Pattern of SMC4 Gene Expression in Human Salivary Gland Tumors

抄録

Structural maintenance of chromosomes 4 (SMC4), a member of SMC protein family, was overexpressed in numerous human epithelial tumors, such as colorectal cancer, hepatocellular carcinoma and so on, suggesting an significant promotion role in tumor progression. However, the expression pattern and potential role of SMC4 in salivary gland tumors (SGTs) were not clear. The aim of this study was to detect the expression pattern of SMC4 in normal salivary glands and three SGTs in order to discuss the role of SMC4 and find a new therapeutic target. SMC4 expression patterns were examined immunohistochemically in 20 normal salivary glands and 94 SGTs. In normal salivary glands, SMC4 strongly expressed in cytoplasm of ductal epithelial cells, and hardly expressed in the abluminal (myoepithelial) cells and luminal (epithelial) cells of seromucous acini. In salivary adenoid cystic carcinoma (SACC), we detected that SMC4 showed positive expression on cytoplasm and no significant difference among tubular, cribriform and solid SACC tissues (5/15; 33.3%, 5/15; 33.3%, 8/20; 40%). SMC4 was negative or weakly expressed in cytoplasm of pleomorphic adenoma (PA) (2/26; 7.7%). The positive rate of SMC4 was 20% (1/5) in well-differentiated mucoepidermoid carcinoma (MEC) and up to 84.6% (11/13) of strong cytoplasmic and nuclear SMC4 expression in poor-differentiated MEC. The sites of SMC4 expressions in MEC tissues were intermediate cells and epidermoid cells. These findings confirmed that SMC4 was negative in benign SGT, but strongly expressed in malignant SGTs especially in MECs. SMC4 may play a key role in poor-differentiated MECs and a specific biomarker for the degree of MEC malignancy.