Estudo imuno-histoquímico da expressão de metalotioneína e proteína p16 em líquen plano e reações liquenóides orais

Abstract

Lichen planus is a chronic inflammatory disease mediated by T cells of unknown cause. Skin, nails and mucous membranes can be affected, and the disease is more common in middleaged adults, especially in women. Oral lichen planus (OLP) manifests as reticular (white) and erosive (red) lesions that are eventually painful. Histologically, it is characterized by dense lymphocytic infiltrate beneath the epithelium, apoptosis of keratinocytes, liquefaction of the basal layer, epithelial hyperplasia and hyperkeratosis. Oral lichenoid reactions (OLR) are distinguished from OLP by the presence of precipitating factors, unilateral lesions and diffuse inflammatory infiltrate. Metallothionein is a protein involved in anti-oxidative response and anti-apoptotic pathways. Ki-67 is a cellular proliferation marker and is expressed only in cells that are in cell division (phases G1, S, G2 and M of the cell cycle). The tumor suppressor gene p16 is involved in the pRb pathway and participates in the regulation of the cell cycle, repairing possible damage to DNA. The aim of this study was to evaluate possible molecular differences, related to oxidative stress and cell proliferation between OLP and OLR, and the two major forms of OLP in order to better understand the pathogenesis of these lesions and facilitate the differential diagnosis between them. Immunohistochemistry for metallothionein, Ki-67 and p16 detection was performed in 42 and 23 cases of OLP and OLR, respectively. Reactivity for metallothionein was more frequently observed in OLP cases than in OLR cases (p = 0,01; Mann-Whitney U test). Significant difference was found between the reticular and atrophic lesions of OLP for p16 protein (p = 0,04; Mann-Whitney U test). There was no significant difference between the lesions in relation to Ki-67 antigen. The results of this study suggest that metallothionein protein may be a useful marker of differential diagnosis between OLP and OLR, and that p16 protein may be a differential marker of reticular and atrophic/erosive lesions of OLP.