OBJECTIVETo study the expression and significance of p65 which is an important subtype of nuclear transcription factor kappaB (NF-kappaB) and its inhibitory protein IkappaBalpha in malignant transformation of hamster buccal mucosa.

METHODSThe animal model of malignant transformation in hamster buccal mucosa induced by DMBA (0.5%) was established. Twelve paired specimens including normal buccal mucosa, epithelial hyperplasia, epithelial dysplasia and squamous cell carcinoma (SCC) were subjected to Western blot for the analysis of p65. The expression of IkappaBalpha was observed in 22 normal buccal epithelia, 20 hyperplasia epithelia, 35 dysplasia epithelia and 23 SCC by immunohistochemical evaluation.

RESULTSIn normal buccal epithelia and hyperplasia epithelia, the expression of p65 was not obvious, and there was no significant difference between them (P > 0.05). The expression of IkappaBalpha existed at large, but mostly localizing in cell cytoplasmic staining in the basal cell layer and bottom of spinocelluar layer. With the occurrence of epithelia dysplasia, the expression of p65 gradually increased, comparing with normal buccal epithelia and hyperplasia epithelia (P < 0.01). But the positive intensity of IkappaBalpha was dramatically decreased (P < 0.05). In SCC, p65 expressed at a higher level comparing with normal buccal mucosa and dysplasia (P < 0.01), while the staining of IkappaBalpha was feedbackly higher comparing with dysplasia (P < 0.01) and even with normal buccal mucosa (P < 0.01).

CONCLUSIONNF-kappaB p65 is strongly activated in malignant transformation of hamster buccal mucosa. The abnormal expression of p65 and IkappaBalpha, especially the ascending expression of p65 as well as the descending expression of IkappaBalpha in dysplasia may be an early event during oral carcinogenesis, and can be used as biomarkers for supervising oral malignancy.