Mucoepidermoid carcinoma-associated expression of MUC5AC, MUC5B and mucin-type carbohydrate antigen sialyl-Tn in the parotid gland.

OBJECTIVE

The aberrant expression of mucins and mucin-type carbohydrates has been described in many types of cancer, including mucoepidermoid carcinoma (MEC), a malignant salivary gland tumor. In this study, we examined the aberrant expression patterns of mucins (MUC1, MUC4, MUC5AC and MUC5B), simple mucin-type carbohydrate antigens (Tn, sialyl-Tn and T) and mature carbohydrate antigens (Lewisa and sulfo-Lewisa antigens) in MEC originating from the parotid gland, which normally does not secrete mucins.

METHODS

We conducted an immunohistochemical study to investigate the presence of mucins and carbohydrates in 24 MEC samples originating from the parotid gland and in surrounding normal tissue of the same gland in comparison 6 samples of normal salivary glands. The expression levels were compared with respect to the histological grading. Furthermore, 24 MEC samples from non-parotid salivary glands were included.

RESULTS

We observed loss of topology of membrane-bound MUC1 and MUC4, and de novo expression of MUC5AC, MUC5B and sialyl-Tn in MEC that originated in the parotid gland. Furthermore, mucins MUC1, MUC4 and carbohydrate antigens Tn, sialyl-Tn, T, Lewisa and sulfo-Lewisa were overexpressed in MEC samples compared to surrounding normal salivary gland tissues. MUC1 was expressed in both low- and high grade MECs, whereas MUC4 was not expressed in high grade MECs of the parotid gland.

CONCLUSIONS

During the development of MEC in the parotid gland, the genes for gel-forming secretory mucins are switched on. Besides these MEC tissues overexpress short oligosaccharides, suggesting that the glycosylation machinery is altered.