Genetic factors in the development of pituitary adenomas

Potential biomarkers of miRNA in non-functional pituitary adenomas

BACKGROUND

The abnormal expression of microRNA (miRNA) has been proved to be closely related to the occurrence and progression of tumors. A unique expression of multiple miRNAs has been found in different types of tumors. However, the correlation between miRNA and non-functional pituitary adenoma (NFPA) is not clear. In this study, miRNAs (miRNA-26b, miRNA-138, miRNA-206, and miRNA-let-7e) have been used as detection genes to compare the miRNA expression levels of NFPA subjects and healthy controls and to explore the expression of four different miRNAs in NFPA.

METHODS

Ten untreated NFPA volunteers were served as subjects, and 10 normal subjects were selected as controls. Peripheral blood samples were collected, and four differentiated expressed miRNAs (miRNA-26b, miRNA-138, miRNA-206, and miRNA-let-7e) obtained in the early stage of the test group were detected, recorded, and archived by quantitative real-time PCR (qPCR). The difference and significance of endogenous miRNA expressions were explored through statistical analysis, hoping to find biomarkers for clinical treatment.

RESULTS

The levels of miRNA-26b, miRNA-138, miRNA-206, and miRNA-let-7e in the peripheral serum of patients with NFPA were significantly lower than those in normal subjects (P < 0.05).

CONCLUSION

miRNA-26b, miRNA-138, miRNA-206, and miRNA-let-7e may be involved in the occurrence and progress of NFPAs. This study aims to study the biological targets of NFPA. It starts from the study of whether miRNA, miRNA-26b, miRNA-138, miRNA-206, and miRNA-let-7e may be tumor suppressor genes in NFPA, which provides a basis for further exploration of tumor markers of pituitary adenoma.

Contemporary Management of Clinically Non-functioning Pituitary Adenomas: A Clinical Review

Non-functioning pituitary adenomas (NFPAs) are benign pituitary tumours that constitute about one-third of all pituitary adenomas. They typically present with symptoms of mass effects resulting in hypopituitarism, visual symptoms, or headache. Most NFPAs are macroadenomas (>1 cm in diameter) at diagnosis that can occasionally grow quite large and invade the cavernous sinus causing acute nerve compression and some patients may develop acute haemorrhage due to pituitary apoplexy. The progression from benign to malignant pituitary tumours is not fully understood; however, genetic and epigenetic abnormalities may be involved. Non-functioning pituitary carcinoma is extremely rare accounting for only 0.1% to 0.5 % of all pituitary tumours and presents with cerebrospinal, meningeal, or distant metastasis along with the absence of features of hormonal hypersecretion. Pituitary surgery through trans-sphenoidal approach has been the treatment of choice for symptomatic NFPAs; however, total resection of large macroadenomas is not always possible. Recurrence of tumours is frequent and occurs in 51.5% during 10 years of follow-up and negatively affects the overall prognosis. Adjuvant radiotherapy can decrease and prevent tumour growth but at the cost of significant side effects. The presence of somatostatin receptor types 2 and 3 (SSTR3 and SSTR2) and D2-specific dopaminergic receptors (D2R) within NFPAs has opened a new perspective of medical treatment for such tumours. The effect of dopamine agonist from pooled results on patients with NFPAs has emerged as a very promising treatment modality as it has resulted in reduction of tumour size in 30% of patients and stabilization of the disease in about 58%. Despite the lack of long-term studies on the mortality, the available limited evidence indicates that patients with NFPA have higher standardized mortality ratios (SMR) than the general population, with women particularly having higher SMR than men. Older age at diagnosis and higher doses of glucocorticoid replacement therapy are the only known predictors for increased mortality.

Malignant transformation in non-functioning pituitary adenomas (pituitary carcinoma)

Non-functioning pituitary carcinomas (NFPC) are defined as tumours of adenophyseal origin with craniospinal or systemic dissemination, with the absence of a hormonal hypersecretion syndrome. These are a histologically heterogenous group of tumours, comprising gonadotroph, null cell, "silent" tumours of corticotroph, somatotroph or lactotroph cell lineages as well as plurihormonal Pit-1 tumours. NFPC are exceedingly rare, and hence few cases have been described. This review has identified 38 patients with NFPC reported in the literature. Recurrent invasive non-functioning pituitary adenomas (NFPA) were observed in a majority of patients. Various factors have been identified as markers of the potential for aggressive behaviour, including rapid tumour growth, growth after radiotherapy, gain or shift of hormone secretion and raised proliferative markers. Typically, there is a latency of several years from the original presentation with an NFPA to identification of metastases and only 5 cases reported with rapidly progressive malignant disease within 1 month of presentation. Therapeutic options include debulking surgery, radiation therapy and chemotherapy with temozolomide recommended as first line systemic treatment. Although long-term survivors are described, prognosis remains generally very poor (median survival 8 months). Improvements in molecular tumour profiling may assist in predicting tumour behaviour, guide therapeutic choices and identify novel therapies.

Pituitary Adenoma Associated With Rathke’s Cleft Cyst: Report of 15 Cases

Objective: The concomitant presence of pituitary adenoma (PA) with Rathke’s cleft cyst (RCC) is rare, and most of the literature published is case reports. RCC’s clinicopathological features have not been well described. Methods: We retrospectively reviewed the data of 15 patients with PA associated with RCC. We also provide a systematic review of the literature. Results: The patients included males and seven females. The transsphenoidal approach was adopted for all patients except one, who underwent right frontal craniotomy. Complete resection was achieved in nine cases, with grossly complete resection in five and partial removal in one. Of the PA subtypes available, five patients had nonfunctional pituitary adenomas, three had multiple-hormone secreting PAs, three had prolactin-producing adenomas, and one had a growth hormone-secreting adenoma. All of the patients’ symptoms and abnormal endocrine test results resolved or were relieved after surgery. The mean follow-up time was 27.6±16.6 months. All of the patients recovered well and had no signs of recurrence during their follow-up, except for one patient. Conclusions: A cyst-like signal indicated on images or cystic materials encountered during operation in a patient with PA suggest the possibility of PA associated with RCC. Transsphenoidal surgery is the preferred approach and can resolve or relieve patients’ symptoms to a great extent. Histologically, nonfunctional PA and prolactinoma are the most common types of PA coexisting with RCC; the mechanisms of PA associated with RCC need to be investigated further.

Gene expression profiling analysis of MENX-associated rat pituitary adenomas contributes to understand molecular mechanisms of human pituitary adenomas

The present study aimed to screen potential genes associated with pituitary adenomas to obtain further understanding with regard to the pathogenesis of pituitary adenomas. The microarray GSE23207 dataset, containing 16 pituitary adenoma samples from multiple endocrine neoplasia syndrome-associated rats and 5 normal pituitary tissue samples, was downloaded from Gene Expression Omnibus. The Linear Models for Microarray Data package was used to identify the differentially-expressed genes (DEGs) with the cut-off criteria of a |log₂fold change (FC)|>1 and adjusted P-values of <0.05. The potential functions of the DEGs were predicted by functional and pathway enrichment analysis with the Database for Annotation, Visualization and Integrated Discovery. Furthermore, the interaction associations of the up- and downregulated DEGs obtained from the Search Tool for the Retrieval of Interacting Genes database were respectively revealed by the protein-protein interaction networks visualized with Cytoscape. A total of 391 upregulated and 238 downregulated DEGs in were screened in the pituitary adenoma samples. The upregulated DEGs with a higher degree in the protein-protein interaction network (e.g., CCNA2, CCNB1 and CDC20) were significantly involved in cell cycle and cell division. Notably, PTTG1 was enriched in every functional term. These DEGs interacted with each other. The downregulated DEGs (e.g., GABRA1, GABRA4 and GABRB1) also interacted with each other, and were relevant to neuroactive ligand-receptor interaction; the DEG POU1F1, interacting with POMC, was correlated with the development of the pituitary gland, adenohypophysis and endocrine system. Certain DEGs, including CCNB1, CCNA2, CDC20, GABRA1, GABRA4, GABRB1, POU1F1 and POMC, and particularly PTTG1, were shown to be closely involved in the pathogenesis of pituitary adenomas.

The molecular pathogenesis of pituitary adenomas: an update

Pituitary tumors represent the most common intracranial neoplasms accompanying serious morbidity through mass effects and inappropriate secretion of pituitary hormones. Understanding the etiology of pituitary tumorigenesis will facilitate the development of satisfactory treatment for pituitary adenomas. Although the pathogenesis of pituitary adenomas is largely unknown, considerable evidence indicates that the pituitary tumorigenesis is a complex process involving multiple factors, including genetic and epigenetic changes. This review summarized the recent progress in the study of pituitary tumorigenesis, focusing on the role of tumor suppressor genes, oncogenes and microRNAs.

Wnt4 is overexpressed in human pituitary adenomas and is associated with tumor invasion

The Wnt4 molecule is a secretory glycoprotein implicated in proliferation and differentiation of both normal and malignant cells. Despite extensive investigation of Wnt4 expression in various cancers, little is known about its expression pattern in different types of pituitary tumors. In this study, we examined the expression of Wnt4 and its downstream molecule β-catenin in pituitary adenoma specimens. Pituitary adenoma tissues were collected from 43 patients and four normal pituitary tissue samples were obtained at autopsy. Quantitative real-time reverse transcription polymerase chain reaction (RT-PCR), immunohistochemistry and western blot were performed to detect the expression of Wnt4 and β-catenin mRNA and protein, respectively. Tumor invasion grade (Knosp grade) was determined on MRI images and was correlated to β-catenin expression. Immunohistochemistry demonstrated elevated Wnt4 expression in follicle-stimulating hormone-producing adenomas, growth hormone-producing adenomas, prolactin-producing adenomas, thyroid-stimulating hormone-producing adenomas and non-functioning adenomas, while adrenocorticotropic hormone-producing adenomas showed a low level of Wnt4 expression that was comparable to normal pituitary tissue. These results were confirmed by real-time RT-PCR and western blot analyses. The expression pattern of β-catenin was similar to that of Wnt4 and was inversely correlated to the Knosp grade of tumor invasion. These data indicate that Wnt4 signaling is deregulated in most pituitary adenomas and its excessive activation may inhibit pituitary tumor invasion.

MGMT expression and pituitary tumours: relationship to tumour biology

Over the past half decade, temozolomide, an oral akylating chemotherapeutic agent, has been shown to have significant activity in the management of aggressive pituitary tumours. The expression of 06-methylguanine-DNA methyltransferase (MGMT), a DNA repair enzyme, is an important predictor of response to therapy. Low MGMT expression has been reported with a higher frequency amongst more aggressive pituitary tumours, suggesting MGMT may play a role in pituitary tumour progression. In this study, we performed a microarray analysis to determine whether there was a distinct gene expression profile between tumours with low MGMT and high MGMT expression. Overall, 1,403 differentially expressed genes were identified with raw p values less than 0.05. Gene set enrichment analysis (GSEA) revealed significant differences in the gene expression profile between high and low MGMT expressing pituitary tumours. High MGMT expressing pituitary tumours were found to have upregulation of components of the FGFR family and downstream signaling cascades such as PI3 K/Akt and MAPK pathways. Activation of genes involved in the DNA damage response and DNA repair pathways, as well as genes involved in transcription, were identified in pituitary tumours with low MGMT expression. These results form the basis of our proposed model to describe the role of MGMT in pituitary tumorigenesis.

Pituitary adenoma pathogenesis: an update

PURPOSE OF REVIEW

To describe the recent efforts to understand the molecular and genetic mechanisms involved in the tumorigenesis of pituitary adenomas.

RECENT FINDINGS

There is rapidly accumulating evidence for the roles of molecular abnormalities in pituitary adenoma tumorigenesis, including dysregulation of the cell cycle, signal transduction pathways, oncogenes and tumor suppressor genes. MicroRNAs have been identified as important participants in gene regulation and may have a role in therapy. Stem cells have also provided novel concepts for tumorigenesis and potentially treatment.

SUMMARY

Pituitary adenomas are relatively common neoplasms, whose pathogenesis is still poorly understood. Although considered by many as benign monoclonal proliferations, their clinical spectrum is diverse including hormone hypersecretion, and various degrees of invasiveness, suggesting multiple steps and mechanisms. This review summarizes recent development in the molecular tumorigenesis of pituitary adenomas emphasizing the dysregulation of the cell cycle components, tumor suppressor genes, oncogenes, stem cells and microRNAs.

Lack of mutations in the gene coding for the hGR (NR3C1) in a pediatric patient with ACTH-secreting pituitary adenoma, absence of stigmata of Cushing's syndrome and unusual histologic features

BACKGROUND

Rare cases of human glucocorticoid receptor (hGRalpha) (NR3C1) gene mutations have been described in the gemline or somatic state in Cushing's disease (CD).

AIM

We describe a pediatric patient with CD with clinical evidence of partial glucocorticoid resistance (GR) due to the relative absence of stigmata of Cushing's syndrome (CS).

CASE DESCRIPTION

A 14-year-old boy with slow growth and hypertension, but no other signs of CS was admitted for CD evaluation. Urinary free cortisol levels (UFC) were consistently 2-3-fold the upper normal range. Pituitary magnetic resonance imaging (MRI) revealed a 3x4 mm hypoenhancing lesion in the right side of the pituitary gland anteriorly (microadenoma). A graded dexamethasone suppression test indicated that the patient had partial GR. Histology confirmed an adrenocorticotrophin (ACTH)-producing pituitary adenoma. We hypothesized that a NR3C1 mutation was present. Sequencing of the entire coding region of the gene produced normal results in both peripheral and tumor DNA.

CONCLUSION

We present the case of a pediatric patient with an ACTH-producing tumor but little evidence of CS. No mutations in the coding sequence of NR3C1 were detected. We conclude that low level somatic mosaicism for NR3C1 mutations or a mutation in another molecule participating in hGRalpha-signaling may account for this case.

Anterior pituitary adenomas: inherited syndromes, novel genes and molecular pathways

Pituitary adenomas are common tumors. Although rarely malignant, pituitary adenomas cause significant morbidity due to mass effects and/or hormonal hypo- and/or hyper-secretion. Molecular understanding of pituitary adenoma formation is essential for the development of medical therapies and the treatment of post-operative recurrences. In general, mutations in genes involved in genetic syndromes associated with pituitary tumors are not a common finding in sporadic lesions. By contrast, multiple endocrine neoplasia type 1 (MEN-1) and aryl hydrocarbon receptor-interacting protein (AIP) mutations may be more frequent among specific subgroups of patients, such as children and young adults, with growth hormone-producing adenomas. In this article, we present the most recent data on the molecular pathogenesis of pituitary adenomas and discuss some of the most recent findings from our laboratory. Guidelines for genetic screening and clinical counseling of patients with pituitary tumors are provided.