Sperm protein 17 (Sp17, gene SPA17) is a highly conserved, immunogenic protein expressed at low levels in normal somatic tissues and highly expressed in testis and a variety of malignant cells. Sp17 has been studied extensively in the context of mammalian sperm function. However, the function of Sp17 in normal somatic and malignant cells is poorly understood. We developed monoclonal antibodies specific for Sp17 and examined subcellular localization of the protein by immunocytochemistry and immunofluorescence. In normal tissues, immunofluorescent staining of mature sperm showed strong staining of Sp17 in the flagella. Sp17 staining was also strong in other normal ciliated cells, including ciliated epithelia cells of the fallopian tube and bronchus, suggesting a normal role for this protein in the function of motile cilia. Immunofluorescent analysis of Sp17 expression in an in vitro model of primary ciliogenesis, the renal tubule cell line mCCD, demonstrated localization of the protein in the basal bodies, suggesting a role for Sp17 in the function of primary, nonmotile cilia as well. Immunofluorescent studies of immortalized tumor cell lines demonstrated Sp17 localization to centrosomes. Tissue microarray analysis of breast and ovarian tumors demonstrated overexpression of Sp17 protein in the majority of tumor samples. Sp17 localized to the nucleus in most samples, with some samples exhibiting predominantly cytoplasmic staining. Localization of Sp17 to the centrosome has not been previously reported, and suggests a new role for this protein in normal somatic and malignant cells.
[Proc Amer Assoc Cancer Res, Volume 46, 2005]