Expression of syndecan-1 in salivary gland carcinomas and lymph node metastases of salivary duct carcinoma and its potential as therapeutic target

Recurrent/metastatic salivary gland carcinomas (SGC) often lack therapeutic options. For indatuximab ravtansine, an antibody-drug conjugate that binds to syndecan-1, promising clinical data for multiple myeloma and preclinical data for triple-negative breast carcinoma are available. Immunohistochemistry for syndecan-1 was performed for patients with primary SGC of the parotid/submandibular gland and sufficient FFPE tissue who had undergone surgery with curative intent between 1990 and 2019. Results were validated by matrix-assisted laser desorption ionisation mass spectrometry (MALDI-MS). Syndecan-1 expression was correlated with clinicopathological data. One hundred and eleven primary SGC and 13 lymph node metastases of salivary duct carcinomas (SaDu) were included. Membranous expression of syndecan-1 was found in 60 % of all SGCs, with expression varying by entity (p<0.01). A mean of 25.2% of tumor cells in mucoepidermoid carcinoma (MuEp), 20.9% in epithelial-myoepithelial carcinoma, 16.0% in acinic cell carcinoma and 15.2% in SaDu showed syndecan-1 expression. In high-/intermediate-grade MuEp, syndecan-1 expression was seen in 34.8% of tumor cells. Lymph node metastases of SaDu showed syndecan-1 expression in 31.2%. MALDI-MS confirmed the presence of syndecan-1 in eight SGCs. There was no significant association between clinicopathological data, including progression-free survival (p = 0.50), and syndecan-1 expression. Syndecan-1 is expressed in the membrane of different entities of SGC and SaDu lymph node metastases and therefore represents a potential therapeutic target for indatuximab ravtansine.

Publication History

Article published online:
12 May 2023