Study of major genetic factors involved in pituitary tumorigenesis and their impact on clinical and biological characteristics of sporadic somatotropinomas and non-functioning pituitary adenomas

Genetic and functional aberrations of guanine nucleotide-binding protein, alpha stimulating (GNAS), aryl hydrocarbon receptor interacting protein (AIP), and pituitary tumor transforming gene (PTTG) are among the most prominent events in pituitary tumorigenesis. A cohort of Brazilian patients with somatotropinomas (n=41) and non-functioning pituitary adenomas (NFPA, n=21) from a single tertiary-referral center were evaluated for GNAS and AIP mutations and gene expression of AIP and PTTG. Results were compared to the clinical and biological (Ki67 and p53 expression) characteristics of tumors and their response to therapy, if applicable. Genetic analysis revealed that 27% of somatotropinomas and 4.8% of NFPA harbored GNAS mutations (P=0.05). However, no differences were observed in clinical characteristics, tumor extension, response to somatostatin analog therapy, hormonal/surgical remission rates, Ki67 index, and p53 expression between mutated and non-mutated somatotropinomas patients. PTTG overexpression (RQ mean=10.6, min=4.39, max=11.9) and AIP underexpression (RQ mean=0.56, min=0.46-max=0.92) were found in virtually all cases without a statistically significant relationship with clinical and biological tumor features. No patients exhibited somatic or germline pathogenic AIP mutations. In conclusion, mutations in GNAS and abnormal PTTG and AIP expression had no impact on tumor features and treatment outcomes in this cohort. Our data support some previous studies and point to the need for further investigations, probably involving epigenetic and transcriptome analysis, to improve our understanding of pituitary tumor behavior.

Recent Progress in the Medical Therapy of Pituitary Tumors

Management of pituitary tumors is multidisciplinary, with medical therapy playing an increasingly important role. With the exception of prolactin-secreting tumors, surgery is still considered the first-line treatment for the majority of pituitary adenomas. However, medical/pharmacological therapy plays an important role in controlling hormone-producing pituitary adenomas, especially for patients with acromegaly and Cushing disease (CD). In the case of non-functioning pituitary adenomas (NFAs), pharmacological therapy plays a minor role, the main objective of which is to reduce tumor growth, but this role requires further studies. For pituitary carcinomas and atypical adenomas, medical therapy, including chemotherapy, acts as an adjuvant to surgery and radiation therapy, which is often required to control these aggressive tumors. In the last decade, knowledge about the pathophysiological mechanisms of various pituitary adenomas has increased, thus novel medical therapies that target specific pathways implicated in tumor synthesis and hormonal over secretion are now available. Advancement in patient selection and determination of prognostic factors has also helped to individualize therapy for patients with pituitary tumors. Improvements in biochemical and “tumor mass” disease control can positively affect patient quality of life, comorbidities and overall survival. In this review, the medical armamentarium for treating CD, acromegaly, prolactinomas, NFA, and carcinomas/aggressive atypical adenomas will be presented. Pharmacological therapies, including doses, mode of administration, efficacy, adverse effects, and use in special circumstances are provided. Medical therapies currently under clinical investigation are also briefly discussed.

Correlation between Pituitary Insufficiency and Magnetic Resonance Imaging Finding in Non-Functioning Pituitary Adenomas

BACKGROUND: Non-functioning pituitary adenomas (NFPAs) are characterized by the absence of clinical and biochemical evidence of pituitary hormone hypersecretion, and these tumors constitute approximately one third of all the tumors of the anterior pituitary. Recently, hormonal deficiencies have gradually evolved to become the leading presenting signs and symptoms in patients with NFPAs. We investigated pituitary hormonal insufficiencies according to the magnetic resonance imaging (MRI) findings in patients with NFPA. METHODS: We evaluated the patients who were newly diagnosed with NFPA from 1997 through 2009. Among them, we analyzed 387 patients who were tested for their combined pituitary function and who underwent MRI. The severity of the hypopituitarism was determined by the number of deficient axes of the pituitary hormones. On the MRI study, the maximal diameter of the tumor, Hardy's classification, the thickness of the pituitary gland and the presence of stalk compression were evaluated. RESULTS: The mean age was 46.85 +/- 12.93 years (range: 15-86) and 186 patients (48.1%) were male. As assessed on MRI, the tumor diameter was 27.87 +/- 9.93 mm, the thickness of the normal pituitary gland was 1.42 +/- 2.07 mm and stalk compression was observed in 201 patients (51.9%). Hypopituitarism was observed in 333 patients (86.0%). Deficiency for each pituitary hormone was most severe in the patients with Hardy type IIIA. Hypopituitarism was severe in the older age patients (P = 0.001) and the patients with a bigger tumor size (P < 0.001) and the presence of stalk compression (P < 0.001). However, the patients who had a thicker pituitary gland showed less severe hypopituitarism (P < 0.001). Multivariate analysis showed that age, tumor diameter and the thickness of pituitary gland were important determinants for pituitary deficiency (P = 0.004, P < 0.001, P = 0.022, respectively). CONCLUSION: The results suggest that the hormonal deficiencies in patient with NFPA were correlated with the MRI findings, and especially the tumor diameter and preservation of the pituitary gland.