Expression and localisation of MUC1 modified with sialylated core-2 O-glycans in mucoepidermoid carcinoma

Mucoepidermoid carcinoma (MEC) is the most frequent of the rare salivary gland malignancies. We previously reported high expression of Mucin 1 (MUC1) modified with sialylated core-2 O-glycans in MEC by using tissue homogenates. In this study, we characterised glycan structures of MEC and identified the localisation of cells expressing these distinctive glycans on MUC1. Mucins were extracted from the frozen tissues of three patients with MEC, and normal salivary glands (NSGs) extracted from seven patients, separated by supported molecular matrix electrophoresis (SMME) and the membranes stained with various lectins. In addition, formalin-fixed, paraffin-embedded sections from three patients with MEC were subjected to immunohistochemistry (IHC) with various monoclonal antibodies and analysed for C2GnT-1 expression by in situ hybridisation (ISH). Lectin blotting of the SMME membranes revealed that glycans on MUC1 from MEC samples contained alpha 2,3-linked sialic acid. In IHC, MUC1 was diffusely detected at MEC-affected regions but was specifically detected at apical membranes in NSGs. ISH showed that C2GnT-1 was expressed at the MUC1-positive in MEC-affected regions but not in the NSG. MEC cells produced MUC1 modified with alpha 2,3-linked sialic acid-containing core-2 O-glycans. MUC1 containing these glycans deserves further study as a new potential diagnostic marker of MEC.

Automated summary

In this study, the authors investigated the glycan structures of Mucoepidermoid carcinoma (MEC) and the expression of Mucin 1 (MUC1) modified with sialylated core-2 O-glycans. They found that MUC1 in MEC samples contained alpha 2,3-linked sialic acid, while MUC1 in normal salivary glands (NSGs) did not. Further analysis revealed that C2GnT-1, an enzyme involved in the synthesis of these glycans, was expressed in MEC-affected regions but not in NSGs. These findings suggest that MUC1 containing these glycans could be a potential diagnostic marker for MEC.