Proteomic profiling of differential display analysis for human oral squamous cell carcinoma: 14-3-3 σ Protein is upregulated in human oral squamous cell carcinoma and dependent on the differentiation level

Oral squamous cell carcinoma (OSCC) has an absolute majority of all oral cancer. We used proteomic technology to analyze the protein expression profile in OSCC tissues and accompanying surrounding normal tissues in four oral locations (buccal mucosa, gingival mucosa, oral floor, and tongue). Ten protein spots were overexpressed more strongly in cancer tissues than normal ones, and were identified as proliferating cell nuclear antigen, 14-3-3 ε, 14-3-3 σ, proteasome subunit α type 5, translationally controlled tumor protein, eukaryotic translation initiation factor 3 subunit, macrophage capping protein, and mitochondrial isocitrate dehydrogenase subunit α. Macrophage capping protein and mitochondrial isocitrate dehydrogenase subunit α had two spots. Especially, we focused on 14-3-3 σ protein, one of the eight identified proteins, and assessed its expression level in four oral locations of OSCC by using differential display methods. The expression level of 14-3-3 σ protein was upregulated in four locations of oral cavity. Eight proteins which we identified in this study may play an important role in OSCC carcinogenesis and progression and could be used as diagnostic biomarkers of OSCC.