The Performance of an Oral Microbiome Biomarker Panel in Predicting Oral Cavity and Oropharyngeal Cancers

The potential value of oral microbial signatures for prediction of oral squamous cell carcinoma based on machine learning algorithms

OBJECTIVE

This study aimed to explore the potential predictive value of oral microbial signatures for oral squamous cell carcinoma (OSCC) risk based on machine learning algorithms.

METHODS

The oral microbiome signatures were assessed in the unstimulated saliva samples of 80 OSCC patients and 179 healthy individuals using 16S rRNA gene sequencing. Four different machine learning classifiers were used to develop prediction models.

RESULTS

Compared with control participants, OSCC patients had a higher microbial dysbiosis index (MDI, p < 0.001). Among four machine learning classifiers, random forest (RF) provided the best predictive performance, followed by the support vector machines, artificial neural networks and naive Bayes. After controlling the potential confounders using propensity score matching, the optimal RF model was further developed incorporating a minimal set of 20 bacteria genera, exhibiting better predictive performance than the MDI (AUC: 0.992 vs. 0.775, p < 0.001).

CONCLUSIONS

The novel MDI and RF model developed in this study based on oral microbiome signatures may serve as noninvasive tools for predicting OSCC risk.

The intratumor microbiome varies by geographical location and anatomical site in head and neck squamous cell carcinoma

Head and Neck Squamous Cell Carcinoma (HNSCC) is a highly heterogeneous cancer that is characterized by distinct phenotypes based on anatomical site and etiological agents. Recently, the intratumor microbiome has been implicated in cancer pathogenesis and progression. Although it is well established that the gut microbiome varies with geographical location and is highly influenced by factors such as diet, environment, and genetics, the intratumor microbiome is not very well characterized. In this review, we aim to characterize the HNSCC intratumor microbiome by geographical location and anatomical site. We conducted a review of primary literature from PubMed and assessed studies based on relevancy and recency. To the best of our knowledge, we are the first to comprehensively examine the tumor microenvironment of HNSCC with respect to these two primary factors on a large scale. Our results suggest that there are unique bacterial and fungal biomarkers for HNSCC for each of the following geographical locations: North America, Asia, Europe, Australia, and Africa. We also identified a panel of microbial biomarkers that are unique to two primary HNSCC anatomic sites, as well as microbial biomarkers associated with various etiological agents of HNSCC. Future study of these microbes may improve HNSCC diagnostic and therapeutic modalities by accounting for differences based on geographic regions and anatomical sites.

Oral and periodontal manifestation related during human papilloma virus infections: Update on early prognostic factors

Human Papilloma Virus (HPV) is considered one of the most common sexually transmitted infections and has been shown to play an important role in the pathogenesis of squamous cell carcinomas (SCC) of the cervix and head and neck. Manifestations of HPV infections can be manifold, ranging from asymptomatic infections to benign or potentially malignant lesions to intraepithelial neoplasms and invasive carcinomas. The heterogeneity of clinical manifestations from HPV infection depends on the interactions between the viral agent and the host, a direct consequence of the ability on the part of HPV is to remain silent and to evade and convey the action of the host immune system. The oral mucosa represents one of the tissues for which HPV has a distinct tropism and is frequently affected by infection. While much information is available on the role that HPV infection plays in the development of SCC in the oral cavity, there is less information on asymptomatic infections and benign HPV-induced oral lesions. Therefore, the purpose of this review is to analyze, in light of current knowledge, the early clinical and bio-humoral prognostic features related to the risk of HPV malignant transformation, focusing on subclinical conditions, benign lesions, and the correlation between oral infection and infection in other districts. The data show that the main risk associated with HPV infection is related to malignant transformation of lesions. Although HPV-driven OPSCC is associated with a better prognosis than non-HPV-driven OPSCC, primary prevention and early detection of the infection and affected genotype are essential to reduce the risk of malignant neoplastic complications and improve the prognosis.

Association between oral microbiome and breast cancer in the east Asian population: A Mendelian randomization and case-control study

BACKGROUND

The causal relationship between breast cancer (BC) and the oral microbiome remains unclear. In this case-control study, using two-sample Mendelian randomization (MR), we thoroughly explored the relationship between the oral microbiome and BC in the East Asian population.

METHODS

Genetic summary data related to oral microbiota and BC were collected from genome-wide association studies involving participants of East Asian descent. MR estimates were generated by conducting various analyses. Sequencing data from a case-control study were used to verify the validity of these findings.

RESULTS

MR analysis revealed that 30 tongue and 37 salivary bacterial species were significantly associated with BC. Interestingly, in both tongue and salivary microbiomes, we observed the causal effect of six genera, namely, Aggregatibacter, Streptococcus, Prevotella, Haemophilus, Lachnospiraceae, Oribacterium, and Solobacterium, on BC. Our case-control study findings suggest differences in specific bacteria between patients with BC and healthy controls. Moreover, sequencing data confirmed the MR analysis results, demonstrating that compared with the healthy control group, the BC group had a higher relative abundance of Pasteurellaceae and Streptococcaceae but a lower relative abundance of Bacteroidaceae.

CONCLUSIONS

Our MR analysis suggests that the oral microbiome exerts a causative effect on BC risk, supported by the sequencing data of a case-control study. In the future, studies should be undertaken to comprehensively understand the complex interaction mechanisms between the oral microbiota and BC.

Effects of squamous cell carcinoma and smoking status on oropharyngeal and laryngeal microbial communities

BACKGROUND

Still, little is known about microbial dysbiosis in oropharyngeal and laryngeal tissue as risk factor for development of local squamous cell carcinoma. The site-specific microbiota at these regions in healthy and cancer tissue and their modulation by environmental factors need to be defined.

METHODS

The local microbiota of cancer tissue and healthy controls was profiled by 16S rRNA gene amplicon sequencing and statistical analysis using 111 oropharyngeal and 72 laryngeal intraoperative swabs.

RESULTS

Oropharynx and larynx harbor distinct microbial communities. Clear effects of both smoking and cancer were seen in the oropharynx whereas effects in the larynx were minor.

CONCLUSION

The distinct microbial communities at larynx and oropharynx partially explain why the effects of cancer and smoking were distinct at those sites. Thus, the use of microbiota supposed to mirror community changes in another target location should be avoided and more studies on the actual cancerous environment are necessary.

Implications of oral dysbiosis and HPV infection in head and neck cancer: from molecular and cellular mechanisms to early diagnosis and therapy

Head and neck cancer (HNC) is the sixth most common type of cancer, with more than half a million new cases annually. This review focuses on the role of oral dysbiosis and HPV infection in HNCs, presenting the involved taxons, molecular effectors and pathways, as well as the HPV-associated particularities of genetic and epigenetic changes and of the tumor microenvironment occurred in different stages of tumor development. Oral dysbiosis is associated with the evolution of HNCs, through multiple mechanisms such as inflammation, genotoxins release, modulation of the innate and acquired immune response, carcinogens and anticarcinogens production, generation of oxidative stress, induction of mutations. Thus, novel microbiome-derived biomarkers and interventions could significantly contribute to achieving the desideratum of personalized management of oncologic patients, regarding both early diagnosis and treatment. The results reported by different studies are not always congruent regarding the variations in the abundance of different taxons in HNCs. However, there is a consistent reporting of a higher abundance of Gram-negative species such as Fusobacterium, Leptotrichia, Treponema, Porphyromonas gingivalis, Prevotella, Bacteroidetes, Haemophilus, Veillonella, Pseudomonas, Enterobacterales, which are probably responsible of chronic inflammation and modulation of tumor microenvironment. Candida albicans is the dominant fungi found in oral carcinoma being also associated with shorter survival rate. Specific microbial signatures (e.g., F. nucleatum, Bacteroidetes and Peptostreptococcus) have been associated with later stages and larger tumor, suggesting their potential to be used as biomarkers for tumor stratification and prognosis. On the other hand, increased abundance of Corynebacterium, Kingella, Abiotrophia is associated with a reduced risk of HNC. Microbiome could also provide biomarkers for differentiating between oropharyngeal and hypopharyngeal cancers as well as between HPV-positive and HPV-negative tumors. Ongoing clinical trials aim to validate non-invasive tests for microbiome-derived biomarkers detection in oral and throat cancers, especially within high-risk populations. Oro-pharyngeal dysbiosis could also impact the HNCs therapy and associated side-effects of radiotherapy, chemotherapy, and immunotherapy. HPV-positive tumors harbor fewer mutations, as well as different DNA methylation pattern and tumor microenvironment. Therefore, elucidation of the molecular mechanisms by which oral microbiota and HPV infection influence the HNC initiation and progression, screening for HPV infection and vaccination against HPV, adopting a good oral hygiene, and preventing oral dysbiosis are important tools for advancing in the battle with this public health global challenge.

The Association of Oral Microbiome Dysbiosis with Gastrointestinal Cancers and Its Diagnostic Efficacy

BACKGROUND

The second leading mortality cause in the world is cancer, making it a critical issue that impacts human health. As a result, scientists are looking for novel biomarkers for cancer detection. The oral microbiome, made up of approximately 700 species-level taxa, is a significant source for discovering novel biomarkers. In this review, we aimed to prepare a summary of research that has investigated the association between the oral microbiome and gastrointestinal cancers.

METHODS

We searched online scientific datasets including Web of Science, PubMed, Scopus, and Google Scholar. Eligibility criteria included human studies that reported abundances of the oral microbiome, or its diagnostic/prognostic performance in patients with gastrointestinal cancers.

RESULTS

Some phyla of the oral microbiome have a relationship with cancers. Some particular phyla of the oral microbiome that may be related to gastrointestinal cancers consist of Firmicutes, Actinobacteria, Bacteroidetes, Proteobacteria, and Fusobacteria. Changes in the abundances of Porphyromonas, Fusobacterium, Prevotella, and Veillonella are correlated with carcinogenesis, and may be used for distinguishing cancer patients from healthy subjects. Oral, colorectal, pancreatic, and esophageal cancers are the most important cancers related to the oral microbiome.

CONCLUSION

The results of this study may help future research to select bacteria as an early diagnostic or prognostic biomarker of gastrointestinal cancer. Given the current state of our knowledge, additional research is required to comprehend the multiplex processes underlying the role of bacterial microbiota upon cancer progression and to characterize the complex microbiota-host interaction network.

Oral and Gut Microbiota Dysbiosis is Associated with Mucositis Severity in Autologous Hematopoietic Stem Cell Transplantation: Evidence from an Asian Population

Mucositis is a debilitating complication of hematopoietic stem cell transplantation (HSCT). It is unclear how changes in the composition of microbiota, which are modulated by geographical location and ethnicity, may influence immune regulation leading to the development of mucositis, and the study of both oral and gut microbiota in a single population of autologous HSCT in the Asian region is lacking. The present study aimed to characterize the oral and gut microbiota changes, and the impact on both oral and lower gastrointestinal (GI) mucositis, with associated temporal changes in a population of adult recipients of autologous HSCT. Autologous HSCT recipients age ≥18 years were recruited from Hospital Ampang, Malaysia, between April 2019 and December 2020. Mucositis assessments were conducted daily, and blood, saliva, and fecal samples were collected prior to conditioning, on day 0, and at 7 days and 6 months post-transplantation. Longitudinal differences in alpha diversity and beta diversity were determined using the Wilcoxon signed-rank test and permutational multivariate analysis of variance, respectively. Changes in relative abundances of bacteria across time points were assessed using the microbiome multivariate analysis by linear models function. The combined longitudinal effects of clinical, inflammatory, and microbiota variables on mucositis severity were measured using the generalized estimating equation. Among the 96 patients analyzed, oral mucositis and diarrhea (representing lower GI mucositis) occurred in 58.3% and 95.8%, respectively. Alpha and beta diversities were significantly different between sample types (P < .001) and across time points, with alpha diversity reaching statistical significance at day 0 in fecal samples (P < .001) and at day +7 in saliva samples (P < .001). Diversities normalized to baseline by 6 months post-transplantation. Significant microbiota, clinical, and immunologic factors were associated with increasing mucositis grades. Increasing relative abundances of saliva Paludibacter, Leuconostoc, and Proteus were associated with higher oral mucositis grades, whereas increasing relative abundances of fecal Rothia and Parabacteroides were associated with higher GI mucositis grades. Meanwhile, increasing relative abundances of saliva Lactococcus and Acidaminococcus and fecal Bifidobacterium were associated with protective effects against worsening oral and GI mucositis grades, respectively. This study provides real-world evidence and insights into the dysbiosis of the microbiota in patients exposed to conditioning regimen during HSCT. Independent of clinical and immunologic factors, we demonstrated significant associations between relative bacteria abundances with the increasing severity of oral and lower GI mucositis. Our findings offer a potential rationale to consider the inclusion of preventive and restorative measures targeting oral and lower GI dysbiosis as interventional strategies to ameliorate mucositis outcome in HSCT recipients.

Oral Microbiota: The Influences and Interactions of Saliva, IgA, and Dietary Factors in Health and Disease

Recent advances in metagenomic analyses have made it easier to analyze microbiota. The microbiota, a symbiotic community of microorganisms including bacteria, archaea, fungi, and viruses within a specific environment in tissues such as the digestive tract and skin, has a complex relationship with the host. Recent studies have revealed that microbiota composition and balance particularly affect the health of the host and the onset of disease. Influences such as diet, food preferences, and sanitation play crucial roles in microbiota composition. The oral cavity is where the digestive tract directly communicates with the outside. Stable temperature and humidity provide optimal growth environments for many bacteria. However, the oral cavity is a unique environment that is susceptible to pH changes, salinity, food nutrients, and external pathogens. Recent studies have emphasized the importance of the oral microbiota, as changes in bacterial composition and balance could contribute to the development of systemic diseases. This review focuses on saliva, IgA, and fermented foods because they play critical roles in maintaining the oral bacterial environment by regulating its composition and balance. More attention should be paid to the oral microbiota and its regulatory factors in oral and systemic health.

Intratumoral Microbiota Changes with Tumor Stage and Influences the Immune Signature of Oral Squamous Cell Carcinoma

Characterization of the oral microbiota profile through various studies has shown an association between the microbiome and oral cancer; however, stage-specific determinants of dynamic changes in microbial communities of oral cancer remain elusive. Additionally, the influence of the intratumoral microbiota on the intratumoral immune system remains largely unexplored. Therefore, this study aims to stratify microbial abundance in the early-onset and subsequent stages of oral cancer and analyze their influence on clinical-pathological and immunological features. The microbiome composition of tissue biopsy samples was identified using 16S rRNA amplicon sequencing, while intratumoral and systemic immune profiling was done with flow cytometry and immunohistochemistry-based analysis. The bacterial composition differed significantly among precancer, early cancer, and late cancer stages with the enrichment of genera Capnocytophaga, Fusobacterium, and Treponema in the cancer group, while Streptococcus and Rothia were enriched in the precancer group. Late cancer stages were significantly associated with Capnocytophaga with high predicting accuracy, while Fusobacterium was associated with early stages of cancer. A dense intermicrobial and microbiome-immune network was observed in the precancer group. At the cellular level, intratumoral immune cell infiltration of B cells and T cells (CD4+ and CD8+) was observed with enrichment of the effector memory phenotype. Naive and effector subsets of tumor-infiltrating lymphocytes (TILs) and related gene expression were found to be distinctly associated with bacterial communities; most importantly, highly abundant bacterial genera of the tumor microenvironment were either negatively correlated or not associated with the effector lymphocytes, which led to the conclusion that the tumor microenvironment favors an immunosuppressive and nonimmunogenic microbiota. IMPORTANCE The gut microbiome has been explored extensively for its importance in the modulation of systemic inflammation and immune response; in contrast, the intratumoral microbiome is less studied for its influence on immunity in cancer. Given the established correlation between intratumoral lymphocyte infiltration and patient survival in cases of solid tumors, it was pertinent to explore the extrinsic factor influencing immune cell infiltration in the tumor. Modulation of intratumoral microbiota could have a beneficial effect on the antitumor immune response. This study stratifies the microbial profile of oral squamous cell carcinoma starting from precancer to late-stage cancer and provides evidence for their immunomodulatory role in the tumor microenvironment. Our results suggest combining microbiome study with immunological signatures of tumors for their prognostic and diagnostic application.

Evaluating Alterations of the Oral Microbiome and Its Link to Oral Cancer among Betel Quid Chewers: Prospecting Reversal through Probiotic Intervention

Areca nut and slaked lime, with or without tobacco wrapped in Piper betle leaf, prepared as betel quid, is extensively consumed as a masticatory product in many countries across the world. Betel Quid can promote the malignant transformation of oral lesions as well as trigger benign cellular and molecular changes. In the oral cavity, it causes changes at the compositional level in oral microbiota called dysbiosis. This dysbiosis may play an important role in Oral Cancer in betel quid chewers. The abnormal presence and increase of bacteria Fusobacterium nucleatum, Capnocytophaga gingivalis, Prevotella melaninogenica, Peptostreptococcus sp., Porphyromonas gingivalis, and Streptococcus mitis in saliva and/or other oral sites of the cancer patients has attracted frequent attention for its association with oral cancer development. In the present review, the authors have analysed the literature reports to revisit the oncogenic potential of betel quid and oral microbiome alterations, evaluating the potential of oral microbiota both as a driver and biomarker of oral cancer. The authors have also shared a perspective that the restoration of local microbiota can become a potentially therapeutic or prophylactic strategy for the delay or reversal of lip and oral cavity cancers, especially in high-risk population groups.

Oral-microbiome-derived signatures enable non-invasive diagnosis of laryngeal cancers

BACKGROUND

Recent studies have uncovered that the microbiota in patients with head and neck cancers is significantly altered and may drive cancer development. However, there is limited data to explore the unique microbiota of laryngeal squamous cell carcinoma (LSCC), and little is known regarding whether the oral microbiota can be utilized as an early diagnostic biomarker.

METHODS

Using 16S rRNA gene sequencing, we characterized the microbiome of oral rinse and tissue samples from 77 patients with LSCC and 76 control patients with vocal polyps, and then performed bioinformatic analyses to identify taxonomic groups associated with clinicopathologic features.

RESULTS

Multiple bacterial genera exhibited significant differences in relative abundance when stratifying by histologic and tissue type. By exploiting the distinct microbial abundance and identifying the tumor-associated microbiota taxa between patients of LSCC and vocal polyps, we developed a predictive classifier by using rinse microbiota as key features for the diagnosis of LSCC with 85.7% accuracy.

CONCLUSION

This is the first evidence of taxonomical features based on the oral rinse microbiome that could diagnose LSCC. Our results revealed the oral rinse microbiome is an understudied source of clinical variation and represents a potential non-evasive biomarker of LSCC.

Influence of the microbiome on radiotherapy-induced oral mucositis and its management: A comprehensive review

Radiation-induced mucositis is the most common, debilitating and painful acute toxicity associated with active treatment in head and neck cancer area, severely affecting more than 65% of patients. Oral microbiota significantly changes during cancer therapy and appears to be involved on its pathophysiology. This review aims to present a comprehensive update of new etiopathogenic factors and treatments that may decrease the incidence of mucositis, mainly modifications of dietary interventions to modify microbiome. Despite advances in recent years, its management is mainly symptomatic opioid-based with variable results on different substances analyzed for its prevention. Immunonutrition seems to play a significant role, particularly the supplementation of compounds such as fatty acids, polyphenols or selected probiotics have shown to promote commensal bacteria diversity and reduced incidence of ulcerative mucositis. Modification of the microbiome is a promising preventive treatment for mucositis although its evidence is still scarce. Large studies are needed to demonstrate the efficacy of interventions on microbiome and its clinical impact on radiation-induced mucositis.

From Pathogenesis to Intervention: The Importance of the Microbiome in Oral Mucositis

Oral mucositis (OM) is a common and impactful toxicity of standard cancer therapy, affecting up to 80% of patients. Its aetiology centres on the initial destruction of epithelial cells and the increase in inflammatory signals. These changes in the oral mucosa create a hostile environment for resident microbes, with oral infections co-occurring with OM, especially at sites of ulceration. Increasing evidence suggests that oral microbiome changes occur beyond opportunistic infection, with a growing appreciation for the potential role of the microbiome in OM development and severity. This review collects the latest articles indexed in the PubMed electronic database which analyse the bacterial shift through 16S rRNA gene sequencing methodology in cancer patients under treatment with oral mucositis. The aims are to assess whether changes in the oral and gut microbiome causally contribute to oral mucositis or if they are simply a consequence of the mucosal injury. Further, we explore the emerging role of a patient's microbial fingerprint in OM development and prediction. The maintenance of resident bacteria via microbial target therapy is under constant improvement and should be considered in the OM treatment.

Oral microbiome and risk of incident head and neck cancer: A nested case-control study

OBJECTIVES

This nested case-control study in the NIH-AARP Diet and Health Study was carried out to prospectively investigate the relationship of oral microbiome with head and neck cancer (HNC).

MATERIALS AND METHODS

56 incident HNC cases were identified, and 112 controls were incidence-density matched to cases. DNA extracted from pre-diagnostic oral wash samples was whole-genome shotgun metagenomic sequenced to measure the overall oral microbiome. ITS2 gene qPCR was used to measure the presence of fungi. ITS2 gene sequencing was performed on ITS2 gene qPCR positive samples. We computed taxonomic and functional alpha-diversity and beta-diversity metrics. The presence and relative abundance of groups of red-complex (e.g., Porphyromonas gingivalis) and/or orange-complex (e.g., Fusobacterium nucleatum) periodontal pathogens were compared between cases and controls using conditional logistic regression models and MiRKAT.

RESULTS

Participants with higher taxonomic microbial alpha-diversity had a non-statistically significant decreased risk of HNC. No case-control differences were found for beta diversity by MiRKAT model (all p > 0.05). A greater relative abundance of red-complex periodontal pathogens (OR = 0.51, 95 % CI = 0.26-1.00), orange-complex (OR = 0.38, 95 % CI = 0.18-0.83), and both complexes' pathogens (OR = 0.32, 95 % CI = 0.14-0.75), were associated with reduced risk of HNC. The presence of oral fungi was also strongly associated with reduced risk of HNC compared with controls (OR = 0.39, 95 % CI = 0.17-0.92).

CONCLUSION

Greater taxonomic alpha-diversity, the presence of oral fungi, and the presence or relative abundance of multiple microbial species, including the red- and orange-complex periodontal pathogens, were associated with reduced risk of HNC. Future studies with larger sample sizes are needed to evaluate these associations.

Oral Microbial Signatures of Tobacco Chewers and Oral Cancer Patients in India

Dysbiosis of the oral microbiome has been found to play a key role in the genesis and progression of oral cancer (OC). Tobacco chewing, a risk factor for oral cancer, is also associated with oral dysbiosis. Since tobacco chewing is a lifestyle habit in the South Asian subcontinent, including India, and contributes to one-third of the global oral cancer burden; we aimed to identify the oral bacterial diversity of Indian oral cancer patients and tobacco chewers. We used 16S rRNA amplicon sequencing to study the composition of oral microbiota in OC patients and tobacco chewers in India and compared it with healthy controls. The abundance of predominant phyla, Firmicutes, and Bacteroidetes varied between the study groups. Our study identified Leptotrichia, Treponema, Lautropia, and Cardiobacterium as significantly enriched in tobacco chewers, whereas genera Pseudomonas, Capnocytophaga, and Mycoplasma were enriched in oral cancer, which could be potential biomarkers for the Indian population. Furthermore, the functional prediction revealed that genes involved in lipid biosynthesis and fatty acid elongation were upregulated in the oral cancer group, whereas those for the reductive TCA cycle were upregulated in the tobacco group. As the role of bacteria in oral cancer is becoming more evident, identification of bacterial diversity and biomarkers for tobacco chewers and OC patients can aid in the early diagnosis of OC in high-risk individuals.

The human oral - nasopharynx microbiome as a risk screening tool for nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a common head and neck cancer with a poor prognosis. There is an urgent need to develop a simple and convenient screening tool for early detection and risk screening of NPC. 139 microbial samples were collected from 40 healthy people and 39 patients with nasopharyngeal biopsy. A total of 40 and 39 oral, eight and 27 nasal cavity, nine and 16 nasopharyngeal microbial samples were collected from the two sets of individuals. A risk screening tool for NPC was established by 16S rDNA sequencing and random forest. Patients with nasopharyngeal biopsy had significantly lower nasal cavity and nasopharynx microbial diversities than healthy people. The beta diversity of the oral microbiome was significantly different between the two groups. The NPC screening tools based on nasopharyngeal and oral microbiomes have 88% and 77.2% accuracies, respectively. The nasopharyngeal biopsy patients had significantly higher Granulicatella abundance in their oral cavity and lower Pseudomonas and Acinetobacter in the nasopharynx than healthy people. This study established microbiome-based non-invasive, simple, no radiation, and low-cost NPC screening tools. Individuals at a high risk of NPC should be advised to seek further examination, which might improve the early detection of NPC and save public health costs.

Differences in the microbiota of oral rinse, lesion, and normal site samples from patients with mucosal abnormalities on the tongue

The oral microbiota associated with mucosal diseases, including oral squamous cell carcinoma and oral potentially malignant disorders, have been extensively analyzed at the phylum and genus levels. However, the details of the oral microbiota remain unclear at the species and operational taxonomic unit (OTU) levels. We aimed to determine differences in the microbiota of oral rinse, lesion and normal site swab samples of patients with mucosal abnormalities on the tongues. Oral samples were obtained from 10 patients with oral mucosal abnormalities. Alpha and beta diversity at the OTU and genus levels of the microbiota samples were analyzed using OTUs clustered with 99.6% similarity based on 16S rRNA gene sequences obtained using the Sanger method. At the OTU level, the microbiota of the lesions were the least diverse but were different from those of the normal site and oral rinse samples. The OTUs corresponding to Streptococcus infantis and Haemophilus parainfluenzae were suggested to contribute to the differences between the microbiota of the lesions and normal sites. At the genus level, no significant differences between these microbiota were observed. In conclusion, strict OTU-level microbiota analysis might be able to discriminate lesions from normal sites of patients with mucosal abnormalities.

A Review of the Role of Oral Microbiome in the Development, Detection, and Management of Head and Neck Squamous Cell Cancers

The role of the microbiome in the development and propagation of head and neck squamous cell cancer (HNSCC) is largely unknown and the surrounding knowledge lags behind what has been discovered related to the microbiome and other malignancies. In this review, the authors performed a structured analysis of the available literature from several databases. The authors discuss the merits and detriments of several studies discussing the microbiome of the structures of the aerodigestive system throughout the development of HNSCC, the role of the microbiome in the development of malignancies (generally and in HNSCC) and clinical applications of the microbiome in HNSCC. Further studies will be needed to adequately describe the relationship between HNSCC and the microbiome, and to push this relationship into a space where it is clinically relevant outside of a research environment.

Comparative and analytical characterization of the oral bacteriome of smokeless tobacco users with oral squamous cell carcinoma

Oral cavity squamous cell carcinoma (OSCC) is the most common type of head and neck cancer worldwide. Smokeless tobacco (SLT) has been well proven for its role in oral carcinogenesis due to the abundance of several carcinogens. However, the role of inhabitant microorganisms in the oral cavity of smokeless tobacco users has not yet been well explored in the context of OSCC. Therefore, the present investigation was conceived to analyze the oral bacteriome of smokeless tobacco users having OSCC (CP group). With the assistance of illumina-based sequencing of bacterial-specific V3 hypervariable region of 16S rDNA gene, 71,969 OTUs (operational taxonomic units) were categorized into 18 phyla and 166 genera. The overall analysis revealed that the oral bacteriome of the patients with OSCC, who were smokeless tobacco users, was significantly different compared to the healthy smokeless tobacco users (HTC group) and non-users (HI users). The appearance of 14 significantly abundant genera [FDR (false discovery rate) adjusted probability value of significance (p value) < 0.05] among the CP group showed the prevalence of tobacco-specific nitrosamines forming bacteria (Staphylococcus, Fusobacterium, and Campylobacter). The functional attributes of the oral bacteriome of the CP group can also be correlated with the genes involved in oncogenesis. This study is the first report on the oral bacteriome of Indian patients with OSCC who were chronic tobacco chewers. The results of the present study will pave the way to understand the influence of smokeless tobacco on the oral bacteriome of OSCC patients. KEY POINTS: • Oral bacteriome of OSCC patients differ from healthy smokeless tobacco (SLT) users and SLT non-users. • Smokeless tobacco influences the oral bacteriome of OSCC group. • Oral bacteriome specific diagnostics may be developed for pre-diagnosis of oral cancer.

Role of Microbiota in Viral Infections and Pathological Progression

Viral infections are influenced by various microorganisms in the environment surrounding the target tissue, and the correlation between the type and balance of commensal microbiota is the key to establishment of the infection and pathogenicity. Some commensal microorganisms are known to resist or promote viral infection, while others are involved in pathogenicity. It is also becoming evident that the profile of the commensal microbiota under normal conditions influences the progression of viral diseases. Thus, to understand the pathogenesis underlying viral infections, it is important to elucidate the interactions among viruses, target tissues, and the surrounding environment, including the commensal microbiota, which should have different relationships with each virus. In this review, we outline the role of microorganisms in viral infections. Particularly, we focus on gaining an in-depth understanding of the correlations among viral infections, target tissues, and the surrounding environment, including the commensal microbiota and the gut virome, and discussing the impact of changes in the microbiota (dysbiosis) on the pathological progression of viral infections.

Saliva Based Liquid Biopsies in Head and Neck Cancer: How Far Are We From the Clinic?

Head and neck cancer (HNC) remains to be a major cause of mortality worldwide because of confounding factors such as late-stage tumor diagnosis, loco-regional aggressiveness and distant metastasis. The current standardized diagnostic regime for HNC is tissue biopsy which fails to determine the thorough tumor dynamics. Therefore, due to the ease of collection, recent studies have focused on the utility of saliva based liquid biopsy approach for serial sampling, early diagnosis, prognosis, longitudinal monitoring of disease progression and treatment response in HNC patients. Saliva collection is convenient, non-invasive, and pain-free and offers repetitive sampling along with real time monitoring of the disease. Moreover, the detection, isolation and analysis of tumor-derived components such as Circulating Tumor Nucleic Acids (CTNAs), Extracellular Vesicles (EVs), Circulating Tumor Cells (CTCs) and metabolites from saliva can be used for genomic and proteomic examination of HNC patients. Although, these circulatory biomarkers have a wide range of applications in clinical settings, no validated data has yet been established for their usage in clinical practice for HNC. Improvements in isolation and detection technologies and next-generation sequencing analysis have resolved many technological hurdles, allowing a wide range of saliva based liquid biopsy application in clinical backgrounds. Thus, in this review, we discussed the rationality of saliva as plausible biofluid and clinical sample for diagnosis, prognosis and therapeutics of HNC. We have described the molecular components of saliva that could mirror the disease status, recent outcomes of salivaomics associated with HNC and current technologies which have the potential to improve the clinical value of saliva in HNC.

A Clinical Study on the Relationship Among Insomnia, Tongue Diagnosis, and Oral Microbiome

Currently, there is a lack of adequate methods to assess insomnia objectively. This study addresses the usefulness of tongue features and oral microbial profile as a potential diagnostic biomarker of insomnia. One hundred insomniac patients and 20 healthy control subjects were selected. Their demographic and clinical characteristics, as well as the tongue diagnostic indices and oral microbial profile, were examined. Compared to the control group, insomniac patients showed a higher abnormal low-frequency/high-frequency (LF/HF) ratio. In tongue diagnosis, the indices related to lightness of tongue body and tongue coating were higher in the insomniac group vs. the control group. Furthermore, linear discriminant analysis (LDA) of oral microbial population revealed that the relative abundances of Clostridia, Veillonella, Bacillus and Lachnospiraceae were significantly higher in the insomniac patients than the control group. Additionally, the tongue features of the insomniac group exhibited that the non-coating group had a poor sleep condition compared to the thick-coating group, although the difference was insignificant. On the other hand, the oral microbial communities of the insomniac patients revealed greater alpha and beta diversities in the non-coating group vs. the thick-coating group. The alpha and beta diversities were higher in orotype1 than orotype2. Collectively, this study highlighted that the lightness of tongue body and tongue coating as well as oral microbial profiles of SR1, Actinobacteria, Clostridia and Lachnospiraceae_unclassified could be considered potential biomarkers of insomnia.

Effect of electronic cigarette and tobacco smoking on the human saliva microbial community

Increasing evidence demonstrated the oral microbial community profile characteristics affected by conventional cigarettes smoking, but few studies focus on oral microbiome in response to electronic cigarettes (E-cigarettes). This study aimed to investigate the effect of E-cigarettes on the oral microbiome and to describe the difference of oral community profiles between E-cigarette smokers and tobacco smokers. 16S rRNA V4 gene sequencing was performed to investigate the oral microbial profiles of 5 E-cigarette smokers, 14 tobacco smokers, 8 quitting tobacco smokers, and 6 nonsmokers. The Chao1, ACE, and Shannon diversity indexes increased significantly in saliva samples collected from E-cigarette smokers and tobacco smokers compared to the non-smokers, and no significant difference was found in alpha diversity between E-cigarette smokers and tobacco smokers. The main phyla Proteobacteria, Firmicutes, Bacteroidetes, and Fusobacteria and major genera Neisseria, Streptococcus, Prevotellaceae, Fusobacterium, and Porphyromonas dominated in the smoking groups, while Actinobacteria, Proteobacteria, Firmicutes, Bacteroidetes, and Fusobacteria became the dominant phyla along with the genera Corynebacterium, Neisseria, Streptococcus, Actinomyces, and Porphyromonas in the nonsmokers. The differences in the phylum Actinobacteria and genus Corynebacterium contributed to various functional differences between smokers and nonsmokers. The difference on oral microbial and composition between E-cigarettes and common tobacco were associated with increased Prevotellaceae and decreased Neisseria. Additionally, smoking cessation could lead to re-establishment of the oral microbiome to that of nonsmokers. Our data demonstrate that E-cigarette smoking had different effects on the structure and composition of the oral microbial community compared to tobacco smoking. However, the short- and long-term impact of E-cigarette smoking on microbiome composition and function needs further exploration.

Haemophilus pittmaniae and Leptotrichia spp. Constitute a Multi-Marker Signature in a Cohort of Human Papillomavirus-Positive Head and Neck Cancer Patients

Objectives

Human papillomavirus (HPV) is a known etiological factor of oropharyngeal head and neck cancer (HNC). HPV positivity and periodontal disease have been associated with higher HNC risk, suggesting a role for oral bacterial species. Our objective was to determine oral microbiome profiles in HNC patients (HPV-positive and HPV-negative) and in healthy controls (HC).

Methods

Saliva samples and swabs of buccal mucosa, supragingival plaque, and tongue were collected from HNC patients (N = 23 patients, n = 92 samples) before cancer therapy. Next-generation sequencing (16S-rRNA gene V3–V4 region) was used to determine bacterial taxa relative abundance (RA). β-Diversities of HNC HPV+ (N = 16 patients, n = 64 samples) and HNC HPV– (N = 7 patients, n = 28 samples) groups were compared using PERMANOVA (pMonte Carlo &lt; 0.05). LEfSe discriminant analysis was performed to identify differentiating taxa (Log LDA &gt; 2.0). RA differences were analyzed by Mann–Whitney U-test (α = 0.05). CombiROC program was used to determine multi-marker bacterial signatures. The Microbial Interaction Network Database (MIND) and LitSuggest online tools were used for complementary analyses.

Results

HNC vs. HC and HNC HPV+ vs. HNC HPV– β-diversities differed significantly (pMonte Carlo &lt; 0.05). Streptococcus was the most abundant genus for HNC and HC groups, while Rothia mucilaginosa and Haemophilus parainfluenzae were the most abundant species in HNC and HC patients, respectively, regardless of antibiotics treatment. LEfSe analysis identified 43 and 44 distinctive species for HNC HPV+ and HNC HPV– groups, respectively. In HNC HPV+ group, 26 periodontal disease-associated species identified by LefSe had a higher average RA compared to HNC HPV– group. The significant species included Alloprevotella tannerae, Fusobacterium periodonticum, Haemophilus pittmaniae, Lachnoanaerobaulum orale, and Leptotrichia spp. (Mann–Whitney U-test, p &lt; 0.05). Of 43 LEfSe-identified species in HPV+ group, 31 had a higher RA compared to HPV– group (Mann–Whitney U-test, p &lt; 0.05). MIND analysis confirmed interactions between Haemophilus and Leptotrichia spp., representing a multi-marker signature per CombiROC analysis [area under the curve (AUC) &gt; 0.9]. LitSuggest correctly classified 15 articles relevant to oral microbiome and HPV status.

Conclusion

Oral microbiome profiles of HNC HPV+ and HNC HPV– patients differed significantly regarding periodontal-associated species. Our results suggest that oral bacterial species (e.g., Leptotrichia spp.), possessing unique niches and invasive properties, coexist with HPV within HPV-induced oral lesions in HNC patients. Further investigation into host–microbe interactions in HPV-positive HNC patients may shed light into cancer development.

Oral Human Papillomavirus Associated With Differences in Oral Microbiota Beta Diversity and Microbiota Abundance

BACKGROUND

Although cervicovaginal microbiome has been associated with cervical human papillomavirus (HPV) infection, little is known regarding the association of oral microbiome with oral HPV, a cause of oropharyngeal cancer.

METHODS

A cross-sectional analysis of 495 participants from the Men and Women Offering Understanding of Throat HPV study was conducted. 16S rRNA gene amplicon sequencing was performed on saliva samples. HPV DNA in oral rinse samples was tested. Associations of oral microbiome diversity, taxon abundance, and predicted functional pathways with oral HPV were assessed, adjusting for age, race/ethnicity, education, human immunodeficiency virus, current smoking, and sequencing batch.

RESULTS

Participants with oral HPV (n = 68) compared with those without HPV had similar oral microbiome alpha-diversity yet different beta-diversity (Bray-Curtis distance for bacterial taxa, P = .009; functional pathways, P = .02). Participants with oral HPV had higher abundance of Actinomycetaceae, Prevotellaceae, Veillonellaceae, Campylobacteraceae, Bacteroidetes, and lower abundance of Gemellaceae (false discovery rate <0.10). We also found differential functional potential of oral microbiome by oral HPV status: xenobiotic biodegradation-related pathways were less abundant among participants with oral HPV, suggesting potential xenobiotic-induced toxic effects with implications for HPV susceptibility.

CONCLUSIONS

Our findings suggest a shift in oral microbiome community structure, composition, and functional potential between individuals with and without oral HPV.

Oral Microbiota-A New Frontier in the Pathogenesis and Management of Head and Neck Cancers

Simple Summary

Head and neck squamous cell carcinoma (HNSCC) is a group of common and aggressive tumors. Recently, oral microbiota has been credited as an important player in carcinogenesis. However, the available knowledge is not always consistent and sometimes conflicting. Therefore, the present comprehensive systematic review of the current clinical reports was conducted to evaluate the role of oral microbiota in HNSCC. Importantly, this study addresses whether oral microbiota targeting could provide diagnostic, prognostic or therapeutic utility in cancer patients. We also discussed the current limitations of this newly emerging field and the potential related strategies for the management of patients with HNSCC and possibly other solid tumors.

Abstract

Head and neck squamous cell carcinoma (HNSCC) comprises the majority of tumors in head and neck tissues. The prognosis of HNSCC has not significantly improved for decades, signifying the need for new diagnostic and therapeutic targets. Recent evidence suggests that oral microbiota is associated with carcinogenesis. Thus, we conducted a comprehensive systematic review to evaluate the current evidence regarding the role of oral microbiota in HNSCC and whether their targeting may confer diagnostic, prognostic or therapeutic utility. Following the screening of 233 publications retrieved from multiple databases, 34 eligible studies comprising 2469 patients were compiled and critically appraised. Importantly, many oral pathogens, such as Porphyromonas gingivalis and Fusobacterium nucleatum were linked to certain oral potentially malignant lesions and various types of HNSCC. Furthermore, we summarized the association between the expression profiles of different oral bacterial species and their tumorigenic and prognostic effects in cancer patients. We also discussed the current limitations of this newly emerging area and the potential microbiota-related strategies for preventing and treating HNSCC. Whilst many clinical studies are underway to unravel the role of oral microbiota in cancer, the limited available data and experimental approaches reflect the newness of this promising yet challenging field.

Bacteriome Identified by Next-Generation Sequencing in Saliva, Dental Plaque, and Tumor Tissue of Patients with Oral Squamous Cell Carcinoma

Background:

Oral squamous cell carcinoma (OSCC) is the sixth most common cancer in the world, and the bacterial microbiome has been considered a risk factor that could play an important role in carcinogenesis.

Objective:

A bacteriome study was performed by next-generation sequencing in dental plaque, saliva, and tumor samples of 10 OSCC patients and compared with bacteriome in dental plaque and saliva of 10 patients without OSCC.

Methods:

DNA was extracted from all samples and sequenced by Illumina technology MiSeq™. Bioinformatic analyzes were performed for evaluated sequence quality, alpha and beta diversity, bidirectional analysis of variance (p <0.05), and principal component analysis. After establishing bacterial profiles associated with each sample and population, intragroup and intergroup comparisons were carried out. For bacteria identification compatible with eubiosis and dysbiosis processes, a screening was performed based on the frequency of appearance in all patient samples with and without OSCC. Lastly, frequency, average, standard deviation, Chi-square, and Mann Whitney test were calculated.

Results:

Out of the identified 1,231 bacteria in the populations under study, 45 bacterial species were selected, of which 34 were compatible with eubiosis, and 11 were compatible with dysbiosis. Among the bacteria compatible with eubiosis were species of Lactobacillus and Streptococcus, Chromobacterium violaceum, Enterobacter asburiae, Mycobacterium chubuense, Mycoplasma penetrans, and Brachyspira intermedia. Among the species associated with dysbiosis,  Providencia stuartii, Capnocytophaga canimorsus, Legionella pneumophila, and Mycoplasma hominis were notable.

Conclusion:

Thirty-four bacterial species may be associated with eubiosis or healthy states and 11 bacterial species could be associated with dysbiosis or pathogenic state, OSCC.

Characterization of Oral Bacterial Composition of Adult Smokeless Tobacco Users from Healthy Indians Using 16S rDNA Analysis

The present investigation is aiming to report the oral bacterial composition of smokeless tobacco (SLT) users and to determine the influence of SLT products on the healthy Indian population. With the aid of the V3 hypervariable region of the 16S rRNA gene, a total of 8,080,889 high-quality reads were clustered into 15 phyla and 180 genera in the oral cavity of the SLT users. Comparative analysis revealed a more diverse microbiome where two phyla and sixteen genera were significantly different among the SLT users as compared to the control group (p-value < 0.05). The prevalence of Fusobacteria-, Porphyromonas-, Desulfobulbus-, Enterococcus-, and Parvimonas-like genera among SLT users indicates altered bacterial communities among SLT users. Besides, the depletion of health-compatible bacteria such as Lactobacillus and Haemophilus also suggests poor oral health. Here, the majority of the altered genera belong to Gram-negative anaerobes that have been reported for assisting biofilm formation that leads in the progression of several oral diseases. The PICRUSt analysis further supports the hypothesis where a significant increase in the count of the genes involved in the metabolism of nitrogen, amino acids, and nicotinate/nicotinamide was observed among tobacco chewers. Moreover, this study has a high significance in Indian prospects where the SLT consumers are prevalent but we are deficient in information on their oral microbiome.

Crosstalk between the oral microbiota, mucosal immunity, and the epithelial barrier regulates oral mucosal disease pathogenesis

Oral mucosal disease (OMD), which is also called soft tissue oral disease, is described as a series of disorders or conditions affecting the mucosa and soft tissue in the oral cavity. Its etiology is unclear, but emerging evidence has implicated the influence of the composition of the oral mucosa and saliva-resident microbiota. In turn, this dysbiosis effects the immune response balance and epithelial barrier function, followed by the occurrence and progression of OMD. In addition, oral microbial dysbiosis is diverse in different types of diseases and different disease progressions, suggesting that key causal pathogens may exist in various oral pathologies. This narrative literature review primarily discusses the most recent findings focusing on how microbial dysbiosis communicates with mucosal adaptive immune cells and the epithelial barrier in the context of five representative OMDs, including oral candidiasis (OC), oral lichen planus (OLP), recurrent aphthous ulcer (RAU), oral leukoplakia (OLK), and oral squamous cell carcinoma (OSCC), to provide new insight into the pathogenetic mechanisms of OMDs.

Paradigm shift in the pathogenesis and treatment of oral cancer and other cancers focused on the oralome and antimicrobial-based therapeutics

The oral microbiome is a community of microorganisms, comprised of bacteria, fungi, viruses, archaea, and protozoa, that form a complex ecosystem within the oral cavity. Although minor perturbations in the environment are frequent and compensable, major shifts in the oral microbiome can promote an unbalanced state, known as dysbiosis. Dysbiosis can promote oral diseases, including periodontitis. In addition, oral dysbiosis has been associated with other systemic diseases, including cancer. The objective of this review is to evaluate the epidemiologic evidence linking periodontitis to oral, gastrointestinal, lung, breast, prostate, and uterine cancers, as well as describe new evidence and insights into the role of oral dysbiosis in the etiology and pathogenesis of the cancer types discussed. Finally, we discuss how antimicrobials, antimicrobial peptides, and probiotics may be promising tools to prevent and treat these cancers, targeting both the microbes and associated carcinogenesis processes. These findings represent a novel paradigm in the pathogenesis and treatment of cancer focused on the oral microbiome and antimicrobial‐based therapies.

Current salivary biomarkers for detection of human papilloma virus-induced oropharyngeal squamous cell carcinoma

Human papilloma virus (HPV) infection is a key risk factor and etiology for oropharyngeal squamous cell carcinoma (OPSCC). HPV-induced OPSCC is rapidly increasing in incidence, with men experiencing increased mortality. When identified at an early stage, HPV-induced OPSCC can be successfully treated. Diagnosis of HPV-related OPSCC relies on an expert physical examination and invasive biopsy. Since saliva bathes the oropharyngeal mucosa and can be collected noninvasively, saliva obtained via salivary risings is an attractive body fluid for early detection of HPV-induced OPSCC. A plethora of DNA, RNA, and protein salivary biomarkers have been explored. This review discusses these markers and their robustness for detecting oncogenic HPV in OPSCC saliva samples. Methods detecting HPV DNA were more reliable than those detecting RNA, albeit both require time-consuming analyses. Salivary HPV proteomics are a new, promising focus of HPV detection research, and while more practical, lag behind nucleic acid detection methods in their development.

Oral Microbiota: A Major Player in the Diagnosis of Systemic Diseases

The oral cavity is host to a complex and diverse microbiota community which plays an important role in health and disease. Major oral infections, i.e., caries and periodontal diseases, are both responsible for and induced by oral microbiota dysbiosis. This dysbiosis is known to have an impact on other chronic systemic diseases, whether triggering or aggravating them, making the oral microbiota a novel target in diagnosing, following, and treating systemic diseases. In this review, we summarize the major roles that oral microbiota can play in systemic disease development and aggravation and also how novel tools can help investigate this complex ecosystem. Finally, we describe new therapeutic approaches based on oral bacterial recolonization or host modulation therapies. Collaboration in diagnosis and treatment between oral specialists and general health specialists is of key importance in bridging oral and systemic health and disease and improving patients' wellbeing.

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.

Human papillomavirus infection and tumor microenvironment are associated with the microbiota in patients with oropharyngeal cancers-pilot study

BACKGROUND

Previous microbiome studies of oropharyngeal cancer have shown that there are differences in the oral microbiota between human papillomavirus (HPV)-positive and HPV-negative patients.

METHODS

We collected saliva, normal tissue, and tumor biopsies from 13 patients with oropharyngeal cancer (eight HPV-positive, five HPV-negative). We obtained basic clinical data from each patient. Extracted DNA was 16S rRNA gene sequenced. Analysis was based on HPV status and sample site using univariate, multivariate, and mixed effect regression methods.

RESULTS

Multivariate analysis methods separated samples based on HPV status (Adonis, p < 0.001). Comparison of patients showed that there were significant changes in microbial richness across all sites based on HPV status (linear mixed effects regression, p = 0.0002).

CONCLUSIONS

We found significant differences in overall microbial community and bacterial richness between oropharyngeal patients based on HPV status. Our results suggest that there are significant differences in the microbiome in patients with oropharyngeal cancer based on HPV status.

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.

Spatially resolved sampling for untargeted metabolomics: A new tool for salivomics

Saliva is a complex bodily fluid composed of metabolites secreted by major and minor glands, as well as by-products of host oral cells, oral bacteria, gingival crevicular fluid, and exogenous compounds. Major salivary glands include the paired parotid, submandibular, and sublingual glands. The secreted fluids of the salivary glands vary in composition, flow rate, site of release, and clearance suggesting that different types of saliva fulfill different functions and therefore can provide unique biological information. Consequently, for the comprehension of the functionality of the salivary components, spatially resolved investigations are warranted. To understand and comprehensively map the highly heterogeneous environment of the oral cavity, advanced spatial sampling techniques for metabolomics analysis are needed. Here, we present a systematic evaluation of collection devices for spatially resolved sampling aimed at untargeted metabolomics and propose a comprehensive and reproducible collection and analysis protocol for the spatially resolved analysis of the human oral metabolome.

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Systematic evaluation of collection devices for untargeted metabolomics of saliva

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Spatially resolved sampling of saliva in the human oral cavity

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Enabling location-specific oral metabolomics

Multidimensional role of bacteria in cancer: Mechanisms insight, diagnostic, preventive and therapeutic potential

The active role of bacteria in oncogenesis has long been a topic of debate. Although, it was speculated to be a transmissible cause of cancer as early as the 16th-century, yet the idea about the direct involvement of bacteria in cancer development has only been explored in recent decades. More recently, several studies have uncovered the mechanisms behind the carcinogenic potential of bacteria which are inflammation, immune evasion, pro-carcinogenic metabolite production, DNA damage and genomic instability. On the other side, the recent development on the understanding of tumor microenvironment and technological advancements has turned this enemy into an ally. Studies using bacteria for cancer treatment and detection have shown noticeable effects. Therapeutic abilities of bioengineered live bacteria such as high specificity, selective cytotoxicity to cancer cells, responsiveness to external signals and control after ingestion have helped to overcome the challenges faced by conventional cancer therapies and highlighted the bacterial based therapy as an ideal approach for cancer treatment. In this review, we have made an effort to compile substantial evidence to support the multidimensional role of bacteria in cancer. We have discussed the multifaceted role of bacteria in cancer by highlighting the wide impact of bacteria on different cancer types, their mechanisms of actions in inducing carcinogenicity, followed by the diagnostic and therapeutic potential of bacteria in cancers. Moreover, we have also highlighted the existing gaps in the knowledge of the association between bacteria and cancer as well as the limitation and advantage of bacteria-based therapies in cancer. A better understanding of these multidimensional roles of bacteria in cancer can open up the new doorways to develop early detection strategies, prevent cancer, and develop therapeutic tactics to cure this devastating disease.

The gut microbiome as non-invasive biomarkers for identifying overweight people at risk for osteoarthritis

OBJECTIVE

To evaluate the potential for identifying overweight people at risk for osteoarthritis from a gut microbiome biomarker.

BACKGROUND

Osteoarthritis (OA) is the most common form of arthritis, affecting millions of people worldwide. Being overweight increases the load placed on the joints such as the knee, which increases stress and could hasten the breakdown of cartilage. Identifying overweight people at risk for osteoarthritis remains a challenge. However, emerging evidence indicates that microbial dysbiosis in the human gut might play an important role in many inflammatory diseases. Considering the role of inflammation in OA development, analysis of the gut microbiome might be a potential non-invasive tool for overweight individuals to evaluate their risk for OA.

RESULTS

In this prospective study, we collected 182 stool samples from overweight OA patients (n = 86) and overweight normal people (n = 96) (25 kg/m²<BMI<30 kg/m²). 16S ribosomal RNA gene sequencing for V3 and V4 regions on the Illumina MiSeq platform was used to identify bacteria at different levels and it showed that both the diversity and richness of the gut microbiome decreased in overweight OA patients. Correspondingly, 9 phyla and 87 genera had significantly differences between overweight OA patients and overweight normal people. Finally, we identified 7 optimal microbial biomarkers in genus levels as a panel, including Gemmiger, Klebsiella, Akkermansia, Bacteroides, Prevotella, Alistipes and Parabacteroides, to build the random forest model, and achieved a 83.36% area under the curve (AUC) of receiver operating characteristic (ROC).

CONCLUSION

We present the first 16S rRNA gene sequencing profiling study of stool microbiomes in overweight people to discover and validate microbial biomarkers indicating risk for OA. Our study successfully established a 7 biomarkers prediction panel, moving towards affordable non-invasive early diagnostic biomarkers for OA in stool samples from overweight individuals.

New Insights Into Oral Squamous Cell Carcinoma: From Clinical Aspects to Molecular Tumorigenesis

Oral squamous cell carcinoma (SCC) is a prevalent malignant disease worldwide, especially so in Taiwan. Early- or even preclinical-stage detection is critical for reducing morbidity and mortality from oral SCC. Epidemiological and genome association studies are useful for identifying clinicopathological risk factors for preventive, diagnostic, and therapeutic approaches of oral SCC. For advanced oral SCC, effective treatments are critical to prolonging survival and enhancing quality of life. As oral SCC is characteristic of regional invasion with lymph node metastases, understanding the aggressive features of oral SCC, particularly in lymphangiogenesis, is essential for determining effective treatments. Emerging evidence has demonstrated that the tumor microenvironment (TME) plays a pivotal role in tumor growth, invasion, and metastases. Recent clinical successes in immune checkpoint inhibitors either alone or combined with chemotherapy have also supported the therapeutic value of immunotherapy in oral SCC. This review summarizes critical advances in basic knowledge of oral SCC from the perspective of clinicopathological risk factors, molecular tumorigenesis, and the TME. We also highlight our recent investigations on the microbiome, genome association studies, lymphangiogenesis, and immunomodulation in oral SCC. This review may provide new insights for oral SCC treatment by systematically interpreting emerging evidence from various preclinical and clinical studies.

Dysbiosis of Oral Microbiota During Oral Squamous Cell Carcinoma Development

Infection with specific pathogens and alterations in tissue commensal microbial composition are intricately associated with the development of many human cancers. Likewise, dysbiosis of oral microbiome was also shown to play critical role in the initiation as well as progression of oral cancer. However, there are no reports portraying changes in oral microbial community in the patients of Indian subcontinent, which has the highest incidence of oral cancer per year, globally. To establish the association of bacterial dysbiosis and oral squamous cell carcinoma (OSCC) among the Indian population, malignant lesions and anatomically matched adjacent normal tissues were obtained from fifty well-differentiated OSCC patients and analyzed using 16S rRNA V3-V4 amplicon based sequencing on the MiSeq platform. Interestingly, in contrast to the previous studies, a significantly lower bacterial diversity was observed in the malignant samples as compared to the normal counterpart. Overall our study identified Prevotella, Corynebacterium, Pseudomonas, Deinococcus and Noviherbaspirillum as significantly enriched genera, whereas genera including Actinomyces, Sutterella, Stenotrophomonas, Anoxybacillus, and Serratia were notably decreased in the OSCC lesions. Moreover, we demonstrated HPV-16 but not HPV-18 was significantly associated with the OSCC development. In future, with additional validation, this panel could directly be applied into clinical diagnostic and prognostic workflows for OSCC in Indian scenario.

Chemoradiation therapy changes oral microbiome and metabolomic profiles in patients with oral cavity cancer and oropharyngeal cancer

BACKGROUND

Patients with oral cavity cancer (OCC) and oropharyngeal cancer (OPC) are often seen with locoregionally advanced disease requiring complex multimodality treatments. These treatments may have detrimental effects on the oral microbiome, which is critical to maintaining physiological balance and health.

METHODS

The effects of different OCC and OPC treatment types on the oral microbiome and metabolomic profiles for 24-month post-treatment in patients with OCC and OPC were investigated using 16S rRNA gene amplicon next-generation sequencing and gas chromatography-mass spectrometry (GC-MS), respectively.

RESULTS

Chemoradiation resulted in oral dysbiosis with specific depletion of genera which regulate the enterosalivary nitrate-nitrite-nitric oxide pathway. These data also correlate with the oral metabolomic profiles with nitric oxide-related precursor, modulator, or catalyst significantly downregulated in saliva samples from patients' postchemoradiation.

CONCLUSIONS

Together, we have shown that oral dysbiosis due to the effects of chemoradiation could potentially have an impact on OCC and OPC patient's quality of life post-treatment.

Potential Association between Vaginal Microbiota and Cervical Carcinogenesis in Korean Women: A Cohort Study

Convincing studies demonstrated that vaginal flora is one of the most impactful key components for the well-being of the genital tract in women. Nevertheless, the potential capability of vaginal-derived bacterial communities as biomarkers to monitor cervical carcinogenesis (CC) has yet to be studied actively compared to those of bacterial vaginosis (BV). We hypothesized that vaginal microbiota might be associated with the progression of CC. In this study, we enrolled 23 participants, including healthy controls (HC group; n = 7), patients with cervical intraepithelial neoplasia (CIN) 2 and 3 (CIN group, n = 8), and patients with invasive cervical cancer (CAN group; n = 8). Amplicon sequencing was performed using the Ion Torrent PGM to characterize the vaginal microbiota. Patients with CIN and CAN presented vaginal microbiota dysbiosis compared with HC. The alpha diversity analysis revealed that CC has a trend to be increased in terms of diversity indexes. Moreover, CC was associated with the abundance of specific microbes, of which Lactobacillus and Gardnerella were the most significantly different between HC and CIN, whereas Streptococcus was differentially abundant in CAN compared with CIN. We then evaluated their diagnostic abilities. Testing in terms of diagnostic ability using the three genera revealed considerably high performance with an area under the receiver-operating characteristic curve of 0.982, 0.953, and 0.922. The current study suggests that the presence of Gardnerella and Streptococcus may be involved in the advancment of CC.

Linking the oral microbiome and salivary cytokine abundance to circadian oscillations

Saliva has immense potential as a diagnostic fluid for identification and monitoring of several systemic diseases. Composition of the microbiome and inflammation has been associated and reflective of oral and overall health. In addition, the relative ease of collection of saliva further strengthens large-scale diagnostic purposes. However, the future clinical utility of saliva cannot be fully determined without a detailed examination of daily fluctuations that may occur within the oral microbiome and inflammation due to circadian rhythm. In this study, we explored the association between the salivary microbiome and the concentration of IL-1β, IL-6 and IL-8 in the saliva of 12 healthy adults over a period of 24 h by studying the 16S rRNA gene followed by negative binomial mixed model regression analysis. To determine the periodicity and oscillation patterns of both the oral microbiome and inflammation (represented by the cytokine levels), two of the twelve subjects were studied for three consecutive days. Our results indicate that the Operational Taxonomic Units (OTUs) belonging to Prevotella, SR1 and Ruminococcaceae are significantly associated to IL-1β while Prevotella and Granulicatella were associated with IL-8. Our findings have also revealed a periodicity of both the oral microbiome (OTUs) and inflammation (cytokine levels) with identifiable patterns between IL-1β and Prevotella, and IL-6 with Prevotella, Neisseria and Porphyromonas. We believe that this study represents the first measure and demonstration of simultaneous periodic fluctuations of cytokine levels and specific populations of the oral microbiome.

Clinical validation of 13-gene DNA methylation analysis in oral brushing samples for detection of oral carcinoma: Italian multicenter study

BACKGROUND

The aim of this Italian multicenter study was to evaluate the diagnostic performance of a minimally invasive method for the detection of oral squamous cell carcinoma (OSCC) based on 13-gene DNA methylation analysis in oral brushing samples.

METHODS

Oral brushing specimens were collected in 11 oral medicine centers across Italy. Twenty brushing specimens were collected by each center, 10 from patients with OSCC, and 10 from healthy volunteers. DNA methylation analysis was performed in blindness, and each sample was determined as positive or negative based on a predefined cutoff value.

RESULTS

DNA amplification failed in 4 of 220 (1.8%) samples. Of the specimens derived from patients with OSCC, 93.6% (103/110) were detected as positive, and 84.9% (90/106) of the samples from healthy volunteers were negative.

CONCLUSION

These data confirmed the diagnostic performance of our novel procedure in a large cohort of brushing specimens collected from 11 different centers and analyzed in blindness.

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.

HPV-Related Oropharyngeal Cancer and Biomarkers Based on Epigenetics and Microbiome Profile

H uman papillomavirus (HPV) is considered the main cause of the increasing incidence rates of oropharyngeal squamous cell carcinoma (OPSCC), and soon, the global burden of HPV-related OPSCC is predicted to exceed that of cervical cancer. Moreover, a different molecular profile for HPV-related OPSCC has been described, opening new promising targeted therapies and immunotherapy approaches. Epigenetic and microbiome-based exploration of biomarkers has gained growing interest with a view to the primary oropharyngeal cancer (OPC) screening. Understanding the role of the epigenetic mechanism and the changes that occur during pathogenesis shows appreciable progress in recent years. The different methylation status of DNA and miRNAs demonstrates the value of possible biomarkers discriminating even in different stages of dysplasia. Through whole-genome bisulfite sequencing, differentially methylated regions (DMRs) hold the key to recover missing information. O n the other hand, the microbiota investigation signifies a new biomarker approach for the evaluation of OPC. Along with known cofactors playing a major role in microbiota differentiation, HPV-related cases must be explored further for better understanding. The dynamic approach of the shotgun metagenomic sequencing will robustly fill the gap especially in species/strain level and consequently to biomarker detection. The constantly growing incidence of HPV-related OPC should lead us in further investigation and understanding of the unique features of the disease, more accurate diagnostic methods, along with the development and implementation of new, targeted therapies. This paper comprehensively reviews the significance of biomarkers based on epigenetics and microbiome profile in the accuracy of the diagnosis of the HPV-related cancer in the oropharynx.