Targeted analysis of Ubiquitin-Specific Peptidase (USP8) in a population of Iranian people with Cushing's disease and a systematic review of the literature.

OBJECTIVE: Activating mutation in Ubiquitin-specific peptidase (USP8) is identified to enhance cell proliferation and adrenocorticotropic hormone (ACTH) secretion from corticotroph pituitary adenoma. We investigated the USP8 variant status in a population of Iranian people with functional corticotroph pituitary adenoma (FCPA). Moreover, a systematic review was conducted to thoroughly explore the role of USP8 variants and the related pathways in corticotroph adenomas, genotype-phenotype correlation in USP8-mutated individuals with FCPA, and the potential role of USP8 and epidermal growth factor receptor (EGFR) as targeted therapies in PFCAs. METHODS: Genetic analysis of 20 tissue samples from 19 patients with PFCAs was performed using Sanger sequencing. Moreover, a systematic literature review was performed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. PubMed, Scopus, web of Sciences, and Cochrane databases were searched. The last search was performed on 20 September 2023 for all databases. RESULTS: In our series, we found two somatic mutations including a 7-bp deletion variant: c.2151_2157delCTCCTCC, p. Ser718GlnfsTer3, and a missense variant: c.2159 C > G, p. Pro720Arg (rs672601311) in exon 14. The Systematic review indicated USP8 variant in 35% of corticotroph adenomas, with the highest frequency (25%) in 720 code regions, p. Pro720Arg. Data regarding the impact of USP8 mutational status on clinical characteristics and outcomes in FCPAs are inconsistent. Moreover, Pasireotide as well as inhibitors of EGFR such as Gefitinib and Lapatinib, as well as USP8 inhibitors including -ehtyloxyimino9H-indeno (1, 2-b) pyrazine-2, 3-dicarbonitrile, DUBs-IN-2, and RA-9 indicated promising results in treatment of corticotroph adenomas. CONCLUSION: Although the USP8-EGFR system has been identified as the main trigger and target of corticotroph tumorigenesis, more precise multicenter studies are required to yield more consistent information regarding the phenotype-genotype correlation and to develop effective targeted therapies.

Neuromedin B receptor as a potential therapeutic target for corticotroph adenomas.

PURPOSE: Cushing's disease (CD) results from autonomous adrenocorticotropic hormone (ACTH) secretion by corticotroph adenomas, leading to excessive cortisol production, ultimately affecting morbidity and mortality. Pasireotide is the only FDA approved tumor directed treatment for CD, but it is effective in only about 25% of patients, and is associated with a high rate of hyperglycemia. Neuromedin B (NMB), a member of the bombesin-like peptide family, regulates endocrine secretion and cell proliferation. Here, we assessed NMB and NMB receptor (NMBR) expression in human corticotroph adenomas and the effects of NMBR antagonist PD168368 on murine and human corticotroph tumors. METHODS: To investigate NMB and NMBR expression, real-time qPCR and immunostaining on human pathological specimens of corticotroph, non-functional and somatotroph adenomas were performed. The effects of PD168368 on hormone secretion and cell proliferation were studied in vitro, in vivo and in seven patient-derived corticotroph adenoma cells. NMB and NMBR were expressed in higher extent in human corticotroph adenomas compared with non-functional or somatotroph adenomas. RESULTS: In murine AtT-20 cells, PD168368 reduced proopiomelanocortin (Pomc) mRNA/protein expression and ACTH secretion as well as cell proliferation. In mice with tumor xenografts, tumor growth, ACTH and corticosterone were downregulated by PD168368. In patient-derived adenoma cells, PD168368 reduced POMC mRNA expression in four out of seven cases and ACTH secretion in two out of five cases. A PD168368-mediated cyclin E suppression was also identified in AtT-20 and patient-derived cells. CONCLUSION: NMBR antagonist represents a potential treatment for CD and its effect may be mediated by cyclin E suppression.

Genetic drivers of Cushing's disease: Frequency and associated phenotypes.

PURPOSE: Cushing's disease (CD) is often explained by a single somatic sequence change. Germline defects, however, often go unrecognized. We aimed to determine the frequency and associated phenotypes of genetic drivers of CD in a large cohort. METHODS: We studied 245 unrelated patients with CD (139 female, 56.7%), including 230 (93.9%) pediatric and 15 (6.1%) adult patients. Germline exome sequencing was performed in 184 patients; tumor exome sequencing was also done in 27 of them. A total of 43 germline samples and 92 tumor samples underwent Sanger sequencing of specific genes. Rare variants of uncertain significance, likely pathogenic (LP), or pathogenic variants in CD-associated genes, were identified. RESULTS: Germline variants (13 variants of uncertain significance, 8 LP, and 11 pathogenic) were found in 8 of 19 patients (42.1%) with positive family history and in 23 of 226 sporadic patients (10.2%). Somatic variants (1 LP and 7 pathogenic) were found in 20 of 119 tested individuals (16.8%); one of them had a coexistent germline defect. Altogether, variants of interest were identified at the germline level in 12.2% of patients, at the somatic level in 7.8%, and coexisting germline and somatic variants in 0.4%, accounting for one-fifth of the cohort. CONCLUSION: We report an estimate of the contribution of multiple germline and somatic genetic defects underlying CD in a single cohort.

Genetics of Cushing's disease: from the lab to clinical practice.

Cushing's disease is a rare, but devastating condition, caused by corticotroph tumors. It rarely manifests as syndrome and very few isolated cases present with germline mutations. Instead, the vast majority of corticotroph tumors are sporadic monoclonal neoplasms. At present, the major recurrent somatic driver mutations are found in the USP8 gene, which encodes for a deubiquitinase that rescues proteins regulating ACTH synthesis. Almost half of functional corticotroph tumors carry somatic USP8 mutations that associate with a distinct transcriptomic and clinical profile. Other genes mutated in a small fraction of corticotroph tumors include the deubiquitinase encoding gene USP48 and the glucocorticoid receptor expressing NR3C1. Recent reports on somatic TP53 and ATRX mutations in corticotroph macroadenomas and carcinomas indicate that within specific patient subpopulations they are not as rare as assumed.

Cushing's disease in children: unique features and update on genetics.

In this brief report, we review the unique characteristics of Cushing disease (CD) in children, as well as the most important new genetic discoveries associated with childhood CD. We often forget it, but CD refers to Cushing syndrome caused by pituitary corticotroph adenomas only. Thus, here we only refer to the new discoveries associated with pituitary tumors. There is indeed a wealth of new information on clinical features, outcomes, and genetic determinants of CD in children!

Responsiveness to DDAVP in Cushing's disease is associated with USP8 mutations through enhancing AVPR1B promoter activity.

PURPOSE: To clarify the characteristics of Cushing's disease (CD) patients who respond to the desmopressin (DDAVP) test and its underlying mechanisms. METHODS: Forty-seven patients with CD who underwent DDAVP testing were included. Patients were divided into two groups: DDAVP test (+) (adrenocorticotropic hormone [ACTH] levels increased by ≥ 1.5-fold during the DDAVP test) and DDAVP test (-) (ACTH levels increased by < 1.5-fold). AVP receptor expression levels in these tumors were quantified using quantitative RT-PCR and immunohistochemistry. AVP receptor promoter activity was analyzed using a dual-luciferase reporter assay system. RESULTS: Females (96.9%) and USP8 mutants (85.7%) were more prevalent in the DDAVP test (+) than in the DDAVP test (-). Indeed, the ACTH and cortisol responsiveness to DDAVP was greater in USP8 mutation positive tumors than that in USP8 wild type tumors (3.0-fold vs. 1.3-fold, 1.6-fold vs. 1.1-fold, respectively). Responsiveness to DDAVP was correlated with the expression levels of AVPR1B, but not with those of AVPR2. Comparably, Avpr1b promoter activity was enhanced by the overexpression of mutant USP8 compared to the wild type. CONCLUSIONS: We found that the responsiveness of ACTH to DDAVP in CD was greater in tumors with USP8 mutations. The present data suggest that USP8 mutations upregulate the AVPR1B promoter activity. Additionally, we showed that the DDAVP test can predict the presence of USP8 mutations.

Genetic Basis of ACTH-Secreting Adenomas.

Cushing's disease represents 60-70% of all cases of Cushing's syndrome, presenting with a constellation of clinical features associated with sustained hypercortisolism. Molecular alterations in corticotrope cells lead to the formation of ACTH-secreting adenomas, with subsequent excessive production of endogenous glucocorticoids. In the last few years, many authors have contributed to analyzing the etiopathogenesis and pathophysiology of corticotrope adenomas, which still need to be fully clarified. New molecular modifications such as somatic mutations of USP8 and other genes have been identified, and several case series and case reports have been published, highlighting new molecular alterations that need to be explored. To investigate the current knowledge of the genetics of ACTH-secreting adenomas, we performed a bibliographic search of the recent scientific literature to identify all pertinent articles. This review presents the most recent updates on somatic and germline mutations underlying Cushing's disease. The prognostic implications of these mutations, in terms of clinical outcomes and therapeutic scenarios, are still debated. Further research is needed to define the clinical features associated with the different genotypes and potential pharmacological targets.

Characterization of Adrenal miRNA-Based Dysregulations in Cushing's Syndrome.

MiRNAs are important epigenetic players with tissue- and disease-specific effects. In this study, our aim was to investigate the putative differential expression of miRNAs in adrenal tissues from different forms of Cushing's syndrome (CS). For this, miRNA-based next-generation sequencing was performed in adrenal tissues taken from patients with ACTH-independent cortisol-producing adrenocortical adenomas (CPA), from patients with ACTH-dependent pituitary Cushing's disease (CD) after bilateral adrenalectomy, and from control subjects. A confirmatory QPCR was also performed in adrenals from patients with other CS subtypes, such as primary bilateral macronodular hyperplasia and ectopic CS. Sequencing revealed significant differences in the miRNA profiles of CD and CPA. QPCR revealed the upregulated expression of miR-1247-5p in CPA and PBMAH (log2 fold change > 2.5, p < 0.05). MiR-379-5p was found to be upregulated in PBMAH and CD (log2 fold change > 1.8, p < 0.05). Analyses of miR-1247-5p and miR-379-5p expression in the adrenals of mice which had been exposed to short-term ACTH stimulation showed no influence on the adrenal miRNA expression profiles. For miRNA-specific target prediction, RNA-seq data from the adrenals of CPA, PBMAH, and control samples were analyzed with different bioinformatic platforms. The analyses revealed that both miR-1247-5p and miR-379-5p target specific genes in the WNT signaling pathway. In conclusion, this study identified distinct adrenal miRNAs as being associated with CS subtypes.

The genomic profiling and MAMLD1 expression in human and canines with Cushing's disease.

BACKGROUND: Cushing's disease (CD) is defined as hypercortisolemia caused by adrenocorticotropic hormone (ACTH)-secreting pituitary adenomas (corticotroph PA) that afflicts humans and dogs. In order to map common aberrant genomic features of CD between humans and dogs, we performed genomic sequencing and immunostaining on corticotroph PA. METHODS: For inclusion, humans and dog were diagnosed with CD. Whole exome sequencing (WES) was conducted on 6 human corticotroph PA. Transcriptome RNA-Seq was performed on 6 human and 7 dog corticotroph PA. Immunohistochemistry (IHC) was complete on 31 human corticotroph PA. Corticotroph PA were compared with normal tissue and between species analysis were also performed. RESULTS: Eight genes (MAMLD1, MNX1, RASEF, TBX19, BIRC5, TK1, GLDC, FAM131B) were significantly (P < 0.05) overexpressed across human and canine corticotroph PA. IHC revealed MAMLD1 to be positively (3+) expressed in the nucleus of ACTH-secreting tumor cells of human corticotroph PA (22/31, 70.9%), but absent in healthy human pituitary glands. CONCLUSIONS: In this small exploratory cohort, we provide the first preliminary insights into profiling the genomic characterizations of human and dog corticotroph PA with respect to MAMLD1 overexpression, a finding of potential direct impact to CD microadenoma diagnosis. Our study also offers a rationale for potential use of the canine model in development of precision therapeutics.

Updates in the Medical Treatment of Pituitary Adenomas.

Pituitary adenomas represent approximately 15% of brain tumors; incidence is significantly on the increase due to widespread use of magnetic resonance imaging. Surgery remains the first-line treatment for most tumors overall. The role of dopaminergic agonists (DAs) and somatostatin receptor ligands (SRLs) in the treatment of pituitary adenomas is quite well established for prolactinomas and growth hormone (GH) excess. However, over the last decade new multi-receptor binding SRLs are increasingly used for treatment of acromegaly and Cushing's disease. SRLs/DA chimeric compounds seem to have enhanced potency and efficacy when compared to that of individual SRLs or DA receptor agonists according to preclinical data. However, following negative results, more research is needed to determine if this interesting mechanism will translate into positive clinical effects for acromegaly patients. Furthermore, new agents that block adrenal steroidogenesis have been developed in phase III clinical trials for Cushing's disease and several new compounds working at the pituitary level and/or blocking the glucocorticoid receptor are also in development. Combination therapy of drugs with similar or different mechanisms (possibly synergistic) are also on the increase. A growing awareness regarding all mechanisms involved in both control of pituitary secretion and cellular proliferation might allow for sole medical treatment of pituitary adenomas, especially macroadenomas, rather than surgery and/or radiation therapy, in the future. Moreover, the underlying decision on how to treat patients with pituitary adenomas should be individualized on a case-by-case basis with not only a goal of tumor shrinkage and biochemical control, but also of improving patients' quality of life.

USP8 Mutations and Cell Cycle Regulation in Corticotroph Adenomas.

Corticotroph adenomas frequently harbor somatic USP8 mutations. These adenomas also commonly exhibit underexpression of P27, a cell cycle regulator. The present study aimed to determine the influence of USP8 mutations on clinical features of Cushing's disease and to elucidate the relationship between USP8 mutations and P27 underexpression in these tumors. Retrospective study with 32 patients with Cushing's disease was followed at the Ribeirao Preto Medical School University Hospital. We evaluated the patients' clinical data, the USP8 mutation status and the gene expression of cell cycle regulators P27/CDKN1B, CCNE1, CCND1, CDK2, CDK4, and CDK6 in tumor tissue in addition to the protein expression of P27/CDKN1B. We observed somatic mutations in the exon 14 of USP8 in 31.3% of the patients. Larger tumor size was observed in patients harboring USP8 mutations (p=0.04), with similar rates of remission, age of presentation, salivary cortisol at 23:00 h and after 1 mg dexamethasone, ACTH levels, and early postoperative plasma cortisol. We observed no differences regarding the gene or protein expression of the cell cycle regulators according to USP8 mutation status. In this Brazilian series, the observed frequency of USP8 somatic mutations was similar to that reported in European ancestry populations. Although it was reasonable that USP8 mutations could contribute to cell cycle dysregulation and P27 underexpression in corticotroph adenomas, our data did not confirm this hypothesis. It is possible that increased deubiquitinase activity observed in mutated USP8 might influence other pathways related to cell growth and proliferation.

TSP-1 is downregulated and inversely correlates with miR-449c expression in Cushing's disease.

The pathogenesis of Cushing's disease, which is caused by pituitary corticotroph adenoma, remains to be studied. Secreted angioinhibitory factor thrombospondin-1 (TSP-1) is an adhesive glycoprotein that mediates cell-to-cell and cell-to-matrix interactions and is associated with platelet aggregation, angiogenesis and tumorigenesis. We have found that the expression of TSP-1 is significantly lower in human pituitary corticotroph tumours compared with normal adenohypophysis. This study aims to elucidate the role of TSP-1 in regulating the tumour function of pituitary adenomas. Forced overexpression of TSP-1 in a murine AtT20 pituitary corticotroph tumour cell line decreased corticotroph precursor hormone proopiomelanocortin (POMC) transcription and adrenocorticotropic hormone (ACTH) secretion. Functional studies showed that TSP-1 overexpression in pituitary adenoma cells suppressed proliferation, migration and invasion. We have demonstrated that TSP-1 is a direct target of miR-449c. Further study showed that miR-449c activity enhanced tumorigenesis by directly inhibiting TSP-1 expression. Low expression of lncTHBS1, along with low expression of TSP-1, was associated with the high expression of miR-449c in Cushing's disease patients. Furthermore, RNA-immunoprecipitation associates miR-449c with lncTHBS1 suggesting that lncTHBS1 might be a negative regulator of miR-449c. Taken together, this study has demonstrated that lncTHBS1 might function as competing endogenous RNA for miR-449c, which could suppress the development of Cushing's disease.

Ubiquitin-specific protease 8 (USP8/UBPy): a prototypic multidomain deubiquitinating enzyme with pleiotropic functions.

Protein modification by ubiquitin is one of the most versatile posttranslational regulations and counteracted by almost 100 deubiquitinating enzymes (DUBs). USP8 was originally identified as a growth regulated ubiquitin-specific protease and is like many other DUBs characterized by its multidomain architecture. Besides the catalytic domain, specific protein-protein interaction modules were characterized which contribute to USP8 substrate recruitment, regulation and targeting to distinct protein complexes. Studies in mice and humans impressively showed the physiological relevance and non-redundant function of USP8 within the context of the whole organism. USP8 knockout (KO) mice exhibit early embryonic lethality while induced deletion in adult animals rapidly causes lethal liver failure. Furthermore, T-cell specific ablation disturbs T-cell development and function resulting in fatal autoimmune inflammatory bowel disease. In human patients, somatic mutations in USP8 were identified as the underlying cause of adrenocorticotropic hormone (ACTH) releasing pituitary adenomas causing Cushing's disease (CD). Here we provide an overview of the versatile molecular, cellular and pathology associated function and regulation of USP8 which appears to depend on specific protein binding partners, substrates and the cellular context.

Cushing's disease due to somatic USP8 mutations: a systematic review and meta-analysis.

PURPOSE: Cushing's disease (CD) is a severe illness generally caused by microcorticotropinomas (MICs) and in approximately 7-20% of patients by macrocorticotropinomas (MACs). USP8-mutations have been identified as a major genetic cause of CD (~ 50%). Few studies have reported the distribution between MICs-MACs related to USP8-mutations and their genotype-phenotype correlations. Therefore, we aimed to evaluate USP8-mutations in a cohort of MICs-MACs from a unique center and to perform a systematic review and meta-analysis. METHODS: DNA-tumor-tissues from 47 corticotropinomas (16 MICs and 31 MACs) were sequenced. Clinical-biochemical data, radiological imaging data and remission/recurrence rates were evaluated. In addition, we performed a meta-analysis of nine published series (n = 630). RESULTS: We identified four different USP8-mutations previously described, in 11 out of 47 (23.4%) corticotropinomas; 8 out of 11 were MACs. The urinary cortisol levels of our patients with corticotrophin USP8-mutated-alleles were lower than those of patients with wild-type (WT) alleles (p ≤ 0.017). The frequency of USP8-mutated-alleles among the series was approximately 30% with a higher prevalence in female-patients (p < 0.1 × 10-4). Among the 5 series, the remission rates were higher in patients with USP8-mutated-alleles than in those with the USP8-WT-alleles (p < 0.1 × 10-4). CONCLUSION: Our data, as well as the retrospective review of CD series associated with USP8-mutated alleles, show heterogeneous findings among the series. Several drawbacks included the lack of a systematic protocol to evaluate these patients before surgery and follow-up. Further prospective studies using a systematic protocol will provide more consistent information about the influence of the corticotropinomas with USP8-mutated alleles on the phenotype, responses to treatment and outcome of patients with CD.

Genetics of Cushing's disease.

Cushing's disease (CD) is a rare disabling condition caused by Adrenocorticotropic hormone (ACTH)-secreting adenomas of the pituitary. The majority of corticotropic adenomas are monoclonal and occur sporadically. Only rarely does CD arise in the context of genetic familial syndromes. Targeted sequencing of oncogenes and tumour suppressor genes commonly mutated in other tumours did not identify recurrent mutations. In contrast, next generation sequencing allowed us recently to clarify the genetic basis of CD: we identified somatic driver mutations in the ubiquitin-specific protease 8 (USP8) gene in a significant portion of corticotropinomas. These mutations represent a novel and unique mechanism leading to ACTH excess. Inhibition of USP8 or its downstream signalling pathways could represent a new therapeutic approach for the management of CD. In this review, we will focus on this new evidence and its implication for clinical care of affected patients.

Children with MEN1 gene mutations may present first (and at a young age) with Cushing disease.

OBJECTIVE: Cushing disease (CD) is a rare entity caused by ACTH-secreting pituitary tumours, leading to prolonged hypercortisolism. Most cases are sporadic but can rarely occur in the context of familial predisposition, due to germline mutations in genes such as MEN1, leading to multiple endocrine neoplasia type 1, MEN1. We have reported previously that CD can be the first and only presenting manifestation of MEN1. In this report, we describe a cohort of paediatric patients who presented with CD as the first manifestation of MEN1. MATERIALS AND METHODS: A retrospective analysis of paediatric patients admitted to the National Institutes of Health (NIH) Clinical Center for evaluation of hypercortisolism, between 1997 and 2017. MEN1 was diagnosed on a clinical, familial and/or genetic basis. RESULTS: Of a total of 238 children with CD, six patients were subsequently diagnosed with MEN1, three males and three females with a mean age at diagnosis of CD at 13.4 ± 2.9 years. Five of the six patients had familial MEN1 and one patient was a sporadic case. Additional manifestations of MEN1 included primary hyperparathyroidism in three patients and hyperprolactinemia in two patients. DISCUSSION: This report describes a paediatric patient population with MEN1 in whom CD was the initial manifestation, confirming a previous observation that paediatric patients with MEN1 may present first with an ACTH-producing adenoma. Therefore, germline MEN1 mutations should be sought in paediatric CD and tested for when there is a suggestive family history and/or other manifestations.

Effects of endogenous hypercortisolism on bone mRNA and microRNA expression in humans.

Hypercortisolism in humans suppresses osteoblastogenesis and osteoblast function through the upregulation of Wnt-signaling antagonists (sclerostin, Dkk1) and changes in microRNAs levels (miR-125b-5p, miR-218-5p, miR-34a-5p, miR-188-3p, miR-199a-5p) which are associated with mesenchymal stem-cell commitment to adipocytes or cartilage cells over the osteoblasts. INTRODUCTION: The purpose of this study was to evaluate the responses of bone to chronic glucocorticoid (GC) excess by measuring the levels of selected mRNA and microRNA (miR) in bone samples of patients with Cushing's disease (CD). METHODS: Bone samples were obtained during transsphenoidal adenomectomy from the sphenoid bone (sella turcica) from 16 patients with clinically and biochemically evident CD and 10 patients with clinically non-functioning pituitary adenomas (NFPA) matched by sex, age, and body mass index. Quantitative polymerase chain reactions (qPCR) were used to examine the expression of genes (mRNA and miRs) known to be involved in bone remodeling regulation based on studies in animals and cell culture. RESULTS: Hypercortisolism was associated with the downregulation of genes involved in osteoblast function and maturation (ACP5, ALPL, BGLAP, COL1A1, COL1A2, BMP2, RUNX2, TWIST1). An excess of GC caused increased expression of Wnt-signaling antagonists (Dkk1, SOST) and changes in the levels of miRs that are known to suppress osteoblastogenesis (miR-125b-5p, miR-218-5p, miR-34a-5p, miR-188-3p, miR-199a-5p) p < 0.05, q < 0.1. Interestingly, compensatory mechanisms were found in long-term hypercortisolism: upregulation of Wnt10b, LRP5, and LRP6; downregulation of SFRP4; changes in miRs involved in osteoblastogenesis (miR-210-5p, miR-135a-5p, miR-211, miR-23a-3p, miR-204-5p); and downregulation of genes associated with osteoclastogenesis. None of these changes prevented the suppression of bone formation. CONCLUSIONS: An excess of endogenous GC in humans suppresses bone formation through the upregulation of Wnt-signaling antagonists and dysregulation of miRs involved in mesenchymal stem-cell commitment. Both Wnt-signaling antagonists and miRs seem to be promising targets for further research in therapeutic intervention in glucocorticoid-induced osteoporosis.

PATHOGENESIS OF CUSHING DISEASE: AN UPDATE ON THE GENETICS OF CORTICOTROPINOMAS.

OBJECTIVE: Cushing disease is a rare severe condition caused by pituitary tumors that secrete adrenocorticotropic hormone (ACTH), leading to excessive endogenous glucocorticoid production. Tumors causing Cushing disease, also called corticotropinomas, are typically monoclonal neoplasms that mainly occur sporadically. METHODS: Literature review. RESULTS: Cushing disease is very rarely encountered in genetic familial syndromes. Oncogenes and tumor suppressor genes commonly associated with other tumor types are only rarely mutated in this tumor type. The advent of next-generation sequencing led to the identification of a single mutational hotspot in the ubiquitin-specific protease 8 ( USP8) gene in almost half of Cushing disease tumors. CONCLUSION: The new discoveries showcase a novel mechanism responsible for corticotroph tumorigenesis and ACTH hypersecretion and highlight USP8 and its downstream signaling pathways as potential promising pharmacologic targets for the management of Cushing disease. ABBREVIATIONS: ACTH = adrenocorticotropic hormone; BRG1 = Brahma-related gene 1; CABLES1 = CDK5 and ABL1 enzyme substrate 1; CD = Cushing disease; CNC = Carney complex; DICER1 = cytoplasmic endoribonuclease III; EGFR = epidermal growth factor receptor; GR = glucocorticoid receptor; IL = interleukin; MEN = multiple endocrine neoplasia; miRNA = microRNA; POMC = proopiomelanocortin; SSTR = somatostatin receptor; USP8 = ubiquitin-specific protease 8.

Frequency of familial pituitary adenoma syndromes among patients with functioning pituitary adenomas in a reference outpatient clinic.

INTRODUCTION: Pituitary adenomas (PA) occur mainly as sporadic disease, but familial syndromes are found in approximately 5% of cases. Identification of these syndromes is important in order to diagnose individuals at risk at an earlier stage. AIMS: To evaluate the frequency of familial PA in a reference outpatient clinic devoted to PA treatment and to identify family members suspected to have pituitary disease. METHODS: Patients with PA were interviewed with respect to the presence of family members with diagnosis of PA or with signs or symptoms suggestive of them. The family members who had a clinical picture suggestive of pituitary disease were further evaluated in an attempt to identify new PA cases. In families with familial disease, the AIP gene was sequenced. RESULTS: 262 patients were evaluated and familial syndrome was found in 13 (5%). Ten (3.8%) patients had familial isolated PA (FIPA) and three (1.2%) had multiple endocrine neoplasia type 1. After evaluation of family members' symptomatology, 110 were considered suspected of having pituitary disease, but only 24 participated in the study. Of these 24, 1 was diagnosed with a corticotropinoma. AIP mutations were found in 20% of FIPA families. CONCLUSION: We found a frequency of familial PA similar to that previously described, as well as a similar frequency of AIP mutations among FIPA families. An active search of the affected family members was able to identify one case of Cushing´s disease. Patients should be aware of pituitary disease's clinical picture to identify possibly affected family members.

Genetics of Cushing's disease: an update.

INTRODUCTION: Cushing's disease (CD) results from uncontrolled hypercortisolism induced by ACTH-secreting corticotroph adenomas; accordingly, patients diagnosed with CD usually present several comorbidities and an increased risk of mortality. Hypothesis-driven screenings have led to identification of rare alterations in a low number of patients, although the genetic basis underlying CD has remained unclear until recently. Using whole-exome sequencing, recurrent mutations have been reported in the gene coding for the ubiquitin-specific protease 8 (USP8), a protein with deubiquitinase (DUB) activity that modulates the lysosomal turnover of the EGF receptor (EGFR) and other membrane proteins. METHODS: In this review, we summarize the recent genetic findings and discuss the clinical and pathological implications of USP8 deregulation in corticotroph adenomas. CONCLUSIONS: Mutations in USP8 have been identified in 35-62 % of functional sporadic corticotroph adenomas causing Cushing's disease, but not in any other type of pituitary tumor. These mutations are found mostly in adult female patients and lead to an aberrant DUB activation by impairing the regulation of USP8 by members of the 14-3-3 family of proteins. The consequence of this hyperactivation is a longer retention of EGFR at the plasma membrane which promotes an enhanced production of ACTH.