Interdisciplinary insights into the link between gut microbiome and gastric carcinogenesis-what is currently known?

Regulatory mechanisms and potential therapeutic targets in precancerous lesions of gastric cancer: A comprehensive review

Precancerous lesions of gastric cancer (PLGC) represent a critical pathological stage in the transformation from normal gastric mucosa to gastric cancer (GC). The global incidence of PLGC has been rising over the past few decades, with a trend towards younger onset ages. Increasing evidence suggests that early prevention and treatment of PLGC can effectively reverse the malignant development of gastric mucosal epithelial cells. However, there is currently a lack of effective therapeutic drugs and methods. Recent years have witnessed substantial advancements in PLGC research, with the elucidation of novel regulatory mechanisms offering promising avenues for clinical intervention and drug development. This review aims to delineate potential targets for early prevention and diagnosis of GC while exploring innovative approaches to PLGC management. This article focuses on elucidating the regulatory mechanisms of the inflammatory microenvironment, bile acids (BA), glycolysis, autophagy, apoptosis, ferroptosis, and cellular senescence. We pay particular attention to potential therapeutic targets for PLGC, with the goal of providing insights and theoretical basis for clinical research on PLGC.

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

The gastric microbial community plays a fundamental role in gastric cancer (GC), and the two main anatomical subtypes of GC, non-cardia and cardia GC, are associated with different risk factors (Helicobacter pylori for non-cardia GC). To decipher the different microbial spatial communities of GC, we performed a multicenter retrospective analysis to characterize the gastric microbiota in 223 GC patients, including H. pylori-positive or -negative patients, with tumors and paired adjacent normal tissues, using third-generation sequencing. In the independent validation cohort, both dental plaque and GC tumoral tissue samples were collected and sequenced. The prevalence of H. pylori and oral-associated bacteria was verified using fluorescence in situ hybridization (FISH) assays in GC tumoral tissues and matched nontumoral tissues. We found that the vertical distribution of the gastric microbiota, at the upper, middle, and lower third sites of GC, was likely an important factor causing microbial diversity in GC tumor tissues. The oral-associated microbiota cluster, which included Veillonella parvula, Streptococcus oralis, and Prevotella intermedia, was more abundant in the upper third of the GC. However, H. pylori was more abundant in the lower third of the GC and exhibited a significantly high degree of microbial correlation. The oral-associated microbiota module was co-exclusive with H. pylori in the lower third site of the GC tumoral tissue. Importantly, H. pylori-negative GC patients with oral-associated gastric microbiota showed worse overall survival, while the increase in microbial abundance in H. pylori-positive GC patients showed no difference in overall survival. The prevalence of V. parvula in both the dental plaque and GC tissue samples was concordant in the independent validation phase. We showed that the oral-associated species V. parvula and S. oralis were correlated with overall survival. Our study highlights the roles of the oral-associated microbiota in the upper third of the GC. In addition, oral-associated species may serve as noninvasive screening tools for the management of GC and an independent prognostic factor for H. pylori-negative GCs.

IMPORTANCE

Our study highlights the roles of the oral-associated microbiota in the upper third of gastric cancer (GC).We showed that the oral-associated species Veillonella parvula and Streptococcus oralis were correlated with overall survival. In addition, oral-associated species may serve as noninvasive screening tools for the management of GC and an independent prognostic factor for Helicobacter pylori-negative GCs.

The demethylase ALKBH5 mediates ZKSCAN3 expression through the m6A modification to activate VEGFA transcription and thus participates in MNNG-induced gastric cancer progression

N-Nitroso compounds (NOCs) are recognized as important factors that promote gastric cancer development, but the specific effects and potential mechanisms by which NOC exposure promotes gastric cancer are still poorly understood. In this study, we explored the effects and potential molecular mechanisms of NOCs on the promotion of gastric cancer using methylnitronitrosoguanidine (MNNG), a classical direct carcinogen of NOC. The results of in vivo and in vitro experiments showed that chronic and low-concentration MNNG exposure significantly promoted the malignant progression of tumors, including cell migration, cell invasion, vasculogenic mimicry (VM) formation, cell spheroid formation, stem cell-like marker expression, and gastric cancer growth and metastasis. Mechanistically, we revealed that demethylase ALKBH5 regulated the level of the N6‑methyladenosine (m6A) modification in the 3'UTR and CDS region of the ZKSCAN3 mRNA to promote ZKSCAN3 expression, mediated the binding of ZKSCAN3 to the VEGFA promoter region to regulate VEGFA transcription, and participated in MNNG-induced gastric cancer cell migration, invasion, VM formation, cell spheroid formation, stem cell-like marker expression and ultimately gastric cancer progression. In addition, our study revealed that ALKBH5-ZKSCAN3-VEGFA signaling was significantly activated during MNNG-induced gastric carcinogenesis, and further studies in gastric cancer patients showed that ALKBH5, ZKSCAN3, and VEGFA expression were upregulated in cancers compared with paired gastric mucosal tissues, that ALKBH5, ZKSCAN3, and VEGFA could serve as important biomarkers for determining patient prognosis, and that the molecular combination showed greater prognostic value. These findings provide a theoretical basis for developing gastric cancer interventions for NOCs and for determining gastric cancer progression.

The role of microbiota in gastric cancer: A comprehensive review

BACKGROUND

Gastric cancer (GC) continues to pose a significant global threat in terms of cancer-related fatalities. Despite notable advancements in medical research and therapies, further investigation is warranted to elucidate its underlying etiology and risk factors. Recent times have witnessed an escalated emphasis on comprehending the role of the microbiota in cancer development.

METHODS

This review briefly delves into recent developments in microbiome-related research pertaining to gastric cancer.

RESULTS

According to studies, the microbiota can influence GC growth by inciting inflammation, disrupting immunological processes, and generating harmful microbial metabolites. Furthermore, there is ongoing research into how the microbiome can impact a patient's response to chemotherapy and immunotherapy.

CONCLUSION

The utilization of the microbiome for detecting, preventing, and managing stomach cancer remains an active area of exploration.

The role of metal ions in the occurrence, progression, drug resistance, and biological characteristics of gastric cancer

Metal ions exert pivotal functions within the human body, encompassing essential roles in upholding cell structure, gene expression regulation, and catalytic enzyme activity. Additionally, they significantly influence various pathways implicated in divergent mechanisms of cell death. Among the prevailing malignant tumors of the digestive tract worldwide, gastric cancer stands prominent, exhibiting persistent high mortality rates. A compelling body of evidence reveals conspicuous ion irregularities in tumor tissues, encompassing gastric cancer. Notably, metal ions have been observed to elicit distinct contributions to the progression, drug resistance, and biological attributes of gastric cancer. This review consolidates pertinent literature on the involvement of metal ions in the etiology and advancement of gastric cancer. Particular attention is directed towards metal ions, namely, Na, K, Mg, Ca, Fe, Cu, Zn, and Mn, elucidating their roles in the initiation and progression of gastric cancer, cellular demise processes, drug resistance phenomena, and therapeutic approaches.

Gut microbiota in gastric cancer: A determinant of etiology or a therapeutic approach?

The impact of the gut microbiota on the well-being and pathology of the host has garnered growing interest. In recent times, there has been a surge in understanding the mechanistic connections between the gut microbiota and cancer, particularly in relation to the genesis, progression, and therapeutic approaches for gastric cancer. The dysbiosis of the intestinal microbiome stands as a significant determinant in the etiology of gastric cancer. Currently, a preliminary consensus exists, although the precise mechanism remains incompletely understood. As research progresses, it becomes increasingly evident that intestinal flora significantly contributes to the therapeutic approach for gastric cancer. This paper gives a comprehensive review of the impact of intestinal flora on gastric cancer, examines the role of the intestinal microbiome in the management of gastric cancer, and elucidates the potential of utilizing the intestinal microbiome as an anti-tumor therapy, with an aim to furnish a point of reference and stimulate future research endeavors.

The role of gastric microecological dysbiosis in gastric carcinogenesis

Gastric cancer (GC) is the leading cause of cancer-related death worldwide, and reducing its mortality has become an urgent public health issue. Gastric microecological dysbiosis (including bacteria, fungi, viruses, acid suppressants, antibiotics, and surgery) can lead to gastric immune dysfunction or result in a decrease in dominant bacteria and an increase in the number and virulence of pathogenic microorganisms, which in turn promotes development of GC. This review analyzes the relationship between gastric microecological dysbiosis and GC, elucidates dynamic alterations of the microbiota in Correa's cascade, and identifies certain specific microorganisms as potential biomarkers of GC to aid in early screening and diagnosis. In addition, this paper presents the potential of gastric microbiota transplantation as a therapeutic target for gastric cancer, providing a new direction for future research in this field.

Autoimmunity and Carcinogenesis: Their Relationship under the Umbrella of Autophagy

The immune system and autophagy share a functional relationship. Both innate and adaptive immune responses involve autophagy and, depending on the disease’s origin and pathophysiology, it may have a detrimental or positive role on autoimmune disorders. As a “double-edged sword” in tumors, autophagy can either facilitate or impede tumor growth. The autophagy regulatory network that influences tumor progression and treatment resistance is dependent on cell and tissue types and tumor stages. The connection between autoimmunity and carcinogenesis has not been sufficiently explored in past studies. As a crucial mechanism between the two phenomena, autophagy may play a substantial role, though the specifics remain unclear. Several autophagy modifiers have demonstrated beneficial effects in models of autoimmune disease, emphasizing their therapeutic potential as treatments for autoimmune disorders. The function of autophagy in the tumor microenvironment and immune cells is the subject of intensive study. The objective of this review is to investigate the role of autophagy in the simultaneous genesis of autoimmunity and malignancy, shedding light on both sides of the issue. We believe our work will assist in the organization of current understanding in the field and promote additional research on this urgent and crucial topic.

Nutrition and Microbiome Interactions in Human Cancer

Individual physiologic responses to changes in dietary patterns can vary widely to affect cancer risk, which is driven by multiple host-specific factors (eg, genetics, epigenetics, inflammatory and metabolic states, and the colonizing microbiome). Emerging evidence indicates that diet-induced microbiota alterations are key modulators of several host functions important to tumor etiology, progression, and response to cancer therapy. Thus, diet may potentially be used to target alterations of the microbiota as an effective means to improve outcomes across the cancer continuum (from cancer prevention to tumor development and progression, to effects on treatment and survivorship). This review will focus on recent examples of functional interactions between dietary components (nutrients and non-nutrients) and the gastrointestinal microbiome, which are 2 critical and malleable environmental variables in cancer risk that affect host immune, metabolic, and cell signaling functions and may provide insights for novel cancer therapeutic and preventive strategies.

New Insights into the Relationship between Gut Microbiota and Radiotherapy for Cancer

Cancer is the second most common cause of death among humans in the world, and the threat that it presents to human health is becoming more and more serious. The mechanisms of cancer development have not yet been fully elucidated, and new therapies are changing with each passing day. Evidence from the literature has validated the finding that the composition and modification of gut microbiota play an important role in the development of many different types of cancer. The results also demonstrate that there is a bidirectional interaction between the gut microbiota and radiotherapy treatments for cancer. In a nutshell, the modifications of the gut microbiota caused by radiotherapy have an effect on tumor radiosensitivity and, as a result, affect the efficacy of radiotherapy and show a certain radiation toxicity, which leads to numerous side effects. What is of new research significance is that the "gut-organ axis" formed by the gut microbiota may be one of the most interesting potential mechanisms, although the relevant research is still very limited. In this review, we combine new insights into the relationship between the gut microbiota, cancer, and radiotherapy. Based on our current comprehensive understanding of this relationship, we give an overview of the new cancer treatments based on the gut microbiota.

Metabolic alterations of short-chain fatty acids and TCA cycle intermediates in human plasma from patients with gastric cancer

AIMS

Short-chain fatty acids (SCFAs) are produced by gut microbiota from dietary fiber. Since absorbed SCFAs could be introduced into the tricarboxylic acid (TCA) cycle in host cells, the relationships between SCFAs and TCA cycle intermediates might influence to energy metabolism in the human body. For this reason, information on profile changes between SCFAs and TCA cycle intermediates could help unveil pathological mechanisms of gastric cancer.

MAIN METHODS

A gas chromatography-tandem mass spectrometry (GC-MS/MS) method was developed to simultaneously determine SCFAs and TCA cycle intermediates in human plasma from patients with chronic superficial gastritis (CSG), intestinal metaplasia (IM), and gastric cancer. We applied a tetra-alkyl ammonium pairing method to prevent loss of volatile SCFAs and base decarboxylation of TCA cycle intermediates during sample preparation. To assess gastric diseases, metabolic alterations of SCFAs and TCA cycle intermediates in human plasma with gastric disorders were analyzed by their plasma levels.

KEY FINDINGS

Significantly different metabolic alterations based on the plasma levels of SCFAs and TCA cycle intermediates were investigated in cancer metabolic pathways. Not only propionate and butyrate, mainly produced by gut microbiota, were significantly decreased, but also cis-aconitate, α-ketoglutarate, and fumarate were significantly increased in plasma with IM or gastric cancer, compared to CSG. Further, based on ratios of product to precursor, three metabolic pathways (succinate/propionate, succinate/α-ketoglutarate, and cis-aconitate/citrate) were supposed to be distorted between gastric diseases.

SIGNIFICANCE

In conclusion, propionate, cis-aconitate, α-ketoglutarate, and fumarate could be used to assess the progression of gastric cancer.

Viral Infection in Esophageal, Gastric, and Colorectal Cancer

The human gastrointestinal tract, which constitutes the digestive system, contains a large number of virus particles that maintain organizational homeostasis and health. Conversely, viral pathogens have also attracted attention for their involvement in the pathogenesis of certain cancers, including gastrointestinal cancers. To aid prevention and treatment of these cancers, the relevance of gastrointestinal viral factors as potential risk factors needs to be carefully investigated. This review summarizes and discusses the available literature on the relationship between the development of esophageal, gastric, and colorectal cancers and their corresponding viruses. This review reveals that research on the association between colorectal cancer and viruses, in particular, is still in its infancy compared to the association between HPV and esophageal cancer and between EBV and gastric cancer.

A positive feedback loop between gastric cancer cells and tumor-associated macrophage induces malignancy progression

BACKGROUND

Hypoxia and inflammation tumor microenvironment (TME) play a crucial role in tumor development and progression. Although increased understanding of TME contributed to gastric cancer (GC) progression and prognosis, the direct interaction between macrophage and GC cells was not fully understood.

METHODS

Hypoxia and normoxia macrophage microarrays of GEO database was analyzed. The peripheral blood mononuclear cell acquired from the healthy volunteers. The expression of C-X-C Motif Chemokine Ligand 8 (CXCL8) in GC tissues and cell lines was detected by quantitative reverse transcription PCR (qRT-PCR), western-blot, Elisa and immunofluorescence. Cell proliferation, migration, and invasion were evaluated by cell counting kit 8 (CCK8), colony formation, real-time imaging of cell migration and transwell. Flow Cytometers was applied to identify the source of cytokines. Luciferase reporter assays and chromatin immunoprecipitation were used to identify the interaction between transcription factor and target gene. Especially, a series of truncated and mutation reporter genes were applied to identify precise binding sites. The corresponding functions were verified in the complementation test and in vivo animal experiment.

RESULTS

Our results revealed that hypoxia triggered macrophage secreted CXCL8, which induced GC invasion and proliferation. This macrophage-induced GC progression was CXCL8 activated C-X-C Motif Chemokine Receptor 1/2 (CXCR1/2) on the GC cell membrane subsequently hyperactivated Janus kinase 1/ Signal transducer and activator of transcription 1 (JAK/STAT1) signaling pathway. Then, the transcription factor STAT1 directly led to the overexpression and secretion of Interleukin 10 (IL-10). Correspondingly, IL-10 induced the M2-type polarization of macrophages and continued to increase the expression and secretion of CXCL8. It suggested a positive feedback loop between macrophage and GC. In clinical GC samples, increased CXCL8 predicted a patient's pessimistic outcome.

CONCLUSION

Our work identified a positive feedback loop governing cancer cells and macrophage in GC that contributed to tumor progression and patient outcome.

Autoimmunity and Cancer-Two Sides of the Same Coin

Autoimmune disease results from the immune response against self-antigens, while cancer develops when the immune system does not respond to malignant cells. Thus, for years, autoimmunity and cancer have been considered as two separate fields of research that do not have a lot in common. However, the discovery of immune checkpoints and the development of anti-cancer drugs targeting PD-1 (programmed cell death receptor 1) and CTLA-4 (cytotoxic T lymphocyte antigen 4) pathways proved that studying autoimmune diseases can be extremely helpful in the development of novel anti-cancer drugs. Therefore, autoimmunity and cancer seem to be just two sides of the same coin. In the current review, we broadly discuss how various regulatory cell populations, effector molecules, genetic predisposition, and environmental factors contribute to the loss of self-tolerance in autoimmunity or tolerance induction to cancer. With the current paper, we also aim to convince the readers that the pathways involved in cancer and autoimmune disease development consist of similar molecular players working in opposite directions. Therefore, a deep understanding of the two sides of immune tolerance is crucial for the proper designing of novel and selective immunotherapies.

The Association Between the Gut Microbiome, Nutritional Habits, Antibiotics, and Gastric Cancer: a Scoping Review

 PURPOSE OF REVIEW: Gastric cancer (GC) represents one of the leading causes of cancer-related deaths worldwide. The prevalence of GC among the younger population has been increasing in recent years, and the latter is associated with late detection and advanced disease status. The factors involved in the development of GC have been the focus of investigation in the past few years; yet no consistent conclusions or preventative solutions have been suggested. This scoping review aims to explore and report on research studies conducted to investigate the association between GC, the gut microbiome, and nutritional habits. RECENT FINDINGS : Using a predefined protocol in compliance with the PRISMA guidelines, a search was conducted on four separate databases including Google Scholar, Cochrane Library, ProQuest, and PubMed to investigate the association between GC, microbiome, and nutrition. A total of 1219 articles were identified through this process. Forty-three articles met the initial screening criteria and following full-article analysis, and 10 articles met the full inclusion criteria and were included in the current review. The results of the study support that there are differences in the gut microbiota between GC patients and healthy controls and that GC patients may have increased microbiota richness and lower diversity compared to healthy controls. In addition, the detection of pre/early GC may be possible through the analysis of the microbiota using fecal sampling. Nutritional habits, probiotics, and antibiotics may also play an important role in affecting GC development. Preliminary studies support a role for the gut microbiota in developing GC. Yet, the lack of sufficient randomized controlled studies investigating the association between GC, the gut microbiota, and nutritional habits demonstrates the need for further clinical research to develop preventative strategies that will aim to reduce the increased incidence of GC among all age groups including younger populations.