In earlier work, we demonstrated that 0.1 p. 100 topical
tretinoin is clinically effective and well tolerated compared with placebo for the treatment of
oral leukoplakia and oral keratosic or erythematous
lichen planus. Here we aimed to complete this clinical protocol with histological and biochemical analyses comparing the biopsy specimens collected at inclusion and those collected after 4 months of treatment. Histological results were based on changes in keratinization observed between onset of treatment and 4 months treatment. Biochemical studies included the use of
antibodies (anti-cytokeratins 10-11, anti-filaggrine) for the immunohistochemical evaluation of keratinization and 2-dimensional gel electrophoresis for measuring cytokeratins. In patients with
lichen planus, histological changes during treatment showed that, in the 10 patients in the
tretinoin group, keratinization disappeared in 6 and decreased significantly in 3. Immunohistochemistry revealed that cytokeratins 10-11 and
filaggrin disappeared in 57 p. 100 of the patients treated with
tretinoin versus 25 p. 100 in the patients given placebo. Bidimensional gel electrophoresis showed that cytokeratins 1, 2, 10 and 11 disappeared only in the
tretinoin group (60 p. 100 of the cases). In patients with
leukoplakia, histological changes during treatment showed that, in the
tretinoin group, keratinization disappeared in 5 cases and decreased in 5 others. Immunohistochemistry revealed that cytokeratins 10-11 disappeared in 30 p. 100 of the patients treated with
tretinoin versus 25 p. 100 in the placebo group. Bidimensional electrophoresis demonstrated that cytokeratins 1, 2, 10 and 11 disappeared in 43 p. 100 of the patients treated with
tretinoin.