Enrichment of oral microbiota in early cystic precursors to invasive pancreatic cancer

Intratumour microbiome of pancreatic cancer

Pancreatic cancer is a high mortality malignancy with almost equal mortality and morbidity rates. Both normal and tumour tissues of the pancreas were previously considered sterile. In recent years, with the development of technologies for high-throughput sequencing, a variety of studies have revealed that pancreatic cancer tissues contain small amounts of bacteria and fungi. The intratumour microbiome is being revealed as an influential contributor to carcinogenesis. The intratumour microbiome has been identified as a crucial factor for pancreatic cancer progression, diagnosis, and treatment, chemotherapy resistance, and immune response. A better understanding of the biology of the intratumour microbiome of pancreatic cancer contributes to the establishment of better early cancer screening and treatment strategies. This review focuses on the possible origins of the intratumour microbiome in pancreatic cancer, the intratumour localization, the interaction with the tumour microenvironment, and strategies for improving the outcome of pancreatic cancer treatment. Thus, this review offers new perspectives for improving the prognosis of pancreatic cancer.

The interplay between oral microbiota, gut microbiota and systematic diseases

Over the past two decades, the importance of microbiota in health and disease has become evident. The human gut microbiota and oral microbiota are the largest and second-largest microbiome in the human body, respectively, and they are physically connected as the oral cavity is the beginning of the digestive system. Emerging and exciting evidence has shown complex and important connections between gut microbiota and oral microbiota. The interplay of the two microbiomes may contribute to the pathological processes of many diseases, including diabetes, rheumatoid arthritis, nonalcoholic fatty liver disease, inflammatory bowel disease, pancreatic cancer, colorectal cancer, and so on. In this review, we discuss possible routes and factors of oral microbiota to affect gut microbiota, and the contribution of this interplay between oral and gut microbiota to systemic diseases. Although most studies are association studies, recently, there have been increasing mechanistic investigations. This review aims to enhance the interest in the connection between oral and gut microbiota, and shows the tangible impact of this connection on human health.

Impact of neoadjuvant therapy on gut microbiome in patients with resectable/borderline resectable pancreatic ductal adenocarcinoma

BACKGROUND

/Objectives: Effects of chemotherapy on gut microbiota have been reported in various carcinomas. The current study aimed to evaluate the changes in the gut microbiota before and after neoadjuvant chemotherapy (NAC) in patients with resectable (R) and borderline resectable (BR) pancreatic ductal adenocarcinoma (PDAC) and understand their clinical implications.

METHODS

Twenty patients diagnosed with R/BR-PDAC were included in this study. Stool samples were collected at two points, before and after NAC, for microbiota analysis using 16S ribosomal RNA (16S rRNA) gene sequences.

RESULTS

Of the 20 patients, 18 (90%) were treated with gemcitabine plus S-1 as NAC, and the remaining patients received gemcitabine plus nab-paclitaxel and a fluorouracil, leucovorin, irinotecan, and oxaliplatin combination. No significant differences were observed in the α- and β-diversity before and after NAC. Bacterial diversity was not associated with Evans classification (histological grade of tumor destruction by NAC) or postoperative complications. The relative abundance of Actinobacteria phylum after NAC was significantly lower than that before NAC (P = 0.02). At the genus level, the relative abundance of Bifidobacterium before NAC in patients with Evans grade 2 disease was significantly higher than that in patients with Evans grade 1 disease (P = 0.03). Patients with Evans grade 2 lost significantly more Bifidobacterium than patients with Evans grade 1 (P = 0.01).

CONCLUSIONS

The diversity of gut microbiota was neither decreased by NAC for R/BR-PDAC nor associated with postoperative complications. Lower incidence of Bifidobacterium genus before NAC may be associated with a lower pathological response to NAC.

Gastrointestinal disorders and intestinal bacteria: Advances in research and applications in therapy

Intestinal bacteria coexist with humans and play a role in suppressing the invasion of pathogens, producing short-chain fatty acids, producing vitamins, and controlling the immune system. Studies have been carried out on culturable bacterial species using bacterial culture methods for many years. However, as metagenomic analysis of bacterial genes has been developed since the 1990s, it has recently revealed that many bacteria in the intestine cannot be cultured and that approximately 1,000 species and 40 trillion bacteria are present in the gut microbiota. Furthermore, the composition of the microbiota is different in each disease state compared with the healthy state, and dysbiosis has received much attention as a cause of various diseases. Regarding gastrointestinal diseases, dysbiosis has been reported to be involved in inflammatory bowel disease, irritable bowel syndrome, and non-alcoholic steatohepatitis. Recent findings have also suggested that dysbiosis is involved in colon cancer, liver cancer, pancreatic cancer, esophageal cancer, and so on. This review focuses on the relationship between the gut microbiota and gastrointestinal/hepatobiliary diseases and also discusses new therapies targeting the gut microbiota.

Intratumoral microbiota: A new force in diagnosing and treating pancreatic cancer

Pancreatic cancer is an increasingly growing source of cancer-related deaths and is often diagnosed at advanced stages. Its treatment is difficult because of the poor results of conventional treatments, such as surgery, chemotherapy, and radiotherapy. Microbiota and their products can regulate the microenvironment of pancreatic tumors, the biological behavior of pancreatic cancer cells, and the functionality of the immune system. Promising results have been achieved in treating pancreatic cancer by regulating microbiota. However, intratumoral microbiota is still in its infancy as a new field of discovery for pancreatic cancer. This review summarizes the mechanisms by which intratumoral microbiota causes pancreatic cancer tumorigenesis, progression, and metastasis and demonstrates their significant potential in diagnosing and treating pancreatic cancer. Additionally, we present an outlook on the future of intratumoral microbiota in treating pancreatic cancer.

Are intratumoral microbiota involved in the progression of intraductal papillary mucinous neoplasms of the pancreas?

BACKGROUND

Microbiota have been reported to influence the development of various gastrointestinal neoplasms through the mechanism of sustained inflammation; however, few data are available regarding their influence on intraductal papillary mucinous neoplasms. The aim of this study was to assess the association between specific microbiota and the clinicopathologic characteristics of intraductal papillary mucinous neoplasms of the pancreas.

METHODS

DNA was extracted from formalin-fixed, paraffin-embedded samples of 30 patients who underwent pancreatectomy for intraductal papillary mucinous neoplasm, and polymerase chain reaction was used to create sequence libraries using the primer set for the V3 and V4 region of 16S recombinant DNA. Filtered sequence reads were then processed into operational taxonomic units with a 97% identity threshold and the relative abundance of bacteria compared between the 2 groups using operational taxonomic units.

RESULTS

There was a trend toward fewer Firmicutes and more Proteobacteria and Fusobacteria in the relative abundance of main duct operational taxonomic units than in branch duct operational taxonomic units. The relative abundances of Bacteroidetes (P < .01) and Fusobacteria (P = .04) were significantly higher in invasive intraductal papillary mucinous neoplasms than in noninvasive intraductal papillary mucinous neoplasms. The relative abundance of the intestinal type was significantly lower in Firmicutes than the relative abundance of the nonintestinal type (P = .04). Notably, main duct operational taxonomic units with the intestinal subtype were affected by increased proportions of Proteobacteria and Fusobacteria, and Fusobacteria were abundant in the intestinal type of invasive main duct operational taxonomic units.

CONCLUSION

Intratumoral microbiota may be involved in the progression of operational taxonomic units.

Could there be an interplay between periodontal changes and pancreatic malignancies?

The term "periodontal disease" refers to a group of chronic inflammatory illnesses caused by specific microorganisms from subgingival biofilm, that affect the tooth-supporting tissues. Recent research has also shown that periodontal infection plays a role in aggravating systemic disease states at distal sites, reinforcing the significance of the oral cavity for general health. Additionally, it has been suggested that gastroenterological malignancies may be promoted by hematogenous, enteral or lymphatic translocation of periopathogens. In the past 25 years, the global burden of pancreatic cancer (PC) has more than doubled, making it one of the major causes of cancer-related mortality. Periodontitis has been linked to at least 50% increased risk of PC and it could be considered a risk factor for this malignancy. A recent study performed on 59000 African American women with a follow up of 21 years showed that participants who had poor dental health had higher chances of PC. The findings, according to researchers, might be related to the inflammation that some oral bacteria trigger. Regarding the mortality of PC, periodontitis considerably raises the chance of dying from PC. Microbiome alterations in the gut, oral cavity and pancreatic tissues of PC patients occur when compared to healthy flora, demonstrating a link between PC and microecology. Inflammation may also contribute to PC development, although the underlying pathway is not yet known. The function of the microbiome in PC risk has drawn more focus over the last decade. Future risk of PC has been linked to the oral microbiome, specifically increased levels of Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans and decreased relative abundance of Leptotrichia and Fusobacteria, suggesting that it may have an impact on the inflammatory condition by expanding, altering, and regulating the commensal microbiome. Patients who received periodontal treatment had significantly decreased incidence rate ratios for PC. By analyzing patterns in the microbiome composition throughout PC development and establishing strategies to enhance the cancer-associated microbial system, we can increase the efficacy of therapy and eventually find an application for the microbial system. The development of immunogenomics and gut micro-genomics in the life sciences will result in a significant advancement in our understanding of how microbial systems and immunotherapy interact, and it may also have intriguing therapeutic implications for extending the lifetime of PC patients.

Pancreatic Cancer Resistance to Treatment: The Role of Microbiota

Pancreatic cancer (PC) is an aggressive malignancy and the fourth leading cause of cancer death in the United States and Europe. It is estimated that PC will be the second leading cause of cancer death by 2030. In addition to late diagnosis, treatment resistance is a major cause of shortened survival in pancreatic cancer. In this context, there is growing evidence that microbes play a regulatory role, particularly in therapy resistance and in creating a microenvironment in the tumor, that favors cancer progression. The presence of certain bacteria belonging to the gamma-proteobacteria or mycoplasmas appears to be associated with both pharmacokinetic and pharmacodynamic changes. Recent evidence suggests that the microbiota may also play a role in resistance mechanisms to immunotherapy and radiotherapy. However, the interactions between microbiota and therapy are bilateral and modulate therapy tolerance. Future perspectives are increasingly focused on elucidating the role of the microbiota in tumorigenesis and processes of therapy resistance, and a better understanding of these mechanisms may provide important opportunities to improve survival in these patients.

[Oral Microbiome and Systemic Diseases]

As one of the most diverse microbial communities within the human body, the oral microbiome is an important component that contributes to the maintenance of human health. The microbial composition of different sites in the oral cavity varies significantly and a dynamic equilibrium is maintained through communications with the environment and oral and distal organs of the host. It has been reported that there is significant correlation between dysbiotic oral microbiome and the occurrence or progression of a variety of systemic diseases. In this review, we summarized recent advances in research on the relationship between oral microbiome and systemic health, focusing on the interaction and pathological mechanisms between oral microbiome and systemic health and hoping to provide new avenues for the early prevention and clinical diagnosis and treatment of systemic diseases.

Microbiome and spatially resolved metabolomics analysis reveal the anticancer role of gut Akkermansia muciniphila by crosstalk with intratumoral microbiota and reprogramming tumoral metabolism in mice

Although gut microbiota has been linked to cancer, little is known about the crosstalk between gut- and intratumoral-microbiomes. The goal of this study was to determine whether gut Akkermansia muciniphila (Akk) is involved in the regulation of intratumoral microbiome and metabolic contexture, leading to an anticancer effect on lung cancer. We evaluated the effects of gut endogenous or gavaged exogenous Akk on the tumorigenesis using the Lewis lung cancer mouse model. Feces, blood, and tumor tissue samples were collected for 16S rDNA sequencing. We then conducted spatially resolved metabolomics profiling to discover cancer metabolites in situ directly and to characterize the overall Akk-regulated metabolic features, followed by the correlation analysis of intratumoral bacteria with metabolic network. Our results showed that both endogenous and exogenous gavaged Akk significantly inhibited tumorigenesis. Moreover, we detected increased Akk abundance in blood circulation or tumor tissue by 16S rDNA sequencing in the Akk gavaged mice, compared with the control mice. Of great interest, gavaged Akk may migrate into tumor tissue and influence the composition of intratumoral microbiome. Spatially resolved metabolomics analysis revealed that the gut-derived Akk was able to regulate tumor metabolic pathways, from metabolites to enzymes. Finally, our study identified a significant correlation between the gut Akk-regulated intratumoral bacteria and metabolic network. Together, gut-derived Akk may migrate into blood circulation, and subsequently colonize into lung cancer tissue, which contributes to the suppression of tumorigenesis by influencing tumoral symbiotic microbiome and reprogramming tumoral metabolism, although more studies are needed.

Clinical Microbial Identification of Severe Oral Infections by MALDI-TOF Mass Spectrometry in Stockholm County: an 11-Year (2010 to 2020) Epidemiological Investigation

Growing evidence suggests that oral infections can modify the course of systemic diseases. To date, epidemiological data on microbial oral infections are scarce. Here, we performed a comprehensive analysis of the trend and microbial diversity in oral infection specimens referred for clinical microbiology analysis from 2010 to 2020. The microbes were isolated by culture and were identified via matrix-assisted laser desorption ionization-time of flight mass spectrometry technology (MALDI-TOF MS) throughout the study period. A total of 1,014 referred samples from dental clinics in Stockholm County with dentoalveolar abscesses and jaw osteomyelitis being the main reason were identified. Overall, the microbial composition was dominated by Firmicutes (51%), followed by Bacteroidetes (19%), Proteobacteria (12%), and Actinobacteria (5%). At the genus level, Streptococcus spp. (36%), Prevotella spp. (18%), and Staphylococcus spp. (11%) were among the most frequently reported. Interestingly, a strong increase in trend was noted for Streptococcus anginosus, Streptococcus mitis, Streptococcus sanguinis, Eikenella corrodens, Actinomyces spp., Aggregatibacter aphrophilus, Staphylococcus epidermidis, and Granulicatella adiacens during the study time (R = 0.66 to 0.89, P < 0.05), and a minor increase was noted for Enterococcus faecalis and Klebsiella spp., whereas steady levels were noted for most of the others. The present study shows the diversity of bacteria that have been involved in dental infections during the last decade in the capital of Sweden, as well as the emerging oral microbiota trend, with clear clinical implications on the oral-systemic link. IMPORTANCE Oral diseases and associated microbes are a risk factor for systemic diseases and can change the courses of these diseases. To date, epidemiological data on microbial oral infections are scarce, and longitudinal reports are lacking. We present for the first time the microbial composition of severe oral bacterial infections determined via the MALDI-TOF mass spectrometry technique in a comprehensive study between 2010 and 2020 (11 years) in Stockholm County. The trend and microbial diversity of oral infections were analyzed on referred clinical microbiological samples and were processed by standardized protocols. Trend increase was noted for Streptococcus anginosus, Streptococcus mitis, Streptococcus sanguinis, Eikenella corrodens, Actinomyces spp., Aggregatibacter aphrophilus, Staphylococcus epidermidis, Granulicatella adiacens, Enterococcus faecalis, and Klebsiella spp. Our results provide new insights into the diversity and trend of oral microbiota that were involved in serious oral infections over the past decade in the capital of Sweden and may influence the oral-systemic link.

Microbiota in the Natural History of Pancreatic Cancer: From Predisposition to Therapy

Early microbiome insights came from gut microbes and their role among intestinal and extraintestinal disease. The latest evidence suggests that the microbiota is a true organ, capable of several interactions throughout the digestive system, attracting specific interest in the biliopancreatic district. Despite advances in diagnostics over the last few decades and improvements in the management of this disease, pancreatic cancer is still a common cause of cancer death. Microbiota can influence the development of precancerous disease predisposing to pancreatic cancer (PC). At the same time, neoplastic tissue shows specific characteristics in terms of diversity and phenotype, determining the short- and long-term prognosis. Considering the above information, a role for microbiota has also been hypothesized in the different phases of the PC approach, providing future revolutionary therapeutic insights. Microbiota-modulating therapies could open new issues in the therapeutic landscape. The aim of this narrative review is to assess the most updated evidence on microbiome in all the steps regarding pancreatic adenocarcinoma, from early development to response to antineoplastic therapy and long-term prognosis.

Poor dental health and risk of pancreatic cancer: a nationwide registry-based cohort study in Sweden, 2009-2016

BACKGROUND

Previous studies have reported inconsistent results regarding the association between poor dental health and pancreatic cancer risk. This study aimed to assess this association using a well-functioning nationwide dental health registry in Sweden.

METHODS

Information of exposures (dental caries, root canal infection, mild inflammation, and periodontitis; the number of teeth) was ascertained from the Swedish Dental Health Register, and occurrence of pancreatic cancer was identified from both cancer and cause of death registries. Hazard ratios (HRs) were estimated using Cox models.

RESULTS

During a median of 7.2 years of follow-up, 10,081 pancreatic cancers were identified among 5,889,441 individuals. Compared with the healthy status, a higher risk of pancreatic cancer was observed in individuals with root canal infection, mild inflammation, and periodontitis in the <50 age group (P for trend <0.001). In the 50-70 age group, only the subgroup with periodontitis had an excess risk (multivariable-adjusted HR = 1.20, 95% confidence interval [CI] 1.11-1.29). No positive association with statistical significance was observed in the 70+ age group. Individuals with fewer teeth tended to have a higher risk in all age groups.

CONCLUSIONS

Our results confirmed the association between poor dental health and pancreatic cancer risk, which warrants further studies on underlying mechanisms.

Research Progress in Intestinal Microecology in Pancreatic Cancer Diagnosis and Treatment

The intestinal microbiota has an increasingly recognized role in the development of cancer, in which microbial interactions play a more important than expected role. Pancreatic cancer is a highly fatal disease, in which its mortality is closely related to its morbidity. Early detection is the best chance of improving survival. Through an in-depth understanding of the pancreatic cancer microbiota, we could establish screening or early diagnosis methods for pancreatic cancer, implement bacterial treatment, adjust the therapeutic effect, and even reduce adverse reactions. These would lead to new developments and provide hope for patients with pancreatic cancer. Herein, we review the progress in intestinal microbiology research to diagnose and treat pancreatic cancer.

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.

The tumour immune microenvironment and microbiome of pancreatic intraductal papillary mucinous neoplasms

Pancreatic intraductal papillary mucinous neoplasms (IPMNs) have gained substantial attention because they represent one of the only radiographically identifiable precursors of invasive pancreatic ductal adenocarcinoma. Although most of these neoplasms have low-grade dysplasia and will remain indolent, a subset of IPMNs will progress to invasive cancer. The role of the immune system in the progression of IPMNs is unclear, but understanding its role could reveal the mechanism of neoplastic progression and targets for immunotherapy to inhibit progression or treat invasive disease. The available evidence supports a shift in the immune composition of IPMNs during neoplastic progression. Although low-grade lesions contain a high proportion of effector T cells, high-grade IPMNs, and IPMNs with an associated invasive carcinoma lose the T-cell infiltrate and are characterised by a predominance of immunosuppressive elements. Several possible therapeutic strategies emerge from this analysis that are unique to IPMNs and its microbiome.

Oral Microbiota and Tumor-A New Perspective of Tumor Pathogenesis

Microorganisms have long been known to play key roles in the initiation and development of tumors. The oral microbiota and tumorigenesis have been linked in epidemiological research relating to molecular pathology. Notably, some bacteria can impact distal tumors by their gastrointestinal or blood-borne transmission under pathological circumstances. Certain bacteria drive tumorigenesis and progression through direct or indirect immune system actions. This review systemically discusses the recent advances in the field of oral microecology and tumor, including the oncogenic role of oral microbial abnormalities and various potential carcinogenesis mechanisms (excessive inflammatory response, host immunosuppression, anti-apoptotic activity, and carcinogen secretion) to introduce future directions for effective tumor prevention.

Differential Oral Microbial Input Determines Two Microbiota Pneumo-Types Associated with Health Status

The oral and upper respiratory tracts are closely linked anatomically and physiologically with the lower respiratory tract and lungs, and the influence of oral and upper respiratory microbes on the lung microbiota is increasingly being recognized. However, the ecological process and individual heterogeneity of the oral and upper respiratory tract microbes shaping the lung microbiota remain unclear owing to the lack of controlled analyses with sufficient sample sizes. Here, the microbiomes of saliva, nasal cavity, oropharyngeal area, and bronchoalveolar lavage samples are profiled and the shaping process of multisource microbes on the lung microbiota is measured. It is found that oral and nasal microbial inputs jointly shape the lung microbiota by occupying different ecological niches. It is also observed that the spread of oral microbes to the lungs is heterogeneous, with more oral microbes entering the lungs being associated with decreased lung function and increased lung proinflammatory cytokines. These results depict the external shaping process of lung microbiota and indicate the great value of oral samples, such as saliva, in monitoring and assessing lung microbiota status in clinical settings.

Fusobacterium nucleatum induces proliferation and migration in pancreatic cancer cells through host autocrine and paracrine signaling

The tumor microbiome is increasingly implicated in cancer progression and resistance to chemotherapy. In pancreatic ductal adenocarcinoma (PDAC), high intratumoral loads of Fusobacterium nucleatum correlate with shorter survival in patients. Here, we investigated the potential mechanisms underlying this association. We found that F. nucleatum infection induced both normal pancreatic epithelial cells and PDAC cells to secrete increased amounts of the cytokines GM-CSF, CXCL1, IL-8, and MIP-3α. These cytokines increased proliferation, migration, and invasive cell motility in both infected and noninfected PDAC cells but not in noncancerous pancreatic epithelial cells, suggesting autocrine and paracrine signaling to PDAC cells. This phenomenon occurred in response to Fusobacterium infection regardless of the strain and in the absence of immune and other stromal cells. Blocking GM-CSF signaling markedly limited proliferative gains after infection. Thus, F. nucleatum infection in the pancreas elicits cytokine secretion from both normal and cancerous cells that promotes phenotypes in PDAC cells associated with tumor progression. The findings support the importance of exploring host-microbe interactions in pancreatic cancer to guide future therapeutic interventions.

Association of oral microbiome and pancreatic cancer: a systematic review and meta-analysis

BACKGROUND

Oral microbiota reported to be associated with pancreatic diseases, including pancreatic cancer. However, the association of oral microbiome and pancreatic cancer has not been reviewed systematically.

OBJECTIVES

To systematically investigate the association between the oral microbiome and pancreatic cancer risk.

DESIGN

A systematic review and meta-analysis.

DATA SOURCES AND METHODS

Systemic searches were conducted using PubMed, Medline, Cochrane Library, and Embase databases without any language restriction from conception to August 29, 2020. The studies that evaluated the association of oral microbiome and pancreatic cancer risk were included in this meta-analysis.

RESULTS

The six included studies encompassed a total of 863 pancreatic cancer cases and 906 controls. Four studies reported the overall oral microbiome in pancreatic cancer cases. A total of 12-17 species/clusters were correlated with pancreatic cancer. Three studies reported the odds ratios (ORs) or relative abundance of several oral microbiomes pieces/clusters, and the majority were associated with pancreatic cancer.

CONCLUSIONS

Overall, this study supports the hypothesis of associations of variations of patients' oral microbiota to pancreatic cancer. Nonetheless, due to all included studies were conducted in USA or Europe, additional original studies and meta-analysis particular studies from other countries are essential for an in-depth investigation into the role of oral bacteria in pancreatic cancer.

The Role of the Microbiome in Pancreatic Cancer

Simple Summary

Pancreatic cancer is deadly cancer characterized by dense stroma creating an immunosuppressive tumor microenvironment. Accumulating evidences indicate that the microbiome plays an important role in pancreatic cancer development and progression via the local and systemic inflammation and immune responses. The alteration of the microbiome modulates the tumor microenvironment and immune system in pancreatic cancer, which affects the efficacy of chemotherapies including immune-targeted therapies. Understanding the role of microbiome and underlying mechanisms may lead to novel biomarkers and therapeutic strategies for pancreatic cancer. This review summarizes the current evidence on the role of the microbiome in pancreatic cancer.

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignancies, with little improvement in outcomes in recent decades, although the molecular and phenotypic characterization of PDAC has contributed to advances in tailored therapies. PDAC is characterized by dense stroma surrounding tumor cells, which limits the efficacy of treatment due to the creation of a physical barrier and immunosuppressive environment. Emerging evidence regarding the microbiome in PDAC implies its potential role in the initiation and progression of PDAC. However, the underlying mechanisms of how the microbiome affects the local tumor microenvironment (TME) as well as the systemic immune system have not been elucidated in PDAC. In addition, therapeutic strategies based on the microbiome have not been established. In this review, we summarize the current evidence regarding the role of the microbiome in the development of PDAC and discuss a possible role for the microbiome in the early detection of PDAC in relation to premalignant pancreatic diseases, such as chronic pancreatitis and intraductal papillary mucinous neoplasm (IPMN). In addition, we discuss the potential role of the microbiome in the treatment of PDAC, especially in immunotherapy, although the biomarkers used to predict the efficacy of immunotherapy in PDAC are still unknown. A comprehensive understanding of tumor-associated immune responses, including those involving the microbiome, holds promise for new treatments in PDAC.

A Commentary on the Potential Use of Oral Microbiome in Prediction, Diagnosis or Prognostics of a Distant Pathology

In health, the oral microbiome is in balance with its host. If this balance is lost, this symbiosis is replaced by dysbiotic microbial communities, which are thought to affect the rest of the body either directly or via metabolites or pro-inflammatory molecules. The association of oral microbiome with general health has led to attempts to use oral microbial biomarkers for the prediction, diagnosis or prognosis of distant pathologies such as colorectal carcinoma or pancreatic cancer. These attempts however have no chance to succeed if the complexity of the oral ecosystem and the interplay of environmental, behavioral and biological factors is not taken into account. Standardized, well-documented oral sample collection procedures together with detailed clinical oral examination and behavioral data are the prerequisites for the successful evaluation of the oral microbiome as a potential biomarker for distant pathologies.

Human microbiota colonization and pancreatic ductal carcinoma

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive disease with a high mortality rate and a poor prognosis. The human microbiota has been confirmed to participate in oncogenesis and may influence the treatment response to both chemotherapy and immunotherapy. Evidence for the association of the microbiota with PDAC risk, tumorigenesis, treatment response, and survival period is rapidly emerging. The oral microbiota and gut microbiota have the potential to be used in early diagnosis and risk stratification. Intratumor microbiota-targeted intervention strategies may be used as adjuvants to current treatments to improve therapeutic efficacy and overall survival. Here, we summarize the effect and association of the oral, gut and intratumor microbiota on the oncogenesis, progression and treatment of PDAC, as well as the potential of the microbiota to serve as a biomarker for the diagnosis and prognosis of PDAC, as well as a therapeutic target.

Oral Microbiota Variation: A Risk Factor for Development and Poor Prognosis of Esophageal Cancer

Recent studies have shown that oral microbiota play an important role in the esophageal cancer (EC) initiation and progression, suggesting that oral microbiota is a new risk factor for EC. The composition of the microbes inhabiting the oral cavity could be perturbed with continuous factors such as smoking, alcohol consumption, and inflammation. The microbial alteration involves the decrease of beneficial species and the increase of pathogenic species. Experimental evidences suggest a significant role of oral commensal organisms in protecting hosts against EC. By contrast, oral pathogens, especially Porphyromonas gingivalis and Fusobacterium nucleatum, give rise to the risk for developing EC through their pro-inflammatory and pro-tumorigenic activities. The presences of oral dysbiosis, microbial biofilm, and periodontitis in EC patients are found to be associated with invasive cancer phenotypes and poor prognosis. The mechanism of oral bacteria in EC progression is complex, which involves a combination of cytokines, chemokines, oncogenic signaling pathways, cell surface receptors, the degradation of extracellular matrix, and cell apoptosis. From a clinical perspective, good oral hygiene, professional oral care, and rational use of antibiotics bring positive impacts on oral microbial balance, thus helping individuals reduce the risk of EC, inhibiting postoperative complications among EC patients, and improving the efficiency of chemoradiotherapy. However, current oral hygiene practices mainly focus on the oral bacteria-based predictive and preventive purposes. It is still far from implementing microbiota-dependent regulation as a therapy for EC. Further explorations are needed to render oral microbiota a potential target for treating EC.

Characterization of Bacterial Differences Induced by Cleft-Palate-Related Spatial Heterogeneity

Background: Cleft palate (CP) patients have a higher prevalence of oral and respiratory tract bacterial infections than the general population. Nevertheless, characteristics of bacterial differences induced by CP-related anatomical heterogeneity are unknown. Methods: In this study, we systematically described the characteristics of bacteria in the oral and nasal niches in healthy children, CP children, healthy adolescents, CP adolescents, and postoperative adolescents by 454-pyrosequencing technology (V3−V6) to determine bacterial differences induced by CP. Results: Due to the CP-induced variations in spatial structure, the early establishment of microecology in CP children was different from that in healthy children. Nasal bacterial composition showed greater changes than in the saliva. Moreover, such discrepancy also appeared in CP and postoperative adolescents who had even undergone surgery > 10 years previously. Interestingly, we found by Lefse analysis that part of bacterial biomarkers in the nasal cavity of CP subjects was common oral flora, suggesting bacterial translocation between the oral and nasal niches. Therefore, we defined the oral−nasal translocation bacteria as O-N bac. By comparing multiple groups, we took the intersection sets of O-N bacs selected from CP children, CP adolescents, and postoperative adolescents as TS O-N bacs with time−character, including Streptococcus, Gemella, Alloprevotella, Neisseria, Rothia, Actinomyces, and Veillonella. These bacteria were at the core of the nasal bacterial network in CP subjects, and some were related to infectious diseases. Conclusions: CP would lead to significant and long-term differences in oral and nasal flora. TS O-N bacs migrating from the oral to the nasal might be the key stone causing nasal flora dysbiosis in the CP patients.

Microbiota in Tumors: From Understanding to Application

Microbes with complex functions have been found to be a potential component in tumor microenvironments. Due to their low biomass and other obstacles, intratumor microbiota is poorly understood. Mucosal sites and normal adjacent tissues are important sources of intratumor microbiota, while hematogenous spread also leads to the invasion of microbes. Intratumor microbiota affects the progression of tumors through several mechanisms, such as DNA damage, activation of oncogenic pathways, induction of immunosuppression, and metabolization of drugs. Notably, in different types of tumors, the composition and abundance of intratumor microbiota are highly heterogeneous and may play different roles in the progression of tumors. Because of the concern in this field, several techniques such as omics and immunological methods have been used to study intratumor microbiota. Here, recent progress in this field is reviewed, including the potential sources of intratumor microbiota, their functions and related mechanisms, and their heterogeneity. Techniques that can be used to study intratumor microbiota are also discussed. Moreover, research is summarized into the development of strategies that can be used in antitumor treatment and prospects for possible future research in this field.

Poor Oral Health and Esophageal Cancer Risk: A Nationwide Cohort Study

BACKGROUND

Previous research indicates that poor dental health increases risks for certain types of cancers, including esophageal cancer. This study aimed to investigate the association with esophageal cancer using Swedish Dental Health Register.

METHODS

This is a prospective cohort study. The exposures were dental diagnoses classified into healthy, caries, root canal infection, mild inflammation, and periodontitis, as well as number of remaining teeth, at baseline and during multiple visits. The outcome was the incidence of esophageal cancer, which was further divided into esophageal adenocarcinoma (EAC) and esophageal squamous cell carcinoma (ESCC). Cox proportional hazards models were used to estimate hazard ratios (HR) and its corresponding confidence intervals (CI).

RESULTS

A total of 5,042,303 individuals were included in the study and 1,259 EAC and 758 ESCC cases were identified. Root canal infection at baseline was associated with 41% higher risk for EAC (HR, 1.41; 95% CI, 1.10-1.82), whereas periodontitis at baseline was linked to 32% and 45% higher risks for respective histopathological subtypes (HR for EAC, 1.32; 95% CI, 1.13-1.53; HR for ESCC, 1.45; 95% CI, 1.20-1.75). Fewer remaining teeth at baseline also increased the risks for both histopathological types of esophageal cancer, with a dose-response effect (Ptrend < 0.01). Cox regression analyses with time-varying exposures corroborated the above-mentioned results.

CONCLUSIONS

Impaired dental health before cancer diagnosis is associated with excess risks for both histopathological subtypes of esophageal cancer.

IMPACT

Our study provided corroborating evidence for the association between poor oral health and esophageal cancer risk.

A faecal microbiota signature with high specificity for pancreatic cancer

BACKGROUND

Recent evidence suggests a role for the microbiome in pancreatic ductal adenocarcinoma (PDAC) aetiology and progression.

OBJECTIVE

To explore the faecal and salivary microbiota as potential diagnostic biomarkers.

METHODS

We applied shotgun metagenomic and 16S rRNA amplicon sequencing to samples from a Spanish case-control study (n=136), including 57 cases, 50 controls, and 29 patients with chronic pancreatitis in the discovery phase, and from a German case-control study (n=76), in the validation phase.

RESULTS

Faecal metagenomic classifiers performed much better than saliva-based classifiers and identified patients with PDAC with an accuracy of up to 0.84 area under the receiver operating characteristic curve (AUROC) based on a set of 27 microbial species, with consistent accuracy across early and late disease stages. Performance further improved to up to 0.94 AUROC when we combined our microbiome-based predictions with serum levels of carbohydrate antigen (CA) 19-9, the only current non-invasive, Food and Drug Administration approved, low specificity PDAC diagnostic biomarker. Furthermore, a microbiota-based classification model confined to PDAC-enriched species was highly disease-specific when validated against 25 publicly available metagenomic study populations for various health conditions (n=5792). Both microbiome-based models had a high prediction accuracy on a German validation population (n=76). Several faecal PDAC marker species were detectable in pancreatic tumour and non-tumour tissue using 16S rRNA sequencing and fluorescence in situ hybridisation.

CONCLUSION

Taken together, our results indicate that non-invasive, robust and specific faecal microbiota-based screening for the early detection of PDAC is feasible.

Fusobacterium nucleatum and Malignant Tumors of the Digestive Tract: A Mechanistic Overview

Fusobacterium nucleatum (F. nucleatum) is an oral anaerobe that plays a role in several oral diseases. However, F. nucleatum is also found in other tissues of the digestive tract, and several studies have recently reported that the level of F. nucleatum is significantly elevated in malignant tumors of the digestive tract. F. nucleatum is proposed as one of the risk factors in the initiation and progression of digestive tract malignant tumors. In this review, we summarize recent reports on F. nucleatum and its role in digestive tract cancers and evaluate the mechanisms underlying the action of F. nucleatum in digestive tract cancers.

Diurnal and eating-associated microbial patterns revealed via high-frequency saliva sampling

The oral microbiome is linked to oral and systemic health, but its fluctuation under frequent daily activities remains elusive. Here, we sampled saliva at 10- to 60-min intervals to track the high-resolution microbiome dynamics during the course of human activities. This dense time series data showed that eating activity markedly perturbed the salivary microbiota, with tongue-specific Campylobacter concisus and Oribacterium sinus and dental plaque-specific Lautropia mirabilis, Rothia aeria, and Neisseria oralis increased after every meal in a temporal order. The observation was reproducible in multiple subjects and across an 11-mo period. The microbiome composition showed significant diurnal oscillation patterns at different taxonomy levels with Prevotella/Alloprevotella increased at night and Bergeyella HMT 206/Haemophilus slowly increased during the daytime. We also identified microbial co-occurring patterns in saliva that are associated with the intricate biogeography of the oral microbiome. Microbial source tracking analysis showed that the contributions of distinct oral niches to the salivary microbiome were dynamically affected by daily activities, reflecting the role of saliva in exchanging microbes with other oral sites. Collectively, our study provides insights into the temporal microbiome variation in saliva and highlights the need to consider daily activities and diurnal factors in design of oral microbiome studies.

The huge clinical potential of microbiota in the treatment of pancreatic cancer: The next frontier

Microbes and their metabolites are found in all body organs; their interaction with body organs can influence inflammation, immunity, and cancer development. Pancreatic cancer development is closely related to intestinal, intrapancreatic, and oral flora. The microbiota plays a regulatory role in pancreatic cancer's malignant progression and treatment resistance. Thus, the study of microbiota-host interactions has emerged as a new hot topic in pancreatic cancer treatment, with microbiota control demonstrating significant clinical potential. This review summarizes recent advances in the clinical diagnosis and treatment of pancreatic cancer, emphasizing the enormous potential for operating microbiota in pancreatic cancer treatment.

Potential Role of Inflammation-Promoting Biliary Microbiome in Primary Sclerosing Cholangitis and Cholangiocarcinoma

Background: Primary sclerosing cholangitis (PSC) is a major risk factor for cholangiocarcinoma (CCA). We investigated biliary and fecal microbiota to determine whether specific microbes in the bile or stool are associated with PSC or CCA. Methods: Bile was obtained from 32 patients with PSC, 23 with CCA with PSC, 26 with CCA without PSC, and 17 controls. Over 90% of bile samples were from patients with perihilar CCA. Stool was obtained from 31 patients with PSC (11 were matched to bile), 16 with CCA with PSC (10 matched to bile), and 11 with CCA without PSC (6 matched to bile). Microbiota composition was assessed using 16SrRNA-marker-based sequencing and was compared between groups. Results: Bile has a unique microbiota distinguished from negative DNA controls and stool. Increased species richness and abundance of Fusobacteria correlated with duration of PSC and characterized the biliary microbiota in CCA. Stool microbiota composition showed no significant differences between groups. Conclusions: We identified a unique microbial signature in the bile of patients with increased duration of PSC or with CCA, suggesting a role for microbiota-driven inflammation in the pathogenesis and or progression to perihilar CCA. Further studies are needed to test this hypothesis.

Recent advances in understanding pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is an intractable cancer and a leading cause of cancer deaths worldwide. Over 90% of patients die within 1 year of diagnosis. Deaths from PDAC are increasing and it remains a cancer of substantial unmet need. A number of factors contribute to its poor prognosis: namely, late presentation, early metastases and limited systemic therapy options because of chemoresistance. A variety of research approaches underway are aimed at improving patient survival. Here, we review high-risk groups and efforts for early detection. We examine recent developments in the understanding of complex molecular and metabolic alterations which accompany PDAC. We explore artificial intelligence and biological targets for therapy and examine the role of tumour stroma and the immune microenvironment. We also review recent developments with respect to the PDAC microbiome. It is hoped that current research efforts will translate into earlier diagnosis, improvements in treatment and better outcomes for patients.

Lactobacillus Suppresses Tumorigenesis of Oropharyngeal Cancer via Enhancing Anti-Tumor Immune Response

Deficiency in T cell-mediated adaptive immunity, such as low CD8⁺ T cell infiltration, inhibits the immune surveillance, promotes malignant transformation, and facilitates tumor growth. Microbiota dysbiosis diminishes the immune system and contributes to the occurrence of cancer. However, the impact of oral dysbiosis on the occurrence and molecular mechanisms of oropharyngeal cancer (OPC) remains largely unknown. In the current study, we used 4-nitroquinoline-1-oxide (4NQO) to mimic tobacco-related carcinogenesis to generate a murine OPC model and determine the role of microbiota changes in OPC tumorigenesis. Our results showed that the oral flora composition of mice was deregulated during the tumorigenesis of OPC. The abundance of Streptococcus, Veillonella, Muribacter, Rodentibacter, and Gemella was increased, whereas the dominant genus Lactobacillus was gradually decreased with disease progression. We further demonstrated that infiltration of CD8⁺ T lymphocytes was markedly reduced due to the reduction of Lactobacillus. Supplementation of Lactobacillus increased the infiltration of CD8⁺ T cells, promoted the expression of IFN-γ and granzyme B, and lessened the OPC progression. Analyzing the metabolites of the Lactobacillus, we demonstrated that Lactobacillus enhanced the anti-tumor immune response by producing acetate in OPC development. Administration of acetate to mice could increase the expression of IFN-γ and IFN-γ-inducible chemokines in tumor tissues by activating GPR43 to promote the infiltration of CD8⁺ T lymphocytes and substantially delay the development of OPC. Together, our data suggest that dysbiosis of oral microbiota promotes the tumorigenesis of OPC through downregulation of cytotoxic T lymphocytes. Lactobacillus and its metabolite acetate improve the tumor microenvironment, which could be applied in the treatment of OPC.

Fusobacterium nucleatum and cancer

Accumulating evidence demonstrates that the oral pathobiont Fusobacterium nucleatum is involved in the progression of an increasing number of tumors types. Thus far, the mechanisms underlying tumor exacerbation by F. nucleatum include the enhancement of proliferation, establishment of a tumor‐promoting immune environment, induction of chemoresistance, and the activation of immune checkpoints. This review focuses on the mechanisms that mediate tumor‐specific colonization by fusobacteria. Elucidating the mechanisms mediating fusobacterial tumor tropism and promotion might provide new insights for the development of novel approaches for tumor detection and treatment.

Isolation of pancreatic microbiota from cystic precursors of pancreatic cancer with intracellular growth and DNA damaging properties

Emerging research suggests gut microbiome may play a role in pancreatic cancer initiation and progression, but cultivation of the cancer microbiome remains challenging. This pilot study aims to investigate the possibility to cultivate pancreatic microbiome from pancreatic cystic lesions associated with invasive cancer. Intra-operatively acquired pancreatic cyst fluid samples showed culture-positivity mainly in the intraductal papillary mucinous neoplasm (IPMN) group of lesions. MALDI-TOF MS profiling analysis shows Gammaproteobacteria and Bacilli dominate among individual bacteria isolates. Among cultivated bacteria, Gammaproteobacteria, particularly Klebsiella pneumoniae, but also Granulicatella adiacens and Enterococcus faecalis, demonstrate consistent pathogenic properties in pancreatic cell lines tested in ex vivo co-culture models. Pathogenic properties include intracellular survival capability, cell death induction, or causing DNA double-strand breaks in the surviving cells resembling genotoxic effects. This study provides new insights into the role of the pancreatic microbiota in the intriguing link between pancreatic cystic lesions and cancer.

Association of the Microbiota and Pancreatic Cancer: Opportunities and Limitations

The human body is thoroughly colonized by a wide variety of microorganisms, termed microbiota. Pancreatic cancer, one of the most aggressive forms of cancer, is no exception. The microbiota of pancreatic cancer largely influences and even dominates the occurrence, development and outcome of pancreatic cancer in many ways. Studies have shown that microbiota could change the malignant phenotype and prognosis of pancreatic cancer by stimulating persistent inflammation, regulating the antitumor immune system, changing the tumor microenvironment and affecting cellular metabolism. This is why the association of the microbiota with pancreatic cancer is an emerging area of research that warrants further exploration. Herein, we investigated the potential microbial markers of pancreatic cancer, related research models, the mechanism of action of microbiota in pancreatic cancer, and pancreatic cancer-microbiota-related treatment.

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

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.

Gut Dysbiosis in Pancreatic Diseases: A Causative Factor and a Novel Therapeutic Target

Pancreatic-related disorders such as pancreatitis, pancreatic cancer, and type 1 diabetes mellitus (T1DM) impose a substantial challenge to human health and wellbeing. Even though our understanding of the initiation and progression of pancreatic diseases has broadened over time, no effective therapeutics is yet available for these disorders. Mounting evidence suggests that gut dysbiosis is closely related to human health and disease, and pancreatic diseases are no exception. Now much effort is under way to explore the correlation and eventually potential causation between the gut microbiome and the course of pancreatic diseases, as well as to develop novel preventive and/or therapeutic strategies of targeted microbiome modulation by probiotics, prebiotics, synbiotics, postbiotics, and fecal microbiota transplantation (FMT) for these multifactorial disorders. Attempts to dissect the intestinal microbial landscape and its metabolic profile might enable deep insight into a holistic picture of these complex conditions. This article aims to review the subtle yet intimate nexus loop between the gut microbiome and pancreatic diseases, with a particular focus on current evidence supporting the feasibility of preventing and controlling pancreatic diseases via microbiome-based therapeutics and therapies.

A comprehensive analysis of intratumor microbiome in head and neck squamous cell carcinoma

PURPOSE

Human microbiome has been considered as the second genome of our body. The intratissue/intratumor microbiome analysis is a relatively new field and deserves more attention. In this study, we conducted a comprehensive analysis of microbiome signatures of head and neck squamous cell carcinoma (HNSC).

METHODS

The intratumor microbiome profiling and clinicopathological information about a total of 177 HNSC samples, including 155 tumors and 22 adjacent normal tissues, were obtained from The Cancer Microbiome Atlas (TCMA) and The Cancer Genome Atlas (TCGA) databases. We identified the microbes that differed between tumors and normal tissues, and assessed their utility values as diagnostic biomarkers. The microbiome signatures under different conditions of clinicopathological parameters were also analyzed.

RESULTS

The intratissue microbiome profiles differed between tumor and normal samples of HNSC. The composition of four, six, and six microbes changed in tumors compared to normal tissues at the phylum, order, and genus levels, respectively (P < 0.05). Eight of the differential microbes performed well in distinguishing tumors from normal tissues (AUC > 0.7, P ≤ 0.001). The microbiome signature was found to be associated with tumor clinicopathological characteristics such as host-gender, host-age, tumor stage, and neoplasm histologic grade.

CONCLUSION

Overall, our results revealed an intratissue microbiome signature of HNSC. We concluded that the intratumor microbiome signature may also reflect human biology in both healthy and disease status, and provide novel perspective for microbiota research about their roles in tumors.

pH-taxis drives aerobic bacteria in duodenum to migrate into the pancreas with tumors

As oral or intestinal bacteria have been found in pancreatic cystic fluid and tumors, understanding bacterial migration from the duodenum into the pancreas via hepato-pancreatic duct is critical. Mathematical models of migration of aerobic bacteria from the duodenum to the pancreas with tumors were developed. Additionally, the bacterial distributions under the pH gradient and those under flow were measured in double-layer flow based microfluidic device and T-shaped cylinders. Migration of aerobic bacteria from the duodenum into pancreas is counteracted by bile and pancreatic juice flow but facilitated by pH-taxis from acidic duodenum fluid toward more favorable slightly alkaline pH in pancreatic juice. Additionally, the reduced flow velocity in cancer patients, due to compressed pancreatic duct by solid tumor, facilitates migration. Moreover, measured distribution of GFP E. coli under the pH gradient in a microfluidic device validated pH-tactic behaviors. Furthermore, Pseudomonas fluorescens in hydrochloride solution, but not in bicarbonate solution, migrated upstream against bicarbonate flow of > 20 μm/s, with an advancement at approximately 50 μm/s.

Alterations in the Duodenal Fluid Microbiome of Patients With Pancreatic Cancer

BACKGROUND & AIMS

The tumor microbiome of patients with pancreas ductal adenocarcinoma (PDAC) includes bacteria normally present in the upper gastrointestinal tract. If the predominant source of intratumoral bacteria in patients with PDAC is retrograde migration from the duodenum, duodenal fluid could be a representative biospecimen for determining microbiome profiles of patients with PDAC or at risk of developing PDAC.

METHODS

We performed a case-control study comparing bacterial and fungal (16S and 18S rRNA) profiles of secretin-stimulated duodenal fluid collections from 308 patients undergoing duodenal endoscopy including 134 normal pancreas control subjects, 98 patients with pancreatic cyst(s) and 74 patients with PDAC.

RESULTS

Alterations in duodenal fluid microbiomes with diminished alpha diversity were significantly associated with age >70 and proton pump inhibitor use. Patients with PDAC had significantly decreased duodenal microbial alpha diversity compared with age-matched control subjects with normal pancreata and those with pancreatic cyst(s). There was evidence of enrichment of Bifidobacterium genera in the duodenal fluid of patients with PDAC compared with control subjects and those with pancreatic cyst(s). There were also enrichment of duodenal fluid Fusobacteria and Rothia bacteria among patients with PDAC with short-term survival. Duodenal fluid microbiome profiles were not significantly different between control subjects and patients with pancreatic cyst(s).

CONCLUSION

Patients with PDAC have alterations in their duodenal fluid microbiome profiles compared with patients with pancreatic cysts and those with normal pancreata. ClinicalTrials.gov, Number: NCT02000089.

Microbiota in Pancreatic Diseases: A Review of the Literature

The gut microbiota is a critical element in the balance between human health and disease. Its impairment, defined as dysbiosis, is associated with gastroenterological and systemic diseases. Pancreatic secretions are involved in the composition and changes of the gut microbiota, and the gut microbiota may colonize the pancreatic parenchyma and be associated with the occurrence of diseases. The gut microbiota and the pancreas influence each other, resulting in a "gut microbiota-pancreas axis". Moreover, the gut microbiota may be involved in pancreatic diseases, both through direct bacterial colonization and an indirect effect of small molecules and toxins derived from dysbiosis. Pancreatic diseases such as acute pancreatitis, chronic pancreatitis, autoimmune pancreatitis, and pancreatic cancer are common gastroenterological diseases associated with high morbidity and mortality. The involvement of the microbiota in pancreatic diseases is increasingly recognized. Therefore, modifying the intestinal bacterial flora could have important therapeutic implications on these pathologies. The aim of this study is to review the literature to evaluate the alterations of the gut microbiota in pancreatic diseases, and the role of the microbiota in the treatment of these diseases.

Dysbiosis of the duodenal microbiota as a diagnostic marker for pancreaticobiliary cancer

BACKGROUND

Pancreaticobiliary cancer (PB Ca) is a lethal disease, and a useful diagnostic marker is urgently needed. A correlation between the human microbiota and malignant gastrointestinal diseases was recently reported.

AIM

To investigate the efficacy of the duodenal microbiota for diagnosing PB Ca.

METHODS

We recruited 22 patients with benign pancreaticobiliary diseases (benign group) and 12 patients with PB Ca (malignant group). The duodenal microbiota of each patient was analyzed by the 16S rDNA terminal restriction fragment length polymorphism method. Patient characteristics, tumor markers, and relative abundances of the duodenal microbiota were compared between the benign and malignant groups.

RESULTS

Cancer antigen 19-9 (CA19-9), Bifidobacterium, Clostridium cluster XVIII, and Prevotella levels differed significantly between the benign and malignant groups. Clostridium cluster XVIII had the greatest area under the receiver operating characteristic curve (AUC) among the four factors with respect to diagnosing PB Ca (cutoff value: 3.038%; sensitivity: 58.3%; specificity: 95.2%; AUC: 0.81). The combination of Clostridium cluster XVIII (cutoff value: 3.038%) and CA19-9 Levels (cutoff value: 18.8 U/mL) showed 91.7% sensitivity and 71.4% specificity for diagnosing PB Ca.

CONCLUSION

The duodenal microbiota may be useful for PB Ca screening.

Human Gut Microbiota in Health and Selected Cancers

The majority of the epithelial surfaces of our body, and the digestive tract, respiratory and urogenital systems, are colonized by a vast number of bacteria, archaea, fungi, protozoans, and viruses. These microbiota, particularly those of the intestines, play an important, beneficial role in digestion, metabolism, and the synthesis of vitamins. Their metabolites stimulate cytokine production by the human host, which are used against potential pathogens. The composition of the microbiota is influenced by several internal and external factors, including diet, age, disease, and lifestyle. Such changes, called dysbiosis, may be involved in the development of various conditions, such as metabolic diseases, including metabolic syndrome, type 2 diabetes mellitus, Hashimoto's thyroidis and Graves' disease; they can also play a role in nervous system disturbances, such as multiple sclerosis, Alzheimer's disease, Parkinson's disease, and depression. An association has also been found between gut microbiota dysbiosis and cancer. Our health is closely associated with the state of our microbiota, and their homeostasis. The aim of this review is to describe the associations between human gut microbiota and cancer, and examine the potential role of gut microbiota in anticancer therapy.