Survivin products in pituitary tumors.

OBJECTIVES: Survivin is a member of the inhibitor of apoptosis protein family, which was recently showed to be expressed by different benign and malignant human tumors. Still very little is known about survivin expression in pituitary tumors. In spite of the fact that pituitary tumors in histological examination are usually benign, in the clinical process a certain number of pituitary adenomas is capable of aggressive growth, recurrence and invasion of the surrounding structures. The aim of the present study was to assess the presence of survivin transcripts and protein in different types of pituitary tumors and to evaluate survivin expression levels in invasive and non-invasive pituitary tumors.

DESIGN AND METHODS: The analyzed material consisted of tumor tissue samples obtained during standard neurosurgical removal of the tumor from 23 patients in whom acromegaly (n=14), non-functioning pituitary tumor (n=6), prolactinoma (n=2) and corticotropinoma (n=1) were diagnosed. As a control of the study normal pituitary tissue obtained at autopsy was used. Amplification of survivin gene using sequence specific primers and qRT-PCR method and immunohistochemical staining with primary polyclonal antibodies against human survivin were performed.

RESULTS: Our study demonstrated the presence of survivin mRNA in all 23 analyzed pituitary tumors. Survivin expression was also observed in normal pituitary, but the level of its expression was 6-fold lower than in tumors tissue when studied by real time RT-PCR. The difference between the levels of survivin expression in invasive and non-invasive tumors was not statistically significant. Immunohistochemical analyses revealed the presence of the protein in both normal and tumor tissue of pituitary. Immunostaining of tumor tissue was not uniform. Survivin was observed mainly in the nuclei of cells collected in clusters. The presence of the protein in normal pituitary was restricted to small population of cells.

CONCLUSIONS: The present study showed that overexpression of survivin is characteristic for pituitary tumors. Further analysis of this protein expression profile should demonstrate whether survivin might be use as a prognostic marker in diagnosis and therapy of pituitary adenomas.