Human Salivary microRNA as Biomarkers in Oral Potentially Malignant Disorder-A Narrative Review

Oral potentially malignant disorders (OPMDs) denote mucosal disorders of oral cavity with higher possibility for malignant transformation. The relatively stable salivary single stranded non-coding RNAs (microRNA) can be utilized as biomarker in different malignancies for diagnosing and management purposes. This paper aims to assess the clinical application of salivary miRNAs in OPMD patients from the available literature for early discovery of oral cancer. A systematic electronic search was made and 13 articles were collected and included to fulfill the study objective. Evidence from numerous reports suggested that majority of the salivary miRNAs have significantly overexpressed in different OPMD patients. These include miR21,miR31,miRNA-184,miR-30e-3p, let-7a-5p,miR-335-5P,miR-144,miR25-3p,miR19a-3p,miR-25-3p,miR19a-3p,miR-660-5p,miR-140-5p,miR590-5p,miR-9. The downregulated markers are miR-27a/b,microRNA 320a,miR 200a,miRNA-145,miR-10b-5p,miR-99a-5p,miR-99b-5p,miR145-5p,miR-100-5p,miR-125b-5p,miR-181b,miR-181c, miR-331-3p, miR15a-5p, miR-708, miR-150-5p. Among the above mentioned markers, the miR-31,miR-21,miR-184,miR-27b have shown promising clinical utilization in OPMDs since the AUC results suggested acceptable to excellent discrimination between OPMDs from other study groups. Besides, the miR-31and miR-21 is frequently studied among others. Micro RNAs have distinctive expression patterns in OPMDs and furnish them a specific tool in diagnostic/prognostic applications in these patients. In addition, the miRNAs could also be used as therapeutic tool for specific gene target thereby improved management of OPMD patients is possible.