Tetraspanin CD81 is expressed in human parotid cancer tissue and mediates cell proliferation

Abstract Objectives CD81, a transmembrane protein belonging to the tetraspanin family, has recently attracted attention as a therapeutic target for cancer owing to its important role in human cancer biology; however, there is no previous knowledge regarding CD81 expression in parotid cancer. Therefore, this study aimed to investigate CD81 expression in human parotid cancer and its involvement in cell proliferation. Materials and Methods Tissue samples were collected from 36 patients with parotid cancer, including 10 with salivary duct carcinoma (SDC), 16 with mucoepidermoid carcinoma (MEC), 5 with adenoid cystic carcinoma (ACC), and 5 with carcinoma ex pleomorphic adenoma (Ca ex PA). CD81 expressions in parotid cancer tissues were evaluated using western blotting and immunohistochemistry. Parotid cancer cell lines were established and the effect of suppressing CD81 expression by small interfering RNA (siRNA) and the effect of our anti-CD81 monoclonal antibody on the growth of parotid cancer cells were evaluated. Results The immunohistochemical expressions of CD81 on tumor cell membranes were observed in SDC and MEC tissues but not in ACC and Ca ex PA tissues. Furthermore, inhibition of CD81 expression by siRNA suppresses the growth of parotid cancer cells, and the mouse monoclonal antibody against CD81 inhibited parotid cancer cell growth in a concentration-dependent manner. Conclusions We confirmed the expressions of CD81 in SDC and MEC tissues and showed that its inhibition suppressed the growth of parotid cancer cells. Clinical Relevance These findings provide primary data for the therapeutic targeting of CD81 in parotid cancer.