S100A8 as potential salivary biomarker of oral squamous cell carcinoma using nanoLC-MS/MS

Background: Oral squamous cell carcinoma (OSCC) shows low 5-year survival; early treatment greatly reduces mortality and morbidity. Saliva is a non-invasive sample, with good potential to discover biomarkers for early detection. Methods: NanoLC-MS/MS served to analyze saliva proteome from control subjects (n. = 35) and OSCC patients T1 (n. = 29), T2 (n. = 36), T3 (n. = 14) and T4 (n. = 21) stages. Identified biomarkers were verified by Western blot and ELISA assays. Results: NanoLC-MS/MS analysis of salivary proteins between 10 and 15. kDa identified S100A8, hemoglobin delta and gamma-G globin in T3 and T4 stage OSCC as well as S100A7 in T1 and T2 stage OSCC. Western blot and ELISA indicated positive correlation between salivary S100A8 increment and tumor size stage. High level of S100A8 appeared in 3.4, 13.9, 92.9, and 100% of saliva OSCC patients with T1, T2, T3, and T4 stages, respectively. Significant increase of salivary S100A7 was observed in 20.7% and 11.1% of those with T1 and T2, respectively. AUROC curve indicated high sensitivity, specificity and accuracy of S100A8-based ELISA as a detector. Conclusions: NanoLC-MS/MS, Western blot and ELISA manifested salivary S100A8 as a specific and sensitive marker for detection of OSCC patients. Salivary S100A8 protein could be applicable in developing OSCC diagnostics.