Current Status on Stem Cells and Cancers of the Gastric Epithelium

Gastric cancer is still a leading cause of cancer-related mortality worldwide in spite of declining incidence. Gastric cancers are, essentially, adenocarcinomas and one of the strongest risk factors is still infection with Helicobacter pylori. Within the last years, it became clear that gastric self-renewal and carcinogenesis are intimately linked, particularly during chronic inflammatory conditions. Generally, gastric cancer is now regarded as a disease resulting from dysregulated differentiation of stem and progenitor cells, mainly due to an inflammatory environment. However, the situation in the stomach is rather complex, consisting of two types of gastric units which show bidirectional self-renewal from an unexpectedly large variety of progenitor/stem cell populations. As in many other tumors, cancer stem cells have also been characterized for gastric cancer. This review focuses on the various gastric epithelial stem cells, how they contribute to self-renewal and which routes are known to gastric adenocarcinomas, including their stem cells.     

ABO Blood Group System and Gastric Cancer: A Case-Control Study and Meta-Analysis

This study focuses on the association between the ABO blood group system and the risk of gastric cancer or Helicobacter pylori infection. The data for the ABO blood group was collected from 1045 cases of gastric cancer, whereby the patient underwent a gastrectomy in Ruijin Hospital, Shanghai. The information on the ABO blood group from 53,026 healthy blood donors was enrolled as control. We searched the Pubmed database on the relationship between ABO blood groups and gastric cancer risk for meta-analysis. In our case-control study, the risk of gastric cancer in blood group A was significantly higher than that in non-A groups (O, B and AB) (odd ratio, OR1.34; 95% confidential interval, CI 1.25–1.44). Compared with non-O groups (A, B and AB), individuals with blood group O demonstrated a reduced risk of gastric cancer (OR = 0.80; 95% CI 0.72–0.88). The proportion of H. pylori infection in blood group A individuals was significantly higher than that in non-A blood groups (OR = 1.42; 95% CI 1.05–1.93). We further combined our data with the published data of others, and crossreferenced the risk of gastric cancer with the blood type, finding consistent evidence that gastric cancer risk in the blood A group was higher than that in the non-A groups (OR = 1.11; 95% CI 1.07–1.15), and that blood type O individuals were consistently shown gastric cancer risk reduction (OR = 0.91; 95% CI 0.89–0.94). Our study concluded that there was a slightly increased risk of gastric cancer in blood group A individuals, and people with blood type A are more prone to be infected by H. pylori than other ABO blood type individuals, whereas, a slightly decreased risk of gastric cancer was identified in blood type O individuals.     

Mucin 1 Gene (MUC1) and Gastric-Cancer Susceptibility

Gastric cancer (GC) is one of the major malignant diseases worldwide, especially in Asia. It is classified into intestinal and diffuse types. While the intestinal-type GC (IGC) is almost certainly caused by Helicobacter pylori (HP) infection, its role in the diffuse-type GC (DGC) appears limited. Recently, genome-wide association studies (GWAS) on Japanese and Chinese populations identified chromosome 1q22 as a GC susceptibility locus which harbors mucin 1 gene (MUC1) encoding a cell membrane-bound mucin protein. MUC1 has been known as an oncogene with an anti-apoptotic function in cancer cells; however, in normal gastric mucosa, it is anticipated that the mucin 1 protein has a role in protecting gastric epithelial cells from a variety of external insults which cause inflammation and carcinogenesis. HP infection is the most definite insult leading to GC, and a protective function of mucin 1 protein has been suggested by studies on Muc1 knocked-out mice.     

Tannins, peptic ulcers and related mechanisms

This review of the current literature aims to study correlations between the chemical structure and gastric anti-ulcer activity of tannins. Tannins are used in medicine primarily because of their astringent properties. These properties are due to the fact that tannins react with the tissue proteins with which they come into contact. In gastric ulcers, this tannin-protein complex layer protects the stomach by promoting greater resistance to chemical and mechanical injury or irritation. Moreover, in several experimental models of gastric ulcer, tannins have been shown to present antioxidant activity, promote tissue repair, exhibit anti Helicobacter pylori effects, and they are involved in gastrointestinal tract anti-inflammatory processes. The presence of tannins explains the anti-ulcer effects of many natural products.     

Effect of Byrsonima crassa and Phenolic Constituents on Helicobacter pylori-Induced Neutrophils Oxidative Burst

Byrsonima crassa Niedenzu (Malpighiaceae) is used in Brazilian folk medicine for the treatment of diseases related mainly to gastric ulcers. In a previous study, our group described the gastric protective effect of the methanolic extract from the leaves of B. crassa. The present study was carried out to investigate the effects of methanolic extract and its phenolic compounds on the respiratory burst of neutrophils stimulated by H. pylori using a luminol-based chemiluminescence assay as well as their anti-H. pylori activity. The suppressive activity on oxidative burst of H. pylori-stimulated neutrophils was in the order of methyl gallate > (+)-catechin > methanol extract > quercetin 3-O-α-l-arabinopyranoside > quercetin 3-O-β-d-galactopyranoside > amentoflavone. Methyl gallate, compound that induced the highest suppressive activity with IC(50) value of 3.4 μg/mL, did not show anti-H. pylori activity. B. crassa could be considered as a potential source of natural antioxidant in gastric ulcers by attenuating the effects on the damage to gastric mucosa caused by neutrophil generated reactive oxygen species, even when H. pylori displays its evasion mechanisms.     

The Role of Sialyl-Tn in Cancer

Activation of an aberrant glycosylation pathway in cancer cells can lead to expression of the onco-foetal sialyl-Tn (sTn) antigen. STn is a truncated O-glycan containing a sialic acid α-2,6 linked to GalNAc α-O-Ser/Thr and is associated with an adverse outcome and poor prognosis in cancer patients. The biosynthesis of the sTn antigen has been linked to the expression of the sialytransferase ST6GalNAc1, and also to mutations in and loss of heterozygosity of the COSMC gene. sTn neo- or over-expression occurs in many types of epithelial cancer including gastric, colon, breast, lung, oesophageal, prostate and endometrial cancer. sTn is believed to be carried by a variety of glycoproteins and may influence protein function and be involved in tumour development. This review discusses how the role of sTn in cancer development and tumour cell invasiveness might be organ specific and occur through different mechanisms depending on each cancer type or subtype. As the sTn-antigen is expressed early in carcinogenesis targeting sTn in cancer may enable the targeting of tumours from the earliest stage.     

Novel Risk Associations between microRNA Polymorphisms and Gastric Cancer in a Chilean Population

Gastric cancer (GC) is the fifth leading cause of cancer deaths in the world, with variations across geographical regions and ethnicities. Emerging evidence indicates that miRNA expression is dysregulated in GC and its polymorphisms may contribute to these variations, which has yet to be explored in Latin American populations. In a case-control study of 310 GC patients and 311 healthy donors from Chile, we assessed the association of 279 polymorphisms in 242 miRNA genes. Two novel polymorphisms were found to be associated with GC: rs4822739:C>G (miR-548j) and rs701213:T>C (miR-4427). Additionally, rs1553867776:T>TCCCCA (miR-4274) and rs12416605:C>T (miR-938) were associated with intestinal-type GC, and rs4822739:C>G (miR-548j) and rs1439619:T>G (miR-3175) with TNM I-II stage. The polymorphisms rs6149511:T> TGAAGGGCTCCA (miR-6891), rs404337:G>A (miR-8084), and rs1439619:T>G (miR-3175) were identified among H.pylori-infected GC patients and rs7500280:T>C (miR-4719) and rs1439619:T>G (miR-3175) were found among H. pylori cagPAI+ infected GC cases. Prediction analysis suggests that seven polymorphisms could alter the secondary structure of the miRNA, and the other one is located in the seed region of miR-938. Targets of miRNAs are enriched in GC pathways, suggesting a possible biological effect. In this study, we identified seven novel associations and replicated one previously described in Caucasian population. These findings contribute to the understanding of miRNA genetic polymorphisms in the GC pathogenesis.     

Aqueous and Organic Solvent-Extracts of Selected South African Medicinal Plants Possess Antimicrobial Activity against Drug-Resistant Strains of Helicobacter pylori: Inhibitory and Bactericidal Potential

The aim of this study was to identify sources of cheap starting materials for the synthesis of new drugs against Helicobacter pylori. Solvent-extracts of selected medicinal plants; Combretum molle, Sclerocarya birrea, Garcinia kola, Alepidea amatymbica and a single Strychnos species were investigated against 30 clinical strains of H. pylori alongside a reference control strain (NCTC 11638) using standard microbiological techniques. Metronidazole and amoxicillin were included in these experiments as positive control antibiotics. All the plants demonstrated anti-H. pylori activity with zone diameters of inhibition between 0 and 38 mm and 50% minimum inhibitory concentration (MIC(50)) values ranging from 0.06 to 5.0 mg/mL. MIC(50) values for amoxicillin and metronidazole ranged from 0.001 to 0.63 mg/mL and 0.004 to 5.0 mg/mL respectively. The acetone extracts of C. molle and S. birrea exhibited a remarkable bactericidal activity against H. pylori killing more than 50% of the strains within 18 h at 4× MIC and complete elimination of the organisms within 24 h. Their antimicrobial activity was comparable to the control antibiotics. However, the activity of the ethanol extract of G. kola was lower than amoxicillin (P < 0.05) as opposed to metronidazole (P > 0.05). These results demonstrate that S. birrea, C. molle and G. kola may represent good sources of compounds with anti-H. pylori activity.     

Morphological and Cellular Features of Innate Immune Reaction in Helicobacter pylori Gastritis: A Brief Review

Innate and adaptive immunity are both involved in acute and chronic inflammatory processes. The main cellular players in the innate immune system are macrophages, mast cells, dendritic cells, neutrophils, eosinophils, and natural killer (NK), which offer antigen-independent defense against infection. Helicobacter pylori (H. pylori) infection presents peculiar characteristics in gastric mucosa infrequently occurring in other organs; its gastric colonization determines a causal role in both gastric carcinomas and mucosa-associated lymphoid tissue lymphoma. In contrast, an active role for Epstein-Barr virus (EBV) has been identified only in 9% of gastric carcinomas. The aim of the present review is to discuss the role of cellular morphological effectors in innate immunity during H. pylori infection and gastric carcinogenesis.     

Associations of NR5A2 Gene Polymorphisms with the Clinicopathological Characteristics and Survival of Gastric Cancer

The orphan nuclear receptor (NR5A2), which belongs to the NR5A subfamily of nuclear receptors, is expressed in developing and adult tissues of endodermal origin, and can contribute to the development of several cancers through regulating cell proliferation. NR5A2 (rs3790843 and rs3790844) single nucleotide polymorphisms (SNPs) genotyping were examined in DNA samples, extracted from paraffin-embedded cancer tissue. Clinicopathologic and follow-up data were collected from 944 patients with gastric cancer (GC). Associations of the 2 SNPs with the progression and prognosis in gastric cancer patients were analyzed using the SPSS version 18.0. We found that NR5A2 rs3790843 polymorphism was significantly associated with the risk of GC which had regional lymph node metastasis (p = 0.044) or distant metastasis (p = 0.020). Our results also indicated that rs3790844 polymorphism was associated with the increased overall survival (OS) of GC patients in the dominant model (GG vs. GA/AA, HR (hazard ratio) = 0.823, 95% CI (confidence interval) = 0.679–0.997), suggesting a potential protective role of the variant A allele. Additionally, in the stratified analysis, both NR5A2 rs3790843 and rs3790844 polymorphism were associated with significantly lower risk of death in the groups of female, tumor size >5 cm in a dominant model. Our results represent the first demonstration that the NR5A2 rs3790844 polymorphism is associated with increased OS of GC patients in the dominant model, and similar results were found among the female group and tumor size >5 cm group for NR5A2 rs3790843 polymorphism. Further validation in other larger studies with different ethnic populations and functional evaluations are needed.     

Role of Glycated High Mobility Group Box-1 in Gastric Cancer

Advanced glycation end products (AGEs) are produced in response to a high-glucose environment and oxidative stress and exacerbate various diseases. N^ε-(Carboxymethyl)lysine (CML) is an AGE that is produced by the glycation of lysine residues of proteins. There are a few reports on alterations in protein function due to CML modification; however, its association with cancer is not clear. We investigated the significance of CML modification in high mobility group box protein-1 (HMGB1), a cytokine that is significantly associated with cancer progression. Treatment of the gastric cancer cell lines TMK1 and MKN74 with glyoxal or glucose resulted in increased CML modification compared to untreated cells. CML-HMGB1 was modified via oxidation and more pronouncedly activated the receptor for AGE and downstream AKT and NF-κB compared to naïve HMGB1 and oxidized HMGB1. CML-HMGB1 bound with reduced affinity to DNA and histone H3, resulting in enhanced extranuclear translocation and extracellular secretion. Treatment of gastric cancer cells with CML-HMGB1 enhanced cell proliferation and invasion, sphere formation, and protection from thapsigargin-induced apoptosis, and decreased 5-FU sensitivity in comparison to HMGB1. Further, CML-HMGB1 was detected at various levels in all the 10 gastric cancer tumor specimens. HMGB1 levels correlated with primary tumor progression and distant metastasis, whereas CML-HMGB1 levels were associated with primary tumor progression, lymph node metastasis, distant metastasis, and stage. In addition, CML-HMGB1 levels correlated with oxidative stress in cancer tissues and resistance to neoadjuvant therapy. Therefore, CML modification of HMGB1 enhanced the cancer-promoting effect of HMGB1. In this study, CML-HMGB1 has been highlighted as a new therapeutic target, and analysis of the molecular structure of CML-HMGB1 is desired in the future.     

Healing,Antioxidant and Cytoprotective Properties of Indigofera truxillensis in Different Models of Gastric Ulcer in Rats

The present study evaluated the antiulcerogenic activity and mechanisms of the aqueous (AqF 100 mg/kg) and ethyl acetate (AcF 50 mg/kg) fractions from Indigofera truxillensis leaves. This dose was selected to assess its activity on ulcer healing and its action on gastric acid and mucus secretion, prostaglandin production and antioxidant enzyme activity (superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and glutathione reductase (GSH-Rd)). Gastric ulcer was induced by absolute ethanol. Antisecretory action, mucus and prostaglandin production, healing and antioxidant enzyme activities were evaluated for both fractions. AqF and AcF significantly inhibited the gastric mucosal damage caused by ethanol. This effect was statistically significant at 100 and 50 mg/kg compared with the vehicle. Neither fraction interfered with gastric secretion. AcF increased the PGE₂ production, and both fractions increased mucus production. l-NAME did not alter the gastroprotection exerted by the fractions, but N-ethylmaleimide attenuated only AcF. In the ischemia/reperfusion model both fractions inhibited the mucosal damage. AcF increased SOD, GSH-Px and GSH-Rd activity, but AqF increased only SOD and GSH-Px. In the acetic acid-induced ulcer model AcF only accelerated ulcer healing. These results showed that Indigofera truxillensis acted as a gastroprotective agent, stimulating protective factors and antioxidants enzymes.     

Helicobacter pylori Disrupts Host Cell Membranes, Initiating a Repair Response and Cell Proliferation

Helicobacter pylori (H. pylori), the human stomach pathogen, lives on the inner surface of the stomach and causes chronic gastritis, peptic ulcer, and gastric cancer. Plasma membrane repair response is a matter of life and death for human cells against physical and biological damage. We here test the hypothesis that H. pylori also causes plasma membrane disruption injury, and that not only a membrane repair response but also a cell proliferation response are thereby activated. Vacuolating cytotoxin A (VacA) and cytotoxin-associated gene A (CagA) have been considered to be major H. pylori virulence factors. Gastric cancer cells were infected with H. pylori wild type (vacA+/cagA+), single mutant (ΔvacA or ΔcagA) or double mutant (ΔvacA/ΔcagA) strains and plasma membrane disruption events and consequent activation of membrane repair components monitored. H. pylori disrupts the host cell plasma membrane, allowing localized dye and extracellular Ca(2+) influx. Ca(2+)-triggered members of the annexin family, A1 and A4, translocate, in response to injury, to the plasma membrane, and cell surface expression of an exocytotic maker of repair, LAMP-2, increases. Additional forms of plasma membrane disruption, unrelated to H. pylori exposure, also promote host cell proliferation. We propose that H. pylori activation of a plasma membrane repair is pro-proliferative. This study might therefore provide new insight into potential mechanisms of H. pylori-induced gastric carcinogenesis.     

DNA Sequence Analysis of South African Helicobacter pylori Vacuolating Cytotoxin Gene (vacA)

Sequence diversity and population structures can vary widely among pathogenic bacteria species. In some species, all isolates are highly similar, whereas in others most of the isolates are distinguished easily. H. pylori is known for its wide genetic diversity amongst the various strains most especially in the genes involved in virulence. The aim of this study was to evaluate by PCR and sequence analysis, the genetic profile of H. pylori vacA gene (s1, s2, m1 and m2). We sequenced small DNA segments from 13 vacAs1, 10 vacAm2, 6 vacAm1 and 6 vacAs2 strains which were amplified with amplicon size of 259/286 bp, 290 bp and 352 bp for vacAs1/s2, m1 and m2 respectively. Based on similarities among our strains accession numbers were provided for seven vacAs1 (HQ709109-HQ709115), six vacAs2 (JN848463-JN848468), six vacAm1 (JN848469-JN848474) and six vacAm2 (HQ650801-HQ650806) strains. Amongst the strains studied, 98.07%, 98.58%, 97.38% and 95.41% of vacAs1, vacAs2, vacAm1 and vacAm2 of the strains were conserved respectively. Findings of this study underscores the importance of understanding the virulence composition and diversity of H. pylori in South Africa for enhanced clinico-epidemiological monitoring and pathophysiology of disease.     

Amplification Target ADRM1: Role as an Oncogene and Therapeutic Target for Ovarian Cancer

Approximately 25,000 ovarian cancers are diagnosed in the U.S. annually, and 75% are in the advanced stage and largely incurable. There is critical need for early detection tools and novel treatments. Proteasomal ubiquitin receptor ADRM1 is a protein that is encoded by the ADRM1 gene. Recently, we showed that among 20q13-amplified genes in ovarian cancer, ADRM1 overexpression was the most highly correlated with amplification and was significantly upregulated with respect to stage, recurrence, and metastasis. Its overexpression correlated significantly with shorter time to recurrence and overall survival. Array-CGH and microarray expression of ovarian cancer cell lines provided evidence consistent with primary tumor data that ADRM1 is a 20q13 amplification target. Herein, we confirm the ADRM1 amplicon in a second ovarian cancer cohort and define a minimally amplified region of 262 KB encompassing seven genes. Additionally, using RNAi knock-down of ADRM1 in naturally amplified cell line OAW42 and overexpression of ADRM1 via transfection in ES2, we show that (1) ADRM1 overexpression increases proliferation, migration, and growth in soft agar, and (2) knock-down of ADRM1 results in apoptosis. Proteomic analysis of cells with ADRM1 knock-down reveals dysregulation of proteins including CDK-activating kinase assembly factor MAT1. Taken together, the results indicate that amplified ADRM1 is involved in cell proliferation, migration and survival in ovarian cancer cells, supporting a role as an oncogene and novel therapeutic target for ovarian cancer.     

Characterization,Purification of Poncirin from Edible Citrus Ougan (Citrus reticulate cv. Suavissima) and Its Growth Inhibitory Effect on Human Gastric Cancer Cells SGC-7901

Poncirin is a bitter flavanone glycoside with various biological activities. Poncirin was isolated from four different tissues (flavedo, albedo, segment membrane, and juice sac) of Ougan fruit (Citrus reticulate cv. Suavissima). The highest content of poncirin was found in the albedo of Ougan fruit (1.37 mg/g DW). High speed counter-current chromatography (HSCCC) combined with D101 resin chromatography was utilized for the separation and purification of poncirin from the albedo of Ougan fruit. After this two-step purification, poncirin purity increased from 0.14% to 96.56%. The chemical structure of the purified poncirin was identified by both HPLC-PDA and LC-MS. Poncirin showed a significant in vitro inhibitory effect on the growth of the human gastric cancer cells, SGC-7901, in a dose-dependent manner. Thus, poncirin from Ougan fruit, may be beneficial for gastric cancer prevention. The purification method demonstrated here will be useful for further studies on the pharmacological mechanism of poncirin activity, as well as for guiding the consumption of Ougan fruit.     

Homeostasis and Cancer Initiation: Organoids as Models to Study the Initiation of Gastric Cancer

Gastric cancer represents a significant disease burden worldwide. The factors that initiate cancer are not well understood. Chronic inflammation such as that triggered by H. pylori infection is the most significant cause of gastric cancer. In recent years, organoid cultures developed from human and animal adult stem cells have facilitated great advances in our understanding of gastric homeostasis. Organoid models are now being exploited to investigate the role of host genetics and bacterial factors on proliferation and DNA damage in gastric stem cells. The impact of a chronic inflammatory state on gastric stem cells and the stroma has been less well addressed. This review discusses what we have learned from the use of organoid models to investigate cancer initiation, and highlights questions on the contribution of the microbiota, chronic inflammatory milieu, and stromal cells that can now be addressed by more complex coculture models.