Distinct oral-associated gastric microbiota and Helicobacter pylori communities for spatial microbial heterogeneity in gastric cancer

Microbiota and gastric cancer: from molecular mechanisms to therapeutic strategies

Gastric cancer, a prevalent malignancy globally, is influenced by various factors. The imbalance in the gut microbiome and the existence of particular intratumoural microbiota could have a strong connection with the onset and progression of gastric cancer. High-throughput sequencing technology and bioinformatics analysis have revealed a close correlation between abnormal abundance of specific microbial communities and the risk of gastric cancer. These microbial communities contribute to gastric cancer progression through mechanisms including increasing cellular genomic damage, inhibiting DNA repair, activating abnormal signaling pathways, exacerbating tumor hypoxia, and shaping a tumor immune-suppressive microenvironment. This significantly impacts the efficacy of gastric cancer treatments, including chemotherapy and immunotherapy. Probiotic, prebiotic, antibiotic, carrier-based, dietary interventions, fecal microbiota transplantation, and traditional Chinese medicine show potential applications in gastric cancer treatment. However, the molecular mechanisms regarding dysbiosis of microbiota, including gut microbiota, and intra-tumoral microbiota during the progression of gastric cancer, as well as the therapeutic efficacy of microbiota-related applications, still require extensive exploration through experiments.

Analyses of single-cell RNA sequencing uncover the role of intratumoral Helicobacter pylori in shaping tumor progression and immunity in gastric cancer

The intratumoral microbiota is closely associated with tumor initiation and progression in multiple solid tumors, including gastric cancer (GC). Single-cell analysis of host-microbiome interactions (SAHMI) is a pipeline used to systematically recover and denoise microbial signals in human clinical tissues and examine tumor-microbiome interactions at the single-cell transcriptome level. In a large GC cohort, we used SAHMI to detect 12 bacteria, among which Helicobacter pylori (H. pylori) was widely present in multiple tumor and normal samples. Meanwhile, we verified the presence of H. pylori in GC tissues via fluorescence in situ hybridization and immunohistochemistry. We performed single-cell RNA sequencing to analyze 11 cell populations, including B cells, T cells, and epithelial cells, and these cell types contained large numbers of H. pylori. We detected obvious enrichment of H. pylori in cancer cells and identified 13 upregulated differentially expressed genes exhibiting significantly negative correlations with patient survival in the H. pylori-positive tumor group compared with the findings in the other groups, indicating that these genes could represent prognostic biomarkers or therapeutic targets for H. pylori-infected patients with GC. Moreover, H. pylori-enriched immune cells, including T cells, B cells, and macrophages, were associated with cell-type-specific gene expression and pathway activities, including cell fate and immune signaling. In summary, tumor-microbiome interactions might reflect or influence tumorigenesis in GC, which has implications for clinical practice.

The Role of Microbiota in Upper Gastrointestinal Cancers

The gut microbiota significantly impacts the development and progression of upper gastrointestinal (GI) cancers, including esophageal and gastric cancers. Microbial dysbiosis contributes to carcinogenesis through mechanisms such as inflammation, immune modulation, and direct DNA damage. Techniques for sampling oral, esophageal, and gastric microbiota vary, with standardization being essential for reliable results. Barrett's esophagus (BE) and esophageal adenocarcinoma (EAC) are associated with an enrichment of Gram-negative bacteria, promoting inflammation and cancer progression. Esophageal squamous cell carcinoma (ESCC) also shows distinct microbial patterns, with reduced diversity and increased harmful bacteria like Porphyromonas gingivalis and Fusobacterium nucleatum. In gastric cancer (GC), Helicobacter pylori (HP) and non-HP gastric microbiota play significant roles, with diverse microbial communities contributing to cancer development through nitrate reduction, immune modulation, and inflammation. Emerging evidence highlights the role of non-HP bacteria in promoting carcinogenesis, with specific taxa like Fusobacterium nucleatum and Lactobacillus influencing tumor growth and immune evasion. Further research is needed to elucidate the complex interactions between gut microbiota and upper GI cancers, paving the way for novel diagnostic and therapeutic approaches. Understanding these microbial dynamics offers potential for microbiota-based interventions, improving the early detection, prognosis, and treatment of upper GI cancers. This comprehensive review summarizes the available evidence on the role of microbiota in upper GI oncology and the need for continued exploration in this field.

Oral microbes and gastrointestinal cancers: new strategies and insights

Gastrointestinal (GI) cancers are among the most prevalent cancers globally and represent a leading cause of cancer-related mortality. A distinctive characteristic of these cancers is their association with the microbes. Gut microbiota dysbiosis is widely recognized as a contributing factor in cancer development. Recent advancements in molecular techniques have increasingly underscored the role of oral microbes in GI cancers, especially colorectal cancer. Oral microbes, transported to the gut via swallowed saliva, have been shown to influence GI health. Both in vivo and in vitro investigations demonstrated the impacts of oral microbes in GI cancers. This review explores the changes in oral microbial diversity and relative abundance in esophageal, gastric and colorectal cancers as well as the underlying mechanisms. These mechanisms include immunomodulation, epigenetics, apoptosis, and others. Among these, immunomodulation stands out due to its close connection with cancer treatment. Finally, we discuss the limitations of the current research and propose new perspectives and directions for future studies.

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.

The association between oral microbiome and gastric precancerous lesions

Gastric precancerous lesions are thought to be precursors in the occurrence and development of gastric cancer through Correa's cascade. Recent studies have investigated the association between the oral microbiome and gastric precancerous lesions. However, there has yet to be a comprehensive synthesis review of the existing literature on the relationship between oral microbiome and gastric precancerous lesions. A systematic review was conducted to characterize the literature on the association between oral microbiome and gastric precancerous lesions. The studies show that oral microbiome is dynamic in individuals with gastric precancerous lesions. Oral-derived microorganisms were colonized in the gastric precancerous lesions. Interactions between oral and gastric microbiomes affect the response of the host immunity. The abnormal proliferation of oral-associated microorganisms may be linked to the reduction of gastric acid. The present review supports the potential association between oral microbiome and gastric precancerous lesions. However, the interactions are complex and multifaceted, which require further investigation.

The dynamic oral-gastric microbial axis connects oral and gastric health: current evidence and disputes

Emerging evidence indicates that oral microbes are closely related to gastric microbes and gastric lesions, including gastric atrophy, intestinal metaplasia and gastric cancer (GC). Helicobacter pylori is a key pathogen involved in GC. However, the increasing prevalence of H. pylori-negative GC and gastric dysbiosis in GC patients emphasize the potential role of other microbial factors. In this review, we discussed the current evidence about the relationship between the oral-gastric microbial axis and oral and gastric health. Epidemiologic evidence indicates that poor oral hygiene is related to greater GC risk. Multiple oral-associated microbes are enriched in the stomach of GC patients. Once colonizing the stomach, oral-associated microbes Streptococcus anginosus and Prevotella melaninogenica, are involved in gastric inflammation or carcinogenesis. Microbial metabolites such as lactate, nitrite, and acetaldehyde promote malignant transformation. The stomach, as a checkpoint of microbial transmission in the digestive tract, is of great importance since the link between oral microbes and intestinal diseases has been emphasized. Still, new technologies and standardized metrics are necessary to identify potential pathogenetic microbes for GC and the core microbiota, interactions, richness, colonization, location and effect (CIRCLE). In the future, oral microbes could be candidates for noninvasive indicators to predict gastric diseases.

Review Article: Disrupted Oral Microbiota and Its Implications in Cancer Onset and Progression: A Narrative Review

The oral microbiota plays a pivotal role in maintaining oral health, but its dysbiosis has been increasingly implicated in the development of systemic diseases, including cancer. Emerging evidence highlights the potential contribution of oral microorganisms to carcinogenesis in the oral cavity and distant organs, such as the lungs, pancreas, and genitourinary tract. This review explores the mechanisms through which the oral microbiota influences cancer development and treatment response, mainly driven by microbial translocation, systemic inflammation, immune modulation, and the release of carcinogenic metabolites. Additionally, the review discusses how oral microbiota perturbations interact with host factors, such as diet, systemic diseases, genetics, and cancer therapies, to influence tumor initiation, progression, and response to treatment. A critical analysis of past and emerging literature shows that specific microbial taxa potentially influence tumor progression and immune responses, including Fusobacterium, Porphyromonas, Aggregatibacter and Treponema. The detection of these microorganisms and the study of oral microbiome profiling in cancer care may offer new diagnostic and therapeutic strategies; however, further studies with homogeneous patient populations are needed to fully understand the contributions of oral dysbiosis in cancer development and treatment responses.

Periodontal conditions and salivary microbiota are potential indicators to distinguish silicosis: an exploratory study

BACKGROUND

Silicosis has always been a serious global occupational health problem. Oral microbiota plays important roles in the development of lung disease. However, few studies have investigated the relationship between periodontal conditions, oral bacteria and silicosis disease.

METHOD

A single-center and cross-sectional study was conducted in 2019 in Sichuan Province, China, including a small sample of silicosis patient group and healthy control group. Demographic data and periodontal examinations measured by clinical attachment loss (CAL), bleeding on probing (BOP) and periodontal pocket (PD) were collected from each participant. Phenotypic changes were detected by histopathological staining. Next-generation sequencing targeting 16S ribosomal RNA was targeted to decipher the salivary microbiome of the two groups. Random forest, Least Absolute Shrinkage and Selection Operator (LASSO) logistic regression and multivariable logistic regression analysis were conducted to find potential indicators to distinguish silicosis.

RESULTS

In general, 29 male healthy controls and 24 male silicosis patients were included. The proportion of CAL ≥ 3 mm in silicosis group was greater than control group, while the proportion of BOP (+) and PD ≥ 4 mm was reduced in silicosis group. The α-smooth muscle actin and fibronectin expression increased in gingiva of patients. The composition of salivary microbiota exhibited significant differences between the two groups, with silicosis patients demonstrating a lower diversity of salivary microbiota. Genus of Aggregatibacter [odds ratio (OR) = 0.000, p = 0.003] and Catonella (OR = 0.000, p = 0.049) were identified as biomarkers to distinguish silicosis.

CONCLUSIONS

The silicosis group exhibited worse CAL, improved BOP and PD, which may be related to the gingival fibrosis found in this study. The composition of the oral microbiota underwent significant changes, accompanied by a decrease in diversity, in patients with silicosis. Our study indicates that respirable crystalline silica exposure affects oral health, and alterations of oral microbiota might be implicated in silicosis. We primarily identified Aggregatibacter and Catonella as the potential indicators to distinguish silicosis patients from healthy controls.