Helicobacter pylori-induced downregulation of the secretory leukocyte protease inhibitor (SLPI) in gastric epithelial cell lines and its functional relevance for H. pylori-mediated diseases

The secretory leukocyte protease inhibitor (SLPI) exerts antiproteolytic activity towards serine proteases, as well as anti-microbial and anti-inflammatory effects. To investigate its role in H. pylori-mediated diseases, SLPI expression was analyzed by RT-PCR, ELISA and immunohistochemistry in clinical samples and gastric tumor cell lines. Determination of the mucosal SLPI levels in 126 patients confirmed the previously reported downregulation of SLPI in H. pylori-infected patients. The lower SLPI levels in antral biopsies of H. pylori-positive subjects were associated with a 30-fold increase (p<0.01) in neutrophil elastase activity, and a significant negative correlation was demonstrated for both parameters (R=-0.63, p=0.0002). Eradication of the bacterium in a long-term study (5-7 years) led to a recovery of mucosal SLPI expression. In vitro experiments using four gastric tumor cell lines (AGS, MKN-28, MKN-45, NCI-N87) generally confirmed the clinical findings. While the co-incubation of these cell lines with H. pylori resulted in lower or unchanged SLPI protein levels, the corresponding SLPI mRNA amounts were upregulated by up to five-fold (p=0.006) in all cell lines. Taken together, these results indicate that the reduction in antral SLPI levels in H. pylori-infected subjects has a functional relevance for gastric mucosa and the H. pylori-induced decrease in SLPI is primarily regulated at the posttranslational level.

A novel region of amplification at 11p12-13 in gastric cancer, revealed by representational difference analysis, is associated with overexpression of CD44v6, especially in early-onset gastric carcinomas

Diffuse-type gastric carcinomas (GCs) are often difficult to characterize because of contamination of tumor samples by surrounding normal tissue. As such, information regarding chromosomal aberrations in this subtype of GCs is limited. In this study, we used representational difference analysis to pinpoint genomic amplifications occurring in diffuse-type GCs. We found nine differential products from two novel regions of amplification in two tumors: one product mapped to 19p13.1 and eight mapped to a 1.8-Mb region in chromosomal segment 11p12-13. These amplifications were confirmed using Southern blot analysis and occurred in 3/16 and 6/15 diffuse-type GCs, respectively. CD44, a well characterized cellular adhesion molecule involved in several human malignancies, is encoded by a gene located within 200 kb of the 11p12-13 amplification fragments. We confirmed that overexpression of isoform CD44v6 was correlated with amplification at 11p12-13 in 11/12 diffuse-type GCs. Since diffuse-type GCs occur more frequently in early-onset gastric carcinomas (EOGCs, presented at 45 years of age or younger) than in "conventional" GCs, and the tumors carrying the original amplifications were EOGCs, we investigated overexpression of CD44v6 in 107 EOGCs and 88 conventional GCs using tissue microarrays. We found frequent CD44v6 overexpression in both tumor groups (76% and 57% respectively) and, interestingly, significantly more cases with overexpression of CD44v6 in EOGCs than in conventional GCs (P = 0.005), irrespective of histology. These findings provide further evidence for both the relevance of CD44 in GC and for distinct molecular characteristics of EOGCs when compared with those of GCs occurring at a later age.

Differential expression of claudin-4 between intestinal and diffuse-type gastric cancer

Our previous microarray analysis of gastric cancer found that claudin-4 was differentially expressed between intestinal-type gastric cancer (IGC) and diffuse-type gastric cancer (DGC). Claudin-4 is a member of a large family of transmembrane proteins, claudins, essential in the formation and maintenance of tight junctions. To explore the roles of claudin-4 in the two histologically distinct types of gastric cancer, we selected 45 IGC and 48 DGC cases and then analyzed the expression of the protein using immunohistochemistry. We found that the overexpression of claudin-4 was greater in IGC than in DGC. A trend was observed between the overexpression of claudin-4 and lymph node metastasis, however, this association was not statistically significant. The results showed that the expression of claudin-4 was lower in DGC. Possibly it played a role in determining the diffuse phenotype and loose cohesion of cells in DGC in a similar manner as E-cadherin.

Proteomic analysis of a highly metastatic gastric cancer cell line using two-dimensional differential gel electrophoresis

Stomach cancer is still a major cause of death in Asian people despite a complete cure after the resection of early cancers, mainly because peritoneal dissemination is difficult to treat. In the present study, we used two-dimensional differential gel electrophoresis (2-D DIGE) to identify specific proteins differentially expressed between a highly metastatic stomach cancer cell line MKN-45-P and its parental cell line MKN-45. We detected 27 protein spots in at least 2 of 3 experiments which showed statistically significant differences in abundance. All 27 protein spots were identified using matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry (MS) and database-searching software. A proteomic analysis revealed 13 different proteins with some isoforms sharing different biochemical characteristics, and that 8 proteins were up-regulated, and 5 were down-regulated. The 13 proteins were mainly involved in protein synthesis (transfer RNA synthetase), metabolism (flavoprotein subunit, pyruvate kinase, adenylate kinase), receptor and signal transduction (annexins I and A2), the cytoskeleton (keratin 5, cytokeratin 8) and cell cycling (ts11). These results suggested that a proteomic approach including 2-D DIGE would be an efficient way to identify the proteins responsible for specific biological functions. Moreover, these observations might be novel findings leading to the prediction of postoperative peritoneal recurrence.

[Prophylactic effect of a selective COX-2 inhibitor celecoxib on carcinogen-induced gastric premalignant lesions in rats]

BACKGROUND & OBJECTIVE

Although we have previously showed that a selective cyclooxygenase-2(COX-2) inhibitor celecoxib prevents gastric cancer development in a rat model of gastric carcinogenesis, the role of celecoxib on gastric premalignant lesions remains unknown. This study was to explore whether celecoxib was effective for the prevention of premalignancy, and further to clarify its mechanism.

METHODS

Ninety-four male Wistar rats were divided into 5 groups. Group A (n=12) was fed with water only; group B (n=16) with daily 10 mg/kg celecoxib; group C (n=22) with 100 microg/ml N-methyl-No-nitro-N-nitrosoguanidine (MNNG); group D (n=22) with 100 microg/ml MNNG and daily 10 mg/kg celecoxib; group E (n=22) with 100 microg/ml MNNG and daily 3 mg/kg indomethacin. The rats in groups B to E were given 10% sodium chloride in the initial 6 weeks, and the rats in groups C to E were given 100 microg/ml MNNG in drinking water to induce premalignant lesions in the stomach. Six rats in group A, 8 in group B, 10 in group C, 10 in group D, and 10 in group E were killed at week 16, and others were killed at week 24. The occurrence rates of gastric premalignant lesions in the groups were compared. The mRNA and protein levels of COX-1 and COX-2 in gastric mucosa were determined by real-time polymerase chain reaction (PCR) and immunohistochemistry; prostaglandin E2 (PGE2) level was measured by an ELISA-based assay.

RESULTS

Ninety-three rats were studied. In week 16 and week 24, the occurrence rates of glandular atrophy in groups C, D, and E had no significant difference (P>0.05). In week 16, gastric mucosal dysplasia was not detected in groups C, D, and E; at week 24, the occurrence rates of dysplasia were 75% (9/12) on group C, 25% (3/12) in group D, and 46% (5/11) in group E. The occurrence rate of gastric mucosal dysplasia was significantly lower in group D than in group C (25% vs. 75%, P=0.039); there was no significant difference between group E and group C (46% vs. 75%, P=0.214). At week 16 and week 24, there was no significant difference in COX-1 expression between treatment groups and control group. The mRNA and protein levels of COX-2 in group C (3.29+/-1.50 and 3.41+/-0.94) were significantly higher than those in other groups (P<0.001). There was no significant difference in PGE2 level between groups C, D, and E (P>0.05).

CONCLUSIONS

Celecoxib effectively inhibits the development of gastric mucosal dysplasia in rats induced by MNNG, but has no effect on the PGE2 level in the gastric mucosa, indicating that the anti-neoplastic activities of celecoxib may be independent of COX-2.

Relationship between E-cadherin, matrix metalloproteinase-7 gene expression and clinicopathological features in gastric carcinoma

We investigated whether the abnormal expression of E-cadherin (ECD), in conjunction with the overexpression of matrix metalloproteinase-7 (MMP-7), is correlated with clinicopathological parameters such as metastasis and the prognosis for human gastric carcinoma. Using RT-PCR, we examined the expression of ECD and MMP-7 mRNA in 42 gastric carcinoma tissues and in the surrounding non-neoplastic mucosa. The macroscopic and histopathological tumor findings and the survival rates were obtained from the patient records. The level of ECD mRNA expression was lower in most of the neoplasms as compared to the corresponding non-neoplastic tissues (50 vs. 80.9%, respectively). The abnormal expression of ECD mRNA was significantly correlated to the microscopic classification and lymph node metastases (p<0.05), and its stage (p<0.05). The level of MMP-7 mRNA expression was higher in most neoplasms compared to the corresponding non-neoplastic tissues (66.6 vs. 50%, respectively). The overexpression of MMP-7 mRNA was significantly correlated with the microscopic classification, lymph node metastases (p<0.05), and its stage (p<0.01). However, a correlation between the abnormal expression of ECD and the overexpression of MMP-7 was not obtained. The survival rate of the patients with an ECD mRNA expression was longer than that of the patients without this expression, but this finding was not statistically significant (p=0.2162). The survival rates of patients with MMP-7 mRNA expression was significantly shorter than that of the patients without MMP-7 mRNA expression (p=0.0025). Overexpression of MMP-7 may be considered as a useful marker for determining metastasis and the prognosis of human gastric carcinoma rather than the abnormal expression of E-cadherin.

Expression status of RUNX1/AML1 in normal gastric epithelium and its mutational analysis in microdissected gastric cancer cells

Although Runt-related transcription factors RUNXs (RUNX1-3) have a high similarity in their structure, only RUNX3 is known to be involved in gastric carcinogenesis. First, we examined mRNA expression of these three RUNX genes in the gastric mucosa, and, finding only RUNX2 was not expressed there, we further investigated RUNX1 and RUNX3 expression in three regions including the pit, isthmus/neck, and gland regions of the human normal stomach and whether RUNX1 is involved in gastric carcinogenesis. The mRNA expression of RUNX1 and RUNX3 was examined by use of the three regions isolated by laser-captured microdissection (LCM) and by use of primary gastric cancer tissues. Furthermore, RUNX1 mutational analysis was performed in the cancer cells, which also were isolated from 44 paraffin-embedded gastric cancer tissues by LCM. RUNX1 was co-expressed with RUNX3 in the pit region, and has cell growth-inhibition activity similar to RUNX3. RUNX3 has been reported to be suppressed by DNA methylation in a subset of gastric cancers; however, the expression of RUNX1 mRNA was observed in all of the gastric cancer cell lines and gastric cancer tissues that we examined. No RUNX1 mutation was found in the 44 gastric cancer patients. Although RUNX1 is similar to RUNX3 in both the expression pattern in the stomach and its cell growth-inhibition activity, RUNX1 is not involved in most cases of gastric cancers. These results suggest that the transcriptional target genes are different between these two family genes.

Expression of the mutated transketolase TKTL1, a molecular marker in gastric cancer

The nonoxidative pentose phosphate pathway allows glucose conversion to ribose for DNA or RNA synthesis and glucose degradation to lactate controlled by transketolase enzyme reactions. It has been postulated, that this pathway is of the utmost importance in tumors for the proliferation process. We detected a strong upregulation of the mutated transketolase transcript (TKTL1) in a considerable number of patients with gastric cancer (GC) or cancer of the gastroesophageal junction (GEJ). While only 10.8% of the cancer tissues revealed a significant mRNA upregulation, 36.9% of the cancer tissues demonstrated a protein overexpression. We propose that TKTL1 upregulation is a common phenomenon in GC and cancer of the GEJ leading to an enhanced, oxygen-independent glucose usage which might contribute to a more aggressive tumor growth. Since molecular targeted inhibition of transketolase enzyme reactions suppresses tumor growth and metastasis, TKTL1 could be a relevant target for anti-transketolase therapies in gastric cancer.

Carcinogenesis in mouse stomach by simultaneous activation of the Wnt signaling and prostaglandin E2 pathway

BACKGROUND & AIMS

Accumulating evidence indicates that prostaglandin E(2) (PGE(2)), a downstream product of cyclooxygenase 2 (COX-2), plays a key role in gastric tumorigenesis. The Wnt pathway is also suggested to play a causal role in gastric carcinogenesis. However, the molecular mechanism remains poorly understood of how the Wnt and PGE(2) pathways contribute to gastric tumorigenesis. To investigate the role of Wnt and PGE(2) in gastric cancer, we have generated transgenic mice that activate both pathways and examined their phenotypes.

METHODS

We constructed K19-Wnt1 transgenic mice expressing Wnt1 in the gastric mucosa using the keratin 19 promoter. We then crossed K19-Wnt1 mice with another transgenic line, K19-C2mE, to obtain K19-Wnt1/C2mE compound transgenic mice. The K19-C2mE mice express COX-2 and microsomal prostaglandin E synthase-1 (mPGES-1) in the stomach, showing an increased gastric PGE(2) level. We examined the gastric phenotypes of both K19-Wnt1 and K19-Wnt1/C2mE mice.

RESULTS

K19-Wnt1 mice had a significant suppression of epithelial differentiation and developed small preneoplastic lesions consisting of undifferentiated epithelial cells with macrophage accumulation. Importantly, additional expression of COX-2 and mPGES-1 converted the preneoplastic lesions in the K19-Wnt1 mice into dysplastic gastric tumors by 20 weeks of age. Notably, we found mucous cell metaplasia in the glandular stomach of the K19-Wnt1/C2mE mice as early as 5 weeks of age, before the dysplastic tumor development.

CONCLUSIONS

Wnt signaling keeps the gastric progenitor cells undifferentiated. Simultaneous activation of both Wnt and PGE(2) pathways causes dysplastic gastric tumors through the metaplasia-carcinoma sequence.

Helicobacter pylori induces mono-(adenosine 5'-diphosphate)-ribosylation in human gastric adenocarcinoma

Mono-(adenosine 5'-diphosphate) (ADP)-ribosylation, which transfers an ADP-ribose from nicotinamide adenine dinucleotide (NAD) to an acceptor protein, is an important post-translational modification of cellular proteins. Several bacterial toxins are known to possess the mono-ADP-ribosyltransferase activity to catalyze this reaction as a possible pathogenic factor. Therefore, the aim of this study was to examine whether H. pylori may also induce mono-ADP-ribosylation in a human gastric mucosal protein in association with gastric cancer development. Tumorous and adjacent non-tumorous mucosal tissue specimens were obtained from the surgically removed stomachs of 5 patients with gastric adenocarcinoma, and then were homogenized into cytosolic and membranous fractions. Each homogenate or an H. pylori extract was assayed for mono-ADP-ribosylation with [adenylate-(32)P]-NAD and 3-aminobenzamide, a potent inhibitor of poly-ADP-ribosylation. The radiolabeled proteins were separated by sodium dodecylsulfate-polyacrylamide gel electrophoresis followed by radio-image analysis. In the extracts from H. pylori, a strain-dependent, endogenous radiolabeling of 70-kDa protein was detected. An assay of the membranous fractions from 5 gastric adenocarcinomas with the extract of OMH4, a clinical H. pylori isolate, revealed notable radiolabelings of 55- and 45-kDa proteins, which were not found without the OMH4 extract. In contrast, the radiolabelings were minimal in the membranous fractions from respective non-tumorous mucosae, and they were not detected in any of the examined cytosolic fractions. All three radiolabelings of 70-, 55-, and 45-kDa proteins were dependent on NAD, but not on ADP-ribose. Snake venom phosphodiesterase digestion of the 3 radiolabeled proteins released only AMP. We thus found that H. pylori had an enzymatic mono-ADP-ribosyltransferase activity which enabled it to modify the 55- and 45-kDa membranous proteins of human gastric adenocarcinoma, as well as the 70-kDa protein of H. pylori itself. The possible roles underlying our observations on carcinogenesis or development of human gastric carcinoma are yet to be elucidated.

[Diallyl trisulfide induces apoptosis of human gastric cancer cell line MGC803 through caspase-3 pathway]

BACKGROUND & OBJECTIVE

Garlic and the organosulfer compound from garlic have antitumor effects, but the mechanisms still remain unclear. This study was to investigate the changes and significance of caspase-3 activity in diallyl trisulfide (DATS)-induced apoptosis of human gastric cancer cell line MGC803.

METHODS

Effects of DATS on the apoptosis of MGC803 cells and the change of activated caspase-3 were observed under a fluorescent and an electron microscopy, and detected by flow cytometry and Western blot.

RESULTS

After incubation with DATS, MGC803 cells showed typical apoptotic morphologic changes, and the apoptosis rate increased significantly. DATS activated caspase-3 in a time-dependent manner: the positive rates of activated caspase-3 were 1.9%, 3.0%, 7.3%, 14.4%, and 27.6% respectively in MGC-803 cells treated with 12 mg/L DATS for 0, 4, 8, 12 and 24 h. When treated with 12 mg/L DATS for 24 h, the apoptosis rate was significantly lower in the cells with pretreatment of Ac-DEVD-CHO (a caspase-3 inhibitor) than in the cells without pretreatment (5.1% vs. 23.0%, P<0.01), indicating that Ac-DEVD-CHO efficiently attenuated DATS-induced apoptosis of MGC803 cells. Moreover, pro-caspase-3 was hydrolyzed and activated in DATS-treated MGC803 cells.

CONCLUSION

DATS induces apoptosis in MGC803 cells which may be through the activation of caspase-3 pathway.

Relationship between immunoexpression of mucin peptide cores MUC1 and MUC2 and Lauren's histologic subtypes of gastric carcinomas

Laurèn's system subdivides gastric cancers into an intestinal type and a diffuse type. This histological classification mirrors histogenetic hypotheses according to which the intestinal-type cancer derives from intestinal metaplasia and dysplasia, while the diffuse-type originates directly from gastric mucosa, with or without a preceding non-metaplastic dysplasia. Studies concerning mucins expression in gastric neoplastic and preneoplastic lesions have provided contradictory data concerning such histogenetic relationships. The aim of the present study was to verify whether a correlation between mucins phenotype and Lauren's classification subsists. 40 gastric adenocarcinomas, subdivided, according to Laurèn's classification, into 27 intestinal-type, 10 diffuse-type and 3 unclassified cases, were examined for MUC1 and MUC2 immunohistochemical expression. Intestinal-type carcinomas displayed a MUC1-positive staining in 23/27 cases and a MUC2-positive immunoreaction in 10/27 cases. Diffuse-type carcinomas expressed MUC1 in 3/10 and MUC2 in 8/10 cases, respectively. According to the mucins expression pattern, three phenotypes were identified: the gastric phenotype (MUC1+/MUC2-); the gastro-intestinal phenotype (MUC1+/MUC2+) and the intestinal phenotype (MUC1-/MUC2+). The gastric phenotype was significantly higherin intestinal-type adenocarcinomas, whereas cases showing an intestinal phenotype were significantly more frequent in diffuse-type adenocarcinomas. These findings provide evidence for a lack of correlation between Lauren's classification and MUC1 and MUC2 phenotypes. In particular, the term intestinal-type tumour as referred to gland-forming gastric cancer does not seem to reflect an immunohistochemical phenotype.

Sodium nitrite-induced cytotoxicity in cultured human gastric epithelial cells

To investigate the effect of sodium nitrite on the viability of the human gastric adenocarcinoma epithelial cell line, AGS, cultured AGS cells were exposed to various concentrations of sodium nitrite for 24, 48 or 72 h. The cytotoxic response was assessed using a cell proliferation assay, and the extent of the response was evaluated on the basis of intracellular and extracellular levels of interleukin 1 beta (IL-1 beta), interleukin 6 (IL-6), interleukin 8 (IL-8) and tumor necrosis factor (TNF-alpha). Both mRNA and protein levels were measured for each cytokine. Sodium nitrite had a significant effect on AGS cell proliferation after a 72-h exposure. At low sodium nitrite concentrations (up to 6.25 mM), cell proliferation increased in a dose-dependent manner; however, exposure to higher concentrations resulted in a dose-dependent decrease in cell proliferation. Sodium nitrite at a low concentration (6.25 mM) increased IL-8 release, whereas IL-1 beta, IL-6, and TNF-alpha release increased only after exposure to high sodium nitrite concentration (25 mM). Our data demonstrate that sodium nitrite can induce the release of these inflammatory cytokines and that high concentrations of sodium nitrite decrease AGS cell proliferation.

Clinical significance of human kallikrein 10 gene expression in colorectal cancer and gastric cancer

BACKGROUND AND AIM

Recent evidence suggests that the human kallikrein 10 (KLK10) gene is differentially regulated in endocrine-related tumors and has potential as diagnostic and/or prognostic marker; however, KLK10 expression has never been investigated in gastrointestinal cancers. The aims of this study were to demonstrate expression and single nucleotide polymorphisms of KLK10 in colorectal cancer (CRC) and gastric cancer (GC), and to correlate the relative KLK10 expression level with clinicopathological factors of CRC and GC.

METHODS

Between March 2004 and January 2005, 63 patients with histologically confirmed CRC and 36 with GC were recruited into the study. Using quantitative real-time (qRT) RT-PCR and Western blot, KLK10 expression in tumor and non-tumor colorectal and gastric tissues was determined at the mRNA and protein levels. KLK10 protein was localized by immunohistochemistry. The KLK10 genomic DNA from 16 cases of paired normal/cancerous colorectal tissues was PCR-amplified and examined for single nucleotide polymorphisms by direct sequencing.

RESULTS

KLK10 mRNA expression was detected by qRT in 61 of 63 (96.8%) CRC specimens and in all GC specimens. KLK10 expression was much higher in tumor tissue than in the corresponding normal mucosal tissue at the mRNA and protein levels (P<0.01). The KLK10 mRNA expression level significantly correlated with lymphatic invasion (P=0.034) and clinical stage of CRC (P=0.025). The KLK10 mRNA expression level significantly correlated with the depth of GC invasion (P=0.018), clinical stage (P=0.045), patient sex (P=0.027) and Lauren type of gastric cancer (P=0.028). No mutations or polymorphisms were detected in exon 1, 2 and 5 of KLK10 gene in CRC. Single nucleotide polymorphisms were identified in codon 50 of exon 3, GCC (alanine) to TCC (serine). The genetic changes of exon 4 were located at codon 106 [GGC (glysine) to GGA (glysine)], codon 112 [ACG (threonine) to ACC (threonine)], codon 141 [CTA (leucine) to CTG (leucine)], and codon 149 [CCG (proline) to CTG (leucine)]. All were identical in tumor and corresponding normal tissue DNA from the same individuals.

CONCLUSION

KLK10 expression is up-regulated in CRC and GC and higher expression of KLK10 closely correlates with advanced disease stage, which predicts a poorer prognosis; however, further follow-up study is needed.

Celecoxib could reverse the hypoxia-induced Angiopoietin-2 upregulation in gastric cancer

We investigated the potential effect of Cyclooxygenase-2 (Cox-2) on hypoxia-induced Angiopoietin-2 (Ang-2) expression in gastric cancer cells. Our results revealed that hypoxia augmented Cox-2 and Ang-2 expressions. Also, the hypoxia-induced Ang-2 could be mimicked by CoCl(2) treatment while genestein treatment could partially counteract the hypoxia-induced Ang-2 expression. Celecoxib but not Cox-1 inhibitor sc-560 reversed the hypoxia-induced Ang-2 expression, while this effect could be partially restored by addition of exogenous PGE2. Our findings suggest that the hypoxia-elevated Ang-2 expression in gastric cancer cells may be mediated by both Cox-2-derived PGE2 and HIF-1alpha pathways, while celecoxib could counteract the hypoxia-induced Ang-2 expression.

Overexpression of nicotinamide N-methyltransferase in gastric cancer tissues and its potential post-translational modification

Gastric cancer is one of the most common cancers worldwide. The purpose of this study was to find out potential markers for gastric cancer. Tumor and normal tissues from 152 gastric cancer cases were analyzed by two-dimensional gel electrophoresis (2-DE). The images of silver stained gels were analyzed and statistical analysis of spot intensities revealed that spot 4262 showed higher expression (5.7-fold increase) in cancer tissues than in normal tissues (P < 0.001). It was identified by peptide mass fingerprinting as nicotinamide N-methyltransferase (NNMT). A monoclonal antibody with a detection limit down to 10 ng was produced against NNMT in mouse. Using the prepared monoclonal antibody, western blot analysis of NNMT was performed for gastric tissues from 15 gastric cancer patients and two gastric ulcer patients. The results corroborated those of 2-DE experiments. A single spot was detected in gastric ulcer tissues while four to five spots were detected in gastric cancer tissues. In cancer tissues, two additional spots of acidic and basic form were mainly detected on 2-DE gels. This suggests that NNMT receives a post-translational modification in cancer- specific manner.

Mechanism of ascorbic acid-induced reversion against malignant phenotype in human gastric cancer cells

OBJECTIVE

To find out the mechanisms of redifferentiation and reversion of malignant human gastric cancer cells induced by ascorbic acid.

METHODS

Human gastric cancer cells grown in the laboratory were used. The Trypan blue dye exclusion method was used to determine the cell doubling time. The electrophoresis rate and colonogenic potential were the indices used to measure the rate of redifferentiation. The content of malondialdehyde (MDA) was measured using the thiobarbituric acid (TBA) method. The activities of superoxide dismutase (SOD), catalase (CAT) and the content of H202 were evaluated by spectrophotography.

RESULTS

Six mmol/L ascorbic acid was used as a positive control. Human gastric cancer cells were treated with 75 microm hydrogen peroxide, which alleviated many of the malignant characteristics. For example, the cell surface charge obviously decreased and the electrophoresis rate dropped from 2.21 to 1.10 microm x s(-1) x V(-1) x cm(-1). The colonogenic potential, a measure of cell differentiation, decreased 90.2%. After treatment with ascorbic acid, there was a concentration- and time-dependent increase in hydrogen peroxide (H202) and the activity of superoxide dismutase (SOD). However, the activity of catalase (CAT) resulted in a concentration- and time-dependent decrease. SOD and 3-amino-1,2,4-triazole (AT) exhibited some effects, but there were statistically significant differences between the SOD and AT group and the H202 group.

CONCLUSIONS

Ascorbic acid induces growth inhibition and redifferentiation of human gastric cancer cells through the production of hydrogen peroxide.

Expression of the Intestinal Transcription Factor CDX2 in Carcinoid Tumors Is a Marker of Midgut Origin

Context.—Carcinoid tumors are classified according to their site of origin into foregut, midgut, or hindgut carcinoids, which have different presentations and prognosis. The intestinal transcription factor CDX2 has been found to be expressed in most intestinal adenocarcinomas but in less than one half of the gastrointestinal carcinoids according to 1 study.

Objective.—To determine whether CDX2 expression in carcinoid tumors varies by the site of origin and whether CDX2 expression is retained in metastatic disease.

Design.—Sections of formalin-fixed and paraffin-embedded tissue from 36 primary carcinoid tumors and 5 cases of metastatic carcinoid to the liver were immunohistochemically stained for CDX2. The percent of cells with nuclear immunoreactivity and the intensity of staining were assessed.

Results.—All 18 foregut carcinoids (10 pulmonary and 8 gastric) were negative (0%) for CDX2. All 11 midgut carcinoids (100%) were positive for CDX2 with moderate to strong staining in more than 50% of the cells. Only 2 (29%) of 7 of hindgut carcinoids were CDX2-positive with the 2 positive cases showing weak to moderate staining intensity in less than 10% of the cells. Expression of CDX2 in more than 50% of tumor cells was seen only in midgut carcinoids (P &lt; .001). CDX2 expression in metastatic tumors was consistent with the site of origin.

Conclusions.—Midgut carcinoid tumors and their metastases are distinct from foregut and hindgut carcinoids in that they express high levels of CDX2. Additional studies are needed to determine whether CDX2 immunostaining may be helpful in determining the primary site of metastatic carcinoid tumors of unknown origin.

Helicobacter pylori can induce heparin-binding epidermal growth factor expression via gastrin and its receptor

Both gastrin and Helicobacter pylori have been shown capable of up-regulating gene expression and protein shedding of heparin-binding epidermal growth factor (HB-EGF). Furthermore, the bacteria have previously been shown to induce serum hypergastrinemia in infected individuals. The aim of this work was to assess the extent to which the ability of H. pylori to up-regulate expression of HB-EGF can be attributed to its effect on gastrin. Gastric cells, transfected with either gastrin small interfering RNA or antisense plasmid or the gastrin/cholecystokinin-2 receptor (CCK-2R), were cultured for 24 hours with H. pylori(+/-), a CCK-2R antagonist. Gene expression levels were measured using reverse transcription-PCR, whereas protein changes were measured using ELISA, Western blotting, and immunofluorescence. H. pylori induced significantly higher levels of HB-EGF gene expression and ectodomain shedding in the CCK-2R-transfected cells than the vector control (P < 0.01). Addition of the CCK-2R inhibitor significantly decreased gene and shedding up-regulation. Gastrin down-regulation reduced the effect of the bacteria on HB-EGF gene and protein expression levels. Endogenous gastrin and CCK-2R expression were also found to be significantly up-regulated in all cell lines as a result of exposure to H. pylori (P < 0.02). Gastric mucosal tissue from H. pylori-infected individuals had significantly higher CCK-2R expression levels than noninfected (P < 0.003), and in hypergastrinemic mice, there was an increase in HB-EGF-expressing cells in the gastric mucosa and colocalization of HB-EGF with CCK-2R-positive enterochromaffin-like cells. In conclusion, gastrin and the CCK-2R play significant roles in the induction of HB-EGF gene and protein expression and ectodomain shedding by H. pylori.

Human β-defensin-3 induction in H pylori-infected gastric mucosal tissues

AIM: To examine human β-defensin-3 (hBD-3) expression in inflamed gastric mucosal tissues or MKN45 gastric cancer cells with or without H pylori infection for better understanding the innate immune response to H pylori.

METHODS: We used reverse transcription-polymerase chain reactions and immunohistochemistry to examine hBD-3 expression in inflamed gastric mucosal tissues or MKN45 gastric cancer cells with or without H pylori. Effects of hBD-3 against H pylori were also evaluated.

RESULTS: The mean mRNA expression of hBD-3 in H pylori-positive specimens was significantly higher than that in H pylori-negative specimens (P = 0.0002, Mann-Whitney). In addition, unlike uninfected samples, 8 of 15 (53.33%) infected mucosal samples expressed hBD-3 protein. H pylori dose-dependently induced mRNA expression of hBD-3 in MKN45 cells, an effect inhibited by adding anti-toll-like receptor (TLR)-4 antibody. HBD-3 protein completely inhibited H pylori growth.

CONCLUSION: Our results suggest that like hBD-2, hBD-3 may be involved in the pathophysiology of H pylori-induced gastritis.

Inhibitory effect of arsenic trioxide on angiogenesis and expression of vascular endothelial growth factor in gastric cancer

AIM: To investigate the inhibitory effect of As₂O₃ on angiogenesis of tumor and expression of vascular endothelial growth factor (VEGF) in tumor cells in vivo and in vitro.

METHODS: The solid tumor model was formed in nude mice with the gastric cancer cell line SGC-7901. The animals were randomly divided into three groups. As₂O₃ was injected into the arsenic-treated groups (2.5 mg/kg and 5 mg/kg) and the same volume of saline solution was injected into the control group. Microvessel density (MVD) and expression of VEGF were detected with immunofluorescence laser confocal technology. Further expression of VEGF protein and VEGF mRNA was measured with Western bloting and fluorescence quantitative RT- PCR in SGC-7901 cells treated with As₂O₃.

RESULTS: In nude mice, after treatment with 5 mg/kg and 2.5 mg/kg As₂O₃ respectively, about 50% and 30% tumor growth inhibition were observed correspondingly (P < 0.05, P < 0.05). Decrease in MVD appeared in As2O3-treated tumors compared with control group (P < 0.001, P < 0.001). MVD in tumors was significantly lower in 5 mg/kg group than in 2.5 mg/kg group (P < 0.01). The fluorescence intensity levels of VEGF in tumor cells were significantly lowered in the arsenic-treated groups (P < 0.01, P < 0.01). The fluorescence intensity level of VEGF in 5 mg/kg group was lower than that in 2.5 mg/kg group (P < 0.01). In vitro, the expression of VEGF protein decreased in dose- and time-dependent manner after the treatment with As₂O₃, but in VEGF mRNA no significant difference was found between the control group and the treated groups.

CONCLUSION: As₂O₃ can inhibit solid tumor growth by inhibiting the formation of new blood vessels. One of the mechanisms is that As₂O₃ can inhibit VEGF protein expression.

Pharmacodynamic studies of gefitinib in tumor biopsy specimens from patients with advanced gastric carcinoma

PURPOSE

Epidermal growth factor receptor (EGFR) is highly expressed in some gastric cancers and is implicated in cancer cell growth and proliferation. The objective of this study was to assess the in situ biologic activity of the EGFR tyrosine kinase inhibitor gefitinib in gastric tumor samples in a phase II study.

METHODS

Patients with previously treated stage IV adenocarcinoma of the stomach or gastroesophageal junction were randomly assigned to receive gefitinib (250 or 500 mg/d). Tumor biopsies, obtained at screening and on day 28 of treatment, were assessed for biomarker expression using immunohistochemistry and analysis of apoptosis.

RESULTS

One hundred sixteen tumor samples from 70 patients were available, 70 were baseline and 46 were on-therapy biopsies. At baseline, levels of EGFR expression significantly correlated with levels of phosphorylated EGFR (pEGFR; P < .001) and Ki67 expression (P = .011), but not with phosphorylated mitogen-activated protein kinase (pMAPK). After gefitinib treatment, levels of pEGFR in tumor cells were significantly reduced (P = .001); this was not the case for pMAPK and phosphorylated Akt (pAkt). However, in some cases gefitinib inhibited pAkt and these tumors had enhanced apoptosis. Likewise, there was a significant correlation between increased exposure to geftinib and enhanced apoptosis.

CONCLUSION

Gefitinib reached the tumors at concentrations sufficient to inhibit EGFR activation in advanced gastric carcinoma patients, although this did not translate into clinical benefit. Overall, intratumoral phosphorylation of MAPK and Akt was not significantly inhibited by gefitinib. However, the finding that decreases in pAkt correlated with enhanced apoptosis deserves further exploration.

Functional role of beta-adrenergic receptors in the mitogenic action of nicotine on gastric cancer cells

We previously reported that nicotine promoted gastric cancer cell growth via upregulation of cyclooxygenase 2 (COX-2). In the present study, we further investigated whether beta-adrenoceptors, protein kinase C (PKC), and extracellular signal-regulated kinase-1/2 (ERK1/2) were involved in the modulation of COX-2 expression and cell proliferation by nicotine in AGS, a human gastric adenocarcinoma cell line. Results showed that nicotine dose dependently increased the phosphorylation of EKR1/2 and the expression of AP-1 subunits c-fos and c-jun. In this connection, the ERK1/2 inhibitor U0126 abrogated the upregulation of AP-1 and COX-2 as well as cell proliferation induced by nicotine. Moreover, nicotine induced the translocation of PKC-betaI from cytosol to membrane and increased the total levels of PKC expression. Inhibition of PKC by staurosporine attenuated nicotine-induced ERK1/2 phosphorylation and COX-2 expression. Furthermore, atenolol and ICI 118,551, a beta1- and beta2-adrenoceptor antagonist, respectively, reversed the stimulatory action of nicotine on the expression of PKC, ERK1/2 phosphorylation, and COX-2 together with cell proliferation. Collectively, these results suggest that nicotine stimulates gastric cancer cell growth through the activation of beta-adrenoceptors and the downstream PKC-betaI/ERK1/2/COX-2 pathway.

Interleukin-18 is a critical factor for vascular endothelial growth factor-enhanced migration in human gastric cancer cell lines

Cell migration and angiogenesis are key steps in tumor metastasis. However, the mechanism of migration regulated by vascular endothelial growth factor (VEGF), a potent regulator of angiogenesis, is not completely understood. This study examined the relationship between VEGF and migration, along with the mechanism involved in the VEGF-regulated migration of human gastric cancer cells. The level of cell migration was increased by recombinant human (rh)VEGF-165 in the VEGF receptor-2-expressing SNU-601 cells. Interleukin (IL)-18 is associated with the malignant progression of tumors. Accordingly, this study examined the effect of IL-18 on the migration of cancer cells in order to identify the factors involved in VEGF-enhanced migration. Inhibiting IL-18 markedly reduced the level of VEGF-enhanced migration, and IL-18 increased cell migration directly through filamentous-actin polymerization and tensin downregulation. It was confirmed that rhVEGF-165 increased IL-18 production significantly. An antioxidant and an extracellular signal-regulated kinase (ERK)1/2-specific inhibitor blocked rhVEGF-165-enhanced IL-18 production. Accordingly, rhVEGF-165 increased the generation of region of interest (ROI) and activated the ERK1/2 pathway. These results suggest that rhVEGF-165 enhances IL-18 production via the generation of ROI and ERK1/2 phosphorylation, which results in the increased migration of gastric cancer cells.