Effect of smoking on MUC1 expression in oral epithelial dysplasia, oral cancer, and irradiated oral epithelium

Objectives: The aim of this study was to assess the MUC1 expression in the oral epithelium of normal, oral epithelial dysplasia (OED), oral squamous cell carcinoma (OSCC), and irradiated oral epithelium (IROE) and its association with smoking habits in non-smokers and smokers. Design: Oral mucosal biopsies from controls, OED, OSCC, and IROE groups were obtained and categorized based on the smoking history as non-smokers, smoker I (25 pack-years), and smoker II (>25 pack-years). Immunohistochemical staining of MUC1 using human milk fat globule 1 (HMFG 1) antibody was performed, and the MUC1 score was calculated. The relation between MUC1 expression and clinicopathological findings was examined. Results: MUC1 staining of superficial oral epithelial cells with mild MUC1 score was detected in all control samples. The MUC1 staining extended from superficial to basal cell layer of oral epithelium with the increase in MUC1 score from moderate to strong in OED, OSCC, and IROE, and the difference was significant (p < 0.004, p < 0.002 and p < 0.004, respectively) compared to controls. A positive association between smoking and MUC1 score was observed within groups (p < 0.05). Conclusion: The depolarization of MUC1 protein expression is associated with smoking habits in OED and OSCC. In the IROE, the radiation causes subcellular and molecular changes, observed as altered MUC1 expression and accelerated by smoking, furthermore, complicating the oral mucosal adaptation and progress to radiation-induced lesions as a delayed effect.