Overexpression of prothymosin alpha is related to pituitary adenoma recurrence but not to adenoma invasiveness and proliferation.

Introduction: Prothymosin alpha (ProTα) is a peptide initially considered as a thymic hormone, but further studies have shown its wide distribution in different tissues and organs. It has a prevalent nuclear localisation and is thought to be involved in the control of proliferation and apoptosis. In earlier studies, the overexpression of ProTα was found in several human tumours, including pituitary adenomas. The present study deals with the relations of ProTα to the pituitary adenoma hormonal phenotype, proliferation, recurrence and invasiveness.

Material And Methods: Sixty two pituitary adenomas were included in the study. The invasiveness of the tumours was estimated before surgery by means of magnetic resonance imaging. The paraffin sections of the tumours were immunostained with an antibody against the C-terminal fragment (101-109) of ProTα and with anti-Ki-67 antibody. The hormonal phenotype of the investigated pituitary adenomas had been established previously by means of immunostaining with antibodies to pituitary hormones (GH, PRL, FSH, LH, TSH, ACTH and α-subunit).

Results: Strong immunostaining with anti-ProTα antibody occurred in the subpopulation of cell nuclei and the walls of intratumoural blood vessels. ProTα index is higher in clinically non-functioning pituitary adenomas (CNFPA) compared to any type of functioning adenomas. There was no difference in the percentage of ProTα- positive cell nuclei in non-invasive vs. invasive adenomas, but it was significantly more frequent in recurrent than in primary tumours. Moreover, the decrease of ProTα index was found in somatotroph tumours treated with somatostatin analogues vs. untreated ones. The percentage of ProTα nuclei did not correlate with Ki-67 index.

Conclusions: The overexpression of nuclear ProTα in pituitary adenomas is related to tumour recurrence, but not to proliferation or invasiveness.