Stomach Carcinogenesis Research Articles

The ASH1L-AS1-ASH1L axis controls NME1-mediated activation of the RAS signaling in gastric cancer.

Gastric cancer (GC) is one of the most leading cause of malignancies. However, the molecular mechanisms underlying stomach carcinogenesis remain incompletely understood. Dysregulated genetic and epigenetic alternations significantly contribute to GC development. Here, we report that ASH1L and its antisense lncRNA ASH1L-AS1, which are transcribed from the most significant GC-risk signal at 1q22, act as novel oncogenes. The high levels of ASH1L or lncRNA ASH1L-AS1 expression in GC specimens are associated with worse prognosis of patients. In line with this, ASH1L and ASH1L-AS1 are functionally important in promoting GC disease progression. LncRNA ASH1L-AS1 up-regulates ASH1L transcription, increases histone methyltransferase ASH1L expression and elevates genome-wide H3K4me3 modification levels in GC cells. Furthermore, ASH1L-AS1 directly interacts with transcription factor NME1 protein to form the ASH1L-AS1-NME1 ribonucleoprotein, which transcriptionally promotes expression of ASH1L, ASH1L-AS1, KRAS and RAF1, and activates the RAS signaling pathway in GC cells. Taken together, our data demonstrated that the ASH1L-AS1-ASH1L regulatory axis controls histone modification reprogram and activation of the RAS signaling in cancers. Thus, ASH1L-AS1 might be a novel targets of GC therapeutics and diagnosis in the clinic.

CDC25B Inhibition by Menadione: A Potential New Therapeutical Approach

Gastric cancer (GC) is the fifth most common type of tumor and the third leading cause of cancer death worldwide. The evolution of gastric carcinogenesis is still poorly understood and, for this reason, preclinical research protocols were established that included the development of gastric cancer cell lines and the establishment of models of gastric carcinogenesis in non-human primates such as Sapajus apella. A comprehensive literature search was performed in relevant databases such as PubMed, ResearchGate, and Google Scholar to identify studies related to the topic. After an in-depth study of these reports, significant data were collected and compiled under appropriate headings. The main result of the studies carried out by the group on GC is the demonstration of the MYC gene overexpression as a common phenomenon in stomach carcinogenesis. Furthermore, we revealed that reducing the expression of the CDC25B gene, regulated by the MYC protein, is a therapeutic strategy against stomach tumors. This review article reveals preclinical evidence that treatment with menadione in experimental models of gastric tumorigenesis, in vivo and in vitro, inhibits the action of the phosphatase CDC25B and, consequently, prevents cell proliferation, invasion, and migration.

Abstract 5680: Hypoxia-responsive and HIF1α-regulated AAA+ ATPase ATAD2 shows high oncogenic potential in stomach cancer

Abstract The burden of stomach cancer incidence and death is a global challenge. Treating stomach cancer remains immensely difficult due to the lack of available markers to detect the disease at the early stages. Therefore, there is an immense demand for finding out an early detection biomarker for stomach cancer. Recently, ATAD2 is found to be overexpressed in stomach cancer with high prognostic significance and recognised as a promising biomarker for stomach cancer. ATAD2 is a unique cancer/testis antigen (CTA) that belongs to both AAA+ ATPase and bromodomain family proteins. However, nothing much is known about the mechanism of ATAD2-mediated stomach carcinogenesis. Using bioinformatics analyses as well as studies with stomach cancer cells and stomach biopsy tissue samples, we address the regulation and function of ATAD2 expression in stomach cancer. We show that ATAD2 is overexpressed in the most common intestinal type of stomach adenocarcinoma, and enhanced expression of ATAD2 is observed in all stages and grades of stomach cancer. Our immunofluorescence microscopy study with stomach biopsy tissues confirms the high expression of ATAD2 both in stomach adenocarcinoma and metastatic stomach tissue samples. Survival analysis indicates that upregulated ATAD2 expression drastically affects the survival of stomach cancer patients. Since H. pylori infection, and hypoxia are the major contributing factors for stomach carcinogenesis; we further study their role in ATAD2-mediated stomach malignancy. An enhanced expression of ATAD2 is observed in H. pylori-infected stomach cancer cells. We identify ATAD2 as a hypoxia-responsive and HIF1α-regulated gene and elucidate that upregulated expression of ATAD2 enhances proliferation and migration of hypoxic stomach cancer cells. We further recognize the protein-protein interaction (PPI) network of ATAD2 with the top-ranked partners like ESR1 (or ERα), NCOA3 (or ACTR/SRC3/AIB1), SUMO2, HDA11 (HDAC11), SPTN2 (SPTBN2), and MYC. Among them, ESR1, MYC, NCOA3, and HDA11 are oncoproteins. Most strikingly, we report the participation of two druggable targets of ATAD2, i.e., AAA+ ATPase and bromodomain in the ATAD2-PPI network; ESR1, SUMO2, SPTN2, and MYC show a preference for bromodomain, whereas NCOA3 and HDA11 prefer ATPase domain of ATAD2. The importance of such findings in terms of targeting bromodomain-PPI and/or ATPase-PPI interfaces to curtail stomach cancer is elucidated. Citation Format: Anasuya Roychowdhury, Aditi Nayak, Sugandh Kumar, Anshuman Dixit, Asima Bhattacharyya. Hypoxia-responsive and HIF1α-regulated AAA+ ATPase ATAD2 shows high oncogenic potential in stomach cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5680.

Convergent dysbiosis of gastric mucosa and fluid microbiome during stomach carcinogenesis

A complex microbiota in the gastric mucosa (GM) has been unveiled recently and its dysbiosis is identified to be associated with gastric cancer (GC). However, the microbial composition in gastric fluid (GF) and its correlation with GM during gastric carcinogenesis are unclear. We obtained GM and GF samples from 180 patients, including 61 superficial gastritis (SG), 55 intestinal metaplasia (IM) and 64 GC and performed 16S rRNA gene sequencing analysis. The concentration of gastric acid and metabolite nitrite has been measured. Overall, the composition of microbiome in GM was distinct from GF with less diversity, and both were influenced by H. pylori infection. The structure of microbiota changed differentially in GM and GF across histological stages of GC, accompanied with decreased gastric acid and increased carcinogenic nitrite. The classifiers of GC based on microbial markers were identified in both GM and GF, including Lactobacillus, Veillonella, Gemella, and were further validated in an independent cohort with good performance. Interestingly, paired comparison between GM and GF showed that their compositional distinction remarkably dwindled from SG to GC, with some GF-enriched bacteria significantly increased in GM. Moreover, stronger interaction network between microbes of GM and GF was observed in GC compared to SG. Our results, for the first time, revealed a comprehensive profile of both GM and GF microbiomes during the development of GC. The convergent microbial characteristics between GM and GF in GC suggest that the colonization of carcinogenic microbes in GM might derive from GF.

Chemopreventive effect of galangin against benzo(a)pyrene-induced stomach tumorigenesis through modulating aryl hydrocarbon receptor in Swiss albino mice.

The present study was aimed to evaluate the chemopreventive potential of galangin against benzo(a)pyrene (BaP)-induced stomach carcinogenesis in Swiss albino mice. Stomach cancer was induced in experimental mice using BaP oral administration. The mice were treated with galangin (10 mg/kg b.wt.) before and during BaP administration. Oral administration of galangin at a dose of 10 mg/kg b.wt. significantly (p < 0.05) prevented the tumor incidence, tumor volume in the experimental animals. Further, galangin pretreatment prevents BaP-induced lipid peroxidation and restores BaP-mediated loss of cellular antioxidants status. It has also been found that galangin prevents BaP-induced activation of phase I detoxification enzymes. Furthermore, galangin pretreatment prevented the BaP-induced overexpression of cytochrome P450s isoform genes (CYP1A1, CYP1B1), aryl hydrocarbon receptor system (AhR, ARNT), transcriptional activators (CBP/p300, NF-kB), tumor growth factors, proto-oncogenes, invasion markers (TGFB, SRC-1, MYC, iNOS, MMP2, MMP9) and Phase II metabolic isoenzyme genes (GST) in the stomach tissue homogenate when compared to the control groups. The western blot results confirm that galangin (10 mg/kg. b.wt.) treatment significantly prevented the BaP-mediated expression of ArR, ARNT, and CYP1A1 proteins in the mouse stomach tissue. Therefore, the present results confirm that galangin prevents BaP-induced stomach carcinogenesis probably through modulating ArR and ARNT expression in the experimental mice.

Oncogenic potential of ATAD2 in stomach cancer and insights into the protein-protein interactions at its AAA + ATPase domain and bromodomain

ATAD2 has recently been shown to promote stomach cancer. However, nothing is known about the functional network of ATAD2 in stomach carcinogenesis. This study illustrates the oncogenic potential of ATAD2 and the participation of its ATPase and bromodomain in stomach malignancy. Expression of ATAD2 in stomach cancer is analyzed by in silico and in vitro techniques including western blot and immunofluorescence microscopy of stomach cancer cells (SCCs) and tissues. The oncogenic potential of ATAD2 is examined thoroughly using genetic alterations, driver gene prediction, survival analysis, identification of interacting partners, and analysis of canonical pathways. To understand the protein-protein interactions (PPI) at residue level, molecular docking and molecular dynamics simulations (1200 ns) are performed. Enhanced expression of ATAD2 is observed in H. pylori-infected SCCs, patient biopsy tissues, and all stages and grades of stomach cancer. High expression of ATAD2 is found to be negatively correlated with the survival of stomach cancer patients. ATAD2 is a cancer driver gene with 37 mutational sites and a predictable factor for stomach cancer prognosis with high accuracy. The top canonical pathways of ATAD2 indicate its participation in stomach malignancy. The ATAD2-PPI in stomach cancer identify top-ranked partners; ESR1, SUMO2, SPTN2, and MYC show preference for the bromodomain whereas NCOA3 and HDA11 have preference for the ATPase domain of ATAD2. The oncogenic characterization of ATAD2 provides strong evidence to consider ATAD2 as a stomach cancer biomarker. These studies offer an insight for the first time into the ATAD2-PPI interface presenting a novel target for cancer therapeutics. Communicated by Ramaswamy H. Sarma

Hypergastrinemia is associated with an increased risk of gastric adenocarcinoma with proximal location: A prospective population-based nested case-control study.

The incidence of proximal gastric adenocarcinoma is increasing among younger adults. Rodent models have shown that hypergastrinemia causes carcinogenesis in the proximal stomach. The aim of our study was therefore to assess if hypergastrinemia was associated with an increased risk of developing gastric adenocarcinoma also in humans. A prospective population‐based nested case‐control study within the Nord‐Trøndelag Health Study (HUNT) cohort, Norway, was used to assess this association. Serum was collected from 78 962 participants in 1995 to 1997 and 2006 to 2008. In the cohort, 181 incident gastric adenocarcinoma cases were identified from the Norwegian Cancer and Patient Registries through 2015 and matched with 359 controls. The risk of gastric adenocarcinoma was compared between participants with prediagnostic hypergastrinemia (>60 pmol/L) and normal serum gastrin (≤60 pmol/L). Logistic regression provided odds ratios (ORs) with 95% confidence intervals (CIs), adjusted for body mass index, tobacco smoking and comorbidity. Hypergastrinemia was associated with increased risk of gastric adenocarcinoma overall (OR 2.2, 95% CI 1.4‐3.4) and in particular for gastric adenocarcinoma with proximal location (OR 6.1, 95% CI 2.7‐13.8), but not with gastric adenocarcinoma with distal location (OR 1.7, 95% CI 0.9‐3.4). Moreover, hypergastrinemia was associated with an increased risk of gastric adenocarcinoma of intestinal histological type (OR 3.8, 95% CI 1.8‐7.9), but not for diffuse histological type (OR 1.6, 95% CI 0.7‐3.7). In conclusion, hypergastrinemia was associated with an increased risk of proximal and intestinal type gastric adenocarcinoma.

HIF1α-dependent upregulation of ATAD2 promotes proliferation and migration of stomach cancer cells in response to hypoxia

Stomach cancer is a difficult-to-treat disease. Lack of detection markers and limited understanding of the disease mechanisms contribute to the aggressive nature of stomach cancer cells (SCCs). Recently, an ATPase, ATAD2 has been found to be highly expressed in stomach cancer contributing to increased malignancy. However, nothing is known about the mechanism of ATAD2 upregulation and its involvement in stomach carcinogenesis. Since hypoxic microenvironment plays a crucial role in the progression of solid tumors like stomach cancer; we have examined the regulation and function of ATAD2 expression in hypoxic SCCs. ATAD2 is induced in hypoxia-treated SCCs. Stomach adenocarcinoma and metastatic tissues with high HIF1α level also show enhanced ATAD2 expression. In the absence of hypoxia-inducible factor HIF1α, ATAD2 protein level is found to be less indicating towards a potential correlation between them. We identify the presence of HIF1α-binding site (HBS) and HIF1α ancillary site (HAS) in the ATAD2 promoter. Using both in vitro and in vivo binding studies, we confirm that HIF1α binds with the ATAD2 promoter in hypoxic condition. ATAD2 upregulation promotes proliferation and migration of SCCs exposed to hypoxia. Thus, we identify ATAD2 as a hypoxia-responsive and HIF1α-regulated gene and elucidate that upregulated expression of ATAD2 enhances tumor-promoting functions in hypoxic SCCs. Therefore, we propose ATAD2 as a promising therapeutic target for stomach cancer.

Assessing the progression of gastric cancer via profiling of histamine, histidine, and bile acids in gastric juice using LC-MS/MS

Bile acid (BA) imbalance may be directly associated with gastric cancer and indirectly influence stomach carcinogenesis via overexpression of histidine decarboxylase (HDC), which converts histidine (His) into histamine (HIST). Moreover, the progression of gastric cancer, could change the gut microbiome, including bacteria spp. that produce secondary BAs. Gastric juice has various metabolites that could indicate gastric cancer-related stomach conditions. Therefore, profiling of HIST, His, and BAs in gastric juice is crucial for understanding the etiological mechanisms of gastric cancer. We used a profiling method to simultaneously determine targeted metabolites in gastric juice using liquid chromatography-tandem mass spectrometry (LC-MS/MS). We successfully analyzed 70 human gastric juice samples from patients with chronic superficial gastritis (CSG, n = 20), intestinal metaplasia (IM, n = 12), and gastric cancer (n = 38). Furthermore, we investigated the relevance between BA metabolism and gastric cancer. There were statistical differences in the metabolism of cholic acid (CA) into deoxycholic acid (DCA) based on the progression of CSG into IM and gastric cancer. Hence, the progression of gastric cancer might be related to the alterations in gut microbiome composition. We provide insight into the etiological mechanisms of the progression of gastric cancer and biomarkers to diagnose and treat gastric cancer.

Aberrant DNA Polymerase Beta Enhances H. pylori Infection Induced Genomic Instability and Gastric Carcinogenesis in Mice.

H. pylori is a significant risk factor of gastric cancer that induces chronic inflammation and oxidative DNA damage to promote gastric carcinoma. Base excision repair (BER) is required to maintain the genome integrity and prevent oxidative DNA damage. Mutation in DNA polymerase beta (Pol β) impacts BER efficiency and has been reported in approximately 30–40% of gastric carcinoma tumors. In this study, we examined whether reduced BER capacity associated with mutation in the POLB gene, along with increased DNA damage generated by H. pylori infection, accelerates gastric cancer development. By infecting a Pol β mutant mouse model that lacks dRP lyase with H. pylori, we show that reactive oxygen and nitrogen species (RONS) mediated DNA damage is accumulated in Pol β mutant mice (L22P). In addition, H. pylori infection in Leu22Pro (L22P) mice significantly increases inducible nitric oxide synthesis (iNOS) mediated chronic inflammation. Our data show that L22P mice exhibited accelerated H. pylori induced carcinogenesis and increased tumor incidence. This work shows that Pol β mediated DNA repair under chronic inflammation conditions is an important suppressor of H. pylori induced stomach carcinogenesis.

Roles of E-cadherin and Noncoding RNAs in the Epithelial-mesenchymal Transition and Progression in Gastric Cancer.

The epithelial–mesenchymal transition (EMT) is thought to be at the root of invasive and metastatic cancer cell spreading. E-cadherin is an important player in this process, which forms the structures that establish and maintain cell–cell interactions. A partial or complete loss of E-cadherin expression in the EMT is presumably mediated by mechanisms that block the expression of E-cadherin regulators and involve the E-cadherin-associated transcription factors. The protein is involved in several oncogenic signaling pathways, such as the Wnt/β-catenin, Rho GTPase, and EGF/EGFR, whereby it plays a role in many tumors, including gastric cancer. Such noncoding transcripts as microRNAs and long noncoding RNAs—critical components of epigenetic control of gene expression in carcinogenesis—contribute to regulation of the E-cadherin function by acting directly or through numerous factors controlling transcription of its gene, and thus affecting not only cancer cell proliferation and metastasis, but also the EMT. This review focuses on the role of E-cadherin and the non-coding RNAs-mediated mechanisms of its expressional control in the EMT during stomach carcinogenesis.

Protective Effect of Curcumin against Nitrosamine‐induced Gastric Cancer in Rats

BackgroundNitrosamine acts as a carcinogenic agent and induces gastric cancer in rats. The mechanisms underlies nitrosamine‐mediated gastric cancer pathogenesis need to be investigated. Experimental studies continue to support the notion that curcumin combat cancer by acting as a dietary antioxidant.ObjectiveOur study model was undertaken to investigate the preventive effect of curcumin supplementation against nitrosamine‐induced oxidative stress and carcinogenesis in rat stomach.MethodsForty Sprague‐Dawley rats (8 weeks old) were randomly divided into 4 groups (10 rats/group). Control group was fed a standard rat chow diet; nitrosamine‐treated group was fed a standard rat chow diet and also received intraperitonial injections of nitrosamine. The other two groups received oral supplementations of curcumin in the presence or absence of nitrosamine injection. All animals were fed ad‐libitum for 16 weeks. At the end of the experiment all rats were sacrificed and the gastric tissues were examined microscopically for gastric cancer lesions development, and for biochemical measurements of oxidative stress indices.ResultsOur results showed that nitrosamine causes gastric cancer development, as well as inducing oxidative stress in gastric tissue as evidenced by glutathione depletion and inhibition of antioxidant enzymes. The concomitant treatment of nitrosamine with curcumin significantly ameliorated the cytotoxic effects of nitrosamine.ConclusionThe results of this study provide in vivo evidence that curcumin supplementation protects against nitrosamine‐induced gastric cancer in the used animal model.Support or Funding InformationThis research was supported by Strategic Grant Funding (CL/SQU‐UAEU/15/03) and Internal Grant Funding (IG/AGR/FOOD/17/1), College of Agricultural and Marine Sciences, Sultan Qaboos UniversityThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Abstract 919: Identification of stem cells in stomach corpus and antrum

Abstract Gastric cancer is still relatively poorly understood, because of the lack of knowledge on stem cells in stomach. By radio-labeling experiments and electron microscopy, rapidly proliferating stem cells have been suggested in isthmus of both corpus (which is just below pit cell zone) and antrum (which is a quarter above the base) (1). In addition, there have been reports indicating the proliferation capacity under certain conditions in a subset of chief cells present at the base in corpus (2). We reported earlier that 270 bp Runx1 enhancer element (termed aR1) that drives the expression of Runx1 in hematopoietic stem cells (3). We found that eR1 also marks the cells in these three locations of stomach (4). In antrum, the stem cell marker, Lgr5, has been reported to mark the cells at the base of antrum but not in corpus (5). eR1+ and Lgr5+ stem cell in antrum appears to be different. It will be interesting to find out the difference between these two types of stem cells. Transgenic mouse was generated that harbors eR1 linked to heterologous promoter and Cre recombinase (eR1-CreERT2). By treating the mouse with tamoxifen, we showed lineage tracing from eR1+ cells in the isthmus of both corpus and antrum that replenish entire glands. We expressed K-rasG12D in eR1+ cells in isthmus and observed antralization of corpus epithelium that is similar to precancerous lesion in human stomach after H pylori infection. On the other hand, eR1+ chief cells rarely multiply. However, they robustly proliferate after tissue damage or oncogene expression. When K-rasG12D is activated in eR1+ chief cells, they show retrodifferentiation to show SPEM (spasmolytic polypeptide expressing metaplasia) phenotype. eR1+ chief cells appear to be reserve stem cells that can replace cells after tissue damage. We now have capability to activate or inactivate genes of interest in the stomach stem cells. We are examining stepwise carcinogenesis in stomach. From eR1+ cells in isthmus of both corpus and antrum, we are generating organoids. We will describe interesting difference in the properties of organoids generated from eR1+ cells from corpus and those from antrum. &amp;lt;Reference&amp;gt; (1) Karam and Leblond., The Anatomical Record 1993; 236: 259-273. (2) Goldenring et al., Gastroenterology 2011; 138: 2207-2210. (3) Ng et al., Stem Cells 2010; 28: 1869-81. (4) Matsuo et al., Gastroenterology 2016; PMID: 27670082. (5) Barker et al., Cell Stem Cell 2010; 6: 25-36. Citation Format: Junichi Matsuo, Akihiro Yamamura, Khay Guan Yeoh, Motomi Osato, Yoshiaki Ito. Identification of stem cells in stomach corpus and antrum [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 919. doi:10.1158/1538-7445.AM2017-919

Chemopreventive Activity of MGN-3/Biobran Against Chemical Induction of Glandular Stomach Carcinogenesis in Rats and Its Apoptotic Effect in Gastric Cancer Cells.

In the current study, we investigated the chemopreventive activity of arabinoxylan rice bran, MGN-3/Biobran, against chemical induction of glandular stomach carcinogenesis in rats. Gastric cancer was induced by carcinogen methylnitronitrosoguanidine (MNNG), and rats received MNNG alone or MNNG plus Biobran (40 mg/kg body weight) for a total of 8 months. Averaged results from 2 separate readings showed that exposure to MNNG plus Biobran caused gastric dysplasia and cancer (adenocarcinoma) in 4.5/12 rats (9/24 readings, 37.5%), with 3.5/12 rats (7/24 readings, 29.2%) showing dysplasia and 1/12 rats (8.3%) developing adenocarcinoma. In contrast, in rats treated with MNNG alone, 8/10 (80%) developed dysplasia and adenocarcinoma, with 6/10 rats (60%) showing dysplasia and 2/10 rats (20%) developing adenocarcinoma. The effect of combining both agents was also associated with significant suppression of the expression of the tumor marker Ki-67 and remarkable induction in the apoptotic gastric cancer cells via mitochondrial-dependent pathway as indicated by the upregulation in p53 expression, Bax expression, downregulation in Bcl-2 expression, an increase in Bax/Bcl-2 ratio, and an activation of caspase-3. In addition, Biobran treatment induced cell-cycle arrest in the subG1 phase, where the hypodiploid cell population was markedly increased. Moreover, Biobran treatment protected rats against MNNG-induced significant decrease in lymphocyte levels. We conclude that Biobran provides protection against chemical induction of glandular stomach carcinogenesis in rats and may be useful for the treatment of human patients with gastric cancer.

Helicobacter pylori with high thioredoxin-1 expression promotes stomach carcinogenesis in Mongolian gerbils

Previous studies by this group have shown that Helicobacter pylori with high thioredoxin-1 (Trx1) expression might be involved in stomach carcinogenesis in vitro. To study histopathological changes of the stomach mucosa in vivo, a Mongolian gerbil model infected with H.pylori with high Trx1 expression was established. Healthy, male Mongolian gerbils (n=75) were randomly divided into 3 groups: controls (n=15), which were not infected with H.pylori, high Trx1 (n=30) which were infected with H.pylori with high Trx1 expression and low Trx1 (n=30) which were infected with low Trx1 expression H.pylori. The animals were sacrificed at 4, 20, 34, 48, 70 and 90 weeks after inoculation. The Mongolian gerbil model of H.pylori infection was successfully established. Three animals died during the study, leaving 72 animals (controls, n=14; low Trx1, n=29; high Trx1, n=29) examined on schedule. Histopathological analysis of the stomach mucosa showed gradually increased aggravation over time in the high and low Trx1 groups. Compared with control and low Trx1, the histopathological changes were more serious in the high Trx1 group. At 90 weeks, no abnormal changes were found in the controls, but 62.5% of the high Trx1 group and 33.3% of the low Trx1 showed adenocarcinomas. The H.pylori Trx1 level in gastric cancer tissue was significantly higher than that from gastritis tissue. Within gastric cancer cells, high Trx1 expression in H.pylori significantly upregulated cyclin D1. High Trx1 expression in H.pylori promoted stomach carcinogenesis. More studies are needed to confirm this finding.

N-Methyl-N-nitrosourea as a mammary carcinogenic agent

The administration of chemical carcinogens is one of the most commonly used methods to induce tumors in several organs in laboratory animals in order to study oncologic diseases of humans. The carcinogen agent N-methyl-N-nitrosourea (MNU) is the oldest member of the nitroso compounds that has the ability to alkylate DNA. MNU is classified as a complete, potent, and direct alkylating compound. Depending on the animals' species and strain, dose, route, and age at the administration, MNU may induce tumors' development in several organs. The aim of this manuscript was to review MNU as a carcinogenic agent, taking into account that this carcinogen agent has been frequently used in experimental protocols to study the carcinogenesis in several tissues, namely breast, ovary, uterus, prostate, liver, spleen, kidney, stomach, small intestine, colon, hematopoietic system, lung, skin, retina, and urinary bladder. In this paper, we also reviewed the experimental conditions to the chemical induction of tumors in different organs with this carcinogen agent, with a special emphasis in the mammary carcinogenesis.

Copy Number Gains at 8q24 and 20q11-q13 in Gastric Cancer Are More Common in Intestinal-Type than Diffuse-Type.

The present study was aimed at discovering DNA copy number alterations (CNAs) involved in the carcinogenesis of stomach and at understanding their clinicopathological significances in the Korean population. DNA copy numbers were analyzed using Agilent 244K or 400K array comparative genomic hybridization (aCGH) in fresh-frozen tumor and matched normal tissues from 40 gastric cancer patients. Some of the detected CNA regions were validated using multiplex ligation-dependent probe amplification (MLPA) in six of the 40 patients and customized Agilent 60K aCGH in an independent set of 48 gastric cancers. The mRNA levels of genes at common CNA regions were analyzed using quantitative real-time PCR. Copy number gains were more common than losses across the entire genome in tumor tissues compared to matched normal tissues. The mean number of alterations per case was 64 for gains and 40 for losses, and the median aberration length was 44016 bp for gains and 4732 bp for losses. Copy number gains were frequently detected at 7p22.1 (20%), 8q24.21 (27%–30%), 8q24.3 (22%–48%), 13q34 (20%–31%), and 20q11-q13 (25%–30%), and losses at 3p14.2 (43%), 4q35.2 (27%), 6q26 (23%), and 17p13.3 (20%–23%). CNAs at 7p22.1, 13q34, and 17p13.3 have not been reported in other populations. Most of the copy number losses were associated with down-regulation of mRNA levels, but the correlation between copy number gains and mRNA expression levels varied in a gene-dependent manner. In addition, copy number gains tended to occur more commonly in intestinal-type cancers than in diffuse-type cancers. In conclusion, the present study suggests that copy number gains at 8q24 and 20q11-q13 and losses at 3p14.2 may be common events in gastric cancer but CNAs at 7p22.1, 13q34, and 17p13.3 may be Korean-specific.

Abstract LB-139: Tissue stem cell specific enhancer element identifies two types of stem cells in the corpus epithelium of the stomach

Abstract The activity of a previously identified hematopoietic stem cell marker, Runx1 enhancer element (eR1) (Ng et al, Stem Cells 28, 1869-1881, 2010), was found to mark tissue stem cells of multiple organs. In corpus of stomach, stem cells are known to reside at isthmus, upper part of gastric unit. They are undifferentiated cells. However, molecular approach to these stem cells has not been described. Recently, fully differentiated Pepsinogen expressing chief cells at the bottom of gastric unit were shown to have tissue regeneration activity, and these cell were named reserve stem cells (Stange et al, Cell 155, 357-368, 2013). In our study, eR1 was shown to mark stem cells of both types. Lineage tracing experiments demonstrated that both types of stem cells continuously gave rise to mature cells to maintain the gastric unit. Manipulation of gene expression in a stem cell-specific manner in the stomach, especially in undifferentiated stem cells, is a long sought-after approach to study gastric carcinogenesis. We crossed transgenic mouse carrying eR1-CreERT2 with LSL-K-rasG12D mice. After tamoxifen treatment, rapid differentiation from the stem cells in the isthmus was observed, mainly into Muc5ac+ cells (surface epithelial cells). As a result, pseudo-pyloric metaplasia was induced which is similar to that observed in human gastritis. Acid-producing parietal cells were eliminated during this process. Rapid generation of Muc5ac+ cells and other phenotype are similar, but not identical, to the phenotype described in Menetrier disease which is known to be caused by excessive production of TGF-α and hyper-stimulation of EGF receptor (Reviewed in Coffey et al, J Clin Invest. 117:70-80, 2007). Menetrier disease is considered to be pre-malignant state. Activation of K-rasG12D in eR1+ chief cells also induced metaplastic lesions. In this case, pepsinogen producing chief cells robustly expressed the marker of mucous neck cells that are considered to be a precursor to chief cells. Therefore, chief cells appeared to be de-differentiated to precursor cells and acquired the stem cell property. We are using eR1 to study step-wise carcinogenesis in stomach and other organs. Citation Format: Junichi Matsuo, Shunichi Kimura, Cai Ping Koh, Md Zakir Hossain, Akihiro Yamamura, Kazuyoshi Kohu, Michiaki Unno, Jimmy Bok Yan So, Feng Zhu, Supriya Srivastava, Teh Meng, Nicholas Barker, Khay Guan Yeoh, Motomi Osato, Yoshiaki Ito. Tissue stem cell specific enhancer element identifies two types of stem cells in the corpus epithelium of the stomach. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr LB-139. doi:10.1158/1538-7445.AM2015-LB-139

LncRNA GAS5 enhances G1 cell cycle arrest via binding to YBX1 to regulate p21 expression in stomach cancer.

Long non-coding RNAs (lncRNAs), which have evolved as important gene expression modulators, are involved in human malignancies. The down-regulation of lncRNA growth arrest specific transcript 5 (GAS5) has been reported in several cancers, however, the underlying mechanism of lncRNA GAS5 in stomach cancer is poorly understood. In this study, we found that lncRNA GAS5 had lower expression in stomach cancer tissues than the normal counterparts. lncRNA GAS5 was shown to interact with Y-box binding protein 1 (YBX1), and lncRNA GAS5 knockdown was shown to accelerate YBX1 protein turnover without affecting YBX1 transcription. lncRNA GAS5 down-regulation reduced the YBX1 protein level, which decreased YBX1-transactivated p21 expression and abolished G1 phase cell cycle arrest in stomach cancer. These results delineate a novel mechanism of lncRNA GAS5 in suppressing stomach carcinogenesis, and the lncRNA GAS5/YBX1/p21 pathway we discovered may provide useful targets for developing lncRNA-based therapies for stomach cancer.

12 Role of CDH1, TGFβR2, and KRAS Mutations in the Carcinogenesis of Stomach

12 Role of CDH1, TGFβR2, and KRAS Mutations in the Carcinogenesis of Stomach