RESUMO
BACKGROUND: Both hMSH2 and hMLH1 are integrated in the DNA mismatch repair (MMR) system. Reduced expression of these proteins has been reported in head and neck carcinoma; however, few studies have examined the normal levels of these proteins in oral tissues or investigated factors which could interfere with this expression. The aim of this study was to detect the expression pattern of hMSH2 and hMLH1 in normal oral mucosa and to correlate this with demographic data, smoking and local inflammation. MATERIALS AND METHODS: The expression of hMSH2 and hMLH1 was evaluated in 38 samples of normal mucosa epithelium using immunohistochemistry. RESULTS: No relationship was observed between hMSH2 and hMLH1 and demographic data. The hMLH1 but not hMSH2 expression was altered in smokers and in the presence of inflammation. CONCLUSION: Both hMSH2 and hMLH1 are highly expressed in the normal epithelium of oral mucosa. In addition, hMLH1 expression is directly influenced by tobacco use and inflammation.