Oral Health May Affect the Performance of mRNA-Based Saliva Biomarkers for Oral Squamous Cell Cancer

Salivary Biomarkers for Oral Cancer Detection: An Exploratory Systematic Review

Different efforts have been made to find better and less invasive methods for the diagnosis and prediction of oral cancer, such as the study of saliva as a source of biomarkers. The aim of this study was to perform a scoping review about salivary molecules that have been assessed as possible biomarkers for the diagnosis of oral squamous cell carcinoma (OSCC). A search was conducted using EBSCO, PubMed (MEDLINE), Scopus, and Web of Science. The research question was as follows: which molecules present in saliva have utility to be used as biomarkers for the early detection of oral cancer? Sixty-two studies were included. Over 100 molecules were assessed. Most of the markers were oriented towards the early diagnosis of OSCC and were classified based on their ability for detecting OSCC and oral potentially malignant disorders (OPMDs), OSCC outcome prediction, and the prediction of the malignant transformation of OPMDs. TNF-α, IL-1β, IL-6 IL-8, LDH, and MMP-9 were the most studied, with almost all studies reporting high sensitivity and specificity values. TNF-α, IL-1β, IL-6 IL-8, LDH, and MMP-9 are the most promising salivary biomarkers. However, more studies with larger cohorts are needed before translating the use of these biomarkers to clinical settings.

Promising applications of human-derived saliva biomarker testing in clinical diagnostics

Saliva testing is a vital method for clinical applications, for its noninvasive features, richness in substances, and the huge amount. Due to its direct anatomical connection with oral, digestive, and endocrine systems, clinical usage of saliva testing for these diseases is promising. Furthermore, for other diseases that seeming to have no correlations with saliva, such as neurodegenerative diseases and psychological diseases, researchers also reckon saliva informative. Tremendous papers are being produced in this field. Updated summaries of recent literature give newcomers a shortcut to have a grasp of this topic. Here, we focused on recent research about saliva biomarkers that are derived from humans, not from other organisms. The review mostly addresses the proceedings from 2016 to 2022, to shed light on the promising usage of saliva testing in clinical diagnostics. We recap the recent advances following the category of different types of biomarkers, such as intracellular DNA, RNA, proteins and intercellular exosomes, cell-free DNA, to give a comprehensive impression of saliva biomarker testing.

Saliva diagnostics: emerging techniques and biomarkers for salivaomics in cancer detection

INTRODUCTION

The pursuit of easy-to-use, non-invasive and inexpensive diagnostics is an urgent task for clinicians and scientists. Saliva is an important component of body fluid with regular changes of contents under various pathophysiological conditions, and the biomarkers identified from saliva shows high application potentials and values in disease diagnostics. This review introduces the latest developments in saliva research, with an emphasis on the detection and application of salivary biomarkers in cancer detection.

AREAS COVERED

Detection of disease-specific biomarkers in saliva samples by existing salivaomic methods can be used to diagnose various human pathological conditions and was introduced in details. This review also covers the saliva collection methods, the analytical techniques as well as the corresponding commercial products, with an aim to describe an holistic process for saliva-based diagnostics.

EXPERT OPINION

Saliva, as a non-invasive and collectable body fluid, can reflect the pathophysiological changes of the human body to a certain extent. Identification of reliable saliva biomarkers can provide a convenient way for cancer detection in clinical applications.

Advances in the Diagnosis, Monitoring, and Progression of Oral Cancer through Saliva: An Update

The early detection of cancer, and in particular oral cancer, has been a priority objective of study in recent years. Saliva has been proposed as an easy-to-obtain means of providing the necessary information to diagnose malignant lesions in the oral cavity, since it can be obtained very easily and completely noninvasively. There are a number of molecules, known as biomarkers, which may be involved in the malignant transformation of oral lesions, and which have different natures. The involvement of proteins (“proteomics”), metabolites (“metabolomics”), and even certain genes in the structural changes of altered tissue has been investigated in order to establish validated parameters for the early diagnosis of oral cancer. In addition, the development of new analytical assay methods that can reduce costs and obtain better results in terms of sensitivity and specificity has been a key point in recent research in this field. Even though there are numerous biomarkers with results showing high sensitivity and specificity, there is still a need for more studies, with a larger sample and with analytical methods that can constitute a real advance in time and cost. Although salivary biomarkers are a promising new diagnostic tool for oral cancer, for the moment they do not replace biopsy as the “gold standard”.

Selection and optimization of reference genes for RT-qPCR normalization: A case study in Solanum lycopersicum exposed to UV-B

Quantitative RT- PCR is one of the most common methods to study gene expression in response to stress. Therefore, it is crucial to have suitable reference genes (RGs) for result normalization. Although several reports describe UV-B-modulated gene expression in Solanum lycopersicum, there are no suitable RGs identified until now. The aim of this work was to evaluate the suitability of seven traditional genes: actin (ACT), tubulin (TUB), ubiquitin (UBI), glyceraldehyde- 3 phosphate dehydrogenase (GAPDH), elongation factor 1α (EF1α), phosphatase 2A catalytic subunit (PP2A) and GAGA binding transcriptional activator (GAGA); and two non-traditional genes: thioredoxin h1 (TRX h1) and UV-B RESISTANCE LOCUS 8 (UVR8), as candidate RGs for their potential use as reliable internal controls in leaves, stems and roots of tomato seedlings exposed to acute and chronic UV-B. The stability of these genes expression was evaluated using five statistical algorithms: geNorm, NormFinder, BestKeeper, Delta Ct and ANOVA. Considering the comprehensive stability ranking, we recommend ACT+TUB as the best pair of RGs for leaves, PP2A+GAPDH+TRX h1 for stems and TUB+UVR8 for roots. The reliability of the selected RGs for each tissue was verified amplifying tomato chalcone synthase 1 (CHS1) and cyclobutane pyrimidine dimer (CPD) photolyase (PHR1-LIKE). Under UV-B treatment, CHS1 was upregulated in leaves, stems and roots whereas PHR1-LIKE was only upregulated in leaves and stems. This interpretation differs when the most and least stable RGs are chosen. This is the first report regarding suitable RGs selection for accurate normalization of gene expression in tomato seedlings exposed to UV-B irradiation.

Efficacy of hypermethylated DNA biomarkers in saliva and oral swabs for oral cancer diagnosis: Systematic review and meta-analysis

OBJECTIVES

This study aims to determine the diagnostic test accuracy (DTA) of hypermethylated DNA biomarkers in saliva and oral swabs for oral squamous cell carcinoma (OSCC) detection from the prevalidation studies available.

MATERIALS AND METHODS

Electronic database searching of PubMed, EMBASE, Cochrane Library, Scopus, Web of Science, and LILACS was conducted to identify relevant articles that were published between January 1, 2000, and August 1, 2020.

RESULTS

Meta-analysis was conducted based on 11 of 20 studies selected for review. Included studies had high bias concerns on the QUADAS-2 study assessment tool. We found that salivary and oral swab hypermethylation markers had better specificity than sensitivity for oral cancer detection. Summary sensitivity and specificity (95% CI) of hypermethylation panels were 86.2% (60-96.2) and 90.6% (85.9-93.9) while for individual markers, summary sensitivity and specificity (95% CI) were 70% (56.9-80.5) and 91.9% (80.3-96.9), respectively. Respective positive and negative likelihood ratios for combined markers were 9.2 (5.89-14.36) and 0.15 (0.05-0.5), and 8.61 (3.39-21.87) and 0.33 (0.22-0.49) for single-application biomarkers.

CONCLUSION

DNA hypermethylation biomarkers especially in combination have acceptable DTA that warrants further optimization with rigorous biomarker evaluation methods for conclusive determination of their efficacy.

Deep dive on the proteome of salivary extracellular vesicles: comparison between ultracentrifugation and polymer-based precipitation isolation

Salivary extracellular vesicles (EVs), as novel functional carriers and potential biomarkers, are usually obtained by ultracentrifugation (UC) and polyethylene glycol (PEG)-based precipitation methods. However, salivary EVs obtained by these two methods have not been systematically compared. Here, we perform an in-depth analysis on EVs isolated by these two methods using proteomics. Both methods obtain EVs ranging from 40 to 210 nm, with the PEG method resulting in a wider size distribution. PEG-separated products were irregularly shaped and aggregated, while UC-separated ones were monodispersed and teacup-shaped. Additionally, the expression of EV-specific markers was higher in UC-separated EVs. Using tandem mass spectrometry proteomics, we identified and quantified 1217 kinds of saliva exosomal proteins and 361 kinds of differential proteins, showing that UC can isolate more EV-related proteins. These results offer some guidance for EV separating and provide potential direction for the use of EVs in non-invasive diagnosis.

Optimized liquid-based cytology for the cellular and molecular analysis of oral keratinocytes: A promising diagnostic tool

BACKGROUND

Liquid-based cytology (LBC) has improved exfoliative cytology by facilitating the extraction of more precise information from epithelial cells. The aim of this study was to optimize a protocol using a conventional cytobrush to perform LBC, obtaining oral keratinocytes for their further cellular and molecular analysis.

METHODS

LBC was performed in 30 healthy donors from buccal mucosa. We evaluated the use of diethyl pyrocarbonate (DEPC)-treated Dulbecco's Modified Eagle Medium (DMEM) medium right after the collection of the cells. Cell morphology and viability were determined by Orcein staining and flow cytometry, respectively. RNA was extracted by the trizol method, and evaluated with spectrometry and electrophoresis. Finally, RNA was copied into cDNA and GAPDH and TLR2 genes were amplified by reverse transcription polymerase chain reaction (RT-PCR) and quantitative reverse transcription polymerase chain reaction (RT-qPCR) using specific primers.

RESULTS

Only DEPC-treated DMEM preserved the viability of intact intraepithelial keratinocytes. RNA quantity and quality improves in samples treated with DEPC. RNA integrity is comparable with a cell line control. GAPDH gene was successfully amplified by RT-PCR and RT-qPCR.

CONCLUSIONS

Therefore, LBC performed under these conditions becomes a reproducible technique for the retrieval of intraepithelial oral keratinocytes with good cell viability for cytomorphometric analysis, and extraction of good RNA quality suitable for molecular analyses such as PCR. We propose this LBC protocol as a complementary method to the cellular and molecular study of oral mucosa pathologies; however, it requires further study.

Potential Salivary mRNA Biomarkers for Early Detection of Oral Cancer

We evaluated potential biomarkers in human whole saliva for the early diagnosis of oral squamous cell carcinoma (OSCC). We selected 30 candidate genes with relevance to cancer from recent reports in PubMed. Saliva samples were obtained from 34 non-tumor control and 33 OSCC patients. Real-time PCR was performed, and mRNA levels were compared. Normalized mRNA levels of six genes (NGFI-A binding protein 2 (NAB2), cytochrome P450, family 27, subfamily A, polypeptide 1 (CYP27A1), nuclear pore complex interacting protein family, member B4 (NPIPB4), monoamine oxidase B (MAOB), sialic acid acetyltransferase (SIAE), and collagen, type III, alpha 1 (COL3A1)) were significantly lower in saliva of OSCC patients. Receiver operating characteristics (ROC) analysis was used to individually evaluate the predictive power of the potential biomarkers for OSCC diagnosis. The area under the curve (AUC) values were evaluated for the OSCC vs. non-tumor groups via univariate ROC analyses, as well as multivariate ROC analyses of combinations of multiple potential biomarkers. The combination of CYP27A1 + SIAE showed a favorable AUC value of 0.84. When we divided saliva samples into two groups according to age using a 60-year cut-off, with OSCC patients and controls evaluated together, the AUC of MAOB-NAB2 was more predictive of OSCC in the under-60 group (AUC, 0.91; sensitivity, 0.92; and specificity, 0.86) than any other gene combination. These results are expected to aid the early diagnosis of OSCC, especially in patients under 60 years of age. While more studies with larger numbers of patients are necessary, our result suggest that salivary mRNA would be a potent biomarker for early OSCC diagnosis.

Integrin α5/ITGA5 Promotes The Proliferation, Migration, Invasion And Progression Of Oral Squamous Carcinoma By Epithelial-Mesenchymal Transition

Background

Integrin signalling is involved in cell migration, invasion, proliferation and motility. Integrin α5/ITGA5 is a subunit of Integrin and contributes to the activation of Integrin signalling. The potential role of Integrin α5/ITGA5 in oral squamous cancer remains unknown. The aim of this study was to uncover the effect and mechanism of Integrin α5/ITGA5 in the progression of oral squamous carcinoma.

Method

TCGA database scanning, qRT-PCR, immunohistochemistry and Western blotting assays were used to detect the expression of Integrin α5/ITGA5 in tissues and cell lines. We established stable Integrin α5/ITGA5 overexpressing and Integrin α5/ITGA5 knockdown cell lines. We investigated the biological function and the underlying mechanism of Integrin α5/ITGA5 through a series of experiments.

Results

Integrin α5/ITGA5 was upregulated in cancer tissue, and its levels negatively correlated with the overall survival (OS) of patients. Integrin α5/ITGA5 promoted proliferation, migration and invasion in an oral squamous carcinoma cell line by EMT (epithelial-mesenchymal transition).

Conclusion

Integrin α5/ITGA5 promotes the proliferation, migration and invasion of oral squamous carcinoma.

Salivary IL-6 mRNA is a Robust Biomarker in Oral Squamous Cell Carcinoma

Salivary IL-6 mRNA was previously identified as a promising biomarker of oral squamous cell carcinoma (OSCC). We performed a multi-center investigation covering all geographic areas of Hungary. Saliva from 95 patients with OSCC and 80 controls, all Caucasian, were collected together with demographic and clinicopathological data. Salivary IL-6 mRNA was quantified by real-time quantitative PCR. Salivary IL-6 protein concentration was measured by enzyme-linked immune-sorbent assay. IL-6 protein expression in tumor samples was investigated by immunohistochemistry. Normalized salivary IL-6 mRNA expression values were significantly higher (p < 0.001) in patients with OSCC (mean ± SE: 3.301 ± 0.885) vs. controls (mean ± SE: 0.037 ± 0.012). Differences remained significant regardless of tumor stage and grade. AUC of the ROC curve was 0.9379 (p < 0.001; 95% confidence interval: 0.8973–0.9795; sensitivity: 0.945; specificity: 0.819). Salivary IL-6 protein levels were significantly higher (p < 0.001) in patients (mean ± SE: 70.98 ± 14.06 pg/mL), than in controls (mean ± SE: 12.45 ± 3.29). Specificity and sensitivity of IL-6 protein were less favorable than that of IL-6 mRNA. Salivary IL-6 mRNA expression was significantly associated with age and dental status. IL-6 manifestation was detected in tumor cells and tumor-infiltrating leukocytes, suggesting the presence of a paracrine loop of stimulation. Salivary IL-6 mRNA is one of the best performing and clinically relevant biomarkers of OSCC.

Clinical validity of saliva and novel technology for cancer detection

Cancer, a local disease at an early stage, systemically evolves as it progresses by triggering alterations in surrounding microenvironment, disturbing immune surveillance and further disseminating its molecular contents into circulation. This pathogenic characteristic of cancer makes the use of biofluids such as blood/serum/plasma, urine, tear and cerebrospinal fluids credible surrogates harboring tumor tissue-derived molecular alterations for the detection of cancer. Most importantly, a number of recent reports have credentialed the clinical validity of saliva for the detection of systemic diseases including cancers. In this review, we discussed the validity of saliva as credible biofluid and clinical sample type for the detection of cancers. We have presented the molecular constituents of saliva that could mirror the systemic status of our body and recent findings of salivaomics associated with cancers. Recently, liquid biopsy to detect cancer-derived circulating tumor DNA has emerged as a credible cancer-detection tool with potential benefits in screening, diagnosis and also risk management of cancers. We have further presented the clinical validity of saliva for liquid biopsy of cancers and a new technology platform based on electrochemical detection of cancer-derived ctDNA in saliva with superior sensitivity and point-of-care potential. The clinical utilities of saliva for the detection of cancers have been evidenced, but biological underpinning on the existence of molecular signatures of cancer-origin in saliva, such as via exosomal distribution, should be addressed in detail.