Saliva liquid biopsy: MMP2, MMP9, and TIMP2 as potential diagnostic biomarkers in oral squamous cell carcinoma. An observational case-control study.

Abstract

Oral squamous cell carcinoma (OSCC) is the most common malignant neoplasm in the oral cavity, characterized by high morbidity and mortality. Various proteins, including matrix metalloproteinases (MMPs), have been investigated as potential biomarkers for diagnosing and prognosing this disease.

Objective: To evaluate the utility of MMP-2, MMP-9, and the tissue inhibitor of metalloproteinase-2 (TIMP-2) as biomarkers in diagnosing and prognosing OSCC.

Methodology: This retrospective case-control study involved 60 cases and 30 controls from the University Hospital Fundación Santa Fe de Bogotá, part of the Colombian cohort of the InterChange/Headspace study. Saliva samples were collected using a 60-second mouth rinse with 10 mL of sterile saline solution, along with serum and oral tissue samples and clinical and sociodemographic data. MMP-9, MMP-2, and TIMP-2 concentrations in saliva were determined using ELISA, whereas tissue samples were analyzed by immunohistochemistry. MMP activity in saliva was quantified using a generic activity assay.

Results: Salivary MMP-9 and MMP-2 concentrations were significantly higher in cases than in controls, whereas no significant differences were observed for TIMP-2. ROC curve analysis showed excellent discriminatory capacity for salivary MMP-9 (AUC=0.946; sensitivity=0.817; specificity=0.867), good performance for MMP-2 (AUC=0.708; sensitivity=0.717; specificity=0.633), and lower discriminatory ability for TIMP-2 (AUC=0.630; sensitivity = 0.617; specificity=0.500). Elevated MMP-9 concentrations were observed in 33% of the serological samples. The immunohistochemistry of MMP-2, MMP-9, and TIMP-2 showed differences between cases and controls.

Conclusions: This study highlights salivary MMP-9 and MMP-2, together with MMP activity, as biomarkers of interest for OSCC that may contribute to the understanding of disease-related molecular changes detectable by liquid biopsy. While elevated salivary levels were observed in OSCC cases when compared to controls, these findings should be interpreted as exploratory. Elevated serological MMP-9 levels were observed in a small subset of cases. However, the limited sample size and the absence of a control group in this study preclude diagnostic interpretation. Larger, well-powered, and externally validated studies are required to determine the potential clinical utility of these biomarkers.