobacter pylori-associated gastric cancer. The induction of COX-2 in the gastric cancer cells with H. pylori has been demonstrated previously, but little is known about the mechanism. This study reported that the COX-2 mRNA and proteins expression level and the activity of COX-2 promoter increased remarkably with H. pylori stimulation in the MKN45 gastric cancer cells. H. pylori also stimulated phosphorylation of p38MAPK and ATF-2, which is the downstream kinase of p38MAPK. Moreover, the expression levels of COX-2 were suppressed with p38MAPK inhibitor treatment. These results suggest that H. pylori-induced activation of p38MAPK/ATF-2-mediated signal pathway is necessary for the expression of COX-2.

Construction of pGL3-Basic-COX-2-promoter reporter gene vector and detection of its function

AIM: To construct COX-2 promoter recombined luciferase reporter gene vector, and to detect its function.

METHODS: Primers were designed based on human COX-2 gene promoter, then COX-2 promoter from human genome DNA was replicated. pGL3-Basic Vector and COX-2 promoter were digested with restriction enzymes Hind Ⅲ and Bgl Ⅱ separately, then COX-2 promoter was inserted into pGL3-Basic Vector. The recombinant vector pGL3-Basic-COX-2-promoter was transiently co-transfected into MKN45 cells with control vector pRL-SV40 respectively. twelve hours later, cells were treated with H. pylori 100 times amount of cells for different length of time, then the activity of dual luciferase was detected.

RESULTS: COX-2 promoter recombined luciferase reporter gene vector was constructed successfully, and the result of sequencing and double digesting of recombined plasmid were completely correct. The experiment of transient transfection showed that the expression of COX-2 promoter in MKN45 cells was increased with time. Activity of dual-luciferase after transfection for 40 h was 3.5 folds of that for 8 h (P < 0.05). When H. pylori was added to medium for co-culture, activity of dual-luciferase was increased up markedly compared with groups that were not added with H. pylori (P < 0.05 or 0.01), and it was 5 folds after transfection for 40 h than 8 h (P < 0.01).

CONCLUSION: pGL3-Basic-COX-2-promoter can be transcribed and activated in MKN45 cells, and activity of COX-2 promoter increases obviously after H. pylori addition. pGL3-Basic-COX-2-promoter can be used to identify and detect the level of COX-2 in cells.