The early diagnosis and monitoring of squamous cell carcinoma via saliva metabolomics

Identification and molecular characterization of propionylcholinesterase, a novel pseudocholinesterase in rice

Cholinesterase is consisting of acetylcholinesterase (AChE) and pseudocholinesterase in vertebrates and invertebrates. AChE gene has been identified in several plant species, while pseudocholinesterase gene has not yet been found in any plant species. In this study, we report that the AChE gene paralog encodes propionylcholinesterase (PChE), a pseudocholinesterase in rice. PChE was found to be located adjacent to AChE (Os07g0586200) on rice chromosome 7 and designated as Os07g0586100. Phylogenetic tree analysis showed a close relationship between rice AChE and PChE. PChE-overexpressing rice had higher hydrolytic activity toward propionylthiocholine than acetylthiocholine and showed extremely low activity against butyrylthiocholine. Therefore, the PChE gene product was characterized as a propionylcholinesterase, a pseudocholinesterase. The rice PChE displayed lower sensitivity to the cholinesterase inhibitor, neostigmine bromide, than electric eel, maize, and rice AChEs. The recombinant PChE functions as a 171 kDa homotetramer. PChE was expressed during the later developmental stage, and it was found be localized in the extracellular spaces of the rice leaf tissue. These results suggest that the rice plant possesses PChE, which functions in the extracellular spaces at a later developmental stage. To the best of our knowledge, this study provides the first direct evidence and molecular characterization of PChE in plants.

Identification of Possible Salivary Metabolic Biomarkers and Altered Metabolic Pathways in South American Patients Diagnosed with Oral Squamous Cell Carcinoma

Oral squamous cell carcinoma (OSCC) represents 90% of oral malignant neoplasms. The search for specific biomarkers for OSCC is a very active field of research contributing to establishing early diagnostic methods and unraveling underlying pathogenic mechanisms. In this work we investigated the salivary metabolites and the metabolic pathways of OSCC aiming find possible biomarkers. Salivary metabolites samples from 27 OSCC patients and 41 control individuals were compared through a gas chromatography coupled to a mass spectrometer (GC-MS) technique. Our results allowed identification of pathways of the malate-aspartate shuttle, the beta-alanine metabolism, and the Warburg effect. The possible salivary biomarkers were identified using the area under receiver-operating curve (AUC) criterion. Twenty-four metabolites were identified with AUC > 0.8. Using the threshold of AUC = 0.9 we find malic acid, maltose, protocatechuic acid, lactose, 2-ketoadipic, and catechol metabolites expressed. We notice that this is the first report of salivary metabolome in South American oral cancer patients, to the best of our knowledge. Our findings regarding these metabolic changes are important in discovering salivary biomarkers of OSCC patients. However, additional work needs to be performed considering larger populations to validate our results.

Salivary Metabolomics for Diagnosis and Monitoring Diseases: Challenges and Possibilities

Saliva is a useful biological fluid and a valuable source of biological information. Saliva contains many of the same components that can be found in blood or serum, but the components of interest tend to be at a lower concentration in saliva, and their analysis demands more sensitive techniques. Metabolomics is starting to emerge as a viable method for assessing the salivary metabolites which are generated by the biochemical processes in elucidating the pathways underlying different oral and systemic diseases. In oral diseases, salivary metabolomics has concentrated on periodontitis and oral cancer. Salivary metabolites of systemic diseases have been investigated mostly in the early diagnosis of different cancer, but also neurodegenerative diseases. This mini-review article aims to highlight the challenges and possibilities of salivary metabolomics from a clinical viewpoint. Furthermore, applications of the salivary metabolic profile in diagnosis and prognosis, monitoring the treatment success, and planning of personalized treatment of oral and systemic diseases are discussed.

Mass spectrometry in the lipid study of cancer

Introduction: Cancer is a heterogeneous disease that exploits various metabolic pathways to meet the demand for increased energy and structural components. Lipids are biomolecules that play essential roles as high energy sources, mediators, and structural components of biological membranes. Accumulating evidence has established that altered lipid metabolism is a hallmark of cancer.Areas covered: Mass spectrometry (MS) is a label-free analytical tool that can simultaneously identify and quantify hundreds of analytes. To date, comprehensive lipid studies exclusively rely on this technique. Here, we reviewed the use of MS in the study of lipids in various cancers and discuss its instrumental limitations and challenges.Expert opinion: MS and MS imaging have significantly contributed to revealing altered lipid metabolism in a variety of cancers. Currently, a single MS approach cannot profile the entire lipidome because of its lack of sensitivity and specificity for all lipid classes. For the metabolic pathway investigation, lipid study requires the integration of MS with other molecular approaches. Future developments regarding the high spatial resolution, mass resolution, and sensitivity of MS instruments are warranted.

Metabolomics of Oral/Head and Neck Cancer

Oral/head and neck cancer is the sixth most common human malignancies in the world. Despite the treatment advances in surgery, chemotherapy, and radiotherapy, the patient survival has not been significantly improved in the past several decades. As a new methodological approach, metabolomics may help reveal the metabolic reprogramming mechanisms underlying head and neck cancer cell proliferation, invasion, and metastasis and may be used to identify metabolite biomarkers for clinical applications of the disease. In this chapter, we briefly review recent metabolomic applications in head and neck cancer.

Unraveling the Microbial Mechanisms Underlying the Psychobiotic Potential of a Bifidobacterium breve Strain

SCOPE

The antidepressant-like effect of psychobiotics has been observed in both pre-clinical and clinical studies, but the molecular mechanisms of action are largely unclear. To address this, the psychobiotic strain Bifidobacterium breve CCFM1025 is investigated for its genomic features, metabolic features, and gut microbial and metabolic modulation effect.

METHODS AND RESULTS

Unlike B. breve FHLJDQ3M5, CCFM1025 significantly decreases the chronically stressed mice's depressive-like behaviors and neurological abnormalities. CCFM1025 has more genes encoding glycoside hydrolases (GHs) when comparing to FHLJDQ3M5's genome, which means CCFM1025 has a superior carbohydrate utilization capacity and living adaptivity in the gut. CCFM1025 also produces higher levels of neuromodulatory metabolites, including hypoxanthine, tryptophan, and nicotinate. The administration of CCFM1025 reshapes the gut microbiome of chronically stressed mice. It results in higher cecal xanthine, tryptophan, short-chain fatty acid levels, and enhances fatty acid and tryptophan biosynthesis capability in the gut-brain interaction (identified by in silico analyses) than FHLJDQ3M5-treated mice.

CONCLUSIONS

Genomic and metabolic features involving GHs and neuromodulatory metabolites may determine the antidepressant-like effect of B. breve CCFM1025. Psychobiotics' characterization in this manner may provide guidelines for developing novel psychopharmacological agents in the future.

MicroRNA-363-3p inhibits tumor cell proliferation and invasion in oral squamous cell carcinoma cell lines by targeting SSFA2

The aim of the present study was to evaluate the expression levels of microRNA (miR)-363-3p and its underlying physiological function in oral squamous cell carcinoma (OSCC). miR-363-3p expression levels were measured in OSCC cell lines using reverse transcription-quantitative PCR. The role of miR-363-3p in OSCC cells was examined using gain-of-function assays in vitro. Cell proliferation was assessed using Cell Counting Kit-8, 5-ethynyl-2'-deoxyuridine assays and flow cytometry. Cell migration and invasion were evaluated in wound-healing and Transwell Matrigel assays. In addition, bioinformatics analysis predicted binding sites of miR-363-3p on sperm-specific antigen 2 (SSFA2). Luciferase reporter and RNA pull-down assays were conducted to test whether miR-363-3p interacted with SSFA2. miR-363-3p expression was downregulated in OSCC cell lines compared with that in the normal epithelial cell line (NHOK). Additionally, miR-363-3p overexpression suppressed OSCC cell proliferation, migration and invasion in vitro. SSFA2 was verified as a direct target of miR-363-3p, and SSFA2 overexpression partially counteracted the inhibitory effects of miR-363-3p on cell proliferation, migration and invasion in OSCC cell lines. Thus, miR-363-3p may serve as a tumor suppressor via targeting SSFA2 and may represent a potential therapeutic target for OSCC.

Systematic evaluation of sample preparation strategy for GC-MS-based plasma metabolomics and its application in osteoarthritis

Sample preparation plays a crucial part in plasma metabolomics. In order to obtain an optimal sample extraction method for gas chromatography mass spectrometry (GC-MS)-based plasma metabolomics, five different extraction strategies including protein precipitation, liquid-liquid extraction and solid-phase extraction were evaluated systematically for both plasma untargeted- and targeted-metabolomics. The comprehensive evaluation revealed that the all-in-one sample preparation method, MeOH-MTBE-H₂O (1:5:1.5, v/v/v), was the optimal extraction method for both untargeted- and targeted-metabolomics. Next, the optimal sample preparation protocol was applied in plasma metabolomics of osteoarthritis (OA). A panel containing cholesterol, lactic acid, stearic acid, alpha-tocopherol and oxalic acid was selected as candidate biomarker to distinguish OA patients from healthy controls (HC) based on the support vector machine (SVM) classification model. The discriminating capability of the candidate biomarker panel was further validated successfully with logistic regression and principal components analysis (PCA) analysis. Therefore, the panel could potentially act as diagnostic biomarker for osteoarthritis.

Salivary metabolomics for cancer detection

Introduction: Saliva is an ideal biofluid that can be collected in a noninvasive manner, enabling safe and frequent screening of various diseases. Recent studies have revealed that salivary metabolomics analysis has the potential to detect both oral and systemic cancers. Area covered: We reviewed the technical aspects, as well as applications, of salivary metabolomics for cancer detection. The topics include the effects of preconditioning and the method of sample collection, sample storage, processing, measurement, data analysis, and validation of the results. We also examined the rational relationship between salivary biomarkers and tumors distant from the oral cavity. A strategy to establish standard operating protocols for obtaining reproducible quantification data is also discussed Expert opinion: Salivary metabolomics reflects oral and systematic health status, which potently enables cancer detection. The sensitivity and specificity of each marker and their combinations have been well evaluated, but a validation study is required. Further, the standard operating protocol for each procedure should be established to obtain reproducible data before clinical usage.

Metabolic landscape of oral squamous cell carcinoma

BACKGROUND

Head and neck cancers are the seventh most common type of cancer worldwide, with almost half of the cases affecting the oral cavity. Oral squamous cell carcinoma (OSCC) is the most common form of oral cancer, showing poor prognosis and high mortality. OSCC molecular pathogenesis is complex, resulting from a wide range of events that involve the interplay between genetic mutations and altered levels of transcripts, proteins, and metabolites. Metabolomics is a recently developed sub-area of omics sciences focused on the comprehensive analysis of small molecules involved in several biological pathways by high throughput technologies.

AIM OF REVIEW

This review summarizes and evaluates studies focused on the metabolomics analysis of OSCC and oral premalignant disorders to better interpret the complex process of oral carcinogenesis. Additionally, the metabolic biomarkers signatures identified so far are also included. Moreover, we discuss the limitations of these studies and make suggestions for future investigations.

KEY SCIENTIFIC CONCEPTS

Although many questions about the metabolic features of OSCC have already been answered in metabolomic studies, further validation and optimization are still required to translate these findings into clinical applications.

Salivary metabolite levels in perinatally HIV-infected youth with periodontal disease

INTRODUCTION

Salivary metabolite profiles are altered in adults with HIV compared to their uninfected counterparts. Less is known about youth with HIV and how oral disorders that commonly accompany HIV infection impact salivary metabolite levels.

OBJECTIVE

As part of the Adolescent Master Protocol multi-site cohort study of the Pediatric HIV/AIDS Cohort Study (PHACS) network we compared the salivary metabolome of youth with perinatally-acquired HIV (PHIV) and youth HIV-exposed, but uninfected (PHEU) and determined whether metabolites differ in PHIV versus PHEU.

METHODS

We used three complementary targeted and discovery-based liquid chromatography-tandem mass spectrometry (LC-MS/MS) workflows to characterize salivary metabolite levels in 20 PHIV and 20 PHEU youth with and without moderate periodontitis. We examined main effects associated with PHIV and periodontal disease, and the interaction between them.

RESULTS

We did not identify differences in salivary metabolite profiles that remained significant under stringent control for both multiple between-group comparisons and multiple metabolites. Levels of cadaverine, a known periodontitis-associated metabolite, were more abundant in individuals with periodontal disease with the difference being more pronounced in PHEU than PHIV. In the discovery-based dataset, we identified a total of 564 endogenous peptides in the metabolite extracts, showing that proteolytic processing and amino acid metabolism are important to consider in the context of HIV infection.

CONCLUSION

The salivary metabolite profiles of PHIV and PHEU youth were overall very similar. Individuals with periodontitis particularly among the PHEU youth had higher levels of cadaverine, suggesting that HIV infection, or its treatment, may influence the metabolism of oral bacteria.

Unravelling the Potential of Salivary Volatile Metabolites in Oral Diseases. A Review

Fostered by the advances in the instrumental and analytical fields, in recent years the analysis of volatile organic compounds (VOCs) has emerged as a new frontier in medical diagnostics. VOCs analysis is a non-invasive, rapid and inexpensive strategy with promising potential in clinical diagnostic procedures. Since cellular metabolism is altered by diseases, the resulting metabolic effects on VOCs may serve as biomarkers for any given pathophysiologic condition. Human VOCs are released from biomatrices such as saliva, urine, skin emanations and exhaled breath and are derived from many metabolic pathways. In this review, the potential of VOCs present in saliva will be explored as a monitoring tool for several oral diseases, including gingivitis and periodontal disease, dental caries, and oral cancer. Moreover, the analytical state-of-the-art for salivary volatomics, e.g., the most common extraction techniques along with the current challenges and future perspectives will be addressed unequivocally.

Signatures of Mucosal Microbiome in Oral Squamous Cell Carcinoma Identified Using a Random Forest Model

OBJECTIVE

The aim of this study was to explore the signatures of oral microbiome associated with OSCC using a random forest (RF) model.

PATIENTS AND METHODS

A total of 24 patients with OSCC were enrolled in the study. The oral microbiome was assessed in cancerous lesions and matched paracancerous tissues from each patient using 16S rRNA gene sequencing. Signatures of mucosal microbiome in OSCC were identified using a RF model.

RESULTS

Significant differences were found between OSCC lesions and matched paracancerous tissues with respect to the microbial profile and composition. Linear discriminant analysis effect size analyses (LEfSe) identified 15 bacteria genera associated with cancerous lesions. Fusobacterium, Treponema, Streptococcus, Peptostreptococcus, Carnobacterium, Tannerella, Parvimonas and Filifactor were enriched. A classifier based on RF model identified a microbial signature comprising 12 bacteria, which was capable of distinguishing cancerous lesions and paracancerous tissues (AUC = 0.82). The network of the oral microbiome in cancerous lesions appeared to be simplified and fragmented. Functional analyses of oral microbiome showed altered functions in amino acid metabolism and increased capacity of glucose utilization in OSCC.

CONCLUSION

The identified microbial signatures may potentially be used as a biomarker for predicting OSCC or for clinical assessment of oral cancer risk.

Oral squamous cell carcinoma diagnosed from saliva metabolic profiling

Saliva is a noninvasive biofluid that can contain metabolite signatures of oral squamous cell carcinoma (OSCC). Conductive polymer spray ionization mass spectrometry (CPSI-MS) is employed to record a wide range of metabolite species within a few seconds, making this technique appealing as a point-of-care method for the early detection of OSCC. Saliva samples from 373 volunteers, 124 who are healthy, 124 who have premalignant lesions, and 125 who are OSCC patients, were collected for discovering and validating dysregulated metabolites and determining altered metabolic pathways. Metabolite markers were reconfirmed at the primary tissue level by desorption electrospray ionization MS imaging (DESI-MSI), demonstrating the reliability of diagnoses based on saliva metabolomics. With the aid of machine learning (ML), OSCC and premalignant lesions can be distinguished from the normal physical condition in real time with an accuracy of 86.7%, on a person by person basis. These results suggest that the combination of CPSI-MS and ML is a feasible tool for accurate, automated diagnosis of OSCC in clinical practice.

Advanced diagnostic aids for oral cancer

Oral cancer, a universal malady, has become a stumbling block over the years due to its significant morbidity and mortality rates. The greater morbidity associated with this deadly disease is attributed to delay in its diagnosis / its presentation in advanced stage. Being multifactorial, Oral squamous cell carcinoma (OSCC) is the outcome of genetic and epigenetic instability. However, in many instances, oral cancer is preceded by precursor lesions named as oral potentially malignant disorders (OPMDs), the early detection of which makes it beneficial for patients with the possible increase in the productive longevity. Many diagnostic tools / aids have been explored with the aim of early detection of oral precancer and cancer. The basic chair-side procedures or relatively advanced aids come with a set of limitations along with subjectivity as one of the setbacks. The advent and exploitation of molecular techniques in the field of health diagnostics, is demanding the molecular typing of the OPMDs and also of oral cancer. The saga of various diagnostic aids for OSCC has witnessed the so-called latest trends such as lab-on-chip, microfluidics, nano diagnostics, liquid biopsy, omics technology and synthetic biology in early detection of oral precancer and cancer. Oral cancer being multifactorial in origin with the chief participation of altered genetics and epigenetics would demand high-end diagnostics for designing personalized therapy. Hence, the present paper highlights the role of various advanced diagnostic aids including 'omics' technology and synthetic biology in oral precancer and cancer.

Intraoral Microbial Metabolism and Association with Host Taste Perception

Metabolomics has been identified as a means of functionally assessing the net biological activity of a particular microbial community. Considering the oral microbiome, such an approach remains largely underused. While the current knowledge of the oral microbiome is constantly expanding, there are several deficits in knowledge particularly relating to their interactions with their host. This work uses nuclear magnetic resonance spectroscopy to investigate metabolic differences between oral microbial metabolism of endogenous (i.e., salivary protein) and exogenous (i.e., dietary carbohydrates) substrates. It also investigated whether microbial generation of different metabolites may be associated with host taste perception. This work found that in the absence of exogenous substrate, oral bacteria readily catabolize salivary protein and generate metabolic profiles similar to those seen in vivo. Important metabolites such as acetate, butyrate, and propionate are generated at relatively high concentrations. Higher concentrations of metabolites were generated by tongue biofilm compared to planktonic salivary bacteria. Thus, as has been postulated, metabolite production in proximity to taste receptors could reach relatively high concentrations. In the presence of 0.25 M exogenous sucrose, increased catabolism was observed with increased concentrations of a range of metabolites relating to glycolysis (lactate, pyruvate, succinate). Additional pyruvate-derived molecules such as acetoin and alanine were also increased. Furthermore, there was evidence that individual taste sensitivity to sucrose was related to differences in the metabolic fate of sucrose in the mouth. High-sensitivity perceivers appeared more inclined toward continual citric acid cycle activity postsucrose, whereas low-sensitivity perceivers had a more efficient conversion of pyruvate to lactate. This work collectively indicates that the oral microbiome exists in a complex balance with the host, with fluctuating metabolic activity depending on nutrient availability. There is preliminary evidence of an association between host behavior (sweet taste perception) and oral catabolism of sugar.

CD44 and associated markers in oral rinses and tissues from oral and oropharyngeal cancer patients

OBJECTIVES

Oral and oropharyngeal squamous cell carcinoma (OOPSCC) is a debilitating disease. Salivary rinses contain soluble tumor markers including CD44 (solCD44) and total protein (TP) that may aid detection and prognosis of these aggressive tumors. Here we aim to examine the relationship between these salivary biomarkers and tissue markers p16 and CD44 and determine whether these markers can predict progression-free survival (PFS) and overall survival (OS).

MATERIALS AND METHODS

Prospective study to update biomarkers using oral rinses and tissues from OOPSC patients enrolled between 2007 and 2012 at an academic tertiary referral center. 64 cases from a 300-subject case-control study with archived tissue for immunohistochemistry were included.

RESULTS

82.8% were male, 84.4% were ever smokers, 70.3% had disease stage T3-T4, and 57.8% presented with nodal disease. Nineteen patients (25%) were p16 positive. The group with strong tissue CD44 expression in membrane and cytoplasm had higher levels of solCD44 (mean 10.73 ng/ml) than other groups (5.47 ng/ml) (p = 0.033). TP levels were significantly reduced in oral rinses from subjects with p16 universal gross tumor tissue staining (mean 0.80 vs. 1.08 mg/ml; p = 0.039). On multivariate analysis, universal CD44 gross tissue staining and TP levels ≥ 1 mg/ml demonstrated poorer PFS, with the latter also affecting OS. Poorer survival was associated with soluble CD44 ≥ 5.33 ng/ml and TP ≥ 1 mg/ml.

CONCLUSIONS

Direct associations were found between high solCD44 levels and strong membrane and cytoplasmic CD44 expression, and between high TP levels and peripheral/mixed p16 gross staining. Poorer PFS and OS are significantly associated with higher levels of solCD44 and protein in oral rinses.

Salivary metabolites to detect patients with cancer: a systematic review

Novel adjunctive screening aids are needed to reduce the morbidity and mortality related to cancer, and every effort should be made for early diagnosis. This systematic review aimed to evaluate salivary metabolites and their diagnostic value in patients with cancer.The systematic review was performed in two phases and included studies that focused on the diagnostic value of salivary metabolites in humans with solid malignant neoplasms. Five electronic databases were searched, and the risk of bias in individual studies was evaluated using the revised Quality Assessment of Diagnostic Accuracy Studies criteria (QUADAS-2). All procedures were performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.Of the 1151 studies retrieved, 25 were included; 13 studies used targeted and 12 untargeted metabolomics approaches. Most studies included patients with breast and oral cancer. Except for one, all studies had case-control designs, and none fulfilled all quality assessments. Overall, 140 salivary metabolites were described. The most frequently reported metabolites were alanine, valine, and leucine. Among the 11 studies that reported diagnostic test accuracy (DTA) values, proline, threonine, and histidine in combination and monoacylglycerol alone demonstrated the highest DTA for breast cancer. Combined choline, betaine, pipecolinic acid, and L-carnitine showed better discriminatory performance for early oral cancer.This systematic review highlights the current evidence on salivary metabolites that may be used as a future strategy to diagnose cancer. Further studies including larger sample sizes with confirmation of the results by untargeted analysis are warranted.

Metabolic Biomarkers of Squamous Cell Carcinoma of the Aerodigestive Tract: A Systematic Review and Quality Assessment

Introduction. Aerodigestive squamous cell carcinomas (ASCC) constitute a major source of global cancer deaths. Patients typically present with advanced, incurable disease, so new means of detecting early disease are a research priority. Metabolite quantitation is amenable to point-of-care analysis and can be performed in ASCC surrogates such as breath and saliva. The purpose of this systematic review is to summarise progress of ASCC metabolomic studies, with an emphasis on the critical appraisal of methodological quality and reporting.

METHOD

A systematic online literature search was performed to identify studies reporting metabolic biomarkers of ASCC. This review was conducted in accordance with the recommendations of the Cochrane Library and MOOSE guidelines.

RESULTS

Thirty studies comprising 2117 patients were included in the review. All publications represented phase-I biomarker discovery studies, and none validated their findings in an independent cohort. There was heterogeneity in study design and methodological and reporting quality. Sensitivities and specificities were higher in oesophageal and head and neck squamous cell carcinomas compared to those in lung squamous cell carcinoma. The metabolic phenotypes of these cancers were similar, as was the kinetics of metabolite groups when comparing blood, tissue, and breath/saliva concentrations. Deregulation of amino acid metabolism was the most frequently reported theme.

CONCLUSION

Metabolite analysis has shown promising diagnostic performance, especially for oesophageal and head and neck ASCC subtypes, which are phenotypically similar. However, shortcomings in study design have led to inconsistencies between studies. To support future studies and ultimately clinical adoption, these limitations are discussed.

Salivary Metabolomics: From Diagnostic Biomarker Discovery to Investigating Biological Function

Metabolomic profiling of biofluids, e.g., urine, plasma, has generated vast and ever-increasing amounts of knowledge over the last few decades. Paradoxically, metabolomic analysis of saliva, the most readily-available human biofluid, has lagged. This review explores the history of saliva-based metabolomics and summarizes current knowledge of salivary metabolomics. Current applications of salivary metabolomics have largely focused on diagnostic biomarker discovery and the diagnostic value of the current literature base is explored. There is also a small, albeit promising, literature base concerning the use of salivary metabolomics in monitoring athletic performance. Functional roles of salivary metabolites remain largely unexplored. Areas of emerging knowledge include the role of oral host-microbiome interactions in shaping the salivary metabolite profile and the potential roles of salivary metabolites in oral physiology, e.g., in taste perception. Discussion of future research directions describes the need to begin acquiring a greater knowledge of the function of salivary metabolites, a current research direction in the field of the gut metabolome. The role of saliva as an easily obtainable, information-rich fluid that could complement other gastrointestinal fluids in the exploration of the gut metabolome is emphasized.

Analytical Strategies in Lipidomics for Discovery of Functional Biomarkers from Human Saliva

Human saliva is increasingly being used and validated as a biofluid for diagnosing, monitoring systemic disease status, and predicting disease progression. The discovery of biomarkers in saliva biofluid offers unique opportunities to bypass the invasive procedure of blood sampling by using oral fluids to evaluate the health condition of a patient. Saliva biofluid is clinically relevant since its components can be found in plasma. As salivary lipids are among the most essential cellular components of human saliva, there is great potential for their use as biomarkers. Lipid composition in cells and tissues change in response to physiological changes and normal tissues have a different lipid composition than tissues affected by diseases. Lipid imbalance is closely associated with a number of human lifestyle-related diseases, such as atherosclerosis, diabetes, metabolic syndromes, systemic cancers, neurodegenerative diseases, and infectious diseases. Thus, identification of lipidomic biomarkers or key lipids in different diseases can be used to diagnose diseases and disease state and evaluate response to treatments. However, further research is needed to determine if saliva can be used as a surrogate to serum lipid profiles, given that highly sensitive methods with low limits of detection are needed to discover salivary biomarkers in order to develop reliable diagnostic and disease monitoring salivary tests. Lipidomic methods have greatly advanced in recent years with a constant advance in mass spectrometry (MS) and development of MS detectors with high accuracy and high resolution that are able to determine the elemental composition of many lipids.

The Relevance of Mass Spectrometry Analysis for Personalized Medicine through Its Successful Application in Cancer "Omics"

Mass spectrometry (MS) is an essential analytical technology on which the emerging omics domains; such as genomics; transcriptomics; proteomics and metabolomics; are based. This quantifiable technique allows for the identification of thousands of proteins from cell culture; bodily fluids or tissue using either global or targeted strategies; or detection of biologically active metabolites in ultra amounts. The routine performance of MS technology in the oncological field provides a better understanding of human diseases in terms of pathophysiology; prevention; diagnosis and treatment; as well as development of new biomarkers; drugs targets and therapies. In this review; we argue that the recent; successful advances in MS technologies towards cancer omics studies provides a strong rationale for its implementation in biomedicine as a whole.

Regulation of succinate dehydrogenase and role of succinate in cancer

Succinate dehydrogenase (SDH) has been classically considered a mitochondrial enzyme with the unique property to participate in both the citric acid cycle and the electron transport chain. However, in recent years, several studies have highlighted the role of the SDH substrate, i.e. succinate, in biological processes other than metabolism, tumorigenesis being the most remarkable. For this reason, SDH has now been defined a tumor suppressor and succinate an oncometabolite. In this review, we discuss recent findings regarding alterations in SDH activity leading to succinate accumulation, which include SDH mutations, regulation of mRNA expression, post-translational modifications and endogenous SDH inhibitors. Further, we report an extensive examination of the role of succinate in cancer development through the induction of epigenetic and metabolic alterations and the effects on epithelial to mesenchymal transition, cell migration and invasion, and angiogenesis. Finally, we have focused on succinate and SDH as diagnostic markers for cancers having altered SDH expression/activity.

Evaluation of salivary metabolomics in oral leukoplakia and oral squamous cell carcinoma

BACKGROUND

Metabolomics is the study of metabolome which describes the full repertoire of small molecules, and the analysis of salivary metabolomics may help in identifying tumor-specific biomarkers for early diagnosis and prediction of tumor progression. The aim of the study was to evaluate the clinical utility of salivary metabolites in oral leukoplakia and oral squamous cell carcinoma.

METHODS

Salivary metabolomic profile of patients diagnosed with oral leukoplakia (n = 21) and oral squamous cell carcinoma (n = 22) was compared with apparently normal controls (n = 18) using Q-TOF-liquid chromatography-mass spectrometry. MassHunter profile software and Metlin database were used for metabolite identification. ANOVA to identify the regulation of metabolites between the three groups, t test (P < 0.05) to signify the changes between two groups, and chi-square test (P < 0.05) to indicate the presence or absence of metabolites in the study participants of the three groups were performed.

RESULTS

Significant upregulation of 1-methylhistidine, inositol 1,3,4-triphosphate, d-glycerate-2-phosphate, 4-nitroquinoline-1-oxide, 2-oxoarginine, norcocaine nitroxide, sphinganine-1-phosphate, and pseudouridine in oral leukoplakia and OSCC was noted. Downregulated compounds in the diseased groups included l-homocysteic acid, ubiquinone, neuraminic acid, and estradiol valerate.

CONCLUSION

A range of salivary metabolites were significantly altered in oral leukoplakia and oral squamous cell carcinoma. Further, it is necessary to evaluate the clinical utility of the individual metabolites in preventing malignant transformation of oral leukoplakia and to improve prognosis of oral squamous cell carcinoma.

Metabolomics study of oral cancers

BACKGROUND

Oral cancer is one of the most frequently occurring cancers. Metabolic reprogramming is an important hallmark of cancer. Metabolomics characterizes all the small molecules in a biological sample, and a complete set of small molecules in such sample is referred as metabolome. Nuclear magnetic resonance spectroscopy and mass spectrometry are two widely used techniques in metabolomics studies. Increasing evidence demonstrates that metabolomics techniques can be used to explore the metabolic signatures in oral cancer. Elucidation of metabolic alterations in oral cancer is also important for the understanding of its pathological mechanisms.

AIM OF REVIEW

In this paper, we summarize the latest progress of metabolomics study in oral cancer and provide the suggestions for the future studies.

KEY SCIENTIFIC CONCEPTS OF REVIEW

The metabolomics studies in saliva, serum, and tumor tissues revealed the existence of metabolic signatures in bio-fluids and tissues of oral cancer, and several tumor-specific metabolites identified in individual study could discriminate oral cancer from healthy controls or precancerous lesions, which are potential biomarkers for the screening or early diagnosis of oral cancer. Metabolomics study of oral cancers in the future should aim to establish a routine procedure with high sensitivity, profile intracellular metabolites to find out the metabolic characteristics of tumor cells, and investigate the mechanism behind metabolomic alterations and the metabolic response of cancer cells to chemotherapy.

Non-invasive metastasis prognosis from plasma metabolites in stage II colorectal cancer patients: The DACHS study

Metastasis is the main cause of death from colorectal cancer (CRC). About 20% of stage II CRC patients develop metastasis during the course of disease. We performed metabolic profiling of plasma samples from non-metastasized and metachronously metastasized stage II CRC patients to assess the potential of plasma metabolites to serve as biomarkers for stratification of stage II CRC patients according to metastasis risk. We compared the metabolic profiles of plasma samples prospectively obtained prior to metastasis formation from non-metastasized vs. metachronously metastasized stage II CRC patients of the German population-based case-control multicenter DACHS study retrospectively. Plasma samples were analyzed from stage II CRC patients for whom follow-up data including the information on metachronous metastasis were available. To identify metabolites distinguishing non-metastasized from metachronously metastasized stage II CRC patients robust supervised classifications using decision trees and support vector machines were performed and verified by 10-fold cross-validation, by nested cross-validation and by traditional validation using training and test sets. We found that metabolic profiles distinguish non-metastasized from metachronously metastasized stage II CRC patients. Classification models from decision trees and support vector machines with 10-fold cross-validation gave average accuracy of 0.75 (sensitivity 0.79, specificity 0.7) and 0.82 (sensitivity 0.85, specificity 0.77), respectively, correctly predicting metachronous metastasis in stage II CRC patients. Taken together, plasma metabolic profiles distinguished non-metastasized and metachronously metastasized stage II CRC patients. The classification models consisting of few metabolites stratify non-invasively stage II CRC patients according to their risk for metachronous metastasis.

1H-NMR spectroscopy identifies potential biomarkers in serum metabolomic signatures for early stage esophageal squamous cell carcinoma

BACKGROUND

Esophageal squamous cell carcinoma (ESCC) is one of the most prevalent types of upper gastrointestinal malignancies. Here, we used ¹H nuclear magnetic resonance spectroscopy (¹H-NMR) to identify potential serum biomarkers in patients with early stage ESCC.

METHODS

Sixty-five serum samples from early stage ESCC patients (n = 25) and healthy controls (n = 40) were analysed using ¹H-NMR spectroscopy. We distinguished between different metabolites through principal component analysis, partial least squares-discriminant analysis, and orthogonal partial least squares-discriminant analysis (OPLS-DA) using SIMCA-P+ version 14.0 software. Receiver operating characteristic (ROC) analysis was conducted to verify potential biomarkers.

RESULTS

Using OPLS-DA, 31 altered serum metabolites were successfully identified between the groups. Based on the area under the ROC curve (AUROC), and the biomarker panel with AUROC of 0.969, six serum metabolites (α-glucose, choline, glutamine, glutamate, valine, and dihydrothymine) were selected as potential biomarkers for early stage ESCC. Dihydrothymine particularly was selected as a new feasible biomarker associated with tumor occurrence.

CONCLUSIONS

¹H-NMR spectroscopy may be a useful tumour detection approach in identifying useful metabolic ESCC biomarkers for early diagnosis and in the exploration of the molecular pathogenesis of ESCC.

Periostin serves an important role in the pathogenesis of oral squamous cell carcinoma

The mechanism underlying OSCC tumorigenesis remains unclear. Periostin is considered to be a prominent oncogene in various solid tumors, although its precise role in OSCC progression remains unknown. In the present study, periostin expression was examined in surgical specimens of OSCC cases, and the results were analyzed for possible correlations with clinical characteristics. In addition, the proliferation and invasiveness of OSCC cells were evaluated following transfection with a Periostin small interfering RNA or an overexpression plasmid. The results revealed that periostin levels were significantly higher in patients with OSCC as compared with those in the controls (P<0.05). In addition, periostin levels in patients with OSCC were significantly associated with permeation classification. Furthermore, periostin expression was observed to promote the proliferation and invasiveness of OSCC cells. The present results suggest that periostin is significantly involved in the pathogenesis of OSCC.

A comparative profiling of oral cancer patients and high risk niswar users using FT-IR and chemometric analysis

Oral cancer is one of the major cancer types, which has increased sustainably in Southeast Asian countries due to the extensive use of a variety of tobacco and betel nut products. The current study is focused on developing an easy, efficient and cost-effective method for plasma profiling of oral cancer patients and tobacco users in order to have a progressive picture towards oral cancer. For this purpose, the profiling of 147 plasma samples including 67 oral cancer patients' samples, 60 "niswar" (a dipping tobacco product) user samples, and 20 healthy controls using attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR), and chemometric analysis was carried out. Fingerprint region (500-1500 cm^-1) of all three groups showed interesting variations in peaks pattern. From these observations, height ratios of two bands H1646/H1550 and H1080/H1024 with p value of 2.01 × 10^-6 and 8.39 × 10^-7, respectively, showed a pattern between healthy to oral cancer and "niswar" user samples. Chemometric analysis of the data showed a clean separation among the groups. PLS-DA and OPLS-DA models provided 87.7% and 89.5% classification rate, respectively. Area under the curve (AUC) for healthy control, oral cancer and "niswar" users were found to be 0.97, 0.95 and 0.92%, respectively. The results of the present study indicate that FT-IR spectroscopy, in conjunction with chemometric data, can be effectively used for the preliminary differentiation of plasma samples of oral cancer patients, "niswar" users and control samples of healthy persons.

Effective early detection of oral cancer using a simple and inexpensive point of care device in oral rinses

INTRODUCTION

Head and neck cancer remains a challenging disease that is increasing in incidence with the majority of patients diagnosed at an advanced stage where 5-year survival is approximately 50%. Current approaches including oral-brush biopsies, fluorescence-based technologies,  and salivary molecular profiling have demonstrated some success; however, cost, ease of use, and accuracy remain limiting factors. Areas covered: This is a profile of a novel, easy to use oral rinse point-of-care (POC) test to aid in the diagnosis of oral and oropharyngeal cancer. Background science related to the challenge of oral and oropharyngeal cancer and natural history of diagnostic aids for this disease are provided. Results of studies performed for validation of a POC and laboratory test are also discussed. Expert commentary: The POC test has been validated through a case : control clinical study and a prospective European trial, using version 1.0 (v1.0), which have demonstrated consistent performance including a > 90% negative predictive value, with a sensitivity of 80%. The assay was designed to identify malignant lesions in the oral cavity and oropharynx by improving upon standard clinical assessment.

Salivary metabolite profiling distinguishes patients with oral cavity squamous cell carcinoma from normal controls

Oral cavity squamous cell carcinoma (OCC) and oropharyngeal squamous cell carcinoma (OPC) are among the most common cancers worldwide and are associated with high mortality and morbidity. The purpose of this study is to identify potential biomarkers to distinguish OCC/OPC from normal controls and to distinguish OCC patients with and without nodal metastasis. We tested saliva samples from 101 OCC, 58 OPC, and 35 normal controls using four analytical platforms (NMR, targeted aqueous by LC-MS/MS, global aqueous and global lipidomics by LC-Q-TOF). Samples from OCC and normal controls were divided into discovery and validation sets. Using linear regression adjusting for age, sex, race and experimental batches, we found the levels of two metabolites (glycine and proline) to be significantly different between OCC and controls (FDR < 0.1 for both discovery and validation sets) but did not find any appreciable differences in metabolite levels between OPC and controls or between OCC with and without nodal metastasis. Four metabolites, including glycine, proline, citrulline, and ornithine were associated with early stage OCC in both discovery and validation sets. Further study is warranted to confirm these results in the development of salivary metabolites as diagnostic markers.

Preanalytical Processing and Biobanking Procedures of Biological Samples for Metabolomics Research: A White Paper, Community Perspective (for "Precision Medicine and Pharmacometabolomics Task Group"-The Metabolomics Society Initiative)

BACKGROUND

The metabolome of any given biological system contains a diverse range of low molecular weight molecules (metabolites), whose abundances can be affected by the timing and method of sample collection, storage, and handling. Thus, it is necessary to consider the requirements for preanalytical processes and biobanking in metabolomics research. Poor practice can create bias and have deleterious effects on the robustness and reproducibility of acquired data.

CONTENT

This review presents both current practice and latest evidence on preanalytical processes and biobanking of samples intended for metabolomics measurement of common biofluids and tissues. It highlights areas requiring more validation and research and provides some evidence-based guidelines on best practices.

SUMMARY

Although many researchers and biobanking personnel are familiar with the necessity of standardizing sample collection procedures at the axiomatic level (e.g., fasting status, time of day, "time to freezer," sample volume), other less obvious factors can also negatively affect the validity of a study, such as vial size, material and batch, centrifuge speeds, storage temperature, time and conditions, and even environmental changes in the collection room. Any biobank or research study should establish and follow a well-defined and validated protocol for the collection of samples for metabolomics research. This protocol should be fully documented in any resulting study and should involve all stakeholders in its design. The use of samples that have been collected using standardized and validated protocols is a prerequisite to enable robust biological interpretation unhindered by unnecessary preanalytical factors that may complicate data analysis and interpretation.

Salivary biomarkers and proteomics: future diagnostic and clinical utilities

Saliva testing is a non-invasive and inexpensive test that can serve as a source of information useful for diagnosis of disease. As we enter the era of genomic technologies and -omic research, collection of saliva has increased. Recent proteomic platforms have analysed the human salivary proteome and characterised about 3000 differentially expressed proteins and peptides: in saliva, more than 90% of proteins in weight are derived from the secretion of three couples of "major" glands; all the other components are derived from minor glands, gingival crevicular fluid, mucosal exudates and oral microflora. The most common aim of proteomic analysis is to discriminate between physiological and pathological conditions. A proteomic protocol to analyze the whole saliva proteome is not currently available. It is possible distinguish two type of proteomic platforms: top-down proteomics investigates intact naturally-occurring structure of a protein under examination; bottom-up proteomics analyses peptide fragments after pre-digestion (typically with trypsin). Because of this heterogeneity, many different biomarkers may be proposed for the same pathology. The salivary proteome has been characterised in several diseases: oral squamous cell carcinoma and oral leukoplakia, chronic graft-versus-host disease Sjögren's syndrome and other autoimmune disorders such as SAPHO, schizophrenia and bipolar disorder, and genetic diseases like Down's Syndrome and Wilson disease. The results of research reported herein suggest that in the near future human saliva will be a relevant diagnostic fluid for clinical diagnosis and prognosis.

Tissue metabolomic profiling to reveal the therapeutic mechanism of reduning injection on LPS-induced acute lung injury rats

Acute lung injury (ALI) is a severe respiratory disease. To date, no medical interventions have been proven effective in improving the outcome. Reduning injection (RDN) showed a potential effect in the therapy of ALI. However, seldom does research concern the holistic pharmacological mechanisms of RDN on ALI. A metabolomic strategy, based on two consecutive extractions of the lung tissue, has been developed to investigate therapeutic mechanisms of RDN on ALI model rat. The extraction procedure was an aqueous extraction with methanol-water followed by organic extraction with dichloromethane-methanol. According to the lipophilicity of extracts, aqueous extracts were analyzed on the T3 column and organic extracts on the C18 column. Partial least-squares discriminant analysis was utilized to identify differences in metabolic profiles of rats. A total of 14 potential biomarkers in lung tissue were identified, which mainly related to phospholipid metabolism, sphingolipid metabolism, nucleotide metabolism and energy metabolism. The combined analytical method provides complementary metabolomics information for exploring the action mechanism of RDN against ALI. And the obtained results indicate metabolomics is a promising tool for understanding the holism and synergism of traditional Chinese medicine.

Salivary biomarkers for oral cancer and pre-cancer screening: a review

OBJECTIVE

The objective of the study was to conduct a systematic review of the literature assessing potential salivary biomarkers of oral cancer and pre-cancer and discuss emerging issues and challenges in relation to oral cancer and pre-cancer diagnostics.

MATERIALS AND METHODS

Search for articles involved the Medline, PubMed, and EMBASE. Specific terms were used from January 1995 to March 2017 by three experts.

RESULTS

This search collected 270 articles, of which 105 articles such as reviews, case reports, news, letter to editor, etc. in first round and 117 articles such as publications in other languages than English, non-human studies, etc. were excluded. The remaining 48 articles considered analyzing whole saliva as well as specific gland saliva. Thirty-one studies considered oral stimuli such as eating, drinking, and oral hygiene practices for varied periods of time prior to sample collection. The time of collection of saliva was morning in most studies, but the exact time of collection was not mentioned. Three studies showed to have evaluated the whole saliva without centrifugation. Two-dimensional gel electrophoresis and tandem mass spectrometry were the most commonly used methods. Most of the potential salivary biomarkers of oral cancer are salivary proteins.

CONCLUSION

Combination approach of salivary biomarkers could be used as screening tool to improve early detection and diagnostic precision of oral pre-cancer and cancer.

CLINICAL RELEVANCE

The current findings are of importance for clinicians and researchers to mitigate the challenges in salivary-based diagnosis of oral cancer and to evaluate reliable, specific, and sensitive salivary biomarkers for oral pre-cancer and cancer diagnosis.

Salivary miRNA panel to detect HPV-positive and HPV-negative head and neck cancer patients

Head and neck squamous cell carcinomas (HNSCC) are a heterogeneous group of tumours that originate predominantly from the oral cavity, pharynx and larynx. Our aim was to determine whether salivary miRNA expression levels can diagnose these cancer subtypes. Saliva samples were collected from healthy controls (n=113, smoker and non-smokers), HPV-positive (n=54) and HPV-negative (n=47) HNSCC patients. The miRNA expression levels in saliva was quantified using qPCR. The potential of salivary miRNAs to discriminate these groups of patients was evaluated using multiple logistic regression with ROC analysis and a 10-fold cross-validation analysis. Salivary miRNA-9, -127, -134, -191, -222 and -455 were shown to discriminate a control group from a HPV-negative HNSCC patient group with a sensitivity of 60% and a specificity of 94%; whilst salivary miRNA-9,-134, -196b, -210, and -455 were the most parsimonious subset discriminating a control group from a HPV-positive HNSCC group, with a sensitivity of 65% and a specificity of 95%. Furthermore, miRNA-9, -134, -196b, -210 and -455 as a panel, was the most parsimonious subset to discriminate HPV-positive HNSCC patients from HPV-negative HNSCC patients. In addition, the expression levels of miRNA-9, -127, -196a, -196b, -210, -222 and -455 were significantly increased in the saliva collected from early stage HNSCC patients compared to controls. A future multi-centre confirmatory study is warranted to test the diagnostic performance of these salivary miRNA prior to clinical implementation.

Is Lipidomic the Answer to the Search of a Biomarker for Organ Preservation Protocol in Head and Neck Squamous Cell Carcinoma?

In the last decade organ preservation protocols based on chemoradiotherapy (CRT) has been showing the possibility of preserving function without jeopardizing survival for locally advanced head and neck squamous cell carcinoma (HNSCC). Still, only a percentage of the patients will benefit from this approach and, to date, no biomarkers are known to correctly predict these patients. More recently, modern mass spectrometry method has been used to determine metabolic profiles, and lipidomics, in particular, emerged as a new field of study in oncology and other diseases. This study aimed to analyze the lipid profile on saliva from patients undergoing to a prospective, single center, open-label, non-randomized phase II trial for organ preservation on HNSCC. The lipid analysis was performed using matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS). Multivariate statistical analyses based on principal component analysis and orthogonal partial least square-discriminant analysis were applied to MALDI-TOF-MS data to visualize differences between the lipid profiles and identify potential biomarkers. The results assisted on distinguishing complete responders from non-responders to the treatment protocol. In conclusion, we demonstrated that a group of lipids is differentially abundant in saliva from HNSCC patients submitted to an organ preservation protocol, being able to differentiate responders from non-responders. These results suggest the potential use of lipid biomarkers to identify patients who may benefit from this treatment. Also, we showed that saliva testing might be routinely used in clinical practice, for being a non-invasive alternative to blood testing, besides inexpensive and easy to obtain.

Phytosphingosine exhibits an anti-epithelial-mesenchymal transition function by the inhibition of EGFR signaling in human breast cancer cells

The lack of effective anti-metastatic drugs for the eradication of breast cancer stem cells within tumors, which are often resistant to chemotherapy and radiotherapy, creates a major obstacle during metastatic breast cancer therapy. Although D-ribo-phytosphingosine (PHS) is well known to activate protein kinase (MAPK)-mediated apoptosis, its possible role towards the metastasis signaling mechanisms underlying the epithelial-mesenchymal transition (EMT) remains largely unknown. In this report, we investigate the anti-metastatic potential of the natural sphingolipid PHS for the targeting of breast cancer cells as well as breast stem-like cells in vitro. We showed that PHS led to suppression of migratory potential, spheroid formation, CD44^high/CD24^low subpopulation as well as stem cell- and EMT-associated protein expression in basal type highly malignant breast cancer cell lines. In addition, PHS-based inhibition of EMT was attributable to the downregulation of the EGFR/JAK1/STAT3 signaling axis, as validated by immunoprecipitation assays and breast tumorigenesis mice models. This study demonstrate that PHS can target metastatic tumors with dual specificity (EMT and cancer stem-like cells) and therefore may be serve as a promising candidate for breast cancer treatments.

High-resolution microbiome profiling uncovers Fusobacterium nucleatum, Lactobacillus gasseri/johnsonii, and Lactobacillus vaginalis associated to oral and oropharyngeal cancer in saliva from HPV positive and HPV negative patients treated with surgery and chemo-radiation

Microbiome studies show altered microbiota in head and neck squamous cell carcinoma (HNSCC), both in terms of taxonomic composition and metabolic capacity. These studies utilized a traditional bioinformatics methodology, which allows for accurate taxonomic assignment down to the genus level, but cannot accurately resolve species level membership. We applied Resphera Insight, a high-resolution methodology for 16S rRNA taxonomic assignment that is able to provide species-level context in its assignments of 16S rRNA next generation sequencing (NGS) data.

Resphera Insight applied to saliva samples from HNSCC patients and healthy controls led to the discovery that a subset of HNSCC saliva samples is significantly enriched with commensal species from the vaginal flora, including Lactobacillus gasseri/johnsonii (710x higher in saliva) and Lactobacillus vaginalis (52x higher in saliva). These species were not observed in normal saliva from Johns Hopkins patients, nor in 16S rRNA NGS saliva samples from the Human Microbiome Project (HMP). Interestingly, both species were only observed in saliva from Human Papilloma Virus (HPV) positive and HPV negative oropharyngeal cancer patients. We confirmed the representation of both species in HMP data obtained from mid-vagina (n=128) and vaginal introitus (n=121) samples.

Resphera Insight also led to the discovery that Fusobacterium nucleatum, an oral cavity flora commensal bacterium linked to colon cancer, is enriched (600x higher) in saliva from a subset of HNSCC patients with advanced tumors stages.

Together, these high-resolution analyses on 583 samples suggest a possible role for bacterial species in the therapeutic outcome of HPV positive and HPV negative HNSCC patients.

Effect of masticatory stimulation on the quantity and quality of saliva and the salivary metabolomic profile

Background

This study characterized the changes in quality and quantity of saliva, and changes in the salivary metabolomic profile, to understand the effects of masticatory stimulation.

Methods

Stimulated and unstimulated saliva samples were collected from 55 subjects and salivary hydrophilic metabolites were comprehensively quantified using capillary electrophoresis-time-of-flight mass spectrometry.

Results

In total, 137 metabolites were identified and quantified. The concentrations of 44 metabolites in stimulated saliva were significantly higher than those in unstimulated saliva. Pathway analysis identified the upregulation of the urea cycle and synthesis and degradation pathways of glycine, serine, cysteine and threonine in stimulated saliva. A principal component analysis revealed that the effect of masticatory stimulation on salivary metabolomic profiles was less dependent on sample population sex, age, and smoking. The concentrations of only 1 metabolite in unstimulated saliva, and of 3 metabolites stimulated saliva, showed significant correlation with salivary secretion volume, indicating that the salivary metabolomic profile and salivary secretion volume were independent factors.

Conclusions

Masticatory stimulation affected not only salivary secretion volume, but also metabolite concentration patterns. A low correlation between the secretion volume and these patterns supports the conclusion that the salivary metabolomic profile may be a new indicator to characterize masticatory stimulation.

MicroRNA-143 suppresses oral squamous cell carcinoma cell growth, invasion and glucose metabolism through targeting hexokinase 2

miRNAs are non-coding RNAs that have functions to regulate gene expression and play essential roles in a variety of biological processes of cancers. In the present study, we report miR-143 acts as a tumor suppressor in human oral squamous cell carcinoma (OSCC). The expressions of miR-143 are down-regulated in both OSCC cell lines and patient samples compared with normal adjacent tissues. We found overexpression of miR-143 in oral cancer cell lines suppresses cell migration, cellular glucose metabolism and proliferation. Moreover, overexpression of miR-143 promoted apoptosis and significantly caused cell cycle arrest at G₁ stage. The colony formation of oral cancer cells was also suppressed by miR-143 We identified hexokinase 2 (HK2) as a direct target of miR-143 in oral cancer cells. Our data show that miR-143 complementary pairs to the 3'-UTR of HK2 in oral cancer cells, leading to the inhibition of glycolysis in vitro and in vivo Moreover, knockdown of HK2 by siRNA in oral cancer cells inhibited glucose metabolism, proliferation and migration. Recovery of glucose metabolism by overexpression of HK2 in miR-143 overexpressing cells restores the cell migration and proliferation, suggesting that the miR-143-mediated cancer suppression is through the direct inhibition of HK2. In summary, the present studies highlight miR-143 as a tumor suppressor in OSCC by the suppression of cell migration, glucose metabolism and proliferation through directly targeting HK2, rendering miR-143 a therapeutic strategy for the treatment of clinical OSCC patients.

Head and Neck Squamous Cell Carcinoma Metabolism Draws on Glutaminolysis, and Stemness Is Specifically Regulated by Glutaminolysis via Aldehyde Dehydrogenase

Cancer cells use alternate energetic pathways; however, cancer stem cell (CSC) metabolic energetic pathways are unknown. The purpose of this study was to define the metabolic characteristics of head and neck cancer at different points of its pathogenesis with a focus on its CSC compartment. UPLC-MS/MS-profiling and GC-MS-validation studies of human head and neck cancer tissue, saliva, and plasma were used in conjunction with in vitro and in vivo models to carry out this investigation. We identified metabolite biomarker panels that distinguish head and neck cancer from healthy controls, and confirmed involvement of glutamate and glutaminolysis. Glutaminase, which catalyzes glutamate formation from glutamine, and aldehyde dehydrogenase (ALDH), a stemness marker, were highly expressed in primary and metastatic head and neck cancer tissues, tumorspheres, and CSC versus controls. Exogenous glutamine induced stemness via glutaminase, whereas inhibiting glutaminase suppressed stemness in vitro and tumorigenesis in vivo. Head and neck CSC (CD44hi/ALDHhi) exhibited higher glutaminase, glutamate, and sphere levels than CD44lo/ALDHlo cells. Glutaminase drove transcriptional and translational ALDH expression, and glutamine directed even CD44lo/ALDHlo cells toward stemness. Glutaminolysis regulates tumorigenesis and CSC metabolism via ALDH. These findings indicate that glutamate is an important marker of cancer metabolism whose regulation via glutaminase works in concert with ALDH to mediate cancer stemness. Future analyses of glutaminolytic-ALDH driven mechanisms underlying tumorigenic transitions may help in the development of targeted therapies for head and neck cancer and its CSC compartment.