Wnt/β-catenin, an oncogenic pathway targeted by H. pylori in gastric carcinogenesis

Role of the Microbiome in the Diagnosis and Management of Gastroesophageal Cancers

PURPOSE

Stomach and esophageal cancers are among the highest mortality from cancers worldwide. Microbiota has an interplaying role within the human gastrointestinal (GI) tract. Dysbiosis occurs when a disruption of the balance between the microbiota and the host happens. With this narrative review, we discuss the main alterations in the microbiome of gastroesophageal cancer, revealing its potential role in the pathogenesis, early detection, and treatment.

RESULTS

Helicobacter pylori plays a major role the development of a cascade of preneoplastic conditions ranging from atrophic gastritis to metaplasia and dysplasia, ultimately culminating in gastric cancer, while other pathogenic agents are Fusobacterium nucleatum, Bacteroides fragilis, Escherichia coli, and Lactobacillus. Campylobacter species (spp.)'s role in the progression of esophageal adenocarcinoma may parallel that of Helicobacter pylori in the context of gastric cancer, with other esophageal carcinogenic agents being Escherichia coli, Bacteroides fragilis, and Fusobacterium nucleatum. Moreover, gut microbiome could significantly alter the outcomes of chemotherapy and immunotherapy. The gut microbiome can be modulated through interventions such as antibiotics, probiotics, or prebiotics intake. Fecal microbiota transplantation has emerged as a therapeutic strategy as well.

CONCLUSIONS

Nowadays, it is widely accepted that changes in the normal gut microbiome causing dysbiosis and immune dysregulation play a role gastroesophageal cancer. Different interventions, including probiotics and prebiotics intake are being developed to improve therapeutic outcomes and mitigate toxicities associated with anticancer treatment. Further studies are required in order to introduce the microbiome among the available tools of precision medicine in the field of anticancer treatment.

The interactions between traditional Chinese medicine and gut microbiota in cancers: Current status and future perspectives

The gut microbiota, known as the "forgotten organ" and "human second genome," comprises a complex microecosystem. It significantly influences the development of various tumors, including colorectal, liver, stomach, breast, and lung cancers, through both direct and indirect mechanisms. These mechanisms include the "gut-liver" axis, the "lung-intestine" axis, and interactions with the immune system. The intestinal flora exhibits dual roles in cancer, both promoting and suppressing its progression. Traditional Chinese medicine (TCM) can alter cancer progression by regulating the intestinal flora. It modifies the intestinal flora's composition and structure, along with the levels of endogenous metabolites, thus affecting the intestinal barrier, immune system, and overall body metabolism. These actions contribute to TCM's significant antitumor effects. Moreover, the gut microbiota metabolizes TCM components, enhancing their antitumor properties. Therefore, exploring the interaction between TCM and the intestinal flora offers a novel perspective in understanding TCM's antitumor mechanisms. This paper succinctly reviews the association between gut flora and the development of tumors, including colorectal, liver, gastric, breast, and lung cancers. It further examines current research on the interaction between TCM and intestinal flora, with a focus on its antitumor efficacy. It identifies limitations in existing studies and suggests recommendations, providing insights into antitumor drug research and exploring TCM's antitumor effectiveness. Additionally, this paper aims to guide future research on TCM and the gut microbiota in antitumor studies.

The Interplay Between Helicobacter pylori and Suppressors of Cytokine Signaling (SOCS) Molecules in the Development of Gastric Cancer and Induction of Immune Response

Helicobacter pylori (H. pylori) colonizes the stomach and leads to the secretion of a vast range of cytokines by infiltrated leukocytes directing immune/inflammatory response against the bacterium. To regulate immune/inflammatory responses, suppressors of cytokine signaling (SOCS) proteins bind to multiple signaling components located downstream of cytokine receptors, such as Janus kinase (JAK), signal transducers and activators of transcription (STAT). Dysfunctional SOCS proteins in immune cells may facilitate the immune evasion of H. pylori, allowing the bacteria to induce chronic inflammation. Dysregulation of SOCS expression and function can contribute to the sustained H. pylori-mediated gastric inflammation which can lead to gastric cancer (GC) development. Among SOCS molecules, dysregulated expression of SOCS1, SOCS2, SOCS3, and SOCS6 were indicated in H. pylori-infected individuals as well as in GC tissues and cells. H. pylori-induced SOCS1, SOCS2, SOCS3, and SOCS6 dysregulation can contribute to the GC development. The expression of SOCS molecules can be influenced by various factors, such as epigenetic DNA methylation, noncoding RNAs, and gene polymorphisms. Modulation of the expression of SOCS molecules in gastric epithelial cells and immune cells can be considered to control gastric carcinogenesis as well as regulate antitumor immune responses, respectively. This review aimed to explain the interplay between H. pylori and SOCS molecules in GC development and immune response induction as well as to provide insights regarding potential therapeutic strategies modulating SOCS molecules.

Inhibition of Wnt Signaling by Atovaquone Inhibits Gastric Cancer and Enhances Chemotherapy Effectiveness Through Activation of Casein Kinase 1α

Abnormal activation of the Wnt/β-catenin signaling pathway is a driving force behind the progression of gastric cancer. Atovaquone, known as an antimalarial drug, has emerged as a potential candidate for anti-cancer therapy. This study investigated atovaquone's effects on gastric cancer and its underlying mechanisms. Using gastric cancer cell lines, we found that atovaquone, at concentrations relevant to clinical use, significantly reduced their viability. Notably, atovaquone exhibited a lower effectiveness in reducing the viability of normal gastric cells compared to gastric cancer cells. We further demonstrated that atovaquone inhibited gastric cancer growth and colony formation. Mechanism studies revealed that atovaquone inhibited mitochondrial respiration and induced oxidative stress. Experiments using ρ0 cells, deficient in mitochondrial respiration, indicated a slightly weaker effect of atovaquone on inducing apoptosis compared to wildtype cells. Atovaquone increased phosphorylated β-catenin at Ser45 and Ser33/37/Thr41, elevated Axin, and reduced β-catenin. The inhibitory effects of atovaquone on β-catenin were reversed upon depletion of CK1α. Furthermore, the combination of atovaquone with paclitaxel suppressed gastric cancer growth and improved overall survival in mice. Given that atovaquone is already approved for clinical use, these findings suggest its potential as a valuable addition to the drug arsenal available for treating gastric cancer.

Intratumoral microbiota: implications for cancer onset, progression, and therapy

Significant advancements have been made in comprehending the interactions between the microbiome and cancer. However, prevailing research predominantly directs its focus toward the gut microbiome, affording limited consideration to the interactions of intratumoral microbiota and tumors. Within the tumor microenvironment (TME), the intratumoral microbiome and its associated products wield regulatory influence, directing the modulation of cancer cell properties and impacting immune system functionality. However, to grasp a more profound insight into the intratumoral microbiota in cancer, further research into its underlying mechanisms is necessary. In this review, we delve into the intricate associations between intratumoral microbiota and cancer, with a specific focus on elucidating the significant contribution of intratumoral microbiota to the onset and advancement of cancer. Notably, we provide a detailed exploration of therapeutic advances facilitated by intratumoral microbiota, offering insights into recent developments in this burgeoning field.

Role of lncRNAs in Helicobacter pylori and Epstein-Barr virus associated gastric cancers

Helicobacter pylori infection is a risk factor for the development of gastric cancer (GC), and the role of co-infection with viruses, such as Epstein-Barr virus, in carcinogenesis cannot be ignored. Furthermore, it is now known that genetic factors such as long non-coding RNAs (lncRNAs) are involved in many diseases, including GC. On the other side, they can also be used as therapeutic goals. Modified lncRNAs can cause aberrant expression of genes encoding proximal proteins, which are essential for the development of carcinoma. In this review, we present the most recent studies on lncRNAs in GC, concentrating on their roles in H. pylori and EBV infections, and discuss some of the molecular mechanisms of these GC-related pathogens. There was also a discussion of the research gaps and future perspectives.

Microbiota as the unifying factor behind the hallmarks of cancer

The human microbiota is a complex ecosystem that colonizes body surfaces and interacts with host organ systems, especially the immune system. Since the composition of this ecosystem depends on a variety of internal and external factors, each individual harbors a unique set of microbes. These differences in microbiota composition make individuals either more or less susceptible to various diseases, including cancer. Specific microbes are associated with cancer etiology and pathogenesis and several mechanisms of how they drive the typical hallmarks of cancer were recently identified. Although most microbes reside in the distal gut, they can influence cancer initiation and progression in distant tissues, as well as modulate the outcomes of established cancer therapies. Here, we describe the mechanisms by which microbes influence carcinogenesis and discuss their current and potential future applications in cancer diagnostics and management.

Wnt-Independent SARS-CoV-2 Infection in Pulmonary Epithelial Cells

The Wnt signaling pathway within host cells regulates infections by several pathogenic bacteria and viruses. Recent studies suggested that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection depends on β-catenin and can be inhibited by the antileprotic drug clofazimine. Since clofazimine has been identified by us as a specific inhibitor of Wnt/β-catenin signaling, these works could indicate a potential role of the Wnt pathway in SARS-CoV-2 infection. Here, we show that the Wnt pathway is active in pulmonary epithelial cells. However, we find that in multiple assays, SARS-CoV-2 infection is insensitive to Wnt inhibitors, including clofazimine, acting at different levels within the pathway. Our findings assert that endogenous Wnt signaling in the lung is unlikely required or involved in the SARS-CoV-2 infection and that pharmacological inhibition of this pathway with clofazimine or other compounds is not a universal way to develop treatments against the SARS-CoV-2 infection. IMPORTANCE The development of inhibitors of the SARS-CoV-2 infection remains a need of utmost importance. The Wnt signaling pathway in host cells is often implicated in infections by bacteria and viruses. In this work, we show that, despite previous indications, pharmacological modulation of the Wnt pathway does not represent a promising strategy to control SARS-CoV-2 infection in lung epithelia.

Helicobacter pylori and epithelial mesenchymal transition in human gastric cancers: An update of the literature

Gastric cancer, a multifactorial disease, is considered one of the most common malignancies worldwide. In addition to genetic and environmental risk factors, infectious agents, such as Epstein-Barr virus (EBV) and Helicobacter pylori (H.pylori) contribute to the onset and development of gastric cancer. H. pylori is a type I carcinogen that colonizes the gastric epithelium of approximately 50% of the world's population, thus increasing the risk of gastric cancer development. On the other hand, epithelial mesenchymal transition (EMT) is a fundamental process crucial to embryogenic growth, wound healing, organ fibrosis and cancer progression. Several studies associate gastric pathogen infection of the epithelium with EMT initiation, provoking cancer metastasis in the gastric mucosa through various molecular signaling pathways. Additionally, EMT is implicated in the progression and development of H. pylori-associated gastric cancer. In this review, we recapitulate recent findings elucidating the association between H. pylori infection in EMT promotion leading to gastric cancer progression and metastasis.

Infectious Agents Induce Wnt/β-Catenin Pathway Deregulation in Primary Liver Cancers

Interaction between infectious agents and liver tissue, as well as repeated and extreme biological events beyond adaptive capacities, may result in pathological conditions predisposing people to development of primary liver cancers (PLCs). In adults, PLCs mainly comprise hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA). Various infectious agents in the hepatic microenvironment can destabilize normal liver cell functions by modulating the Wnt/β-catenin pathway components. Among them, hepatotropic viruses B, C, and D are involved in Wnt/β-catenin signaling dysregulation. Other microbial agents, including oncogenic viruses such as Epstein-Barr virus (EBV) and human papilloma virus (HPV), bacteria, e.g., Mycoplasma hyorhinis and Salmonella Typhi, the protozoan parasite Toxoplasma gondii, the fungus Aspergillus flavus, and liver flukes such as Clonorchissinensis or Opisthorchis viverrini, may induce malignant transformation in hepatocytes or in target cells of the biliary tract through aberrant Wnt signaling activation. This review focuses on new insights into infectious agents implicated in the deregulation of Wnt signaling and PLC development. Since the Wnt/β-catenin pathway is a driver of cancer following viral and bacterial infections, molecules inhibiting the complex axis of Wnt signaling could represent novel therapeutic approaches in PLC treatment.

Comprehensive insight into altered host cell-signaling cascades upon Helicobacter pylori and Epstein-Barr virus infections in cancer

Cancer is characterized by mutagenic events that lead to disrupted cell signaling and cellular functions. It is one of the leading causes of death worldwide. Literature suggests that pathogens, mainly Helicobacter pylori and Epstein-Barr virus (EBV), have been associated with the etiology of human cancer. Notably, their co-infection may lead to gastric cancer. Pathogen-mediated DNA damage could be the first and crucial step in the carcinogenesis process that modulates numerous cellular signaling pathways. Altogether, it dysregulates the metabolic pathways linked with cell growth, apoptosis, and DNA repair. Modulation in these pathways leads to abnormal growth and proliferation. Several signaling pathways such RTK, RAS/MAPK, PI3K/Akt, NFκB, JAK/STAT, HIF1α, and Wnt/β-catenin are known to be altered in cancer. Therefore, this review focuses on the oncogenic roles of H. pylori, EBV, and its associated signaling cascades in various cancers. Scrutinizing these signaling pathways is crucial and may provide new insights and targets for preventing and treating H. pylori and EBV-associated cancers.

Cellular Senescence, Inflammation, and Cancer in the Gastrointestinal Tract

Due to modern medical advancements, greater proportions of the population will continue to age with longer life spans. Increased life span, however, does not always correlate with improved health span, and may result in an increase in aging-related diseases and disorders. These diseases are often attributed to cellular senescence, in which cells become disengaged from the cell cycle and inert to cell death. These cells are characterized by a proinflammatory secretome. The proinflammatory senescence-associated secretory phenotype, although part of a natural function intended to prevent further DNA damage, creates a microenvironment suited to tumor progression. This microenvironment is most evident in the gastrointestinal tract (GI), where a combination of bacterial infections, senescent cells, and inflammatory proteins can lead to oncogenesis. Thus, it is important to find potential senescence biomarkers as targets of novel therapies for GI diseases and disorders including cancers. However, finding therapeutic targets in the GI microenvironment to reduce the risk of GI tumor onset may also be of value. This review summarizes the effects of cellular senescence on GI aging, inflammation, and cancers, and aims to improve our understanding of these processes with a goal of enhancing future therapy.

Fusobacterium & Co. at the Stem of Cancer: Microbe-Cancer Stem Cell Interactions in Colorectal Carcinogenesis

Adult stem cells lie at the crossroads of tissue repair, inflammation, and malignancy. Intestinal microbiota and microbe-host interactions are pivotal to maintaining gut homeostasis and response to injury, and participate in colorectal carcinogenesis. Yet, limited knowledge is available on whether and how bacteria directly crosstalk with intestinal stem cells (ISC), particularly cancerous stem-like cells (CR-CSC), as engines for colorectal cancer initiation, maintenance, and metastatic dissemination. Among several bacterial species alleged to initiate or promote colorectal cancer (CRC), the pathobiont Fusobacterium Nucleatum has recently drawn significant attention for its epidemiologic association and mechanistic linkage with the disease. We will therefore focus on current evidence for an F. nucleatum-CRCSC axis in tumor development, highlighting the commonalities and differences between F. nucleatum-associated colorectal carcinogenesis and gastric cancer driven by Helicobacter Pylori. We will explore the diverse facets of the bacteria-CSC interaction, analyzing the signals and pathways whereby bacteria either confer "stemness" properties to tumor cells or primarily target stem-like elements within the heterogeneous tumor cell populations. We will also discuss the extent to which CR-CSC cells are competent for innate immune responses and participate in establishing a tumor-promoting microenvironment. Finally, by capitalizing on the expanding knowledge of how the microbiota and ISC crosstalk in intestinal homeostasis and response to injury, we will speculate on the possibility that CRC arises as an aberrant repair response promoted by pathogenic bacteria upon direct stimulation of intestinal stem cells.

RUNX3 Meets the Ubiquitin-Proteasome System in Cancer

RUNX3 is a transcription factor with regulatory roles in cell proliferation and development. While largely characterized as a tumor suppressor, RUNX3 can also be oncogenic in certain cancers. Many factors account for the tumor suppressor function of RUNX3, which is reflected by its ability to suppress cancer cell proliferation after expression-restoration, and its inactivation in cancer cells. Ubiquitination and proteasomal degradation represent a major mechanism for the inactivation of RUNX3 and the suppression of cancer cell proliferation. On the one hand, RUNX3 has been shown to facilitate the ubiquitination and proteasomal degradation of oncogenic proteins. On the other hand, RUNX3 can be inactivated through the ubiquitin-proteasome system. This review encapsulates two facets of RUNX3 in cancer: how RUNX3 suppresses cell proliferation by facilitating the ubiquitination and proteasomal degradation of oncogenic proteins, and how RUNX3 is degraded itself through interacting RNA-, protein-, and pathogen-mediated ubiquitination and proteasomal degradation.

CDK1 bridges NF-κB and β-catenin signaling in response to H. pylori infection in gastric tumorigenesis

Infection with Helicobacter pylori (H. pylori) is the main risk factor for gastric cancer, a leading cause of cancer-related death worldwide. The oncogenic functions of cyclin-dependent kinase 1 (CDK1) are not fully understood in gastric tumorigenesis. Using public datasets, quantitative real-time PCR, western blot, and immunohistochemical (IHC) analyses, we detect high levels of CDK1 in human and mouse gastric tumors. H. pylori infection induces activation of nuclear factor κB (NF-κB) with a significant increase in CDK1 in in vitro and in vivo models (p < 0.01). We confirm active NF-κB binding sites on the CDK1 promoter sequence. CDK1 phosphorylates and inhibits GSK-3β activity through direct binding with subsequent accumulation and activation of β-catenin. CDK1 silencing or pharmacologic inhibition reverses these effects and impairs tumor organoids and spheroid formation. IHC analysis demonstrates a positive correlation between CDK1 and β-catenin. The results demonstrate a mechanistic link between infection, inflammation, and gastric tumorigenesis where CDK1 plays a critical role.

Gut Microbiota in Colorectal Cancer: Biological Role and Therapeutic Opportunities

Colorectal cancer (CRC) is the second-leading cause of cancer-related deaths worldwide. While CRC is thought to be an interplay between genetic and environmental factors, several lines of evidence suggest the involvement of gut microbiota in promoting inflammation and tumor progression. Gut microbiota refer to the ~40 trillion microorganisms that inhabit the human gut. Advances in next-generation sequencing technologies and metagenomics have provided new insights into the gut microbial ecology and have helped in linking gut microbiota to CRC. Many studies carried out in humans and animal models have emphasized the role of certain gut bacteria, such as Fusobacterium nucleatum, enterotoxigenic Bacteroides fragilis, and colibactin-producing Escherichia coli, in the onset and progression of CRC. Metagenomic studies have opened up new avenues for the application of gut microbiota in the diagnosis, prevention, and treatment of CRC. This review article summarizes the role of gut microbiota in CRC development and its use as a biomarker to predict the disease and its potential therapeutic applications.

Molecular mechanisms underlying the action of carcinogens in gastric cancer with a glimpse into targeted therapy

BACKGROUND

Gastric cancer imposes a substantial global health burden despite its overall incidence decrease. A broad spectrum of inherited, environmental and infectious factors contributes to the development of gastric cancer. A profound understanding of the molecular underpinnings of gastric cancer has lagged compared to several other tumors with similar incidence and morbidity rates, owing to our limited knowledge of the role of carcinogens in this malignancy. The International Agency for Research on Cancer (IARC) has classified gastric carcinogenic agents into four groups based on scientific evidence from human and experimental animal studies. This review aims to explore the potential comprehensive molecular and biological impacts of carcinogens on gastric cancer development and their interactions and interferences with various cellular signaling pathways.

CONCLUSIONS

In this review, we highlight recent clinical trial data reported in the literature dealing with different ways to target various carcinogens in gastric cancer. Moreover, we touch upon other multidisciplinary therapeutic approaches such as surgery, adjuvant and neoadjuvant chemotherapy. Rational clinical trials focusing on identifying suitable patient populations are imperative to the success of single-agent therapeutics. Novel insights regarding signaling pathways that regulate gastric cancer can potentially improve treatment responses to targeted therapy alone or in combination with other/conventional treatments. Preventive strategies such as control of H. pylori infection through eradication or immunization as well as dietary habit and lifestyle changes may reduce the incidence of this multifactorial disease, especially in high prevalence areas. Further in-depth understanding of the molecular mechanisms involved in the role of carcinogenic agents in gastric cancer development may offer valuable information and update state-of-the-art resources for physicians and researchers to explore novel ways to combat this disease, from bench to bedside. A schematic outlining of the interaction between gastric carcinogenic agents and intracellular pathways in gastric cancer H. pylori stimulates multiple intracellular pathways, including PI3K/AKT, NF-κB, Wnt, Shh, Ras/Raf, c-MET, and JAK/STAT, leading to epithelial cell proliferation and differentiation, apoptosis, survival, motility, and inflammatory cytokine release. EBV can stimulate intracellular pathways such as the PI3K/Akt, RAS/RAF, JAK/STAT, Notch, TGF-β, and NF-κB, leading to cell survival and motility, proliferation, invasion, metastasis, and the transcription of anti-apoptotic genes and pro-inflammatory cytokines. Nicotine and alcohol can lead to angiogenesis, metastasis, survival, proliferation, pro-inflammatory, migration, and chemotactic by stimulating various intracellular signaling pathways such as PI3K/AKT, NF-κB, Ras/Raf, ROS, and JAK/STAT. Processed meat contains numerous carcinogenic compounds that affect multiple intracellular pathways such as sGC/cGMP, p38 MAPK, ERK, and PI3K/AKT, leading to anti-apoptosis, angiogenesis, metastasis, inflammatory responses, proliferation, and invasion. Lead compounds may interact with multiple signaling pathways such as PI3K/AKT, NF-κB, Ras/Raf, DNA methylation-dependent, and epigenetic-dependent, leading to tumorigenesis, carcinogenesis, malignancy, angiogenesis, DNA hypermethylation, cell survival, and cell proliferation. Stimulating signaling pathways such as PI3K/Akt, RAS/RAF, JAK/STAT, WNT, TGF-β, EGF, FGFR2, and E-cadherin through UV ionizing radiation leads to cell survival, proliferation, and immortalization in gastric cancer. The consequence of PI3K/AKT, NF-κB, Ras/Raf, ROS, JAK/STAT, and WNT signaling stimulation by the carcinogenic component of Pickled vegetables and salted fish is the Warburg effect, tumorigenesis, angiogenesis, proliferation, inflammatory response, and migration.

DNMT1 Gene Expression in Patients with Helicobacter pylori Infection

DNMT1, as a critical enzyme affecting epigenetics through methylation of DNA cytosine-rich sequences, regulates gene expression. Exterior factors including long-term infections, in this study Helicobacter pylori infection, could change host cells' epigenetics by affecting DNMT1 gene expression. This study investigated the statistical correlation between H. pylori virulence genes and DNMT1 gene expression in gastric antral epithelial cells of gastric adenocarcinoma and gastritis patients. In a case-control study, 50 and 53 gastritis and gastric adenocarcinoma antral biopsies, including 23 and 21 patients with H. pylori infection, respectively, were collected from hospitals in the west of Iran. Having extracted total RNA from gastric biopsy samples, cDNA was synthesized and virulence genes of H. pylori were detected by using the PCR method. Relative real-time RT PCR was used to detect ΔΔCt fold changes of the DNMT1 gene expression in divided groups of patients based on H. pylori infection and clinical manifestations. The results showed that along with increasing patients' age, the DNMT1 gene expression will increase in gastric antral epithelial cells of gastric cancer patients (P ≤ 0.05). On the other hand, the biopsy samples with infection of H. pylori cagA, cagY, and cagE genotypes revealed a direct correlation along with increased DNMT1 gene expression. This study revealed the correlations of H. pylori cag pathogenicity island genes with increased DNMT1 gene expression.

Relationships among microbiota, gastric cancer, and immunotherapy

Currently, conventional neoadjuvant therapy or postoperative adjuvant therapy, such as chemotherapy and radiation therapy, can only bring limited survival benefits to gastric cancer (GC). Median survival after palliative chemotherapy is also low, at about 8–10 months. Immunotargeting is a new option for the treatment of GC, but has not been widely replicated. The highly immunosuppressed tumor microenvironment (TME) discounts the efficacy of immunotherapy for GC. Therefore, new strategies are needed to enhance the immune response of the TME. This paper reviewed the relationship between microorganisms and GC, potential links between microorganisms and immunotherapy and research of microorganisms combined immunotherapy.

TNF-α-inducing protein of Helicobacter pylori promotes EMT and cancer stem-like cells properties via activation of Wnt/β-catenin signaling pathway in gastric cancer cells

Tumor necrosis factor-α-inducing protein (Tipα) is a newly identified toxin, which promotes the inflammation and carcinogenesis caused by Helicobacter pylori (H. pylori). However, its mechanism of pathogenesis is still unclear. To investigate the carcinogenic mechanisms of Tipα, SGC7901 cells and SGC7901-derived cancer stem-like cells (CSCs) were stimulated by recombinant Tipα protein with or without Wnt/β-catenin signaling inhibitor XAV939. qRT-PCR and Western blotting were employed to detect expression of epithelial-mesenchymal transition (EMT), CSCs markers, and downstream target genes of this signaling pathway. The cell migration ability was measured by wound healing assay and transwell assay. Our results indicated that Tipα promoted CSC properties of SGC7901 spheroids, including increased expression of CSC specific surface markers CD44, Oct4, Nanog, and an increased capacity for self-renewal. Tipα activated Wnt/β-catenin signaling in both SGC7901 cells or CSCs. Furthermore, Tipα induced the EMT and increased the expressions of downstream target genes of this signaling, including c-myc, cyclin D1, and CD44. However, XAV939 pretreatment inhibited Tipα-induced EMT and CSC properties in SGC7901 cells or CSCs. These results suggest that Tipα promotes EMT and CSC-like properties in gastric cancer cells through activation of Wnt/β-catenin signaling pathway, thereby accelerating the progression of gastric cancer.

Helicobacter pylori infection activates Wnt/β-catenin pathway to promote the occurrence of gastritis by upregulating ASCL1 and AQP5

Helicobacter pylori (H. pylori) infection is a well-recognized contributing factor to gastritis, but the underlying mechanisms remain to be established. It is interesting to note that AQP5 was predicted to be highly expressed in intestinal metaplasia (IM) based on H. pylori infection-related microarray data, and the transcription factor ASCL1 was bioinformatically predicted to associate with AQP5. Therefore, the purpose of this study is to evaluate the mechanistic significance of ASCL1 and AQP5 in H. pylori infection of gastritis. Gastritis mouse models were established by H. pylori infection, followed by determination of AQP5 and ASCL1 in gastric mucosa. Besides, the effects of AQP5 on H. pylori-induced gastritis were explored using AQP5^-/- mice. It was observed that H. pylori infection elevated expression of AQP5 and ASCL1 in gastric mucosa and gastric epithelial cells (GECs). H. pylori induced AQP5 expression by regulating ASCL1 and activated WNT/β-catenin signaling pathway in GECs. It was also found that AQP5 knockdown suppressed inflammatory response and apoptosis in H. pylori-infected mice. Moreover, H. pylori infection-elevated ASCL1 and AQP5 expression promoted apoptosis and inflammation in GECs. Taken together, the key findings of the present study demonstrate that H. pylori infection activated WNT/β-catenin signaling pathway by upregulating ASCL1/AQP5 to induce gastritis.

Helicobacter pylori-induced RASAL2 Through Activation of Nuclear Factor-κB Promotes Gastric Tumorigenesis via β-catenin Signaling Axis

BACKGROUND & AIMS

Helicobacter pylori infection is the predominant risk factor for gastric cancer. RAS protein activator like 2 (RASAL2) is considered a double-edged sword in carcinogenesis. Herein, we investigated the role of RASAL2 in response to H pylori infection and gastric tumorigenesis.

METHODS

Bioinformatics analyses of local and public databases were applied to analyze RASAL2 expression, signaling pathways, and clinical significance. In vitro cell culture, spheroids, patient-derived organoids, and in vivo mouse models were used. Molecular assays included chromatin immunoprecipitation, co-immunoprecipitation, Western blotting, quantitative polymerase chain reaction, and immunocyto/histochemistry.

RESULTS

H pylori infection induced RASAL2 expression via a nuclear factor-κB (NF-κB)-dependent mechanism whereby NF-κB was directly bound to the RASAL2 promoter activating its transcription. By gene silencing and ectopic overexpression, we found that RASAL2 upregulated β-catenin transcriptional activity. RASAL2 inhibited protein phosphatase 2A activity through direct binding with subsequent activation of the AKT/β-catenin signaling axis. Functionally, RASAL2 silencing decreased nuclear β-catenin levels and impaired tumor spheroids and organoids formation. Furthermore, the depletion of RASAL2 impaired tumor growth in gastric tumor xenograft mouse models. Clinicopathological analysis indicated that abnormal overexpression of RASAL2 correlated with poor prognosis and chemoresistance in human gastric tumors.

CONCLUSIONS

These studies uncovered a novel signaling axis of NF-κB/RASAL2/β-catenin, providing a novel link between infection, inflammation and gastric tumorigenesis.

Silencing of Nudix type 5 represses proliferation and invasion and enhances chemosensitivity of gastric carcinoma cells by affecting the AKT/GSK-3β/β-catenin pathway

Nudix type 5 (NUDT5) has been recently identified as a new cancer-associated protein that is involved in numerous cancers. To date, the relationship between NUDT5 and gastric carcinoma has not been addressed. In the current research, we focused on exploring the potential relevance of NUDT5 in gastric carcinoma. The initial analysis of NUDT5 expression in gastric carcinoma by TCGA data revealed a clear increase in NUDT5 expression in tumor versus normal tissue. The increased expression of NUDT5 was also validated in the clinical specimens of gastric carcinoma by immunoblotting detection. Moreover, high NUDT5 levels predicted a poorer overall survival in gastric carcinoma patients. A series of cellular functional assays demonstrated that gastric carcinoma cells with silenced NUDT5 exhibited decreased proliferative and invasive ability, increased cell cycle arrest at the G0/G1 phase, and enhanced chemosensitivity. In-depth research showed that the silencing of NUDT5 led to a reduction in the activation of AKT and β-catenin. The reactivation of AKT blocked the repressive effect of NUDT5 silencing on β-catenin activation. The forced expression of β-catenin also reversed NUDT5-silencing-mediated anticancer effects. A Xenograft tumor assay confirmed the anticancer role of NUDT5 in gastric carcinoma in vivo. In short, these findings reveal elevated NUDT5 levels in gastric carcinoma and demonstrate that the inhibition of NUDT5 displays promising anticancer effects by affecting the AKT/β-catenin pathway. Thus, our work unveils a vital role of NUDT5 in gastric carcinoma and indicates it as a viable candidate target for anticancer drug discovery.

Proteolytic Landscapes in Gastric Pathology and Cancerogenesis

Gastric cancer is a leading cause of cancer-related death, and a large proportion of cases are inseparably linked to infections with the bacterial pathogen and type I carcinogen Helicobacter pylori. The development of gastric cancer follows a cascade of transformative tissue events in an inflammatory environment. Proteases of host origin as well as H. pylori-derived proteases contribute to disease progression at every stage, from chronic gastritis to gastric cancer. In the present article, we discuss the importance of (metallo-)proteases in colonization, epithelial inflammation, and barrier disruption in tissue transformation, deregulation of cell proliferation and cell death, as well as tumor metastasis and neoangiogenesis. Proteases of the matrix metalloproteinase (MMP) and a disintegrin and metalloproteinase domain-containing protein (ADAM) families, caspases, calpain, and the H. pylori proteases HtrA, Hp1012, and Hp0169 cleave substrates including extracellular matrix molecules, chemokines, and cytokines, as well as their cognate receptors, and thus shape the pathogenic microenvironment. This review aims to summarize the current understanding of how proteases contribute to disease progression in the gastric compartment.

Infection with a hypervirulent strain of Helicobacter pylori primes gastric cells toward intestinal transdifferentiation

BACKGROUND

Intestinal metaplasia, gastric-to-intestinal transdifferentiation, occurs as a result of the misexpression of certain regulatory factors, leading to genetic reprogramming. Here, we have evaluated the H. pylori-induced expression patterns of these candidate genes.

METHODS

The expression levels of 1) tissue-specific transcription factors (RUNX3, KLF5, SOX2, SALL4, CDX1 and CDX2), 2) stemness factors (TNFRSF19, LGR5, VIL1) and 3) tissue-specific mucins (MUC5AC, MUC2) were evaluated by quantitative real-time PCR in gastric primary cells (GPCs), in parallel with two gastric cancer (MKN45 and AGS) cell lines, up to 96h following H. pylori infection.

RESULTS

Following H. pylori infection of GPCs, RUNX3 declined at 24h post infection (-6.2 ± 0.3) and remained downregulated for up to 96h. Subsequently, overexpression of self-renewal and pluripotency transcription factors, KLF5 (3.6 ± 0.2), SOX2 (7.6 ± 0.5) and SALL4 (4.3 ± 0.2) occurred. The expression of TNFRSF19 and LGR5, demonstrated opposing trends, with an early rise of the former (4.5 ± 0.3) at 8h, and a simultaneous fall of the latter (-1.8 ± 0.5). This trend was reversed at 96h, with the decline in TNFRSF19 (-5.5 ± 0.2), and escalation of LGR5 (2.6 ± 0.2) and VIL1 (1.8 ± 0.3). Ultimately, CDX1 and CDX2 were upregulated by 1.9 and 4.7-fold, respectively. The above scenario was, variably observed in MKN45 and AGS cells.

CONCLUSION

Our data suggests an interdependent gene regulatory network, induced by H. pylori infection. This interaction begins with the downregulation of RUNX3, upregulation of self-renewal and pluripotency transcription factors, KLF5, SOX2 and SALL4, leading to the downregulation of TNFRSF19, upregulation of LGR5 and aberrant expression of intestine-specific transcription factors, potentially facilitating the process of gastric-to-intestinal transdifferentiation.

Inhibitory Effect of Astaxanthin on Gene Expression Changes in Helicobacter pylori-Infected Human Gastric Epithelial Cells

Helicobacter pylori (H. pylori) infection promotes gastric carcinogenesis by increasing oxidative stress, inflammation, and dysregulation of cell survival and proliferation of gastric epithelial cells. Astaxanthin (ASTX), a bioactive carotenoid, exhibits antioxidant and anticancer effects by modulating aberrant signaling pathways that lead to dysregulation of cell death and proliferation. To elucidate the molecular mechanism of H. pylori-induced gastric carcinogenesis and to examine the inhibitory effect of ASTX on H. pylori-induced gastric epithelial cell gene expression changes, we performed comparative RNA-sequencing (RNA-Seq) analysis for H. pylori-infected gastric epithelial cells treated with or without ASTX. RNA-Seq results reveal that differentially expressed genes (DEGs) in H. pylori-infected cells were mainly associated with the Wnt/β-catenin signaling pathway, which is related to cell proliferation. ASTX significantly reversed H. pylori-induced transcriptional alterations of the key mediators involved in β-catenin signaling, notably, porcupine (gene symbol, PORCN), spermine oxidase (SMOX), bone morphogenetic protein (BMP) and activin membrane-bound inhibitor (BAMBI), SMAD family member 4 (SMAD4), transforming growth factor-β1 (TGFB1), Fos-like 1 (FOSLI), and c-myc (MYC). We suggest that ASTX may be a potential therapeutic agent that can suppress H. pylori-induced proliferation-associated gene expression changes, in part, by counter-regulating the Wnt/β-catenin signaling pathway.

Interplay and cooperation of Helicobacter pylori and gut microbiota in gastric carcinogenesis

Chronic Helicobacter pylori infection is a critical risk factor for gastric cancer (GC). However, only 1–3 % of people with H. pylori develop GC. In gastric carcinogenesis, non-H. pylori bacteria in the stomach might interact with H. pylori. Bacterial dysbiosis in the stomach can strengthen gastric neoplasia development via generating tumor-promoting metabolites, DNA damaging, suppressing antitumor immunity, and activating oncogenic signaling pathways. Other bacterial species may generate short-chain fatty acids like butyrate that may inhibit carcinogenesis and inflammation in the human stomach. The present article aimed at providing a comprehensive overview of the effects of gut microbiota and H. pylori on the development of GC. Next, the potential mechanisms of intestinal microbiota were discussed in gastric carcinogenesis. We also disserted the complicated interactions between H. pylori, intestinal microbiota, and host in gastric carcinogenesis, thus helping us to design new strategies for preventing, diagnosing, and treating GC.

Emerging therapeutic targets for gastric cancer from a host-Helicobacter pylori interaction perspective

INTRODUCTION

Gastric cancer (GC) has the higher genetic, cytologic, and architectural heterogeneity compared to other gastrointestinal cancers. By inducing gastric inflammation, Helicobacter pylori (HP) may lead to GC through combining bacterial factors with host factors. In this regard, identification of the major therapeutic targets against the host-HP interactions plays a critical role in GC prevention, diagnosis, and treatment.

AREAS COVERED

This study offers new insights into the promising therapeutic targets against the angiogenesis, invasion, or metastasis of GC from a host-HP interaction perspective. To this end, MEDLINE, EMBASE, LILACS, AIM, and IndMed databases were searched for relevant articles since 1992.

EXPERT OPINION

Wnt signaling and COX pathway have a well-documented history in the genesis of GC by HP and might be considered as the most promising targets for early GC treatment. Destroying HP may decrease the risk of GC, but it cannot fully hinder the GC development induced by HP infection. Therefore, targeting HP-activated pathways, especially COX-2/Wnt/beta-catenin/VEGF, TLR2/TLR9/COX-2, COX2-PGE2, and NF-κB/COX-2, as well as EPHA2, MMPs, and miR-543/SIRT1 axis, can be an effective measure in the early treatment of GC. However, different clinical trials and large, multi-center cohorts are required to validate these potentially effective targets for GC therapy.

Trefoil Factor 1 Suppresses Epithelial-mesenchymal Transition through Inhibition of TGF-beta Signaling in Gastric Cancer Cells

Gastric cancer is a malignancy with high incidence and mortality worldwide. In gastric cancer, epithelial-mesenchymal transition (EMT) and metastasis further increase the mortality rate. Trefoil factor 1 (TFF1) has been reported as a protective factor in the gastric mucosa. In this study, TFF1 inhibited the migration and invasive capability of gastric cancer cells. Elevated TFF1 levels induced the expression of E-cadherin, the epithelial marker, and reduced the expression of N-cadherin, vimentin, Snail, Twist, Zinc finger E-box binding homeobox (ZEB) 1 and ZEB2, well-known repressors of E-cadherin expression. In addition, the expression of matrix metalloproteinase (MMP)-2, MMP-7 and MMP-9, which are major markers of cancer metastasis, was suppressed by TFF1. Upregulation of TFF1 inhibited TGF-β, a major signaling for EMT induction, and the phosphorylation of Smad2/3 activated by TGF-β in AGS cells. In conclusion, TFF1 inhibits EMT through suppression of TGF-β signaling in AGS cells, which might be used in therapeutic strategies for reducing metastatic potential and invasiveness of these cells.

Dual activation of Hedgehog and Wnt/β-catenin signaling pathway caused by downregulation of SUFU targeted by miRNA-150 in human gastric cancer

Mounting evidence has shown that miRNA-150 expression is upregulated in gastric cancer (GC) and is associated with gastric carcinogenesis, but the underlying oncogenic mechanism remains elusive. Here, we discovered that miRNA-150 targets the tumor suppressor SUFU to promote cell proliferation, migration, and the epithelial-mesenchymal transition (EMT) via the dual activation of Hedgehog (Hh) and Wnt signaling. MiRNA-150 was highly expressed in GC tissues and cell lines, and the level of this miRNA was negatively related to that of SUFU. In addition, both the miRNA-150 and SUFU levels were associated with tumor differentiation. Furthermore, miRNA-150 activated GC cell proliferation and migration in vitro. We found that miRNA-150 inhibitors repressed not only Wnt signaling by promoting cytoplasmic β-catenin localization, but also repressed Hh signaling and EMT. MiRNA-150 inhibition also resulted in significant tumor volume reductions in vivo, suggesting the potential application of miRNA-150 inhibitors in GC therapy. The expression of genes downstream of Hh and Wnt signaling was also reduced in tumors treated with miRNA-150 inhibitors. Notably, anti-SUFU siRNAs rescued the inhibitory effects of miRNA-150 inhibitors on Wnt signaling, Hh activation, EMT, cell proliferation, cell migration, and colony formation. Taken together, these findings indicate that miRNA-150 is oncogenic and promotes GC cell proliferation, migration, and EMT by activating Wnt and Hh signaling via the suppression of SUFU expression.

MiRNA-20b/SUFU/Wnt axis accelerates gastric cancer cell proliferation, migration and EMT

Previous research has found that miRNA-20b is highly expressed in gastric cancer (GC), however, its function and underlying mechanism are not clear. Wnt signaling pathway, implicated in tumorigeneisis, is activated in more than 30% of GC. We would like to characterize the biological behavior of miRNA-20b in terms of modulating Wnt/β-catenin signaling and EMT. We showed that miRNA-20b inhibitors suppressed Topflash/Fopflash dependent luciferase activity and the β-catenin nuclear translocation, resulting in inhibition of Wnt pathway activity and EMT. SUFU, negatively regulating Wnt and Hedgehog signaling pathway, was proved to be targeted by miRNA-20b. Moreover, additional knockdown of SUFU alleviated the inhibitory effect on Wnt pathway activity, EMT, cell proliferation/migration and colony formation caused by miRNA-20b inhibition. In summary, miRNA-20b is an oncogenic miRNA and promoted cell proliferation, migration and EMT in GC partially by activating Wnt pathway via targeting SUFU.

Rola miRNA w rozwoju wybranych nowotworów – potencjalne zastosowanie w diagnostyce*

MikroRNA (miRNA) są małymi cząsteczkami kwasu rybonukleinowego, które mimo że nie podlegają procesowi translacji, pełnią ważną funkcję regulacyjną w komórkach eukariotycznych. Ich fizjologiczną funkcją jest utrzymywanie homeostazy komórek. Zaburzona ekspresja miRNA może spowodować rozwój wielu chorób, w tym chorób nowotworowych. Działanie miRNA polega na hamowaniu tworzenia się białek, w tym białek o właściwościach onkogennych i antyonkogennych. Mutacje w miejscach kodowania miRNA mogą prowadzić do nadmiernego lub zmniejszonego wytwarzania wspomnianych białek. Odkrycie miRNA i poznanie ich roli w komórce otworzyło nowe możliwości dla diagnostyki chorób nowotworowych. Zmiany poziomu odpowiednich miRNA, w krwiobiegu lub innych płynach ustrojowych, mogą być markerem diagnostycznym chorób. Diagnostyka onkologiczna mogłaby przebiegać na podstawie badań profilu miRNA pacjenta i porównania go z opracowanymi wcześniej profilami zmian miRNA powiązanymi z występowaniem danego rodzaju choroby nowotworowej. Informacja o zmianach profilu miRNA podstawowych w regulacji ekspresji genów związanych z procesami nowotworzenia, mogłaby się przyczynić do opracowania terapii eksperymentalnych opartych na przywróceniu pierwotnego poziomu miRNA w komórkach, a tym samym, na przywróceniu prawidłowej regulacji ekspresji genów. Coraz nowsze metody wyciszania i włączania ekspresji miRNA mogą w przyszłości zaowocować skutecznymi rozwiązaniami terapeutycznymi.

Helicobacter pylori-Mediated Immunity and Signaling Transduction in Gastric Cancer

Helicobacter pylori infection is a leading cause of gastric cancer, which is the second-most common cancer-related death in the world. The chronic inflammatory environment in the gastric mucosal epithelia during H. pylori infection stimulates intracellular signaling pathways, namely inflammatory signals, which may lead to the promotion and progression of cancer cells. We herein report two important signal transduction pathways, the LPS-TLR4 and CagA-MET pathways. Upon H. pylori stimulation, lipopolysaccharide (LPS) binds to toll-like receptor 4 (TLR4) mainly on macrophages and gastric epithelial cells. This induces an inflammatory response in the gastric epithelia to upregulate transcription factors, such as NF-κB, AP-1, and IRFs, all of which contribute to the initiation and progression of gastric cancer cells. Compared with other bacterial LPSs, H. pylori LPS has a unique function of inhibiting the mononuclear cell (MNC)-based production of IL-12 and IFN-γ. While this mechanism reduces the degree of inflammatory reaction of immune cells, it also promotes the survival of gastric cancer cells. The HGF/SF-MET signaling plays a major role in promoting cellular proliferation, motility, migration, survival, and angiogenesis, all of which are essential factors for cancer progression. H. pylori infection may facilitate MET downstream signaling in gastric cancer cells through its CagA protein via phosphorylation-dependent and/or phosphorylation-independent pathways. Other signaling pathways involved in H. pylori infection include EGFR, FAK, and Wnt/β-Catenin. These pathways function in the inflammatory process of gastric epithelial mucosa, as well as the progression of gastric cancer cells. Thus, H. pylori infection-mediated chronic inflammation plays an important role in the development and progression of gastric cancer.

Effects of a Potential Probiotic Strain Lactobacillus gasseri ATCC 33323 on Helicobacter pylori-Induced Inflammatory Response and Gene Expression in Coinfected Gastric Epithelial Cells

In the present study, we aimed to investigate the modulatory effects of a potential probiotic bacterium Lactobacillus gasseri ATCC 33323 on Helicobacter pylori-induced inflammatory response and gene expression in human gastric adenocarcinoma (AGS) cell line. The gastric epithelial cells were coinfected with a collection of H. pylori clinical strains alone or in combination with L. gasseri at a multiplicity of infection (MOI) of 1:100 for each bacterium, and incubated for different time points of 3, 6, and 12 h. IL-8 secretion from coinfected AGS cells after incubation at each time point was measured by an enzyme-linked immunosorbent assay (ELISA). The mRNA expression of IL-8, Bcl-2, β-catenin, integrin α₅, and integrin β₁ genes was determined by quantitative RT-PCR amplification of total RNA extracted from coinfected epithelial cells. L. gasseri significantly (P < 0.05 and P < 0.01) decreased the production of IL-8 in AGS cells coinfected with H. pylori strains at 6 h post-infection. We also detected that L. gasseri significantly (P < 0.05) down-regulated the gene expression level of IL-8 in H. pylori-stimulated AGS cells after 6 and 12 h of coinfection. Similarly, L. gasseri caused a significant decrease (P < 0.05) in mRNA expression of Bcl-2, β-catenin, integrin α₅, and integrin β₁ genes in AGS cells at 3 and 6 h after infection with H. pylori strains as compared with non-infected control cells. In conclusion, our results demonstrated that L. gasseri ameliorates H. pylori-induced inflammation and could be developed as a supplementation to the current treatment regimens administrated against H. pylori infection.

SUFU mediates EMT and Wnt/β-catenin signaling pathway activation promoted by miRNA-324-5p in human gastric cancer

The poor prognosis of late gastric carcinomas (GC) underscores the necessity to identify novel biomarkers for earlier diagnosis and effective therapeutic targets. MiRNA-324-5p has been shown to be over-expressed in GC, however the biological function of miRNA-324-5p implicated in gastric cancer and its downstream targets were not well understood. Wnt/β-catenin signaling pathway is aberrantly regulated in GC. We sought to explore if miRNA-324-5p promotes oncogenesis through modulating Wnt signaling and EMT. MiRNA-324-5p is highly expressed in GC based on qRT-PCR and TCGA data. In addition, in vitro cell proliferation, cell migration assays and in vivo animal exenograft were executed to show that miRNA-324-5p is an oncogenic miRNA in GC. MiRNA-324-5p activates Wnt signaling and induces EMT in GC. Further, SUFU was identified as a target of miRNA-324-5p confirmed by western blotting and luciferase assays. Spearson analysis and TCGA data indicate that the expression of SUFU is negatively associated with the expression of miRNA-324-5p. Rescue experiments were performed to determine if SUFU mediates the Wnt activation, EMT and oncogenic function of miRNA-324-5p. MiRNA-324-5p inhibitors plus SUFU siRNAs rescue partially the inhibitory effect on Wnt signaling and EMT caused by miRNA-324-5p inhibitors. Finally, the suppression of cell proliferation, migration, and colony formation ability induced by miRNA-324-5p inhibitors is alleviated by addition of SUFU siRNAs. In summary, miRNA-324-5p is overexpressed in vivo and exerts cell growth and migration-promoting effects through activating Wnt signaling and EMT by targeting SUFU in GC. It represents a potential miRNA with an oncogenic role in human gastric cancer.

MetaDE-Based Analysis of circRNA Expression Profiles Involved in Gastric Cancer

BACKGROUND

Circular RNAs (circRNAs) could play carcinogenic roles in gastric cancer (GC) and have potential to be biomarkers for GC early diagnosis, which needs to be further excavated and supported by more evidence.

AIMS

The study aims to identify more authentic circRNA expression profiles that could function as potential biomarkers in GC.

METHODS

circRNA expression data in three microarrays were downloaded from Gene Expression Omnibus datasets. A systematic meta-analysis based on an integrated dataset pre-processed from the three microarrays was conducted to identify a panel of differentially expressed circRNAs (DEcircs) by using the metaDE package. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes term enrichment were used to note the corresponding functions of DEcircs. Quantitative real-time polymerase chain reaction was applied to verify the DEcircs expression in cancer tissues and adjacent paracancerous tissues. A GC risk-related circRNAs-miRNAs-mRNAs network was further constructed and analyzed.

RESULTS

MetaDE analysis suggested 64 DEcircs between cancer tissues and adjacent normal tissues. GO and KEGG analysis showed that the parental genes of these DEcircs were mainly associated with histone methylation, Wnt signalosome and histone methylation activity. Hsa_circ_0005927 and hsa_circ_0067934 were verified in GC tissues, and a GC risk-related network was constructed.

CONCLUSION

MetaDE-based circRNA expression profiles revealed a series of potential biomarkers involved in GC. Two circRNAs, hsa_circ_0005927 and hsa_circ_0067934, could be more authentic biomarkers for GC screening. The GC risk-related network of hsa_circ_0005927/hsa_circ_0067934 and their downstream targets will provide new genetic insights for GC research.

miRNA-192 and -215 activate Wnt/β-catenin signaling pathway in gastric cancer via APC

Although great progress has been made in surgical techniques, traditional radiotherapy, and chemotherapy, gastric cancer (GC) is still the most common malignant tumor and has a high mortality, which highlights the importance of novel diagnostic markers. Emerging studies suggest that different microRNAs (miRNAs) are involved in tumorigenesis of GC. In this study, we found that miRNA-192 and -215 are significantly upregulated in GC and promote cell proliferation and migration. Adenomatous polyposis coli (APC), a well-known negative regulator in Wnt signaling, has been proved to be a target of miRNA-192 and -215. Inhibition of miRNA-192 or -215 reduced the Topflash activities and repressed the expression of Wnt signaling pathway proteins, while APC small interfering RNAs reversed the inhibitory effects, suggesting that miRNA-192 and -215 activate Wnt signaling via APC. In addition, APC mediates the cell proliferation and migration regulated by miRNA-192 and -215. Furthermore, APC is downregulated in GC tissues and negatively correlated with the expression of miRNA-192 and -215. In summary, miRNA-192 and -215 target APC and function as oncogenic miRNAs by activating Wnt signaling in GC, revealing to be potential therapeutic targets.

Gastric Damage and Cancer-Associated Biomarkers in Helicobacter pylori-Infected Children

Helicobacter pylori (H. pylori) is well-known to be involved in gastric carcinogenesis, associated with deregulation of cell proliferation and epigenetic changes in cancer-related genes. H. pylori infection is largely acquired during childhood, persisting long-term in about half of infected individuals, a subset of whom will go on to develop peptic ulcer disease and eventually gastric cancer, however, the sequence of events leading to disease is not completely understood. Knowledge on carcinogenesis and gastric damage-related biomarkers is abundant in adult populations, but scarce in children. We performed an extensive literature review focusing on gastric cancer related biomarkers identified in adult populations, which have been detected in children infected with H. pylori. Biomarkers were related to expression levels (RNA or protein) and/or methylation levels (DNA) in gastric tissue or blood of infected children as compared to non-infected controls. In this review, we identified 37 biomarkers of which 24 are over expressed, three are under expressed, and ten genes are significantly hypermethylated in H. pylori-infected children compared to healthy controls in at least 1 study. Only four of these biomarkers (pepsinogen I, pepsinogen II, gastrin, and SLC5A8) have been studied in asymptomatically infected children. Importantly, 13 of these biomarkers (β-catenin, C-MYC, GATA-4, DAPK1, CXCL13, DC-SIGN, TIMP3, EGFR, GRIN2B, PIM2, SLC5A8, CDH1, and VCAM-1.) are consistently deregulated in infected children and in adults with gastric cancer. Future studies should be designed to determine the clinical significance of these changes in infection-associated biomarkers in children and their persistence over time. The effect of eradication therapy over these biomarkers in children if proven significant, could lead to modifications in treatment guidelines for younger populations, and eventually promote the development of preventive strategies, such as vaccination, in the near future.

Gastric Tumor Microenvironment

A compelling body of evidence has demonstrated that gastric cancer has a very particular tumor microenvironment, a signature very suitable to promote tumor progression and metastasis. Recent investigations have provided new insights into the multiple molecular mechanisms, defined by genetic and epigenetic mechanisms, supporting a very active cross talk between the components of the tumor microenvironment and thus defining the fate of tumor progression. In this review, we intend to highlight the role of very active contributors at gastric cancer TME, particularly cancer-associated fibroblasts, bone marrow-derived cells, tumor-associated macrophages, and tumor-infiltrating neutrophils, all of them surrounded by an overtime changing extracellular matrix. In addition, the very active cross talk between the components of the tumor microenvironment, defined by genetic and epigenetic mechanisms, thus defining the fate of tumor progression, is also reviewed.

Circular RNAs Regulate Cancer Onset and Progression via Wnt/β-Catenin Signaling Pathway

Cancer remains to be a major challenge for public health providers, and is the second leading cause of death worldwide. Therefore, it is imperative to explore the mechanisms underlying cancer initiation and development, and design novel diagnostics and therapeutics. Circular RNAs (circRNAs), which exhibit a covalently closed loop structure, are involved in a variety of diseases, including cancer. The aberrant expression of circRNAs contributes to the initiation and development of various cancers by disrupting the interplay of specific signaling pathways, including the Wnt/β-catenin pathway, which controls a plethora of cellular processes that drive cancer development. The interactions between circRNAs (specifically expressed in different cancer tissues) and Wnt/β-catenin signaling pathway presents potential diagnostic biomarkers and novel therapeutic targets. In this review, we have summarized research discoveries on the functions of Wnt/β-catenin pathway-related circRNAs in the modulation of oncogenesis and progression of different types of cancer. We anticipate that our findings will contribute to the improvement or development of circRNAs-based strategies for cancer treatment.

Gastric microflora and gastric disease

Gastric environment has long been considered sterile, but the discovery of Helicobacter pylori (H. pylori) changed such concept in 1982. Over the past few decades, modern techniques have provided insight into microbial communities in the stomach and the interactions between communities, ranging from methods that rely on bacterial culture to the application of macrogenomics and high-throughput sequencing techniques. H. pylori is an important risk factor for gastric disease, but there may be other bacteria involved in the occurrence of gastric disease. This review summarizes the current progress in the understanding of the relationship between gastric microflora and gastric disease.

Dendrobium officinale Polysaccharides Inhibit 1-Methyl-2-Nitro-1-Nitrosoguanidine Induced Precancerous Lesions of Gastric Cancer in Rats through Regulating Wnt/β-Catenin Pathway and Altering Serum Endogenous Metabolites

Dendrobium officinale is a herb in traditional Chinese medicine where D. officinale polysaccharides (DOP) are the main active ingredient. This study aimed at evaluating DOP efficiency at inhibiting 1-Methyl-2-nitro-1-nitrosoguanidine (MNNG) induced precancerous lesions of gastric cancer (PLGC) in rats through the Wnt/b-catenin pathway and analyzing the variations of serum endogenous metabolites. PLGC was established in male Sprague-Dawley (SD) rats by administering 150 μg/mL MNNG in drinking water for 7 months and giving 0.1 mL of 10% NaCl once weekly during the initial 20 weeks. Treatment with DOP inhibited the progress of PLGC through decreasing the expression of β-catenin by immunohistochemical analysis. The futher study indicated DOP downregulated gene expression of Wnt2β, Gsk3β, PCNA, CyclinD1, and β-catenin, as well as protein expression of Wnt2β, PCNA, and β-catenin. On the other hand, there were nine endogenous metabolites identified after the DOP treatment. Among these, the most significant one is betaine because of its strong antioxidant activity, leading to an anti-tumor effect. DOP can inhibit MNNG-induced PLGC models via regulating Wnt/β-catenin pathway and by changing endogenous metabolites.

KDM4B promotes gastric cancer metastasis by regulating miR-125b-mediated activation of Wnt signaling

Emerging evidence has demonstrated that the aberrant expression of histone-modifying enzymes such as histone demethylases contributes to gastric carcinogenesis and progression. The role of KDM4B in cancer progression has been gradually revealed. However, the underlying mechanisms regulating gastric cancer metastasis of KDM4B remain unclear. In the present study we determined KDM4B expression in gastric cancer and its biologic function in vitro and in vivo. We found that KDM4B expression was significantly increased in most gastric cancer tissues compared with the adjacent normal tissues. Upregulated expression of KDM4B in human gastric cancer was correlated with poor prognosis. In vitro, KDM4B overexpression in AGS cells promoted cell invasion, whereas knockdown of KDM4B inhibited cell invasion. Furthermore, KDM4B overexpression also promoted tumor metastasis in vivo. Mechanistically, KDM4B upregulated miR-125b expression and activated Wnt signaling pathway. More important, miR-125b partially mediated KDM4B-induced activation of Wnt signaling. Finally, we demonstrated that KDM4B promoted gastric cancer cell invasion in vitro and cancer metastasis in vivo, at least in part, by upregulating miR-125b expression. These data provided novel insights on the role of KDM4B-driven gastric cancer metastasis and indicated that KDM4B may be served as a potential target for gastric cancer.