Diagnostic Potential of Salivary Interleukin-8 mRNA and Protein in Oral Squamous Cell Carcinoma and Oral Potentially Malignant Disorders: Insights From South India

Background Oral squamous cell carcinoma (OSCC) is a common type of head and neck cancer, which is often preceded by oral potentially malignant disorders (OPMDs). Though comprehensive examination forms the backbone of oral cancer screening, the combination of salivary proteomic and transcriptomic markers may identify molecular markers specific to OSCC and assess their ability to predict malignant transformation in OPMD. Hence, this study aimed to determine the diagnostic utility of salivary interleukin-8 (IL-8) mRNA and protein in the differential diagnosis of OSCC, OPMD, and healthy controls. Methodology Unstimulated whole saliva was collected from 90 subjects, 30 in each group (i.e., OSCC, OPMD, and controls). This comparative cross-sectional, multicenter study was conducted after obtaining institutional ethical clearance. The supernatant was treated with RNase inhibitor and separated into the following two fractions: one for RNA extraction and the other for enzyme-linked immunosorbent assay (ELISA). The results were statistically analyzed using SPSS version 21 software (IBM Corp., Armonk, NY, USA), and p-values <0.05 were considered statistically significant. Results Salivary IL-8 showed statistically significant differences when all three groups were compared at the protein (p < 0.001) and transcriptomic (p = 0.001) levels. Salivary IL-8 protein showed the best discriminatory ability in distinguishing OSCC from controls, with the highest area under the curve (AUC) of 0.915. It yielded a sensitivity of 80% and a specificity of 76% at a cutoff value of 239.55 pg/mL (p < 0.001) with strong predictive power. Conclusions Salivary IL-8 protein showed strong discriminatory ability in the present study compared to salivary mRNA in distinguishing OSCC from controls, with the highest AUC of 0.915. The sensitivity and specificity, as well as the predictive value of polymerase chain reaction measurements of salivary IL-8 mRNA, were not as strong as the sensitivity and specificity for salivary IL-8 protein using ELISA. Alterations in OSCC-associated IL-8 expression levels, both at the protein and mRNA levels, could aid in early oral cancer detection during population mass screening to enable identification of high-risk groups with strong discriminatory ability.