Oncogene activation in pituitary tumors

Promoter mutations are no major cause of PTTG overexpression in pituitary adenomas

OBJECTIVE

The pituitary tumour transforming gene (PTTG) was proven to cause transformation of NIH3T3 fibroblasts, which produce tumours when transplanted into immunodeficient mice. PTTG is overexpressed in about 90% of pituitary adenomas. The reason for its overexpression is still unclear.

DESIGN

Because promoter mutations may play a role for an altered regulation of PTTG transcription in the pituitary adenomas, we analysed two promoter regions which were characterized previously as functionally important.

PATIENTS

Twenty-five patients of both sexes with pituitary adenomas, mainly null-cell adenomas, were included in this study.

MEASUREMENTS

Both DNA regions were amplified from paraffin sections by PCR and analysed for small deletions or insertions on polyacrylamide gels in all patients. In 16 cases both DNA regions were sequenced to detect base substitutions.

RESULTS

No deletions/insertions and no tumour-specific substitutions were found. In three homopolymeric regions a polymorphism was detected, which also occurred in control sequences. In addition, these tracts showed some degree of length instability.

CONCLUSIONS

Promoter mutations do not play a major role for the enhanced PTTG transcription in pituitary adenomas. Therefore, DNA-binding proteins, hypomethylation or other epigenetic factors may be responsible for PTTG overexpression.

Pituitary tumor diagnosis and treatment

Over the past few years, significant contributions have been made to the understanding, diagnosis, and treatment of pituitary tumors. This article reviews recent advances in the areas of biology, diagnostic imaging, medical diagnosis and treatment, surgical results and technique, and adjuvant therapy in the form of radiotherapy and radiosurgery. Of particular note are the roles of endoscopy, intraoperative magnetic resonance imaging, radiosurgery, and radiation for nonfunction tumors, the diagnosis of Cushing's disease, the management of "incidentalomas," and new medication therapies.