TERMINAL AMINE ISOTOPIC LABELING OF SUBSTRATES (TAILS) ANALYSIS REVEALS NOVEL POTENTIAL SUBSTRATES OF TUMOR SUPPRESSIVE MATRIX METALLOPROTEINASE-8 IN ORAL TONGUE CARCINOMA

Objectives Oral tongue squamous cell carcinoma (OTSCC)is an aggressive cancer with poor survival and increasing incidence. Matrix metalloproteinase-8 (MMP-8), unlike most MMPs, provides protective effects in various human cancers including OTSCC. Yet, the mechanism behind these effects remain unclear. Knowledge of the molecular basis of disease progression is crucial for developing novel treatments. Thus our study aimed to identify novel candidate substrates of MMP-8 to examine the mechanisms behind its tumor-suppressive actions in OTSCC. Findings We have previously generated stably MMP-8 overexpressing oral squamous cell carcinoma cell line (HSC-3 MMP-8+ cells) and showed that overexpression of MMP-8 significantly decreased the cell migration and invasion. However, the molecular mechanisms hampering the motility of these cells remained unrevealed. The current study aimed to unravel these mechanisms by subjecting the secretomes of MMP-8+ and control HSC-3 cells to Terminal Amine Isotopic Labeling of Substrates (TAILS) analysis to find novel candidate substrates for MMP-8. The analysis revealed cleaved proteins, including dysadherin, 60S ribosomal protein L13, kallikrein-5, lipolysis-stimulated lipoprotein receptor, matrix-remodeling-associated protein 7, POTE ankyrin domain family member E, stathmin 1 and tubulin alpha-1C chain, which were enriched in MMP-8+ secretomes. Dysadherin is known to promote metastasis of various cancers and decrease cell adhesion. MMP-8+ cells showed decreased levels of dysadherin, suggesting a cleavage by MMP-8 from the cell membrane. Moreover, the adhesion of MMP-8+ cells was enhanced which might affect the migration. Conclusions Several novel candidate substrates of MMP-8 were revealed by TAILS analysis. The potential substrates, including dysadherin, may play crucial role in the changed behavior of MMP-8+ cells and needs to be further explored for their potential role in OTSCC. The cleavage of tumor-promoting dysadherin from the cell membrane might be one of the mechanisms by which MMP-8 increases tumor cell adhesion and thereby suppresses migration.