Differential expression of p53, p63 and p73 proteins in human buccal squamous-cell carcinomas

Abnormalities in the p53 gene are regarded as the most consistent of the genetic abnormalities in oral squamous-cell carcinoma. Two new members of the p53 gene family, p73 and p63, have recently been identified, with the three sharing considerable sequence homology at the acidic N-terminal transactivation, central DNA-binding and C-terminal oligomerization domains, indicating possible functional and biological interactions. The differential expression of p73, p63 and p53 genes in human oral squamous-cell carcinoma does not yet appear to be completely understood, however. In this study, therefore, immunohistochemical analysis of protein expression was performed for 40 samples of well-differentiated human buccal squamous-cell carcinomas, with 10 specimens of normal buccal mucosa employed as controls. Differential expressions of p63, p73 and p53 proteins in the carcinoma samples were: p63+/p73+/p53 + (n = 28; 70%); p63+/p73+/p53- (n = 4; 10%); p63+/p73-/p53- (n = 8; 20%), respectively; and p63+/p73+/p53- for normal mucosa (n = 10; 100%). A significant correlation between p53, p63 and p73 immunoexpression was demonstrated for the buccal squamous-cell carcinoma samples (P < 0.0001; Fisher's exact test). Significance was not achieved for the correlation between p73 and p53 immunoexpression and clinicopathological parameters for buccal carcinomas (P > 0.05; Fisher's exact test). Our results indicate that both p73 and p63 may be involved in the development of human buccal squamous-cell carcinoma, perhaps in concert with p53.