/pdf/journal-of-clinical-endocrinology-and-metabolism-1w9si59np1.pdf

Journal of clinical endocrinology and metabolism

Pituitary adenomas are one of the most frequent intracranial tumors and occur with a prevalence of approximately 1:1000 in the developed world. Pituitary adenomas have a serious disease burden, and their management involves neurosurgery, biological therapies, and radiotherapy. Early diagnosis of pituitary tumors while they are smaller may help increase cure rates. Few genetic predictors of pituitary adenoma development exist. Recent years have seen two separate, complimentary advances in inherited pituitary tumor research. The clinical condition of familial isolated pituitary adenomas (FIPA) has been described, which encompasses the familial occurrence of isolated pituitary adenomas outside of the setting of syndromic conditions like multiple endocrine neoplasia type 1 and Carney complex. FIPA families comprise approximately 2% of pituitary adenomas and represent a clinical entity with homogeneous or heterogeneous pituitary adenoma types occurring within the same kindred. The aryl hydrocarbon receptor interacting protein (AIP) gene has been identified as causing a pituitary adenoma predisposition of variable penetrance that accounts for 20% of FIPA families. Germline AIP mutations have been shown to associate with the occurrence of large pituitary adenomas that occur at a young age, predominantly in children/adolescents and young adults. AIP mutations are usually associated with somatotropinomas, but prolactinomas, nonfunctioning pituitary adenomas, Cushing disease, and other infrequent clinical adenoma types can also occur. Gigantism is a particular feature of AIP mutations and occurs in more than one third of affected somatotropinoma patients. Study of pituitary adenoma patients with AIP mutations has demonstrated that these cases raise clinical challenges to successful treatment. Extensive research on the biology of AIP and new advances in mouse Aip knockout models demonstrate multiple pathways by which AIP may contribute to tumorigenesis. This review assesses the current clinical and therapeutic characteristics of more than 200 FIPA families and addresses research findings among AIP mutation-bearing patients in different populations with pituitary adenomas.

Familial Isolated Pituitary Adenomas (FIPA) and the Pituitary Adenoma Predisposition due to Mutations in the Aryl Hydrocarbon Receptor Interacting Protein (AIP) Gene

Acromegaly is a rare and underdiagnosed disorder caused, in more than 95% of cases, by a growth hormone (GH)-secreting pituitary adenoma. The GH hypersecretion leads to overproduction of insulin-like growth factor 1 (IGF-1) which results in a multisystem disease characterized by somatic overgrowth, multiple comorbidities, physical disfigurement, and increased mortality. This article aims to review the clinical features of acromegaly at diagnosis. Acromegaly affects both males and females equally and the average age at diagnosis ranges from 40 to 50 years (up to 5% of cases < the age 20). Due to insidious onset and slow progression, acromegaly is often diagnosed five to more than ten years after its onset. The typical coarsening of facial features include furrowing of fronthead, pronounced brow protrusion, enlargement of the nose and the ears, thickening of the lips, skin wrinkles and nasolabial folds, as well as mandibular prognathism that leads to dental malocclusion and increased interdental spacing. Excessive growth of hands and feet (predominantly due to soft tissue swelling) is present in the vast majority of acromegalic patients. Gigantism accounts for up to 5% of cases and occurs when the excess of GH becomes manifest in the young, before the epiphyseal fusion. The disease also has rheumatologic, cardiovascular, respiratory, neoplastic, neurological, and metabolic manifestations which negatively impact its prognosis and patients quality of life. Less than 15% of acromegalic patients actively seek medical attention for change in appearance or enlargement of the extremities. The presentation of acromegaly is more often related to its systemic comorbidities or to local tumor effects.

Acromegaly: clinical features at diagnosis

Multiple endocrine neoplasia (MEN) refers to a group of autosomal dominant disorders with generally high penetrance that lead to the development of a wide spectrum of endocrine and non-endocrine manifestations. The most frequent among these conditions is MEN type 1 (MEN1), which is caused by germline heterozygous loss-of-function mutations in the tumor suppressor gene MEN1 MEN1 is characterized by primary hyperparathyroidism (PHPT) and functional or nonfunctional pancreatic neuroendocrine tumors and pituitary adenomas. Approximately 10% of patients with familial or sporadic MEN1-like phenotype do not have MEN1 mutations or deletions. A novel MEN syndrome was discovered, initially in rats (MENX), and later in humans (MEN4), which is caused by germline mutations in the putative tumor suppressor CDKN1B The most common phenotype of the 19 established cases of MEN4 that have been described to date is PHPT followed by pituitary adenomas. Recently, somatic or germline mutations in CDKN1B were also identified in patients with sporadic PHPT, small intestinal neuroendocrine tumors, lymphoma and breast cancer, demonstrating a novel role for CDKN1B as a tumor susceptibility gene for other neoplasms. In this review, we report on the genetic characterization and clinical features of MEN4.

/pdf/men4-and-cdkn1b-mutations-the-latest-of-the-men-syndromes-3p025k9pqj.pdf

MEN4 and CDKN1B mutations: The latest of the MEN syndromes

Recently, a number of novel genetic alterations have been identified that predispose individuals to pituitary adenomas. Clinically relevant pituitary adenomas are relatively common, present in 0.1% of the general population. They are mostly benign monoclonal neoplasms that arise from any of the five hormone-secreting cell types of the anterior lobe of the pituitary gland, and cause disease due to hormonal alterations and local space-occupying effects. The pathomechanism of pituitary adenomas includes alterations in cell-cycle regulation and growth factor signaling, which are mostly due to epigenetic changes; somatic and especially germline mutations occur more rarely. A significant proportion of growth hormone- and adrenocorticotrophin-secreting adenomas have activating somatic mutations in the GNAS and USP8 genes, respectively. Rarely, germline mutations predispose to pituitary tumorigenesis, often in a familial setting. Classical tumor predisposition syndromes include multiple endocrine neoplasia type 1 (MEN1) and type 4 (MEN4) syndromes, Carney complex, and McCune-Albright syndrome. Pituitary tumors have also been described in association with neurofibromatosis type 1, DICER1 syndrome, and SDHx mutations. Pituitary adenomas with no other associated tumors have been described as familial isolated pituitary adenomas. Patients with AIP or GPR101 mutations often present with pituitary gigantism either in a familial or simplex setting. GNAS and GPR101 mutations that arise in early embryonic age can lead to somatic mosaicism involving the pituitary gland and resulting in growth hormone excess. Senescence has been suggested as the key mechanism protecting pituitary adenomas turning malignant in the overwhelming majority of cases. Here we briefly summarize the genetic background of pituitary adenomas, with an emphasis on the recent developments in this field. Clin Cancer Res; 22(20); 5030-42. ©2016 AACR SEE ALL ARTICLES IN THIS CCR FOCUS SECTION, "ENDOCRINE CANCERS REVISING PARADIGMS".

/pdf/novel-genetic-causes-of-pituitary-adenomas-3w0qify5az.pdf

Novel Genetic Causes of Pituitary Adenomas.

Somatic mosaicism has been implicated as a causative mechanism in a number of genetic and genomic disorders. X-linked acrogigantism (XLAG) syndrome is a recently characterized genomic form of pediatric gigantism due to aggressive pituitary tumors that is caused by submicroscopic chromosome Xq26.3 duplications that include GPR101 We studied XLAG syndrome patients (n= 18) to determine if somatic mosaicism contributed to the genomic pathophysiology. Eighteen subjects with XLAG syndrome caused by Xq26.3 duplications were identified using high-definition array comparative genomic hybridization (HD-aCGH). We noted that males with XLAG had a decreased log2ratio (LR) compared with expected values, suggesting potential mosaicism, whereas females showed no such decrease. Compared with familial male XLAG cases, sporadic males had more marked evidence for mosaicism, with levels of Xq26.3 duplication between 16.1 and 53.8%. These characteristics were replicated using a novel, personalized breakpoint junction-specific quantification droplet digital polymerase chain reaction (ddPCR) technique. Using a separate ddPCR technique, we studied the feasibility of identifying XLAG syndrome cases in a distinct patient population of 64 unrelated subjects with acromegaly/gigantism, and identified one female gigantism patient who had had increased copy number variation (CNV) threshold for GPR101 that was subsequently diagnosed as having XLAG syndrome on HD-aCGH. Employing a combination of HD-aCGH and novel ddPCR approaches, we have demonstrated, for the first time, that XLAG syndrome can be caused by variable degrees of somatic mosaicism for duplications at chromosome Xq26.3. Somatic mosaicism was shown to occur in sporadic males but not in females with XLAG syndrome, although the clinical characteristics of the disease were similarly severe in both sexes.

/pdf/somatic-mosaicism-underlies-x-linked-acrogigantism-syndrome-3vxws5exee.pdf

Somatic mosaicism underlies X-linked acrogigantism syndrome in sporadic male subjects

Familial isolated pituitary adenoma (FIPA) occurs in families and is unrelated to multiple endocrine neoplasia type 1 and Carney complex. Mutations in AIP account only for 15-25% of FIPA families. CDKN1B mutations cause MEN4 in which affected patients can suffer from pituitary adenomas. With this study, we wanted to assess whether mutations in CDKN1B occur among a large cohort of AIP mutation-negative FIPA kindreds. Eighty-eight AIP mutation-negative FIPA families were studied and 124 affected subjects underwent sequencing of CDKN1B. Functional analysis of putative CDKN1B mutations was performed using in silico and in vitro approaches. Germline CDKN1B analysis revealed two nucleotide changes: c.286A>C (p.K96Q) and c.356T>C (p.I119T). In vitro, the K96Q change decreased p27 affinity for Grb2 but did not segregate with pituitary adenoma in the FIPA kindred. The I119T substitution occurred in a female patient with acromegaly. p27(I119T) shows an abnormal migration pattern by SDS-PAGE. Three variants (p.S56T, p.T142T, and c.605+36C>T) are likely nonpathogenic because In vitro effects were not seen. In conclusion, two patients had germline sequence changes in CDKN1B, which led to functional alterations in the encoded p27 proteins in vitro. Such rare CDKN1B variants may contribute to the development of pituitary adenomas, but their low incidence and lack of clear segregation with affected patients make CDKN1B sequencing unlikely to be of use in routine genetic investigation of FIPA kindreds. However, further characterization of the role of CDKN1B in pituitary tumorigenesis in these and other cases could help clarify the clinicopathological profile of MEN4.

/pdf/cyclin-dependent-kinase-inhibitor-1b-cdkn1b-gene-variants-in-4k50td3vjp.pdf

Cyclin-dependent kinase inhibitor 1B (CDKN1B) gene variants in AIP mutation-negative familial isolated pituitary adenoma kindreds.

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Somatic mosaicism underlies X-linked acrogigantism syndrome in sporadic male subjects

Cyclin-dependent kinase inhibitor 1B (CDKN1B) gene variants in AIP mutation-negative familial isolated pituitary adenoma kindreds.