ASSESSMENT OF P53 AND KI-67 EXPRESSION IN SNUFF-INDUCED LESIONS

An immunohistochemical study of snuff-induced lesions with a monoclona l antibody (DO-7) specific to p53 mutant and wildtype antioncogene pro duct demonstrated nuclear overexpression of the mutant protein in 45.9 nuclear profiles/mm(2) epithelium (SEM 10.8; n=15) compared with only 0.18 positively stained nuclear profiles/mm(2) in the control group ( SEM 0.18; n=4). Furthermore, the biopsy material was also stained with the antibody Ki-67, which has been shown to be excellent for the esti mation of the growth fraction in both normal and malignant human tissu es. Ki-67 stained positive in 566.1 nuclear profiles/mm(2) epithelium (SEM 85.0; n=15) in the snuffgroup compared with 20.2 nuclear profiles /mm(2) (SEM 4.9; n=4) in the control group. To the best of our knowled ge, this is the first study showing overexpression of p53 protein and Ki-67 in snuff-induced lesions. The results may indicate that the p53 gene is involved in the initial events leading to subsequent malignant transformation of oral mucosa exposed to snuff. Furthermore, mutation s of the p53 gene have been associated with increased cellular prolife ration with greater risk of perpetuation of mutations and malignant tr ansformation.