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) infec-tion and the development of gastric cancer. However, the exact mechanism whereby H. pylori causes gastric carcinogenesis remains unclear. It has been demon-strated that expression of cyclooxygenase-2(COX-2) is elevated in gastric carcinomas and in their precursor le-sions. 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.     

Expression of COX-2 proteins in gastric mucosal lesions

AIM: To investigate the expression of COX-2 proteins in gastric mucosal lesions and to assess the relationship between COX-2 expression and type, pathologic stage, differentiation, or lymph node metastasis in gastric cancer and the relationship between COX-2 expression and H pylori infection in gastric mucosal lesions. METHODS: Thirty patients with gastric carcinoma underwent surgical resection. Samples were taken from tumor site and paracancerous tissues, and ABC immunohistochemical staining was used to detect the expression of COX-2 proteins. H pylori was determined by rapid urea test combined with pathological stating/14C urea breath test. RESULTS: The positive rate and staining intensity of mutant COX-2 gene expression in gastric cancer were significantly higher than those in paracancerous tissues (66.7% vs 26.7%) (P<0.01, P<0.001). There was a significant correlation between COX-2 and pathologic stage or lymph node metastasis type of gastric carcinoma (76.0% vs 20.0%, 79.2% vs 16.7%) (P<0.05). No correlation was found between COX-2 expression and type or grade of differentiation (P>0.05). COX-2 expression of intestinal metaplasia (IM) or dysplasia (DYS) with positive H pylori was significantly higher than that with negative H pylori (50.6% vs 18.1%, 60.0% vs 33.3%) (P<0.05). CONCLUSION: COX-2 overexpression was found in a large proportion of gastric cancer tissues compared with matched non-cancerous tissues and was significantly associated with advanced tumor stage and lymph node metastasis. Overexpression of COX-2 plays an important role in tumor progression of gastric cancer. COX-2 may also play a role in the early development/promotion of gastric carcinoma and is associated with H pylori infection.     

Microvessel density is a prognostic marker of human gastric cancer

INTRODUCTIONGastric cancer is one of the most frequent and lethal malignancies worldwide, especially in Eastern Asia including China, and the 5-year survival rate is only about 20%[1]. A recent research has shown an increasing trend of gastric cancer mortality in China in the past 20 years, especially in rural areas and among aged people[2]. To date, the treatment outcome of this common malignancy is still not satisfactory. One major difficulty in the diagnosis and treatment of gastric c…     

Involvement of eicosanoids in the pathogenesis of pancreatic cancer: The roles of cyclooxygenase-2 and 5-lipoxygenase

The interplay between inflammation and cancer progression is a growing area of research. A combination of clinical, epidemiological, and basic science investigations indicate that there is a relationship between inflammatory changes in the pancreas and neoplastic progression. Diets high in ω-6 polyunsaturated fatty acids provide increased substrate for arachidonic acid metabolism by cyclooxygenase-2 (COX-2) and 5-lipoxygenase (5-LOX) to form eicosanoids. These eicosanoids directly contribute to pancreatic cancer cell proliferation. Both COX-2 and 5-LOX are upregulated in multiple cancer types, including pancreatic cancer. In vitro studies using pancreatic cancer cell lines have demonstrated upregulation of COX-2 and 5-LOX at both the mRNA and protein levels. When COX-2 and 5-LOX are blocked via a variety of mechanisms, cancer cell proliferation is abrogated both in vitro and in vivo. The mechanism of COX-2 has been shown to include effects on apoptosis as well as angiogenesis. 5-LOX has been implicated in apoptosis. The use of COX-2 and 5-LOX inhibitors in clinical studies in patients with pancreatic cancer has been limited. Patient enrollment has been restricted to those with advanced disease which makes evaluation of these drugs as chemopreventive agents difficult. COX-2 and 5-LOX expression have been shown to be present during the early neoplastic changes of pancreatic cancer, well before progression to invasive disease. This indicates that the ideal role for these interventions is early in the disease process as preventive agents, perhaps in patients with chronic pancreatitis or hereditary pancreatitis.     

Cyclooxygenase-2 expression is associated with well-differentiated and intestinal-type pathways in gastric carcinogenesis

BACKGROUND/AIMS: Cyclooxygenase-2 (COX-2) expression appears to be increased in several different types of human cancers, suggesting that the presence of COX-2 is associated with carcinogenesis. Recently, increased expression of COX-2 has been frequently detected in gastric cancer, and this may have prognostic significance. In the present study, we aimed to analyze the expression of COX-2 in a much larger sample to determine whether COX-2 expression is related to the clinicopathological features and survival rates of patients with gastric cancer. METHODS: We investigated 140 patients with gastric cancer who underwent surgery between January 1992 and December 1993 and examined the expression of COX-2 in human gastric cancer tissue by immunohistochemistry. RESULTS: COX-2 expression was present in the cytoplasm of tumor cells but not in normal gastric epithelia. Positive expression of COX-2 was detected in 86 of 140 gastric cancers analyzed (61.4%). Positive expression of COX-2 correlated with the depth of tumor invasion (p = 0.015). However, there was no association between COX-2 expression and tumor stage or status of lymph node or distant metastasis. Furthermore, COX-2 expression was not associated with patient survival (p = 0.816). Positive expression of COX-2 occurred more frequently in intestinal than in diffuse or mixed types of cancer and correlated with tumor differentiation (p < 0.001, p = 0.001, respectively). CONCLUSION: These results suggest that COX-2 may play an important role in the evolution of gastric carcinogenesis and be associated with well-differentiated and intestinal type pathways in gastric carcinogenesis. However, COX-2 expression seems to be less useful for establishing prognosis for gastric cancer.     

Role of microRNAs in gastric cancer

Although gastric cancer(GC)is one of the leading causes of cancer-related death,major therapeutic advances have not been made,and patients with GC still face poor outcomes.The prognosis of GC also remains poor because the molecular mechanisms of GC progression are incompletely understood.MicroRNAs(miRNAs)are noncoding RNAs that are associated with gastric carcinogenesis.Studies investigating the regulation of gene expression by miRNAs have made considerable progress in recent years,and abnormalities in miRNA expression have been shown to be associated with the occurrence and progression of GC.miRNAs contribute to gastric carcinogenesis by altering the expression of oncogenes and tumor suppressors,affecting cell proliferation,apoptosis,motility,and invasion.Moreover,a number of miRNAs have been shown to be associated with tumor type,tumor stage,and patient survival and therefore may be developed as novel diagnostic or prognostic markers.In this review,we discuss the involvement of miRNAs in GC and the mechanisms through which they regulate gene expression and biological functions.Then,we review recent research on the involvement of miRNAs in GC prognosis,their potential use in chemotherapy,and their effects on Helicobacter pylori infections in GC.A greater understanding of the roles of miRNAs in gastric carcinogenesis could provide insights into the mechanisms of tumor development and could help to identify novel therapeutic targets.     

Correlation between cyclooxygenase-2, proliferative activity,and mucin phenotype in human advanced gastric cancer

Background Recent studies have suggested that nonsteroidal anti-inflammatory drugs (NSAIDs) reduce the risk of gastrointestinal cancer, and that cyclooxygenase-2 (COX-2) may be a target enzyme for the prevention or regression of cancer by the use of NSAIDs. Mucin histochemistry has made possible a clear distinction between the differentiated characteristics of gastrointestinal epithelial cells, and the possibility that phenotypic shifts from gastric- to intestinal-type in gastric carcinoma progression has been suggested. To evaluate the role of COX-2 in gastric cancer progression, we immunohistochemically investigated COX-2 expression, and examined its relationship to proliferative activity, mucin phenotype, and clinicopathological parameters in human advanced gastric carcinomas.Methods Forty-five surgical specimens of advanced gastric carcinomas (invaded the muscularis propria or subserosa) were examined. Immunohistochemical staining was performed with monoclonal antibodies against COX-2, Ki-67, CD10 (brush border), MUC-2 (goblet-cell mucin), MUC-5AC (gastric foveolar mucin), and MUC-6 (pyloric mucin). COX-2 expression was scored by the percentage of COX-2-positive neoplastic cells, and proliferative activity was assessed by the Ki-67 labeling index at the deepest area of invasion. The mucin phenotype of the carcinomas was classified into three categories; gastric, intestinal, and unclassified.Results COX-2 staining was restricted to the cytoplasm, not only in cancer cells but also in intestinal metaplasia and some inflammatory cells and COX-2 expression in cancer cells varied greatly, but the staining in some samples was preferentially found at the invasive front. COX-2 positivity was found to correlate with Ki-67 labeling. The mean COX-2 scores were 2.29%, 2.71%, and 2.75%; and the Ki-67 labeling indices were 23.6%, 40.6%, and 56.5%, in gastric-, intestinal-, and unclassified- type carcinomas, respectively.Conclusions A close relationship between COX-2 expression and proliferative activity was confirmed in the deepest areas of advanced gastric carcinoma, and the proliferative activity increased from gastric- to intestinal- and to unclassified- type gastric carcinoma, suggesting a role for COX-2 expression and differences in biological behavior according to mucin phenotype expression during gastric cancer progression.     

Cyclooxygenase-2 expression is increased in early intestinal-type gastric cancer and gastric mucosa with intestinal metaplasia

OBJECTIVE: Cyclooxygenase-2 (COX-2) expression is increased in gastric cancer. We examined COX-2 expression in early stage gastric cancer and background mucosa to elucidate the role of COX-2 in gastric carcinogenesis. METHODS: Thirty-three early gastric cancers obtained from 30 patients infected with Helicobacter pylori were studied. Twenty-three patients had an intestinal, four patients had a diffuse, and three patients had both an intestinal and a diffuse type cancer. Expression of COX-2 protein was detected by immunohistochemistry by counting the number of positive staining cells per 100 cells. RESULTS: Mean COX-2 expression was 84.1 (SD 11.4) in 26 intestinal type cancers and was significantly higher than that in seven diffuse type cancers (23.1 +/- 9.7) (P < 0.001). In three patients who had both the intestinal and the diffuse type cancer, COX-2 expression was 92, 90 and 83 in the intestinal type cancer and only 25, 24 and 7 in the corresponding diffuse type cancer. In 18 patients who had intestinal metaplasia (15 had incomplete metaplasia), COX-2 expression was 60.2 (24.2) in the crypts with metaplasia while it was only 16.8 (10.7) in the crypts without metaplasia (P < 0.001). CONCLUSIONS: COX-2 expression may be associated with the carcinogenesis of the intestinal type gastric cancer and, speculatively, inhibition of COX-2 might have preventative effects on the intestinal type gastric cancer.     

Preferential expression of cyclooxygenase-2 in colonic-phenotype of gastric intestinal metaplasia: association with helicobacter pylori and gastric carcinoma

OBJECTIVES: Gastric intestinal metaplasia (GIM) associated with H. pylori (HP) has been considered a premalignant lesion. However, GIM phenotype associated with HP infection and gastric cancer is unclear. The expression of COX-2 in relation to GIM phenotype is also unknown. METHODS: We evaluated cellular phenotype and COX-2 expression in the GIM from HP-positive and -negative patients from Japan in the absence of gastric cancer (n = 31) by using a colon epithelium specific monoclonal antibody (mAb Das-1) and anti-COX-2 antibody. COX-2 expression was also examined in patients with gastric cancer (n = 34), both in the cancer and in the GIM areas away from the cancer field. RESULTS: Sixty-eight percent of HP-positive GIM reacted with mAb Das-1, whereas the reactivity in the HP-negative GIM was only 25% (P < 0.001). The COX-2 expression was present in 32% of HP-positive GIM and in only 9% of HP-negative GIM (P < 0.001). In the cancer group, COX-2 expression was localized both in the cancer area (94%) and in the GIM (82%) away from the cancer. Each of the COX-2-positive tissue was also positive to mAb Das-1. CONCLUSION: HP infection is highly associated with the development of colonic-phenotype of GIM, and about half of them expressed COX-2. COX-2 expression was frequent in both gastric cancer and the GIM adjacent to the cancer. The results suggest that the presence of mAb Das-1 and COX-2 reactivity in the GIM identify the subgroup of patients who may be at risk for gastric cancer and may need close surveillance.     

环氧合酶-2和血管内皮生长因子-C与胃癌淋巴管转移

目的　研究环氧合酶 2 (COX 2 )和血管内皮生长因子 (VEGF) C在胃癌组织中的表达及相关性 ,探讨二者在胃癌淋巴管生成和转移中的作用。方法　采用免疫组化方法和逆转录 PCR技术 ,分别检测了 6 4例胃癌石蜡组织中COX 2和VEGF C的表达及其中 2 2例胃癌新鲜组织中二者mRNA的表达。结果　 2 2例胃癌新鲜组织中COX 2和VEGF CmRNA表达阳性率分别为 82 %和73% ,其表达均高于相应的癌旁正常组织 (P <0 0 0 1) ,与 6 4例胃癌石蜡标本COX 2和VEGF C的表达结果较一致。且COX 2和VEGF C表达之间存在明显关联性 (P <0 0 5 )。二者在癌组织中的高表达与肿瘤浸润深度、淋巴结转移等密切相关 (P <0 0 5 )。结论　胃癌组织中有COX 2和VEGF C的高表达 ,而COX 2可能参与VEGF C淋巴管生成通路 ,它们的表达可能在胃癌淋巴管浸润和转移中发挥重要作用     

Estrogen receptors in gastric cancer:Advances and perspectives

Worldwide, gastric cancer is one of the most common malignancies with high mortality. Various aspects of thedevelopment and progression of gastric cancer continue to be extensively investigated in order to further our understanding and provide more effective means for the prevention, diagnosis, and treatment of the disease. Estrogen receptors(ERs) are steroid hormone receptors that regulate cellular activities in many physiological and pathological processes in different tissues. There are two distinct forms of ERs, namely ERα and ERβ, with several alternative-splicing isoforms for each. They show distinct tissue distribution patterns and exert different biological functions. Dysregulation of ERs has been found to be associated closely with many diseases, including cancer. A number of studies have been conducted to investigate the role of ERs in gastric cancer, the possible mechanisms underlying these roles, and the clinical relevance of deregulated ERs in gastric cancer patients. To date, inconsistent associations of different ERs with gastric cancer have been reported. These inconsistencies may be caused by variations in in vitro cell models and clinical samples, including assay conditions and protocols with regard to different forms of ERs. Given the potential of the deregulated ERs as diagnostic/prognostic markers or therapeutic targets for gastric cancer, it will be important to identify/confirm the association of each ER isoform with gastric cancer, to determine the specific roles and interactions that these individual ER isoforms play under specific conditions in the development and/or progression of gastric cancer, and to elucidate precisely these mechanisms. In this review, we summarize the achievements from early ER studies in gastric cancer to the most up-to-date discoveries, with an effort to provide a comprehensive understanding of the role of ERs roles in gastric cancer and its possible mechanisms. Furthermore, we propose directions for future investigations.     

Elevated cyclooxygenase-2 expression in patients with early gastric cancer in the gastric pylorus

Background Duodenogastric reflux after surgery increases the risk of gastric carcinoma. To determine whether bile reflux influences the development of gastric cancer in patients who have not had surgery, we compared cyclooxygenase-2 (COX-2) immunoreactivity in early gastric cancer originating from the gastric pylorus and that originating from other locations. We also examined the effects of bile acids on the expression and activity of COX-2 in gastric cells in vitro.Methods Tumor sections from 79 patients who underwent endoscopic mucosal resection for early intestinal-type gastric carcinoma were stained using a COX-2-specific monoclonal antibody. Immunoblotting of COX-2 was used to assess the effects of bile acids on COX-2 expression and activity in human gastric cell lines.Results Among the 79 early gastric cancer lesions studied, 13 (16%) arose in the gastric pylorus. In this group, COX-2 immunoreactivity was negative to weak in 38% (5 of 13 lesions) and moderate to strong in 62% (8 of 13 lesions). In the control group, COX-2 immunoreactivity was negative to weak in 70% (46 of 66 lesions) and moderate to strong in 30% (20 of 66 lesions). COX-2 expression was significantly elevated in early gastric cancer located in the gastric pylorus, compared with that in the other locations. In human gastric cell lines, bile acids induced COX-2 expression, mediated by the ERK 1/2 mitogen-activated protein kinase pathway.Conclusions COX-2 expression is elevated in early gastric cancer of the gastric pylorus, a common site of gastric cancer. Bile acids induced COX-2 expression in human gastric cell lines, suggesting a role of bile reflux in gastric carcinogenesis.     

A review of the genomics of gastric cancer.

Gastric cancer is the fourth most common cancer and the second leading cause of cancer-related death in the world. Over the past 2 decades, many exciting discoveries regarding the genomics of gastric cancer have been made. There are 2 distinct histologic types of gastric adenocarcinoma, and these types differ in their epidemiology, pathogenesis, genetic profile, and clinical outcome. The development of new approaches to functional genomics has significantly improved our ability to explore molecular alterations underlying gastric carcinogenesis and progression. The pathogenesis of intestinal-type gastric cancer follows a multistep progression that usually is initiated by H pylori infection. A wide range of genetic and epigenetic abnormalities including point mutation, loss of heterozygosity, microsatellite instability, and hypermethylation are described in intestinal-type gastric cancer and its precursor lesions. In contrast to the intestinal-type, diffuse-type gastric cancer is defined by a lack of precursor lesions; mutation or epigenetic silencing of the E-cadherin gene appears to be the key carcinogenic event. An improved understanding of the genomics of gastric cancer should lead to the rapid development of novel diagnostic techniques and molecular-based treatment strategies.     

microRNA-101和环氧合酶-2在胃癌中的表达及其临床意义

背景：microRNAs是一类对靶基因表达具有转录后调控作用的非编码小RNA。microRNA-101（miR-101）在多种恶性肿瘤中呈低表达,而过表达外源性miR-101可发挥肿瘤抑制作用。前期体内、外实验发现外源性miR-101可抑制胃癌细胞增殖和环氧合酶-2（COX-2）表达。目的：检测胃癌组织中的miR-101、COX-2表达并探讨其临床意义。方法：收集手术切除胃癌组织和配对癌旁非癌组织标本30例,以实时荧光定量RT—PCR检测miR-101、COX-2mRNA表达,分析两者间以及两者与胃癌主要临床病理特征的关系。结果：绝大多数胃癌组织中miR-101表达低下,COX-2mRNA则呈过表达。胃癌组织与癌旁非癌组织间miR-101、COX-2mRNA表达量差异显著（P〈0．01）,且两者表达在癌组织和癌旁组织中均呈负相关（癌组织：r=-0．767,P=0．000;癌旁组织：r=-0．718,P=0．000）。TNMⅢ、IV期胃癌和伴淋巴结转移的胃癌中,miR-101表达分别显著低于TNMI、Ⅱ期病例和无淋巴结转移病例（P〈0．05）,COX-2mRNA表达分别显著高于TNMI、Ⅱ期病例和无淋巴结转移病例（P〈0．05）。结论：miR-101与COX-2之间的负相关性可能有助于胃癌的临床诊断;miR-101表达低下伴COX-2过表达与胃癌临床进展和转移有关,对预后判断有一定参考价值。     

环氧合酶-2与癌症治疗引起的消化道黏膜炎

消化道黏膜炎是癌症治疗的主要并发症之一，可继发于放疗、化疗或两者综合治疗后。研究显示环氧合酶-2（COX-2）在消化道黏膜炎的发生、发展过程中起非常重要的作用,COX-2抑制剂则能通过抑制COX-2而减轻消化道黏膜炎，有望成为一种新的黏膜炎预防和治疗药物。本文就癌症治疗引起的消化道黏膜炎的定义和发生机制、COX-2在消化道黏膜炎中的作用以及COX-2抑制剂的疗效作一综述。     

环氧化酶-2在胃癌和胃炎中的表达及其与幽门螺杆菌感染的关系

目的探讨环氧化酶-2(COX-2)在胃癌和胃炎中的表达及其与幽门螺杆菌(Helicobater pylori,HP)感染的关系,为胃癌的预防和治疗提供有价值的实验和理论依据。方法2004年11月至2005年4月中国医科大学附属第一医院门诊胃镜活检标本共128例,采用免疫组化技术检测COX-2在胃癌以及各型胃炎中的表达情况。结果胃癌和萎缩性胃炎伴不典型增生组织中COX-2的表达率明显高于浅表性胃炎(P<0.05),COX-2在萎缩性胃炎伴不典型增生HP感染阳性患者中的表达率明显高于HP感染阴性患者(P<0.05),高、中分化胃癌COX-2表达率高于低分化胃癌(P<0.05)。结论COX-2在胃癌组织中存在过表达,HP感染可使萎缩性胃炎伴不典型增生组织中COX-2表达增强,COX-2表达与胃癌分化程度有关。