Oral leukoplakias with different degrees of dysplasia: comparative study of hMLH1, p53, and AgNOR.

Background: hMLH1 is one of the major proteins of the mammalian mismatch repair system. It has been suggested that the mismatch repair machinery could be linked to p53, a tumor suppressor protein. The AgNOR technique is used to assess cell proliferation. The aim was to compare the immunoexpression of hMLH1 and p53, and AgNOR number in oral leukoplakias with different degrees of dysplasia.

Methods: Sixty-two samples were evaluated by immunohistochemistry for hMLH1 and p53, and AgNOR technique, being 17 without dysplasia, 19 with mild dysplasia, 16 with moderate dysplasia, and 10 with severe dysplasia.

Results: hMLH1 immunoexpression showed decreasing indexes, while p53 and AgNOR showed increasing indexes from lesions with lower degrees of dysplasia to lesions with more severe dysplasia. An inverse correlation between hMLH1 and both p53 and AgNOR, and a direct correlation between p53 and AgNOR were observed.

Conclusions: Alterations in the immunoexpression pattern of hMLH1 and p53 seemed to be early events in oral carcinogenesis. During acquisition of a more dysplastic phenotype, keratinocytes may show diminished capacity of DNA repair and tumor suppression, as well as higher cellular proliferation, and these pathways can be somehow interconnected.