Ubiquitin and malignant transformation of oral mucosa.

BACKGROUND: Ubiquitinylation is a cyclical process operating in all cells to target specific proteins (eg, p53) for degradation. Abnormal accumulations of ubiquitinylated proteins have been identified in colorectal carcinoma. This study investigated abnormal ubiquitinylated proteins and changes in ubiquitinylation patterns associated with malignant transformation of oral tissue. METHODS: Twenty-three fresh specimens of normal, premalignant, oral squamous cell carcinoma (SCC), and its adjacent normal mucosa were collected for immunohistochemistry with anti-ubiquitin and anti-UbcH7 (a human ubiquitin-conjugating enzyme) antibodies using light and electron microscopy and protein analysis by Western blot. RESULTS: Ubiquitin and UbcH7 were observed in both nucleus and cytoplasm of normal, "premalignant" and malignant tissues of oral mucosa using immunoelectron microscopy. However there was no change in their distribution pattern. CONCLUSIONS: The lack of demonstrable difference in distribution pattern of ubiquitin enzymes indicates that at present, ubiquitin cannot be used as a diagnostic marker for malignant transformation of oral SCC.