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 radiationinduced complications.

Irradiation Alters the Expression of MUC1, CD44 and Hyaluronan in Oral Mucosal Epithelium

“…Our results showed that plasma membrane and intracellular staining of HA and CD44 extended up to involve the superficial layers of epithelium, possibly due to co-localization of HA and CD44 in irradiated tissue or upregulation of HA and CD44 production due to some persistent inflammatory stimulus following RT. Moreover, HA and CD44 expression did not correlate with the local dose of radiation and the time interval between RT and biopsy, such as the MUC1 expression, as shown previously [ 12 ].…”

“…MUC1 staining was performed using a Dako EnVision K 5007-kit (Dako, Glostrup, Denmark) as described in a previous study [ 12 ]. The method followed for IHC staining was as per the manufacturer‘s instructions (Abcam, Cambridge, UK).…”

“…An ordered recording was carried out for staining distribution in the basal, intermediate, and superficial layers of the oral mucosal epithelium, as shown in Figure 1 . The staining intensity for MUC1, CD44, and HA was estimated as described previously: 0 = no staining, 1 = some staining, 2 = considerable staining [ 12 ].…”

“…Transmission electron microscopy was used to investigate cell-cell interaction with higher magnification. The samples were post-fixed in 2% osmium tetroxide with a cacodylate buffer solution at 4 °C for two hours before rinsing with cacodylate buffer solution, dehydrating in graded ethanol, and embedding in epoxy resin as described previously [ 12 ]. Semi-thin sections were made with an ultramicrotome and stained with 1% toluidine blue and examined with a light microscope to find a correct area for TEM investigations.…”

“…Such differential expression of MUC1 has been associated with tumor cell proliferation, migration, invasion, adhesion, and metastasis. MUC1 was shown to express homogeneously in the layers of irradiated tissue samples suggesting changes in the genome and microenvironmental properties of the individual cells that resulted in architectural and hierarchical disturbances in the epithelial cell strata, inter cellular interaction, and cell surface microstructure [ 12 ].…”