Impact factors that modulate gastric cancer risk in Helicobacter pylori-infected rodent models

Bacterial Involvement in Progression and Metastasis of Adenocarcinoma of the Stomach

Simple Summary

Infectious bacteria influence primary gastric carcinogenesis, organotropism, and metastatic progression by altering the microenvironment at the primary and secondary tumors. Key species include Helicobacter pylori (H. pylori) and Mycoplasma hyorhinis (M. hyorhinis). Inflammation caused by H. pylori virulence factors, such as CagA, VacA, and oipA, disrupt epithelial integrity, which allows the primary tumor to progress through the metastatic process. Evidence supports the activation of aquaporin-5 by CagA-positive H. pylori infection, promoting epithelial–mesenchymal transition via the extracellular signal-regulated kinase/mitogen-activated protein kinase (MEK/ERK) pathway, thus laying the foundation for metastatic disease. M. hyorhinis has also been implicated in gastric neoplasia via β-catenin stabilization and subsequent activation of the WNT-signaling pathway, promoting gastric cancer cell motility and inciting cancer progression.

Abstract

Gastric cancer metastasis is a process in which the tumor microenvironment may carry significant influence. Helicobacter pylori (H. pylori) infection is well-established as a contributor to gastric carcinoma. However, the role that these bacteria and others may play in gastric carcinoma metastasis is a current focus of study. A review of the literature was conducted to elucidate the process by which gastric adenocarcinoma metastasizes, including its ability to utilize both the lymphatic system and the venous system to disseminate. Studies that investigate the tumor microenvironment at both the primary and secondary sites were assessed in detail. H. pylori and Mycoplasma hyorhinis (M. hyorhinis) were found to be important drivers of the pathogenesis of gastric adenocarcinoma by modifying various steps in cell metastasis, including epithelial–mesenchymal transition, cell migration, and cell invasion. H. pylori is also a known driver of MALT lymphoma, which is often reversible simply with the eradication of infection. M. hyorhinis has been implicated in gastric neoplasia via β-catenin stabilization and subsequent activation of the WNT-signaling pathway, promoting gastric cancer cell motility and inciting cancer progression. Fusobacterium nucleatum (F. nucleatum) and its association with worse prognosis in diffuse-type gastric adenocarcinoma are also reviewed. Recognition of the roles that bacteria play within the metastatic cascade is vital in gastrointestinal adenocarcinoma treatment and potential reoccurrence. Further investigation is needed to establish potential treatment for metastatic gastric carcinoma by targeting the tumor microenvironment.

Probing Transferrin Receptor Overexpression in Gastric Cancer Mice Models

Exposure to carcinogenic chemicals, Helicobacter pylori infection, and high dietary salt are the risk factors associated with gastric cancer. Mice models of gastric cancer are key to understanding the cancer mechanism, to discerning the role played by different factors, and to determining therapeutic effects of different treatments. The goal has been to find targets which are only expressed with cancer so that they can be targeted specifically without harming normal cells. One such target could be the transferrin receptor, a glycoprotein receptor that is expressed many-folds on rapidly growing cells due to the greater demand of iron. In this study, gastric cancer was developed in mice (BALB/c) with human cancer-associated risk factors by feeding them with tumor-inducing concentration of methyl nitrosourea, dietary salt, and H. pylori along with normal feed and water. Three strategies were adopted to induce gastric cancer; (1) use of N-methyl-N-nitrosourea (MNU) with high dietary salt (NaCl), (2) infection with H. pylori (isolated from human gastric tissue), and (3) use of MNU along with high concentration of NaCl after H. pylori infection. Mice were dissected after induction, and histological study of gastric tissue was done with Hematoxylin and Eosin staining. A diagnostic probe comprising transferrin conjugated with cadmium sulfide quantum dots was prepared and characterized. It was used to study the transferrin receptor overexpression in gastric tissue of cancer-induced mice relative to the normal mice. Mice of group 3 showed the highest rate of the cancer incidence ratio (96%) along with a high expression of transferrin receptors among the three groups. Histochemical studies showed that different types of gastric cancer depend upon the cancer-induction conditions. The mouse model of group 3 has the potential to be used in the future to study the therapeutic effects of cancer medicines, and overexpression of transferrin receptors could be identified through the designed probe to be used as diagnostics.

Activation of Aquaporin 5 by carcinogenic Helicobacter pylori infection promotes epithelial-mesenchymal transition via the MEK/ERK pathway

BACKGROUND

Helicobacter pylori (H. pylori) is a major risk factor for gastric cancer. The water channel protein Aquaporin 5 (AQP5) is involved in the tumorigenesis and progression of various cancers. In this study, we aimed to explore the role of AQP5 in H. pylori-induced gastric carcinogenesis.

MATERIALS AND METHODS

We collected 160 samples which inculded CNAG, IM, Dys and gastric cancer from patients who underwent endoscopy and detected the expression of AQP5. In vivo and vitro H. pylori infection models, we explored the relationship between AQP5 and H. pylori. Plasmid, siRNA and inhibitors were used to investigated the relationship between AQP5 and EMT and the role of AQP5 in H. pylori-induced gastric carcinogenesis.

RESULT

AQP5 expression was gradually increased in human gastric tissues with the progression of chronic nonatrophic gastritis to gastric cancer and associated with the H. pylori infection status. In vivo and in vitro studies showed that H. pylori infection induced AQP5 expression in gastric epithelial cells in a CagA-dependent manner. Knockdown of AQP5 reversed H. pylori-induced cell proliferation and invasion, and -suppressed cell apoptosis. Additionally, knockdown of AQP5 suppressed H. pylori-induced Epithelial-mesenchymal transition (EMT) phenotypes by regulating transcriptional factors, mesenchymal markers, and epithelial markers.

CONCLUSIONS

We explored the underlying mechanism and our results indicated that knockdown of AQP5 significantly suppressed H. pylori infection-induced phosphorylation of ERK1/2, MEK and the expression levels of downstream genes. Treatment with an ERK inhibitor suppressed the EMT induced by H. pylori infection. Taken together, this study suggest that pathogenic H. pylori infection promotes AQP5 expression to induce the EMT via the MEK/ERK signaling pathway.

Genotyping Helicobacter pylori antibiotic resistance - and virulence-associated genes in patients with gastric cancer in Wenzhou, China

BACKGROUND AND STUDY AIMS

Helicobacter pylori infection affects approximately 50% of the global population and has become a serious health concern related to gastric cancer, gastritis, and peptic ulcers. This organism acquires drug resistance through gene mutations, and its increasing resistance to antibiotics has severely influenced the effectiveness of eradication efforts. Therefore, we designed this study to determine the prevalence of H. pylori virulence- (cagA and vacA) and antibiotic resistance - associated genotypes in patients with gastric cancer infected with H. pylori in Whenzhou, China.

PATIENTS AND METHODS

We used polymerase chain reaction (PCR) to confirm H. pylori in cancerous and paracancerous tissue specimens from 225 patients. Then we tested the prevalence of virulence- and antibiotic resistance - associated genotypes in H. pylori using a PCR-based DNA-sequencing assay.

RESULTS

We observed H. pylori DNA in 222 of the 225 patients and found the most prevalent virulence-associated genotypes in cagA⁺ (97.75%) and vacAs1m1 (93.25%). Metronidazole resistance - associated gene mutation was G616A in rdxA; levofloxacin resistance - associated gene mutations were N87K, N87I, and D91G in gyrA; clarithromycin resistance - associated gene mutations were A2143G and A2142G in 23SrRNA; and amoxicillin resistance - associated gene mutation was T556S in pbp1. The most prevalent mutation related to antibiotic resistance was present in rdxA (97.30%), followed by gyrA (41.44%) and 23SrRNA (16.67%); the least prevalent was in pbp1 (2.25%). We observed single-gene mutations in 102 patients (45.95%) and found mutations in multiple genes (≥2 genes) in 116 patients (52.25%).

CONCLUSION

Patients with gastric cancer in Wenzhou, China, have high incidence infection caused by H. pylori with high-toxicity virulence genotypes. The frequency of gene mutations associated with metronidazole, levofloxacin, and clarithromycin resistances was high and that associated with amoxicillin resistance was relatively low. The mutation patterns were diverse, and the rates of multiple gene mutations were high.

Inhibition of autophagy aggravates DNA damage response and gastric tumorigenesis via Rad51 ubiquitination in response to H. pylori infection

Helicobacter pylori (H. pylori) infection is the strongest known risk factor for the development of gastric cancer. DNA damage response (DDR) and autophagy play key roles in tumorigenic transformation. However, it remains unclear how H. pylori modulate DDR and autophagy in gastric carcinogenesis. Here we report that H. pylori infection promotes DNA damage via suppression of Rad51 expression through inhibition of autophagy and accumulation of p62 in gastric carcinogenesis. We find that H. pylori activated DNA damage pathway in concert with downregulation of repair protein Rad51 in gastric cells, C57BL/6 mice and Mongolian gerbils. In addition, autophagy was increased early and then decreased gradually during the duration of H. pylori infection in vitro in a CagA-dependent manner. Moreover, loss of autophagy led to promotion of DNA damage in H. pylori-infected cells. Furthermore, knockdown of autophagic substrate p62 upregulated Rad51 expression, and p62 promoted Rad51 ubiquitination via the direct interaction of its UBA domain. Finally, H. pylori infection was associated with elevated levels of p62 in gastric intestinal metaplasia and decreased levels of Rad51 in dysplasia compared to their H. pylori- counterparts. Our findings provide a novel mechanism into the linkage of H. pylori infection, autophagy, DNA damage and gastric tumorigenesis.

The NF-κB Signaling Pathway, the Microbiota, and Gastrointestinal Tumorigenesis: Recent Advances

Gastrointestinal (GI) cancers, especially gastric cancer and colorectal cancer (CRC), represent a major global health burden. A large population of microorganisms residing in the GI tract regulate physiological processes, such as the immune response, metabolic balance, and homeostasis. Accumulating evidence has revealed the alteration of microbial communities in GI tumorigenesis. Experimental studies in cell lines and animal models showed the functional roles and molecular mechanisms of several bacteria in GI cancers, including Helicobacter pylori in gastric cancer as well as Fusobacterium nucleatum, Escherichia coli, Peptostreptococcus anaerobius, and Bacteroides fragilis in CRC. The transcriptional factor NF-κB plays a crucial role in the host response to microbial infection through orchestrating innate and adaptive immune functions. Moreover, NF-κB activity is linked to GI cancer initiation and development through its induction of chronic inflammation, cellular transformation and proliferation. Here, we provide an overview and discussion of modulation of the NF-κB signaling pathway by microbiota, especially infectious bacteria, in GI tumorigenesis, with a major focus on gastric cancer and CRC.