Anti-Sp17 monoclonal antibody with antibody-dependent cell-mediated cytotoxicity and complement-dependent cytotoxicity activities against human ovarian cancer cells.

Sperm protein 17 (Sp17) is a cancer testis antigen that has been shown to be overexpressed in a variety of gynecologic malignancies, in particular ovarian cancer. Emerging evidences indicate that Sp17 is involved in tumorigenesis and in the migration of malignant cells. It has been proposed as a useful target for tumor-vaccine strategies and a novel marker to define tumor subsets and predict drug response. However, the antitumor activity of anti-Sp17 monoclonal antibody (anti-Sp17 mAb) has not been investigated. In this study, the in vitro cytotoxicity, antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) activities of anti-Sp17 mAb were evaluated using Sp17-positive ovarian cancer cells as targets, Sp17-negative ovarian cancer cells as the control, and healthy human peripheral blood monocytes and healthy human serum as effectors. Our preliminary results indicate that the direct cytotoxicity of anti-Sp17 mAb against the investigated ovarian cancer cells was very weak. However, the cytotoxicity of anti-Sp17 mAb, mediated by peripheral blood mononuclear cells (PBMCs), as ADCC, or by human serum, as CDC, was relatively strong in the Sp17-positive ovarian cancer cells. This finding suggested that anti-Sp17 mAb could be a useful tool against ovarian cancer and may provide insight into the development of low side-effect targeting therapy for this malignant disease.