Effect of radiotherapy on expression of transmembrane mucin MUC1 in oral mucosal cells

Abstract Objective: Mucins form a protective surface called mucosal pellicle on oral epithelium. Mucin — 1 (MUC1) is secreted from the oral mucosal squamous epithelium itself on the apical surface of the epithelial cell. The objective of this study was to determine the effect of radiotherapy (RT) on MUC1 expression of the oral epithelium in patients with head and neck cancer (HNC). Methods: Oral mucosal tissue biopsies were obtained from 55 patients; Study group 1 consisted of 33 clinically healthy subjects as controls. The oncology group consisted of two subgroups: Group 2 consisted of 7 oral cancer patients treated with surgery without RT, and Group 3 consisted of 15 HNC patients treated with RT. To visualized MUC1 staining, HMFG1 antibody was used. In addition, microstructures of the specimens were studied under electron microscopies. Results: The superficial layer of the oral epithelium had strong MUC1 staining in control samples compared to oncological groups (p=0.002). Intermediate layer showed the most expression of MUC1 in irradiated mucosa (p=0.02). In both oncological groups, the expression of MUC1 was detected on the basal layer (p=0.005). Morphological analysis with electron microscopies showed destruction in the microstructure of apical cells of the irradiated oral epithelium. Irradiated oral mucosa with strong MUC1 expression showed loose intercellular bonds. Conclusion: Radiotherapy affects the expression of MUC1 in basal and intermediate layers of oral epithelium. Irradiation alters or hinders the intra and intercellular linkages which affects the normal apical transportation of MUC1 and hence, such alteration may play a role in promoting radiation — induced complications