Saliva is a complex fluid composed of wide range of organic and inorganic components. The source of information is largely derived from the variety of DNA’s, RNA’s and proteins present in the saliva. The assessment of salivary biomarkers is a recent development with increased interest in its use as a diagnostic and prognostic tool. The easy and non-invasive method of collection, the proximity of saliva to various oral lesions along with the availability of the newer technologies, has enabled the identification of biomarkers present in small quantities thus signifying the use of saliva as an important assessment media. Salivary diagnostics are being extensively reviewed to identify potential biomarkers using genomics, proteomics, transcriptomics and metabolomics. Ever since its discovery, metabolomics has been widely applied to various clinical conditions for identifying biomarkers. Metabolomic investigations can generate quantitative data for metabolites which helps in elucidating the metabolic dynamics related to disease states and drug exposure. Oral cancer is a significant disease affecting humans and the most common form is the oral squamous cell carcinoma (OSCC) which accounts for over 90% of the reported malignancies of the oral cavity. In general, OSCC can arise de novo or from pre-existing oral lesions collectively referred to as oral potentially malignant disorders such as leukoplakia. Some of the salivary metabolites which could serve as tumor biomarkers include 1-methylhistidine, inositol 1,3,4- triphosphate, d-glycerate-2-phosphate, 4-nitoquinolone-1-oxide, 2-oxoarginine, norcocaine nitroxide, sphinganine-1-phosphate, pseudouridine, L-homocysteic acid, ubiquinone, neuraminic acid and estradiol valerate. In addition, literature review suggests the utility of microRNA, genetic and epigenetic alterations as salivary specific tumor biomarkers. This presentation provides an overview of the clinical applicability of saliva -based biomarkers in oral cancer along with the discussion of research finding determining the clinical utility of salivary metabolites in oral leukoplakia and oral squamous cell carcinoma.
Keywords: Salivary diagnostics; Oral cancer; oral pre-cancer; metabolomics