The role of microbiota in the development and treatment of gastric cancer

Streptococcus anginosus promotes gastric cancer progression via GSDME-mediated pyroptosis pathway: Molecular mechanisms of action of GSDME, cleaved caspase-3, and NLRP3 proteins

Streptococcus vasculosus is a common oral and intestinal symbiotic bacteria, but it can transform into a pathogen under certain conditions, affecting the host's immune response. Studies have shown that Streptococcus vasculosus may promote tumor growth and metastasis by activating host inflammatory responses. This study simulated the environment of Streptococcus vascularis infection through in vitro cell culture experiment, and observed the influence of streptococcus vascularis at different time points and different concentrations on cancer cells. The expression and activity of GSDME, cleaved caspase-3 and NLRP3 proteins were detected by Western blot, immunofluorescence and flow cytometry. By constructing gene knockout and overexpression cell models, the role of these protein molecules in promoting cancer progression of Streptococcus vascularis was further verified. It was found that GSDME activation is a key step in Pyroptosis occurrence, and cleaved caspase-3 plays an important role in GSDME cleavage activation. The activation of NLRP3 inflammatome is closely related to the inflammatory response induced by Streptococcus vasculosus, and thus affects the tumor microenvironment.

Role of human microbiota in facilitating the metastatic journey of cancer cells

Cancer continues to be the leading cause of mortality worldwide, with metastasis being the primary contributor to cancer-related deaths. Despite significant advancements in cancer therapies, metastasis remains a major challenge in effective cancer management. Metastasis, the process by which cancer cells spread from the primary tumor to distant organs, is a complex phenomenon influenced by multiple factors, including the human microbiota. The human body encompasses various microorganisms, comprising bacteria, viruses, fungi, and protozoa, collectively known as microbiota. In fact, the microbiota is more abundant than human cells, and its disruption, leading to an imbalance in host-microbiota interactions (dysbiosis), has been linked to various diseases, including cancer. Among all microbiota, bacteria are one of the key contributors to cancer progression. Bacteria and bacteria-derived components such as secondary metabolites, QSPs, and toxins play a pivotal role in the metastatic progression of cancers. This review explores the intricate relationship between the human microbiota and cancer progression, focusing on different bacterial species which have been implicated in tumorigenesis, immune evasion, and metastasis. The present review explores the role of the human microbiome, specifically of bacteria in promoting metastasis in different types of cancers, demonstrating its ability to impact both the spread of tumors and their underlying mechanisms. This review also highlights the therapeutic potential and challenges of microbiome-based interventions in combating metastatic cancers. By addressing these challenges and by integrating microbiome-targeted strategies into clinical cancer treatment could represent a transformative approach in the fight against metastasis.

Quantification of Naturally Occurring Prebiotics in Selected Foods

Background: Prebiotics are non-digestible dietary compounds, defined as substrates that are utilised by host microorganisms conferring a health benefit. Although fructo-oligosaccharides (FOSs) and galacto-oligosaccharides (GOSs) are among the most studied prebiotics and support intestinal normobiosis, comprehensive data on their content in foods remain limited. Objectives: The objective was to quantify the content of FOSs (kestose, nystose, and 1 F-β-fructofuranosylnystose) and GOSs (raffinose and stachyose) in 35 foods, including fruit and nuts, legumes, and cereals. We also estimated the intakes of prebiotics in an Italian population. Methods: We analysed the prebiotic content in foods using high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD). We estimated the prebiotic intake of 100 healthy controls from a case-control study on colorectal cancer conducted in Italy between 2017 and 2019. We used dietary information collected through a food frequency questionnaire and the prebiotic data quantified in this and a previous study. Results: FOSs were mostly detected in cereal products, with wheat bran and whole-meal rye flour containing the highest amount (around 0.7 g/100 g each). GOSs were most abundant in legumes, especially in dried soy products (around 4.0 g/100 g each). Mean daily intake was 0.236 g for total FOSs and 0.371 g for total GOSs. Wheat bran, raspberries, chestnuts, walnuts, raisins, soy milk, and soy yoghurt overall accounted for 3.9% of kestose, 1.2% of nystose, 0% of 1F-β-fructofuranosylnystose, 15.5% of raffinose, and 8.3% of stachyose total intakes. Conclusions: The present study enables the development of a comprehensive database on prebiotic content in foods through a consistent analytical method. This makes prebiotic intake assessments more accurate than previously available data and facilitates future epidemiological studies investigating their potential effects on health.

Overcoming immunotherapy resistance in gastric cancer: insights into mechanisms and emerging strategies

Gastric cancer (GC) remains a leading cause of cancer-related mortality worldwide, with limited treatment options in advanced stages. Immunotherapy, particularly immune checkpoint inhibitors (ICIs) targeting PD1/PD-L1, has emerged as a promising therapeutic approach. However, a significant proportion of patients exhibit primary or acquired resistance, limiting the overall efficacy of immunotherapy. This review provides a comprehensive analysis of the mechanisms underlying immunotherapy resistance in GC, including the role of the tumor immune microenvironment, dynamic PD-L1 expression, compensatory activation of other immune checkpoints, and tumor genomic instability. Furthermore, the review explores GC-specific factors such as molecular subtypes, unique immune evasion mechanisms, and the impact of Helicobacter pylori infection. We also discuss emerging strategies to overcome resistance, including combination therapies, novel immunotherapeutic approaches, and personalized treatment strategies based on tumor genomics and the immune microenvironment. By highlighting these key areas, this review aims to inform future research directions and clinical practice, ultimately improving outcomes for GC patients undergoing immunotherapy.

Advances in 16S rRNA-Based Microbial Biomarkers for Gastric Cancer Diagnosis and Prognosis

Gastric cancer (GC) is a malignant tumour with high morbidity and mortality worldwide, and there is an urgent need for early diagnosis and precision treatment. In recent years, the role of microbiota in the occurrence and development of GC has drawn extensive attention. Particularly, the in-depth study of GC-related microbiota by 16S rRNA sequencing technology has offered valuable tools and new perspectives for exploring the microbial characteristics of GC patients. This review systematically summarises the microbial diversity and composition of GC and non-GC samples based on 16S rRNA data, outlines the progress in identifying GC-related microbial biomarkers, explores the potential mechanisms by which diagnostic microbial biomarkers influence the development of GC, and reflects on the limitations of present studies. By integrating the current evidence, this review intends to offer a new theoretical foundation and further direction for the clinical translation of microbiota research in the diagnosis and treatment of GC.

Exploring the mediating role of blood metabolites in the relationship between gut microbiota and gastric cancer risk: a Mendelian randomization study

Background

Prior studies have established correlations between gut microbiota (GM) dysbiosis, circulating metabolite alterations, and gastric cancer (GC) risk. However, the causal nature of these associations remains uncertain.

Methods

We utilized summary data from genome-wide association studies (GWAS) on GM (European, n=8,956), blood metabolites (European, n=120,241; East Asian, n=4,435), and GC (European, n=476,116; East Asian, n=167,122) to perform a bidirectional Mendelian randomization (MR) analysis, investigating the causal effects of GM and metabolites on GC risk. Additionally, we conducted mediation analysis (two-step MR) to identify potential metabolite mediators in the GM-GC relationship.

Results

We identified twelve negative and seven positive associations between specific GM taxa and GC risk. For blood metabolites, seven traits were found to be significantly associated with reduced GC risk in the European population, with these findings subsequently validated in the East Asian cohort. Three GM taxa showed potential causal associations with five metabolic traits: the Bacteroidia class and Bacteroidales order were positively correlated with five metabolites (all P < 0.013), while Bacteroides OTU97_27 exhibited a negative correlation with one metabolite (P = 0.007). Two-step MR analysis indicated that total lipids in intermediate-density lipoprotein (IDL), IDL particle concentration, phospholipids in medium low-density lipoprotein (LDL), phospholipids in small LDL, and free cholesterol in small LDL indirectly influenced the association between Bacteroidia class/Bacteroidales order and GC, with mediation proportions of 1.71% (P = 0.048), 1.69% (P = 0.048), 2.05% (P = 0.045), 1.85% (P = 0.048), and 1.99% (P = 0.045), respectively.

Conclusion

The present study provides suggestive evidence of a causal relationship between specific GM, blood metabolites, and GC risk, potentially offering new insights into GC etiology.

Living biobank: Standardization of organoid construction and challenges

ABSTRACT

In multiple areas such as science, technology, and economic activities, it is necessary to unify the management of repetitive tasks or concepts by standardization to obtain the best order and high efficiency. Organoids, as living tissue models, have rapidly developed in the past decade. Organoids can be used repetitively for in vitro culture, cryopreservation, and recovery for further utilization. Because organoids can recapitulate the parental tissues' morphological phenotypes, cell functions, biological behaviors, and genomic profiles, they are known as renewable "living biobanks". Organoids cover two mainstream fields: Adult stem cell-derived organoids (also known as patient-derived organoids) and induced pluripotent stem cell-derived and/or embryonic stem cell-derived organoids. Given the increasing importance of organoids in the development of new drugs, standardized operation, and management in all steps of organoid construction is an important guarantee to ensure the high quality of products. In this review, we systematically introduce the standardization of organoid construction operation procedures, the standardization of laboratory construction, and available standardization documents related to organoid culture that have been published so far. We also proposed the challenges and prospects in this field.

Intratumoral and fecal microbiota reveals microbial markers associated with gastric carcinogenesis

Background

The relationship between dysbiosis of the gastrointestinal microbiota and gastric cancer (GC) has been extensively studied. However, microbiota alterations in GC patients vary widely across studies, and reproducible diagnostic biomarkers for early GC are still lacking in multiple populations. Thus, this study aimed to characterize the gastrointestinal microbial communities involved in gastric carcinogenesis through a meta-analysis of multiple published and open datasets.

Methods

We analyzed 16S rRNA sequencing data from 1,642 gastric biopsy samples and 394 stool samples across 11 independent studies. VSEARCH, QIIME and R packages such as vegan, phyloseq, cooccur, and random forest were used for data processing and analysis. PICRUSt software was employed to predict functions.

Results

The α-diversity results indicated significant differences in the intratumoral microbiota of cancer patients compared to non-cancer patients, while no significant differences were observed in the fecal microbiota. Network analysis showed that the positive correlation with GC-enriched bacteria increased, and the positive correlation with GC-depleted bacteria decreased compared to healthy individuals. Functional analyses indicated that pathways related to carbohydrate metabolism were significantly enriched in GC, while biosynthesis of unsaturated fatty acids was diminished. Additionally, we investigated non-Helicobacter pylori (HP) commensals, which are crucial in both HP-negative and HP-positive GC. Random forest models, constructed using specific taxa associated with GC identified from the LEfSe analysis, revealed that the combination of Lactobacillus and Streptococcus included alone could effectively discriminate between GC patients and healthy individuals in fecal samples (area under the curve (AUC) = 0.7949). This finding was also validated in an independent cohort (AUC = 0.7712).

Conclusions

This study examined the intratumoral and fecal microbiota of GC patients from a dual microecological perspective and identified Lactobacillus, Streptococcus, Roseburia, Faecalibacterium and Phascolarctobacterium as intratumoral and intestinal-specific co-differential bacteria. Furthermore, it confirmed the validity of the combination of Lactobacillus and Streptococcus as GC-specific microbial markers across multiple populations, which may aid in the early non-invasive diagnosis of GC.

Streptococcus anginosus in the development and treatment of precancerous lesions of gastric cancer

The microbiota is strongly association with cancer. Studies have shown significant differences in the gastric microbiota between patients with gastric cancer (GC) patients and noncancer patients, suggesting that the microbiota may play a role in the development of GC. Although Helicobacter pylori (H. pylori) infection is widely recognized as a primary risk factor for GC, recent studies based on microbiota sequencing technology have revealed that non-H. pylori microbes also have a significant impact on GC. A recent study discovered that Streptococcus anginosus (S. anginosus) is more prevalent in the gastric mucosa of patients with GC than in that of those without GC. S. anginosus infection can spontaneously induce chronic gastritis, mural cell atrophy, mucoid chemotaxis, and heterotrophic hyperplasia, which promote the development of precancerous lesions of GC (PLGC). S. anginosus also disrupts the gastric barrier function, promotes the proliferation of GC cells, and inhibits apoptosis. However, S. anginosus is underrepresented in the literature. Recent reports suggest that it may cause precancerous lesions, indicating its emerging pathogenicity. Modern novel molecular diagnostic techniques, such as polymerase chain reaction, genetic testing, and Ultrasensitive Chromosomal Aneuploidy Detection, can be used to gastric precancerous lesions via microbial markers. Therefore, we present a concise summary of the relationship between S. anginosus and PLGC. Our aim was to further investigate new methods of preventing and treating PLGC by exploring the pathogenicity of S. anginosus on PLGC.

Current Knowledge about Gastric Microbiota with Special Emphasis on Helicobacter pylori-Related Gastric Conditions

The gastric milieu, because of its very low acidic pH, is very harsh for bacterial growth. The discovery of Helicobacter pylori (H.p.) has opened a new avenue for studies on the gastric microbiota, thus indicating that the stomach is not a sterile environment. Nowadays, new technologies of bacterial identification have demonstrated the existence of other microorganisms in the gastric habitat, which play an important role in health and disease. This bacterium possesses an arsenal of compounds which enable its survival but, at the same time, damage the gastric mucosa. Toxins, such as cytotoxin-associated gene A, vacuolar cytotoxin A, lipopolysaccharides, and adhesins, determine an inflammatory status of the gastric mucosa which may become chronic, ultimately leading to a gastric carcinoma. In the initial stage, H.p. persistence alters the gastric microbiota with a condition of dysbiosis, predisposing to inflammation. Probiotics and prebiotics exhibit beneficial effects on H.p. infection, and, among them, anti-inflammatory, antioxidant, and antibacterial activities are the major ones. Moreover, the association of probiotics with prebiotics (synbiotics) to conventional anti-H.p. therapy contributes to a more efficacious eradication of the bacterium. Also, polyphenols, largely present in the vegetal kingdom, have been demonstrated to alleviate H.p.-dependent pathologies, even including the inhibition of tumorigenesis. The gastric microbiota composition in health and disease is described. Then, cellular and molecular mechanisms of H.p.-mediated damage are clarified. Finally, the use of probiotics, prebiotics, and polyphenols in experimental models and in patients infected with H.p. is discussed.

Helicobacter pylori causes gastric dysbacteriosis in chronic gastritis patients

Gastric mucosal samples were procured and underwent the sequencing of 16S ribosomal RNA (16S rRNA) via Illumina high-throughput sequencing technology to explore the impact of Helicobacter pylori (H. pylori) infection on the composition of gastric flora in chronic gastritis (CG) patients. In the results, the operational taxonomic unit (OTU) analysis revealed an overlap of 5706 OTUs shared between the two groups. The top 5 abundance ranking (TOP5) phyla comprised Bacteroidetes, Proteobacteria, Firmicutes, Actinobacteria, and Epsilonbacteraeota, while the TOP5 genus was Lachnospiraceae_NK4A136_group, Helicobacter, Bacteroides, Klebsiella, and Pseudomonas. In the metabolic pathways at the Kyoto Encyclopedia of Genes and Genomes (KEGG)_L3 level, conspicuous variations across seven functions were observed between the H. pylori-positive (HP_Pos) and H. pylori-negative (HP_Neg) groups. Subsequently, functional gene enrichment in KEGG pathways was further validated through animal experimentation. In contrast to the mice in the HP_Neg group, those infected with H. pylori manifested an infiltration of inflammatory cells, an augmentation in gastric acid secretion, and conspicuously elevated scores regarding gastric activity, along with heightened levels of malondialdehyde. In conclusion, CG patients infected with H. pylori displayed a disorder in gastric flora, furnishing a theoretical basis for the prophylaxis of H. pylori infection and its associated pathogenic ramifications.

Exploring the Relationship between Ovarian Cancer and Genital Microbiota: A Systematic Review and Meta-Analysis

Ovarian cancer (OC) remains a significant health challenge globally, with high mortality rates despite advancements in treatment. Emerging research suggests a potential link between OC development and genital dysbiosis, implicating alterations in the microbiome composition as a contributing factor. To investigate this correlation, a meta-analysis was conducted following PRISMA and MOOSE guidelines, involving eight studies encompassing 3504 patients. Studies investigating the role of upper and inferior genital tract dysbiosis were included, with particular reference to HPV infection and/or history of pelvic inflammatory disease. The analysis revealed no significant difference in genital dysbiosis prevalence between OC patients and healthy controls. Although previous literature suggests associations between dysbiosis and gynecologic cancers, such as cervical and endometrial cancers, the findings regarding OC are inconclusive. Methodological variations and environmental factors may contribute to these discrepancies, underscoring the need for standardized methodologies and larger-scale studies. Despite the limitations, understanding the microbiome's role in OC development holds promise for informing preventive and therapeutic strategies. A holistic approach to patient care, incorporating microbiome monitoring and personalized interventions, may offer insights into mitigating OC risk and improving treatment outcomes. Further research with robust methodologies is warranted to elucidate the complex interplay between dysbiosis and OC, potentially paving the way for novel preventive and therapeutic approaches.

Immunotherapy of gastric cancer: Present status and future perspectives

In this editorial, we comment on the article entitled "Advances and key focus areas in gastric cancer immunotherapy: A comprehensive scientometric and clinical trial review (1999-2023)," which was published in the recent issue of the World Journal of Gastroenterology. We focused on the results of the authors' bibliometric analysis concerning gastric cancer immunotherapy, which they analyzed in depth by compiling the relevant publications of the last 20 years. Before that, we briefly describe the most recent data concerning the epidemiological parameters of gastric cancer (GC) in different countries, attempting to give an interpretation based on the etiological factors involved in the etiopathogenesis of the neoplasm. We then briefly discuss the conservative treatment (chemotherapy) of the various forms of this malignant neoplasm. We describe the treatment of resectable tumors, locally advanced neoplasms, and unresectable (advanced) cases. Special attention is given to modern therapeutic approaches with emphasis on immunotherapy, which seems to be the future of GC treatment, especially in combination with chemotherapy. There is also a thorough analysis of the results of the study under review in terms of the number of scientific publications, the countries in which the studies were conducted, the authors, and the scientific centers of origin, as well as the clinical studies in progress. Finally, an attempt is made to draw some con-clusions and to point out possible future directions.