Relationship between the epithelial expression of hMLH1, MDM2, and p63 and lower lip carcinogenesis.

OBJECTIVES: To evaluate the relationship between the epithelial expression of hMLH1, MDM2, and p63 in lower lip carcinogenesis, comparing the immunostaining of these proteins in cases of actinic cheilitis (AC) and lower lip squamous cell carcinoma (SCC). STUDY DESIGN: Forty cases of AC and 40 cases of SCC were studied, both lesions were of lower lip. Histological sections of 3 mum were submitted to immunoperoxidase method, and 1000 cells were counted for immunohistochemical analysis of lesions. The results were analyzed quantitatively, and expression was compared by the Mann-Whitney, Student t-test, or one-way ANOVA, adopting a level of significance of 5%. RESULTS: A higher percentage of epithelial cells expressing hMLH1 was observed in cases of AC without dysplasia or mild dysplasia (721.23 +/- 88.116), whereas fewer positive cells were observed in lower lip SSCs (255.03 +/- 199.47) when compared to the AC group (P < 0.001). Immunoexpression of MDM2 was higher in SCCs of the lower lip compared with AC (P = 0.019). For p63 protein, the expression was higher in AC than in SCC (P = 0.045). CONCLUSION: The present results showed changes in the immunoexpression of hMLH1, MDM2, and p63 in epithelial cells from premalignant and malignant lip disease, supporting the hypothesis that these alterations are related to the process of lower lip carcinogenesis.