Inflammatory Bacteriome and Oral Squamous Cell Carcinoma

Identification of Aerobic Salivary Microorganisms in Patients With Oral Squamous Cell Carcinoma Using MALDI-TOF MS: Preliminary Findings From a Pilot Study

RATIONALE

Oral squamous cell carcinoma (OSCC) is a multifactorial disease, and emerging evidence links the oral microbiome to its development. Rapid, noninvasive identification of salivary microorganisms may offer novel diagnostic and prognostic insights into oral cancer.

METHODS

Salivary microbiota from OSCC patients and healthy individuals were analyzed using MALDI Biotyper. Saliva samples were cultured, and microbial identification was performed based on protein spectral profiles using an UltrafleXtreme MALDI-TOF mass spectrometer.

RESULTS

Thirteen OSCC patients (mean age 55 ± 11 years; 69% male) and nineteen healthy controls (mean age 55 ± 10 years; 79% male) were analyzed. Distinct microbial profiles were observed in OSCC patients, including pathogenic species previously associated with carcinogenesis, suggesting potential biomarkers for oral cancer.

CONCLUSIONS

The MALDI Biotyper is an effective, noninvasive tool for identifying salivary microbiota. Its application may support early diagnosis and prognosis of OSCC, reinforcing the significance of the oral microbiome in cancer etiology.

Comparative analysis of bacterial abundance and diversity in tumour tissue of oral squamous cell carcinoma and non-tumour tissue: insights from a systematic review of 16S ribosomal RNA sequencing

BACKGROUND

As per the recent research findings, there is a significant difference between the bacteriome of normal tissue (NT) and tumor tissues (TT) of oral squamous cell carcinoma (OSCC). Identifying this distinct bacteriome is crucial for understanding their potential contribution to oral carcinogenesis. This systematic review (SR) aims to identify exclusive and relative bacterial abundance and bacterial diversity in TT and NT.

METHODOLOGY

The review was conducted following the PRISMA guidelines. PUBMED and SCOPUS databases were searched for studies in English published till 31st August 2024. The inclusion criteria focused on identifying bacteriome in NT versus TT at either species,/genus, and/or phylum level through 16 s ribosomal RNA sequencing. Quality assessment was performed using an eleven-parameter tool combining the Newcastle-Ottawa Scale and customized criteria.

RESULT

Evaluating the selected 13 articles, we have identified the exclusive and relative abundance of bacteriome in TT and NT at phylum, genus, and species levels. Three phyla such as Chloroflexota, Deinococcus-Thermus, and Mycoplasmatota, are found exclusively in TT. Seven genus such as Eubacterium, Campylobacter, Aeromonas, Oceanivigra, Rheinheimera, Weissella, and Catonella are exclusively found in TT. Ten species such as Micrococcus luteus, Prevotella melaninogenica, Exiguobacterium oxidotolerans, Fusobacterium naviforme, Staphylococcus aureus, Veillonella parvula, Parvimonas sp oral taxon 110, Eubacterium II G1 infirmum, Eubacterium XI G3 Brachy, Weissella viridescens are found in TT. Six genus such as Capnocytophaga, Selenomonas, Leptothrix, Desulfovibrio, Desulfoplanes, Pelospora are found exclusively in NT. Eleven species, such as Streptococcus sp. Oral taxon 071,Selenomonas sputigena, Treponema pedis, Acholeplasmatales bacterium, Capnocytophaga haemolytica, Eubacterium sp., Syntrophomonadaceae genomosp.,Treponema putidum, Mitsuokella sp., Actinomyces sp. Oral taxon 848 str. F0332, p- 2534 - 18B5-gut-group are found in NT. Seven common genera within which different species are identified in TT and NT, suggesting differences in bacterial behaviour and characteristics within the same genus. A total of 12 phyla, 35 genera, and 54 species were found to be relatively more abundant in TT compared to NT. Conversely, 7 phyla, 32 genera, and 45 species were relatively more abundant in NT than in TT. Considerable variations in diversity metrics were found between TT and NT.

CONCLUSION

This systematic review is the first to identify a distinct bacteriome exclusive to OSCC tumour tissue compared to normal tissue using 16S ribosomal RNA sequencing. This pioneering work lays the foundation for future studies on the oral microbiome as a potential diagnostic or therapeutic target in oral cancer management. It emphasizes the importance of exploring species-level differences for a deeper understanding of their roles in OSCC.

TRIAL REGISTRATION

Not applicable.

Microsatellite Instability in the Tumor Microenvironment: The Role of Inflammation and the Microbiome

BACKGROUND

Microsatellite instability (MSI) is a hallmark of DNA mismatch repair (MMR) deficiency that leads to genomic instability and increased cancer risk. The tumor microenvironment (TME) significantly influences MSI-driven tumorigenesis, and emerging evidence points to a critical role of the microbiome in shaping this complex interplay.

METHODS

This review comprehensively examines the existing literature on the intricate relationship between MSI, microbiome, and cancer development, with a particular focus on the impact of microbial dysbiosis on the TME.

RESULTS

MSI-high tumors exhibited increased immune cell infiltration owing to the generation of neoantigens. However, immune evasion mechanisms such as PD-1/CTLA-4 upregulation limit the efficacy of immune checkpoint inhibitors (ICIs) in a subset of patients. Pathobionts, such as Fusobacterium nucleatum and Bacteroides fragilis, contribute to MSI through the production of genotoxins, further promoting inflammation and oxidative stress within the TME.

CONCLUSIONS

The microbiome profoundly affects MSI-driven tumorigenesis. Modulation of the gut microbiota through interventions such as fecal microbiota transplantation, probiotics, and dietary changes holds promise for improving ICI response rates. Further research into cancer pharmacomicrobiomics, investigating the interplay between microbial metabolites and anticancer therapies, is crucial for developing personalized treatment strategies.

Exploring oral microbiome in oral squamous cell carcinoma across environment-associated sample types

The relationship between the oral microbiome and oral squamous cell carcinoma (OSCC) has been extensively investigated. Nonetheless, most previous studies were single-center, resulting in the absence of systematic evaluations. To address this gap, we performed a comprehensive meta-analysis on 1,255 samples from OSCC-related 16S rRNA gene data sets, representing a diverse range of OSCC phenotypes. It is recognized that the progression of cancer is related to the alterations in the microbiome among different phenotypes. Our findings revealed distinct microbiome characteristics among different sample types, with Biopsy (Bios) and Swab samples exhibiting significant differences between phenotypes. In Bios samples, the microbiomes of the Cancer group and the normal tissue adjacent to the tumor (NAT) group display a higher similarity, while both differ from the microbiome of the Fibroepithelial polyp (FEP) group. Moreover, the identified differential genera and pathways corresponded with these observations. We developed a diagnostic model using the random forest algorithm on Swab samples, achieving an area under the receiver operating characteristic curve (AUC) of 0.918. Importantly, this model exhibited considerable effectiveness (AUC = 0.849) when applied to another sequencing platform. Taken together, our study provides a comprehensive overview of the oral microbiome during various OSCC progression stages, potentially enhancing early detection and treatment.IMPORTANCEThis study answers key questions regarding the universal microbial characteristics and comprehensive oral microbiome dynamics during oral squamous cell carcinoma (OSCC) progression. By integrating multiple data sets, we examine the following critical aspects: (1) Do different sample types harbor distinct microbial communities within the oral cavity? (2) Which sample types offer greater potential for investigating OSCC progression? (3) How are the oral microbiomes of the Cancer group, normal tissue adjacent to the tumor group, and Fibroepithelial polyp group related, and what is their potential association with OSCC development? (4) Can a diagnostic model based on microbial signatures effectively distinguish between Cancer and Health groups using Swab samples?

Decoding Salivary ncRNAomes as Novel Biomarkers for Oral Cancer Detection and Prognosis

Oral cancer (OC) ranks among the most prevalent head and neck cancers, becoming the eleventh most common cancer worldwide with ~350,000 new cases and 177,000 fatalities annually. The rising trend in the occurrence of OC among young individuals and women who do not have tobacco habits is escalating rapidly. Surgical procedures, radiation therapy, and chemotherapy are among the most prevalent treatment options for oral cancer. To achieve better therapy and an early detection of the cancer, it is essential to understand the disease's etiology at the molecular level. Saliva, the most prevalent body fluid obtained non-invasively, holds a collection of distinct non-coding RNA pools (ncRNAomes) that can be assessed as biomarkers for identifying oral cancer. Non-coding signatures, which are transcripts lacking a protein-coding function, have been identified as significant in the progression of various cancers, including oral cancer. This review aims to examine the role of various salivary ncRNAs (microRNA, circular RNA, and lncRNA) associated with disease progression and to explore their functions as potential biomarkers for early disease identification to ensure better survival outcomes for oral cancer patients.

Dysbiosis of Oral Microbiome: A Key Player in Oral Carcinogenesis? A Critical Review

The oral cavity is known to harbor hundreds of microorganisms, belonging to various genera, constituting a peculiar flora called the oral microbiome. The change in the relative distribution of the constituents of this microbial flora, due to any reason, leads to oral dysbiosis. For centuries, oral dysbiosis has been linked to the etiopathogenesis of several medical illnesses, both locally and systemically-. However, aided by the recent advent of bio-technological capabilities, several reports have re-emerged that link oral dysbiosis to oral carcinogenesis, and numerous studies are currently exploring their association and plausible mechanisms. Some of the proposed mechanisms of oral dysbiosis-induced carcinogenesis (ODIC) include-a bacteria-induced chronic inflammatory state leading to direct cellular damage, inflammatory-cytokine-mediated promotion of cellular proliferation and invasion, release of bacterial products that are carcinogenic, and suppression of local immunity by alteration of the tumor microenvironment. However, the actual interactions between these cellular mechanisms and their role in carcinogenesis are not yet fully understood. This review provides a comprehensive overview of the various hypotheses and mechanisms implicated in the ODIC, along with the corresponding molecular aberrations. Apart from discussing the usual constituents of the oral microbiome profile, the review also summarizes the various dysbiosis profiles implicated in ODIC. The review also sheds light on the potential clinical implications of the research on oral microbiome in the prevention and management of oral cancer.

The Global Trends and Advances in Oral Microbiome Research on Oral Squamous Cell Carcinoma: A Systematic Review

The oral microbiome is increasingly recognized as a key factor in the development and progression of oral squamous cell carcinoma (OSCC). Dysbiosis has been associated with inflammation and tumorigenesis, highlighting the potential of microbial alterations and salivary biomarkers as tools for early, non-invasive diagnosis. This review examines recent advancements in understanding the oral microbiome's role in OSCC. A comprehensive synthesis of studies from 2016 to 2024 was conducted to identify emerging themes and significant findings in the field. Key topics included the interplay between microbiome-driven mechanisms and cancer development, with a focus on microbial communities and their metabolic byproducts. The findings emphasize the importance of specific microbial alterations in modulating immune responses and tumor microenvironments, as well as the promise of biomarkers such as interleukins and miRNA signatures in improving diagnostic accuracy. Recent research trends indicate growing interest in the therapeutic potential of targeting the oral microbiome in OSCC management. Despite significant advancements, gaps remain in the understanding of the precise mechanisms linking dysbiosis to cancer progression. This review underscores the need for continued research to develop personalized diagnostic and therapeutic strategies based on the oral microbiome, with the potential to transform OSCC management.

Oral Leukoplakia Microbiome Predicts the Degree of Dysplasia and is Shaped by Smoking and Tooth Loss

OBJECTIVE

This study aimed to determine if the oral potentially malignant disorder, oral leukoplakia (OLK), exhibited microbiome changes that predict the degree of dysplasia and the risk of malignant progression.

RESULTS

We examined the microbiome in 216 swabs of OLK from 177 patients. Compared to healthy controls (n = 120 swabs from 61 patients), who were less likely to smoke and had better oral health, OLK patients exhibited an increased abundance of Rothia mucilaginosa, Streptococcus parasanguinis and S. salivarius, resembling acetaldehyde generating communities described previously. Compared to the patients' healthy contralateral normal (CLN) mucosa (n = 202), which acts as a matched control for oral health parameters, OLK exhibited increased S. infantis, Leptotrichia spp., Bergeyella spp., Porphyromonas spp. and F. nucleatum. Machine learning with clinical and microbiome data could discriminate high-risk dysplasia (moderate to severe) from low-risk dysplasia (none or mild) (sensitivity 87.4%; specificity 76.5%). Follow-up swabs were recovered from 58 patients, eight of whom progressed to a higher grade of dysplasia or OSCC and these eight patients exhibited a higher abundance of Fusobacterium species at their initial presentation.

CONCLUSIONS

Our study suggests that the OLK microbiome has potential to be an aid to the prediction of dysplasia grade and the risk of malignant transformation.

The role of the microbiome in head and neck squamous cell cancers

The human microbiome has garnered tremendous interest in the field of oncology, and microbiota studies in head and neck oncology has also flourished. Given the increasing incidence and mortality of HNSCC, as well as the suboptimal outcomes of available treatments, there is an urgent need for innovative approaches involving the microbiome. This review evaluates the intricate relationship between the microbiome and HNSCC, highlighting the potential of the microbiome as a marker for cancer detection, its role in malignancy, and its impact on the efficacy of conventional treatments like chemotherapy and radiotherapy. The review also explores the effects of treatment modalities on the microbiome and discusses the potential of microbiome alterations to predict and influence treatment toxicities such as mucositis and xerostomia. Further research is warranted to characterize the microbiome-HNSCC association, which holds promise for advancing early diagnosis, enhancing prognostic accuracy, and personalizing treatment strategies to improve patient outcomes. The exploration of the microbiome in clinical trials indicates a burgeoning subject of microbiome-focused therapies, heralding a new frontier in most cancer care.

Oral microbiota: the overlooked catalyst in cancer initiation and progression

The advancement of high-throughput sequencing technology in recent decades has led to a greater understanding of the components of the oral microbiota, providing a solid foundation for extensive research in this field. The oral microbiota plays an important role in an individual's overall health. It has been shown to be significantly correlated with chronic human diseases, including diabetes, rheumatoid arthritis, cardiovascular disease, periodontal disease, and Alzheimer's disease. Furthermore, tumor occurrence and development are closely related to the oral microbiome. Specific bacteria, such as Fusobacterium nucleatum (F. nucleatum), Porphyromonas gingivalis (P. gingivalis), Streptococcus, Streptomyces, Prevotella, and Fibrophagy gingivalis, play critical roles in cancer development. The oral microbiota has various oncogenic mechanisms, including bacterial inflammation, immunological suppression, tumor growth mediated by bacterial toxins, antiapoptotic activity, and carcinogenic effects. This paper reviews the role of the oral microbiota in the occurrence and progression of cancer and systematically elucidates the molecular mechanisms by which dysbiosis influences tumorigenesis and tumor progression. This information can provide a theoretical basis for exploring cancer treatment strategies and offer new insights for cancer prevention.

Oral microbiome profiles in oral potentially malignant disorders and oral cancer - A diagnostic perspective

Background

Dysregulation of the oral microbiome has been correlated with many diseases, but oral microbiome in the etiopathogenesis of oral cancer remains a grey area and needs to be explored. It is imperative to understand the oral microbiome profiles so as to know the variations in the composition from normal to pre-cancer to cancer.

Aim

To profile the oral microbiome of normal, oral potentially malignant disorders (leukoplakia - Leu, oral submucous fibrosis - OSMF) and oral squamous cell carcinoma (OSCC) by Next-Generation Sequencing of the 16S ribosomal rRNA gene.

Material and Methods

This is an observational cross-sectional study. A total of 50 subjects were selected for this study, which included the the normal, Leukoplakia, OSMF, and OSCC groups. Bacterial genomic DNA was extracted, and 16S rRNA gene sequencing of the V4 region was carried out using the Illumina MiSeq system. Bio-informatics data analysis was carried out using the DADA2 pipeline and phyloseq R package, and the t-test was used for statistical analysis.

Results and Conclusion

Variations in the composition of the oral microbiome were identified across all study groups, and significant differences were noted in certain microbial taxa across normal, pre-cancer, and cancer. Certain bacterial taxa were detected only in OSCC. An increase in relative abundance of Gram-negative bacteria as well as an increasing trend in the abundance of periodontal taxa was observed in OSCC. This study generated a baseline data which may provide a guideline for future functional and integrative oral microbiome studies. Variations in oral microbiome composition may be used as biomarkers and provide signatures during the progression from normal to pre-cancer to cancer.

Metagenomic shotgun sequencing reveals the enrichment of Salmonella and Mycobacterium in larynx due to prolonged ethanol exposure

The exposure of ethanol increases the risk of head and neck inflammation and tumor progression. However, limited studies have investigated the composition and functionality of laryngeal microbiota under ethanol exposure. We established an ethanol-exposed mouse model to investigate the changes in composition and function of laryngeal microbiota using Metagenomic shotgun sequencing. In the middle and late stages of the experiment, the laryngeal microbiota of mice exposed to ethanol exhibited obvious distinguished from that of the control group on principal-coordinate analysis (PCoA) plots. Among the highly abundant species, Salmonella enterica and Mycobacterium marinum were likely to be most impacted. Our findings indicated that the exposure to ethanol significantly increased their abundance in larynxes in mice of the same age, which has been confirmed through FISH experiments. Among the species-related functions and genes, metabolism is most severely affected by ethanol. The difference was most obvious in the second month of the experiment, which may be alleviated later because the animal established tolerance. Notable enrichments concerning energy, amino acid, and carbohydrate metabolic pathways occurred during the second month under ethanol exposure. Finally, based on the correlation between species and functional variations, a network was established to investigate relationships among microbiota, functional pathways, and related genes affected by ethanol. Our data first demonstrated the continuous changes of abundance, function and their interrelationship of laryngeal microbiota under ethanol exposure by Metagenomic shotgun sequencing.

Importance

Ethanol may participate in the inflammation and tumor progression by affecting the composition of the laryngeal microbiota. Here, we applied the metagenomic shotgun sequencing instead of 16 S rRNA sequencing method to identify the laryngeal microbiota under ethanol exposure. Salmonella enterica and Mycobacterium marinum are two dominant species that may play a role in the reconstruction of the laryngeal microenvironment, as their local abundance increases following exposure to ethanol. The metabolic function is most evidently impacted, and several potential metabolic pathways could be associated with alterations in microbiota composition. These findings could help us better understand the impact of prolonged ethanol exposure on the microbial composition and functionality in the larynx.

Predicting cancer-related mycobiome aspects in gastrointestinal cancers: a systematic review

Background

Colonization of the human gut and tumor tissue by non-pathogenic fungi has emerged as a potential risk factor associated with cancer epidemics. Therefore, we aimed to conduct a systematic review to assess the role of fungal colonization in gastrointestinal (GI) tumors in increasing diagnostic efficiency.

Methods

A PubMed citation search was conducted for publications up to and including March 2023, followed by full-text screening. Results were reported according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines. According to the Patient, Intervention, Comparison, Outcome (PICO) framework, patients diagnosed with early-and advanced-stage GI cancers, GI adenoma patients, and healthy subjects were included with metagenomic (MG) or internal transcribed spacer (ITS) sequencing on tumor tissue, adjacent normal tissue, stool, and blood samples.

Results

Fourteen studies were eligible based on the inclusion criteria and methodological quality. Studies were conducted in stool (n = 8) or tissue (n = 7) as the most common specimens to be used for molecular analysis. In the collected data, ITS was used in n = 10 cases and metagenomic analyses in n = 3 cases. Observing the interindividual variability, we found that the Ascomycota/Basidiomycota (A/B) ratio from healthy to cancer state decreased in n = 2, increased in n = 1 cases, and did not change significantly in n = 2 studies. An increase in the relative abundance of Malassezia was identified in n = 4, of Candida in n = 5, of Saccharomyces in n = 2, and of Aspergillus in n = 2 cases. Intraindividual differences in the A/B ratio were identified in cancer and adjacent tissue (n = 4) and cancer vs. stool (n = 1) studies. Intraindividual variability of the A/B ratio showed an increase in n = 2 and no change in n = 3 studies for cancer tissue.

Conclusion

In conclusion, the advent of highly sensitive sequencing methods may aid in the identification and the differentiation of cancerous from healthy human fungal colonizations with potential future diagnostic applications. Further studies are needed to establish reliable biomarkers for GI cancer screening.

Succession of the multi-site microbiome along pancreatic ductal adenocarcinoma tumorigenesis

Background

To investigate microbial characteristics across multibody sites from chronic pancreatitis (CP), through pancreatic benign tumors, to pancreatic ductal adenocarcinoma (PDAC) at different stages.

Methods

16S ribosomal RNA (rRNA) amplicon sequencing was conducted on saliva, duodenal fluid, and pancreatic tissue obtained via endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) of patients with CP, pancreatic benign tumors, PDAC in stage I/II, III, and IV. The neutral community model (NCM) assessed the microbial assembly contribution and MaAslin2 identified the differential microbes.

Results

From CP to stage IV PDAC patients, there was a marked surge in influence of salivary and duodenal microbiota on constitution of pancreatic microbial communities. Our observations revealed a successive alteration in microbial species across various bodily sites during PDAC tumorigenesis. Notably, Porphyromonas gingivalis, Treponema denticola, Peptoanaerobacter stomatis, Propionibacterium acidifaciens, Porphyromonas endodontalis, Filifactor alocis, etc., sequentially increased along PDAC progression in pancreatic tissue, whereas bacteria commonly used as probiotics Bifidobacterium breve, Lactiplantibacillus plantarum, etc., declined. Furthermore, the sequentially escalating trends of Peptoanaerobacter stomatis and Propionibacterium acidifaciens during PDAC tumorigenesis were mirrored in duodenal fluid and saliva. Porphyromonas gingivalis, Porphyromonas endodontalis, and Filifactor alocis, which intensified from CP to stage IV PDAC in pancreatic tissue, were also found to be enriched in saliva of patients with short-term survival (STS) compared with those with long-term survival (LTS).

Conclusions

Salivary and duodenal microorganisms were prominent factors in shaping pancreatic microbial landscape in PDAC context. Further exploration of these microbial entities is imperative to unravel their specific roles in PDAC pathogenesis, potentially yielding insights for future therapeutic strategies.

Assessing the oral microbiome of head and neck cancer patients before and during radiotherapy

OBJECTIVE

To characterize the oral microbiome of patients with head and neck squamous cell carcinoma (HNSCC) before and during radiotherapy (RT), compared to healthy individuals. Evaluating the impact of oral microbiome in the clinical outcomes one year following the end of RT.

METHODS

Oral samples were collected from HNSCC patients who underwent RT using the following regimens: no dose received (T0), dose 12-16 Gy (T1), dose 30-36 Gy (T2) and dose ≥ 60 Gy (T3). Samples from healthy individuals were also collected only once as a control group. Regions V1-V2 of the 16S rRNA were sequenced by Illumina and analyzed using Mothur.

RESULTS

49 patients with HNSCC and 25 healthy individuals were included. At T0, HNSCC patients showed a lower abundance of Firmicutes and Streptococcus (p = 0.011, p = 0.002) and a higher abundance of Bacteroidetes (p = 0.005) compared to healthy individuals. During RT, Fusobacterium (p = 0.017) and Porphyromonas (p = 0.0008) decreased, while Streptococcus increased at T1 (p = 0.001). By T3, the differences in Firmicutes, Bacteroidetes, and Streptococcus between the control and HNSCC groups were no longer significant (p > 0.3). Patients with higher initial abundances of Porphyromonas (p = 0.012) and Fusobacterium (p = 0.017) had poorer outcomes, including recurrence, metastasis, and death. In contrast, disease-free patients had a higher abundance of Streptococcus (p = 0.004).

CONCLUSION

Oral microbiome dysbiosis was found in HNSCC patients. By the end of RT, the main initial differences in phylum and genus abundance observed at T0 between the control and HNSCC groups were no longer present. Higher abundances of Fusobacterium and Porphyromonas were associated with poor outcomes.

Bacteriome and mycobiome dysbiosis in oral mucosal dysplasia and oral cancer

It has long been considered that the oral microbiome is tightly connected to oral health and that dysbiotic changes can be detrimental to the occurrence and progression of dysplastic oral mucosal lesions or oral cancer. Improved understanding of the concepts of microbial dysbiosis together with advances in high-throughput molecular sequencing of these pathologies have charted in greater microbiological detail the nature of their clinical state. This review discusses the bacteriome and mycobiome associated with oral mucosal lesions, oral candidiasis, and oral squamous cell carcinoma, aiming to delineate the information available to date in pursuit of advancing diagnostic and prognostic utilities for oral medicine.

Roles of intralesional bacteria in the initiation and progression of oral squamous cell carcinoma

BACKGROUND

Oral squamous cell carcinoma (OSCC) is the predominant form of head and neck cancer, often diagnosed at late stages, resulting in a poor prognosis. Recent studies indicate a potential association between OSCC and microbial presence. Microorganisms have been identified in various tumors and lesions, including OSCC and oral potentially malignant disorders (OPMDs). Intralesional microbiota are considered important components of the tumor microenvironment (TME) and may contribute to carcinogenesis.

METHODS

Sources were collected through thorough searches of databases PubMed and Embase. The review focused on microbial characteristics, potential origins, and their impact on cancer progression.

RESULTS

Bacteria display varying abundance and diversity throughout the stages of OSCC and OPMDs. Intraleisional bacteria may have diverse sources, including not only oral plaque and saliva but also potentially the gut. Intralesional bacteria have both pro-carcinogenic and anti-carcinogenic effects, affecting processes like cell proliferation, invasion, and immune response.

CONCLUSIONS

Intralesional microbiota are crucial in OSCC and OPMDs, influencing both disease progression and treatments. Despite their significance, challenges like inconsistent sampling and microbial identification remain. Future research is required to fully understand their role and improve clinical applications.

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 oral microbiome and oral and upper gastrointestinal diseases

Background

Microbiomes are essential components of the human body, and their populations are substantial. Under normal circumstances, microbiomes coexist harmoniously with the human body, but disturbances in this equilibrium can lead to various diseases. The oral microbiome is involved in the occurrence and development of many oral and gastrointestinal diseases. This review focuses on the relationship between oral microbiomes and oral and upper gastrointestinal diseases, and therapeutic strategies aiming to provide valuable insights for clinical prevention and treatment.

Methods

To identify relevant studies, we conducted searches in PubMed, Google Scholar, and Web of Science using keywords such as "oral microbiome," "oral flora, " "gastrointestinal disease, " without any date restrictions. Subsequently, the retrieved publications were subject to a narrative review.

Results

In this review, we found that oral microbiomes are closely related to oral and gastrointestinal diseases such as periodontitis, dental caries, reflux esophagitis, gastritis, and upper gastrointestinal tumors (mainly the malignant ones). Oral samples like saliva and buccal mucosa are not only easy to collect, but also display superior sample stability compared to gastrointestinal tissues. Consequently, analysis of the oral microbiome could potentially serve as an efficient preliminary screening method for high-risk groups before undergoing endoscopic examination. Besides, treatments based on the oral microbiomes could aid early diagnosis and treatment of these diseases.

Conclusions

Oral microbiomes are essential to oral and gastrointestinal diseases. Therapies centered on the oral microbiomes could facilitate the early detection and management of these conditions.

Prevalence of oral Capnocytophaga species and their association with dental plaque accumulation and periodontal inflammation in middle‑aged and older people

Capnocytophaga species are commonly found in human oral microbiome. The aim of the present study was to understand the association of the prevalence of oral Capnocytophaga species with oral hygiene and periodontal inflammation. A total of 136 patients (median age 72 years) who visited the Hiroshima University Hospital (Hiroshima, Japan) between April 2021 and June 2023 were enrolled. Swab samples were obtained from the tongue surface. DNA from Capnocytophaga species (C. ochracea and C. sputigena) was detected by real-time PCR analysis. Dental plaque accumulation was observed to assess the oral hygiene condition of participants. Additionally, clinical periodontal inflammation was assessed with periodontal inflamed surface area (PISA) scores. Clinical confounding factors such as age, sex, lifestyle-related disease, remaining teeth and denture wearing between Capnocytophaga species-positive and -negative groups were adjusted with a propensity score matching method. Mann-Whitney U and χ2 or Fisher's exact test were employed for statistical analysis. The prevalence rate was 67.6% for oral C. ochracea and 83.1% for C. sputigena. C. ochracea-positive participants showed significantly higher plaque control record scores (an indicator of dental plaque accumulation) than C. ochracea-negative participants (P=0.03). Additionally, C. ochracea/C. sputigena dual-positive participants exhibited significantly higher plaque control record and PISA scores than non-dual-positive participants (P=0.01 and P=0.04, respectively). Propensity score matching was conducted in the C. ochracea/C. sputigena dual-positive group and the non-dual-positive group for adjustment of clinical factors, resulting in 51 matched patient pairs. C. ochracea/C. sputigena dual-positive participants had significantly higher plaque control record scores than non-dual-positive participants (P=0.02). The present results suggest that the prevalence of both oral C. ochracea and C. sputigena is associated with poor oral hygiene in middle-aged and older people.

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.

The role of intratumoral microorganisms in the progression and immunotherapeutic efficacy of head and neck cancer

The effectiveness of cancer immunization is largely dependent on the tumor’s microenvironment, especially the tumor immune microenvironment. Emerging studies say microbes exist in tumor cells and immune cells, suggesting that these microbes can affect the state of the immune microenvironment of the tumor. Our comprehensive review navigates the intricate nexus between intratumoral microorganisms and their role in tumor biology and immune modulation. Beginning with an exploration of the historical acknowledgment of microorganisms within tumors, the article underscores the evolution of the tumor microenvironment (TME) and its subsequent implications. Using findings from recent studies, we delve into the unique bacterial compositions across different tumor types and their influence on tumor growth, DNA damage, and immune regulation. Furthermore, we illuminate the potential therapeutic implications of targeting these intratumoral microorganisms, emphasizing their multifaceted roles from drug delivery agents to immunotherapy enhancers. As advancements in next-generation sequencing (NGS) technology redefine our understanding of the tumor microbiome, the article underscores the importance of discerning their precise role in tumor progression and tailoring therapeutic interventions. The review culminates by emphasizing ongoing challenges and the pressing need for further research to harness the potential of intratumoral microorganisms in cancer care.

Fusobacterium nucleatum subsp. polymorphum recovered from malignant and potentially malignant oral disease exhibit heterogeneity in adhesion phenotypes and adhesin gene copy number, shaped by inter-subspecies horizontal gene transfer and recombination-derived mosaicism

Fusobacterium nucleatum is an anaerobic commensal of the oral cavity associated with periodontitis and extra-oral diseases, including colorectal cancer. Previous studies have shown an increased relative abundance of this bacterium associated with oral dysplasia or within oral tumours. Using direct culture, we found that 75 % of Fusobacterium species isolated from malignant or potentially malignant oral mucosa were F. nucleatum subsp. polymorphum. Whole genome sequencing and pangenome analysis with Panaroo was carried out on 76 F. nucleatum subsp. polymorphum genomes. F. nucleatum subsp. polymorphum was shown to possesses a relatively small core genome of 1604 genes in a pangenome of 7363 genes. Phylogenetic analysis based on the core genome shows the isolates can be separated into three main clades with no obvious genotypic associations with disease. Isolates recovered from healthy and diseased sites in the same patient are generally highly related. A large repertoire of adhesins belonging to the type V secretion system (TVSS) could be identified with major variation in repertoire and copy number between strains. Analysis of intergenic recombination using fastGEAR showed that adhesin complement is shaped by horizontal gene transfer and recombination. Recombination events at TVSS adhesin genes were not only common between lineages of subspecies polymorphum, but also between different subspecies of F. nucleatum. Strains of subspecies polymorphum with low copy numbers of TVSS adhesin encoding genes tended to have the weakest adhesion to oral keratinocytes. This study highlights the genetic heterogeneity of F. nucleatum subsp. polymorphum and provides a new framework for defining virulence in this organism.

Capnocytophaga gingivalis is a potential tumor promotor in oral cancer

OBJECTIVES

To investigate the role of oral microbiome in promoting oral squamous cell carcinoma (OSCC) development.

MATERIALS AND METHODS

We investigated the salivary microbiome of 108 controls and 70 OSCC cases by16S rRNA gene sequencing and detected the fluorescence signal of OSCC-related pathological bacteria by fluorescence in situ hybridization assay (FISH). The invasion and migration assays were used to show the differences of invasive and migrative abilities between control and experimental groups. Quantitative real-time PCR and Western blotting were used to verify the epithelial-to-mesenchymal transition (EMT).

RESULTS

In our study, the overall microbiome abundance and composition were richer in the 108 controls than in the 70 OSCC cases. We demonstrated that Streptococcus, Capnocytophaga, Peptostreptococcus, and Lactobacillus were highly abundant in the saliva of OSCC patients by 16S rDNA sequencing and FISH. Moreover, we found that Capnocytophaga gingivalis (C. gingivalis) was highly presented in OSCC tissues by FISH. We focused on C. gingivalis and found that its supernatant induced OSCC cells to undergo EMT, causing the cells to acquire a mesenchymal phenotype associated with highly invasive and metastatic properties.

CONCLUSION

Taken together, these results indicated that C. gingivalis might invade OSCC tissues and played an important role in OSCC by promoting OSCC invasion and metastasis by inducing EMT. Hence, the role of C. gingivalis in cancer progression revealed a new direction for the research of OSCC.

The Microbiome Modulates the Immune System to Influence Cancer Therapy

The gut microbiota composition can affect the tumor microenvironment and its interaction with the immune system, thereby having implications for treatment predictions. This article reviews the studies available to better understand how the gut microbiome helps the immune system fight cancer. To describe this fact, different mechanisms and approaches utilizing probiotics to improve advancements in cancer treatment will be discussed. Moreover, not only calorie intake but also the variety and quality of diet can influence cancer patients' immunotherapy treatment because dietary patterns can impair immunological activities either by stimulating or suppressing innate and adaptive immunity. Therefore, it is interesting and critical to understand gut microbiome composition as a biomarker to predict cancer immunotherapy outcomes and responses. Here, more emphasis will be given to the recent development in immunotherapies utilizing microbiota to improve cancer therapies, which is beneficial for cancer patients.

Identification of consensus head and neck cancer-associated microbiota signatures: a systematic review and meta-analysis of 16S rRNA and The Cancer Microbiome Atlas datasets

Introduction. Multiple reports have attempted to describe the tumour microbiota in head and neck cancer (HNSC).Gap statement. However, these have failed to produce a consistent microbiota signature, which may undermine understanding the importance of bacterial-mediated effects in HNSC.Aim. The aim of this study is to consolidate these datasets and identify a consensus microbiota signature in HNSC.Methodology. We analysed 12 published HNSC 16S rRNA microbial datasets collected from cancer, cancer-adjacent and non-cancer tissues to generate a consensus microbiota signature. These signatures were then validated using The Cancer Microbiome Atlas (TCMA) database and correlated with the tumour microenvironment phenotypes and patient's clinical outcome.Results. We identified a consensus microbial signature at the genus level to differentiate between HNSC sample types, with cancer and cancer-adjacent tissues sharing more similarity than non-cancer tissues. Univariate analysis on 16S rRNA datasets identified significant differences in the abundance of 34 bacterial genera among the tissue types. Paired cancer and cancer-adjacent tissue analyses in 16S rRNA and TCMA datasets identified increased abundance in Fusobacterium in cancer tissues and decreased abundance of Atopobium, Rothia and Actinomyces in cancer-adjacent tissues. Furthermore, these bacteria were associated with different tumour microenvironment phenotypes. Notably, high Fusobacterium signature was associated with high neutrophil (r=0.37, P<0.0001), angiogenesis (r=0.38, P<0.0001) and granulocyte signatures (r=0.38, P<0.0001) and better overall patient survival [continuous: HR 0.8482, 95 % confidence interval (CI) 0.7758-0.9273, P=0.0003].Conclusion. Our meta-analysis demonstrates a consensus microbiota signature for HNSC, highlighting its potential importance in this disease.

The Roles and Interactions of Porphyromonas gingivalis and Fusobacterium nucleatum in Oral and Gastrointestinal Carcinogenesis: A Narrative Review

Epidemiological studies have spotlighted the intricate relationship between individual oral bacteria and tumor occurrence. Porphyromonas gingivalis and Fusobacteria nucleatum, which are known periodontal pathogens, have emerged as extensively studied participants with potential pathogenic abilities in carcinogenesis. However, the complex dynamics arising from interactions between these two pathogens were less addressed. This narrative review aims to summarize the current knowledge on the prevalence and mechanism implications of P. gingivalis and F. nucleatum in the carcinogenesis of oral squamous cell carcinoma (OSCC), colorectal cancer (CRC), and pancreatic ductal adenocarcinoma (PDAC). In particular, it explores the clinical and experimental evidence on the interplay between P. gingivalis and F. nucleatum in affecting oral and gastrointestinal carcinogenesis. P. gingivalis and F. nucleatum, which are recognized as keystone or bridging bacteria, were identified in multiple clinical studies simultaneously. The prevalence of both bacteria species correlated with cancer development progression, emphasizing the potential impact of the collaboration. Regrettably, there was insufficient experimental evidence to demonstrate the synergistic function. We further propose a hypothesis to elucidate the underlying mechanisms, offering a promising avenue for future research in this dynamic and evolving field.

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.

Potential role of epithelial-mesenchymal transition induced by periodontal pathogens in oral cancer

With the increasing incidence of oral cancer in the world, it has become a hotspot to explore the pathogenesis and prevention of oral cancer. It has been proved there is a strong link between periodontal pathogens and oral cancer. However, the specific molecular and cellular pathogenic mechanisms remain to be further elucidated. Emerging evidence suggests that periodontal pathogens-induced epithelial-mesenchymal transition (EMT) is closely related to the progression of oral cancer. Cells undergoing EMT showed increased motility, aggressiveness and stemness, which provide a pro-tumour environment and promote malignant metastasis of oral cancer. Plenty of studies proposed periodontal pathogens promote carcinogenesis via EMT. In the current review, we discussed the association between the development of oral cancer and periodontal pathogens, and summarized various mechanisms of EMT caused by periodontal pathogens, which are supposed to play an important role in oral cancer, to provide targets for future research in the fight against oral cancer.

Interactions Between Oral Microbiota and Cancers in the Aging Community: A Narrative Review

The oral microbiome potentially wields significant influence in the development of cancer. Within the human oral cavity, an impressive diversity of more than 700 bacterial species resides, making it the second most varied microbiome in the body. This finely balanced oral microbiome ecosystem is vital for sustaining oral health. However, disruptions in this equilibrium, often brought about by dietary habits and inadequate oral hygiene, can result in various oral ailments like periodontitis, cavities, gingivitis, and even oral cancer. There is compelling evidence that the oral microbiome is linked to several types of cancer, including oral, pancreatic, colorectal, lung, gastric, and head and neck cancers. This review discussed the critical connections between cancer and members of the human oral microbiota. Extensive searches were conducted across the Web of Science, Scopus, and PubMed databases to provide an up-to-date overview of our understanding of the oral microbiota's role in various human cancers. By understanding the possible microbial origins of carcinogenesis, healthcare professionals can diagnose neoplastic diseases earlier and design treatments accordingly.

Compositional and functional changes in the salivary microbiota related to oral leukoplakia and oral squamous cell carcinoma: a case control study

BACKGROUND

Oral squamous cell carcinoma (OSCC) is one of the most common malignant tumours with increasing incidence, and oral leukoplakia (OLK) has a strong tendency to undergo malignant transformation. The oral microbiota may influence oral cancer progression, but the salivary bacterial composition and functional changes in OSCC and OLK have not been comprehensively elucidated. Therefore, we compared salivary bacteria in OLK and OSCC patients with healthy controls (HC).

METHODS

Metagenomic sequencing was used to compare the bacterial composition and functional changes of 18 OSCC patients, 21 OLK patients and 21 HC. Spearman correlation was used to identify possible associations between functions and bacteria.

RESULTS

Gemella was the most differentially enriched genus in OSCC. At the species level, Streptococcus sp. NPS 308, Streptococcus agalactiae, Gemella haemolysans and Gemella morbillorum were slightly increased in OLK and OSCC. Kyoto Encyclopedia of Genes and Genomes (KEGG) results showed that OSCC was mainly associated with metabolism functions, including lipid metabolism, carbohydrate metabolism and glycan biosynthesis and metabolism. The synthesis and degradation of ketone bodies, cysteine and methionine metabolism and glycerolipid metabolism differed significantly among the three groups, and were highest in OSCC and lowest in HC. And G. haemolysans was significantly associated with these selected metabolic pathways.

CONCLUSIONS

Metagenomic analysis revealed significant differences in the salivary microbiota among OSCC, OLK and HC. Thus, salivary microbiota composition and functional changes may be associated with OSCC progression. Metabolism of nonessential amino acids such as cysteine and methionine in bacteria may play an important role in oral oncogenesis, and more studies of the mechanism between metabolisms of bacteria and oral oncogenesis are needed in the future.

Real-Time PCR Detection of Candida Species in Biopsy Samples from Non-Smokers with Oral Dysplasia and Oral Squamous Cell Cancer: A Retrospective Archive Study

The impact of Candida sp. in the development of oral cancer remains uncertain and requires sensitive analytical approaches for clarification. Given the invasive capabilities of these microorganisms in penetrating and invading host tissues through hyphal invasion, this study sought to detect the presence of five Candida sp. in oral biopsy tissue samples from non-smoker patients. Samples were obtained from patients at varying stages of oral carcinogenesis, including dysplasia, carcinoma in situ, OSCC, and histologically benign lesions, and analyzed using Real-Time PCR. Oral tissue samples from 80 patients (46 males and 34 females) were included. Significantly higher C. albicans presence was detected in the mild/moderate dysplasia group compared to the healthy (p = 0.001), carcinoma in situ (p = 0.031) and OSCC groups (p = 0.000). Similarly, C. tropicalis carriage was higher in tissues with mild/moderate dysplasia compared to healthy (p = 0.004) and carcinoma in situ (p = 0.019). Our results showed a significant increase in the presence of C. albicans and C. tropicalis within the mild/moderate dysplasia group compared to other cohorts. Coexistence of these two microorganisms was observed, suggesting a potential transition from a commensal state to an opportunistic pathogen, which could be particularly linked to the onset of oral neoplasia.

The emerging role of oral microbiota in oral cancer initiation, progression and stemness

Oral squamous cell carcinoma (OSCC) is the most prevalent malignancy among the Head and Neck cancer. OSCCs are highly inflammatory, immune-suppressive, and aggressive tumors. Recent sequencing based studies demonstrated the involvement of different oral microbiota in oral cavity diseases leading OSCC carcinogenesis, initiation and progression. Researches showed that oral microbiota can activate different inflammatory pathways and cancer stem cells (CSCs) associated stemness pathways for tumor progression. We speculate that CSCs and their niche cells may interact with the microbiotas to promote tumor progression and stemness. Certain oral microbiotas are reported to be involved in dysbiosis, pre-cancerous lesions, and OSCC development. Identification of these specific microbiota including Human papillomavirus (HPV), Porphyromonas gingivalis (PG), and Fusobacterium nucleatum (FN) provides us with a new opportunity to study the bacteria/stem cell, as well as bacteria/OSCC cells interaction that promote OSCC initiation, progression and stemness. Importantly, these evidences enabled us to develop in-vitro and in-vivo models to study microbiota interaction with stem cell niche defense as well as CSC niche defense. Thus in this review, the role of oral microbiota in OSCC has been explored with a special focus on how oral microbiota induces OSCC initiation and stemness by modulating the oral mucosal stem cell and CSC niche defense.

Mapping the Scientific Landscape of Bacterial Influence on Oral Cancer: A Bibliometric Analysis of the Last Decade's Medical Progress

The research domain investigating bacterial factors in the development of oral cancer from January 2013 to December 2022 was examined with a bibliometric analysis. A bibliometric analysis is a mathematical and statistical method used to examine extensive datasets. It assesses the connections between prolific authors, journals, institutions, and countries while also identifying commonly used keywords. A comprehensive search strategy identified 167 relevant articles, revealing a progressive increase in publications and citations over time. China and the United States were the leading countries in research productivity, while Harvard University and the University of Helsinki were prominent affiliations. Prolific authors such as Nezar Al-Hebshi, Tsute Chen, and Yaping Pan were identified. The analysis also highlights the contributions of different journals and identifies the top 10 most cited articles in the field, all of which focus primarily on molecular research. The article of the highest citation explored the role of a Fusobacterium nucleatum surface protein in tumor immune evasion. Other top-cited articles investigated the correlation between the oral bacteriome and cancer using 16S rRNA amplicon sequencing, showing microbial shifts associated with oral cancer development. The functional prediction analysis used by recent studies has further revealed an inflammatory bacteriome associated with carcinogenesis. Furthermore, a keyword analysis reveals four distinct research themes: cancer mechanisms, periodontitis and microbiome, inflammation and Fusobacterium, and risk factors. This analysis provides an objective assessment of the research landscape, offers valuable information, and serves as a resource for researchers to advance knowledge and collaboration in the search for the influence of bacteria on the prevention, diagnosis, and treatment of oral cancer.

Detecting salivary host and microbiome RNA signature for aiding diagnosis of oral and throat cancer

OBJECTIVE

Oral squamous cell carcinoma (OSCC) and oropharyngeal squamous cell carcinoma (OPSCC) can go undetected resulting in late detection and poor outcomes. We describe the development and validation of CancerDetect for Oral & Throat cancer™ (CDOT), to detect markers of OSCC and/or OPSCC within a high-risk population.

MATERIAL AND METHODS

We collected saliva samples from 1,175 individuals who were 50 years or older, or adults with a tobacco use history. 945 of those were used to train a classifier using machine learning methods, resulting in a salivary microbial and human metatranscriptomic signature. The classifier was then independently validated on the 230 remaining samples prospectively collected and unseen by the classifier, consisting of 20 OSCC (all stages), 76 OPSCC (all stages), and 134 negatives (including 14 pre-malignant).

RESULTS

On the validation cohort, the specificity of the CDOT test was 94 %, sensitivity was 90 % for participants with OSCC, and 84.2 % for participants with OPSCC. Similar classification results were observed among people in early stage (stages I & II) vs late stage (stages III & IV).

CONCLUSIONS

CDOT is a non-invasive test that can be easily administered in dentist offices, primary care centres and specialised cancer clinics for early detection of OPSCC and OSCC. This test, having received FDA's breakthrough designation for accelerated review, has the potential to enable early diagnosis, saving lives and significantly reducing healthcare expenditure.

Inflammatory response-related genes predict prognosis in patients with HNSCC

BACKGROUND

Head and neck squamous cell carcinoma (HNSCC) is the most common malignancy of the head and neck, and the inflammatory microenvironment can impact the prognosis of HNSCC. However, the contribution of inflammation to tumour progression has not been fully elucidated.

METHODS

The mRNA expression profiles and corresponding clinical data of HNSCC patients were downloaded from The Cancer Genome Atlas (TCGA) database. The least absolute shrinkage and selection operator (LASSO) Cox analysis model was used to identify prognostic genes. The overall survival (OS) between high- and low-risk patients was compared by Kaplan‒Meier analysis. The independent predictors of OS were determined by univariate and multivariate Cox analyses. Single-sample gene set enrichment analysis (ssGSEA) was used to assess immune cell infiltration and immune-related pathway activity. GSEA was used to analyse Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. The Gene Expression Profiling Interactive Analysis (GEPIA) database was used to examine prognostic genes in HNSCC patients. Immunohistochemistry was used to verify the protein expression of prognostic genes in HNSCC samples.

RESULTS

An inflammatory response-related gene signature was constructed by LASSO Cox regression analysis. HNSCC patients in the high-risk group showed significantly reduced OS compared with those in the low-risk group. The predictive capacity of the prognostic gene signature was confirmed by ROC curve analysis. Multivariate Cox analysis revealed that the risk score was an independent predictor for OS. Functional analysis indicated that the immune status was markedly different between the two risk groups. The risk score was significantly related to tumour stage and immune subtype. The expression levels of the prognostic genes were significantly related to the sensitivity of cancer cells to antitumour drugs. Furthermore, high expression of the prognostic genes significantly predicted poor prognosis of HNSCC patients.

CONCLUSIONS

The novel signature containing 9 inflammatory response-related genes reflects the immune status of HNSCC and can be used for prognosis prediction. Furthermore, the genes may be potential targets for HNSCC treatment.

Alteration of oral bacteriome of smokeless tobacco users and their association with oral cancer

Smokeless tobacco (SLT) is certainly one of the major risk factors associated with oral cancer. Disruption of oral microbiota-host homeostasis contributes to the progression of oral cancer. Here, we profiled SLT users' oral bacterial composition and inferred their functions by sequencing 16S rDNA V₃-V₄ region and PICRUSt2, respectively. Oral bacteriome of SLT users (with or without oral premalignant lesions), SLT with alcohol co-users, and non-SLT consumers were compared. Oral bacteriome is shaped primarily by SLT use and the incidence of oral premalignant lesions (OPL). A significantly increased bacterial α-diversity was monitored in SLT users with OPL compared to in SLT users without OPL and non-users, whereas β-diversity was significantly explained by OPL status. Overrepresented genera were Prevotella, Fusobacterium, Veillonella, Haemophilus, Capnocytophaga, and Leptotrichia in SLT users having OPL. LEfSe analysis identified 16 genera as a biomarker that were differentially abundant in SLT users having OPL. The functional prediction of genes significantly increased for several metabolic pathways, more importantly, were nitrogen metabolism, nucleotide metabolism, energy metabolism, and biosynthesis/biodegradation of secondary metabolites in SLT users having OPL. Furthermore, HPV-16 and EBV, but not HPV-18, were considerably connected with the SLT users having OPL. Overall, this study provides evidence that SLT utilization and OPL development are associated with oral bacteriome dysbiosis indicating the enrichment of bacterial species known for their contribution to oral carcinogenesis. Therefore, delineating the cancer-inducing bacterial population in SLT users will facilitate the future development of microbiome-targeted therapies. KEY POINTS: • SLT consumption significantly elevates oral bacterial diversity. • Prevalent significant genera are Prevotella, Veillonella, and Haemophilus in SLT users with OPL. • SLT promotes the occurrence of the cancer-inducing bacterial population.

Integrative Metatranscriptomic Analysis Reveals Disease-specific Microbiome-host Interactions in Oral Squamous Cell Carcinoma

Studies on the microbiome of oral squamous cell carcinoma (OSCC) have been limited to 16S rRNA gene sequencing. Here, laser microdissection coupled with brute-force, deep metatranscriptome sequencing was employed to simultaneously characterize the microbiome and host transcriptomes and predict their interaction in OSCC. The analysis involved 20 HPV16/18-negative OSCC tumor/adjacent normal tissue pairs (TT and ANT) along with deep tongue scrapings from 20 matched healthy controls (HC). Standard bioinformatic tools coupled with in-house algorithms were used to map, analyze, and integrate microbial and host data. Host transcriptome analysis identified enrichment of known cancer-related gene sets, not only in TT versus ANT and HC, but also in the ANT versus HC contrast, consistent with field cancerization. Microbial analysis identified a low abundance yet transcriptionally active, unique multi-kingdom microbiome in OSCC tissues predominated by bacteria and bacteriophages. HC showed a different taxonomic profile yet shared major microbial enzyme classes and pathways with TT/ANT, consistent with functional redundancy. Key taxa enriched in TT/ANT compared with HC were Cutibacterium acnes, Malassezia restricta, Human Herpes Virus 6B, and bacteriophage Yuavirus. Functionally, hyaluronate lyase was overexpressed by C. acnes in TT/ANT. Microbiome-host data integration revealed that OSCC-enriched taxa were associated with upregulation of proliferation-related pathways. In a preliminary in vitro validation experiment, infection of SCC25 oral cancer cells with C. acnes resulted in upregulation of MYC expression. The study provides a new insight into potential mechanisms by which the microbiome can contribute to oral carcinogenesis, which can be validated in future experimental studies.

Significance

Studies have shown that a distinct microbiome is associated with OSCC, but how the microbiome functions within the tumor interacts with the host cells remains unclear. By simultaneously characterizing the microbial and host transcriptomes in OSCC and control tissues, the study provides novel insights into microbiome-host interactions in OSCC which can be validated in future mechanistic studies.

Altered oral microbiome in Sudanese Toombak smokeless tobacco users carries a newly emerging risk of squamous cell carcinoma development and progression

There are an estimated 6-10 million smokeless tobacco (Toombak) users in Sudan, the majority being males. Toombak is known to be a carcinogenic product that is likely to modify the oral microbiome spatiality into a high-risk potential for the development and progression of oral cancer, but previous studies are lacking in this field. Here, we endeavour for the first time the exploration of the oral microbiome in key mucosal areas of the oral cavity and assess the microbiome variations in premalignant and oral squamous cell carcinoma (OSCC) samples from both users and non-users of Toombak. 16S rRNA sequencing was performed on DNA obtained from pooled saliva, oral mucosa and supragingival plaque from 78 Sudanese users and non-users of Toombak, aged between 20 and 70 years. In 32 of the pooled saliva samples, the mycobiome (fungal) environment was analysed through ITS sequencing. Then, 46 formalin-fixed paraffin-embedded samples of premalignant and OSCC samples were collected, and their associated microbiomes sequenced. The oral Sudanese microbiome was found to be enriched in Streptococcaceae, but Staphylococcaceae were significantly more abundant amongst Toombak users. Genera enriched in the oral cavity of Toombak users included Corynebacterium_1 and Cardiobacterium while in non-users, Prevotella, Lactobacillus and Bifidobacterium were prominent. Aspergillus was the most abundant fungus in the mouths of Toombak users with a marked loss of Candida. The genus Corynebacterium_1 was abundant in the buccal, floor of the mouth and saliva microbiomes as well as in oral cancer samples from Toombak users indicating a possible role for this genus in the early stages of oral cancer development. An oral cancer microbiome that favours poor survival and metastasis in those who use Toombak also emerged that includes the genera Stenotrophomonas and Schlegelella. Those utilising Toombak carry an altered oral microbiome that may be an additional risk factor for this products carcinogenicity to the oral structures. These significant microbiome modulations are a newly emerging key driving factor in oral cancer development and progression in Toombak users while it is also shown that Toombak users carry an oral cancer microbiome that may increase the potential for a poorer prognosis.

Molecular insights into the role of electronic cigarettes in oral carcinogenesis

Electronic cigarette (EC) usage or vaping has seen a significant rise in recent years across various parts of the world. They have been publicized as a safe alternative to smoking; however, this is not supported strongly by robust research evidence. Toxicological analysis of EC liquid and aerosol has revealed presence of several toxicants with known carcinogenicity. Oral cavity is the primary site of exposure of both cigarette smoke and EC aerosol. Role of EC in oral cancer is not as well-researched as that of traditional smoking. However, several recent studies have shown that it can lead to a wide range of potentially carcinogenic molecular events in oral cells. This review delineates the oral carcinogenesis potential of ECs at the molecular level, providing a summary of the effects of EC usage on cancer therapy resistance, cancer stem cells (CSCs), immune evasion, and microbiome dysbiosis, all of which may lead to increased tumor malignancy and poorer patient prognosis. This review of literature indicates that ECs may not be as safe as they are perceived to be, however further research is needed to definitively determine their oncogenic potential.

Exploring the microbiome of oral epithelial dysplasia as a predictor of malignant progression

A growing body of research associates the oral microbiome and oral cancer. Well-characterized clinical samples with outcome data are required to establish relevant associations between the microbiota and disease. The objective of this study was to characterize the community variations and the functional implications of the microbiome in low-grade oral epithelial dysplasia (OED) using 16S rRNA gene sequencing from annotated archival swabs in progressing (P) and non-progressing (NP) OED. We characterised the microbial community in 90 OED samples - 30 swabs from low-grade OED that progressed to cancer (cases) and 60 swabs from low-grade OED that did not progress after a minimum of 5 years of follow up (matched control subjects). There were small but significant differences between P and NP samples in terms of alpha diversity as well as beta diversity in conjunction with other clinical factors such as age and smoking status for both taxa and functional predictions. Across all samples, the most abundant genus was Streptococcus, followed by Haemophilus, Rothia, and Neisseria. Taxa and predicted functions were identified that were significantly differentially abundant with progression status (all Ps and NPs), when samples were grouped broadly by the number of years between sampling and progression or in specific time to progression for Ps only. However, these differentially abundant features were typically present only at low abundances. For example, Campylobacter was present in slightly higher abundance in Ps (1.72%) than NPs (1.41%) and this difference was significant when Ps were grouped by time to progression. Furthermore, several of the significantly differentially abundant functions were linked to the Campylobacteraceae family in Ps and may justify further investigation. Larger cohort studies to further explore the microbiome as a potential biomarker of risk in OED are warranted.

On the Oral Microbiome of Oral Potentially Malignant and Malignant Disorders: Dysbiosis, Loss of Diversity, and Pathogens Enrichment

The role of dysbiosis in the development and progression of oral potentially malignant disorders (OPMDs) remains largely unknown. Here, we aim to characterize and compare the oral microbiome of homogeneous leucoplakia (HL), proliferative verrucous leukoplakia (PVL), oral squamous cell carcinoma (OSCC), and OSCC preceded by PVL (PVL-OSCC). Fifty oral biopsies from HL (n = 9), PVL (n = 12), OSCC (n = 10), PVL-OSCC (n = 8), and healthy (n = 11) donors were obtained. The sequence of the V3-V4 region of the 16S rRNA gene was used to analyze the composition and diversity of bacterial populations. In the cancer patients, the number of observed amplicon sequence variants (ASVs) was lower and Fusobacteriota constituted more than 30% of the microbiome. PVL and PVL-OSCC patients had a higher abundance of Campilobacterota and lower Proteobacteria than any other group analyzed. A penalized regression was performed to determine which species were able to distinguish groups. HL is enriched in Streptococcus parasanguinis, Streptococcus salivarius, Fusobacterium periodonticum, Prevotella histicola, Porphyromonas pasteri, and Megasphaera micronuciformis; PVL is enriched in Prevotella salivae, Campylobacter concisus, Dialister pneumosintes, and Schaalia odontolytica; OSCC is enriched in Capnocytophaga leadbetteri, Capnocytophaga sputigena, Capnocytophaga gingivalis, Campylobacter showae, Metamycoplasma salivarium, and Prevotella nanceiensis; and PVL-OSCC is enriched in Lachnospiraceae bacterium, Selenomonas sputigena, and Prevotella shahii. There is differential dysbiosis in patients suffering from OPMDs and cancer. To the best of our knowledge, this is the first study comparing the oral microbiome alterations in these groups; thus, additional studies are needed.

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.

Modifiable risk factors for oral cavity cancer in non-smokers: A systematic review and meta-analysis

BACKGROUND

Oral cavity cancer (OCC) is traditionally associated with smoking, but there is an increasing prevalence of the disease among non-smokers. This review investigates possible modifiable risk factors in the development of OCC in non-smokers (OCCNS).

METHODS

PubMed, EMBASE, Web of Science, and Scopus were searched for publications prior to June 2021. Comparative studies investigating modifiable OCCNS risk factors were identified following PRISMA guidelines. Publication date, population size, and results were indexed. Study quality was assessed using MINORS (Methodological Index for Non-Randomized Studies). Factors examined by multiple studies were analyzed using random-effect meta-analysis framework.

RESULTS

Literature search resulted in 1,625 unique publications. 52 records met inclusion criterion, investigating alcohol (n = 22), chewing products (n = 18), diet (n = 7), dental health (n = 11), and medical comorbidities (n = 6).

CONCLUSION

This review demonstrates the paucity of large studies investigating OCCNS risk factors. Further investigation is warranted to help clinicians risk-stratify patients without traditional risk factors.

F. nucleatum facilitates oral squamous cell carcinoma progression via GLUT1-driven lactate production

BACKGROUND

Tumor-resident microbiota has been documented for various cancer types. Oral squamous cell carcinoma (OSCC) is also enriched with microbiota, while the significance of microbiota in shaping the OSCC microenvironment remains elusive.

METHODS

We used bioinformatics and clinical sample analysis to explore relationship between F. nucleatum and OSCC progression. Xenograft tumor model, metabolic screening and RNA sequencing were performed to elucidate mechanisms of pro-tumor role of F. nucleatum.

FINDINGS

We show that a major protumorigenic bacterium, F. nucleatum, accumulates in invasive margins of OSCC tissues and drives tumor-associated macrophages (TAMs) formation. The mechanistic dissection shows that OSCC-resident F. nucleatum triggers the GalNAc-Autophagy-TBC1D5 signaling, leading to GLUT1 aggregation in the plasma membrane and the deposition of extracellular lactate. Simultaneous functional inhibition of GalNAc and GLUT1 efficiently reduces TAMs formation and restrains OSCC progression.

INTERPRETATION

These findings suggest that tumor-resident microbiota affects the immunomodulatory and protumorigenic microenvironment via modulating glycolysis and extracellular lactate deposition. The targeted intervention of this process could provide a distinct clinical strategy for patients with advanced OSCC.

FUNDING

This work was supported by the National Natural Science Foundation of China for Key Program Projects (82030070, to LC) and Distinguished Young Scholars (31725011, to LC), as well as Innovation Team Project of Hubei Province (2020CFA014, to LC).

Current understanding of the intratumoral microbiome in various tumors

It is estimated that in the future, the number of new cancer cases worldwide will exceed the 19.3 million recorded in 2020, and the number of deaths will exceed 10 million. Cancer remains the leading cause of human mortality and lagging socioeconomic development. Intratumoral microbes have been revealed to exist in many cancer types, including pancreatic, colorectal, liver, esophageal, breast, and lung cancers. Intratumoral microorganisms affect not only the host immune system, but also the effectiveness of tumor chemotherapy. This review concentrates on the characteristics and roles of intratumoral microbes in various tumors. In addition, the potential of therapies targeting intratumoral microbes, as well as the main challenges currently delaying these therapies, are explored. Furthermore, we briefly summarize existing technical methods used to characterize intratumoral microbes. We hope to provide ideas for exploring intratumoral microbes as potential biomarkers and targets for tumor diagnosis, treatment, and prognostication.

The significant clinical correlation of the intratumor oral microbiome in oral squamous cell carcinoma based on tissue-derived sequencing

Background: The microbiota is a critical component of the complex human microenvironment, impacting various physiological processes and disease development via the microbe-host interaction. In particular, the oral microbiota profoundly affects tumor development and progression. There is increasing evidence that oral microbiota is associated with the development of oral cancer, especially oral squamous cell carcinoma (OSCC). Methods: We comprehensively analyzed the oral microbiota in 133 OSCC samples worldwide. Subsequently, we evaluated the microbial compositions between OSCC patients and healthy people and their correlation with clinical parameters. The value of the oral microbiota as a diagnostic and prognostic biomarker was also determined. Results: This study found differences in critical oral microbiota between OSCC and normal controls. The most notable differences are present in p_Firmicutes, p_Actinobacteria, c_Fusobacteriia, o_Fusobacteriales, f_Fusobacteriaceae, and g_Fusobacterium. All six-level oral microorganisms were also associated with the clinical characteristics of OSCC, particularly with the clinical outcomes (survival time and status). We developed a predictive model based on this. We found that five different oral microorganisms have high confidence and can be used for clinical diagnosis and prognostic prediction, except for p_Actinobacteria. Conclusion: This study revealed that the intratumor oral microbiota of OSCC patients worldwide and the microbial signatures of OSCC patients possess similar properties in different regions, further refining the shortcomings of the current research field. We revealed that the oral microbiota could be used as a biomarker to reflect human health and disease progression status. This will provide new directions for tumor microbiome research. This means we can develop strategies through diet, probiotics, and antibiotics for cancer prevention and treatment.

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.

Influence of site and smoking on malignant transformation in the oral cavity: Is the microbiome the missing link?

The tongue and floor of the mouth are high-risk sites for oral squamous cell carcinoma (OSCC), while smoking is its most significant risk factor. Recently, questions have been raised as to the role of the oral microbiome in OSCC because of a wealth of evidence demonstrating that the microbiome of OSCC differs from that of healthy mucosa. However, oral site and smoking also have a significant impact on oral microbial communities, and to date, the role these factors play in influencing the dysbiotic microbial communities of OSCC and precursor lesions has not been considered. This review aims to examine the influence of site and smoking on the oral microbiome and, in turn, whether these microbiome changes could be involved in oral carcinogenesis.

Changes in the oral and nasal microbiota in pediatric obstructive sleep apnea

Background

Several clinical studies have demonstrated that pediatric obstructive sleep apnea (OSA) is associated with dysbiosis of airway mucosal microbiota. However, how oral and nasal microbial diversity, composition, and structure are altered in pediatric OSA has not been systemically explored.

Methods

30 polysomnography-confirmed OSA patients with adenoid hypertrophy, and 30 controls who did not have adenoid hypertrophy, were enrolled. Swabs from four surface oral tissue sites (tongue base, soft palate, both palatine tonsils, and adenoid) and one nasal swab from both anterior nares were collected. The 16S ribosomal RNA (rRNA) V3-V4 region was sequenced to identify the microbial communities.

Results

The beta diversity and microbial profiles were significantly different between pediatric OSA patients and controls at the five upper airway sites. The abundances of Haemophilus, Fusobacterium, and Porphyromonas were higher at adenoid and tonsils sites of pediatric patients with OSA. Functional analysis revealed that the differential pathway between the pediatric OSA patients and controls involved glycerophospholipids and amino acid metabolism.

Conclusions

In this study, the oral and nasal microbiome of pediatric OSA patients exhibited certain differences in composition compared with the controls. However, the microbiota data could be useful as a reference for studies on the upper airway microbiome.