Loss of liver E-cadherin induces sclerosing cholangitis and promotes carcinogenesis.

E-cadherin is an important adhesion molecule whose loss is associated with progression and poor prognosis of liver cancer. However, it is unclear whether the loss of E-cadherin is a real culprit or a bystander in liver cancer progression. In addition, the precise role of E-cadherin in maintaining liver homeostasis is also still unknown, especially in vivo. Here we demonstrate that liver-specific E-cadherin knockout mice develop spontaneous periportal inflammation via an impaired intrahepatic biliary network, as well as periductal fibrosis, which resembles primary sclerosing cholangitis. Inducible gene knockout studies identified E-cadherin loss in biliary epithelial cells as a causal factor of cholangitis induction. Furthermore, a few of the E-cadherin knockout mice developed spontaneous liver cancer. When knockout of E-cadherin is combined with Ras activation or chemical carcinogen administration, E-cadherin knockout mice display markedly accelerated carcinogenesis and an invasive phenotype associated with epithelial-mesenchymal transition, up-regulation of stem cell markers, and elevated ERK activation. Also in human hepatocellular carcinoma, E-cadherin loss correlates with increased expression of mesenchymal and stem cell markers, and silencing of E-cadherin in hepatocellular carcinoma cell lines causes epithelial-mesenchymal transition and increased invasiveness, suggesting that E-cadherin loss can be a causal factor of these phenotypes. Thus, E-cadherin plays critical roles in maintaining homeostasis and suppressing carcinogenesis in the liver.

Gastric cancer diagnosed after Helicobacter pylori eradication in diabetes mellitus patients.

BACKGROUND: Helicobacter pylori infection is the most important risk factor for gastric cancer, for which eradication therapy is commonly performed. However, gastric cancer is sometimes discovered after successful eradication of H. pylori. Much evidence indicates that diabetes mellitus (DM) is a risk factor for gastric cancer. The incidence and characteristics of gastric cancer diagnosed after H. pylori eradication in DM patients remain to be determined. METHODS: We followed the clinical course of patients who underwent H. pylori eradication therapy at our institution. Endoscopy was performed before and after eradication. We compared the incidence and clinical characteristics of gastric cancer arising in DM and non-DM patients. RESULTS: In total, 965 patients who underwent successful eradication (518 DM and 447 non-DM patients) were followed-up for an average of 4.5 years. During the follow-up period, 21 gastric cancers were diagnosed (12 in DM patients and 9 in non-DM patients). The incidence of gastric cancer after eradication was not significantly different between DM and non-DM patients (0.485 and 0.482 %/year, respectively). There was no significant difference in the pathology, diameter, depth, location, or treatment of gastric cancer between patients with and without DM. CONCLUSION: The incidence and characteristics of gastric cancer occurring after H. pylori eradication were comparable between DM and non-DM patients.

Apoptosis signal-regulating kinase 1 and cyclin D1 compose a positive feedback loop contributing to tumor growth in gastric cancer.

Mitogen-activated protein kinase (MAPK) pathways regulate multiple cellular functions and are highly active in many types of human cancers. Apoptosis signal-regulating kinase 1 (ASK1) is an upstream MAPK involved in apoptosis, inflammation, and carcinogenesis. This study investigated the role of ASK1 in the development of gastric cancer. In human gastric cancer specimens, we observed increased ASK1 expression, compared to nontumor epithelium. Using a chemically induced murine gastric tumorigenesis model, we observed increased tumor ASK1 expression, and ASK1 knockout mice had both fewer and smaller tumors than wild-type (WT) mice. ASK1 siRNA inhibited cell proliferation through the accumulation of cells in G1 phase of the cell cycle, and reduced cyclin D1 expression in gastric cancer cells, whereas these effects were uncommon in other cancer cells. ASK1 overexpression induced the transcription of cyclin D1, through AP-1 activation, and ASK1 levels were regulated by cyclin D1, via the Rb-E2F pathway. Exogenous ASK1 induced cyclin D1 expression, followed by elevated expression of endogenous ASK1. These results indicate an autoregulatory mechanism of ASK1 in the development of gastric cancer. Targeting this positive feedback loop, ASK1 may present a potential therapeutic target for the treatment of advanced gastric cancer.

[An elderly woman with macrocytic anemia and acute high-output heart failure following acute bleeding due to a gastric ulcer].

Although macrocytic anemia can develop in patients with acute blood loss, such anemia in very old patients is uncommon. In this report, we describe the course of an 89-year-old woman who had a rapid recovery from macrocytic anemia by medication only after acute blood loss due to a gastric ulcer. She had been treated with antihypertensive drugs for the previous 28 years at our outpatient clinic, and was admitted because of acute anemia 6 days after she had experienced tarry stool. Her hemoglobin (Hb) count and mean corpuscular volume (MCV) were 8.4 g/dl, and 103 fl, respectively. A gastroscopic examination indicated that the tarry stool originated from a fresh gastric ulcer. She was treated with an iron preparation, a diuretic and a proton pump inhibitor. The anemia was rapidly improved to Hb 10.5 g/dl and MCV 106 fl in one week, and to Hb 14.5 g/dl and MCV 99 fl in 4 weeks. At admission, she had slight pleural effusion and slight edema associated with an increase in her plasma brain natriuretic peptide (BNP) level (323 pg/ml), and her left ventricular ejection fraction was 76% based on the echocardiography findings, which are signs of the high-output heart failure without remarkable left ventricular diastolic dysfunction (E/e': 11.2). However, these signs improved rapidly, and her BNP level thereafter decreased to 114 pg/ml within four weeks.

Role of interleukin-32 in Helicobacter pylori-induced gastric inflammation.

Helicobacter pylori infection is associated with gastritis and gastric cancer. An H. pylori virulence factor, the cag pathogenicity island (PAI), is related to host cell cytokine induction and gastric inflammation. Since elucidation of the mechanisms of inflammation is important for therapy, the associations between cytokines and inflammatory diseases have been investigated vigorously. Levels of interleukin-32 (IL-32), a recently described inflammatory cytokine, are increased in various inflammatory diseases, such as rheumatoid arthritis and Crohn's disease, and in malignancies, including gastric cancer. In this report, we examined IL-32 expression in human gastric disease. We also investigated the function of IL-32 in activation of the inflammatory cytokines in gastritis. IL-32 expression paralleled human gastric tissue pathology, with low IL-32 expression in H. pylori-uninfected gastric mucosa and higher expression levels in gastritis and gastric cancer tissues. H. pylori infection increased IL-32 expression in human gastric epithelial cell lines. H. pylori-induced IL-32 expression was dependent on the bacterial cagPAI genes and on activation of nuclear factor κB (NF-κB). IL-32 expression induced by H. pylori was not detected in the supernatant of AGS cells but was found in the cytosol. Expression of the H. pylori-induced cytokines CXCL1, CXCL2, and IL-8 was decreased in IL-32-knockdown AGS cell lines compared to a control AGS cell line. We also found that NF-κB activation was decreased in H. pylori-infected IL-32-knockdown cells. These results suggest that IL-32 has important functions in the regulation of cytokine expression in H. pylori-infected gastric mucosa.

Influence of Helicobacter pylori eradication on the management of type 2 diabetes.

BACKGROUND/AIMS: H. pylori eradication therapy has been widely performed. In addition, the number of patients with type 2 diabetes is increasing worldwide. The aim of this study was to understand the influence of H. pylori eradication therapy on the management of type 2 diabetes. METHODOLOGY: A total of 174 patients with type 2 diabetes who did not have an active peptic ulcer or serious complications and were cured successfully of their H. pylori infection at our institute were included in this study. The time course of mean glycosylated hemoglobin (HbA1c) values and body mass index (BMI) during the year before and after H. pylori eradication were assessed by a paired Student's t-test. RESULTS: No significant changes in mean HbA1c values were observed during the year before or after eradication. However, the mean BMI, which did not change during the year before eradication, increased significantly at 6 months (23.1±2.6kg/m2, p<0.05) and 12 months (23.1±2.7kg/m2, p<0.05) after eradication as compared with the time point of eradication (22.9±2.6kg/m2). CONCLUSIONS: H. pylori eradication significantly increased BMI but not HbA1c in patients with type 2 diabetes, despite diabetes treatment.

Apoptosis signal-regulating kinase 1 regulates colitis and colitis-associated tumorigenesis by the innate immune responses.

BACKGROUND & AIMS: Mitogen-activated protein kinase (MAPK) signaling pathways regulate multiple cellular functions and are implicated in the pathogenesis of inflammatory bowel disease and colitis-associated cancer (CAC). Apoptosis signal-regulating kinase 1 (ASK1) is a MAPK kinase kinase; little is known about the role of ASK1 in colonic disease. We assessed the involvement of ASK1 in the development of intestinal inflammation and CAC. METHODS: Dextran sodium sulfate (DSS) or Citrobacter rodentium was used to induce colitis in wild-type (WT) and ASK1 knock-out (ASK1(-/-)) mice; CAC was induced by azoxymethane injection followed by repeated intake of DSS by the mice. Primary macrophages were isolated from WT and ASK1(-/-) mice and used to investigate the involvement of ASK1 in innate immune responses. Bone marrow chimeric mice were used to study the contribution of myeloid cells to colitis activity. RESULTS: ASK1 deficiency increased susceptibility to colonic inflammation in both models of colitis. In vitro, ASK1(-/-) macrophages were impaired in their ability to kill bacteria and had increased susceptibility to bacterial-induced apoptosis, because p38 was inactivated. Expression of antiapoptotic genes was greatly reduced in ASK1(-/-) macrophages. WT mice given transplants of ASK1(-/-) mouse-derived bone marrow cells developed more severe DSS-induced colitis than mice with WT-derived bone marrow cells. In the CAC model, ASK1(-/-) mice developed more numerous and larger tumors than WT mice through increased colonic inflammation. CONCLUSIONS: ASK1 controls the development of intestinal inflammation and CAC through the regulation of innate immunity.

Inhibitor of kappaB kinase beta regulates gastric carcinogenesis via interleukin-1alpha expression.

BACKGROUND & AIMS: Nuclear factor-kappaB (NF-kappaB) is an important transcription factor involved in various biological processes, including carcinogenesis. However, it is unknown whether NF-kappaB activation is involved in gastric carcinogenesis. METHODS: To explore the roles of inhibitor of kappaB kinase (IKKbeta), the key kinase for NF-kappaB activation, in gastric epithelium, we established a conditional gastric mucosal epithelium knockout mouse (Ikkbeta(DeltaST)). Gastric cancer was induced using N-methyl-N-nitrosourea (MNU). After 8 months, the number of tumors and their sizes were evaluated. Apoptosis was analyzed by terminal deoxynucleotidyl transferase-mediated deoxyuridine nick-end labeling staining, and levels of inflammatory cytokines were measured. RESULTS: No phenotypical or histologic difference was observed between untreated Ikkbeta(DeltaST) and controls (Ikkbeta(F/F)). The number of tumors was significantly less in the MNU-treated Ikkbeta(DeltaST) group than in the Ikkbeta(F/F) group (mean +/- standard error, 2.21 +/- 0.48 vs 0.80 +/- 0.23), and the size of the tumors did not differ (2.75 +/- 0.99 vs 2.89 +/- 1.12 mm). After a single oral dose of MNU, interleukin (IL)-1alpha was up-regulated significantly in control mice compared with Ikkbeta(DeltaST) mice, whereas the levels of IL-1beta, IL-6, and tumor necrosis factor-alpha were unchanged. MNU significantly increased apoptotic cell death in Ikkbeta(DeltaST) mice compared with Ikkbeta(F/F) mice, and apoptosis was dependent on decreased IL-1alpha expression. IL-1alpha also induced the proliferation of gastric cancer cells. Fewer tumors were observed in IL-1-receptor knockout mice (Il-1r(-/-); 1.17 +/- 0.44) than in control mice (2.42 +/- 0.52). CONCLUSIONS: IKKbeta regulates gastric carcinogenesis via IL-1alpha expression, which is associated with anti-apoptotic signaling and cell proliferation.

[A case of advanced gastric cancer with peritoneal dissemination effectively treated by combined chemotherapy of paclitaxel (TXL) and TS-1].

The patient was a 49-year-old woman. Chemotherapy was conducted combining paclitaxel (TXL) and TS-1 under the diagnosis of non-resectable advanced gastric cancer with peritoneal dissemination. The administration schedule was as follows: 60 mg/m2 of TXL on days 1, 8 and 15 intravenously and 120 mg/day of TS-1/on days 1 5, 8-12, and 15-19 orally. One cycle lasted for 5 weeks. Grade 1 peripheral neuropathy was noted, but no other serious adverse reaction occurred. Ascites fluid was reduced after completion of the 1st cycle, and the therapeutic efficacy was rated as PR. Abdominal fullness was relieved shortly after starting the treatment, making it possible to conduct treatment on an ambulatory basis in the 2nd and subsequent cycles. At present, 6 months after starting chemotherapy, there is no evidence of relapse or adverse reactions that require intervention. Chemotherapy is being continued on an ambulatory basis. Combination of TXL and TS-1 is expected to show good therapeutic efficacy and improve patients' QOL in patients with gastric cancer associated with peritoneal dissemination.

Risk factors for esophageal variceal bleeding in patients with hepatocellular carcinoma.

BACKGROUND/AIMS: To evaluate the risk factors for esophageal variceal bleeding in patients with hepatocellular carcinoma. METHODOLOGY: 103 patients with esophageal varices and hepatocellular carcinoma without previous history of varices bleeding or treatment of varices were followed up and the risk factors for variceal bleeding were evaluated by Cox proportional hazards regression. RESULTS: During an average of 650 days' follow-up, 17 patients (17%) suffered from variceal bleeding, showing an annual incidence rate of 9.3%. Another 8 patients (8%) underwent endoscopic variceal ligation for the aggravation of esophageal varices. Multivariate analysis showed that the red color sign of varices and the size of tumor (> or = 33 mm) were independently associated with an increased risk of variceal bleeding (Risk Ratio = 20.33, P < 0.0001 and Risk Ratio = 2.64, P = 0.0231, respectively). CONCLUSIONS: The large size of tumor, as well as the red color sign of varices, was a significant risk factor for variceal bleeding in patients with hepatocellular carcinoma.

Regulation of the expression of the liver cancer susceptibility gene MICA by microRNAs.

Hepatocellular carcinoma (HCC) is a threat to public health worldwide. We previously identified the association of a single nucleotide polymorphism (SNP) at the promoter region of the MHC class I polypeptide-related sequence A (MICA) gene with the risk of hepatitis-virus-related HCC. Because this SNP affects MICA expression levels, regulating MICA expression levels may be important in the prevention of HCC. We herein show that the microRNA (miR) 25-93-106b cluster can modulate MICA levels in HCC cells. Overexpression of the miR 25-93-106b cluster significantly suppressed MICA expression. Conversely, silencing of this miR cluster enhanced MICA expression in cells that express substantial amounts of MICA. The changes in MICA expression levels by the miR25-93-106b cluster were biologically significant in an NKG2D-binding assay and an in vivo cell-killing model. These data suggest that the modulation of MICA expression levels by miRNAs may be a useful method to regulate HCCs during hepatitis viral infection.

The flavonoid apigenin improves glucose tolerance through inhibition of microRNA maturation in miRNA103 transgenic mice.

Polyphenols are representative bioactive substances with diverse biological effects. Here, we show that apigenin, a flavonoid, has suppressive effects on microRNA (miRNA) function. The effects were mediated by impaired maturation of a subset of miRNAs, probably through inhibition of the phosphorylation of TRBP, a component of miRNA-generating complexes via impaired mitogen-activated protein kinase (MAPK) Erk activation. While glucose intolerance was observed in miRNA103 (miR103)-overexpressing transgenic mice, administration of apigenin improved this pathogenic status likely through suppression of matured miR103 expression levels. These results suggest that apigenin may have favorable effects on the pathogenic status induced by overexpression of miRNA103, whose maturation is mediated by phosphorylated TRBP.

Interleukin-6 mediates epithelial-stromal interactions and promotes gastric tumorigenesis.

Interleukin-6 (IL-6) is a pleiotropic cytokine that affects various functions, including tumor development. Although the importance of IL-6 in gastric cancer has been documented in experimental and clinical studies, the mechanism by which IL-6 promotes gastric cancer remains unclear. In this study, we investigated the role of IL-6 in the epithelial-stromal interaction in gastric tumorigenesis. Immunohistochemical analysis of human gastritis, gastric adenoma, and gastric cancer tissues revealed that IL-6 was frequently detected in the stroma. IL-6-positive cells in the stroma showed positive staining for the fibroblast marker α-smooth muscle actin, suggesting that stromal fibroblasts produce IL-6. We compared IL-6 knockout (IL-6(-/-)) mice with wild-type (WT) mice in a model of gastric tumorigenesis induced by the chemical carcinogen N-methyl-N-nitrosourea. The stromal fibroblasts expressed IL-6 in tumors from WT mice. Gastric tumorigenesis was attenuated in IL-6(-/-) mice, compared with WT mice. Impaired tumor development in IL-6(-/-) mice was correlated with the decreased activation of STAT3, a factor associated with gastric cancer cell proliferation. In vitro, when gastric cancer cell line was co-cultured with primary human gastric fibroblast, STAT3-related genes including COX-2 and iNOS were induced in gastric cancer cells and this response was attenuated with neutralizing anti-IL-6 receptor antibody. IL-6 production from fibroblasts was increased when fibroblasts were cultured in the presence of gastric cancer cell-conditioned media. IL-6 production from fibroblasts was suppressed by an interleukin-1 (IL-1) receptor antagonist and siRNA inhibition of IL-1α in the fibroblasts. IL-1α mRNA and protein were increased in fibroblast lysate, suggesting that cell-associated IL-1α in fibroblasts may be involved. Our results suggest the importance of IL-6 mediated stromal-epithelial cell interaction in gastric tumorigenesis.

Risk factors and early signs of pancreatic cancer in diabetes: screening strategy based on diabetes onset age.

BACKGROUND: Diabetes mellitus (DM) has long been recognized as a risk factor for pancreatic cancer (PaC) and recently has attracted attention as a manifestation of PaC. Diabetes is expected to be a clue for the early detection of PaC; however, no effective screening strategy has been established. METHODS: Forty diabetic patients with PaC were identified and compared with 120 diabetic patients without any malignancies. We analyzed risk factors for and early signs of PaC, focusing on the DM-onset age. RESULTS: As there were peaks at 40-45 years and 60-65 years in the distribution of DM-onset age, we analyzed the clinical characteristics of and risk factors for PaC according to DM-onset age: i.e., early-onset (< 55 years) and late-onset (≥ 55 years). PaC was diagnosed within 2 years of DM onset (new-onset) in 0% of the patients with early-onset DM, and in 33% of those with late-onset DM. The mean duration of DM in patients with early-onset DM with PaC was longer than that in the late-onset patients (26 vs. 9 years; P < 0.01). A family history of DM (odds ratio [OR] 3.60) and use of insulin (OR 3.52) were significant risk factors in patients with early-onset DM, while the onset age of DM (OR 1.12) and multiple diabetic patients in the family (OR 6.13) were risk factors in those with late-onset DM. Body weight loss and exacerbation of DM were seen 12 months prior to PaC diagnosis in both groups. CONCLUSIONS: Our study revealed specific risk factors for and similar early signs of PaC in early-onset and late-onset DM. Thus, we could develop a screening strategy, combining these risk factors specific for DM-onset age with early signs of disease.

Non-bismuth quadruple therapy for first-line Helicobacter pylori eradication: A randomized study in Japan.

AIM: To find the way to improve the eradication rate of first-line therapy in Japanese patients. METHODS: We prospectively compared the effectiveness of 7-d quadruple therapy to standard 7 d triple therapy in Japanese patients infected with Helicobacter pylori (H. pylori). One hundred and nineteen patients were randomly assigned to receive 7-d non-bismuth quadruple therapy with lansoprazole, amoxicillin, clarithromycin and metronidazole (LACM7) or 7-d triple therapy with lansoprazole, amoxicillin and clarithromycin (LAC7). After three months, H. pylori status was analyzed by (13)C-urea breath test. Incidence rates of adverse events were evaluated by use of questionnaires. RESULTS: By intention-to-treat (ITT) analysis, the eradication rate in the LACM7 group was 94.9%, which was significantly higher than the LAC7 group (68.3%, P < 0.001). Per protocol analysis also showed a significantly higher eradication rate in the LACM7 group (98.3%) than the LAC7 group (73.2%, P < 0.001). Nevertheless, the incidence of serious adverse events did not differ between the two groups (RR: 1.10, 95% CI: 0.70-1.73, P = 0.67). CONCLUSION: Seven day non-bismuth quadruple therapy (LACM7) was superior to standard 7-d triple therapy (LAC7) for first-line eradication.

Sitafloxacin resistance in Helicobacter pylori isolates and sitafloxacin-based triple therapy as a third-line regimen in Japan.

The third-line treatment regimen for Helicobacter pylori after failure of clarithromycin- and metronidazole-based therapies is not yet established. Sitafloxacin (STX) is a quinolone that possesses potent in vitro activity against H. pylori. In this study, the susceptibility of H. pylori isolates to STX was examined and the efficacy of STX-based triple therapy as a third-line regimen was evaluated. STX showed minimum inhibitory concentrations (MICs) of ≤1 µg/mL against all 100 H. pylori isolates, and the MIC(90) (MIC for 90% of the organisms) of STX was 5 log(2) dilutions lower than that of levofloxacin (LVX). The MIC(50) (MIC for 50% of the organisms) of STX against gyrA mutants was 0.12 µg/mL and was significantly lower than that of LVX (8 µg/mL). The activity of STX at pH 5.5 was significantly less than that at pH 7.0. In the clinical trial, 28 patients with two eradication failures were treated with STX-based triple therapy [rabeprazole 10 mg twice daily (b.i.d.), amoxicillin 750 mg b.i.d. and STX 100mg b.i.d. for 7 days]. The eradication rate was 75% using intention-to-treat analysis and 80% using per-protocol analysis. Two gyrA mutant strains were eradicated. Amongst participants, a low pepsinogen I/II ratio was associated with successful eradication. These results suggest that STX could be active against most clinical H. pylori isolates and that STX-based triple therapy is a promising and safe third-line therapy.

Colon cancer-derived factors activate NF-κB in myeloid cells via TLR2 to link inflammation and tumorigenesis.

The exact mechanism for the contribution of NF-κB activation during colon carcinogenesis is unclear. The present study aimed to determine the manner in which colon cancer cells induce inflammatory responses in order to link tumor growth. Macrophages were stimulated with cultured medium from the supernatants of several colon cancer cell lines. Macrophage accumulation and NF-κB activation were observed in samples that were stimulated with supernatant from tumor cells that showed constitutive NF-κB activity. NF-κB activation in the stimulated macrophages was dependent on TLR2 and IKKß, but not TLR4. Various cytokines, such as IL-6, were induced in a TLR2-dependent manner. Tumor cells that were cultured with the supernatant of macrophages originally stimulated with the tumor cell cultured media grew more rapidly than those stimulated with the supernatant of unstimulated macrophages. Taken together, colon cancer-derived factors induce the accumulation of macrophages and activate NF-κB through a TLR2-dependent mechanism, suggesting an important link between inflammation and tumor growth.

MicroRNA122 is a key regulator of α-fetoprotein expression and influences the aggressiveness of hepatocellular carcinoma.

α-fetoprotein (AFP) is not only a widely used biomarker in hepatocellular carcinoma (HCC) surveillance, but is also clinically recognized as linked with aggressive tumour behaviour. Here we show that deregulation of microRNA122, a liver-specific microRNA, is a cause of both AFP elevation and a more biologically aggressive phenotype in HCC. We identify CUX1, a direct target of microRNA122, as a common central mediator of these two effects. Using liver tissues from transgenic mice in which microRNA122 is functionally silenced, an orthotopic xenograft tumour model, and human clinical samples, we further demonstrate that a microRNA122/CUX1/microRNA214/ZBTB20 pathway regulates AFP expression. We also show that the microRNA122/CUX1/RhoA pathway regulates the aggressive characteristics of tumours. We conclude that microRNA122 and associated signalling proteins may represent viable therapeutic targets, and that serum AFP levels in HCC patients may be a surrogate marker for deregulated intracellular microRNA122 signalling pathways in HCC tissues.

Helicobacter pylori activates the proto-oncogene c-fos through SRE transactivation.

Epidemiological studies have demonstrated a strong association between Helicobacter pylori infection and gastric cancer. However, there have been few detailed studies on the mechanism of cellular proliferation by H. pylori. Thus, we examined activation of the proto-oncogene c-fos to elucidate the underlying mechanism of cell proliferation caused by H. pylori. Activation of c-fos was evaluated in human gastric cancer cells (TMK1) by Northern blot and reporter assays with deletion analysis of the c-fos transcriptional control region. c-fos promoter activation and transcription were enhanced when cocultured with cag-positive strains. H. pylori-mediated c-fos promoter activation was inhibited by MEK1/2 inhibitor (U0126). The deletion analysis indicated that serum response element (SRE) was required for the activation of c-fos by H. pylori. In conclusion, c-fos promoter activation and transcription were enhanced through the activation of extracellular signal-regulated kinases (ERK)/mitogen-activated protein kinase (MAPK) cascade in gastric cancer cells when cocultured with H. pylori possessing intact cag PAI. SRE is required for the activation of c-fos by H. pylori. These results suggest a direct involvement of H. pylori infection in cellular proliferation, which may play a role in neoplastic transformation.

Helicobacter pylori induces antiapoptosis through buclear factor-kappaB activation.

Although Helicobacter pylori is classified as a definite carcinogen, the mechanism underlying gastric carcinogenesis is not yet clear. We previously have shown that H. pylori activates an antiapoptotic gene, the cellular inhibitor of apoptosis protein 2 (c-IAP2), the underlying mechanism of which was investigated in the present study. cDNA array and real-time PCR analyses indicated that H. pylori showed a stimulatory effect on the expression of c-IAP2. Isogenic mutant strains with impaired cag pathogenicity island (cagPAI) expression showed weaker induction. Analyses that used the in situ terminal deoxynucleotide transferase-mediated dUTP nick end-labeling method indicated suppression of antiapoptosis by the antisense c-IAP2 oligonucleotide. Reporter assays with deletion and mutation constructs for the c-IAP2 promoter showed that nuclear factor-kappaB (NF-kappaB) binding sites are indispensable for transactivation. Super-repressor IkappaBalpha or NF-kappaB inhibitor reduced c-IAP2 transactivation by H. pylori, and exogenous expression of c-IAP2 inhibited apoptosis seen with H. pylori. In conclusion, H. pylori induces antiapoptosis through c-IAP2 transactivation following cagPAI-dependent NF-kappaB activation. The interaction of these stimuli may play a role in gastric carcinogenesis.