Identification of a Novel Salivary Four-miRNA Signature for Non-Invasive Diagnosis of Oral Squamous Cell Carcinoma

Oral squamous cell carcinoma (OSCC) is the most common type of oral cancer, often diagnosed at advanced stages due to the lack of early symptoms and limitations of current invasive diagnostic methods. Salivary microRNAs (miRNAs) have emerged as promising non-invasive biomarkers for early detection. This study evaluated the diagnostic potential of ten miRNAs, selected from literature, in saliva samples from 30 OSCC patients and 30 healthy controls. The workflow included RNA extraction, reverse transcription, qRT-PCR amplification, and data normalization using the mean expression of the two most stable miRNAs identified across and within groups. Five miRNAs showed significant differential expression: miR-21 and miR-424 were upregulated, while miR-31, miR-146a, and let-7a were downregulated in OSCC patients. Receiver operating characteristic (ROC) curve analysis indicated moderate individual diagnostic power (AUC 0.658–0.720). A multivariate logistic regression combining miR-21, miR-31, miR-146a, and miR-424 yielded an AUC of 0.959, 96.7% specificity, and 86.7% sensitivity. Although limited by sample size, this study provides the first step for larger validation studies aimed at confirming the diagnostic utility of our salivary four-miRNA signature as a cost-effective and minimally invasive diagnostic tool for OSCC.