Role of the Gastric Microbiome in Gastric Cancer: From Carcinogenesis to Treatment

Oro-Respiratory Dysbiosis and Its Modulatory Effect on Lung Mucosal Toxicity during Exposure or Co-Exposure to Carbon Nanotubes and Cigarette Smoke

The oro-respiratory microbiome is impacted by inhalable exposures such as smoking and has been associated with respiratory health conditions. However, the effect of emerging toxicants, particularly engineered nanoparticles, alone or in co-exposure with smoking, is poorly understood. Here, we investigated the impact of sub-chronic exposure to carbon nanotube (CNT) particles, cigarette smoke extract (CSE), and their combination. The oral, nasal, and lung microbiomes were characterized using 16S rRNA-based metagenomics. The exposures caused the following shifts in lung microbiota: CNT led to a change from Proteobacteria and Bacteroidetes to Firmicutes and Tenericutes; CSE caused a shift from Proteobacteria to Bacteroidetes; and co-exposure (CNT+CSE) had a mixed effect, maintaining higher numbers of Bacteroidetes (due to the CNT effect) and Tenericutes (due to the CSE effect) compared to the control group. Oral microbiome analysis revealed an abundance of the following genera: Acinetobacter (CNT), Staphylococcus, Aggregatibacter, Allobaculum, and Streptococcus (CSE), and Alkalibacterium (CNT+CSE). These proinflammatory microbial shifts correlated with changes in the relative expression of lung mucosal homeostasis/defense proteins, viz., aquaporin 1 (AQP-1), surfactant protein A (SP-A), mucin 5b (MUC5B), and IgA. Microbiota depletion reversed these perturbations, albeit to a varying extent, confirming the modulatory role of oro-respiratory dysbiosis in lung mucosal toxicity. This is the first demonstration of specific oro-respiratory microbiome constituents as potential modifiers of toxicant effects in exposed lungs.

Hepatitis B virus-related hepatocellular carcinoma exhibits distinct intratumoral microbiota and immune microenvironment signatures

Emerging evidence supports a high prevalence of cancer type-specific microbiota residing within tumor tissues. The intratumoral microbiome in hepatocellular carcinoma (HCC), especially in viral (hepatitis B virus [HBV]/hepatitis C virus [HCV]) HCC, has not been well characterized for their existence, composition, distribution, and biological functions. We report herein a finding of specific microbial signature in viral HCC as compared to non-HBV/non-HCV (NBNC) HCC. However, the significantly diverse tumor microbiome was only observed in HBV-related HCC, and Cutibacterium was identified as the representative taxa biomarker. Biological function of the unique tumor microbiota in modulating tumor microenvironment (TME) was characterized by using formalin-fixed paraffin-embedded (FFPE) tissue-based multiplex immunofluorescence histochemistry (mIFH) allowing simultaneous in situ detection of the liver cancer cells surrounded with high/low density of microbiota, and the infiltrating immune cells. In HBV_HCC, the intratumoral microbiota are positively associated with increased tumor-infiltrating CD8+ T lymphocytes, but not the CD56+ NK cells. Two subtypes of myeloid-derived suppressor cells (MDSCs): monocytic MDSCs and polymorphonuclear MDSCs, were also found to be positively correlated with the intratumoral microbiota in HBV_HCC, indicating an inhibitory role of these microbial species in antitumor immunity and the contribution to the liver TME in combination of chronic viral hepatitis during HCC development.

The role of microbiomes in gastrointestinal cancers: new insights

Gastrointestinal (GI) cancers constitute more than 33% of new cancer cases worldwide and pose a considerable burden on public health. There exists a growing body of evidence that has systematically recorded an upward trajectory in GI malignancies within the last 5 to 10 years, thus presenting a formidable menace to the health of the human population. The perturbations in GI microbiota may have a noteworthy influence on the advancement of GI cancers; however, the precise mechanisms behind this association are still not comprehensively understood. Some bacteria have been observed to support cancer development, while others seem to provide a safeguard against it. Recent studies have indicated that alterations in the composition and abundance of microbiomes could be associated with the progression of various GI cancers, such as colorectal, gastric, hepatic, and esophageal cancers. Within this comprehensive analysis, we examine the significance of microbiomes, particularly those located in the intestines, in GI cancers. Furthermore, we explore the impact of microbiomes on various treatment modalities for GI cancer, including chemotherapy, immunotherapy, and radiotherapy. Additionally, we delve into the intricate mechanisms through which intestinal microbes influence the efficacy of GI cancer treatments.

Gut microbiome-derived butyrate inhibits the immunosuppressive factors PD-L1 and IL-10 in tumor-associated macrophages in gastric cancer

Early detection and surgical treatment are essential to achieve a good outcome in gastric cancer (GC). Stage IV and recurrent GC have a poor prognosis. Therefore, new treatments for GC are needed. We investigated the intestinal microbiome of GC patients and attempted to reverse the immunosuppression of the immune and cancer cells of GC patients through the modulation of microbiome metabolites. We evaluated the levels of programmed death-ligand 1 (PD-L1) and interleukin (IL)-10 in the peripheral blood immunocytes of GC patients. Cancer tissues were obtained from patients who underwent surgical resection of GC, and stained sections of cancer tissues were visualized via confocal microscopy. The intestinal microbiome was analyzed using stool samples of healthy individuals and GC patients. Patient-derived avatar model was developed by injecting peripheral blood mononuclear cells (PBMCs) from advanced GC (AGC) patients into NSG mice, followed by injection of AGS cells. PD-L1 and IL-10 had higher expression levels in immune cells of GC patients than in those of healthy controls. The levels of immunosuppressive factors were increased in the immune and tumor cells of tumor tissues of GC patients. The abundances of Faecalibacterium and Bifidobacterium in the intestinal flora were lower in GC patients than in healthy individuals. Butyrate, a representative microbiome metabolite, suppressed the expression levels of PD-L1 and IL-10 in immune cells. In addition, the PBMCs of AGC patients showed increased levels of immunosuppressive factors in the avatar mouse model. Butyrate inhibited tumor growth in mice. Restoration of the intestinal microbiome and its metabolic functions inhibit tumor growth and reverse the immunosuppression due to increased PD-L1 and IL-10 levels in PBMCs and tumor cells of GC patients.

Leveraging immunoinformatics for developing a multi-epitope subunit vaccine against Helicobacter pylori and Fusobacterium nucleatum

Gastric ulcers caused by Helicobacter pylori and Fusobacterium nucleatum remain a significant global health concern without an established vaccine. In this study, we utilized immunoinformatics methods to design a multi-epitope vaccine targeting these pathogens. Outer membrane proteins from H. pylori and F. nucleatum were scrutinized to identify high antigenic T-cell and B-cell epitopes. The resulting vaccine comprised carefully analyzed and evaluated epitopes, including cytotoxic T-lymphocytes, helper T-lymphocytes, and linear B-lymphocytes epitopes. This vaccine exhibited notable antigenicity, suitable immunogenicity, and demonstrated non-allergenicity and non-toxicity. It displayed favorable physiochemical characteristics and high solubility. In interaction studies, the vaccine exhibited robust binding to toll-like receptor 4 (TLR4). Molecular dynamic simulations revealed cohesive structural integrity and stable attachment. Codon adaptation utilizing Escherichia coli K12 host yielded a vaccine with elevated Codon Adaptation Index (CAI) and optimal GC content. In silico cloning into the pET28+(a) vector demonstrated efficient expression. Immune simulations indicated the vaccine's ability to initiate immune responses in humans, mirroring real-life scenarios. Based on these comprehensive findings, we propose that our developed vaccine has the potential to confer robust immunity against H. pylori and F. nucleatum infections.Communicated by Ramaswamy H. Sarma.

Predicting Personalized Diets Based on Microbial Characteristics between Patients with Superficial Gastritis and Atrophic Gastritis

BACKGROUND

gastritis is a common stomach disease with a high global incidence and can potentially develop into gastric cancer. The treatment of gastritis focuses on medication or diets based on national guidelines. However, the specific diet that can alleviate gastritis remains largely unknown.

METHODS

we propose a microbiota-directed dietary strategy that investigates potential food factors using microbial exogenous metabolites. Given the current lack of understanding of the repeatable characteristics of gastric microbiota, we conducted a meta-analysis to identify the features of gastric bacteria. Local samples were collected as validation cohorts. Furthermore, RevEcoR was employed to identify bacteria's exogenous metabolites, and FooDB was used to retrieve foods that can target specific bacteria.

RESULTS

Bacteroides, Weissella, Actinomyces, Atopobium, Oribacterium, Peptostreptococcus, and Rothia were biomarkers between superficial gastritis (SG) and atrophic gastritis (AG) (AG_N) without H. pylori infection, whereas Bacillus, Actinomyces, Cutibacterium, Helicobacter, Novosphingobium, Pseudomonas, and Streptococcus were signatures between SG and AG (AG_P) with H. pylori infection. According to the exogenous metabolites, adenosyloobalamin, soybean, common wheat, dates, and barley were regarded as potential candidates for AG_N treatment, while gallate was regarded as a candidate for AG_P treatment.

CONCLUSIONS

this study firstly profiled the gastric microbiota of AG and SG with or without H. pylori and provided a recommended diet for global AG according to exogenous metabolites.

Microbial-Related Metabolites May Be Involved in Eight Major Biological Processes and Represent Potential Diagnostic Markers in Gastric Cancer

Metabolites associated with microbes regulate human immunity, inhibit bacterial colonization, and promote pathogenicity. Integrating microbe and metabolome research in GC provides a direction for understanding the microbe-associated pathophysiological process of metabolic changes and disease occurrence. The present study included 30 GC patients with 30 cancerous tissues and paired non-cancerous tissues (NCs) as controls. LC-MS/MS metabolomics and 16S rRNA sequencing were performed to obtain the metabolic and microbial characteristics. Integrated analysis of the microbes and metabolomes was conducted to explore the coexistence relationship between the microbial and metabolic characteristics of GC and to identify microbial-related metabolite diagnostic markers. The metabolic analysis showed that the overall metabolite distribution differed between the GC tissues and the NC tissues: 25 metabolites were enriched in the NC tissues and 42 metabolites were enriched in the GC tissues. The α and β microbial diversities were higher in the GC tissues than in the NC tissues, with 11 differential phyla and 52 differential genera. In the correlation and coexistence integrated analysis, 66 differential metabolites were correlated and coexisted, with specific differential microbes. The microbes in the GC tissue likely regulated eight metabolic pathways. In the efficacy evaluation of the microbial-related differential metabolites in the diagnosis of GC, 12 differential metabolites (area under the curve [AUC] >0.9) exerted relatively high diagnostic efficiency, and the combined diagnostic efficacy of 5 to 6 microbial-related differential metabolites was higher than the diagnostic efficacy of a single feature. Therefore, microbial diversity and metabolite distribution differed between the GC tissues and the NC tissues. Microbial-related metabolites may be involved in eight major metabolism-based biological processes in GC and represent potential diagnostic markers.

Diversification and deleterious role of microbiome in gastric cancer

Gut microbiota dictates the fate of several diseases, including cancer. Most gastric cancers (GC) belong to gastric adenocarcinomas (GAC). Helicobacter pylori colonizes the gastric epithelium and is the causative agent of 75% of all stomach malignancies globally. This bacterium has several virulence factors, including cytotoxin-associated gene A (CagA), vacuolating cytotoxin (VacA), and outer membrane proteins (OMPs), all of which have been linked to the development of gastric cancer. In addition, bacteria such as Escherichia coli, Streptococcus, Clostridium, Haemophilus, Veillonella, Staphylococcus, and Lactobacillus play an important role in the development of gastric cancer. Besides, lactic acid bacteria (LAB) such as Bifidobacterium, Lactobacillus, Lactococcus, and Streptococcus were found in greater abundance in GAC patients. To identify potential diagnostic and therapeutic interventions for GC, it is essential to understand the mechanistic role of H. pylori and other bacteria that contribute to gastric carcinogenesis. Furthermore, understanding bacteria-host interactions and bacteria-induced inflammatory pathways in the host is critical for developing treatment targets for gastric cancer.

Exploring the Microbiome in Gastric Cancer: Assessing Potential Implications and Contextualizing Microorganisms beyond H. pylori and Epstein-Barr Virus

While previous research has primarily focused on the impact of H. pylori and Epstein-Barr virus (EBV), emerging evidence suggests that other microbial influences, including viral and fungal infections, may also contribute to gastric cancer (GC) development. The intricate interactions between these microbes and the host's immune response provide a more comprehensive understanding of gastric cancer pathogenesis, diagnosis, and treatment. The review highlights the roles of established players such as H. pylori and EBV and the potential impacts of gut bacteria, mainly Lactobacillus, Streptococcus, hepatitis B virus, hepatitis C virus, and fungi such as Candida albicans. Advanced sequencing technologies offer unprecedented insights into the complexities of the gastric microbiome, from microbial diversity to potential diagnostic applications. Furthermore, the review highlights the potential for advanced GC diagnosis and therapies through a better understanding of the gut microbiome.

Advancing our understanding of the influence of drug induced changes in the gut microbiome on bone health

The gut microbiome has been implicated in a multitude of human diseases, with emerging evidence linking its microbial diversity to osteoporosis. This review article will explore the molecular mechanisms underlying perturbations in the gut microbiome and their influence on osteoporosis incidence in individuals with chronic diseases. The relationship between gut microbiome diversity and bone density is primarily mediated by microbiome-derived metabolites and signaling molecules. Perturbations in the gut microbiome, induced by chronic diseases can alter bacterial diversity and metabolic profiles, leading to changes in gut permeability and systemic release of metabolites. This cascade of events impacts bone mineralization and consequently bone mineral density through immune cell activation. In addition, we will discuss how orally administered medications, including antimicrobial and non-antimicrobial drugs, can exacerbate or, in some cases, treat osteoporosis. Specifically, we will review the mechanisms by which non-antimicrobial drugs disrupt the gut microbiome's diversity, physiology, and signaling, and how these events influence bone density and osteoporosis incidence. This review aims to provide a comprehensive understanding of the complex interplay between orally administered drugs, the gut microbiome, and osteoporosis, offering new insights into potential therapeutic strategies for preserving bone health.

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

The stomach was once considered a sterile organ until the discovery of Helicobacter pylori (HP). With the application of high-throughput sequencing technology and macrogenomics, researchers have identified fungi and fivemajor bacterial phyla within the stomachs of healthy individuals. These microbial communities exert regulatory influence over various physiological functions, including energy metabolism and immune responses. HP is a well-recognized risk factor for gastric cancer, significantly altering the stomach's native microecology. Currently, numerous studies are centered on the mechanisms by which HP contributes to gastric cancer development, primarily involving the CagA oncoprotein. However, aside from exogenous infections such as HP and EBV, certain endogenous dysbiosis can also lead to gastric cancer through multiple mechanisms. Additionally, gut microbiota and its metabolites significantly impact the development of gastric cancer. The role of microbial therapies, including diet, phages, probiotics and fecal microbiota transplantation, in treating gastric cancer should not be underestimated. This review aims to study the mechanisms involved in the roles of exogenous pathogen infection and endogenous microbiota dysbiosis in the development of gastric cancer. Also, we describe the application of microbiota therapy in the treatment and prognosis of gastric cancer.

Changes in salivary microbiota due to gastric cancer resection and its relation to gastric fluid microbiota

Gastric cancer is one of the leading causes of death worldwide, and resections are performed to cure the disease. We have previously reported the changes in the gastric microbiota after gastric cancer resection, which may be associated with the oral microbiota; however, the changes in the oral microbiota remain uncharacterized. This study aimed to characterize the changes in the salivary microbiota caused by gastric cancer resection and to evaluate their association with the gastric fluid microbiota. Saliva and gastric fluid samples were collected from 63 patients who underwent gastrectomy before and after surgery, and a 16S rRNA metagenomic analysis was performed to compare the microbiota composition. The number of bacterial species in the salivary microbiota decreased, and the bacterial composition changed after the resection of gastric cancer. In addition, we identified several bacterial genera that varied significantly in the salivary microbiota, some of which also showed similar changes in the gastric fluid microbiota. These findings indicate that changes in the gastric environment affect the oral microbiota, emphasizing the close association between the oral and gastric fluid microbiota. Our study signifies the importance of focusing on the oral microbiota in the perioperative period of gastrectomy in patients with gastric cancer.

Microbiomes, Their Function, and Cancer: How Metatranscriptomics Can Close the Knowledge Gap

The interaction between the microbial communities in the human body and the onset and progression of cancer has not been investigated until recently. The vast majority of the metagenomics research in this area has concentrated on the composition of microbiomes, attempting to link the overabundance or depletion of certain microorganisms to cancer proliferation, metastatic behaviour, and its resistance to therapies. However, studies elucidating the functional implications of the microbiome activity in cancer patients are still scarce; in particular, there is an overwhelming lack of studies assessing such implications directly, through analysis of the transcriptome of the bacterial community. This review summarises the contributions of metagenomics and metatranscriptomics to the knowledge of the microbial environment associated with several cancers; most importantly, it highlights all the advantages that metatranscriptomics has over metagenomics and suggests how such an approach can be leveraged to advance the knowledge of the cancer bacterial environment.

Crosstalk between Helicobacter pylori and gastrointestinal microbiota in various gastroduodenal diseases-A systematic review

Gastroduodenal diseases have prevailed for a long time and more so due to dominance of gut bacteria Helicobacter pylori in most of the cases. But habitation by other gut microbiota in gastroduodenal diseases and the relationship between Helicobacter pylori and gastrointestinal microbiota in different gastroduodenal diseases is somewhat being unravelled in the current times. For this systematic review, we did a literature search of various gastroduodenal diseases and the effect on gut microbiota pertaining to it. A search of the online bibliographic databases PUBMED and PUBMED CENTRAL was carried out to identify articles published between 1977 and May 2022. The analysis of these selected studies highlighted the inhabitation of other gut microbiota such as Fusobacteria, Bacteroidetes, Streptococcaceae, Prevotellaceae, Fusobacteriaceae, and many others. Interplay between these microbiota and H. pylori have also been noted which suggested that gastroduodenal diseases and gut microbiota are intertwined by a symbiotic association regardless of the H. pylori status. The relationship between the gut microbiota and many gastroduodenal diseases, such as gastritis, gastric cancer, lymphomas, and ulcers, demonstrates the dysbiosis of the gut microbiota in both the presence and absence of H. pylori. The evolving ways for eliminating H. pylori are provided along with inhibiting qualities of other species on H. pylori. Most significant member of our gut system is Helicobacter pylori which has been associated with numerous diseases like gastric cancer, gastritis, duodenal ulcer.

MicroRNA: trends in clinical trials of cancer diagnosis and therapy strategies

As a type of short noncoding RNAs, microRNA (miRNA) undoubtedly plays a crucial role in cancer development. Since the discovery of the identity and clinical functions of miRNAs, over the past few decades, the roles of miRNAs in cancer have been actively investigated. Numerous pieces of evidence indicate that miRNAs are pivotal factors in most types of cancer. Recent cancer research focused on miRNAs has identified and characterized a large cohort of miRNAs commonly dysregulated in cancer or exclusively dysregulated in specific types of cancer. These studies have suggested the potential of miRNAs as biomarkers in the diagnosis and prognostication of cancer. Moreover, many of these miRNAs have oncogenic or tumor-suppressive functions. MiRNAs have been the focus of research given their potential clinical applications as therapeutic targets. Currently, various oncology clinical trials using miRNAs in screening, diagnosis, and drug testing are underway. Although clinical trials studying miRNAs in various diseases have been reviewed before, there have been fewer clinical trials related to miRNAs in cancer. Furthermore, updated results of recent preclinical studies and clinical trials of miRNA biomarkers and drugs in cancer are needed. Therefore, this review aims to provide up-to-date information on miRNAs as biomarkers and cancer drugs in clinical trials.

Unveiling the Human Gastrointestinal Tract Microbiome: The Past, Present, and Future of Metagenomics

Over 10¹⁴ symbiotic microorganisms are present in a healthy human body and are responsible for the synthesis of vital vitamins and amino acids, mediating cellular pathways and supporting immunity. However, the deregulation of microbial dynamics can provoke diverse human diseases such as diabetes, human cancers, cardiovascular diseases, and neurological disorders. The human gastrointestinal tract constitutes a hospitable environment in which a plethora of microbes, including diverse species of archaea, bacteria, fungi, and microeukaryotes as well as viruses, inhabit. In particular, the gut microbiome is the largest microbiome community in the human body and has drawn for decades the attention of scientists for its significance in medical microbiology. Revolutions in sequencing techniques, including 16S rRNA and ITS amplicon sequencing and whole genome sequencing, facilitate the detection of microbiomes and have opened new vistas in the study of human microbiota. Especially, the flourishing fields of metagenomics and metatranscriptomics aim to detect all genomes and transcriptomes that are retrieved from environmental and human samples. The present review highlights the complexity of the gastrointestinal tract microbiome and deciphers its implication not only in cellular homeostasis but also in human diseases. Finally, a thorough description of the widely used microbiome detection methods is discussed.

Current developments in gastric cancer: from molecular profiling to treatment strategy

Gastric cancer and gastro-oesophageal junction cancer represent a global health-care challenge. Despite the efficacy of improved chemotherapy and surgical options, these patients still have a poor prognosis. In advanced disease, only trastuzumab and some immune checkpoint inhibitors, such as nivolumab and pembrolizumab in addition to chemotherapy, have demonstrated consistent and reliable efficacy in patients with HER2-positive and PDL1-positive tumours, respectively. In this Review, we discuss the intrinsic characteristics of gastric and gastro-oesophageal cancer from the molecular and clinical perspectives and provide a comprehensive review of previously reported and ongoing phase II and III clinical trials with targeted agents and immunotherapy in advanced and localized settings. Finally, we suggest alternative strategies to help overcome current challenges in precision medicine and to improve outcomes for these patients.

Shotgun Metagenomics of Gastric Biopsies Reveals Compositional and Functional Microbiome Shifts in High- and Low-Gastric-Cancer-Risk Populations from Colombia, South America

Along with Helicobacter pylori infection, the gastric microbiota is hypothesized to modulate stomach cancer risk in susceptible individuals. Whole metagenomic shotgun sequencing (WMS) is a sequencing approach to characterize the microbiome with advantages over traditional culture and 16S rRNA sequencing including identification of bacterial and non-bacterial taxa, species/strain resolution, and functional characterization of the microbiota. In this study, we used WMS to survey the microbiome in extracted DNA from antral gastric biopsy samples from Colombian patients residing in the high-risk gastric cancer town Túquerres (n = 10, H. pylori-positive = 7) and low-risk town of Tumaco (n = 10, H. pylori-positive = 6). Kraken2/Bracken was used for taxonomic classification and abundance. Functional gene profiles were inferred by InterProScan and KEGG analysis of assembled contigs and gene annotation. The most abundant taxa represented bacteria, non-human eukaryota, and viral genera found in skin, oral, food, and plant/soil environments including Staphylococus, Streptococcus, Bacillus, Aspergillus, and Siphoviridae. H. pylori was the predominant taxa present in H. pylori-positive samples. Beta diversity was significantly different based on H. pylori-status, risk group, and sex. WMS detected more bacterial taxa than 16S rRNA sequencing and aerobic, anaerobic, and microaerobic culture performed on the same gastric biopsy samples. WMS identified significant differences in functional profiles found between H. pylori-status, but not risk or sex groups. H. pylori-positive samples were significantly enriched for H. pylori-specific genes including virulence factors such as vacA, cagA, and urease, while carbohydrate and amino acid metabolism genes were enriched in H. pylori-negative samples. This study shows WMS has the potential to characterize the taxonomy and function of the gastric microbiome as risk factors for H. pylori-associated gastric disease. Future studies will be needed to compare and validate WMS versus traditional culture and 16S rRNA sequencing approaches for characterization of the gastric microbiome.

Morphine use induces gastric microbial dysbiosis driving gastric inflammation through TLR2 signalling which is attenuated by proton pump inhibition

BACKGROUND AND PURPOSE

Opioids are the standard drug for pain management; however, their effects on gastric dysfunction are relatively understudied. Opioid users have a higher incidence of gastric pathology leading to increased hospitalization. Herein, we investigated the consequences of morphine use on gastric pathology and the underlying mechanisms. We further investigated the therapeutic benefit of proton pump inhibition to overcome morphine-mediated gastric inflammation.

EXPERIMENTAL APPROACH

Mice were implanted with 25 mg slow-release morphine and placebo pellets. Gastric microbiome analyses were performed. Gastric damage was assayed. Gastric pH was measured. Germ-free and TLR2KO mice were used to investigate the mechanisms. Gastroprotective studies were performed with the proton pump inhibitor (PPI) omeprazole.

KEY RESULTS

Chronic morphine treatment alters gastric microbial composition and induces preferential expansion of pathogenic bacterial communities such as Streptococcus and Pseudomonas. Morphine causes disruption of the gastric mucosal layer, increases apoptosis, and elevates inflammatory cytokines. Moreover, morphine-mediated gastric pathology was significantly attenuated in germ-free mice, and reconstitution of morphine gastric microbiome in germ-free mice resulted gastric inflammation. In addition, morphine-mediated gastric inflammation was attenuated in TLR2KO mice. Morphine causes a decrease in gastric pH, which contributes to gastric dysbiosis leads to gastric inflammation. Omeprazole treatment inhibits gastric acidity, rescuing morphine-induced gastric dysbiosis and preventing inflammation.

CONCLUSION AND IMPLICATIONS

This study attributes morphine-induced gastric acidity as a driver of gastric dysbiosis and pathology and proposes the therapeutic use of PPI as an inexpensive approach for the clinical management of morphine-associated pathophysiology.

Tumor microbiome - an integral part of the tumor microenvironment

The tumor microenvironment (TME) plays a significant role in tumor progression and cancer cell survival. Besides malignant cells and non-malignant components, including immune cells, elements of the extracellular matrix, stromal cells, and endothelial cells, the tumor microbiome is considered to be an integral part of the TME. Mounting evidence from preclinical and clinical studies evaluated the presence of tumor type-specific intratumoral bacteria. Differences in microbiome composition between cancerous tissues and benign controls suggest the importance of the microbiome-based approach. Complex host-microbiota crosstalk within the TME affects tumor cell biology via the regulation of oncogenic pathways, immune response modulation, and interaction with microbiota-derived metabolites. Significantly, the involvement of tumor-associated microbiota in cancer drug metabolism highlights the therapeutic implications. This review aims to summarize current knowledge about the emerging role of tumor microbiome in various types of solid malignancies. The clinical utility of tumor microbiome in cancer progression and treatment is also discussed. Moreover, we provide an overview of clinical trials evaluating the role of tumor microbiome in cancer patients. The research focusing on the communication between the gut and tumor microbiomes may bring new opportunities for targeting the microbiome to increase the efficacy of cancer treatment and improve patient outcomes.

Mechanism Underlying Metformin Action and Its Potential to Reduce Gastric Cancer Risk

Diabetes mellitus is associated with a high risk of developing gastric cancer (GC). Metformin, which is conventionally used to treat type 2 diabetes, induces AMP-activated protein kinase signaling and suppresses gluconeogenesis. Recent studies have reported that metformin is associated with beneficial effects in cancer prevention and treatment owing to its anti-tumor effects. This makes metformin a potential medication for GC therapy. However, contradicting reports have emerged regarding the efficacy of metformin in reducing the risk of GC. This review summarizes the impact of metformin on mitigating GC risk by analyzing clinical databases. The mechanism underlying the anti-tumor effect of metformin on GC is also discussed.

Intestinal microbial diversity in female rhesus (Macaca mulatta) at different physiological periods

To explore the relationship between the changes in the physiological period and the fecal microbial population of female rhesus monkeys by measuring microbial composition of fecal samples and the serum hormones. Blood and fecal samples were collected from six female adult rhesus monkeys during the menstrual period (MP), ovulation period (OP), and Luteal period (LP). Serum estradiol (E2) and progesterone (P) levels were determined by the chemiluminescence method and the stool samples were subjected to high-throughput 16S rRNA sequencing. The highest level of E2 and P secretions were during the MP, and LP, respectively. Stool samples produced valid sequences and the number of operational taxonomic unit/OTU was: 810056/3756 (MP), 845242/4159 (OP), 881560/3970 (LP). At the phylum level, the three groups of Firmicutes and Bacteroides accounted for > 95%. The dominant flora at the LP was Bacteroides (53.85%), the dominant flora at the MP and OP was Firmicutes, 64.08 and 56.53%, respectively. At the genus level, the dominant genus at the LP was Prevotella, the dominant genera at the MP were Prevotella, Oncococcus, Streptococcus, and Kurtella. The dominant genera at OP were Prevotella and Nocococcus. At the phylum level, P levels were negatively correlated to Firmicutes, Actinomycetes Actinobacteria, and Fibrobacteres, but positively correlated to Bacteroidetes. Likewise, E2 was positively correlated to Proteobacteria but negatively correlated to Euryarchaeota. At the genus level, P hormone showed a significant correlation with 16 bacterial species, and E2 was significantly correlated to seven bacterial species. Function prediction analysis revealed a high similarity between the MP and OP with six differentially functional genes (DFGs) between them and 11 DFGs between OP and LP (P < 0.05). Fecal microbiota types of female rhesus monkeys varied with different stages of the menstrual cycle, possibly related to changes in hormone levels.

Neutrophil Transcriptional Deregulation by the Periodontal Pathogen Fusobacterium nucleatum in Gastric Cancer: A Bioinformatic Study

Background

Infection with the periodontal pathogen Fusobacterium nucleatum (F. nucleatum) has been associated with gastric cancer. The present study is aimed at uncovering the putative biological mechanisms underlying effects of F. nucleatum–mediated neutrophil transcriptional deregulation in gastric cancer.

Materials and Methods

A gene expression dataset pertaining to F. nucleatum-infected human neutrophils was utilized to identify differentially expressed genes (DEGs) using the GEO2R tool. Candidate genes associated with gastric cancer were sourced from the “Candidate Cancer Gene Database” (CCGD). Overlapping genes among these were identified as link genes. Functional profiling of the link genes was performed using “g:Profiler” tool to identify enriched Gene Ontology (GO) terms, pathways, miRNAs, transcription factors, and human phenotype ontology terms. Protein-protein interaction (PPI) network was constructed for the link genes using the “STRING” tool, hub nodes were identified as key candidate genes, and functionally enriched terms were determined.

Results

The gene expression dataset GEO20151 was downloaded, and 589 DEGs were identified through differential analysis. 886 candidate gastric cancer genes were identified in the CGGD database. Among these, 36 overlapping genes were identified as the link genes. Enriched GO terms included molecular function “enzyme building,” biological process “protein folding,'” cellular components related to membrane-bound organelles, transcription factors ER71 and Sp1, miRNAs miR580 and miR155, and several human phenotype ontology terms including squamous epithelium of esophagus. The PPI network contained 36 nodes and 53 edges, where the top nodes included PH4 and CANX, and functional terms related to intracellular membrane trafficking were enriched.

Conclusion

F nucleatum-induced neutrophil transcriptional activation may be implicated in gastric cancer via several candidate genes including DNAJB1, EHD1, IER2, CANX, and PH4B. Functional analysis revealed membrane-bound organelle dysfunction, intracellular trafficking, transcription factors ER71 and Sp1, and miRNAs miR580 and miR155 as other candidate mechanisms, which should be investigated in experimental studies.

The double-edged sword of probiotic supplementation on gut microbiota structure in Helicobacter pylori management

As Helicobacter pylori management has become more challenging and less efficient over the last decade, the interest in innovative interventions is growing by the day. Probiotic co-supplementation to antibiotic therapies is reported in several studies, presenting a moderate reduction in drug-related side effects and a promotion in positive treatment outcomes. However, the significance of gut microbiota involvement in the competence of probiotic co-supplementation is emphasized by a few researchers, indicating the alteration in the host gastrointestinal microbiota following probiotic and drug uptake. Due to the lack of long-term follow-up studies to determine the efficiency of probiotic intervention in H. pylori eradication, and the delicate interaction of the gut microbiota with the host wellness, this review aims to discuss the gut microbiota alteration by probiotic co-supplementation in H. pylori management to predict the comprehensive effectiveness of probiotic oral administration.Abbreviations: acyl-CoA- acyl-coenzyme A; AMP- antimicrobial peptide; AMPK- AMP-activated protein kinase; AP-1- activator protein 1; BA- bile acid; BAR- bile acid receptor; BCAA- branched-chain amino acid; C2- acetate; C3- propionate; C4- butyrate; C5- valeric acid; CagA- Cytotoxin-associated gene A; cAMP- cyclic adenosine monophosphate; CD- Crohn's disease; CDI- C. difficile infection; COX-2- cyclooxygenase-2; DC- dendritic cell; EMT- epithelial-mesenchymal transition; FMO- flavin monooxygenases; FXR- farnesoid X receptor; GPBAR1- G-protein-coupled bile acid receptor 1; GPR4- G protein-coupled receptor 4; H2O2- hydrogen peroxide; HCC- hepatocellular carcinoma; HSC- hepatic stellate cell; IBD- inflammatory bowel disease; IBS- irritable bowel syndrome; IFN-γ- interferon-gamma; IgA immunoglobulin A; IL- interleukin; iNOS- induced nitric oxide synthase; JAK1- janus kinase 1; JAM-A- junctional adhesion molecule A; LAB- lactic acid bacteria; LPS- lipopolysaccharide; MALT- mucosa-associated lymphoid tissue; MAMP- microbe-associated molecular pattern; MCP-1- monocyte chemoattractant protein-1; MDR- multiple drug resistance; mTOR- mammalian target of rapamycin; MUC- mucin; NAFLD- nonalcoholic fatty liver disease; NF-κB- nuclear factor kappa B; NK- natural killer; NLRP3- NLR family pyrin domain containing 3; NOC- N-nitroso compounds; NOD- nucleotide-binding oligomerization domain; PICRUSt- phylogenetic investigation of communities by reconstruction of unobserved states; PRR- pattern recognition receptor; RA- retinoic acid; RNS- reactive nitrogen species; ROS- reactive oxygen species; rRNA- ribosomal RNA; SCFA- short-chain fatty acids; SDR- single drug resistance; SIgA- secretory immunoglobulin A; STAT3- signal transducer and activator of transcription 3; T1D- type 1 diabetes; T2D- type 2 diabetes; Th17- T helper 17; TLR- toll-like receptor; TMAO- trimethylamine N-oxide; TML- trimethyllysine; TNF-α- tumor necrosis factor-alpha; Tr1- type 1 regulatory T cell; Treg- regulatory T cell; UC- ulcerative colitis; VacA- Vacuolating toxin A.

Interleukin-8 Regulates the Autophagy and Apoptosis in Gastric Cancer Cells via Regulating PI3K/Akt Signaling Pathway

Objective. To explore the role and mechanism of interleukin-8-mediated autophagy regulation of gastric cancer (GC) cells in GC. Methods. After cell culture, the SGC7901 cell line was separated into the control group and IL-8 (20 ng/mL) group, IL-8 (40 ng/mL) group, and IL-8 (60 ng/mL) group, to verify the effects of the PI3K/Akt signal path on the modulation of autophagy in GC cells. Western blot detected autophagy markers, ATG12-ATG5 complexes, autophagy-associated pathways, and apoptosis-associated factors in GC cells. Transwell was utilized to identify invasion capability. Results. Compared with the control group, the expression of LC3II, Atg5, ATG7, Beclin1, Bax, C-cas3, C-cas9, P-PI3K, P-Akt, and ATG12-ATG5 was remarkably elevated in the IL-8 (60 ng/mL) group, IL-8 (20 ng/mL) group, and the IL-8 (40 ng/mL) group. The expression of P62 and Bcl-2 in the IL-8 (60 ng/mL) group was also lower than that of the IL-8 (20 ng/mL) group and IL-8 (40 ng/mL) group, in contrast to the controls. The invasive quantity of GC SGC7901 cells in the IL-8 (60 ng/mL) group was also remarkably higher in contrast to the IL-8 (20 ng/mL) and IL-8 (40 ng/mL) groups. The relative expressions of LC3II, Atg5, ATG7, Beclin1, Bax, C-cas3, C-cas9, P-PI3K, P-Akt, and ATG12-ATG5 complex proteins in LY294002 group were considerably elevated. LC3II, Atg5, ATG7, Beclin1, Bax, C-cas3, C-cas9, P-PI3K, P-Akt, and ATG12-ATG5 were decreased in the IL-8 + LY294002 group. The relative expressions of P62 and Bcl-2 proteins in the IL-8 + LY294002 group were remarkably elevated, and the invasion of SGC7901 cells in the IL-8 group was elevated. In contrast to the IL-8 group, the invasion quantity of gastric cancer SGC7901 cells in the IL-8 + LY294002 group was considerably decreased. Conclusion. IL-8 promotes autophagy and aggression and suppresses apoptosis of GC SGC7901 cells by regulating PI3K/AKT pathway phosphorylation.

Microbiota and the Immune System-Actors in the Gastric Cancer Story

Simple Summary

Stomach cancer is one of the most commonly diagnosed cancers in the world. Although the number of new cases is decreasing year by year, the death rate for this type of cancer is still high. The heterogeneous course and the lack of symptoms in the early stages of the disease mean that the diagnosis is made late, which translates into a worse prognosis for such patients. That is why it is so important to analyze potential risk factors that may increase the risk of developing gastric cancer and to search for new effective methods of treatment. These requirements are met by the analysis of the composition of the gastric microbiota and its relationship with the immune system, which is a key element in the human anti-cancer fight. This publication was created to systematize the current knowledge on the impact of dysbiosis of human microbiota on the development and progression of gastric cancer. Particular emphasis was placed on taking into account the role of the immune system in this process.

Abstract

Gastric cancer remains one of the most commonly diagnosed cancers in the world, with a relatively high mortality rate. Due to the heterogeneous course of the disease, its diagnosis and treatment are limited and difficult, and it is associated with a reduced prognosis for patients. That is why it is so important to understand the mechanisms underlying the development and progression of this cancer, with particular emphasis on the role of risk factors. According to the literature data, risk factors include: changes in the composition of the stomach and intestinal microbiota (microbiological dysbiosis and the participation of Helicobacter pylori), improper diet, environmental and genetic factors, and disorders of the body’s immune homeostasis. Therefore, the aim of this review is to systematize the knowledge on the influence of human microbiota dysbiosis on the development and progression of gastric cancer, with particular emphasis on the role of the immune system in this process.

Unveiling microbiome profiles in human inner body fluids and tumor tissues with pancreatic or biliary tract cancer

With the discovery of bacterial symbiosis in the tissues of various cancers, the study of the tumor microbiome is attracting a great deal of attention. Anatomically, since the gastrointestinal tract, liver, and pancreas form a continuous ductal structure, the microbiomes in the digestive juices of these organs may influence each other. Here, we report a series of microbiome data in tumor-associated tissues such as tumor, non-tumor, and lymph nodes, and body fluids such as saliva, gastric juice, pancreatic juice, bile, and feces of patients with pancreatic or biliary tract cancers. The results show that the microbiome of tumor-associated tissues has a very similar bacterial composition, but that in body fluids has different bacterial composition which varies by location, where some bacteria localize to specific body fluids. Surprisingly, Akkermansia was only detected in the bile of patients with biliary tract cancer and its presence was significantly associated with the performance of external biliary drainage (P = 0.041). Furthermore, we found that tumor-associated tissues and body fluids in deep inner body are mostly inhabited by unidentified and uncharacterized bacteria, suggesting that such bacteria may be potential targets for precision therapy in the future.

Anti-Gastric Cancer Activity of the Cell-free Culture Supernatant of Serofluid Dish and Lactiplantibacillus plantarum YT013

Cancer is second only to heart disease as a cause of death, despite improvements in its early diagnosis and precision medicine. Due to the limitations of commonly used anticancer methods such as surgery, radiotherapy and chemotherapy, biological therapy, especially probiotics such as lactic acid bacteria, has received widespread attention. Lactobacillus has been proven to inhibit the proliferation of a variety of cancer cells. In this work, the effects of the cell-free culture supernatant of serofluid dish (CCS1) and the cell-free culture supernatant of Lactiplantibacillus plantarum YT013 (CCS2) isolated from serofluid dish on AGS, HCT116, HepG2 and PANC-1 cells were investigated. Based on the CCK-8 assay, CCS1 and CCS2 were shown to suppress the growth of cancer cells in a concentration-dependent manner. The IC₅₀ values of CCS2 of AGS, HCT116, HepG2 and PANC-1 cells were 346.51 ± 35.28, 1207.69 ± 333.18, 650.94 ± 123.78 and 808.96 ± 126.27 μg/ml, respectively. In addition, the results of fluorescence microscopy showed that CCS2 changed cell morphology and treated with CCS2 (200, 400 and 800 μg/ml) for 48 h, AGS cell apoptosis was quantitatively surveyed by flow cytometry, showing 25.0, 34.1, and 42.6% total apoptotic cells. Moreover, western blotting confirmed that BAX, BAD and Caspase-3/8/9 were significantly upregulated and that BCL-2 was significantly downregulated in AGS cells treated with CCS2. These results indicated that CCS2 might lead to apoptosis via the endogenous mitochondrial apoptotic pathway. In summary, Lactiplantibacillus plantarum YT013 may be considered a good candidate for anticancer therapies.

Peptic Ulcer and Gastric Cancer: Is It All in the Complex Host-Microbiome Interplay That Is Encoded in the Genomes of "Us" and "Them"?

It is increasingly being recognized that severe gastroduodenal diseases such as peptic ulcer and gastric cancer are not just the outcomes of Helicobacter pylori infection in the stomach. Rather, both diseases develop and progress due to the perfect storms created by a combination of multiple factors such as the expression of different H. pylori virulence proteins, consequent human immune responses, and dysbiosis in gastrointestinal microbiomes. In this mini review, we have discussed how the genomes of H. pylori and other gastrointestinal microbes as well as the genomes of different human populations encode complex and variable virulome–immunome interplay, which influences gastroduodenal health. The heterogeneities that are encrypted in the genomes of different human populations and in the genomes of their respective resident microbes partly explain the inconsistencies in clinical outcomes among the H. pylori-infected people.

Diagnostic and Therapeutic Uses of the Microbiome in the Field of Oncology

Cancer is a leading cause of death worldwide and it can affect almost every part of the human body. Effective screening and early diagnosis of cancers is extremely difficult due to the multifactorial etiology of the disease and delayed presentation of the patients. The available treatments are usually not specific to the affected organ system, leading to intolerable systemic side effects and early withdrawal from therapies. In vivo and in vitro studies have revealed an association of specific microbiome signatures with individual cancers. The cancer-related human microbiome has also been shown to affect the response of tissues to chemotherapy, immunotherapy, and radiation. This is an excellent opportunity for us to design specific screening markers using the microbiome to prevent cancers and diagnose them early. We can also develop precise treatments that can target cancer-affected specific organ systems and probably use a lesser dose of chemotherapy or radiation for the same effect. This prevents adverse effects and early cessation of treatments. However, we need further studies to exactly clarify and characterize these associations. In this review article, we focus on the association of the microbiome with individual cancers and highlight its future role in cancer screenings, diagnosis, prognosis, and treatments.

Fungal Microbiota Dysbiosis and Ecological Alterations in Gastric Cancer

Changes in bacteriome composition have a strong association with gastric cancer (GC). However, the relationship between stomach fungal microbiota composition and human host immune factors remains largely unknown. With high-throughput internal transcribed spacer region 2 (ITS2) sequencing, we characterized gastric fungal microbiome among the GC (n = 22), matched para-GC (n = 22), and healthy individuals (n = 11). A total of 4.5 million valid tags were generated and stratified into 1,631 operational taxonomic units (OTUs), and 10 phyla and 301 genera were identified. The presence of GC was associated with a distinct gastric fungal mycobiome signature, characterized by a decreased biodiversity and richness and significant differences in fungal composition. In addition, fungal dysbiosis was reflected by the increased ratio of Basidiomycota to Ascomycota and a higher proportion of opportunistic fungi, such as Cutaneotrichosporon and Malassezia, as well as the loss of Rhizopus and Rhodotorula during the progression of cancers. A panel of GC-associated fungi (e.g., Cutaneotrichosporon and Rhodotorula) was found to adequately exhibit diagnostic value. Furthermore, the mRNA levels of cytokines and chemokines were detected and correlated with the specific fungal dysbiosis, indicating the possible mechanism of GC. This study reveals GC-associated mycobiome dysbiosis characterized by altered fungal composition and ecology and suggests that the fungal mycobiome might play a role in the pathogenesis of GC.

Chemorefractory Gastric Cancer: The Evolving Terrain of Third-Line Therapy and Beyond

Simple Summary

Gastric and gastro-oesophageal junction cancers (GC) are the fourth cause of cancer-related deaths, representing an international problem which needs a proper assessment. Beyond being an aggressive disease, which rapidly progress to different lines of treatment, patients suffering GC normally present a non-depreciable number of symptoms that make them especially fragile. In this context, sequential treatment lines with few toxic adverse events have been associated to an increased survival. A satisfactory GC therapy comprise at least three lines of treatment including chemotherapy and immunotherapy and/or targeted agents when indicated.

Abstract

Gastric and gastro-oesophageal junction cancer (GC) represent a global healthcare problem being the fifth most common tumour type and the fourth cause of cancer mortality. Extremely poor median survival of approximately 10 months is normally reported within advanced GC patients, mainly secondary to two factors, i.e., the fragility of these patients and the aggressiveness of this disease. In this context, the correct treatment of GC patients requires not only a multidisciplinary team with special attention to palliative and nutritional care but also a close follow-up with regular monitoring of disease symptoms and tumour evaluation. Sequential treatment lines with few toxic adverse events have emerged as the best therapeutic approach, and a third line of therapy could further improve survival and quality of life of GC patients. Chemotherapy, immunotherapy, and targeted agents -when indicated- constitute the treatment armamentarium of these patients. In this review, we discuss treatment options in the refractory setting as well as novel approaches to overcome the poor prognosis of GC.

Esophageal microbiota composition and outcome of esophageal cancer treatment: a systematic review

BACKGROUND

The role of esophageal microbiota in esophageal cancer treatment is gaining renewed interest, largely driven by novel DNA-based microbiota analysis techniques. The aim of this systematic review is to provide an overview of current literature on the possible association between esophageal microbiota and outcome of esophageal cancer treatment, including tumor response to (neo)adjuvant chemo(radio)therapy, short-term surgery-related complications, and long-term oncological outcome.

METHODS

A systematic review of literature was performed, bibliographic databases were searched and relevant articles were selected by two independent researchers. The Newcastle-Ottawa scale was used to estimate the quality of included studies.

RESULTS

The search yielded 1303 articles, after selection and cross-referencing, five articles were included for qualitative synthesis and four studies were considered of good quality. Two articles addressed tumor response to neoadjuvant chemotherapy and described a correlation between high intratumoral Fusobacterium nucleatum levels and a poor response. One study assessed surgery-related complications, in which no direct association between esophageal microbiota and occurrence of complications was observed. Three studies described a correlation between shortened survival and high levels of intratumoral F. nucleatum, a low abundance of Proteobacteria and high abundances of Prevotella and Streptococcus species.

CONCLUSIONS

Current evidence points towards an association between esophageal microbiota and outcome of esophageal cancer treatment and justifies further research. Whether screening of the individual esophageal microbiota can be used to identify and select patients with a predisposition for adverse outcome needs to be further investigated. This could lead to the development of microbiota-based interventions to optimize esophageal microbiota composition, thereby improving outcome of patients with esophageal cancer.

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.

Helicobacter pylori-Induced Inflammation: Possible Factors Modulating the Risk of Gastric Cancer

Chronic inflammation and long-term tissue injury are related to many malignancies, including gastric cancer (GC). Helicobacter pylori (H. pylori), classified as a class I carcinogen, induces chronic superficial gastritis followed by gastric carcinogenesis. Despite a high prevalence of H. pylori infection, only about 1–3% of people infected with this bacterium develop GC worldwide. Furthermore, the development of chronic gastritis in some, but not all, H. pylori-infected subjects remains unexplained. These conflicting findings indicate that clinical outcomes of aggressive inflammation (atrophic gastritis) to gastric carcinogenesis are influenced by several other factors (in addition to H. pylori infection), such as gut microbiota, co-existence of intestinal helminths, dietary habits, and host genetic factors. This review has five goals: (1) to assess our current understanding of the process of H. pylori-triggered inflammation and gastric precursor lesions; (2) to present a hypothesis on risk modulation by the gut microbiota and infestation with intestinal helminths; (3) to identify the dietary behavior of the people at risk of GC; (4) to check the inflammation-related genetic polymorphisms and role of exosomes together with other factors as initiators of precancerous lesions and gastric carcinoma; and (5) finally, to conclude and suggest a new direction for future research.

Machine Learning as a Tool in Investigating the Possible Role of Microbiome in Development and Treatment of Cancer

In recent times, cancer has become a leading cause of death worldwide, and a need for new therapeutic methods to save lives has become an inevitable necessity. Microbiome and its composition have been a key area of interest among the scientific community. Microbiota appears to hold the key to the therapeutic outcome of cancer by modulating the anti-tumor activity of drugs. Furthermore, the genetic composition of the microbiota and its matching gene sequences in the oncogene has added a new dimension to cancer research. However, it requires adaptive learning techniques and high computational power to bring this research to light empirically. This paper explores the role of machine learning (ML), a subset of artificial intelligence (AI), as a tool to investigate the possible role of the microbiome in the detection and treatment of cancer.

Impact of Environmental and Pharmacologic Changes on the Upper Gastrointestinal Microbiome

Diseases of the upper gastrointestinal tract have become more prevalent over time. Mechanisms of disease formation are still only partially understood. Recent literature has shown that the surrounding microbiome affects the propensity for disease formation in various parts of the upper gastrointestinal tract. A review was performed of any literature to our best knowledge concerning the effects of pharmacologic agents, environmental changes, and surgical intervention on the microbiome of the upper gastrointestinal tract. Searches of the literature were performed using specific keywords related to drugs, surgical procedures, and environmental factors. Many prescription and nonprescription drugs that are commonly used have varying effects on the upper gastrointestinal tract. Proton pump inhibitors may affect the relative prevalence of some organisms in the lower esophagus and have less effect in the proximal esophagus. Changes in the esophageal microbiome correlate with some esophageal diseases. Drugs that induce weight loss have also been shown to affect the microbiomes of the esophagus and stomach. Common surgical procedures are associated with shifts in the microbial community in the gastrointestinal tract. Environmental factors have been shown to affect the microbiome in the upper gastrointestinal tract, as geographic differences correlate with alterations in the microbiome of the gastrointestinal tract. Understanding the association of environmental and pharmacologic changes on the microbiome of the upper gastrointestinal tract will facilitate treatment plans to reduce morbidity from disease.