PTTG is a Secretory Protein in Human Pituitary Adenomas and in Mouse Pituitary Tumor Cell Lines

The pituitary tumor-transforming gene (PTTG) is a homolog of yeast Securin, which arrests the activation of Separin to induce sister chromatid separation in the transition from metaphase to anaphase. Pituitary tumor-transforming gene is also known to induce angiogenesis during pituitary tumorigenesis. It has not been clarified whether PTTG functions as a cytoplasmic or a nuclear protein. Our immunohistochemical study indicated that PTTG is localized in the cytoplasm of pituitary tumor cells. In the present study, confocal laser scanning microscopy (CLSM) analysis of human pituitary adenomas and immunoelectron microscopy of the mouse pituitary cell line, AtT-20, demonstrated the localization of PTTG in the Golgi apparatus and vesicles. Secreted PTTG was detected by immunoblotting from culture medium of mouse pituitary tumor cell lines. Our results suggested that PTTG is a secretory protein produced by pituitary tumor cells. In addition, PTTG may exert autocrine and/or paracrine functions as a newly proposed important pathway for the action of PTTG.