Effect of Helicobacter pylori Eradication on Gastric Cancer Prevention: Updated Report From a Randomized Controlled Trial With 26.5 Years of Follow-up.

BACKGROUND & AIMS: Helicobacter pylori infection is considered as the most important risk factor in the pathogenesis of gastric cancer. This study aims to evaluate the long-term effects of H pylori eradication treatment on the incidence and mortality of gastric cancer among a high-risk population. METHODS: This prospective, randomized, placebo-controlled trial was conducted in a high-risk area in southern China in July 1994. A total of 1630 asymptomatic, H pylori-infected individuals were randomly assigned to receive standard triple therapy for H pylori eradication (n = 817) or placebo (n = 813), and were followed up until December 2020. The primary outcome was incidence of gastric cancer. Total and cause-specific mortalities were the secondary outcomes. RESULTS: During 26.5 years of follow-up, 21 participants (2.57%) in the treatment arm and 35 (4.31%) in the placebo arm were diagnosed with gastric cancer. Participants receiving H pylori treatment had a lower incidence of gastric cancer compared with their placebo counterparts (hazard ratio [HR], 0.57; 95% CI, 0.33-0.98). More obvious risk reduction was observed among those without premalignant gastric lesions (HR, 0.37; 95% CI, 0.15-0.95) and those without dyspepsia symptoms at baseline (HR, 0.44; 95% CI, 0.21-0.94). Furthermore, compared with 32 cases of gastric cancer observed among 527 participants with persistent H pylori infection in the placebo group, only 16 were identified in 625 subjects with successful eradication in the treatment group (HR, 0.46; 95% CI, 0.26-0.83). However, there were no statistically significant differences for any mortality end points between the 2 groups. CONCLUSIONS: Eradication of H pylori might confer a long-term protection against gastric cancer in high-risk populations, especially for infected individuals without precancerous gastric lesions at baseline.

Role of PCDH10 and its hypermethylation in human gastric cancer.

Epigenetic changes of genomic DNA are involved in the development and progression of many cancers. Aberrant methylation of CpG islands in the promoter regions of certain tumor-suppressor genes (TSG) is frequently observed in cancer cells. Protocadherin 10 (PCDH10), a member of the cadherin superfamily, is a recently identified putative TSG. PCDH10 is frequently silenced in many solid tumors. However, the role of PCDH10 in gastric cancer is largely unknown. In this study, we examined the expression and methylation status of PCDH10 in gastric cancer cells and tissues by real time PCR and methylation-specific PCR (MSP), and then investigated the biological function of PCDH10. We found that the expression of PCDH10 was markedly reduced in gastric cancer cells and tissues. The reduced expression correlated with hypermethylation of this gene in its promoter region, as demonstrated by MSP and bisulfite genomic sequencing (BGS) analysis. In addition, pharmacological demethylation using 5-Aza restored the expression of PCDH10 in gastric cancer cells. Over-expression of PCDH10 in gastric cancer cells suppressed cell proliferation and migration, but did not cause marked apoptosis. Over-expression of PCDH10 also suppressed growth of xenograft tumors in nude mice. Thus, PCDH10 functions as a TSG in gastric cancer, and might be a useful target for cancer therapy.

Effects of selective COX-2 inhibitor and Helicobacter pylori eradication on precancerous gastric lesions.

OBJECTIVE: Helicobacter pylori infection and overexpression of cyclo-oxygenase-2 (COX-2) are associated with gastric cancer and its precursors. To evaluate the effect of a selective COX-2 inhibitor alone and combined with H pylori eradication on the evolution of precancerous gastric lesions, a randomised, placebo-controlled trial was conducted in Linqu County, Shandong Province, China. METHODS: A total of 1024 participants aged 35-64 years with H pylori infection and advanced gastric lesions were randomly assigned in a factorial design to two interventions or placebo: anti-H pylori treatment for 7 days, and a COX-2 inhibitor (celecoxib) for 24 months. The effects of the interventions were evaluated by the regression or progression of advanced gastric lesions. RESULTS: Of the 1024 participants who received anti-H pylori treatment or placebo, 919 completed a subsequent 24-month treatment with celecoxib or placebo. The H pylori eradication rate by per-protocol analysis was 78.2%. Compared with placebo, the proportions of regression of gastric lesions significantly increased in the celecoxib treatment (52.8% vs 41.2%) and anti-H pylori treatment (59.3% vs 41.2%) group, and OR by per-protocol analysis was 1.72 (95% CI 1.07 to 2.76) for celecoxib and 2.19 (95% CI 1.32 to 3.64) for H pylori eradication. No statistically significant effect was found for H pylori eradication followed by celecoxib on the regression of advanced gastric lesions (OR 1.48, 95% CI 0.91 to 2.40). CONCLUSION: This population-based intervention trial revealed that celecoxib treatment or H pylori eradication alone had beneficial effects on the regression of advanced gastric lesions. No favourable effects were seen for H pylori eradication followed by celecoxib treatment. Trial registration HARECCTR0500053 in accordance with WHO ICTRP requirements.

Esomeprazole compared with famotidine in the prevention of upper gastrointestinal bleeding in patients with acute coronary syndrome or myocardial infarction.

OBJECTIVES: Little is known about the efficacy of proton pump inhibitors compared with H(2) receptor antagonists in preventing adverse upper gastrointestinal complications in patients with acute coronary syndrome (ACS) or ST elevation myocardial infarction (STEMI) receiving aspirin, clopidogrel, and enoxaparin or thrombolytics. The objective of this study was to compare the efficacies of esomeprazole and famotidine in preventing gastrointestinal complications. METHODS: A double-blind, randomized, controlled trial was performed in patients receiving a combination of aspirin, clopidogrel, and either enoxaparin or thrombolytics. Patients received either esomeprazole (20 mg nocte) or famotidine (40 mg nocte) orally for 4-52 weeks, depending on the duration of dual antiplatelet therapy. The primary end point was upper gastrointestinal bleeding (GIB), perforation, or obstruction from ulcer/erosion (http://www.clinicaltrials.gov NCT00683111). RESULTS: In all, 311 patients were recruited, with 163 and 148 patients in the esomeprazole and famotidine groups, respectively. Mean (s.d.) follow-up was 19.2 (17.6) and 17.6 (18.0) weeks, respectively. One (0.6%) patient in the esomeprazole group and 9 (6.1%) in the famotidine group reached the primary end point (log-rank test, P=0.0052, hazard ratio=0.095, 95% confidence interval: 0.005-0.504); all had upper GIB. CONCLUSIONS: In patients with ACS or STEMI, esomeprazole is superior to famotidine in preventing upper gastrointestinal complications related to aspirin, clopidogrel, and enoxaparin or thrombolytics.

XIAP-associated factor 1 (XAF1), a novel target of p53, enhances p53-mediated apoptosis via post-translational modification.

The role of X chromosome-linked inhibitor of apoptosis protein (XIAP)-associated factor 1 (XAF1) in mediating apoptosis has been reported but the underlying mechanism remains unclear. The present study was designed to examine the putative interaction between XAF1 and p53 and the functional importance of this interaction in regulation of apoptosis in human gastric and colon cancer cells. We first identified XAF1 as a novel target gene of p53 by the chromatin immunoprecipitation (CHIP) assay and demonstrated that wild-type p53, but not mutant p53, down-regulated XAF1 at both mRNA and protein levels, which acted mostly under the condition of high expression of XAF1 and was associated with the physical interaction between p53 and the XAF1 promoter. We also found that the over-expression of XAF1 led to activation of wild-type p53 via post-translational modification in cells with or without DNA damage, which resulting in p53 nuclear accumulation and its increased transcriptional activity and enhancing p53-dependent apoptosis. These findings suggest that a potential novel feedback loop exists between XAF1 and wild-type p53.

Asian consensus report on functional dyspepsia.

BACKGROUND AND AIM: Environmental factors such as food, lifestyle and prevalence of Helicobacter pylori infection are widely different in Asian countries compared with the West, and physiological functions and genetic factors of Asians may also be different from those of Westerners. Establishing an Asian consensus for functional dyspepsia is crucial in order to attract attention to such data from Asian countries, to articulate the experience and views of Asian experts, and to provide a relevant guide on management of functional dyspepsia for primary care physicians working in Asia. METHODS: Consensus team members were selected from Asian experts and consensus development was carried out by using a modified Delphi method. Consensus teams collected published papers on functional dyspepsia especially from Asia and developed candidate consensus statements based on the generated clinical questions. At the first face-to-face meeting, each statement was reviewed and e-mail voting was done twice. At the second face-to-face meeting, final voting on each statement was done using a keypad voting system. A grade of evidence and strength of recommendation were applied to each statement according to the method of the GRADE Working Group. RESULTS: Twenty-nine consensus statements were finalized, including seven for definition and diagnosis, five for epidemiology, nine for pathophysiology, and eight for management. Algorithms for diagnosis and management of functional dyspepsia were added. CONCLUSIONS: This consensus developed by Asian experts shows distinctive features of functional dyspepsia in Asia and will provide a guide to the diagnosis and management of functional dyspepsia for Asian primary care physicians.

Famotidine is inferior to pantoprazole in preventing recurrence of aspirin-related peptic ulcers or erosions.

BACKGROUND & AIMS: Little is known about the efficacy of H(2)-receptor antagonists in preventing recurrence of aspirin-related peptic ulcers. We compared the efficacy of high-dose famotidine with that of pantoprazole in preventing recurrent symptomatic ulcers/erosions. METHODS: We performed a randomized, double-blind, controlled trial of 160 patients with aspirin-related peptic ulcers/erosions, with or without a history of bleeding. Patients were given either famotidine (40 mg, morning and evening) or pantoprazole (20 mg in the morning and placebo in the evening). All patients continued to receive aspirin (80 mg daily). The primary end point was recurrent dyspeptic or bleeding ulcers/erosions within 48 weeks. RESULTS: A total of 130 patients (81.1%) completed the study; 13 of 65 patients in the famotidine group reached the primary end point (20.0%; 95% one-sided confidence interval [CI] for the risk difference, 0.1184-1.0) compared with 0 of 65 patients in the pantoprazole group (P < .0001, 95% one-sided CI for the risk difference, 0.1184-1.0). Gastrointestinal bleeding was significantly more common in the famotidine group than the pantoprazole group (7.7% [5/65] vs 0% [0/65]; 95% one-sided CI for the risk difference, 0.0226-1.0; P = .0289), as was recurrent dyspepsia caused by ulcers/erosions (12.3% [8/65] vs 0% [0/65]; 95% one-sided CI for the risk difference, 0.0560-1.0; P = .0031). No patients had ulcer perforation or obstruction. CONCLUSIONS: In patients with aspirin-related peptic ulcers/erosions, high-dose famotidine therapy is inferior to pantoprazole in preventing recurrent dyspeptic or bleeding ulcers/erosions.

XIAP-associated factor 1 interacts with and attenuates the trans-activity of four and a Half LIM protein 2.

XIAP-associated factor 1(XAF1) is a tumor suppressor with its functional mechanisms not fully understood. The zinc-finger cluster located at the N-terminus is the only domain structure. Four and a half LIM domain protein 2 (FHL2) also contains a tandem zinc finger structure, and its protein functions as an important adaptor and modifier in protein-protein interactions. Both of their structures are relatively simple, while the association between them is still unclear. In this study, we detected the interaction between XAF1 and FHL2 by using the yeast two-hybrid system. We identified FHL2 as a XAF1 binding protein. Furthermore, both XAF1 and FHL2 localized to the cytoplasm, mitochondria, and nucleus of gastric cancer cells. Over-expression of XAF1 excluded FHL2 from the nucleus and suppressed the trans-activity of FHL2 in stimulating the transcriptional activities of ß-catenin and AP-1. In conclusion, our findings unraveled an antagonistic mechanism between a tumor suppressor and an oncoprotein in cancer cells.

Helicobacter pylori and gastritis: Untangling a complex relationship 27 years on.

Since its' introduction by Warren and Marshall 27 years ago, Helicobacter pylori (HP) has become the linchpin in our understanding of important gastric conditions including gastritis, intestinal metaplasia (IM), gastric/duodenal ulcers (GU/DU), Mucosal Associated Lymphoid Tumour (MALToma) and gastric cancer. Initially named Campylobacter pyloridis, it was re-named HP when biochemical and genetic characterization of the organism showed that it was not a member of the Campylobacter genus. The finding in 1983 was seminal. It is now recognized that HP is the most common chronic human bacterial infection and it is the most common cause of gastritis. It is strongly implicated in the development of peptic ulcer disease and gastric neoplasms. In the years since its' discovery, much headway has been made in the understanding of this ubiquitous organism that had remained elusive, with much work focused on eradication, in part driven by pharmaceutical research and development. Standard triple therapy emerged to eradicate HP. However, with the emergence of HP resistance, newer regimes have been put forth that include quadruple therapy, sequential therapy and a dizzying array of other combinations bent on eradicating HP. Much less is known about the natural history of HP, the different faces of HP internationally, HP eradication and its effect on gastritis, IM, GU/DU and gastric cancer. This review will address the changing face of HP in 2011.

Promoter hypermethylation and histone hypoacetylation contribute to pancreatic-duodenal homeobox 1 silencing in gastric cancer.

BACKGROUND AND AIMS: The expression of pancreatic-duodenal homeobox 1 (PDX1) in gastric cancer is aberrantly reduced. The aim of this study was to elucidate the regulation of DNA methylation and histone acetylation at the promoter for PDX1 silencing in gastric cancer. METHODS: PDX1 expression in response to demethylation and acetylation was detected in human gastric cancer cell lines by reverse transcription-polymerase chain reaction (PCR) and western blot. Four CpG islands within the 5'-flanking region of PDX1 gene were analyzed with their transcription activities being detected by dual luciferase assay. Promoter hypermethylation was identified in gastric cancer cell lines and cancer tissues by methylation-specific PCR or bisulfite DNA sequencing PCR analysis. Histone acetylation was determined by chromatin immunoprecipitation (ChIP) assay. RESULTS: Demethylation by 5'-aza-2'-deoxycytidine (5'-aza-dC) and/or acetylation by trichostatin A (TSA) restored PDX1 expression in gastric cancer cells. Hypermethylation was found in four CpG islands in six of seven cancer cell lines. However, only the distal CpG island located in the promoter fragment of PDX1, F383 (c.-2063 to -1681 nt upstream of the ATG start codon) displayed significant transcriptional activity that could be suppressed by SssI methylase and increased by 5'-aza-dC and TSA. More than 70% of the single CpG sites in F383 were methylated with hypermethylation of F383 fragment more common in gastric cancerous tissues compared with the paired normal tissues (P < 0.05). ChIP assay showed F383 was also associated with low hypoacetylation level of the histones. CONCLUSION: Promoter hypermethylation and histone hypoacetylation contribute to PDX1 silencing in gastric cancer.

Four-and-a-half LIM protein 2 promotes invasive potential and epithelial-mesenchymal transition in colon cancer.

BACKGROUND AND AIMS: Cancer invasion and metastasis may associate with the phenotype transition called epithelial-mesenchymal transition (EMT). We aim to evaluate the impact of four-and-a-half LIM protein 2 (FHL2) on EMT and invasion of colon cancer. METHODS: The functional role of FHL2 in EMT was determined by overexpression or small interfering RNA-mediated depletion of FHL2. Mechanisms of FHL2 on expression or activity of E-cadherin and beta-catenin were assessed. RESULTS: FHL2 was highly expressed in primary and metastatic colon cancer but not in normal tissues. FHL2 was critical for cancer cell adhesion to extracellular matrix, migration and invasion. FHL2 expression was stimulated by transforming growth factor (TGF)-beta1. Moreover, FHL2 acted as a potent EMT inducer by stimulating vimentin and matrix metalloproteinase-9 expressions and causing a loss of E-cadherin, whereas those alterations of EMT markers were not affected by silencing of Smad molecules (typical TGF-beta signal mediators) in FHL2 stable transfectant cells. Therefore, FHL2 induced EMT in a TGF-beta-dependent and Smad-independent manner. FHL2 downregulated E-cadherin expression and inhibited the formation of membrane-associated E-cadherin-beta-catenin complex. FHL2 also stabilized nuclear beta-catenin, resulting in enforcement of beta-catenin transactivation activity. CONCLUSION: FHL2 is a potent EMT inducer and might be an important mediator for invasion and/or metastasis of colon cancer.

Rabeprazole is effective in treating laryngopharyngeal reflux in a randomized placebo-controlled trial.

BACKGROUND & AIMS: There is controversy about the efficacy of treating patients with laryngopharyngeal reflux (LPR) using proton pump inhibitors (PPIs). We assessed the effects of high doses of the PPI rabeprazole in patients with LPR. METHODS: Patients with LPR symptoms were assigned randomly to receive rabeprazole (20 mg, twice daily, n = 42) or placebo (n = 40) for 12 weeks. All patients completed symptom questionnaires; these provided demographic information and the reflux symptom index before, during, and 6 weeks after cessation of treatment. Videolaryngostroboscopy was used to document the laryngeal findings and determine the reflux finding score. RESULTS: Twenty-four patients (57.1%) in the rabeprazole group and 27 patients (67.5%) in the placebo group had pH-documented LPR. The total reflux symptom index score decreased significantly in the group given rabeprazole, compared with patients given placebo, at weeks 6 and 12, but not at week 18. However, there were no significant differences in reflux finding scores between the rabeprazole and placebo groups at any of the time points. CONCLUSIONS: Twelve weeks of treatment with rabeprazole (20 mg, twice daily) significantly improved reflux symptoms, compared with placebo, in patients with LPR. Relapse of symptoms was observed 6 weeks after stopping PPI therapy, indicating the requirement for longer treatment duration in patients with LPR.

Essential role for macrophage migration inhibitory factor in gastritis induced by Helicobacter pylori.

Macrophage migration inhibitory factor (MIF) is an upstream regulator of immune and inflammatory responses; however, its role in Helicobacter pylori (HP)-associated gastritis remains unknown. We infected MIF knockout (KO) and wild-type mice with SS1 HP and found that 2 weeks after infection, MIF and its receptor CD74 were markedly up-regulated in wild-type mice. This up-regulation preceded the up-regulation of both tumor necrosis factor-alpha and intercellular adhesion molecule-1, as well as the development of moderate gastritis at 8 weeks, as determined by a significant infiltration of neutrophils, T cells, and macrophages. In contrast, KO mice were protected against HP-induced gastritis by preventing the up-regulation of CD74 and Th1-mediated immune injury, including a reduction in the Th1 transcriptional factor T-bet and the expression of interferon-gamma. Additionally, inhibition of skin delayed type hypersensitivity reactions to HP antigens in KO mice also suggested a critical role for MIF in cell-mediated injury. A regulatory role for MIF in Th1-immune responses was further demonstrated by the finding that antigen-primed CD4(+) T cells lacking MIF failed to differentiate into the Th1 phenotype; these cells were instead promoted to Th2 differentiation after challenge with HP antigen in vitro. Results from this study indicated that inhibition of HP-induced innate immune responses and Th1-mediated immune injury may be the key mechanisms by which KO mice failed to develop gastritis after HP infection.

Twelve-month endoscopic and histological analysis following proton-pump inhibitor-based triple therapy in Helicobacter pylori-positive patients with gastric ulcers.

OBJECTIVE: To evaluate endoscopic and histological findings after Helicobacter pylori eradication therapy in gastric ulcer (GU) patients after 12 months' follow-up. MATERIAL AND METHODS: A total of 401 GU patients were randomized to receive either twice-daily (b.i.d.) esomeprazole 20 mg+amoxicillin 1000 mg+clarithromycin 500 mg (EAC) for 1 week followed by placebo for 3 weeks, EAC followed by once-daily (o.d.) esomeprazole 20 mg for 3 weeks or esomeprazole 20 mg b.i.d. plus placebo antibiotics for 1 week followed by esomeprazole 20 mg o.d. for 3 weeks. Endoscopy with biopsy was performed at baseline, after treatment and at 6 and 12 months' follow-up (healed patients). RESULTS: Endoscopic abnormalities, particularly in the stomach, were common at baseline and remained similar during follow-up, regardless of ulcer status and treatment. Helicobacter gastritis was present (antrum or corpus) in approximately 20% of patients following eradication therapy (versus approximately 80% with esomeprazole alone); these effects were sustained during follow-up. Similar trends were observed for other histological variables (granulocyte and lymphoplasmocytic cell infiltration, replacement of gastric surface cells by regenerative epithelium, and mucous depletion). No changes in atrophy or intestinal metaplasia were observed. Eighteen gastric cancer cases were detected: 11 at baseline endoscopy, and seven during treatment and follow-up. CONCLUSIONS: Endoscopic abnormalities are common in GU patients and persist after proton-pump inhibitor-based triple therapy for H. pylori eradication, which is associated with large, sustained improvements in histological variables. Follow-up endoscopy and histology may be necessary, even in patients with apparently non-malignant GU, to improve the detection rate of gastric malignancy in populations with a high prevalence of gastric cancer.

Proton pump inhibitor and clopidogrel interaction: the case for watchful waiting.

Clopidogrel is an integral part of the management of several important vascular diseases. However the medium to long term clinical outcomes are poorer for these patients if they experience gastro-intestinal bleeding, hence patients with risk factors for gastro-intestinal bleeding are frequently prescribed proton pump inhibitors. Conflicting evidence exists as to the existence of an adverse interaction between clopidogrel and proton pump. This review examines the original studies, which suggested the adverse interaction, the subsequent and most recent studies, the pharmaco-dynamics of the two drugs and suggests an algorithm for the use of clopidogrel with proton pump inhibitors.

Trend of colorectal cancer in Hong Kong: 1983-2006.

BACKGROUND AND AIM: The incidence of colorectal cancer (CC) is increasing in many Asian countries, but decreasing in western countries. The present study examined the local incidence of CC in the past few decades. METHODS: A population based study, using data from Hong Kong (HK) Cancer Registry, was carried out to examine the trends of CC in different age groups in HK. Comparison with other countries was made. RESULTS: The crude rate of CC in HK increased from 29.6/100,000 in 1983 to 57.1/100,000 in 2006. Age standardized rate (ASR) increased by less than 20%. It was markedly smaller than the 190% increase in crude rate. ASR progressively increased in males. In females, ASR peaked in 1994 and declined in the last decade. In most countries, the risk of CC was higher and increasing in males, but stable or decreasing in females. With respect to age, increasing risk was noted in males above 60 years old and females above 70 years old. However, a declining rate was noted in those below 50 years old. The decrease was over 40% in the 30-34 years group over the past two decades. CONCLUSIONS: Increasing incidence of CC in HK was mostly in the older and male population, but not in the younger age group.

Targeting apoptosis as an approach for gastrointestinal cancer therapy.

Cancers in the gastrointestinal system account for a large proportion of malignancies and cancer-related deaths with gastric cancer and colorectal cancer being the most common ones. For those patients in whom surgical resection is not possible, other therapeutic approaches are necessary. Disordered apoptosis has been linked to cancer development and treatment resistance. Apoptosis occurs via extrinsic or intrinsic signaling each triggered and regulated by many different molecular pathways. In recent years, the selective induction of apoptosis in tumor cells has been increasingly recognized as a promising approach for cancer therapy. A detailed understanding of the molecular pathways involved in the regulation of apoptosis is essential for developing novel effective therapeutic approaches. Apoptosis can be induced by many different approaches including activating cell surface death receptors (for example, Fas, TRAIL and TNF receptors), inhibiting cell survival signaling (such as EGFR, MAPK and PI3K), altering apoptosis threshold by modulating pro-apoptotic and anti-apoptotic members of the Bcl-2 family, down-regulating anti-apoptosis proteins (such as XIAP, survivin and c-IAP2), and using other pro-apoptotic agents. In this review, the authors reviewed the currently reported apoptosis-targeting approaches in gastrointestinal cancers.

Role of Notch signaling in colorectal cancer.

Notch signaling is an important molecular pathway involved in the determination of cell fate. In recent years, this signaling has been frequently reported to play a critical role in maintaining progenitor/stem cell population as well as a balance between cell proliferation, differentiation and apoptosis. Thus, Notch signaling may be mechanistically involved carcinogenesis. Indeed, many studies have showed that Notch signaling is overexpressed or constitutively activated in many cancers including colorectal cancer (CRC). Consequently, inactivation of Notch signaling may constitute a novel molecular therapy for cancer. CRC is one of the most common malignancies but the current therapeutic approaches for advanced CRC are less efficient. Thus, novel therapeutic approaches are badly needed. In this review article, the authors reviewed the current understanding and research findings of the role of Notch signaling in CRC and discussed the possible Notch-targeting approaches in CRC.

c-Jun N-terminal kinase (JNK1) upregulates XIAP-associated factor 1 (XAF1) through interferon regulatory factor 1 (IRF-1) in gastrointestinal cancer.

BACKGROUND AND AIMS: X-linked inhibitor of apoptosis protein-associated factor 1 (XAF1) is a tumor suppressor that can sensitize cancer cell to apoptosis. Intrinsic expression of XAF1 in cancer cell is low. Our purpose is to determine the effect of c-Jun N-terminal kinase 1 (JNK1) on XAF1 expression and the putative mechanism. METHODS: XAF1 expression in gastrointestinal (GI) cancer cell line AGS and SW1116 was detected by reverse transcription-polymerase chain reaction (PCR), real-time PCR and immunoblotting. The role of JNK1 was assessed by ectopic overexpression with wild-type (JNK1-WT) and dominant-negative (JNK1-DN) JNK1 constructs. The effects of JNK1 activator, interferon (IFN)-alpha, tumor necrosis factor (TNF)-alpha and phorbol-12-myristate-13-acetate (PMA), or JNK1 inhibitor, SP600125, were evaluated. An XAF1 promoter reporter pLUC107 with WT or mutated interferon regulatory factor 1-binding element (IRF-E) was used to assess JNK1-induced transcription by dual luciferase assay. RESULT: Ectopic overexpression of JNK1-WT or treatment with IFN-alpha, TNF-alpha and PMA induced whereas SP600125 suppressed intrinsic and induced XAF1 expression. Induction of XAF1 required de novo protein synthesis. Moreover, JNK1 stimulated whereas SP600125 suppressed XAF1 promoter activity. JNK1 stimulated interferon regulatory factor 1 (IRF-1) expression, whereas both IRF-1 small-interfering RNA and site mutation of IRF-E within XAF1 promoter abrogated the effect of JNK1. CONCLUSION: JNK1 stimulated and mediated the effects of IFN and TNF-alpha on XAF1 expression through transcriptional regulation by induction of IRF-1. The linkage of JNK1, IRF-1 and XAF1 in the same signal pathway may unravel a novel mechanism in regulation of apoptosis and differentiation of GI cancers.

Identification of XAF1 as a novel cell cycle regulator through modulating G(2)/M checkpoint and interaction with checkpoint kinase 1 in gastrointestinal cancer.

BACKGROUND AND AIMS: X-linked inhibitor of apoptosis-associated factor 1 (XAF1) was first recognized as an antagonist of X-linked inhibitor of apoptosis in suppressing caspase 3 activity. It has lower expression in cancer cells than normal tissue. Overexpression of XAF1 can inhibit cancer cell growth and sensitize tumor necrosis factor-related apoptosis-inducing ligand- or etoposide-induced apoptosis. The aim of this study is to elucidate the mechanism of XAF1 in regulating cell growth. METHODS: Stable transfectants of gastrointestinal (GI) cancer cell lines AGS and SW1116 expressing XAF1 and vector control were generated. Cell growth, apoptosis, mitotic status and cell cycle distribution were assessed. The interaction between XAF1 and G(2)/M checkpoint proteins was evaluated by immunoblotting, kinase assay and co-immunoprecipitation assay. Mitotic catastrophe was identified by occurrence of aberrant nuclei and centrosomal amplification. RESULTS: Our results showed that overexpression of XAF1 suppressed serum-dependent cancer cell growth, induced mitotic catastrophe and G(2)/M cell cycle arrest. Interestingly, XAF1 was predominantly expressed in G(2)/M phase after cell cycle synchronization. XAF1 interacted with and activated checkpoint kinase 1 (Chk1), inactivated Cdc25C and lead to inactivation of Cdc2-cyclin B complex. Suppression of Chk1 abrogated XAF1-induced G(2)/M arrest. CONCLUSIONS: Our findings implicate XAF1 as a novel cell cycle modulator that is recruited in G(2)/M phase and thus unravel a novel function pathway of XAF1, suggesting the potential role of XAF1 as the target for the management of GI cancers.