Identification of TPD54 as a candidate marker of oral epithelial carcinogenesis

The purpose of this study was to identify a novel marker of oral carcinogenesis in order to make the early diagnosis of malignant potential of oral lesion. In this study, we analyzed using tissue proteomics that relies on a functional relationship between laser microdissection (LMD) and nano-flow liquid chromatography and mass spectrometry and protein identification by tandem mass spectrometry (LC/MS/MS). A microdissected formalin-fixed paraffin-embedded tissue block of a single case of oral squamous cell carcinoma (OSCC) in the lower gingiva was analyzed by LC/MS/MS resulting in more than 400 unique protein identifications. In comparison with each protein profiling list from normal epithelium, dysplastic epithelium and OSCC, a new candidate marker of oral carcinogenesis, tumor protein D54 (TPD54), was identified. We performed real-time PCR, the Western blotting and immunohistochemical analysis for validation about TPD54 in various tissues including normal epithelium, hyperplastic, dysplastic epithelium and OSCC. As the result of real-time PCR analysis, the level of TPD54 expression in cancerous region was statistically higher than that in normal epithelia. In the Western blotting analysis, expression of TPD54 was high in OSCC cell, but was little seen in keratinocyte and fibroblast cells. And in the immunohistochemical analysis, the ratio of TPD54 expression increased according to the degree of carcinogenesis in epithelial lesions. From these results, we concluded that TPD54 was a candidate marker of oral epithelial carcinogenesis.