Differential expression of topoisomerase IIα protein in salivary gland carcinomas: histogenetic and prognostic implications

Salivary gland carcinomas are relatively uncommon heterogeneous malignancies characterized by locoregional invasion and distant metastasis. Topoisomerase IIα (topoIIα), located at chromosome 17q21-22, is considered a major mediator of cell proliferation and DNA replication. The purpose of this study was to evaluate the expression of topoIIα in various types of salivary gland tumors and its biological significance. The protein expression of topoIIα was evaluated immunohistochemically in formalin-fixed, paraffin-embedded tissue from 54 salivary gland carcinomas and 20 benign tumors (10 pleomorphic adenomas and 10 Warthin's tumors). The primary salivary gland carcinoma specimens consisted of 17 adenoid cystic carcinomas, 7 adenocarcinomas not otherwise specified, 7 mucoepidermoid carcinomas, 6 salivary duct carcinomas, 3 acinic cell carcinomas, 3 carcinomas ex pleomorphic adenomas, 3 epithelial-myoepithelial carcinomas, 2 carcinosarcomas, 2 lymphoepithelial carcinomas, 2 myoepithelial carcinomas, 1 oncocytic carcinoma, and 1 squamous cell carcinoma. The associations between clinicopathological factors and outcome were analyzed. Of the 54 primary salivary gland carcinomas, 38 (70%) showed positive expression (≥10%) of topoIIα protein, and 16 carcinomas (30%) and all benign tumors were negative (p < 0.001). Expression of topoIIα was more frequently observed in salivary duct carcinoma, carcinoma ex pleomorphic adenoma, adenocarcinoma, and adenoid cystic carcinoma, solid type, and it was associated with advanced stage and shortened survival. The results of the present study suggest that topoIIα expression is associated with histologically aggressive subtypes and shortened survival. Furthermore, it may provide useful prognostic information and suggests the potential efficacy of topoIIα-targeting therapy in patients with salivary gland carcinoma