Expression of the cell cycle regulation proteins p53 and p21WAF1 in different types of non-dysplastic leukoplakias

Objectives: The aim of this study was to analyze the immunolabeling of two cell cycle protein regulators, p53 and p21(WAF1), in non-dysplastic leukoplakias with different epithelial alterations: acanthosis, hyperkeratosis and acanthosis combined with hyperkeratosis, and compare them with dysplastic leukoplakias. Material and Methods: This was a prospective cohort study involving 36 patients with oral homogeneous leukoplakias. Excisional biopsies were performed and the patients remain under clinical follow-up. The leukoplakias were divided into four groups: 6 acanthosis, 9 hyperkeratosis, 10 acanthosis combined with hyperkeratosis, and 11 epithelial dysplasias. Paraffin-embebeded sections were immunostained for p53 and p21(WAF1). Five hundred cells from the basal layer and 500 from the parabasal layer were counted to determine the percentage of positive cells. A qualitative analysis was also carried out to determine the presence or absence of immunohistochemical staining in the intermediate and superficial layers. Groups were compared with ANOVA (p<0.05). Pearson's correlation coefficient was used to test for associations between the two markers, p53 and p21(WAF1). Results: No leukoplakia recurred and no malignant transformation was observed whitin a follow-up period of 3-6 years. The mean percentage of p53 staining in the basal and parabasal layers was similar in all groups. p21(WAF1) staining differed between layers was as follows: in the basal, only 3 to 4% of cells were stained, while in the parabasal, between 16 and 28% of the epithelial cells were stained in the four different studied groups with no statistically significant difference (p>0.05). Conclusions: Our findings failed to differentiate the non-dysplastic lesions by means of p53 and p21(WAF1) immunostaining, notwithstanding similar profiles between non-dysplastic and dysplastic leukoplakias were observed.