Periodontal pathogens Porphyromonas gingivalis and Fusobacterium nucleatum promote tumor progression in an oral-specific chemical carcinogenesis model

Viruses, periodontitis, and comorbidities

Seminal studies published in the 1990s and 2000s explored connections between periodontal diseases and systemic conditions, revealing potential contributions of periodontal diseases in the initiation or worsening of systemic conditions. The resulting field of periodontal medicine led to the publication of studies indicating that periodontal diseases can influence the risk of systemic conditions, including adverse pregnancy outcomes, cardiovascular and respiratory diseases, as well as Alzheimer disease and cancers. In general, these studies hypothesized that the periodontal bacterial insult and/or the associated proinflammatory cascade could contribute to the pathogenesis of these systemic diseases. While investigations of the biological basis of the connections between periodontal diseases and systemic conditions generally emphasized the bacteriome, it is also biologically plausible, under an analogous hypothesis, that other types of organisms may have a similar role. Human viruses would be logical "suspects" in this role, given their ubiquity in the oral cavity, association with periodontal diseases, and ability to elicit strong inflammatory response, compromise immune responses, and synergize with bacteria in favor of a more pathogenic microbial consortium. In this review, the current knowledge of the role of viruses in connecting periodontal diseases and systemic conditions is examined. We will also delve into the mechanistic basis for such connections and highlight the importance of those relationships in the management and treatment of patients.

Oral microbiota in human systematic diseases

Oral bacteria directly affect the disease status of dental caries and periodontal diseases. The dynamic oral microbiota cooperates with the host to reflect the information and status of immunity and metabolism through two-way communication along the oral cavity and the systemic organs. The oral cavity is one of the most important interaction windows between the human body and the environment. The microenvironment at different sites in the oral cavity has different microbial compositions and is regulated by complex signaling, hosts, and external environmental factors. These processes may affect or reflect human health because certain health states seem to be related to the composition of oral bacteria, and the destruction of the microbial community is related to systemic diseases. In this review, we discussed emerging and exciting evidence of complex and important connections between the oral microbes and multiple human systemic diseases, and the possible contribution of the oral microorganisms to systemic diseases. This review aims to enhance the interest to oral microbes on the whole human body, and also improve clinician’s understanding of the role of oral microbes in systemic diseases. Microbial research in dentistry potentially enhances our knowledge of the pathogenic mechanisms of oral diseases, and at the same time, continuous advances in this frontier field may lead to a tangible impact on human health.

Fusobacterium nucleatum is associated with inflammation and poor survival in early-stage HPV-negative tongue cancer

Persistent pathogen infection is a known cause of malignancy, although with sparse systematic evaluation across tumor types. We present a comprehensive landscape of 1060 infectious pathogens across 239 whole exomes and 1168 transcriptomes of breast, lung, gallbladder, cervical, colorectal, and head and neck tumors. We identify known cancer-associated pathogens consistent with the literature. In addition, we identify a significant prevalence of Fusobacterium in head and neck tumors, comparable to colorectal tumors. The Fusobacterium-high subgroup of head and neck tumors occurs mutually exclusive to human papillomavirus, and is characterized by overexpression of miRNAs associated with inflammation, elevated innate immune cell fraction and nodal metastases. We validate the association of Fusobacterium with the inflammatory markers IL1B, IL6 and IL8, miRNAs hsa-mir-451a, hsa-mir-675 and hsa-mir-486-1, and MMP10 in the tongue tumor samples. A higher burden of Fusobacterium is also associated with poor survival, nodal metastases and extracapsular spread in tongue tumors defining a distinct subgroup of head and neck cancer.

Periodontitis, Metabolic and Gastrointestinal Tract Diseases: Current Perspectives on Possible Pathogenic Connections

Comprehensive research conducted over the past decades has shown that there is a definite connection between periodontal and systemic conditions, leading to the development and consolidation of the “periodontal medicine” concept. The 2018 classification of periodontal conditions uses this concept as a key element of the precise diagnosis of and individualized therapeutical protocols for periodontitis patients. The topic of this review is the pathogenic connections that exist between periodontal disease and metabolic/digestive tract conditions. It is important to remember that the oral cavity is a key element of the digestive tract and that any conditions affecting its integrity and function (such as periodontitis or oral cancer) can have a significant impact on the metabolic and gastrointestinal status of a patient. Thus, significant diseases with links to metabolic or digestive disruptions were chosen for inclusion in the review, such as diabetes mellitus, hepatic conditions and gastric cancers. Periodontal pathogenic mechanisms share several significant elements with these conditions, including mutual pro-inflammatory mediators, bacterial elements and genetic predisposition. Consequently, periodontal screening should be recommended for affected patients, and conversely, periodontitis patients should be considered for careful monitoring of their metabolic and digestive status.

More Than Just a Periodontal Pathogen –the Research Progress on Fusobacterium nucleatum

Fusobacterium nucleatum is a common oral opportunistic bacterium that can cause different infections. In recent years, studies have shown that F. nucleatum is enriched in lesions in periodontal diseases, halitosis, dental pulp infection, oral cancer, and systemic diseases. Hence, it can promote the development and/or progression of these conditions. The current study aimed to assess research progress in the epidemiological evidence, possible pathogenic mechanisms, and treatment methods of F. nucleatum in oral and systemic diseases. Novel viewpoints obtained in recent studies can provide knowledge about the role of F. nucleatum in hosts and a basis for identifying new methods for the diagnosis and treatment of F. nucleatum-related diseases.

Microbial Colonization and Inflammation as Potential Contributors to the Lack of Therapeutic Success in Oral Squamous Cell Carcinoma

This review discusses the microenvironment of evolving and established conventional oral squamous cell carcinoma, by far the most common oral cancer. The focus of this paper is mainly on the more recent data that describe the role of microorganisms, host-microbial interactions, and in particular, the contributions of cell-surface toll-like receptors on immune system cells and on normal and malignant epithelial cells to their functions that support carcinogenesis. Because carcinomas arising at various host surfaces share much in common, additional information available from studies of other carcinomas is included in the discussion. Accumulating evidence reveals the complex toll-like receptor-mediated tumor-supporting input into many aspects of carcinogenesis via malignant cells, stromal immune cells and non-immune cells, complicating the search for effective treatments.

Molecular Mechanisms Leading from Periodontal Disease to Cancer

Periodontitis is prevalent in half of the adult population and raises critical health concerns as it has been recently associated with an increased risk of cancer. While information about the topic remains somewhat scarce, a deeper understanding of the underlying mechanistic pathways promoting neoplasia in periodontitis patients is of fundamental importance. This manuscript presents the literature as well as a panel of tables and figures on the molecular mechanisms of Porphyromonas gingivalis and Fusobacterium nucleatum, two main oral pathogens in periodontitis pathology, involved in instigating tumorigenesis. We also present evidence for potential links between the RANKL–RANK signaling axis as well as circulating cytokines/leukocytes and carcinogenesis. Due to the nonconclusive data associating periodontitis and cancer reported in the case and cohort studies, we examine clinical trials relevant to the topic and summarize their outcome.

Crosstalk between autophagy and microbiota in cancer progression

Autophagy is a highly conserved catabolic process seen in eukaryotes and is essentially a lysosome-dependent protein degradation pathway. The dysregulation of autophagy is often associated with the pathogenesis of numerous types of cancers, and can not only promote the survival of cancer but also trigger the tumor cell death. During cancer development, the microbial community might predispose cells to tumorigenesis by promoting mucosal inflammation, causing systemic disorders, and may also regulate the immune response to cancer. The complex relationship between autophagy and microorganisms can protect the body by activating the immune system. In addition, autophagy and microorganisms can crosstalk with each other in multifaceted ways to influence various physiological and pathological responses involved in cancer progression. Various molecular mechanisms, correlating the microbiota disorders and autophagy activation, control the outcomes of protumor or antitumor responses, which depend on the cancer type, tumor microenvironment and disease stage. In this review, we mainly emphasize the leading role of autophagy during the interaction between pathogenic microorganisms and human cancers and investigate the various molecular mechanisms by which autophagy modulates such complicated biological processes. Moreover, we also highlight the possibility of curing cancers with multiple molecular agents targeting the microbiota/autophagy axis. Finally, we summarize the emerging clinical trials investigating the therapeutic potential of targeting either autophagy or microbiota as anticancer strategies, although the crosstalk between them has not been explored thoroughly.

A prospective interventional trial on the effect of periodontal treatment on Fusobacterium nucleatum abundance in patients with colorectal tumours

Fusobacterium nucleatum is associated with the progression of colorectal cancer. Thus, the possibility of preventing colorectal cancer or its progression by targeting F. nucleatum has been explored. As F. nucleatum is associated with periodontitis, we analysed whether treating periodontitis could influence F. nucleatum abundance in the colon. Patients with colorectal tumours who underwent colonoscopy were recruited. Patients diagnosed with periodontitis by a dentist were treated for approximately 3 months. Endoscopic resection of colorectal tumours was performed after periodontitis treatment, and resected tumours were pathologically classified as high-(HGD) or low-grade dysplasia (LGD). Saliva and stool samples were collected before and after the treatment. Of the 58 patients with colorectal tumours, 31 were included in the study, 16 showed improvement in periodontitis, and 11 showed no improvement. Stool F. nucleatum levels before treatment were significantly lower in the LGD group than in the HGD group. A significant decrease in faecal F. nucleatum levels was observed in patients who underwent successful treatment but not in those whose treatment failed. Salivary F. nucleatum levels were not altered in patients despite periodontal treatment. Thus, successful periodontitis treatment reduces stool F. nucleatum levels and may aid research on periodontitis and suppression of colorectal cancer development.

Porphyromonas gingivalis in oral squamous cell carcinoma: A review

Oral cancer contributes significantly to the global cancer burden. Oral bacteria play an important role in the spread of oral cancer, according to mounting evidence. The most proven instance is the carcinogenic implications of Porphyromonas gingivalis, a key pathogen in chronic periodontitis. It is imperative to understand the pathogenesis of P. gingivalis in OSCC. This review aims to gather and assess scientific shreds of evidence on the involvement of Porphyromonas gingivalis in the molecular mechanism of oral squamous cell carcinoma.

The role played by bacterial infections in the onset and metastasis of cancer

Understanding various responses of cells towards change in their external environment, presence of other species and is important in identifying and correlating the mechanisms leading to malignant transformations and cancer development. Although uncovering and comprehending the association between bacteria and cancer is highly challenging, it promises excellent perspectives and approaches for successful cancer therapy. This review introduces various bacterial species, their virulence factors, and their role in cell transformations leading to cancer (particularly gastric, oral, colon, and breast cancer). Bacterial dysbiosis permutates host cells, causes inflammation, and results in tumorigenesis. This review explored bacterial-mediated host cell transformation causing chronic inflammation, immune receptor hyperactivation/absconding immune recognition, and genomic instability. Bacterial infections downregulate E-cadherin, leading to loosening of epithelial tight junction polarity and triggers metastasis. In addition to understanding the role of bacterial infections in cancer development, we have also reviewed the application of bacteria for cancer therapy. The emergence of bacteriotherapy combined with conventional therapies led to new and effective ways of overcoming challenges associated with available treatments. This review discusses the application of bacterial minicells, microswimmers, and outer cell membrane vesicles (OMV) for drug delivery applications.

Is There an Interplay between Oral Microbiome, Head and Neck Carcinoma and Radiation-Induced Oral Mucositis?

Head and neck carcinoma is one of the most common human malignancy types and it ranks as the sixth most common cancer worldwide. Nowadays, a great potential of microbiome research is observed in oncology-investigating the effect of oral microbiome in oncogenesis, occurrence of treatment side effects and response to anticancer therapies. The microbiome is a unique collection of microorganisms and their genetic material, interactions and products residing within the mucous membranes. The aim of this paper is to summarize current research on the oral microbiome and its impact on the development of head and neck cancer and radiation-induced oral mucositis. Human microbiome might determine an oncogenic effect by, among other things, inducing chronic inflammatory response, instigating cellular antiapoptotic signals, modulation of anticancer immunity or influencing xenobiotic metabolism. Influence of oral microbiome on radiation-induced oral mucositis is expressed by the production of additional inflammatory cytokines and facilitates progression and aggravation of mucositis. Exacerbated acute radiation reaction and bacterial superinfections lead to the deterioration of the patient's condition and worsening of the quality of life. Simultaneously, positive effects of probiotics on the course of radiation-induced oral mucositis have been observed. Understanding the impact on the emerging acute radiation reaction on the composition of the microflora can be helpful in developing a multifactorial model to forecast the course of radiation-induced oral mucositis. Investigating these processes will allow us to create optimized and personalized preventive measures and treatment aimed at their formation mechanism. Further studies are needed to better establish the structure of the oral microbiome as well as the dynamics of its changes before and after therapy. It will help to expand the understanding of the biological function of commensal and pathogenic oral microbiota in HNC carcinogenesis and the development of radiation-induced oral mucositis.

Simultaneous occurrence of Epstein-Barr virus (EBV) in periodontal pockets and in oral squamous cell carcinoma: a cross-sectional study

OBJECTIVES

This study aimed to investigate the detection of Epstein-Barr virus (EBV) in oral squamous cell carcinoma (OSCC) and to verify the concordance of EBV-DNA frequency in subgingival sites and in the OSCC.

METHODS

A cross-sectional study with 30 OSCC patients, aged from 44 to 88 years old, was conducted. Samples were collected in subgingival sites and at the OSCC, then submitted to DNA isolation, qPCR, and genotyping. Descriptive statistic was performed to report the frequency of EBV-DNA in all samples, and McNemar test was applied to verify the concordance among the EBV-DNA frequency in both sites.

RESULTS

The individuals presented 62 years old in average, and the majority were male (66.6%). EBV-DNA was detected in 56.7% OSCC lesions. Among the subgroup of 19 dentate individuals, high concordance (73.7%) in both EBV-DNA detection and the absence in subgingival sites and OSCC was observed, and it was statistically significant (p < 0.05).

CONCLUSIONS

We report the notable occurrence of EBV-DNA in OSCC; also, the presence of EBV in periodontal sites may contribute to find it in OSCC, although the possible contribution of EBV in the OSCC remains to be investigated.

CLINICAL RELEVANCE

The identification of this easily accessible site of EBV latent infection may help to improve the patient's quality of life by maintenance of oral/periodontal health condition and preventing further possible disorders related to the virus, and also encourages new approaches for investigating EBV, periodontitis, and OSCC.

Periodontal Inflammation and Systemic Diseases: An Overview

Periodontitis is a common inflammatory disease of infectious origins that often evolves into a chronic condition. Aside from its importance as a stomatologic ailment, chronic periodontitis has gained relevance since it has been shown that it can develop into a systemic condition characterized by unresolved hyper-inflammation, disruption of the innate and adaptive immune system, dysbiosis of the oral, gut and other location's microbiota and other system-wide alterations that may cause, coexist or aggravate other health issues associated to elevated morbi-mortality. The relationships between the infectious, immune, inflammatory, and systemic features of periodontitis and its many related diseases are far from being fully understood and are indeed still debated. However, to date, a large body of evidence on the different biological, clinical, and policy-enabling sources of information, is available. The aim of the present work is to summarize many of these sources of information and contextualize them under a systemic inflammation framework that may set the basis to an integral vision, useful for basic, clinical, and therapeutic goals.

Fusobacterium nucleatum and oral cancer: a critical review

There is a growing level of interest in the potential role inflammation has on the initiation and progression of malignancy. Notable examples include Helicobacter pylori-mediated inflammation in gastric cancer and more recently Fusobacterium nucleatum-mediated inflammation in colorectal cancer. Fusobacterium nucleatum is a Gram-negative anaerobic bacterium that was first isolated from the oral cavity and identified as a periodontal pathogen. Biofilms on oral squamous cell carcinomas are enriched with anaerobic periodontal pathogens, including F. nucleatum, which has prompted hypotheses that this bacterium could contribute to oral cancer development. Recent studies have demonstrated that F. nucleatum can promote cancer by several mechanisms; activation of cell proliferation, promotion of cellular invasion, induction of chronic inflammation and immune evasion. This review provides an update on the association between F. nucleatum and oral carcinogenesis, and provides insights into the possible mechanisms underlying it.

Common Risk Factor Approach to Limit Noncommunicable Diseases and Periodontal Disease-The Molecular and Cellular Basis: A Narrative Review

Introduction

The link between periodontal disease and noncommunicable diseases (NCDs) has been the subject of major research over the past several years. The primary objective of this review is to understand the cellular and molecular components that link common risk factors (exposure) in adult patients (population) with periodontal disease and other NCDs (outcome). The secondary objective is to interpret from existing literature the possibility of identifying the molecular plausibility of the Common Risk Factor Approach (CRFA).

Materials and Methods

A literature search was performed in PubMed/MEDLINE, CINAHL, Web of Science, and Google Scholar for all published articles pertaining to the molecular and cellular basis of the risk factors between periodontal diseases and major NCDs. Data from all randomized and nonrandomized clinical trials, cross-sectional studies, case-control, cohort studies, literature, and systematic reviews were included.

Results

Periodontal pathogens, stress, obesity, smoking, and dietary factors are some of the common risk factors between periodontal disease and NCDs.

Conclusion

Understanding the molecular and cellular link of common risk factors between NCDs and periodontal disease would ensure the application of CRFA. The CRFA implies that controlling the risk factors associated with NCDs can have an incredible positive impact on regulating many chronic conditions, which would extend to periodontal health also.

A Plausible Proposition of CCL20-Related Mechanism in Fusobacterium nucleatum-Associated Oral Carcinogenesis

Objective: The objective of this prospective observational case–control study is to evaluate the prevalence of Fusobacterium nucleatum in the tissues of oral squamous cell carcinoma (OSCC). Reconnoitering the CCL20-related mechanism of carcinogenesis in Fusobacterium nucleatum-positive OSCC is another objective. Methodology: Tissues from 50 OSCC patients and 30 healthy oral tissues were collected. The prevalence of Fusobacterium nucleatum was evaluated in both tumour and healthy tissue by polymerase chain reaction. The immunohistochemistry of OSCC tissues was conducted to evaluate the difference in the expression of CCL20 between Fusobacterium nucleatum-positive and -negative OSCC tissues. Results: Fusobacterium nucleatum was significantly (p < 0.001) prevalent in OSCC tissues (74%), compared to healthy tissues (26%). No association of Fusobacterium nucleatum or CCL20 immuno-expression with any clinical or histopathological features of OSCC was observed. While the intensity of CCL20 immuno-expression did not differ (p = 0.053), the CCL20-positive cell population was significantly different (p = 0.034) between Fusobacterium nucleatum-positive and -negative OSCC. Conclusion: Fusobacterium nucleatum is possibly prevalent in oral cancer tissues in the Indian population. By using immunohistochemistry, this is the first study to propose that the carcinogenesis in Fusobacterium nucleatum-positive OSCC may be CCL20-related. The findings enrich the knowledge of mechanisms involved in Fusobacterium nucleatum-mediated oral carcinogenesis.

Lactiplantibacillus plantarum HNU082 inhibited the growth of Fusobacterium nucleatum and alleviated the inflammatory response introduced by F. nucleatum invasion

As a potential biomarker, there is increasing evidence showing that Fusobacterium nucleatum is positively correlated with the occurrence and development of colorectal cancer. Although antibiotics were expected to eliminate F. nucleatum, the side effects associated with gut microbiotal disorders have to be considered. Here, by performing shotgun metagenomic and transcriptome sequencing, we systematically evaluated the antagonistic effects of probiotic Lactiplantibacillus plantarum HNU082 (Lp082) on F. nucleatum in vivo and in vitro. The results showed that the F. nucleatum invasion significantly altered the host intestinal microbiome including the microbial composition, specific species, metabolic pathways and metabolites, as well as impacted the transcriptome of the intestinal epithelial cells. Moreover, the F. nucleatum invasion triggered inflammatory cytokines and inflammatory responses in the intestine but did not develop into colorectal cancer. Excitingly, the Lp082 intervention inhibited the growth of F. nucleatum both in vivo and in vitro and alleviated the inflammatory response introduced by F. nucleatum invasion. Further network-based mechanism exploration demonstrated that Lp082, which negatively correlated to F. nucleatum, maintained the intestinal microbiome homeostasis and prompted the production of beneficial metabolites in the intestine which decreased the expression of inflammatory cytokines in a mouse model. The present research suggested a feasible probiotic intervention strategy for F. nucleatum antagonism in vivo, which may prevent colorectal cancer at the early stage.

Periodontal Pathogens Promote Oral Squamous Cell Carcinoma by Regulating ATR and NLRP3 Inflammasome

Periodontitis is closely related to oral cancer, but the molecular mechanism of periodontal pathogens involved in the occurrence and development of oral cancer is still inconclusive. Here, we demonstrate that, in vitro, the cell proliferation ability and S phase cells of the periodontitis group (colonized by Porphyromonas gingivalis and Fusobacterium nucleatum, P+) significantly increased, but the G1 cells were obviously reduced. The animal models with an in situ oral squamous cell carcinoma (OSCC) and periodontitis-associated bacteria treatment were constructed, and micro-CT showed that the alveolar bone resorption of mice in the P+ group (75.3 ± 4.0 μm) increased by about 53% compared with that in the control group (48.8 ± 1.3 μm). The tumor mass and tumor growth rate in the P+ group were all higher than those in the blank control group. Hematoxylin-eosin (H&E) staining of isolated tumor tissues showed that large-scale flaky necrosis was found in the tumor tissue of the P+ group, with lots of damaged vascular profile and cell debris. Immunohistochemistry (IHC) of isolated tumor tissues showed that the expression of Ki67 and the positive rate of cyclin D1 were significantly higher in tumor tissues of the P+ group. The qRT-PCR results of the expression of inflammatory cytokines in oral cancer showed that periodontitis-associated bacteria significantly upregulated interleukin (IL)-6, tumor necrosis factor (TNF)-α, IL-18, apoptosis-associated speck-like protein containing a CARD (ASC) (up to six times), and caspase-1 (up to four times), but it downregulated nuclear factor (NF)-κB, NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3), and IL-1β (less than 0.5 times). In addition, the volume of spleen tissue and the number of CD4+ T cells, CD8+ T cells, and CD206+ macrophages in the P+ group increased significantly. IHC and Western blotting in tumor tissues showed that expression levels of γ-H2AX, p-ATR, RPA32, CHK1, and RAD51 were upregulated, and the phosphorylation level of CHK1 (p-chk1) was downregulated. Together, we identify that the periodontitis-related bacteria could promote tumor growth and proliferation, initiate the overexpressed NLRP3, and activate upstream signal molecules of ATR-CHK1. It is expected to develop a new molecular mechanism between periodontitis-related bacteria and OSCC.

The Heparanase Regulatory Network in Health and Disease

The extracellular matrix (ECM) is a structural framework that has many important physiological functions which include maintaining tissue structure and integrity, serving as a barrier to invading pathogens, and acting as a reservoir for bioactive molecules. This cellular scaffold is made up of various types of macromolecules including heparan sulfate proteoglycans (HSPGs). HSPGs comprise a protein core linked to the complex glycosaminoglycan heparan sulfate (HS), the remodeling of which is important for many physiological processes such as wound healing as well as pathological processes including cancer metastasis. Turnover of HS is tightly regulated by a single enzyme capable of cleaving HS side chains: heparanase. Heparanase upregulation has been identified in many inflammatory diseases including atherosclerosis, fibrosis, and cancer, where it has been shown to play multiple roles in processes such as epithelial-mesenchymal transition, angiogenesis, and cancer metastasis. Heparanase expression and activity are tightly regulated. Understanding the regulation of heparanase and its downstream targets is attractive for the development of treatments for these diseases. This review provides a comprehensive overview of the regulators of heparanase as well as the enzyme’s downstream gene and protein targets, and implications for the development of new therapeutic strategies.

Microbiome and cancer

The human microbiome constitutes a complex multikingdom community that symbiotically interacts with the host across multiple body sites. Host-microbiome interactions impact multiple physiological processes and a variety of multifactorial disease conditions. In the past decade, microbiome communities have been suggested to influence the development, progression, metastasis formation, and treatment response of multiple cancer types. While causal evidence of microbial impacts on cancer biology is only beginning to be unraveled, enhanced molecular understanding of such cancer-modulating interactions and impacts on cancer treatment are considered of major scientific importance and clinical relevance. In this review, we describe the molecular pathogenic mechanisms shared throughout microbial niches that contribute to the initiation and progression of cancer. We highlight advances, limitations, challenges, and prospects in understanding how the microbiome may causally impact cancer and its treatment responsiveness, and how microorganisms or their secreted bioactive metabolites may be potentially harnessed and targeted as precision cancer therapeutics.

The pathogenic mechanism of oral bacteria and treatment with inhibitors

OBJECTIVES

The objective of this study was to introduce the evidence obtained through extensive research that periodontitis increases risk of many systemic diseases.

METHOD

Analysis of some oral bacteria (P. gingivalis, T. denticola, T. forsythia, A. actinomycetemcomitans, and F. nucleatum) and its related treatments and mediators by the specific methods (western blot, ELISA, etc).

RESULTS

This article reviews in detail the evidence obtained through extensive research that periodontitis increases risk of many systemic diseases, including cardiovascular disease, rheumatoid arthritis, and Alzheimer's disease. These diseases are known to be associated with some certain specific gram-negative bacteria as periodontal pathogens, which induce inflammation and related diseases through TLR receptors, kinases, transcriptional factors and other cytokines. We also reviewed the latest research for inhibitors against inflammation and related diseases that have potential to be further applied clinically. In addition, based on a large amount of research evidence, we draw two tables about the mechanism of disease caused by periodontal bacteria, so that readers can easily search and analyze these research results.

DISCUSSION

This review details how the periodontal bacteria and their virulence factors can trigger host immune defense and induce many systemic diseases via inflammation and invasion. This Review also addressed the latest research around inhibitors against inflammation.

The Clinical Potential of Oral Microbiota as a Screening Tool for Oral Squamous Cell Carcinomas

Introduction

The oral squamous cell carcinoma (OSCC) is detrimental to patients’ physical and mental health. The prognosis of OSCC depends on the early diagnosis of OSCC in large populations.

Objectives

Here, the present study aimed to develop an early diagnostic model based on the relationship between OSCC and oral microbiota.

Methods

Overall, 164 samples were collected from 47 OSCC patients and 48 healthy individuals as controls, including saliva, subgingival plaque, the tumor surface, the control side (healthy mucosa), and tumor tissue. Based on 16S rDNA sequencing, data from all the five sites, and salivary samples only, two machine learning models were developed to diagnose OSCC.

Results

The average diagnostic accuracy rates of five sites and saliva were 98.17% and 95.70%, respectively. Cross-validations showed estimated external prediction accuracies of 96.67% and 93.58%, respectively. The false-negative rate was 0%. Besides, it was shown that OSCC could be diagnosed on any one of the five sites. In this model, Actinobacteria, Fusobacterium, Moraxella, Bacillus, and Veillonella species exhibited strong correlations with OSCC.

Conclusion

This study provided a noninvasive and inexpensive way to diagnose malignancy based on oral microbiota without radiation. Applying machine learning methods in microbiota data to diagnose OSCC constitutes an example of a microbial assistant diagnostic model for other malignancies.

Leukoplakia in the Oral Cavity and Oral Microbiota: A Comprehensive Review

Simple Summary

The aim of this narrative review is to better understand the role of the oral microbiota in oral cavity leukoplakia. We provide a comprehensive review, exhaustively summarizing the steps taken in this field.

Abstract

We reviewed the current published literature on the impact of oral microbiota on oral cavity leukoplakia (OLK), aiming at clarifying its role in disease transformation. The analysis unveiled that bacterial richness and diversity in the oral cavity tend to be decreased in OLK compared to healthy controls, with a reduction in the prevalent commensals, such as Streptococci, and elevation of anaerobes. Moreover, Fusobacterium nucleatum, Porphyromonas gingivalis and Prevotella intermedia are recurrent findings, and they already have been linked to periodontal disease. These microbial community changes may also represent a marker for the transition from OLK to oral squamous cell carcinoma. Unfortunately, the reviewed studies present several limitations, making an objective comparison difficult. To overcome these biases, longitudinal studies are necessary.

The role of microbiome in pancreatic cancer

Recent studies of the human microbiome have offered new insights into how the microbiome can impact cancer development and treatment. Specifically, in pancreatic ductal adenocarcinoma (PDAC), the microbiota has been shown to modulate PDAC risk, contribute to tumorigenesis, impact the tumor microenvironment, and alter treatment response. These findings provide rationale for further investigations into leveraging the microbiome to develop new strategies to diagnose and treat PDAC patients. There is growing evidence that microbiome analyses have the potential to become easily performed, non-invasive diagnostic, prognostic, and predictive biomarkers in pancreatic cancer. More excitingly, there is now emerging interest in developing interventions based on the modulation of microbiota. Fecal microbiota transplantation, probiotics, dietary changes, and antibiotics are all potential strategies to augment the efficacy of current therapeutics and reduce toxicities. While there are still challenges to overcome, this is a rapidly growing field that holds promise for translation into clinical practice and provides a new approach to improving patient outcomes.

The Role of Periodontopathogens and Oral Microbiome in the Progression of Oral Cancer. A Review

Chronic periodontal disease and oral bacteria dysbiosis can lead to the accumulation of genetic mutations that eventually stimulate Oral Squamous Cell Cancer (OSCC). The annual incidence of OSCC is increasing significantly, and almost half of the cases are diagnosed in an advanced stage. Worldwide there are more than 380,000 new cases diagnosed every year, and a topic of extensive research in the last few years is the alteration of oral bacteria, their compositional changes and microbiome. This review aims to establish the relationship between bacterial dysbiosis and OSCC. Several bacteria implicated in periodontal disease, including Fusobacterium nucleatum, Porphyromonas gingivalis, Prevotella intermedia, and some Streptococcus species, promote angiogenesis, cell proliferation, and alteration in the host defense process; these same bacteria have been present in different stages of OSCC. Our review showed that genes involved in bacterial chemotaxis, the lipopolysaccharide (LPS) of the cell wall membrane of gram negatives bacteria, were significantly increased in patients with OSCC. Additionally, some bacterial diversity, particularly with Firmicutes, and Actinobacteria species, has been identified in pre-cancerous stage samples. This review suggests the importance of an early diagnosis and more comprehensive periodontal therapy for patients by the dental care professional.

Commensal microbiota in the digestive tract: a review of its roles in carcinogenesis and radiotherapy

The human microflora is a complex ecosystem composed of diverse microorganisms mainly distributed in the epidermal and mucosal habitats of the entire body, including the mouth, lung, intestines, skin, and vagina. These microbial communities are involved in many essential functions, such as metabolism, immunity, host nutrition, and diseases. Recent studies have focused on the microbiota associated with cancers, particularly the oral and intestinal microbiota. Radiotherapy, the most effective cytotoxic modality available for solid tumors, contributes to the treatment of cancer patients. Mounting evidence supports that the microbiota plays pivotal roles in the efficacy and prognosis of tumor radiotherapy. Here, we review current research on the microbiota and cancer development, and describe knowledge gaps in the study of radiotherapy and the microbiota. Better understanding of the effects of the microbiome in tumorigenesis and radiotherapy will shed light on future novel prevention and treatment strategies based on modulating the microbiome in cancer patients.

Distinct microbial communities colonize tonsillar squamous cell carcinoma

Squamous cell carcinoma of the tonsil is one of the most frequent cancers of the oropharynx. The escalating rate of tonsil cancer during the last decades is associated with the increase of high risk-human papilloma virus (HR-HPV) infections. While the microbiome in oropharyngeal malignant diseases has been characterized to some extent, the microbial colonization of HR-HPV-associated tonsil cancer remains largely unknown. Using 16S rRNA gene amplicon sequencing, we have characterized the microbiome of human palatine tonsil crypts in patients suffering from HR-HPV-associated tonsil cancer in comparison to a control cohort of adult sleep apnea patients. We found an increased abundance of the phyla Firmicutes and Actinobacteria in tumor patients, whereas the abundance of Spirochetes and Synergistetes was significantly higher in the control cohort. Furthermore, the accumulation of several genera such as Veillonella, Streptococcus and Prevotella_7 in tonsillar crypts was associated with tonsil cancer. In contrast, Fusobacterium, Prevotella and Treponema_2 were enriched in sleep apnea patients. Machine learning-based bacterial species analysis indicated that a particular bacterial composition in tonsillar crypts is tumor-predictive. Species-specific PCR-based validation in extended patient cohorts confirmed that differential abundance of Filifactor alocis and Prevotella melaninogenica is a distinct trait of tonsil cancer. This study shows that tonsil cancer patients harbor a characteristic microbiome in the crypt environment that differs from the microbiome of sleep apnea patients on all phylogenetic levels. Moreover, our analysis indicates that profiling of microbial communities in distinct tonsillar niches provides microbiome-based avenues for the diagnosis of tonsil cancer.

The Role of the Oral Microbiota in the Etiopathogenesis of Oral Squamous Cell Carcinoma

Dysbiosis in the oral environment may play a role in the etiopathogenesis of oral squamous cell carcinoma (OSCC). This review aims to summarize the current knowledge about the association of oral microbiota with OSCC and to describe possible etiopathogenetic mechanisms involved in processes of OSCC development and progression. Association studies included in this review were designed as case–control/case studies, analyzing the bacteriome, mycobiome, and virome from saliva, oral rinses, oral mucosal swabs, or oral mucosal tissue samples (deep and superficial) and comparing the results in healthy individuals to those with OSCC and/or with premalignant lesions. Changes in relative abundances of specific bacteria (e.g., Porphyromonas gingivalis, Fusobacterium nucleatum, Streptococcus sp.) and fungi (especially Candida sp.) were associated with OSCC. Viruses can also play a role; while the results of studies investigating the role of human papillomavirus in OSCC development are controversial, Epstein–Barr virus was positively correlated with OSCC. The oral microbiota has been linked to tumorigenesis through a variety of mechanisms, including the stimulation of cell proliferation, tumor invasiveness, angiogenesis, inhibition of cell apoptosis, induction of chronic inflammation, or production of oncometabolites. We also advocate for the necessity of performing a complex analysis of the microbiome in further studies and of standardizing the sampling procedures by establishing guidelines to support future meta-analyses.

Association of Microbiome with Oral Squamous Cell Carcinoma: A Systematic Review of the Metagenomic Studies

The past decade has witnessed a surge in epidemiological studies that have explored the relationship between the oral microbiome and oral cancer. Owing to the diversity of the published data, a comprehensive systematic overview of the currently available evidence is critical. This review summarises the current evidence on the metagenomic studies on the oral microbiome in oral cancer. A systematic search was conducted in Medline and Embase databases to identify original studies examining the differences in the oral microbiome of oral cancer cases and controls. A total of twenty-six studies were identified that reported differences in microbial abundance between oral squamous cell carcinoma (OSCC) and controls. Although almost all the studies identified microbial dysbiosis to be associated with oral cancer, the detailed qualitative analysis did not reveal the presence/abundance of any individual bacteria or a consortium to be consistently enriched in OSCC samples across the studies. Interestingly, few studies reported a surge of periodontopathogenic taxa, especially Fusobacteria, whereas others demonstrated a depletion of commensal taxa Streptococci. Considerable heterogeneity could be identified in the parameters used for designing the studies as well as reporting the microbial data. If microbiome data needs to be translated in the future, to complement the clinical parameters for diagnosis and prognosis of oral cancer, further studies with the integration of clinical variables, adequate statistical power, reproducible methods, and models are required.

Role of microbial dysbiosis in carcinogenesis & cancer therapies

The human body supports a heterogeneous population of microorganisms. Every microorganism has the ability to contribute to the unique microenvironment around it. The aim of this review is to discuss the changes in the microbial population and their relative abundance across different ecosystems of the human body, the interactions within the microbial communities, metabolites they secrete to their external environment, their immunomodulatory functions, their signal transduction pathways and how these respond to environmental stimuli such as various diets, alcohol and drug consumption, smoking and finally suggest new therapeutic approaches. The microbiota may leads to cancer through inflammation mediated mechanisms which modulate immune responses, or produce carcinogenic metabolites and genotoxins, or deregulate cell proliferative signalling pathways. The identification of these molecular mechanisms in carcinogenesis may lead to better treatment strategies. In this review we have tried to explore the changes in microbial composition between cancer and normal tissues and what molecular mechanisms provide a connecting link between microbial dysbiosis and cancer.

Oral microbial dysbiosis and its performance in predicting oral cancer

Dysbiosis of oral microbiome may dictate the progression of oral squamous cell carcinoma (OSCC). Yet, the composition of oral microbiome fluctuates by saliva and distinct sites of oral cavity and is affected by risky behaviors (smoking, drinking and betel quid chewing) and individuals' oral health condition. To characterize the disturbances in the oral microbial population mainly due to oral tumorigenicity, we profiled the bacteria within the surface of OSCC lesion and its contralateral normal tissue from discovery (n = 74) and validation (n = 42) cohorts of male patients with cancers of the buccal mucosa. Significant alterations in the bacterial diversity and relative abundance of specific oral microbiota (most profoundly, an enrichment for genus Fusobacterium and the loss of genus Streptococcus in the tumor sites) were identified. Functional prediction of oral microbiome shown that microbial genes related to the metabolism of terpenoids and polyketides were differentially enriched between the control and tumor groups, indicating a functional role of oral microbiome in formulating a tumor microenvironment via attenuated biosynthesis of secondary metabolites with anti-cancer effects. Furthermore, the vast majority of microbial signatures detected in the discovery cohort was generalized well to the independent validation cohort, and the clinical validity of these OSCC-associated microbes was observed and successfully replicated. Overall, our analyses reveal signatures (a profusion of Fusobacterium nucleatum CTI-2 and a decrease in Streptococcus pneumoniae) and functions (decreased production of tumor-suppressive metabolites) of oral microbiota related to oral cancer.

Comparative analysis of bacterial content, levels of lipopolysaccharides and lipoteichoic acid in symptomatic and asymptomatic endodontic infections at different stages of endodontic treatment

OBJECTIVES

This study aimed to detect the presence of specific bacteria and to evaluate the levels of lipopolysaccharides (LPS) and lipoteichoic acid (LTA) in symptomatic necrotic root canals associated with acute apical abscess (symptomatic group - GI). It also aimed to compare the findings with those presented by asymptomatic necrotic root canals (asymptomatic group - GII) in the different stages of the endodontic treatment.

MATERIALS AND METHODS

Microbiological samples were collected from 20 root canals, including purulent collection from acute apical abscesses, before and after chemo-mechanical preparation (CMP) preparation (CMP) with chlorhexidine gel 2% and after 30 days of intracanal medication (ICM) with (Ca[OH]₂) + chlorhexidine. The culture method was used to evaluate the efficacy of CMP and ICM. Nested PCR was used to detect the presence of 17 specific bacteria. Levels of LPS were measured by using limulus amebocyte lysate, whereas enzyme-linked immunosorbent assay was used for the quantification of LTA.

RESULTS

CMP was effective in reducing the microbial load in both groups (P < 0.05). LPS levels were higher in GI than in GII (P < 0.05). There was a significant reduction in the LPS levels after CMP and ICM (P < 0.05) in GI and GII. LTA levels were significantly reduced in GI after ICM and in GII after CMP and ICM (both P < 0.05). Fusobacterium nucleatum and Enterococcus faecalis were frequently identified in both groups, alone or in combination with each other.

CONCLUSION

Different species were detected in all stages of the endodontic treatment. CMP was able to reduce bacterial content and the levels of LPS, but not of LTA in the symptomatic group. High levels of LPS were correlated with spontaneous pain and pain to percussion in the symptomatic group.

CLINICAL RELEVANCE

This clinical study showed that chemo-mechanical preparation was able to reduce bacterial load and levels of LPS, but not of LTA in the symptomatic group. Elevated levels of LPS were correlated with the presence of symptomatology.

Regulation of Bone Cell Differentiation and Activation by Microbe-Associated Molecular Patterns

Gut microbiota has emerged as an important regulator of bone homeostasis. In particular, the modulation of innate immunity and bone homeostasis is mediated through the interaction between microbe-associated molecular patterns (MAMPs) and the host pattern recognition receptors including Toll-like receptors and nucleotide-binding oligomerization domains. Pathogenic bacteria such as Porphyromonas gingivalis and Staphylococcus aureus tend to induce bone destruction and cause various inflammatory bone diseases including periodontal diseases, osteomyelitis, and septic arthritis. On the other hand, probiotic bacteria such as Lactobacillus and Bifidobacterium species can prevent bone loss. In addition, bacterial metabolites and various secretory molecules such as short chain fatty acids and cyclic nucleotides can also affect bone homeostasis. This review focuses on the regulation of osteoclast and osteoblast by MAMPs including cell wall components and secretory microbial molecules under in vitro and in vivo conditions. MAMPs could be used as potential molecular targets for treating bone-related diseases such as osteoporosis and periodontal diseases.

Toothbrushing frequency and gastric and upper aerodigestive tract cancer risk: A meta-analysis

OBJECTIVE

Results of epidemiological studies evaluating the association between toothbrushing and gastric and upper aerodigestive tract (UADT) cancer risk showed inconsistent results. The purpose of this study was to evaluate the association between toothbrushing and gastric and UADT cancer risk and quantify the dose-response association between them.

METHODS

We searched the PubMed, EMBASE and Cochrane Library databases to identify relevant studies on toothbrushing and gastric and UADT cancer risk. Statistical analyses were performed using STATA 12.0 software.

RESULTS

A total of 30 studies of involving 1 194 017 participants met eligibility criteria and were included in the meta-analysis. Meta-analysis using a random-effect model showed that the high frequency of toothbrushing was associated with significantly reduced risk of gastric and UADT cancers (OR: 0.55, 95% CI 0.46-0.64, P < .05). Our dose-response analysis presented that every increased toothbrushing per day might reduce oral cavity cancer risk by 6%, pharyngeal cancer risk by 11%, laryngeal cancer risk by 3%, oesophageal cancer risk by 6% and gastric cancer risk by 4%.

CONCLUSIONS

This meta-analysis suggested the negative relationship between frequency of toothbrushing and risk of gastric and UADT cancers. Toothbrushing may be a protective factor for gastric and UADT cancers. However, this association must be further validated through large prospective studies.

The dysbiosis signature of Fusobacterium nucleatum in colorectal cancer-cause or consequences? A systematic review

Colorectal cancer (CRC) is the third most common cause of cancer globally and the fourth attributable cause of mortality and morbidity due to cancer. An emerging factor contributing to CRC is the gut microbiota and the cellular changes associated with it. Further insights on this may help in the prevention, diagnosis and new therapeutic approaches to colorectal cancer. In most cases of CRC, genetic factors appear to contribute less to its aetiology than environmental and epigenetic factors; therefore, it may be important to investigate these environmental factors, their effects, and the mechanisms that may contribute to this cancer. The gut microbiota has recently been highlighted as a potential risk factor that may affect the structural components of the tumor microenvironment, as well as free radical and enzymatic metabolites directly, or indirectly. Many studies have reported changes in the gut microbiota of patients with colorectal cancer. What is controversial is whether the cancer is the cause or consequence of the change in the microbiota. There is strong evidence supporting both possibilities. The presence of Fusobacterium nucleatum in human colorectal specimens has been demonstrated by RNA-sequencing. F. nucleatum has been shown to express high levels of virulence factors such as FadA, Fap2 and MORN2 proteins. Our review of the published data suggest that F. nucleatum may be a prognostic biomarker of CRC risk, and hence raises the potential of antibiotic treatment of F. nucleatum for the prevention of CRC.

Determination of the Role of Fusobacterium Nucleatum in the Pathogenesis in and Out the Mouth

INTRODUCTION

One of the most important types of microorganisms in the oral cavity in both healthy and non-healthy individuals is Fusobacterium nucleatum. Although present as a normal resident in the oral cavity, this Gram-negative pathogen is dominant in periodontal disease and it is involved in many invasive infections in the population, acute and chronic inflammatory conditions, as well as many adverse events with a fatal outcome.

AIM

To determine the role of F. nucleatum in the development of polymicrobial biofilms thus pathogenic changes in and out of the oral media.

MATERIAL AND METHOD

A systematic review of the literature concerning the determination and role of F. nucleatum through available clinical trials, literature reviews, original research and articles published electronically at Pub Med and Google Scholar.

CONCLUSION

The presence of Fusobacterium nucleatum is commonly associated with the health status of individuals. These anaerobic bacteria plays a key role in oral pathological conditions and has been detected in many systemic disorders causing complex pathogenethic changes probably due to binding ability to various cells thus several virulence mechanisms. Most common diseases and conditions in the oral cavity associated with F.nucleatum are gingivitis (G), chronic periodontitis (CH), aggressive periodontitis (AgP), endo-periodental infections (E-P), chronic apical periodontitis (PCHA). The bacterium has been identified and detected in many systemic disorders such as coronary heart disease (CVD) pathological pregnancy (P); polycystic ovary syndrome (PCOS), high-risk pregnancy (HRP), colorectal cancer (CRC); pre-eclampsia (PE); rheumatoid arthritis (RA); osteoarthritis (OA).

Maintaining homeostatic control of periodontal epithelial tissue

Years of coevolution with resident microbes has made them an essential component of health. Yet, little is known about oral commensal bacteria's contribution to and role in the maintenance of oral health and homeostasis. Commensal bacteria are speculated to play a host protective role in the maintenance of health. In this review, we describe and provide examples of the coordinate regulation that occurs between oral commensal bacteria and the host innate immune response to modulate and maintain oral homeostasis.

Oral microbiota and Helicobacter pylori in gastric carcinogenesis: what do we know and where next?

Gastric cancer (GC) is one of the most common malignancies causing death worldwide, and Helicobacter pylori is a powerful inducer of precancerous lesions and GC. The oral microbiota is a complex ecosystem and is responsible for maintaining homeostasis, modulating the immune system, and resisting pathogens. It has been proposed that the gastric microbiota of oral origin is involved in the development and progression of GC. Nevertheless, the causal relationship between oral microbiota and GC and the role of H. pylori in this relationship is still controversial. This study was set to review the investigations done on oral microbiota and analyze various lines of evidence regarding the role of oral microbiota in GC, to date. Also, we discussed the interaction and relationship between H. pylori and oral microbiota in GC and the current understanding with regard to the underlying mechanisms of oral microbiota in carcinogenesis. More importantly, detecting the patterns of interaction between the oral cavity microbiota and H. pylori may render new clues for the diagnosis or screening of cancer. Integration of oral microbiota and H. pylori might manifest a potential method for the assessment of GC risk. Hence it needs to be specified the patterns of bacterial transmission from the oral cavity to the stomach and their interaction. Further evidence on the mechanisms underlying the oral microbiota communities and how they trigger GC may contribute to the identification of new prevention methods for GC. We may then modulate the oral microbiota by intervening with oral-gastric bacterial transmission or controlling certain bacteria in the oral cavity.

Proto-Oncogenes and Cell Cycle Gene Expression in Normal and Neoplastic Oral Epithelial Cells Stimulated With Soluble Factors From Single and Dual Biofilms of Candida albicans and Staphylococcus aureus

This study was aimed at analyzing proto-oncogenic signaling pathway activation in normal oral keratinocytes (NOK-si) and neoplastic cell lines (SCC 25 and Detroit 562) stimulated with metabolites (soluble factors) from single and dual biofilms of Candida albicans and Staphylococcus aureus. Soluble factors (SF) from early (16-h) and mature (36-h) biofilms of C. albicans and S. aureus were collected and incubated with cell cultures, which were subsequently evaluated using gene expression via RT-qPCR, cell viability via AlamarBlue^TM, and flow cytometry cell cycle analysis. In general, exposure to the SF of early and mature biofilms from C. albicans and dual species caused a major reduction in NOK-si cell viability and enhanced the sub G0 phase. This led to a decrease in gene expression. However, in this cell line, SF of S. aureus biofilms upregulated the CDKN1A gene followed by the maintenance of cell viability and a significant increase in the G2/M population. For tumor cells, SCC 25 and Detroit 562, the stimuli of SF biofilms upregulated oncogenes such as hRAS and mTOR, as well as Bcl-2 and CDKN1A. SCC 25 and Detroit 562 cells could survive even after 24 h of stimuli from both SF (early and mature). This occurred without significant changes taking place in the cell cycle progression for SCC 25, and with a significant tendency to increase the G2/M phase for Detroit 562. These results point to the fact that metabolites from prevalent clinical fungal and bacterial biofilms, C. albicans and S. aureus, can disrupt the homeostasis of normal and neoplastic oral epithelial cells. This changes proto-oncogenes’ expression, specifically PI3KCA, hRAS, mTOR, BRAF, and cell cycle genes CDKN1A and Bcl-2, thus causing a disturbance in cell viability, survival, and the cell cycle profile.

Independent association of marijuana use and poor oral hygiene with HPV-negative but not HPV-positive head and neck squamous cell carcinomas

BACKGROUND

Sexual behavior is associated with human papillomavirus (HPV)-positive head and neck cancer, whereas tobacco and alcohol use are associated with HPV-negative cancer. A case-control study was designed to investigate additional demographic and behavioral factors independently associated with these distinct oral cancers.

METHODS

From 2011 to 2014, 249 newly diagnosed oral cavity and oropharyngeal squamous cell carcinoma (OSCC) cases were matched (1:2) on age, gender, and self-identified race to 498 controls without a cancer history attending the outpatient otolaryngology clinic at The Ohio State University in Columbus. Cases were stratified by detection of high-risk HPV DNA and RNA in tumors. Demographic and behavioral data were collected using an audio computer-assisted self-interview, and associations with HPV-positive versus HPV-negative OSCCs were investigated by use of univariable and multivariable conditional logistic regression models.

RESULTS

After adjustment for oral sexual behavior, the odds of HPV-positive cancer decreased with the patient's years of education. Annual income, tobacco smoking, alcohol drinking, marijuana smoking, and poor oral hygiene were not associated with HPV-positive OSCC. In contrast, the odds of HPV-negative OSCC increased independently with decreased annual income, decreased with a high number of marijuana hit-years, and increased with fewer than annual dental visits after adjustment for lifetime tobacco and alcohol use. Sexual behavior and education were not associated with HPV-negative OSCC.

CONCLUSIONS

The distinct risk-factor profiles for HPV-positive and HPV-negative OSCC are confirmed and extended in this case-control study, thus supporting 2 principal etiological pathways for OSCC development.

LAY SUMMARY

Sexually acquired human papillomavirus (HPV) infection is an established cause of tonsil and base of tongue cancers. This study compared and contrasted risk factors for HPV-positive and HPV-negative oral cancers. Low number of years of education and sexual behavior are associated with HPV-positive cancer. In contrast, low annual income, infrequent dental visits, and tobacco and alcohol use are associated with HPV-negative cancers. Long-term marijuana use appears protective for HPV-negative cancer. Public health efforts to address these modifiable risk factors may prevent oral cancer.

Salivary CCL20 Level as a Biomarker for Oral Squamous Cell Carcinoma

BACKGROUND/AIM

This study investigated the utility of C-C motif chemokine ligand 20 (CCL20) expression in saliva as a biomarker for oral squamous cell carcinoma (OSCC) and also examined the associated microbiome.

MATERIALS AND METHODS

The study group included patients with OSCC or oral potentially malignant disorder (OPMD), and healthy volunteers (HVs). microarray and qRT-PCR were used to compare salivary CCL20 expression levels among groups. Data on CCL20 levels in oral cancer tissues and normal tissues were retrieved from a public database and examined. Furthermore, next-generation sequencing was used to investigate the salivary microbiome.

RESULTS

A significant increase in the expression level of CCL20 was observed in both OSCC tissues and saliva from patients with oral cancer. Fusobacterium was identified as the predominant bacteria in OSCC and correlated with CCL20 expression level. OSCC screening based on salivary CCL20 expression enabled successful differentiation between patients with OSCC and HVs.

CONCLUSION

CCL20 expression may be a useful biomarker for OSCC.

TNFα expression by Porphyromonas gingivalis-stimulated macrophages relies on Sirt1 cleavage

OBJECTIVE

Periodontitis is one the most common chronic inflammatory conditions, resulting in destruction of tooth-supporting tissues and leading to tooth loss. Porphyromonas gingivalis activates host macrophages to secrete pro-inflammatory cytokines and elicit tissue damage, in part by inducing NF-kappa-B transactivation. Since NFκB transactivation is negatively regulated by the Nicotinamide adenine dinucleotide (NAD)-dependent deacetylase enzyme Sirt1, we sought to assess if RAW264.7 macrophages exposed to P. gingivalis demonstrate impaired Sirt1 activity, to ultimately induce a pro-inflammatory response.

METHODS

RAW264.7 macrophages were incubated with heat- killed P. gingivalis for 2, 4, 8, and 24 h. Stimulated RAW264.7 were assessed for TNFα expression via PCR, ELISA, and ChIP analysis. Following the activation of RAW264.7 macrophages, immunoblot analysis was executed to detect modifications in Sirt1 and the NFκB subunit RelA that is essential for NFκB transcriptional activity.

RESULTS

TNFα expression was elevated 4 h after exposure to P. gingivalis. ChIP confirmed that RelA was enriched in the mouse TNFα promoter 4 h following stimulation, which correlated with the increased TNFα mRNA levels. Preceding TNFα expression, we detected Phosphoserine 536 and acetylated lysine 310 of RelA after 2 hours exposure with P. gingivalis. Moreover, reduced Sirt1 activity was associated with its cleavage in RAW264.7 protein extracts, after 2 hours of P. gingivalis exposure. Blocking TLR2/4 signaling prevented Sirt1 cleavage, loss of deacetylase activity, and TNFα secretion, while co-administering CA074Me (a cathepsin B inhibitor) with P. gingivalis reduced RelA promoter enrichment, resulting in impaired TNFα expression.

CONCLUSIONS

Together, the results suggest that P. gingivalis induces TNFα expression, at least in part, by enhancing cleavage of Sirt1 via a TLR-dependent signaling circuit.

LncRNA LTSCCAT promotes tongue squamous cell carcinoma metastasis via targeting the miR-103a-2-5p/SMYD3/TWIST1 axis

Abnormal expression of long-noncoding RNA is involved in the tumorigenesis and progression of various cancers, but the potential molecular regulatory mechanisms are unclear. Microbial flora and chronic inflammation, such as periodontitis, which is associated with oral cancer, affect the occurrence and progression of tumors. Accordingly, we stimulated the tongue squamous cell carcinoma (TSCC) cell lines CAL27 and SCC15 with a low concentration of lipopolysaccharide (LPS) from Porphyromonas gingivalis (P.g) for 6 days and then performed LncRNA sequencing on P.g-LPS-treated CAL27 cells and untreated CAL27 cells. LTSCCAT was upregulated in P.g-LPS-treated CAL27 cells compared with untreated CAL27 cells. LTSCCAT induced epithelial–mesenchymal transition and promoted the invasion and metastasis of TSCC in vitro and in vivo. LncRNA LTSCCAT was upregulated in TSCC patients with periodontitis and was correlated with metastasis and poor prognosis. We predicted through an online database and confirmed by dual-luciferase reporter assays that LTSCCAT is a competitive endogenous RNA for the regulation of miR-103a-2-5p. Another dual-luciferase reporter assay confirmed that miR-103a-2-5p has a binding site at the 3′-UTR of the histone methylation transferase SMYD3 and inhibits its translation. Chromatin immunoprecipitation experiments demonstrated that SMYD3 binds directly to the promoter region of TWIST1 and promotes its transcription, which is related to H3K4 trimethylation. The effect of pcDNA/LTSCCAT on expression was attenuated by miR-103a-2-5p mimics. The RF and SVM classifier predicts that LTSCCAT can bind to SMYD3, whereas the RNA immunoprecipitation (RIP) assay confirms that it cannot. In addition, we predicted the combination of LTSCCAT and SMYD3 through software, but the RIP assay confirmed that LTSCCAT could not be combined with SMYD3. For the first time, we showed that periodontitis promotes the invasion and metastasis of TSCC and clarified the molecular mechanism of LTSCCAT to promote invasion and metastasis of TSCC, providing a potential therapeutic target for clinical treatment of TSCC.

Looking beyond the smokescreen: can the oral microbiome be a tool or target in the management of tobacco-associated oral cancer?

A wide range of microbes inhabit the oral cavity, and bacterial and fungal communities most often exist as structured communities or biofilms. The use of tobacco alters the structure of the oral microbiome, including that of potentially malignant lesions, and the altered oral microbiome influences key microenvironmental changes such as chronic inflammation, secretion of carcinogenic toxins, cellular and tissue remodelling and suppression of apoptosis. Given this, it is clear that the bacterial and fungal biofilms in potentially malignant states are likely not passive entities, but could play a critical role in shaping potential malignant and carcinogenic conditions. This holds potential towards leveraging the oral microbiome for the management of tobacco-associated potentially malignant lesions and oral cancer. Here, we explore this line of investigation by reviewing the effects of tobacco in shaping the oral microbiome, and analyse the available evidence in the light of the microbiome of oral potentially malignant and cancerous lesions, and the role of dysbiosis in carcinogenesis. Finally, we discuss possible interventions and approaches using which the oral microbiome could be leveraged towards precision-based oral cancer therapeutics.

Oral microbiota and vitamin D impact on oropharyngeal squamous cell carcinogenesis: a narrative literature review

An emerging body of research is revealing the microbiota pivotal involvement in determining the health or disease state of several human niches, and that of vitamin D also in extra-skeletal regions. Nevertheless, much of the oral microbiota and vitamin D reciprocal impact in oropharyngeal squamous cell carcinogenesis (OPSCC) is still mostly unknown. On this premise, starting from an in-depth scientific bibliographic analysis, this narrative literature review aims to show a detailed view of the state of the art on their contribution in the pathogenesis of this cancer type. Significant differences in the oral microbiota species quantity and quality have been detected in OPSCC-affected patients; in particular, mainly high-risk human papillomaviruses (HR-HPVs), Fusobacterium nucleatum, Porphyromonas gingivalis, Pseudomonas aeruginosa, and Candida spp. seem to be highly represented. Vitamin D prevents and fights infections promoted by the above identified pathogens, thus confirming its homeostatic function on the microbiota balance. However, its antimicrobial and antitumoral actions, well-described for the gut, have not been fully documented for the oropharynx yet. Deeper investigations of the mechanisms that link vitamin D levels, oral microbial diversity and inflammatory processes will lead to a better definition of OPSCC risk factors for the optimization of specific prevention and treatment strategies.

Differences in the bacteriome of swab, saliva, and tissue biopsies in oral cancer

Microbial dysbiosis has been implicated in the pathogenesis of oral cancer. We analyzed the compositional and metabolic profile of the bacteriome in three specific niches in oral cancer patients along with controls using 16SrRNA sequencing (Illumina Miseq) and DADA2 software. We found major differences between patients and control subjects. Bacterial communities associated with the tumor surface and deep paired tumor tissue differed significantly. Tumor surfaces carried elevated abundances of taxa belonging to genera Porphyromonas, Enterobacteriae, Neisseria, Streptococcus and Fusobacteria, whereas Prevotella, Treponema, Sphingomonas, Meiothermus and Mycoplasma genera were significantly more abundant in deep tissue. The most abundant microbial metabolic pathways were those related to fatty-acid biosynthesis, carbon metabolism and amino-acid metabolism on the tumor surface: carbohydrate metabolism and organic polymer degradation were elevated in tumor tissues. The bacteriome of saliva from patients with oral cancer differed significantly from paired tumor tissue in terms of community structure, however remained similar at taxonomic and metabolic levels except for elevated abundances of Streptococcus, Lactobacillus and Bacteroides, and acetoin-biosynthesis, respectively. These shifts to a pro-inflammatory profile are consistent with other studies suggesting oncogenic properties. Importantly, selection of the principal source of microbial DNA is key to ensure reliable, reproducible and comparable results in microbiome studies.

Fusobacteria modulate oral carcinogenesis and promote cancer progression

Background: Evidence suggest periodontal bacterial infection can contribute to oral cancer initiation and progression.

Aim: To investigate the effects of periodontal bacteria on oral cancer cell behavior using a cell-based system and a mouse carcinogenesis model.

Methods: Oral cancer cell lines were polyinfected with four periodontal bacteria. Cytokine levels and relative changes in oncogene mRNA expression were determined post-infection. Oral tumours in mice induced by 4-nitroquinoline-1-oxide (4NQO) were compared with and without administrating periodontal bacteria.

Results: Polyinfected oral cancer cells had upregulated MMP1, MMP9, and IL-8. The expression of cell survival markers MYC, JAK1, and STAT3 and epithelial-mesenchymal transition markers ZEB1 and TGF-β were also significantly elevated. Monoinfections showed F. nucleatum alone had comparable or greater effects than the four bacteria together. Fusobacterial culture supernatant, primarily LPS, was sufficient to induce IL-8 secretion, demonstrating that direct contact of live Fusobacteria with cancer cells might not be required to exert changes in cancer cell behaviour. In the 4NQO-induced oral tumour model, mice infected with bacteria developed significantly larger and more numerous lesions compared to those not infected.

Conclusion: This study demonstrated that Fusobacteria could potentially enhance cancer cell invasiveness, survival, and EMT when presented in the oral tumour microenvironment.

Abbreviations: 4NQO, 4-nitroquinoline-1-oxide; ELISA, enzyme-linked immunosorbent assay; EMT, epithelial–mesenchymal transition; IL-8, interleukin-8; JAK1, Janus kinase 1; LPS, lipopolysaccharide; MMP, matrix metalloproteinase; OSCCs, oral squamous cell carcinomas; PK, proteinase K; PMB, Polymyxin B; qRT-PCR, quantitative real-time polymerase chain reaction; STAT3, signal transducer and activator of transcription 3; TGF-β, transforming growth factor beta; ZEB1, zinc finger E-Box binding homeobox 1

Anaerobic bacterial communities associated with oral carcinoma: Intratumoral, surface-biofilm and salivary microbiota

It was estimated that more than 700 bacterial species inhabit the oral cavity of healthy humans. Anaerobes comprise a significant fraction of the oral bacteriome and play an important role in the formation of multi-species biofilms attached to various anatomical sites. Bacterial biofilms are also associated with pathologic laesions of the oral cavity, including oral squamous cell carcinoma (OSCC), and distinct oral taxa could also be detected within the tumors, i.e. in deep biopsy samples. These observations suggested that certain oral bacteria or oral bacterial communities may play a causative role in oral carcinogenesis, in addition to the well characterized risk factors of oral cancer. Alternatively, it was also proposed that a subset of oral bacteria may have a growth advantage in the unique microenvironment of OSCC. Recently, a series of studies analysed the OSCC-associated bacterial communities using metataxonomic, metagenomic and metatranscriptomic approaches. This review outlines the major differences between the community structure of microbiota in tumor biopsy, surface-biofilm and salivary or oral wash samples collected from OSCC patients, compared to corresponding samples from control persons. A special emphasis is given to the anaerobic bacteria Fusobacterium nucleatum and Fusobacterium periodonticum that were characterised repeatedly as "OSCC-associated" in independent studies. Predicted microbial functions and relevant in vivo experimental models of oral carcinogenesis will also be summarized.

The Role of the Microbiome in Oral Squamous Cell Carcinoma with Insight into the Microbiome-Treatment Axis

Oral squamous cell carcinoma (OSCC) is one of the leading presentations of head and neck cancer (HNC). The first part of this review will describe the highlights of the oral microbiome in health and normal development while demonstrating how both the oral and gut microbiome can map OSCC development, progression, treatment and the potential side effects associated with its management. We then scope the dynamics of the various microorganisms of the oral cavity, including bacteria, mycoplasma, fungi, archaea and viruses, and describe the characteristic roles they may play in OSCC development. We also highlight how the human immunodeficiency viruses (HIV) may impinge on the host microbiome and increase the burden of oral premalignant lesions and OSCC in patients with HIV. Finally, we summarise current insights into the microbiome–treatment axis pertaining to OSCC, and show how the microbiome is affected by radiotherapy, chemotherapy, immunotherapy and also how these therapies are affected by the state of the microbiome, potentially determining the success or failure of some of these treatments.