Microbiome Markers of Pancreatic Cancer Based on Bacteria-Derived Extracellular Vesicles Acquired from Blood Samples: A Retrospective Propensity Score Matching Analysis

Applications of Urinary Extracellular Vesicles in the Diagnosis and Active Surveillance of Prostate Cancer

Prostate cancer is the most common non-cutaneous cancer among men in the UK, causing significant health and economic burdens. Diagnosis and risk prognostication can be challenging due to the genetic and clinical heterogeneity of prostate cancer as well as uncertainties in our knowledge of the underlying biology and natural history of disease development. Urinary extracellular vesicles (EVs) are microscopic, lipid bilayer defined particles released by cells that carry a variety of molecular cargoes including nucleic acids, proteins and other molecules. Urine is a plentiful source of prostate-derived EVs. In this narrative review, we summarise the evidence on the function of urinary EVs and their applications in the evolving field of prostate cancer diagnostics and active surveillance. EVs are implicated in the development of all hallmarks of prostate cancer, and this knowledge has been applied to the development of multiple diagnostic tests, which are largely based on RNA and miRNA. Common gene probes included in multi-probe tests include PCA3 and ERG, and the miRNAs miR-21 and miR-141. The next decade will likely bring further improvements in the diagnostic accuracy of biomarkers as well as insights into molecular biological mechanisms of action that can be translated into opportunities in precision uro-oncology.

Urinary microbiome-based metagenomic signature for the noninvasive diagnosis of hepatocellular carcinoma

BACKGROUND

Gut microbial dysbiosis is implicated in chronic liver disease and hepatocellular carcinoma (HCC), but the role of microbiomes from various body sites remains unexplored. We assessed disease-specific alterations in the urinary microbiome in HCC patients, investigating their potential as diagnostic biomarkers.

METHODS

We performed cross-sectional analyses of urine samples from 471 HCC patients and 397 healthy controls and validated the results in an independent cohort of 164 HCC patients and 164 healthy controls. Urinary microbiomes were analyzed by 16S rRNA gene sequencing. A microbial marker-based model distinguishing HCC from controls was built based on logistic regression, and its performance was tested.

RESULTS

Microbial diversity was significantly reduced in the HCC patients compared with the controls. There were significant differences in the abundances of various bacteria correlated with HCC, thus defining a urinary microbiome-derived signature of HCC. We developed nine HCC-associated genera-based models with robust diagnostic accuracy (area under the curve [AUC], 0.89; balanced accuracy, 81.2%). In the validation, this model detected HCC with an AUC of 0.94 and an accuracy of 88.4%.

CONCLUSIONS

The urinary microbiome might be a potential biomarker for the detection of HCC. Further clinical testing and validation of these results are needed in prospective studies.

Paraprobiotic derived from Bacillus velezensis GV1 improves immune response and gut microbiota composition in cyclophosphamide-treated immunosuppressed mice

Paraprobiotics that benefit human health have the capacity to modulate innate and adaptive immune systems. In this study, we prepared the paraprobiotic from Bacillus velezensis GV1 using the heat-killing method and investigated its effects on immunity and gut microbiota in vitro and in vivo. The morphology of inactivated strain GV1 was observed using scanning electron microscopy. Treatment with GV1 promoted nitric oxide production and augmented cytokine (IL-6, IL-1β, and TNF-α) expression and secretion in RAW 264.7 macrophages. Moreover, the strain GV1 could alleviate cyclophosphamide monohydrate (CTX)-induced immunosuppression by reversing spleen damage and restoring the immune organ index, as well as by increasing the expression of immune-related cytokines (TNF-α, IL-1β, IFN-γ, and IL-2) in the spleen and thymus, respectively. Furthermore, GV1 treatment dramatically healed the CTX-damaged colon and regulated gut microbiota by increasing the relative abundance of beneficial bacterial families (Lactobacillaceae, Akkermansiaceae, and Coriobacteriaceae) and decreasing that of harmful bacterial families (Desulfovibrionaceae, Erysipelotrichaceae, and Staphylococcaceae). Thus, the heat-killed GV1 can be considered a potential immunoregulatory agent for use as a functional food or immune-enhancing medicine.

Bibliometric analysis of pancreatic diseases and gut microbiota research from 2002 to 2022

Background

An increasing number of studies have indicated that pancreatic diseases are associated with the structure of the gut microbiota. We aimed to assess the research hotspots and trends in this field through a quantitative method.

Materials and methods

Articles related to pancreatic diseases and the gut microbiota published from 2002 to 2022 were retrieved from the Web of Science database. We visualized the countries/regions, institutions, authors, journals, and keywords using VOSviewer and CiteSpace software. The interplay between pancreatic diseases and the gut microbiota was also analysed.

Results

A total of 129 publications were finally identified. The number of papers increased gradually, and China held the dominant position with respect to publication output. Shanghai Jiao Tong University was the most influential institution. Zeng Yue ranked highest in the number of papers, and Scientific Reports was the most productive journal. The keywords "gut", "bacterial translocation", and "acute pancreatitis" appeared early for the first time, and "gut microbiota", "community", and "diversity" have been increasingly focused on. The predominant pancreatic disease correlated with the gut microbiota was pancreatic inflammatory disease (50.39%). Pancreatic diseases are associated with alterations in the gut microbiota, characterized by a decrease in beneficial bacteria and an increase in harmful bacteria.

Conclusion

This is the first comprehensive bibliometric analysis of all pancreatic diseases and the gut microbiota. The research on the relationship between them is still in the preliminary stage, and the trend is toward a gradual deepening of the research and precise treatment development. The interaction between the gut microbiota and pancreatic diseases will be of increasing concern in the future.

Microbiome as a biomarker and therapeutic target in pancreatic cancer

Studying the effects of the microbiome on the development of different types of cancer has recently received increasing research attention. In this context, the microbial content of organs of the gastrointestinal tract has been proposed to play a potential role in the development of pancreatic cancer (PC). Proposed mechanisms for the pathogenesis of PC include persistent inflammation caused by microbiota leading to an impairment of antitumor immune surveillance and altered cellular processes in the tumor microenvironment. The limited available diagnostic markers that can currently be used for screening suggest the importance of microbial composition as a non-invasive biomarker that can be used in clinical settings. Samples including saliva, stool, and blood can be analyzed by 16 s rRNA sequencing to determine the relative abundance of specific bacteria. Studies have shown the potentially beneficial effects of prebiotics, probiotics, antibiotics, fecal microbial transplantation, and bacteriophage therapy in altering microbial diversity, and subsequently improving treatment outcomes. In this review, we summarize the potential impact of the microbiome in the pathogenesis of PC, and the role these microorganisms might play as biomarkers in the diagnosis and determining the prognosis of patients. We also discuss novel treatment methods being used to minimize or prevent the progression of dysbiosis by modulating the microbial composition. Emerging evidence is supportive of applying these findings to improve current therapeutic strategies employed in the treatment of PC.

Leveraging circulating microbiome signatures to predict tumor immune microenvironment and prognosis of patients with non-small cell lung cancer

BACKGROUND

Accumulating evidence supports the significant role of human microbiome in development and therapeutic response of tumors. Circulating microbial DNA is non-invasive and could show a general view of the microbiome of host, making it a promising biomarker for cancers. However, whether circulating microbiome is associated with prognosis of non-small cell lung cancer (NSCLC) and its potential mechanisms on tumor immune microenvironment still remains unknown.

METHODS

The blood microbiome data and matching tumor RNA-seq data of TCGA NSCLC patients were obtained from Poore's study and UCSC Xena. Univariate and multivariate Cox regression analysis were used to identify circulating microbiome signatures associated with overall survival (OS) and construct the circulating microbial abundance prognostic scoring (MAPS) model. Nomograms integrating clinical characteristics and circulating MAPS scores were established to predict OS rate of NSCLC patients. Joint analysis of blood microbiome data and matching tumor RNA-seq data was used to deciphered the tumor microenvironment landscape of patients in circulating MAPS-high and MAPS-low groups. Finally, the predictive value of circulating MAPS on the efficacy of immunotherapy and chemotherapy were assessed.

RESULTS

A circulating MAPS prediction model consisting of 14 circulating microbes was constructed and had an independent prognostic value for NSCLC. The integration of circulating MAPS into nomograms may improve the prognosis predictive power. Joint analysis revealed potential interactions between prognostic circulating microbiome and tumor immune microenvironment. Especially, intratumor plasma cells and humoral immune response were enriched in circulating MAPS-low group, while intratumor CD4 + Th2 cells and proliferative related pathways were enriched in MAPS-high group. Finally, drug sensitivity analysis indicated the potential of circulating MAPS as a predictor of chemotherapy efficacy.

CONCLUSION

A circulating MAPS prediction model was constructed successfully and showed great prognostic value for NSCLC. Our study provides new insights of interactions between microbes, tumors and immunity, and may further contribute to precision medicine for NSCLC.

Multi-omics reveals Dengzhan Shengmai formulation ameliorates cognitive impairments in D-galactose-induced aging mouse model by regulating CXCL12/CXCR4 and gut microbiota

Dengzhan Shengmai (DZSM), a traditional Chinese medicine formulation, has been administered extensively to elderly individuals with cognitive impairment (CI). However, the underlying mechanisms by which Dengzhan Shengmai improves cognitive impairment remains unknown. This study aimed to elucidate the underlying mechanism of the effect of Dengzhan Shengmai on aging-associated cognitive impairment via a comprehensive combination of transcriptomics and microbiota assessment. Dengzhan Shengmai was orally administered to a D-galactose-induced aging mouse model, and evaluation with an open field task (OFT), Morris water maze (MWM), and histopathological staining was performed. Transcriptomics and 16S rDNA sequencing were applied to elucidate the mechanism of Dengzhan Shengmai in alleviating cognitive deficits, and enzyme-linked immunosorbent assay (ELISA), quantitative real-time polymerase chain reaction (PCR), and immunofluorescence were employed to verify the results. The results first confirmed the therapeutic effects of Dengzhan Shengmai against cognitive defects; specifically, Dengzhan Shengmai improved learning and impairment, suppressed neuro loss, and increased Nissl body morphology repair. Comprehensive integrated transcriptomics and microbiota analysis indicated that chemokine CXC motif receptor 4 (CXCR4) and its ligand CXC chemokine ligand 12 (CXCL12) were targets for improving cognitive impairments with Dengzhan Shengmai and also indirectly suppressed the intestinal flora composition. Furthermore, in vivo results confirmed that Dengzhan Shengmai suppressed the expression of CXC motif receptor 4, CXC chemokine ligand 12, and inflammatory cytokines. This suggested that Dengzhan Shengmai inhibited CXC chemokine ligand 12/CXC motif receptor 4 expression and modulated intestinal microbiome composition by influencing inflammatory factors. Thus, Dengzhan Shengmai improves aging-related cognitive impairment effects via decreased CXC chemokine ligand 12/CXC motif receptor 4 and inflammatory factor modulation to improve gut microbiota composition.

The Microbiome in PDAC-Vantage Point for Future Therapies?

Microorganisms have been increasingly implicated in the pathogenesis of malignant diseases, potentially affecting different hallmarks of cancer. Despite the fact that we have recently gained tremendous insight into the existence and interaction of the microbiome with neoplastic cells, we are only beginning to understand and exploit this knowledge for the treatment of human malignancies. Pancreatic ductal adenocarcinoma (PDAC) is an aggressive solid tumor with limited therapeutic options and a poor long-term survival. Recent data have revealed fascinating insights into the role of the tumoral microbiome in PDAC, with profound implications for survival and potentially therapeutic outcomes. In this review, we outline the current scientific knowledge about the clinical and translational role of the microbiome in PDAC. We describe the microbial compositions in healthy and tumoral pancreatic tissue and point out four major aspects of the microbiome in PDAC: pathogenesis, diagnosis, treatment, and prognosis. However, caution must be drawn to inherent pitfalls in analyzing the intratumoral microbiome. Among others, contamination with environmental microbes is one of the major challenges. To this end, we discuss different decontamination approaches that are crucial for clinicians and scientists alike to foster applicability and physiological relevance in this translational field. Without a definition of an exact and reproducible intratumoral microbial composition, the exploitation of the microbiome as a diagnostic or therapeutic tool remains theoretical.

Role of drug catabolism, modulation of oncogenic signaling and tumor microenvironment in microbe-mediated pancreatic cancer chemoresistance

Pancreatic ductal adenocarcinoma (PDAC) has one of the highest incidence/death ratios among all neoplasms due to its late diagnosis and dominant chemoresistance. Most PDAC patients present with an advanced disease characterized by a multifactorial, inherent and acquired resistance to current anticancer treatments. This remarkable chemoresistance has been ascribed to several PDAC features including the genetic landscape, metabolic alterations, and a heterogeneous tumor microenvironment that is characterized by dense fibrosis, and a cellular contexture including functionally distinct subclasses of cancer-associated fibroblasts, immune suppressive cells, but also a number of bacteria, shaping a specific tumor microbiome microenvironment. Thus, recent studies prompted the emergence of a new research avenue, by describing the role of the microbiome in gemcitabine resistance, while next-generation-sequencing analyses identified a specific microbiome in different tumors, including PDAC. Functionally, the contribution of these microbes to PDAC chemoresistance is only beginning to be explored. Here we provide an overview of the studies demonstrating that bacteria have the capacity to metabolically transform and hence inactivate anticancer drugs, as exemplified by the inhibition of the efficacy of 10 out of 30 chemotherapeutics by Escherichia coli. Moreover, a number of bacteria modulate specific oncogenic pathways, such as Fusobacterium nucleatum, affecting autophagy and apoptosis induction by 5-fluorouracil and oxaliplatin. We hypothesize that improved understanding of how chemoresistance is driven by bacteria could enhance the efficacy of current treatments, and discuss the potential of microbiome modulation and targeted therapeutic approaches as well as the need for more reliable models and biomarkers to translate the findings of preclinical/translational research to the clinical setting, and ultimately overcome PDAC chemoresistance, hence improving clinical outcome.

Impact of microbiota-immunity axis in pancreatic cancer management

The microbiota impact on human diseases is well-known, and a growing body of literature is providing evidence about the complex interplay between microbiota-immune system-human physiology/pathology, including cancers. Together with the defined risk factors (e.g., smoke habits, diet, diabetes, and obesity), the oral, gut, biliary, and intrapancreatic microbiota contribute to pancreatic cancer development through different pathways including the interaction with the immune system. Unfortunately, a great majority of the pancreatic cancer patients received a diagnosis in advanced stages not amenable to be radically treated and potentially cured. Given the poor pancreatic cancer prognosis, complete knowledge of these complicated relationships could help researchers better understand the disease pathogenesis and thus provide early potential non-invasive biomarkers, new therapeutic targets, and tools for risk stratification that might result in greater therapeutic possibilities and eventually in a better and longer patient survival.

Prostate Infiltration by Treg and Th17 Cells as an Immune Response to Propionibacterium acnes Infection in the Course of Benign Prostatic Hyperplasia and Prostate Cancer

Benign prostatic hyperplasia (BPH) and prostate cancer (PCa) belong to the most frequent diseases in ageing men. It has been proposed that prostate chronic inflammation is a risk factor for the development of both BPH and PCa. However, potential stimuli that cause or maintain inflammation in the prostate gland are still poorly characterized. Bacterial infections seems to be one of the potential sources of prostatitis. Recent studies show that Propionibacterium acnes (P. acnes) is the most prevalent microorganism in the prostate gland and may be a predisposing factor for inflammation of prostatic tissue. It indicates that P. acnes may contribute to cancer development by enhancing proinflammatory responses, as well as by modifying the prostate extracellular environment. In this review, we discuss the potential role of P. acnes in the development of BPH and PCa and highlight the importance of regulatory T CD4(+)FoxP3(+) (Treg) and Th17 cells in response to P. acnes infection in the context of both prostate diseases.

Predicting preterm birth through vaginal microbiota, cervical length, and WBC using a machine learning model

An association between the vaginal microbiome and preterm birth has been reported. However, in practice, it is difficult to predict premature birth using the microbiome because the vaginal microbial community varies highly among samples depending on the individual, and the prediction rate is very low. The purpose of this study was to select markers that improve predictive power through machine learning among various vaginal microbiota and develop a prediction algorithm with better predictive power that combines clinical information. As a multicenter case–control study with 150 Korean pregnant women with 54 preterm delivery group and 96 full-term delivery group, cervicovaginal fluid was collected from pregnant women during mid-pregnancy. Their demographic profiles (age, BMI, education level, and PTB history), white blood cell count, and cervical length were recorded, and the microbiome profiles of the cervicovaginal fluid were analyzed. The subjects were randomly divided into a training (n = 101) and a test set (n = 49) in a two-to-one ratio. When training ML models using selected markers, five-fold cross-validation was performed on the training set. A univariate analysis was performed to select markers using seven statistical tests, including the Wilcoxon rank-sum test. Using the selected markers, including Lactobacillus spp., Gardnerella vaginalis, Ureaplasma parvum, Atopobium vaginae, Prevotella timonensis, and Peptoniphilus grossensis, machine learning models (logistic regression, random forest, extreme gradient boosting, support vector machine, and GUIDE) were used to build prediction models. The test area under the curve of the logistic regression model was 0.72 when it was trained with the 17 selected markers. When analyzed by combining white blood cell count and cervical length with the seven vaginal microbiome markers, the random forest model showed the highest test area under the curve of 0.84. The GUIDE, the single tree model, provided a more reasonable biological interpretation, using the 10 selected markers (A. vaginae, G. vaginalis, Lactobacillus crispatus, Lactobacillus fornicalis, Lactobacillus gasseri, Lactobacillus iners, Lactobacillus jensenii, Peptoniphilus grossensis, P. timonensis, and U. parvum), and the covariates produced a tree with a test area under the curve of 0.77. It was confirmed that the association with preterm birth increased when P. timonensis and U. parvum increased (AUC = 0.77), which could also be explained by the fact that as the number of Peptoniphilus lacrimalis increased, the association with preterm birth was high (AUC = 0.77). Our study demonstrates that several candidate bacteria could be used as potential predictors for preterm birth, and that the predictive rate can be increased through a machine learning model employing a combination of cervical length and white blood cell count information.

Comprehensive fecal metabolomics and gut microbiota for the evaluation of the mechanism of Panax Ginseng in the treatment of Qi-deficiency liver cancer

ETHNOPHARMACOLOGICAL RELEVANCE

Qi deficiency liver cancer (QDLC) is an important part of liver cancer research in traditional Chinese medicine (TCM). In the course of its treatment, Panax ginseng is often selected as the main Chinese herbal medicine, and its function has special significance in the tumor treatment of Qi deficiency constitution. However, its mechanism is not clear.

AIM OF THE STUDY

The research tried to evaluate the mechanism of Panax ginseng in the treatment of QDLC through fecal metabonomics and gut microbiota on the basis of previous pharmacodynamic evaluation.

MATERIALS AND METHODS

Firstly, biomarkers and related metabolic pathways were screened and identified by metabonomics and Kyoto Encyclopedia of Genes and Genomes (KEGG) database. Then, 16S rRNA sequencing technique was used to investigate the composition, β diversity and key differences of gut microbiota. Finally, the relationship among phenotypes, gut microbiota and fecal metabolites was comprehensively analyzed by spearman correlation coefficient.

RESULTS

31 pharmacodynamic potential biomarkers and 20 synergistic potential biomarkers of effective parts of Panax ginseng on QDLC were screened and identified by fecal metabonomics. And then, 6 major metabolic pathways were searched, including bile acid biosynthesis, unsaturated fatty acid biosynthesis, tryptophan metabolism, arachidonic acid metabolism, pyrimidine metabolism, vitamin B6 metabolism. In the study of gut microbiota, at the genus level, 25 species of bacteria with significant differences of effective parts on QDLC and 23 species of bacteria with significant differences of synergistic action of ginsenosides and polysaccharides were screened. In addition, Spearman correlation analysis showed that there was a complex potential relationship among phenotype, gut microbiota and fecal metabolites during the development of QDLC and Panax ginseng intervention, which was mainly reflected in the close potential relationship between bacteria and fecal metabolites such as bile acids, unsaturated fatty acids and indole compounds.

CONCLUSION

Through the changes of fecal endogenous metabolites and intestinal bacteria, the mechanism of Panax ginseng on QDLC were preliminarily clarified.

Extracellular vesicle-mediated crosstalk between pancreatic cancer and stromal cells in the tumor microenvironment

Pancreatic ductal adenocarcinoma (PDAC) interacts closely with the tumor microenvironment (TME). The TME is remodeled by crosstalk between pancreatic cancer cells and stromal cells, and is critical for cancer progression. Extracellular vesicles (EVs), including exosomes and microvesicles, help facilitate an exchange of information both within the TME and to distant organs. EVs have also been identified as potential diagnostic biomarkers, therapeutic targets, and drug carriers for pancreatic cancer treatment. Thus, understanding the selective packaging of EVs cargo and its mechanistic impact will increase our understanding of cancer biology. In this review, we collect and analyze recent findings of the pancreatic cancer-stromal cell interactions mediated by EVs and the mechanisms involved in cancer-related immunity and chemoresistance. These studies demonstrate the vital role of EVs in pancreatic cancer reprogramming and TME remodeling. We also summarize the EVs identified as potential PDAC diagnostic biomarkers and possible therapeutic targets. This greater understanding is a promising avenue for transitioning EVs from bench to bedside.

Metagenomic Analysis of Plasma Microbial Extracellular Vesicles in Patients Receiving Mechanical Ventilation: A Pilot Study

Background: Previous studies reported a significant association between pneumonia outcome and the respiratory microbiome. There is increasing interest in the roles of bacterial extracellular vesicles (EVs) in various diseases. We studied the composition and function of microbiota-derived EVs in the plasma of patients receiving mechanical ventilation to evaluate whether they can be used as a diagnostic marker and to predict clinical outcomes. Methods: Plasma samples (n = 111) from 59 mechanically ventilated patients (41 in the pneumonia group; 24 in the nursing home and hospital-associated infection [NHAI] group) were prospectively collected on days one and seven. After isolating the bacterial EVs from plasma samples, nucleic acid was extracted for 16S rRNA gene pyrosequencing. The samples were evaluated to determine the α and β diversity, bacterial composition, and predicted functions. Results: Principal coordinates analysis revealed significantly different clustering of microbial EVs between the pneumonia and non-pneumonia groups. The proportions of Lactobacillus, Cutibacterium, and Sphingomonas were significantly different between the pneumonia and non-pneumonia groups. In addition, the abundances of Lactobacillus and Bifidobacterium were significantly higher in the non-NHAI than the NHAI group. In the analysis of β diversity, the structure of microbial EVs differed significantly different between 28-day survivors and non-survivors (Bray-Curtis distance, p = 0.014). Functional profiling revealed significant differences between the pneumonia and non-pneumonia groups. The longitudinal change in predicted functions of microbial EV genes showed a significant difference between 28-day survivors and non-survivors. Conclusions: Bacterial microbiota–derived EVs in the plasma have potential as diagnostic and prognostic markers for patients receiving mechanical ventilation. Further large prospective studies are needed to determine the clinical utility of plasma microbiota-EVs in intubated patients.

A new horizon of precision medicine: combination of the microbiome and extracellular vesicles

Over several decades, the disease pattern of intractable disease has changed from acute infection to chronic disease accompanied by immune and metabolic dysfunction. In addition, scientific evidence has shown that humans are holobionts; of the DNA in humans, 1% is derived from the human genome, and 99% is derived from microbial genomes (the microbiome). Extracellular vesicles (EVs) are lipid bilayer-delimited nanoparticles and key messengers in cell-to-cell communication. Many publications indicate that microbial EVs are both positively and negatively involved in the pathogenesis of various intractable diseases, including inflammatory diseases, metabolic disorders, and cancers. Microbial EVs in feces, blood, and urine show significant differences in their profiles between patients with a particular disease and healthy subjects, demonstrating the potential of microbial EVs as biomarkers for disease diagnosis, especially for assessing disease risk. Furthermore, microbial EV therapy offers a variety of advantages over live biotherapeutics and human cell EV (or exosome) therapy for the treatment of intractable diseases. In summary, microbial EVs are a new tool in medicine, and microbial EV technology might provide us with innovative diagnostic and therapeutic solutions in precision medicine.

The tiny membrane-bound vesicles containing various biomolecules that the organisms comprising our microbiome release could offer a powerful tool for precision medicine. Our bodies are home to trillions of microbes, which interact closely with our tissues to maintain a healthy physiological environment. Yoon-Keun Kim of the Institute of MD Healthcare, Seoul, South Korea, and colleagues have reviewed current research into the extracellular vesicles that these microbes use to communicate with other microbes and their human hosts. The authors note that these vesicles affect tissues throughout the body, and their activities have been linked to various disorders including asthma, Crohn’s disease and cancer. A deeper understanding of how these vesicles prevent or accelerate various conditions in different individuals could yield useful new diagnostic biomarkers and provide the foundation for interventions that are optimized for each patient.

A Comprehensive Review of the Current and Future Role of the Microbiome in Pancreatic Ductal Adenocarcinoma

Simple Summary

This review summarizes the current literature related to the microbiome and pancreatic ductal adenocarcinoma (PDAC). The aim of this review is to explore the current role of the microbiome in the disease process, screening/diagnostics and to postulate the future role with regards to therapeutic strategies including chemotherapy, immunotherapy and surgery. We further explore the future of microbiome modulation (faecal microbiome transplants, bacterial consortiums, anti-microbials and probiotics), their applications and how we can improve the future of microbiome modulation in a bid to improve PDAC outcomes.

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is expected to become the second most common cause of cancer death in the USA by 2030, yet progress continues to lag behind that of other cancers, with only 9% of patients surviving beyond 5 years. Long-term survivorship of PDAC and improving survival has, until recently, escaped our understanding. One recent frontier in the cancer field is the microbiome. The microbiome collectively refers to the extensive community of bacteria and fungi that colonise us. It is estimated that there is one to ten prokaryotic cells for each human somatic cell, yet, the significance of this community in health and disease has, until recently, been overlooked. This review examines the role of the microbiome in PDAC and how it may alter survival outcomes. We evaluate the possibility of employing microbiomic signatures as biomarkers of PDAC. Ultimately this review analyses whether the microbiome may be amenable to targeting and consequently altering the natural history of PDAC.

Anti-Cancer Role and Therapeutic Potential of Extracellular Vesicles

Cell-cell communication is an important mechanism in biological processes. Extracellular vesicles (EVs), also referred to as exosomes, microvesicles, and prostasomes, are microvesicles secreted by a variety of cells. EVs are nanometer-scale vesicles composed of a lipid bilayer and contain biological functional molecules, such as microRNAs (miRNAs), mRNAs, and proteins. In this review, "EVs" is used as a comprehensive term for vesicles that are secreted from cells. EV research has been developing over the last four decades. Many studies have suggested that EVs play a crucial role in cell-cell communication. Importantly, EVs contribute to cancer malignancy mechanisms such as carcinogenesis, proliferation, angiogenesis, metastasis, and escape from the immune system. EVs derived from cancer cells and their microenvironments are diverse, change in nature depending on the condition. As EVs are thought to be secreted into body fluids, they have the potential to serve as diagnostic markers for liquid biopsy. In addition, cells can encapsulate functional molecules in EVs. Hence, the characteristics of EVs make them suitable for use in drug delivery systems and novel cancer treatments. In this review, the potential of EVs as anti-cancer therapeutics is discussed.

Microbiome-Friend or Foe of Pancreatic Cancer?

Pancreatic ductal adenocarcinoma is one of the deadliest human neoplasms. Despite the development of new surgical and adjuvant therapies, the prognosis remains very poor, with the overall survival rate not exceeding 9%. There is now increasing evidence that the human microbiome, which is involved in many physiological functions, including the regulation of metabolic processes and the modulation of the immune system, is possibly linked to pancreatic oncogenesis. However, the exact mechanisms of action are poorly understood. Our review summarizes the current understanding of how the microbiome affects pancreatic cancer development and progression. We discuss potential pathways of microbe translocation to the pancreas, as well as the mechanism of their action. We describe the role of the microbiome as a potential marker of pancreatic cancer diagnosis, progression, and survival. Finally, we discuss the possibilities of modifying the microbiome to improve treatment effectiveness for this deadly disease.

Bacterial Extracellular Vesicles in Gastrointestinal Tract Cancer: An Unexplored Territory

Bacterial extracellular vesicles are membrane-enclosed, lipid bi-layer nanostructures that carry different classes of biomolecules, such as nucleic acids, lipids, proteins, and diverse types of small molecular metabolites, as their cargo. Almost all of the bacteria in the gut secrete extracellular vesicles to assist them in competition, survival, material exchange, host immune modulation, infection, and invasion. The role of gut microbiota in the development, progression, and pathogenesis of gastrointestinal tract (GIT) cancer has been well documented. However, the possible involvement of bacterial extracellular vesicles (bEVs) in GIT cancer pathophysiology has not been given due attention. Studies have illustrated the ability of bEVs to cross physiological barriers, selectively accumulate near tumor cells, and possibly alter the tumor microenvironment (TME). A systematic search of original published works related to bacterial extracellular vesicles on gastrointestinal cancer was performed for this review. The current systemic review outlines the possible impact of gut microbiota derived bEVs in GIT cancer in light of present-day understanding. The necessity of using advanced sequencing technologies, such as genetic, proteomic, and metabolomic investigation methodologies, to facilitate an understanding of the interrelationship between cancer-associated bacterial vesicles and gastrointestinal cancer is also emphasized. We further discuss the clinical and pharmaceutical potential of bEVs, along with future efforts needed to understand the mechanism of interaction of bEVs in GIT cancer pathogenesis.

Increase in Akkermansiaceae in Gut Microbiota of Prostate Cancer-Bearing Mice

Gut microbiota are reported to be associated with many diseases, including cancers. Several bacterial taxa have been shown to be associated with cancer development or response to treatment. However, longitudinal microbiota alterations during the development of cancers are relatively unexplored. To better understand how microbiota changes, we profiled the gut microbiota composition from prostate cancer-bearing mice and control mice at five different time points. Distinct gut microbiota differences were found between cancer-bearing mice and control mice. Akkermansiaceae was found to be significantly higher in the first three weeks in cancer-bearing mice, which implies its role in the early stage of cancer colonization. We also found that Bifidobacteriaceae and Enterococcaceae were more abundant in the second and last sampling week, respectively. The increments of Akkermansiaceae, Bifidobacteriaceae and Enterococcaceae were previously found to be associated with responses to immunotherapy, which suggests links between these bacteria families and cancers. Additionally, our function analysis showed that the bacterial taxa carrying steroid biosynthesis and butirosin and neomycin biosynthesis were increased, whereas those carrying naphthalene degradation decreased in cancer-bearing mice. Our work identified the bacteria taxa altered during prostate cancer progression and provided a resource of longitudinal microbiota profiles during cancer development in a mouse model.