Evaluation of salivary and serum exosomal mRNAs as biomarkers for the diagnosis and prognosis of oral squamous cell carcinoma

Minimally-invasive or non-invasive biomarkers from serum and saliva hold significant promise for real-time monitoring of oral squamous cell carcinoma (OSCC). However, the diagnostic potential of exosomes, which carry heterogeneous tumor-derived functional cargo remains largely underexplored. This study aimed to evaluate the diagnostic and prognostic utility of exosomal mRNAs derived from saliva and serum samples of OSCC patients. Exosomes were isolated from paired serum and saliva samples of 40 OSCC patients and 40 healthy controls using commercial kits. Characterization was performed using NTA, TEM, zeta potential, protein/lipid quantification, and western blotting. Expression of nine mRNA markers including cytokines (IL1, IL6, IL8, TNF-α), proliferation markers (OAZ1, SAT, S100P), and metastasis-related molecules (MMP9, Chemerin) was analyzed by qRT-PCR. Diagnostic accuracy was evaluated using ROC curve analysis, and correlations with tumor grade and lymph node metastasis were systematically investigated. Results demonstrated that salivary exosomal MMP9, TNF-α, and OAZ1 exhibited markedly higher diagnostic sensitivity and specificity compared to the top-performing serum exosomal derived markers (MMP9, IL1, and OAZ1). Notably, a two-gene salivary mRNA panel combining TNF-α and OAZ1 demonstrated strong discriminatory power (AUC: 0.89, sensitivity: 80%, specificity: 90%; Youden Index: 0.70). Additionally, salivary exosomal MMP9, IL8, S100P, SAT, and OAZ1 significantly differentiated between grade I and grade III OSCC. Moreover, IL6 expression positively correlated with lymph node metastasis. In contrast, serum exosomal markers lacked clear discriminatory potential. Therefore, salivary exosomal panel of TNF-α and OAZ1 represent promising non-invasive biomarkers for OSCC diagnosis, while MMP9 and IL6 is informative for tumor grading.