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The low 5-year survival rate for Oral Squamous Cell Carcinoma (OSCC) is largely attributed to the limitations of current invasive diagnostic procedures and diagnosis at a late stage. Biomarkers from saliva and exfoliated oral cells could be used to diagnose oral cancer as the malignancy begins in the epithelium and would be particularly useful for screening patients in high-risk categories like tobacco users. However, single biomarker use can be deceptive. This study investigates the candidature of onco-miRNAs (miR-21-5p, miR-31-5p, and miR-155-5p) and tumor suppressor miRNAs (miR-125-3p and miR-133a), along with their targets p53 and EGFR, in oral exfoliated cells, as noninvasive biomarkers for timely detection of oral cancer in high-risk tobacco users.

We analyzed salivary miRNAs and mRNAs in 40 individuals comprising oral cancer patients, tobacco consumers, and healthy controls using quantitative real-time PCR (qRT-PCR). This study focused on selected oncogenic and tumor-suppressor miRNAs. The miRNA target mRNAs, p53 and EGFR, were analyzed by qRT-PCR and immunocytochemistry. Diagnostic potential was assessed using receiver operating characteristic (ROC) curve analysis.

The relative gene expression levels of all studied miRNAs and their target mRNA were found deregulated among the study participants. miR-31-5p increased 23-fold in tobacco consumers (p = 0.002) and 38-fold in oral cancer patients (p = 0.002). EGFR expressions increased 12-fold in tobacco consumers (p = 0.001) and 20-fold in oral cancer patients (p = 0.0003).

The results of this pilot study suggest that combined salivary miR-31-5p and oral exfoliated-cell EGFR expression is a candidate biomarker panel for noninvasive screening in high-risk tobacco users. Given the small, single-cohort design, these preliminary, hypothesis-generating findings require validation in larger, independent cohorts before clinical application.