Targeting the cancer glycocalyx in salivary duct carcinoma: tumor-associated mucin 1 (Tn-MUC1) as a novel cell surface marker.

Despite the use of targeted drugs for human epidermal growth factor receptor type 2 (HER2)-positive salivary duct carcinoma (SDC) treatment, the overall prognosis for SDC remains poor. In this study, we aimed to investigate whether the glycocalyx of SDC cells serves as a potential cell surface marker. To understand the complex structure of the glycocalyx of salivary gland tumors, we used a lectin with glycan-specific binding properties. Lectin staining was performed for five types of common salivary gland tumors. We determined the expression of the transmembrane glycoprotein mucin 1 with Tn antigen (GalNAc), Tn-MUC1, using 20 clinical SDC specimens. Vicia villosa lectin (VVL) was not stained in the vascular endothelium but specifically stained in the SDC tumor cells. GalNAc, to which VVL binds, formed Tn-MUC1 via glycosylation with N-acetylgalactosaminyltransferases (GALNTs). GALNT7 was highly expressed in SDC. Analysis of clinical SDC specimens revealed that Tn-MUC1 was also positive in the SDC tumor cells, suggesting its potential as a cell surface target for SDC.