Helicobacter pylori infection generated gastric cancer through p53-Rb tumor-suppressor system mutation and telomerase reactivation

Prognosis and survival study in patients with gastric adenocarcinoma and its relationship with pRb expression alteration: A retrospective IHC-based study

Background and Objective

Among cancers, gastric cancer has the fifth highest incidence worldwide and is the third most common mortality factor, which may have been due to inadequate knowledge of its molecular pathogenesis. The retinoblastoma gene (RB1), a tumor suppressor gene, may have a role in gastric cancer. This research aims to assess Rb expression as a prognostic marker to obtain more insight regarding gastric cancer.

Methods

This retrospective analytical study was done on 61 patients (45 males and 16 females) with gastric adenocarcinoma admitted from 2010 to 2012 in Shahid Sadoughi and Mortaz hospitals, Yazd, Iran. Demographic data, including age, gender, clinical signs and symptoms, and pathology reports, were retrieved from patients' hospital folders. Then, the altered Retinoblastoma gene expression was evaluated by immunohistochemistry studies. Acquired data were analyzed by SPSS software v.16. p < 0.05 was statistically considered meaningful.

Results

In this study, the ratio of men to women was higher (2.81:1), and the mean age of patients was 62.44 years. About 90.2% of patients died during the study. There was no meaningful relationship between the presence of pRb, the intensity of staining, the percentage of staining with patients' age, gender, tumor grading, and survival rate (p > 0.05). There was only a meaningful relationship between the grade of tumors and survival rate (p = 0.039).

Conclusion

Altered pRB expression is not common in gastric cancer and does not impact the survival and grading of tumors. Poorly differentiated tumors had an ominous outcome with the lowest survival time.

Stomach-specific c-Myc overexpression drives gastric adenoma in mice through AKT/mammalian target of rapamycin signaling

Gastric cancer (GC) is one of the most common malignant cancers in the world. c-Myc, a well-known oncogene, is commonly amplified in many cancers, including gastric cancer. However, it is still not completely understood how c-Myc functions in GC. Here, we generated a stomach-specific c-Myc transgenic mouse model to investigate its role in GC. We found that overexpression of c-Myc in Atp4b+ gastric parietal cells could induce gastric adenoma in mice. Mechanistically, c-Myc promoted tumorigenesis via the AKT/mTOR pathway. Furthermore, AKT inhibitor (MK-2206) or mTOR inhibitor (Rapamycin) inhibited the proliferation of c-Myc overexpressing gastric cancer cell lines. Thus, our findings highlight that gastric tumorigenesis can be induced by c-Myc overexpression through activation of the AKT/mTOR pathway.

The Role and Clinical Implications of the Retinoblastoma (RB)-E2F Pathway in Gastric Cancer

Gastric cancer is the most common malignant tumor in the digestive tract, with very high morbidity and mortality in developing countries. The pathogenesis of gastric cancer is a complex biological process mediated by abnormal regulation of proto-oncogenes and tumor suppressor genes. Although there have been some in-depth studies on gastric cancer at the molecular level, the specific mechanism has not been fully elucidated. RB family proteins (including RB, p130, and p107) are involved in cell cycle regulation, a process that largely depends on members of the E2F gene family that encode transcriptional activators and repressors. In gastric cancer, inactivation of the RB-E2F pathway serves as a core transcriptional mechanism that drives cell cycle progression, and is regulated by cyclins, cyclin-dependent kinases, cyclin-dependent kinase inhibitors, p53, Helicobacter pylori and some other upstream molecules. The E2F proteins are encoded by eight genes (i.e. E2F1 to E2F8), each of which may play a specific role in gastric cancer. Interestingly, a single E2F such as E2F1 can activate or repress transcription, and enhance or inhibit cell proliferation, depending on the cell environment. Thus, the function of the E2F transcription factor family is very complex and needs further exploration. Importantly, the presence of H. pylori in stomach mucosa may affect the RB and p53 tumor suppressor systems, thereby promoting the occurrence of gastric cancer. This review aims to summarize recent research progress on important roles of the complex RB-E2F signaling network in the development and effective treatment of gastric cancer.

Predictive Effect of Helicobacter pylori in Gastric Carcinoma Development: Systematic Review and Quantitative Evidence Synthesis

Helicobacter pylori (H. pylori) is a bacterial pathogen implicated in gastritis, gastric ulceration, and gastric carcinoma. This study aimed to synthesize literature in providing evidence on the causative role of H. pylori in gastric carcinoma development. This study is based on assessing public literature using an applied meta-analysis, namely, quantitative evidence synthesis (QES). The analytic procedure uses DerSimonian-Laird, including assessing heterogeneity. The QES also utilizes meta-regression and the environmental effect associated with H. pylori in gastric cancer development. Eighteen studies are included in the QES. There is increased prevalence of H. pylori exposure among the cases. The heterogeneity between the CES and individual effect sizes is also significant. Despite controlling for the confoundings, there is increased exposure to H. pylori among the gastric cancer cases, regardless of the differences in the geographic location. H. pylori in this synthesized literature illustrates the contributory role of this microbe in gastric carcinoma. Additionally, regardless of geographic locale, namely, South Korea or Spain, H. pylori is implicated in gastric cancer development.

Association of p53 Gene Mutation With Helicobacter pylori Infection in Gastric Cancer Patients and Its Correlation With Clinicopathological and Environmental Factors

BACKGROUND

Gastric cancer is also a leading cancer in Bangladesh like that of the global incidences. It is speculated that environmental, bacterial infection and molecular factors might have been carrying the key role of rising trend of the disease. This study was aimed to investigate the association of mutated p53 gene with of Helicobacter pylori (H. pylori) infection, clinicopathological and some environmental factors of the gastric cancer patients.

METHODS

This cross-sectional study was carried out from January 2015 to December 2016 in a specialized cancer hospital of Bangladesh. Patients were selected randomly who were admitted for surgical intervention after diagnosis as adenocarcinoma of the stomach and physically fit for surgery. After admission proper evaluation of the patients was done. Tissue sample from the gastrectomy specimen along with the blood sample was sent to the related laboratories. After DNA extraction for p53, exons 5 and 6, they were adjusted for proper primer designing. Appropriate sequencing analysis of the result was done. Status of p53 was investigated to see their association with the result of the H. pylori, age and sex, tumor status, smoking and extra salt intake of the patients. Result of the study was calculated and analyzed by Chi-square and binomial logistic regression to find the association amongst them.

RESULTS

Among the 71 patients, mean age was 52.96 years old, male: female ratio were 48:23, age group above 41 years were 53 (74.6%), proliferative and ulceroproliferative group of the tumor dominated (87.3%). There were 52 cases with (73.2%) p53 mutation. Among the 51 H. pylori positive cases, 41 (80%) had p53 mutation (P = 0.033). Tumor size and lymph node status were found to be associated with the gene mutation (P = 0.05). Age also had strong correlation with the mutation (P = 0.015). Gene mutation was found mostly among the younger (≤ 40 years) group of patients (94.4%). Patient with extra salt intake was also found related with the mutation (P = 0.03).

CONCLUSIONS

Environmental and genetic factors seem to be risk factors for gastric cancer in Bangladesh. Nationwide anti H. pylori drive and further molecular research could elicit the other risk factors which might help to reduce the gastric cancer incidences in the country after taking appropriate measures.

MET4 expression predicts poor prognosis of gastric cancers with Helicobacter pylori infection

The role of HGF/SF‐MET signaling is important in cancer progression, but its relation with Helicobacter pylori‐positive gastric cancers remains to be elucidated. In total, 201 patients with primary gastric carcinoma who underwent curative or debulking resection without preoperative chemotherapy were studied. MET4 and anti‐HGF/SF mAbs were used for immunohistochemical analysis. Survival of gastric cancer patients was estimated by Kaplan–Meier method and compared with log‐rank. Cox proportional hazards models were fit to determine the independent association of MET‐staining status with outcome. The effect of live H. pylori bacteria on cell signaling and biological behaviors was evaluated using gastric cancer cell lines. MET4‐positive gastric cancers showed poorer prognosis than MET4‐negative cases (overall survival, P = 0.02; relapse‐free survival, P = 0.06). Positive staining for MET4 was also a statistically significant factor to predict poor prognosis in H. pylori‐positive cases (overall survival, P < 0.01; relapse‐free survival, P = 0.01) but not in H. pylori‐negative cases. Gastric cancers positively stained with both HGF/SF and MET4 showed a tendency of the worst prognosis. Stimulation of MET‐positive gastric cancer cells with live H. pylori bacteria directly upregulated MET phosphorylation and activated MET downstream signals such as p44/42MAPK and Akt, conferring cell proliferation and anti‐apoptotic activity. In conclusion, positive staining for MET4 was useful for predicting poor prognosis of gastric cancers with H. pylori infection. Helicobacter pylori stimulated MET‐positive gastric cancers and activated downstream signaling, thereby promoting cancer proliferation and anti‐apoptotic activity. These results support the importance of H. pylori elimination from gastric epithelial surface in clinical therapy.

Genetic and molecular aspects of Helicobacter pylori in gastritis, pre- cancerous conditions and gastric adenocrcinoma

Gastric adenocarcinoma is one of the most common malignancies worldwide. Many ethological causes have been introduced among which helicobacter pylori, as a gram-negative bacterium has been considered as an important pathological facilitating factor. This agent is also associated with different digestive diseases, such as gastritis, peptic ulcer, and mucosa-associated lymphoid tissue lymphoma. Recently, scientists have been described some molecular aspects that show the role of some apoptotic genes and proteins; for example: P53, Bcl2, C-Myc and Rb-suppressor systems in the H. pylori pathogenesis. Also the relationship between nitric oxide (NOSi genotype) with H. pylori infection has been shown. The aim of this mini-review is to explain better these genetically aspects of H.pylori pathogenesis.

MSI/LOH and extron expression of the FHIT gene in gastric carcinoma

We detected loss of heterozygosity (LOH) and microsatellite instabilities (MSI), as well as extron expression of the fragile histidine triad (FHIT) gene in gastric carcinoma (GC), in order to evaluate their association with clinicopathological processes in gastric carcinogenesis. LOH and MSI of the FHIT were detected by using PCR at 4 microsatellite loci: D3S 1300, D3S 4103, D3S 1481, D3S 1234 in cancer tissues from 50 patients with primary GC, with normal mucosa acting as matched controls. FHIT transcripts were detected by nested RT-PCR in 30 cases of GC and their products were sequenced. Results show that the average frequencies of LOH and MSI of the FHIT gene in GC were 32.4% and 26.4%, respectively. There was no correlation between LOH and MSI of the FHIT gene in GC and the histological characteristics of gastric carcinoma (Bormann's or Lauren's classification). LOH of the FHIT gene in GC was related to depth invasiveness, and its frequency in GC where serosa was penetrated was significantly higher than that in GC without serosa penetration (73.5% vs 37.5%, P < 0.05). The frequency of MSI in GC without lymph node metastasis was significantly higher than that in GC with lymph node metastasis (66.7% vs 34.3%, P < 0.05). Aberrant transcripts were found in 11/30 GC tissues. Sequencing analysis of the aberrant fragments found a RT-PCR product missing exons 5-7 in one case of GC, and another product missing exons 4-7. Four of 10 (40.0%) cases of primary GC showed absent or decreased expression of the FHIT protein as compared to their matched normal tissues. The findings in this study suggest that LOH and MSI of FHIT gene may induce aberrant extron expression, which might play a role in gastric carcinogenesis.

Helicobacter pylori infection and light chain gammopathy

Objective. Helicobacter pylori provokes a host of immune alterations upon colonizing the gastric mucosa. Design. We report 22 individuals with confirmed Helicobacter pylori infection who were also managed for the concurrent elevation of immunoglobulin free light chain (kappa and lambda) levels. Result. Of the 22 patients, 15 patients (68.2%) had elevated free light chain levels: 6 patients (40%) had only kappa chain elevation, 2 patients (13.3%) had only lambda chain elevation, and 7 patients (46.7%) had both kappa and lambda chain elevation. Twenty out of the 22 patients (90.9%) were microbiologically confirmed cured with 3 patients being lost to follow-up for repeat levels. Of the 3 patients who were lost to follow-up, 1 patient had only kappa chain elevation, 1 patient had only lambda chain elevation, and 1 patient had both kappa and lambda chain elevation. For those who were cured (19 patients), 5 patients with kappa elevation had normalized values, 4 patients with lambda elevation had normalized values, and 2 patients with combined kappa and lambda elevation had normalized values. For 6 out of the 19 patients, the light chain levels remained elevated. Conclusion. We speculate that the Helicobacter pylori infection disrupts the immunoglobulin system with potential implications being discussed below.

Clinicopathological correlation and prognostic significance of protein kinase cα overexpression in human gastric carcinoma

OBJECTIVES

This study investigated the PKCα protein expression in gastric carcinoma, and correlated it with clinicopathological parameters. The prognostic significance of PKCα protein expression in gastric carcinoma was analyzed.

METHODS

Quantitative real-time PCR test was applied to compare the PKCα mRNA expression in tumorous and nontumorous tissues of gastric carcinoma in ten randomly selected cases. Then PKCα protein expression was evaluated in 215 cases of gastric carcinoma using immunohistochemical method. The immunoreactivity was scored semiquantitatively as: 0 = absent; 1 = weak; 2 = moderate; and 3 = strong. All cases were further classified into two groups, namely PKCα overexpression group with score 2 or 3, and non-overexpression group with score 0 or 1. The PKCα protein expression was correlated with clinicopathological parameters. Survival analysis was performed to determine the prognostic significance of PKCα protein expression in patients with gastric carcinoma.

RESULTS

PKCα mRNA expression was upregulated in all ten cases of gastric carcinoma via quantitative real-time PCR test. In immunohistochemical study, eighty-eight out of 215 cases (41%) of gastric carcinoma revealed PKCα protein overexpression, which was statistically correlated with age (P = 0.0073), histologic type (P<0.0001), tumor differentiation (P = 0.0110), depth of invasion (P = 0.0003), angiolymphatic invasion (P = 0.0373), pathologic stage (P = 0.0047), and distant metastasis (P = 0.0048). We found no significant difference in overall and disease free survival rates between PKCα overexpression and non-overexpression groups (P = 0.0680 and 0.0587). However, PKCα protein overexpression emerged as a significant independent prognostic factor in multivariate Cox regression analysis (hazard ratio 0.632, P = 0.0415).

CONCLUSIONS

PKCα protein is upregulated in gastric carcinoma. PKCα protein expression is statistically correlated with age, histologic type, tumor differentiation, depth of invasion, angiolymphatic invasion, pathologic stage, and distant metastasis. The PKCα protein overexpression in patients with gastric carcinoma is a significant independent prognostic factor in multivariate Cox regression analysis.

hTERT, MYC and TP53 deregulation in gastric preneoplastic lesions

Background

Gastric cancer is a serious public health problem in Northern Brazil and in the world due to its high incidence and mortality. Despite the severity of the disease, more research is needed to better understand the molecular events involved in this intestinal-type gastric carcinogenesis process. Since precancerous lesions precede intestinal-type gastric cancer, here, we evaluated the hTERT, MYC, and TP53 mRNA and protein expression, as well as TP33 copy number, in gastric preneoplastic lesions.

Methods

We evaluated 19 superficial gastritis, 18 atrophic gastritis, and 18 intestinal metaplasia from cancer-free individuals of Northern Brazil. Quantitative reverse transcription PCR was used to analyze the mRNA expression and immunohistochemical methods were used to assess protein immunoreactivity in tissue samples. The number of TP53 gene copies was investigated in gastric diseases by quantitative PCR.

Results

We observed hTERT, MYC, and p53 immunoreactivity only in intestinal metaplasia samples. The immunoreactivity of these proteins was strongly associated with each other. A significantly higher MYC mRNA expression was observed in intestinal metaplasia compared to gastritis samples. Loss of TP53 was also only detected in intestinal metaplasia specimens.

Conclusions

We demonstrated that hTERT, MYC, and TP53 are deregulated in intestinal metaplasia of individuals from Northern Brazil and these alterations may facilitate tumor initiation.

The impact of C-MYC gene expression on gastric cancer cell

The upregulation or mutation of C-MYC has been observed in gastric, colon, breast, and lung tumors and in Burkitt's lymphoma. However, little is known about the role C-MYC plays in gastric adenocarcinoma. In the present study, we intended to investigate the influence of C-MYC on the growth, proliferation, apoptosis, invasion, and cell cycle of the gastric cancer cell line SGC7901 and the gastric cell line HFE145. C-MYC cDNA was subcloned into a constitutive vector PCDNA3.1 followed by transfection in normal gastric cell line HFE145 by using liposome. Then stable transfectants were selected and appraised. Specific inhibition of C-MYC was achieved using a vector-based siRNA system which was transfected in gastric cancer cell line SGC7901. The apoptosis and cell cycles of these clones were analyzed by using flow cytometric assay. The growth and proliferation were analyzed by cell growth curves and colony-forming assay, respectively. The invasion of these clones was analyzed by using cell migration assay. The C-MYC stable expression clones (HFE-Myc) and C-MYC RNAi cells (SGC-MR) were detected and compared with their control groups, respectively. HFE-Myc grew faster than HFE145 and HFE-PC (HFE145 transfected with PCDNA3.1 vector). SGC-MR1, 2 grew slower than SGC7901 and SGC-MS1, 2 (SGC7901 transfected with scrambled control duplexes). The cell counts of HFE-Myc in the third, fourth, fifth, sixth, and seventh days were significantly more than those of control groups (P < 0.05). Those of SGC-MR1, 2 in the fourth, fifth, sixth, and seventh days were significantly fewer than those of control groups (P < 0.05). Cell cycle analysis showed that proportions of HFE-Myc and SGC-MR cells in G0-G1 and G2-M were different significantly with their control groups, respectively (P < 0.05). The apoptosis rate of HFE-Myc was significantly higher than those of control groups (P < 0.05). Results of colony-forming assay showed that the colony formation rate of HFE-Myc was higher than those of control groups; otherwise, the rate of SGC-MR was lower than those of their control groups (P < 0.05). The results of cell migration assay showed that there were no significant differences between experimental groups and control groups (P > 0.05). In conclusion, C-MYC can promote the growth and proliferation of normal gastric cells, and knockdown of C-MYC can restrain the growth and proliferation of gastric cancer cells. It can induce cell apoptosis and help tumor cell maintain malignant phenotype. But it can have not a detectable influence on the ability of invasion of gastric cancer cells.

Genetic polymorphisms in DNA repair genes XPC, XPD, and XRCC4, and susceptibility to Helicobacter pylori infection-related gastric antrum adenocarcinoma in Guangxi population, China

Genetic polymorphisms in DNA repair genes may influence individual variation in DNA repair capacity, which may be associated with risk of gastric antrum adenocarcinoma (GAA) related to Helicobacter pylori infection. This study, including 361 GAAs and 616 controls without any evidence of tumors, was designed to evaluate the association between the polymorphisms of DNA repair genes XPC Ala499Val (RS#2228000) and Lys939Gln (RS#2228001), XPD Lys751Gln (RS#13181), and XRCC4 Ala247Ser (RS#3734091) and Ser298Asn (RS#1805377), and GAA risk for Guangxi population by means of TaqMan-PCR analysis. Increased risks of GAA were found for individuals with H. pylori positive [odds ratio (OR), 2.48; 95% confidence interval (CI), 1.84-3.33] or cagA positive (OR, 7.34; 95% CI, 5.46-9.87). No differences were observed among the studied groups with regard to the genotype distribution of XPC codons 499 and 939 and of XRCC4 codon 247; but XPD codon 751 genotypes with Gln [ORs (95% CI) were 2.67 (1.98-3.58) and 3.97 (2.64-5.99) for Lys/Gln and Gln/Gln, respectively] and XRCC4 codon 298 genotypes with Asn [ORs (95% CI) were 3.01 (2.21-4.10) and 4.78 (3.24-7.05) for Ser/Asn and Asn/Asn, respectively] increased the risk of GAA. Interestingly, there was an interactive effect between the risk genotypes of these two genes and cagA-positive status in the GAA risk (OR(interact) = 2.05 and 2.08, respectively). However, we did not find the gene-H. pylori-status interaction effects on the risk of GAA (P(interact) > 0.05). The results suggested that the polymorphisms of XPD codon 751 and XRCC4 codon 298 are associated with an increased risk of developing H. pylori-related GAA among Guangxi population.

Gastric adenocarcinoma and Helicobacter pylori: correlation with p53 mutation and p27 immunoexpression

INTRODUCTION

Helicobacter pylori infection is an established risk factor for gastric cancer development, but the exact underlying mechanism still remains obscure. The inactivation of tumor suppressor genes such as p53 and p27(KIP1) is a hypothesized mechanism, although there is no consensus regarding the influence of H. pylori cagA(+) in the development of these genetic alterations.

GOALS

To verify the relationship among H. pylori infection, p53 mutations and p27(Kip1) Protein (p27) expression in gastric adenocarcinomas (GA) seventy-four tissues were assayed by PCR for H. pylori and cagA presence. Mutational analysis of p53 gene was performed by single-strand conformation polymorphism (SSCP). Seventy tissues were analyzed by an immunohistochemical method for p27 expression.

RESULTS

From the samples examined, 95% (70/74) were H. pylori positive, 63% cagA(+). Altered p53 electrophoretic mobility was found in 72% of cases and significantly more frequent in the presence of cagA. Considerable reduction in p27 expression (19%) was found with a tendency for association between cagA(+) and p27(-), although the results were not statistically significant. Concomitant alterations of both suppressor genes were detected in 60% of cases. In the cases cagA(+), 66.7% of them had these concomitant alterations.

CONCLUSIONS

The data suggest that H. pylori cagA(+) contributes to p53 alteration and indicate that concomitant gene inactivation, with reduced p27 expression, may be a mechanism in which H. pylori can promote the development and progression of gastric cancer.

p53 inhibition of AP1-dependent TFF2 expression induces apoptosis and inhibits cell migration in gastric cancer cells

Overexpression of trefoil factor 2 (TFF2) is associated with increased cell migration, resistance to apoptosis, and possibly increased gastric cancer invasion. Dysregulation of p53 is frequently observed in preneoplastic conditions of the stomach. Here, we investigated the effect of p53 on the expression and function of TFF2 in gastric cancer cell lines. Gene expression was determined by reverse transcription-polymerase chain reaction, and promoter activity was assessed by dual luciferase reporter assays. Apoptosis was detected by flow cytometry, and cell migration was evaluated by the Boyden chamber assay. Exogenous expression of p53 dose dependently inhibited endogenous TFF2 mRNA, protein, and promoter activity and resulted in induction of cell apoptosis and inhibition of cell migration. Downregulation of TFF2 by small interfering RNA sensitized gastric cancer cells to drug-induced p53-dependent apoptosis. Addition of human TFF2 peptide reversed p53-dependent apoptosis and inhibition of cell migration. The p53-responsive element was mapped to an AP-1-like cis-element at -182 bp upstream of the TFF2 transcription start site. Mutation of this AP-1-like element abrogated p53-mediated inhibition of TFF2 promoter activity. Gel shift and chromatin immunoprecipitation assays demonstrated that c-Jun and c-Fos bind to this AP-1-like element. Ectopic expression of c-Jun/c-Fos or p300 or treatment of cells with phorbol 12-myristate 13-acetate (PMA) stimulated endogenous TFF2 mRNA expression and promoter activity, and p53 inhibited the effects of AP-1 and PMA on TFF2. p53 induces cell apoptosis and inhibits cell migration in part by downregulating TFF2 expression through an AP-1-like site, suggesting that TFF2 may be an important downstream target of p53.

Intestinal metaplasia: a premalignant lesion involved in gastric carcinogenesis

Despite a plateau in incidence, gastric cancer remains a significant problem globally. The majority of gastric cancer is associated with histologically recognizable premalignant stages as first described by Pelayo Correa in the mid-1970s. The mortality from gastric cancer remains high especially in Western countries where, arguably, the index of suspicion of gastric cancer in patients presenting with upper abdominal symptoms is lower than in high prevalence countries. What is the evidence that intestinal metaplasia (IM) is a premalignant condition? What should the clinician know about IM and the relative risks of progression to gastric cancer? Finally, what are the current and future strategies that may help stratify patients into high risk and low risk for the development of gastric cancer? This review focuses on gastric IM and outlines some of the literature that discusses it as a premalignant condition. It also reviews the issue of surveillance of patients with IM in order to attempt to reduce the significant mortality of gastric cancer by detection of earlier stages of disease which are eminently treatable.

MYC and gastric adenocarcinoma carcinogenesis

MYC is an oncogene involved in cell cycle regulation, cell growth arrest, cell adhesion, metabolism, ribosome biogenesis, protein synthesis, and mitochondrial function. It has been described as a key element of several carcinogenesis processes in humans. Many studies have shown an association between MYC deregulation and gastric cancer. MYC deregulation is also seen in gastric preneoplastic lesions and thus it may have a role in early gastric carcinogenesis. Several studies have suggested that amplification is the main mechanism of MYC deregulation in gastric cancer. In the present review, we focus on the deregulation of the MYC oncogene in gastric adenocarcinoma carcinogenesis, including its association with Helicobacter pylori (H pylori) and clinical applications.

Gastric epithelial dysplasia: the Western perspective

The need for early diagnosis of gastric cancer is emphasized by the fact that gastric cancer remains the second most common cause of cancer related deaths worldwide. The aggressive surveillance and definite therapy for low and high-grade dysplasia, which can be achieved endoscopic means, remains the cornerstone of clinical management. Although the precursor status of dysplasia is not contested, its classification is controversial and fraught with marked inter-observer variations. Most cases of gastric dysplasia have an "intestinal" phenotype referred to as adenomatous dysplasia. Hyperplastic (type II dysplasia) is another less common variant. The progression of dysplasia to carcinoma is paralleled by a stepwise accumulation of multiple, but yet uncertain, genetic abnormalities. There are no immunohistochemical or molecular assays that can stratify with certainty the risk of progression to cancer. Given the low rate of transformation of low-grade dysplasia, annual endoscopic surveillance with re-biopsy is advocated. A diagnosis of indefinite for dysplasia should also prompt endoscopic surveillance. A diagnosis of high-grade dysplasia is more ominous, since it progress to cancer in most cases. However, the novel imaging and endoscopic modalities have modified management strategies with mucosal lesions amenable to endoscopic resection, while surgical resection is reserved to invasive adenocarcinoma with submucosal invasion.

Gastric preneoplastic lesions and epithelial dysplasia

The incidence of gastric cancer is declining; however, it remains the second most common cause of cancer-related deaths worldwide. This article describes gastric preneoplastic lesions and epithelial dysplasia. The possible role of Helicobacter pylori infection is emphasized.

Helicobacter pylori eradication to prevent gastric cancer: Underlying molecular and cellular mechanisms

Numerous cellular and molecular events have been described in development of gastric cancer. In this article, we overviewed roles of Helicobacter pylori (H pylori) infection on some of the important events in gastric carcinogenesis and discussed whether these cellular and molecular events are reversible after cure of the infection. There are several bacterial components affecting gastric epithelial kinetics and promotion of gastric carcinogenesis. The bacterium also increases risks of genetic instability and mutations due to NO and other reactive oxygen species. Epigenetic silencing of tumor suppressor genes such as RUNX3 may alter the frequency of phenotype change of gastric glands to those with intestinal metaplasia. Host factors such as increased expression of growth factors, cytokines and COX-2 have been also reported in non-cancerous tissue in H pylori-positive subjects. It is noteworthy that most of the above phenomena are reversed after the cure of the infection. However, some of them including overexpression of COX-2 continue to exist and may increase risks for carcinogenesis in metaplastic or dysplastic mucosa even after successful H pylori eradication. Thus, H pylori eradication may not completely abolish the risk for gastric carcinogenesis. Efficiency of the cure of the infection in suppressing gastric cancer depends on the timing and the target population, and warrant further investigation.

Genetic alterations in benign lesions: Chronic gastritis and gastric ulcer

AIM: To investigate the occurrence of chromosome 3, 7, 8, 9, and 17 aneuploidies, TP53 gene deletion and p53 protein expression in chronic gastritis, atrophic gastritis and gastric ulcer, and their association with H pylori infection.

METHODS: Gastric biopsies from normal mucosa (NM, n = 10), chronic gastritis (CG, n = 38), atrophic gastritis (CAG, n=13) and gastric ulcer (GU, n = 21) were studied using fluorescence in situ hybridization (FISH) and immunohistochemical assay. A modified Giemsa staining technique and PCR were used to detect H pylori. An association of the gastric pathologies and aneuploidies with H pylori infection was assessed.

RESULTS: Aneuploidies were increasingly found from CG (21%) to CAG (31%) and to GU (62%), involving mainly monosomy and trisomy 7, trisomies 7 and 8, and trisomies 7, 8 and 17, respectively. A significant association was found between H pylori infection and aneuploidies in CAG (P = 0.0143) and GU (P = 0.0498). No TP53 deletion was found in these gastric lesions, but p53-positive immunoreactivity was detected in 45% (5/11) and 12% (2/17) of CG and GU cases, respectively. However, there was no significant association between p53 expression and H pylori infection.

CONCLUSION: The occurrence of aneuploidies in benign lesions evidences chromosomal instability in early stages of gastric carcinogenesis associated with H pylori infection, which may confer proliferative advantage. The increase of p53 protein expression in CG and GU may be due to overproduction of the wild-type protein related to an inflammatory response in mucosa.

Telomerase activity in proximal and distal gastric neoplastic and preneoplastic lesions using immunohistochemical detection of hTERT

BACKGROUND

The incidence of distal (corpus and antrum) gastric adenocarcinoma is decreasing with a simultaneous increase in incidence of proximal (cardia) adenocarcinoma. Epidemiological studies suggest that they may represent different diseases but corroborative molecular data are scarce. Intestinal metaplasia may have a lower malignant potential in the proximal stomach but regardless of the locations, its specificity as a predictor of carcinoma is low.

AIMS

The aim of this study was to establish whether human telomerase reverse transcriptase expression differs at various points in proximal versus distal gastric carcinogenesis and to test the utility of human telomerase reverse transcriptase expression as a marker of cancer risk in intestinal metaplasia.

MATERIAL AND METHODS

Wax-embedded tissue from proximal and distal stomach including normal mucosa (n=86), intestinal metaplasia (n=83) and carcinoma (n=101) were used and slides were immunostained for human telomerase reverse transcriptase and pRb and scored semi-quantitatively.

RESULTS

The results showed that in both proximal and distal stomach, human telomerase reverse transcriptase expression rates increased from normal mucosa to cancer. High rates of human telomerase reverse transcriptase expression were seen in the proliferative zones of glands in intestinal metaplasia. In both the locations, loss of pRb expression correlated with higher human telomerase reverse transcriptase expression.

CONCLUSIONS

In conclusion, telomerase activity appears to be an early event in both proximal and distal gastric carcinogenesis and human telomerase reverse transcriptase is expressed in intestinal metaplasia. Telomerase re-expression may be facilitated by pRb inactivation.

Expression of human telomerase reverse transcriptase gene in hepatocellular carcinoma and effect of antisense telomerase gene on apoptosis of hepatocellular cancer cell line HepG2

AIM: To examine the expression of human telomerase reverse transcriptase (hTERT) gene in human hepatocellular cancer (HCC), to investigate its relevance with the carcinogenesis, development and recurrence of HCC, and to explore the potential of antisense RNA of human telemerase (hTR) gene in the treatment of HCC.

METHODS: Immunohistochemistry was used to detect the expression of hTERT protein in 42 specimens of HCC. The relationship between hTERT expression and the clinical and pathological characteristics was analyzed. HepG2 cell line was transfected with antisense hTR expression vector (pBBS-hTR) with lipofectin. The transfected cells were cultured in vitro and then inoculated into nude mice. The cell cycle, ultrastructure and tumorigenicity of the transfected cells were examined.

RESULTS: The positive rate of hTERT gene expression in HCC was significantly higher (30/42) than that in normal liver tissues (71.4% vs 0%, P < 0.01), and the positive rates were also significantly different between HCC with pathological grades I (4/10), II(14/20) and III(12/12) (40.0% vs 70.0% vs 100%, respectively, P < 0.05). The expression of hTERT was positively correlated to the recurrence of patients (P < 0.05). The transfected cells manifested typical apoptotic morphology, and the apoptotic peak appeared before G₁ phase of cell cycle. Tumorigenesis of the transfected cells in nude mice was significantly inhibited. The survival time of nude mice inoculated with transfected cells was markedly prolonged, in comparison with that of control mice.

CONCLUSION: The aberrant expression of hTERT gene may be related to the pathogenesis and progression of HCC. The highly expressed hTERT gene may be regarded as a marker for the recurrence of HCC. The growth of HepG2 cells can be effectively inhibited and the apoptosis can be promoted by transfection of antisense telomerase RNA.

Relationship between bcl-2 gene expression and cell proliferation and apoptosis in human gastric carcinomas

AIM: To investigate the relationship between bcl -2 gene expression levels in human gastric carcinoma and the frequency of tumor cell proliferation activity and apoptosis.

METHODS: In situ hybridization and immunohistochemistry methods were used to study the frequencies of expressions of bcl -2 gene and nuclear antigen of proliferating cells (PCNA) in 53 gastric carcinomas. Meanwhile, an in situ apoptotic cell detection (TUNEL method) was adopted to compare the number of apoptotic cells and PCNA with the Bcl -2 protein expression in each case.

RESULTS: Of the 53 gastric carcinomas, 41 and 43 expressed bcl -2 mRNA and Bcl -2 protein, which were count for 77.4% and 81.1% respectively. There was no significant difference between the positive rates obtained by these two methods. The apoptotic index of gastric carcinomas negatively related to PCNA index (r = -0.993, P < 0.01). With the increase of Bcl-2 protein expression , the cell proliferating activity increased but the apoptosis decreased in the tumor cells. Significant difference of cell proliferation and apoptosis existed between +++ group and ++ group of Bcl -2 protein expression (t = 2.552, 2.699, P < 0.05) as well as between the former two groups and the -, + group (t = 4.487, 3.975, 2.807, 3.094, 4.885, 5.816, 3.404, 3.895, P < 0.01) respectively.

CONCLUSION: The overexpression of bcl -2 gene inhibits cell apoptosis and excessive cell proliferation in the development and progress of gastric carcinomas.

Protein expression of fragile histidine triad and non-metastasis 23-H1 and their clinicopathological significance in gastric cancer

AIM: To explore the expression of fragile histidine triad (FHIT) and non-metastasis 23-H₁ (nm23-H₁) and to investigate their relations with clinicopathological behaviors of gastric cancer.

METHODS: PV9000 two-step immunohistochemical method was employed to detect the expression of FHIT and nm23-H₁ in 98 cases of gastric cancer.

RESULTS: The positive rates of FHIT and nm23-H₁ expression were 38.8% (38/98) and 33% (28/87) respectively. The FHIT expression related to the histological classification, Lauren classification and lymph node metastasis of gastric cancer (P < 0.05). The positive rate of FHIT protein expression became higher with the development of gastric cancer, but there was no significance (P > 0.05). The nm23-H₁ expression was negatively related to clinical staging and lymph node metastasis (P < 0.05).

CONCLUSION: FHIT may be an important candidate of tumor suppressor gene in gastric cancer. The expression of FHIT and nm23-H₁ protein has close relations with lymph node metastasis in gastric cancer, and they may work synergistically and can be important markers for predicting metastasis and evaluating prognosis of gastric cancer.

P53 and Rb tumor suppressor gene alterations in gastric cancer

Inactivation of tumor suppressor genes has been frequently observed in gastric carcinogenesis. Our purpose was to study the involvement of p53, APC, DCC, and Rb genes in gastric carcinoma.

METHOD

Loss of heterozygosity of the p53, APC, DCC and Rb genes was studied in 22 gastric cancer tissues using polymerase chain reaction; single-strand conformation polymorphism of the p53 gene exons 5-6 and exons 7-8 was studied using 35S-dATP, and p53 expression was detected using a histological immunoperoxidase method with an anti-p53 clone.

RESULTS AND DISCUSSION

No loss of heterozygosity was observed in any of these tumor suppressor genes; homozygous deletion was detected in the Rb gene in 23% (3/13) of the cases of intestinal-type gastric carcinoma. Eighteen (81.8%) cases showed band mobility shifts in exons 5-6 and/or 7-8 of the p53 gene. The presence of the p53 protein was positive in gastric cancer cells in 14 cases (63.6%). Normal gastric mucosa showed negative staining for p53; thus, the immunoreactivity was likely to represent mutant forms. The correlation of band mobility shift and the immunoreactivity to anti-p53 was not significant (P =.90). There was no correlation of gene alterations with the disease severity.

CONCLUSIONS

The inactivation of Rb and p53 genes is involved in gastric carcinogenesis in our environment. Loss of the Rb gene observed only in the intestinal-type gastric cancer should be further evaluated in association with Helicobacter pylori infection. The p53 gene was affected in both intestinal and diffuse histological types of gastric cancer.

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Construction of an oral recombinant DNA vaccine strain of live attenuated Salmonella typhimurium carrying H. pylori neutrophil activating protein

AIM: To construct a live attenuated Salmonella typhimurium (S. typhimurium) strain carrying H. pylori-neutrophil activating protein (HP-NAP) gene as an oral recombinant DNA vaccine.

METHODS: By genetic engineering method, a 435 bp napA gene (encoding HP-NAP) was subcloned into an eukaryotic expression vector pIRES. After sequencing and BLAST analysis, the identified recombinant plasmid was then transformed into a live attenuated S. typhimurium strain SL7207.

RESULTS: By using polymerase chain reaction (PCR) and restriction enzyme digestion, a recombinant eukaryotic expression plasmid pIRES-napA containing napA gene of H. pylori was constructed, and the recombinant plasmid was transformed successfully into the live attenuated S. typhimurium strain SL7207. Most of the H. pylori-napA sequences in recombinant plasmid pIRES-napA were homologized with that of SS1 strain reported by GenBank, and the homology of nucleotide and protein was 98%, respectively.

CONCLUSION: A recombinant live attenuated S. typhimurium strain carrying HP-NAP gene as DNA vaccine is successfully constructed. The results lay the foundation for developing multivalent oral DNA vaccine against H. pylori infection.

Novel nanosensors for rapid analysis of telomerase activity

Elevated telomerase levels are found in many malignancies, offering an attractive target for therapeutic intervention and diagnostic or prognostic purposes. Here we describe the use of a novel nanosensor developed for rapid screens of telomerase activity in biological samples. The technique utilizes magnetic nanoparticles that, on annealing with telomerase synthesized TTAGGG repeats, switch their magnet state, a phenomenon readily detectable by magnetic readers. We tested the efficacy of different telomerase inhibitors in crude human and murine samples and show that phosphorylation of telomerase regulates its activity. High-throughput adaptation of the technique by magnetic resonance imaging allowed processing of hundreds of samples within tens of minutes at ultrahigh sensitivities. Together, these studies establish and validate a novel and powerful tool for rapidly sensing telomerase activity and provide the rationale for developing analogous magnetic nanoparticles for in vivo sensing.

Alterations of mtDNA copy number in gastric carcinoma

AIM: To explore the relationship between mitochondrial DNA (mtDNA) and gastric cancer by comparing the difference of mtDNA copy number in gastric cancers and paracancerous tissues.

METHODS: Hypervariable reigon (HV)₁ and HV₂ of mitochondrial D-loop region from 20 cases of gastric cancer and 20 paracancerous tissues were amplified by PCR; meantime b-actin was served as a quantitative standard marker, followed by polyacrylamide gel electrophoresis (PAGE) and silver staining, in which the difference of mtDNA copy number was compared between gastric cancers and paracancerous tissues.

RESULTS: There existed significantly quantitative difference in HV₁, HV₂ (standardized with b-actin) between gastric cancers and paracancerous tissues (P < 0.01). mtDNA copy number was associated with important enzymes in nucleus such as AKP, cAMP-PDE and cGMP-PDE (P < 0.05), although not with tumor histological type and invasive depth (P > 0.05).

CONCLUSION: The occurrence of gastric cancer is closely associated with decreased mtDNA copy number, which may be a new tumor marker.

Influence of H. pylori on cyclinD1 and PCNA mRNA expression in HepG2 cell line

AIM: To observe the effects of Helicobacter pylori (H. pylori) on cyclinD1 and PCNA mRNA expression in a human hepatoma cell line HepG2.

METHODS: H. pylori was co-cultured with HepG2 for 1, 3,6, 12 and 24 h. The cyclinD1 and PCNA mRNA expression was detected by semi-quantitative RT-PCR.

RESULTS: When HepG2 cells were cocultured with H. pylori CagA⁺ strain, the amount of cyclinD1 mRNA was increased 4.0-fold by 3 h and PCNA mRNA was increased 2.0-fold by 6 h, compared with that of uninfected control. Neither cyclinD1 mRNA nor PCNA mRNA of the HepG2 cells was increased after incubation with H. pylori CagA^- strain.

CONCLUSION: H. pylori can induce increasing expression of cyclinD1 and PCNA mRNA in HepG2, which may play some roles in the development of hepatocellular carcinoma.

Expression of Helicobacter pylori Hsp60 protein and its immunogenicity

AIM: To express Hsp60 protein of H pylori by a constructed vector and to evaluate its immunogenicity.

METHODS: Hsp60 DNA was amplified by PCR and inserted into the prokaryotie expression vector pET-22b (+), which was transformed into BL21 (DE3) E.coli strain to express recombinant protein. Immunogenicity of expressed Hsp60 protein was evaluated with animal experiments.

RESULTS: DNA sequence analysis showed Hsp60 DNA was the same as GenBank’s research. Hsp60 recombinant protein accounted for 27.2% of the total bacterial protein, and could be recognized by the serum from H pylori infected patients and Balb/c mice immunized with Hsp60 itself.

CONCLUSION: Hsp60 recombinant protein might become a potential vaccine for controlling and treating H pylori infection.

Survivin, versatile modulation of cell division and apoptosis in cancer

Survivin is a member of the inhibitor of apoptosis (IAP) gene family that has attracted attention from several viewpoints of basic and translational research. Its cell cycle-regulated expression at mitosis and association with the mitotic apparatus have been of interest to cell biologists studying faithful segregation of sister chromatids and timely separation of daughter cells. Investigators interested in mechanisms of apoptosis have found survivin an evolving challenge: while survivin inhibits apoptosis in vitro and in vivo, this pathway may be more selective as compared to cytoprotection mediated by other IAPs. Finally, basic and translational researchers in cancer biology have converged on survivin as a pivotal cancer gene, not simply for its sharp expression in tumors and not in normal tissues, but also for the potential exploitation of this pathway in cancer diagnosis and therapy. The objective of the present contribution is to line up current evidence and emerging concepts on the multifaceted functions of survivin in cell death and cell division, and how this pathway is being pursued for novel cancer therapeutic strategies.

Detection of serum anti-Helicobacter pylori immunoglobulin G in patients with different digestive malignant tumors

AIM: To investigate the seroprevalence of Helicobacter pylori infection in patients with different digestive malignant tumors.

METHODS: Enzyme linked immunosorbent assay (ELISA) was used to detect serum anti-Helicobacter pylori IgG antibody in 374 patients with different digestive malignant tumors and 310 healthy subjects (normal control group).

RESULTS: The seroprevalence of Helicobacter pylori infection was 61.50% (230/374) and 46.77% (145/310), respectively, in patients with digestive tumors and normal controls (P < 0.05). The seroprevalence was 52.38% (33/63), 86.60% (84/97), 83.14% (84/101), 45.24 (19/42), 51.13% (18/35) and 44.44% (16/36), respectively in patients with carcinomas of esophagus, stomach, duodenum, rectum, colon and liver (P < 0.01). In patients with intestinal and diffuse type gastric cancers, the seroprevalence was 93.75% (60/64) and 72.73% (24/33), respectively (P < 0.05). In patients with gastric antral and cardiac cancers, the seroprevalence was 96.43% (54/56) and 73.17% (30/41), respectively (P < 0.05). In patients with ulcerous and proliferous type duodenal cancers, the seroprevalence of H. pylori infection was 91.04% (61/67) and 52.27% (23/44), respectively (P < 0.05). In patients with duodenal bulb and descending cancers, the seroprevalence was 94.20% (65/69) and 45.20% (19/42), respectively (P < 0.05).

CONCLUSION: H. pylori infection is associated with occurrence and development of gastric and duodenal carcinomas. Furthermore, it is also associated with histological type and locations of gastric and duodenal carcinomas.

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Helicobacter pylori and gastric malignancies

Despite decreasing incidence during the last 50 years, gastric cancer still ranks as one of the most frequent cancers. A multifactorial model of human gastric carcinogenesis is currently accepted in which different dietary and nondietary factors, including genetic susceptibility of the host and Helicobacter pylori infection are involved at different stages in the cancer process. On the molecular level, at least two phenotypes, associated with distinct pathways of genome destabilization, have been identified. However, applying new technologies such as cDNA microarrays a new era in the analysis of molecular markers has started. This molecular technology may open the path towards novel treatment modalities, i.e. gene therapy. Epidemiological, biological, and molecular genetic studies have also implicated the role of H. pylori in lymphomagenesis. Knowledge of pathogenesis and therapy is increasing while good epidemiological data are rare. Many studies have demonstrated that MALT-type lymphomas develop along two different pathways: t(11;18)-positive cases, and t(11;18)-negative cases. Meanwhile, a third translocation could be detected, the t(14;18), opening the discussion of a possible third pathway of lymphoma development.

Expression of estrogen inducing gene PS2/TFF1 in gastric cancer and precancerous lesions

AIM

To determine the significance of PS2/TFF1 protein expression in chronic superficial gastritis (CSG), gastric ulcer (GU),gastric mucosal intestinal metaplasia (IM), gastric mucosal dysplasia and gastric cancer(GC).

METHODS

Pathologic specimens of 121 patients with gastric mucosal diseases and 20 healthy volunteers were immunostained for PS2/TFF1.

RESULTS

Positive PS2/TFF1 staining was seen throughout all epithelia with normal gastric mucosas, CSG, GU and in complete type of intestinal metaplasia (20/21). On the contrary, 11 of 20 incomplete type of intestinal metaplasia had positive staining (P <0.01). The expressions of PS2/TFF1 protein in CSG and GU were significantly higher than that in control group (P <0.01), while the expressions of PS2/TFF1 protein in IM,gastric mucosal dysplasia and GC were obviously lower than that in control group (P <0.01).

CONCLUSION

Our results indicate that PS2/TFF1 may play an important role in gastric mucosal protection,and loss of PS2/TFF1 expression may occur as an early event in the malignant transformation process of intestinal-type tumors.

Stability of randomly amplified polymorphic DNA fingerprinting in genotyping clinical isolates of Helicobacter pylori

AIM: H pylori genomes are highly diversified. This project was designed to genotype H pylori isolates by the polymerase chain reaction (PCR)-based randomly amplified polymorphic DNA (RAPD) fingerprinting technique and to verify its stability by Southern blotting and DNA sequencing.

METHODS: Clinical isolates of H pylori were cultured from gastric antra and cardia of 73 individuals, and genomic DNA was prepared for each isolate. RAPD was carried out under optimized conditions. 23S rDNA was regarded as an internal control, and a 361 bp rDNA fragment (RDF) was used as a probe to screen the RAPD products by Southern blotting. Ten RDFs from different clinical isolates and the flanking regions (both upstream and downstream) of four RDFs were amplified and sequenced.

RESULTS: H pylori isolates from different individuals had different RAPD profiles, but the profiles for isolates cultured from different gastric sites of a given individual were identical in all but one case. Isolates from 27 individuals were RDF positive by Southern blotting. Sequences of the RDFs and their flanking regions were almost the same between the RDF positive and negative isolates as determined by Southern blotting. There was no binding site for random PCR primer inside the sequences.

CONCLUSION: RAPD is very useful in genotyping H pylori grossly on a large scale. However, it seems unstable in amplification of low yield fragments, especially those that do not appear as visible bands on the agarose gel stained with EB, since the primer is partially matched to the template.

Isolation of a novel member of small G protein superfamily and its expression in colon cancer

AIM: APMCF1 is a novel human gene whose transcripts are up-regulated in apoptotic MCF-7 cells. In order to learn more about this gene’s function in other tumors, we cloned its full length cDNA and prepared its polyclonal antibody to investigate its expression in colon cancers with immunohistochemistry.

METHODS: With the method of 5’ rapid amplification of cDNA end (RACE) and EST assembled in GenBank, we extended the length of APMCF1 at 5’ end. Then the sequence encoding the APMCF1 protein was amplified by RT-PCR from the total RNA of apoptotic MCF-7 cells and cloned into the prokaryotic expression vector pGEX-KG to construct recombinant expression vector pGEX-APMCF1. The GST-APMCF1 fusion protein was expressed in E. coli and used to immunize rabbits to get the rabbit anti-APMCF1 serum. The specificity of polyclonal anti-APMCF1 antibody was determined by Western blot. Then we investigated the expression of Apmcf1 in colon cancers and normal colonic mucosa with immunohistochemistry.

RESULTS: A cDNA fragment with a length of 1745 bp was obtained. APMCF1 was mapped to chromosome 3q22.2 and spanned at least 14.8 kb of genomic DNA with seven exons and six introns contained. Bioinformatic analysis showed the protein encoded by APMCF1 contained a small GTP-binding protein (G proteins) domain and was homologous to mouse signal recognition particle receptor β(SRβ). A coding region covering 816 bp was cloned and polyclonal anti-APMCF1 antibody was prepared successfully. The immunohistochemistry study showed that APMCF1 had a strong expression in colon cancer.

CONCLUSION: APMCF1 may be the gene coding human signal recognition particle receptor β and belongs to the small-G protein superfamily. Its strong expression pattern in colon cancer suggests it may play a role in colon cancer development.

Identification of H. pylori strain specific DNA sequences between two clinical isolates from NUD and gastric ulcer by SSH

AIM: The genomes of Helicobacter pylori (H. pylori) from different individuals are different. This project was to identify the strain specific DNA sequences between two clinical H. pylori isolates by suppression subtractive hybridization (SSH).

METHODS: Two clinical H. pylori isolates, one from gastric ulcer (GU, tester) and the other from non-ulcer dyspepsia (NUD, driver), were cultured and the genomic DNA was prepared and submitted to Alu I digestion. Then two different adaptors were ligated respectively to the 5’-end of two aliquots of the tester DNA fragments and SSH was made between the tester and driver DNA. The un-hybridized tester DNA sequences were amplified by two sequential PCR and cloned into pGEM-T-Easy Vector. The tester strain specific inserts were screened and disease related DNA sequences were identified by dot blotting.

RESULTS: Among the 240 colonies randomly chosen, 50 contained the tester strain specific DNA sequences. Twenty three inserts were sequenced and the sizes ranged from 261 bp to 1036 bp. Fifteen inserts belonged to the H.pylori plasmid pHPO100 that is about 3.5 kb and codes a replication protein A. Other inserts had patches of homologous to the genes of H.pylori in GenBank. Various patterns of dot blots were given and no GU strain unique DNA sequences were found when 4 inserts were used as probes to screen the genomic DNA from 27 clinical isolates, 8 from GU, 12 from duodenum ulcer (DU), 4 from GU-DU, 2 from NUD and 1 from gastric cancer (GC). But a 670 bp DNA fragment (GU198) that was a bit homologous to the 3’-end of the gene of thymidylate kinase was positive in 7 GU strains (7/8), 3 GU-DU strains (3/4) and 3 DU strains (3/12). A 384 bp fragment (GU79) of the replication gene A (repA) was positive only in 4 H.pylori isolates, 2 from GU and 2 from GU-DU.

CONCLUSION: Differences exist in the genes of different H.pylori isolates. SSH is very effective to screen H.pylori strain specific DNA sequences between two clinical isolates, and some of these sequences may have clinical significance.

Primary adenocarcinomas of lower esophagus, esophagogastric junction and gastric cardia: in special reference to China

Gastric cardia adenocarcinoma (GCA) is an under-studied subject. The pathogenesis, molecular changes in the early stage of carcinogenesis and related risk factors have not been well characterized. There is evidence, however, that GCA differs from cancer of the rest of the stomach in terms of natural history and histopathogenesis. Adenocarcinomas of the lower esophagus, esophagogastric junction (EGJ) and gastric cardia have been given much attention because of their increasing incidences in the past decades, which is in striking contrast with the steady decrease in distal stomach adenocarcinoma. In China, epidemiologically, GCA shares very similar geographic distribution with esophageal squamous cell carcinoma (SCC), especially in Linzhou (formerly Linxian County), Henan Province, North China, the highest incidence area of esophageal SCC in the world. Historically, both GCA and SCC in these areas were referred to as esophageal cancer (EC) by the public because of the common syndrome of dysphagia. In Western countries, Barrett's esophagus is very common and has been considered as an important precancerous lesion of adenocarcinoma at EGJ. Because of the low incidence of Barrett's esophagus in China, it is unlikely to be an important factor in early stage of EGJ adenocarcinoma development. However, Z line up-growth into lower esophagus may be one of the characteristic changes in these areas in early stage of GCA development. Whether intestinal metaplasia (IM) is a premalignant lesion for GCA is still not clear. Higher frequency of IM observed at adjacent GCA tissues in Henan suggests the possibility of IM as a precancerous lesion for GCA in these areas. Molecular information on GCA, especially in early stage, is very limited. The accumulated data about the changes of tumor suppressor gene, such as p53 mutation, and ontogeny, such as C-erbB2, especially the similar alterations in GCA and SCC in the same patient, indicated that there might be some similar risk factors, such as nitrosamine, involved in both GCA and SCC in Henan population. The present observations also suggest that GCA should be considered as a distinct entity.

Expression of survivin protein in human colorectal carcinogenesis

AIM: To identify the role of survivin in colorectal carcinogenesis and the relationship between Survivin and histological differentiation grade of colorectal carcinoma.

METHODS: Immunohistochemical staining of survivin by using the monoclonal antibody was performed by the standard streptavidin-peroxidase (SP) technique for the 188 paraffin sections which included 30 normal colorectal mucosas, 41 adenomas with low grade dysplasia, 30 adenomas with high grade dysplasia, and 87 colorectal carcinomas which were classified as high, middle and low differentiated subgroups which included 33, 28, 26 cases respectively.

RESULTS: Expression of survivin was observed in the cytoplasm of adenoma with dysplasia and colorectal carcinoma cells. No immunoreactivity of survivin was seen in normal mucosas. The positive rate of survivin increased in the transition from normal mucosas to adenomas with low grade dysplasia to high grade dysplasia/carcinomas (0.0%, 31.7%, 56.7% and 63.2% respectively). But the difference between high grade dysplasia and carcinomas had no statistical significance. Positive rate was not related to histological differentiation grade of colorectal carcinoma. Moreover, there was no correlation between histological differentiation grade of colorectal carcinoma and immunoreactive intensity of survivin.

CONCLUSION: The expression of survivin is the essential event in the early stage of colorectal carcinogenesis and plays an important role in the transition sequence and it is not related to histological differentiation grade of colorectal carcinoma. It thus may provide a new diagnostic and therapeutic target in colorectal cancer.