Association of Oral Microbiome With Risk for Incident Head and Neck Squamous Cell Cancer

Alterations of salivary microbial community associated with oropharyngeal and hypopharyngeal squamous cell carcinoma patients

The highest number (35.1% of global incident cases) of new oropharyngeal (OP) and hypopharyngeal (HP) cancer cases was reported in South-Central Asia. The highest incidence of HP cancer in India was reported in East Khasi Hills District of Meghalaya, Aizawl District of Mizoram, and Kamrup Urban District of Assam. HP and OP cancer showed the highest mortality rate, worst prognoses and the highest rate of nodal metastases and distant metastases. Thus, research is required to detect specific biomarkers for early prevention and diagnosis for these cancers. Oral microbiome signatures in saliva are considered as a potential diagnostic biomarker for OP and HP cancer. Bacterial profile alterations in OP and HP cancer have not been reported in India population, to establish the association of oral bacteria in the progression of OP and HP cancer; we studied bacterial communities in saliva of eight OP and seven HP cancer patients as compared to healthy controls using 16S rRNA V3-V4 region sequencing. The higher abundance of Haemophilus parainfluenzae, Haemophilus influenzae and Prevotella copri and lower abundance of Rothia mucilaginosa, Aggregatibacter segnis, Veillonella dispar, Prevotella nanceiensis, Rothia aeria, Capnocytophaga ochracea, Neisseria bacilliformis, Prevotella nigrescens and Selenomonas noxia in saliva of OP and HP cancer patients may be considered as a non-invasive diagnostic biomarker for OP and HP cancer patients. Streptococcus anginosus may be considered as a non-invasive diagnostic biomarker for OP cancer patients only. Therefore, evaluation of salivary microbial biomarkers may be informative to understand the pathobiology and carcinogenesis of OP and HP cancer.

Cigarette smoking and oral microbiota in low-income and African-American populations

BACKGROUND

Cigarette smoking is a common risk factor for diseases and cancers. Oral microbiota is also associated with diseases and cancers. However, little is known about the impact of cigarette smoking on the oral microbiota, especially among ethnic minority populations.

METHODS

We investigated cigarette smoking in relationship with the oral microbiota in a large population of predominately low-income and African-American participants. Mouth rinse samples were collected from 1616 participants within the Southern Community Cohort Study, including 592 current-smokers, 477 former-smokers and 547 never-smokers. Oral microbiota was profiled by 16S ribosomal RNA gene deep sequencing.

RESULTS

Current-smokers showed a different overall microbial composition from former-smokers (p=6.62×10-7) and never-smokers (p=6.00×10-8). The two probiotic genera, Bifidobacterium and Lactobacillus, were enriched among current-smokers when compared with never-smokers, with Bonferroni-corrected p values (PBonferroni ) of 1.28×10-4 and 5.89×10-7, respectively. The phylum Actinobacteria was also enriched in current-smokers when compared with never-smokers, with a median relative abundance of 12.35% versus 9.36%, respectively, and with a PBonferroni =9.11×10-11. In contrast, the phylum Proteobacteria was depleted in current smokers (PBonferroni =5.57×10-13), with the relative abundance being almost three times that of never-smokers (7.22%) when compared with that of current-smokers (2.47%). Multiple taxa within these two phyla showed differences in abundance/prevalence between current-smokers and never-smokers at PBonferroni <0.05. The differences in the overall microbial composition and abundance/prevalence of most taxa were observed among both African-Americans and European-Americans. Meanwhile, such differences were not observed between former-smokers and never-smokers.

CONCLUSION

Smoking has strong impacts on oral microbial community, which was recovered after smoking cessation.

Immunotherapy in head and neck cancer: The great challenge of patient selection

The development of immune checkpoint inhibitors (ICIs) revolutionized the therapeutic landscape in head and neck cancer. However, the majority of patients present primary resistance to ICIs and do not benefit from use of these agents, highlighting the need of developing predictive biomarkers to better determine who will benefit from treatment with ICIs. Patient's related clinical characteristics, disease related features, pathological and molecular factors, as well as emerging immune predictive biomarkers can be considered for the selection of those patients who would be the best candidate for immunotherapy. We examined these factors, emerging from the results of currently available studies in head and neck squamous cell carcinoma (HNSCC), in order to provide a useful tool which could assist the oncologist in their clinical practice.

An assessment of Oxford Nanopore sequencing for human gut metagenome profiling: A pilot study of head and neck cancer patients

Gut metagenome profiling using the Oxford Nanopore Technologies (ONT) sequencer was assessed in a pilot-sized study of 10 subjects. The taxonomic abundance of gut microbiota derived from ONT was comparable with Illumina Technology (IT) for the high-abundance species. IT better detected low-abundance species through amplification, when material was limited.

Association between the relative abundance of gastric microbiota and the risk of gastric cancer: a case-control study

The human gut hosts a diverse community of bacteria referred to as the gut microbiome. We investigated the association between the relative abundance of gastric microbiota and gastric cancer (GC) risk in a Korean population. The study participants included 268 GC patients and 288 controls. DNA was extracted from gastric biopsies, and 16S rRNA gene analysis was performed. Unconditional logistic regression models were used to observe the associations. Of the participants, those who had the highest level (highest tertile) of relative Helicobacter pylori and Propionibacterium acnes abundances showed a significantly higher risk for GC after adjusting for potential confounding variables (odds ratio (OR) = 1.86, 95% confidence interval (CI) = 1.17–2.97, p for trend = 0.017 and OR = 4.77, 95% CI = 2.94–7.74, p for trend <0.001, respectively). Subjects who carried Prevotella copri had a significantly higher risk of GC than noncarriers (OR = 2.54, 95% CI = 1.42–4.55, p for trend = 0.002). There was a lower risk of GC in subjects carrying Lactococcus lactis than in noncarriers (OR = 0.21, 95% CI = 0.10–0.44, p for trend <0.001). H. pylori, P. acnes and P. copri are strong risk factors, whereas L. lactis is a protective factor, for GC development in Koreans. Further microbiome studies are warranted to verify the findings of the current study.

Microbiomic differences at cancer-prone oral mucosa sites with marijuana usage

Marijuana smoke contains cannabinoids, immunosuppressants, and a mixture of potentially-mutagenic chemicals. In addition to systemic disease, it is thought to contribute to oral disease, such as tooth loss, tissue changes in the gums and throat, and possibly oral pharyngeal cancer. We used a cross-sectional study of 20 marijuana users and 19 control non-users, to determine if chronic inhalation-based exposure to marijuana was associated with a distinct oral microbiota at the two most common sites of head and neck squamous cell carcinoma (HNSCC), the lateral border of the tongue and the oral pharynx. At the tongue site, genera earlier shown to be enriched on HNSCC mucosa, Capnocytophaga, Fusobacterium, and Porphyromonas, were at low levels in marijuana users, while Rothia, which is found at depressed levels on HNSCC mucosa, was high. At the oral pharynx site, differences in bacteria were distinct, with higher levels of Selenomonas and lower levels of Streptococcus which is what is seen in HNSCC. No evidence was seen for a contribution of marijuana product contaminating bacteria to these differences. This study revealed differences in the surface oral mucosal microbiota with frequent smoking of marijuana.

Polymorphisms of the TERT-CLPTM1L Gene Are Associated with Pharynx-Larynx Cancer

Pharynx-larynx cancer is a complex malignant tumor with the sixth-highest morbidity and mortality rate worldwide. The telomerase reverse transcriptase TERT-CLPTM1L gene, located on chromosome 5p15.33, plays a key role in the occurrence and progression of various cancer. The purpose of this hospital-based case-control study of patients in northern China was to explore the association between two single-nucleotide polymorphisms (SNPs) rs401681 in TERT and rs2736100 in CLPTM1L and the risk of head and neck cancer. We collected samples and relative characteristics and then analyzed the relationship between SNPs and pharynx-larynx cancer susceptibility by logistic regression analysis. The results suggested that the male patients carrying CT and CT+CC genotype model of rs401681 was associated with reduced risk of pharynx-larynx cancer compared with the CC genotype (adjusted odds ratios were 0.701 and 0.704, and 95% confidence intervals were 0.495-0.992 and 0.506-0.980; p-values were 0.045 and 0.038, respectively). In addition, we found that subjects with allele-C showed a relatively low risk of pharyngeal cancer when smoking exposure history was obtained. But the limitation is that in the future we need to further investigate about the exact functional effect of these two variant genes and a larger scale sample. Overall, in this research, our results show that the TERT-CLPTM1L gene could be a meaningful biomarker for pharynx-larynx cancer susceptibility.

Oral microbiome and obesity in a large study of low-income and African-American populations

Few studies have evaluated the relationship of oral microbiome with obesity. We investigated the oral microbiome among 647 obese and 969 non-obese individuals from the Southern Community Cohort Study, through 16S rRNA gene sequencing in mouth rinse samples. We first investigated 16 taxa in two probiotic genera, Bifidobacterium and Lactobacillus. Among them, eight showed nominal associations with obesity (P < 0.05). Especially, Bifidobacterium (odds ratio [OR] = 0.67, 95% confidence interval [CI]:0.54, 0.83) and Bifidobacterium longum (OR = 0.57, 95% CI: 0.45, 0.73) were significantly associated with decreased obesity prevalence with false-discovery rate (FDR)-corrected P of 0.01 and 5.41 × 10-4, respectively. Multiple other bacterial taxa were also significantly associated with obesity prevalence at FDR-corrected P < 0.05. Among them, five in Firmicutes and two respectively in Actinobacteria and Proteobacteria were significantly associated with increased obesity prevalence. Significant associations with decreased obesity prevalence were observed for two taxa respectively in Actinobacteria and Firmicutes. Most of these taxa were associated with body mass index at study enrollment and weight gain during adulthood. Also, most of these associations were observed in both European- and African-Americans. Our findings indicate that multiple oral bacterial taxa, including several probiotic taxa, were significantly associated with obesity.

The Oral Mouse Microbiome Promotes Tumorigenesis in Oral Squamous Cell Carcinoma

Oral squamous cell carcinoma (OSCC) is the most common malignancy of the head and neck worldwide. Dysbiosis of the microbiome has increasingly been linked to the development of different kinds of cancer. Applying 16S rRNA gene sequence analysis and metatranscriptomic analyses, we characterized the longitudinal changes in the profiles and the function of the oral microbiome in a 4-nitroquinoline-1-oxide (4-NQO)-induced model of OSCC in gnotobiotic mice. We characterized the dynamics of the oral microbiome in this model using two different microbiome inocula: one from healthy mice and the other from mice bearing a 4-NQO-induced tumor. Mice colonized with different oral microbiomes and exposed to 4-NQO had increased tumor numbers and sizes compared to controls exposed to 4-NQO but lacking a microbiome. We observed an overall increase in diversity in the tumorigenic samples compared to that in the nontumor group not exposed to 4-NQO. Despite the variability in community dynamics, specific patterns emerged during the progression of the disease. In the two groups that were inoculated with the OSCC-associated microbiome, we observed opposite profiles of abundance in Parabacteroides and Corynebacterium While the percentage of Parabacteroides bacteria decreased in the control group, it increased in the OSCC group, and the opposite was observed for Corynebacterium The metatranscriptomic analysis revealed overexpression of the same metabolic signatures associated with OSCC regardless of the community profile. These included nitrogen transport, response to stress, interspecies interactions, Wnt pathway modulation, and amino acid and lipid biosynthesis. Thus, these results seem to suggest that certain collective physiological activities are critical for microbiome-mediated OSCC progression.IMPORTANCE There is growing evidence that changes in the microbiome are associated with carcinogenesis. To date, no consistent oral microbiome composition associated with OSCC has been identified. Longitudinal and functional studies like the study presented here should yield a better understanding of the role that the oral microbiome plays in OSCC. Our findings, obtained using a germ-free mouse model, indicate that the presence of different oral microbiomes enhances tumorigenesis and increases the final number of tumors in mice. By studying community-wide expression profiles, we found that regardless of the phylogenetic composition of the microbiome, the same metabolic activities were consistently associated with OSCC. Therefore, due to the functional redundancy of the microbiome, the critical element in explaining the contribution of the microbiota in OSCC is the collective physiological activity of the community, thus accounting for the previous inability to identify a consensus community profile or etiologic agents for OSCC.

Smoking and microbiome in oral, airway, gut and some systemic diseases

The human microbiome harbors a diverse array of microbes which establishes a mutually beneficial relation with the host in healthy conditions, however, the dynamic homeostasis is influenced by both host and environmental factors. Smoking contributes to modifications of the oral, lung and gut microbiome, leading to various diseases, such as periodontitis, asthma, chronic obstructive pulmonary disease, Crohn’s disease, ulcerative colitis and cancers. However, the exact causal relationship between smoking and microbiome alteration remains to be further explored.

Serum IgG Antibodies against Periodontal Microbes and Cancer Mortality

INTRODUCTION

Periodontitis is a chronic inflammatory condition initiated by microorganisms and is positively linked to systemic conditions such as cancer, cardiovascular disease, and diabetes mellitus.

OBJECTIVES

To prospectively investigate associations between empirically derived clusters of IgG antibodies against 19 selected periodontal microorganisms and cancer mortality in a representative sample of the US population.

METHODS

We evaluated 6,491 participants aged ≥40 y from the Third National Health and Nutrition Examination Survey (1988 to 1994), who had complete data on IgG antibody titers against 19 selected periodontal microorganisms and were free of cardiovascular disease and cancer. In a prior study, antibodies were categorized into 4 mutually exclusive groups via cluster analysis: red-green, orange-red, yellow-orange, and orange-blue. Cluster scores were estimated by summing z scores of the antibody titers making up each cluster. Participants were followed up to death until December 31, 2011. Cox proportional hazard models were applied to estimate hazard ratios (HRs) and 95% CIs for all-cancer mortality by tertiles of cluster scores.

RESULTS

During follow-up for a median of 15.9 y, there were 2,702 deaths (31.3%), including 631 cancer-related deaths (8.1%). After adjusting for multiple confounders, the orange-blue cluster was inversely associated with cancer mortality (tertile 2 vs. tertile 1: HR = 0.67, 95% CI = 0.54 to 0.84; tertile 3 vs tertile 1: HR = 0.62, 95% CI = 0.46 to 0.84). The association between the yellow-orange cluster and all-cancer mortality was also inverse but not significant, and the orange-red cluster and the red-green cluster were not associated with all-cancer mortality.

CONCLUSIONS

Antibodies against Eubacterium nodatum and Actinomyces naeslundii may be novel predictors of cancer mortality. If further studies establish a causal relationship between these antibodies and cancer mortality, they could be targets to prevent possible systemic effects of periodontal disease with potential interventions to raise their levels.

KNOWLEDGE TRANSFER STATEMENT

Periodontal antibodies against Eubacterium nodatum and Actinomyces naeslundii were inversely associated with cancer mortality among adults followed up for an average of 16 y. Periodontal antibodies may predict cancer mortality.

Variations in Oral Microbiota Composition Are Associated With a Risk of Throat Cancer

In this study, a next-generation sequencing strategy on 16S ribosomal RNA (16S rRNA) gene was employed to analyze 70 oral samples from 32 patients with throat cancer, nine patients with vocal cord polyp, and 29 healthy individuals (normal controls). Using this strategy, we demonstrated, for the first time, that the salivary microbiota of cancer patients were significantly different from those of patients with a polyp and healthy individuals. We observed that the beta diversity of the cancer group was divergent from both the normal and polyp groups, while alpha-diversity indices such as the Chao1 estimator (P = 8.1e-05), Simpson (P = 0.0045), and Shannon (P = 0.0071) were significantly reduced in cancer patients compared with patients containing a polyp and normal healthy individuals. Linear discriminant analysis (LDA) and Kruskal–Wallis test analyses and real-time quantitative polymerase chain reaction (qPCR) verification test revealed that the genera Aggregatibacter, Pseudomonas, Bacteroides, and Ruminiclostridium were significantly enriched in the throat cancer group compared with the vocal cord polyp and normal control groups (score value >2). Finally, diagnostic models based on putatively important constituent bacteria were constructed with 87.5% accuracy [area under the curve (AUC) = 0.875, 95% confidence interval (CI): 0.695–1]. In summary, in this study we characterized, for the first time, the oral microbiota of throat cancer patients without smoking history. We speculate that these results will help in the pathogenic mechanism and early diagnosis of throat cancer.

Beyond Head and Neck Cancer: The Relationship Between Oral Microbiota and Tumour Development in Distant Organs

An altered oral microbiota has been linked with the development of several oral diseases, such as dental caries, periodontal disease, and oral stomatitis. Moreover, poor oral health has been linked to head and neck cancer, particularly oral cancer. In recent years a growing number of studies indicate that oral microbiota could be involved in the development of primary tumours outside of head and neck region. The aim of this article is to review the recent studies based on high-throughput technology to present evidences of a relationship between oral microbiota and "non-head and neck tumours." Oral dysbiosis seem to be more pronounced in patients with tumours of gastrointestinal tract, in particular oesophageal, gastric, pancreatic, and colorectal cancers, paving the way for developing specific oral microbiota test to allow early cancer detection. Regarding other tumour types, the results are promising but highly preliminary and still debated. Currently, there are several factors that limit the generalization of the results, such as the small sample size, the lack of adequate clinical information about patients, the different sequencing techniques used, and biological sample heterogeneity. Although only at the beginning, the analysis of oral microbiota could be the next step in the evolution of cancer therapy and will help clinicians to develop individualised approaches to cancer prevention and treatment.

AllergoOncology: Microbiota in allergy and cancer-A European Academy for Allergy and Clinical Immunology position paper

The microbiota can play important roles in the development of human immunity and the establishment of immune homeostasis. Lifestyle factors including diet, hygiene, and exposure to viruses or bacteria, and medical interventions with antibiotics or anti-ulcer medications, regulate phylogenetic variability and the quality of cross talk between innate and adaptive immune cells via mucosal and skin epithelia. More recently, microbiota and their composition have been linked to protective effects for health. Imbalance, however, has been linked to immune-related diseases such as allergy and cancer, characterized by impaired, or exaggerated immune tolerance, respectively. In this AllergoOncology position paper, we focus on the increasing evidence defining the microbiota composition as a key determinant of immunity and immune tolerance, linked to the risk for the development of allergic and malignant diseases. We discuss novel insights into the role of microbiota in disease and patient responses to treatments in cancer and in allergy. These may highlight opportunities to improve patient outcomes with medical interventions supported through a restored microbiome.

Potential associations of circulating growth differentiation factor-15 with sex hormones in male patients with coronary artery disease

This study aimed to explore the association between growth differentiation factor-15 (GDF-15), a stress-induced factor, and sex hormones in male patients with coronary artery disease (CAD). In this study, we recruited 253 male patients with CAD and 205 male controls. Patients were divided into three groups in accordance with GDF-15 tertiles. Serum levels of GDF-15, testosterone, estradiol and other biochemical variables were measured. Serum levels of GDF-15 were significantly increased and serum testosterone and testosterone/estradiol ratio (T/E2 ratio) were significantly decreased in CAD patients compared with controls. Patients with high GDF-15 levels had lower testosterone (203.97, 95% CI 154.67-328.30 vs. 303.98, 95% CI 246.93-345.66; P = 0.001) and T/E2 ratio (8.82, 95% CI 5.77-11.41 vs. 11.07, 95% CI 7.91-14.32; P = 0.013). Correlation analyses showed that serum GDF-15 levels inversely correlated with testosterone levels (r = -0.339) and T/E2 ratio (r = -0.365) (both P < 0.001). In multivariate regression analyses, the association between GDF-15 and T/E2 ratio was maintained (B=-0.442, 95% CI -99.568 to -6.991, P = 0.015). Furthermore, in vitro studies showed a synergistic effect of testosterone and estradiol on GDF-15 secretion, and demonstrated that testosterone association with estradiol decreased GDF-15 secretion through androgen receptor/estrogen receptor-mediated pathways. Together, these results suggest that upregulation of GDF-15 in the presence of low and imbalanced sex hormone levels may contribute to CAD. Thus, restoring the balance of testosterone and estradiol may inhibit the effects of GDF-15 and serve as a promising therapeutic strategy for the treatment of CAD.

Evaluation of Oral Cavity DNA Extraction Methods on Bacterial and Fungal Microbiota

The objective of this study was to evaluate the most effective method of DNA extraction of oral mouthwash samples for use in microbiome studies that utilize next generation sequencing (NGS). Eight enzymatic and mechanical DNA extraction methods were tested. Extracted DNA was amplified using barcoded primers targeting the V6 variable region of the bacterial 16S rRNA gene and the ITS1 region of the fungal ribosomal gene cluster and sequenced using the Illumina NGS platform. Sequenced reads were analyzed using QIIME and R. The eight methods yielded significantly different quantities of DNA (p < 0.001), with the phenol-chloroform extraction method producing the highest total yield. There were no significant differences in observed bacterial or fungal Shannon diversity (p = 0.64, p = 0.93 respectively) by extraction method. Bray-Curtis beta-diversity did not demonstrate statistically significant differences between the eight extraction methods based on bacterial (R2 = 0.086, p = 1.00) and fungal (R2 = 0.039, p = 1.00) assays. No differences were seen between methods with or without bead-beating. These data indicate that choice of DNA extraction method affect total DNA recovery without significantly affecting the observed microbiome.

No difference in 4-nitroquinoline induced tumorigenesis between germ-free and colonized mice

Variations in oral bacterial communities have been linked to oral cancer suggesting that the oral microbiome is an etiological factor that can influence oral cancer development. The 4-nitroquinoline 1-oxide (4-NQO)-induced murine oral and esophageal cancer model is frequently used to assess the effects of preventive and/or therapeutic agents. We used this model to assess the impact of the microbiome on tumorigenesis using axenic (germ-free) and conventionally housed mice. Increased toxicity was observed in germ-free mice, however, no difference in tumor incidence, multiplicity, and size was observed. Transcriptional profiling of liver tissue from germ-free and conventionally housed mice identified 254 differentially expressed genes including ten cytochrome p450 enzymes, the largest family of phase-1 drug metabolizing enzymes in the liver. Gene ontology revealed that differentially expressed genes were enriched for liver steatosis, inflammation, and oxidative stress in livers of germ-free mice. Our observations emphasize the importance of the microbiome in mediating chemical toxicity at least in part by altering host gene expression. Studies on the role of the microbiome in chemical-induced cancer using germ-free animal models should consider the potential difference in dose due to the microbiome-mediated changes in host metabolizing capacity, which might influence the ability to draw conclusions especially for tumor induction models that are dose dependent.

Immune biomarkers of response to immune-checkpoint inhibitors in head and neck squamous cell carcinoma

Anti-programmed cell death protein 1 (PD-1) agents have become the standard of care for platinum-refractory recurrent/metastatic head and neck squamous cell carcinoma (HNSCC) and are currently being evaluated in various disease settings. However, despite the gain in overall survival seen in some of the clinical trials, the majority of patients display primary resistance and do not benefit from these agents. Taking into consideration the potentially severe immune-related toxicities and their high cost, the search for predictive biomarkers of response is crucial. Besides Programmed death ligand-1 (PD-L1) expression, other biomarkers such as immune infiltration, tumor mutational burden or immune-gene expression profiling have been explored, but none of them has been validated in this disease. Among these, the microbiota has recently garnered tremendous interest since it has proven to influence the efficacy of PD-1 blockade in some tumor types. With the accumulating evidence on the effect of the microbiota in HNSCC tumorigenesis and progression, the study of its potential role as a predictive immune biomarker is warranted. This review examines the available evidence on emerging immune predictive biomarkers of response to anti-PD-1/PD-L1 therapy in HNSCC, introducing the microbiota and its potential use as a predictive immune biomarker in this disease.

Role of Oral Microbiome Signatures in Diagnosis and Prognosis of Oral Cancer

Despite advancement in cancer treatment, oral cancer has a poor prognosis and is often detected at late stage. To overcome these challenges, investigators should search for early diagnostic and prognostic biomarkers. More than 700 bacterial species reside in the oral cavity. The oral microbiome population varies by saliva and different habitats of oral cavity. Tobacco, alcohol, and betel nut, which are causative factors of oral cancer, may alter the oral microbiome composition. Both pathogenic and commensal strains of bacteria have significantly contributed to oral cancer. Numerous bacterial species in the oral cavity are involved in chronic inflammation that lead to development of oral carcinogenesis. Bacterial products and its metabolic by-products may induce permanent genetic alterations in epithelial cells of the host that drive proliferation and/or survival of epithelial cells. Porphyromonas gingivalis and Fusobacterium nucleatum induce production of inflammatory cytokines, cell proliferation, and inhibition of apoptosis, cellular invasion, and migration thorough host cell genomic alterations. Recent advancement in metagenomic technologies may be useful in identifying oral cancer-related microbiome, their genomes, virulence properties, and their interaction with host immunity. It is very important to address which bacterial species is responsible for driving oral carcinogenesis. Alteration in the oral commensal microbial communities have potential application as a diagnostic tool to predict oral squamous cell carcinoma. Clinicians should be aware that the protective properties of the resident microflora are beneficial to define treatment strategies. To develop highly precise and effective therapeutic approaches, identification of specific oral microbiomes may be required. In this review, we narrate the role of microbiome in the progression of oral cancer and its role as an early diagnostic and prognostic biomarker for oral cancer.

Bugs in the system: bringing the human microbiome to bear in cancer immunotherapy

The influence of the composition of the human microbiome on the efficacy of cancer directed immunotherapies, such as antibodies directed against the programmed cell death 1 protein (PD-1) or its ligand (PD-L1), has garnered increasing attention as the role of immunotherapies in the care of cancer has grown. Dysbiosis (altered microbiota) has recently been reported to adversely affect the efficacy of cancer directed immunotherapies, and correction of this dysbiosis has the potential to improve the efficacy of these treatments. However, the exact mechanisms underlying this relationship remains unknown. Current methods for characterizing the microbiome likely capture only a small portion of the highly complex interaction between the microbiome and the immune system. Here we discuss the recent reports of the influence of dysbiosis on cancer immunotherapy, methods to more fully characterize the interaction between the microbiome and the immune system, and methods of modulating the immune system to improve the efficacy of cancer immunotherapy.

Association of Coffee and Tea Intake with the Oral Microbiome: Results from a Large Cross-Sectional Study

Background: The oral microbiota play a central role in oral health, and possibly in carcinogenesis. Research suggests that coffee and tea consumption may have beneficial health effects. We examined the associations of these common beverages with the oral ecosystem in a large cross-sectional study.Methods: We assessed oral microbiota in mouthwash samples from 938 participants in two U.S. cohorts using 16S rRNA gene sequencing. Coffee and tea intake were assessed from food frequency questionnaires. We examined associations of coffee and tea intake with overall oral microbiota diversity and composition using linear regression and permutational MANOVA, respectively, and with taxon abundance using negative binomial generalized linear models; all models adjusted for age, sex, cohort, body mass index, smoking, ethanol intake, and energy intake.Results: Higher tea intake was associated with greater oral microbiota richness (P = 0.05) and diversity (P = 0.006), and shifts in overall community composition (P = 0.002); coffee was not associated with these microbiome parameters. Tea intake was associated with altered abundance of several oral taxa; these included Fusobacteriales, Clostridiales, and Shuttleworthia satelles (higher with increasing tea) and Bifidobacteriaceae, Bergeyella, Lactobacillales, and Kingella oralis (lower with increasing tea). Higher coffee intake was only associated with greater abundance of Granulicatella and Synergistetes.Conclusions: In the largest study to date of tea and coffee consumption in relation to the oral microbiota, the microbiota of tea drinkers differed in several ways from nondrinkers.Impact: Tea-driven changes to the oral microbiome may contribute to previously observed associations between tea and oral and systemic diseases, including cancers. Cancer Epidemiol Biomarkers Prev; 27(7); 814-21. ©2018 AACR.

Comparison of the oral microbiome in mouthwash and whole saliva samples

Population-based epidemiologic studies can provide important insight regarding the role of the microbiome in human health and disease. Buccal cells samples using commercial mouthwash have been obtained in large prospective cohorts for the purpose of studying human genomic DNA. We aimed to better understand if these mouthwash samples are also a valid resource for the study of the oral microbiome. We collected one saliva sample and one Scope mouthwash sample from 10 healthy subjects. Bacterial 16S rRNA genes from both types of samples were amplified, sequenced, and assigned to bacterial taxa. We comprehensively compared these paired samples for bacterial community composition and individual taxonomic abundance. We found that mouthwash samples yielded similar amount of bacterial DNA as saliva samples (p from Student's t-test for paired samples = 0.92). Additionally, the paired samples had similar within sample diversity (p from = 0.33 for richness, and p = 0.51 for Shannon index), and clustered as pairs for diversity when analyzed by unsupervised hierarchical cluster analysis. No significant difference was found in the paired samples with respect to the taxonomic abundance of major bacterial phyla, Bacteroidetes, Firmicutes, Proteobacteria, Fusobacteria, and Actinobacteria (FDR adjusted q values from Wilcoxin signed-rank test = 0.15, 0.15, 0.87, 1.00 and 0.15, respectively), and all identified genera, including genus Streptococcus (q = 0.21), Prevotella (q = 0.25), Neisseria (q = 0.37), Veillonella (q = 0.73), Fusobacterium (q = 0.19), and Porphyromonas (q = 0.60). These results show that mouthwash samples perform similarly to saliva samples for analysis of the oral microbiome. Mouthwash samples collected originally for analysis of human DNA are also a resource suitable for human microbiome research.