The Gene of the Ubiquitin-Specific Protease 8 Is Frequently Mutated in Adenomas Causing Cushing's Disease

Outcome of non-functioning ACTH pituitary tumors: silent does not mean indolent

INTRODUCTION

Silent corticotroph tumors (siACTH) represent a rare entity of pituitary tumors (PT), usually more aggressive than other PT. Few predictor factors of recurrence in the post-operative period have been proposed until now. This study aimed (1) to evaluate the clinical outcome of siACTH after surgery according to a five-tiered clinicopathological classification (2) to compare siACTH characteristics to ACTH-secreting macroadenomas (macroCD), and silent gonadotropinomas (siLH/FSH).

PATIENTS AND METHODS

Between 2008 and 2022, 29 siACTH out of 865 PT cases operated in one tertiary center were included. Clinical, paraclinical, histological, and surgical data were collected and compared to 25 macroCD and 143 siLH/FSH cases, respectively. The tumor grading was established according to both invasion (no = 1; yes = 2) and proliferation (no = a; yes = b). Progression-free survival was estimated using Kaplan-Meier method and log-rank test.

RESULTS

We identified 15 (51.7%) grade 1a, 11 (37.9%) grade 2a and 3 (10.3%) grade 2b siACTH with a trend for a 7-fold-time higher risk of progression/recurrence in grade 2b as compared to 1a (p = 0.06). The repartition of tumor grades was similar between the three subgroups, however a 5.7-fold-higher risk of progression was observed in grade 1a siACTH than in grade 1a siLH/FSH (p = 0.02). Compared to siLH/FSH, higher ACTH levels may help to preoperatively identify siACTH.

CONCLUSION

The five-tiered clinicopathological classification contribute to predict the risk of recurrence of operated siACTH tumors. Noteworthy, non-invasive and non-proliferative siACTH exhibit a less favorable outcomes than their siLH/FSH counterparts, which should prompt for a personalized follow up.

An Update on the Genetic Drivers of Corticotroph Tumorigenesis

The genetic landscape of corticotroph tumours of the pituitary gland has dramatically changed over the last 10 years. Somatic changes in the USP8 gene account for the most common genetic defect in corticotrophinomas, especially in females, while variants in TP53 or ATRX are associated with a subset of aggressive tumours. Germline defects have also been identified in patients with Cushing's disease: some are well-established (MEN1, CDKN1B, DICER1), while others are rare and could represent coincidences. In this review, we summarise the current knowledge on the genetic drivers of corticotroph tumorigenesis, their molecular consequences, and their impact on the clinical presentation and prognosis.

A long-term prognosis study of human USP8-mutated ACTH-secreting pituitary neuroendocrine tumours

OBJECTIVE

Somatic variants in the ubiquitin-specific protease 8 (USP8) gene are the most common genetic cause of Cushing disease. We aimed to explore the relationship between clinical outcomes and USP8 status in a single centre.

DESIGN, PATIENTS AND MEASUREMENTS

We investigated the USP8 status in 48 patients with pituitary corticotroph tumours. A median of 62 months of follow-up was conducted after surgery from November 2013 to January 2015. The clinical, biochemical and imaging features were collected and analysed.

RESULTS

Seven USP8 variants (p.Ser718Pro, p.Ser719del, p.Pro720Arg, p.Pro720Gln, p.Ser718del, p.Ser718Phe, p.Lys713Arg) were identified in 24 patients (50%). USP8 variants showed a female predominance (100% vs. 75% in wild type [WT], p = .022). Patients with p.Ser719del showed an older age at surgery compared to patients with the p.Pro720Arg variant (47- vs. 24-year-olds, p = .033). Patients with p.Pro720Arg showed a higher rate of macroadenoma compared to patients harbouring the p.Ser718Pro variant (60% vs. 0%, p = .037). No significant differences were observed in serum and urinary cortisol and adrenocorticotropin hormone (ACTH) levels. Immediate surgical remission (79% vs. 75%) and long-term hormone remission (79% vs. 67%) were not significantly different between the two groups. The recurrence rate was 21% (4/19) in patients harbouring USP8 variants and 13% (2/16) in WT patients. Recurrence-free survival presented a tendency to be shorter in USP8-mutated individuals (76.7 vs. 109.2 months, p = .068).

CONCLUSIONS

Somatic USP8 variants accounted for 50% of the genetic causes in this cohort with a significant female frequency. A long-term follow-up revealed a tendency toward shorter recurrence-free survival in USP8-mutant patients.

Consensus statement by the French Society of Endocrinology (SFE) and French Society of Pediatric Endocrinology & Diabetology (SFEDP) for the diagnosis of Cushing's syndrome: Genetics of Cushing's syndrome

Cushing's syndrome is due to overproduction of cortisol, leading to abnormal and prolonged exposure to cortisol. The most common etiology is Cushing disease, while adrenal causes are rarer. Knowledge of the genetics of Cushing's syndrome, and particularly the adrenal causes, has improved considerably over the last 10 years, thanks in particular to technical advances in high-throughput sequencing. The present study, by a group of experts from the French Society of Endocrinology and the French Society of Pediatric Endocrinology and Diabetology, reviewed the literature on germline genetic alterations leading to a predisposition to develop Cushing's syndrome. The review led to a consensus statement on genetic screening for Cushing disease and adrenal Cushing's syndrome.

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.

Somatic USP8 alteration affects the immune landscape of corticotroph pituitary adenomas- a pilot study

INTRODUCTION

Somatic mutations in ubiquitin-specific protease-8 (USP8), encoding a deubiquinating protein, are found in approximately 30% of corticotroph-derived pituitary adenomas (CPAs). Stratifin, a protein encoded by SFN, inhibits USP8 catalytic activity. USP8 has immunomodulating properties that have been demonstrated in non-tumoral diseases.

METHODS

We assessed the influence of USP8 on the immune landscape of CPA and validated this effect and its dependency on stratifin in large cohorts of non-pituitary tumors. We analyzed data of CPA samples (n = 20) and additional non-pituitary tumors from the TCGA database, using transcriptome signature-recognition algorithms. Immune tumor microenvironment (iTME) was compared both by USP8 and SFN expression levels (n = 843) and by USP8 mutation status and SFN expression (n = 12,389).

RESULTS

CPA with activating USP8 mutations was associated with "cold" iTME compared with wild-type USP8 CPA, as reflected by lower fractions of immune cells, including B cells, CD4, regulatory and gamma/delta T cells, natural killer cells, M0 and M1 macrophages, dendritic cells, and eosinophils (p < 0.05 for all comparisons). Pathways altered by the presence of USP8 mutation, based on the most differentially expressed genes (3061 genes), included microglia pathogen phagocytosis and multiple toll-like receptor signaling pathways (p < 0.0001). In a validation analysis based on large cohorts of non-pituitary tumors, high expression of USP8 was associated with a suppressed iTME effect that was augmented by a low SFN expression.

CONCLUSIONS

Our data demonstrate for the first time, to our knowledge, a distinct immune landscape of tumors based on USP8 status and expression and the dependency of this immunological effect on SFN expression.

Fusion of Platelet Derived Growth Factor Receptor Alpha (PDGFRA) With Ubiquitin Specific Peptidase 8 (USP8) in a Calcified Chondroid Mesenchymal Neoplasm Harboring t(4;15)(q12;q21) as a Sole Aberration

BACKGROUND/AIM

The term "calcified chondroid mesenchymal neoplasm" was introduced in 2021 to describe a group of tumors characterized by various morphological features, including the formation of cartilage or chondroid matrix. These tumors frequently carry chimeric genes where the 5'-end partner gene is fibronectin 1 and the 3'-end partner gene codes for receptor tyrosine kinase. Our study explores fusion of the genes platelet-derived growth factor receptor alpha (PDGFRA) and ubiquitin-specific peptidase 8 (USP8) in calcified chondroid mesenchymal neoplasm.

CASE REPORT

Genetic investigations were conducted on a tumor located in the leg of a 71-year-old woman. G-banding analysis of short-term cultured tumor cells revealed the karyotype 46,XX,t(4;15)(q12;q21)[6]/46,XX[4]. RNA sequencing detected in-frame PDGFRA::USP8 and USP8::PDGFRA chimeric transcripts, which were validated by RT-PCR/Sanger sequencing. The PDGFRA::USP8 chimeric protein is predicted to have cell membrane location and functions as a chimeric ubiquitinyl hydrolase. The USP8::PDGFRA protein was predicted to be nuclear and function as a positive regulator of cellular metabolic process.

CONCLUSION

We report, for the first time, a calcified chondroid mesenchymal neoplasm carrying a balanced t(4;15)(q12;q21) chromosomal translocation, resulting in the generation of both PDGFRA::USP8 and USP8::PDGFRA chimeras. The PDGFRA::USP8 protein is located on the cell membrane and functions as a chimeric ubiquitinyl hydrolase, activated by PDGFs. Conversely, USP8::PDGFRA is a nuclear protein regulating metabolic processes.

Consensus guideline for the diagnosis and management of pituitary adenomas in childhood and adolescence: Part 1, general recommendations

Tumours of the anterior part of the pituitary gland represent just 1% of all childhood (aged <15 years) intracranial neoplasms, yet they can confer high morbidity and little evidence and guidance is in place for their management. Between 2014 and 2022, a multidisciplinary expert group systematically developed the first comprehensive clinical practice consensus guideline for children and young people under the age 19 years (hereafter referred to as CYP) presenting with a suspected pituitary adenoma to inform specialist care and improve health outcomes. Through robust literature searches and a Delphi consensus exercise with an international Delphi consensus panel of experts, the available scientific evidence and expert opinions were consolidated into 74 recommendations. Part 1 of this consensus guideline includes 17 pragmatic management recommendations related to clinical care, neuroimaging, visual assessment, histopathology, genetics, pituitary surgery and radiotherapy. While in many aspects the care for CYP is similar to that of adults, key differences exist, particularly in aetiology and presentation. CYP with suspected pituitary adenomas require careful clinical examination, appropriate hormonal work-up, dedicated pituitary imaging and visual assessment. Consideration should be given to the potential for syndromic disease and genetic assessment. Multidisciplinary discussion at both the local and national levels can be key for management. Surgery should be performed in specialist centres. The collection of outcome data on novel modalities of medical treatment, surgical intervention and radiotherapy is essential for optimal future treatment.

A proposed clinical classification for pituitary neoplasms to guide therapy and prognosis

No comprehensive classification system that guides prognosis and therapy of pituitary adenomas exists. The 2022 WHO histopathology-based classification system can only be applied to lesions that are resected, which represent few clinically significant pituitary adenomas. Many factors independent of histopathology provide mechanistic insight into causation and influence prognosis and treatment of pituitary adenomas. We propose a new approach to guide prognosis and therapy of pituitary adenomas by integrating clinical, genetic, biochemical, radiological, pathological, and molecular information for all adenomas arising from anterior pituitary cell lineages. The system uses an evidence-based scoring of risk factors to yield a cumulative score that reflects disease severity and can be used at the bedside to guide pituitary adenoma management. Once validated in prospective studies, this simple manageable classification system could provide a standardised platform for assessing disease severity, prognosis, and effects of therapy on pituitary adenomas.

Relevance of mutations in protein deubiquitinases genes and TP53 in corticotroph pituitary tumors

Introduction

Corticotroph pituitary neuroendocrine tumors (PitNETs) develop from ACTH-producing cells. They commonly cause Cushing's disease (CD), however, some remain clinically silent. Recurrent USP8, USP48, BRAF and TP53 mutations occur in corticotroph PitNETs. The aim of our study was to determine frequency and relevance of these mutations in a possibly large series of corticotroph PitNETs.

Methods

Study included 147 patients (100 CD and 47 silent tumors) that were screened for hot-spot mutations in USP8, USP48 and BRAF with Sanger sequencing, while 128 of these patients were screened for TP53 mutations with next generation sequencing and immunohistochemistry.

Results

USP8 mutations were found in 41% CD and 8,5% silent tumors, while USP48 mutations were found in 6% CD patients only. Both were more prevalent in women. They were related to higher rate of biochemical remission, non-invasive tumor growth, its smaller size and densely granulated histology, suggesting that these mutation may be favorable clinical features. Multivariate survival analyses did not confirm possible prognostic value of mutation in protein deubiquitinases. No BRAF mutations were found. Four TP53 mutations were identified (2 in CD, 2 in silent tumors) in tumors with size >10mm including 3 invasive ones. They were found in Crooke's cell and sparsely granulated tumors. Tumors with missense TP53 mutations had higher TP53 immunoreactivity score than wild-type tumors. Tumor with frameshift TP53 variant had low protein expression. TP53 mutation was a poor prognostic factor in CD according to uni- and multivariate survival analyses in spite of low mutations frequency.

Conclusions

We confirmed high prevalence of USP8 mutations and low incidence of USP48 and TP53 mutations. Changes in protein deubiquitinases genes appear to be favorable prognostic factors in CD. TP53 mutations are rare, occur in both functioning and silent tumors and are related to poor clinical outcome in CD.

Current and Emerging Pharmacological Therapies for Cushing's Disease

Cushing's Disease (CD), hypercortisolism due to pituitary ACTH secreting neuroendocrine neoplasm, is associated with increased morbidity and, if untreated, mortality in about half of the affected individuals. Consequently, the timely initiation of effective treatment is mandatory. Neurosurgery is the first line and the only potentially curative treatment; however, 30% of patients will have persistent disease post-surgery. Furthermore, a small percentage of those initially controlled will develop hypercortisolism during long-term follow- up. Therefore, patients with persistent or recurrent disease, as well as those considered non-eligible for surgery, will need a second-line therapeutic approach, i.e., pharmacotherapy. Radiation therapy is reserved as a third-line therapeutic option due to its slower onset of action and its unfavorable profile regarding complications. During the past few years, the understanding of molecular mechanisms implicated in the physiology of the hypothalamus-pituitary-adrenal axis has evolved, and new therapeutic targets for CD have emerged. In the present review, currently available treatments, compounds currently tested in ongoing clinical trials, and interesting, potentially new targets emerging from unraveling molecular mechanisms involved in the pathophysiology of Cushing's disease are discussed.

The clinicopathological features and prognosis of silent corticotroph tumors: an updated systematic review and meta-analysis

INTRODUCTION

Data on silent corticotroph tumor (SCT) are still heterogeneous and controversial. In this study, we aimed to compare the demographic, clinicopathological manifestations, postoperative complications, and patient outcomes of SCTs with other non-functioning pituitary neuroendocrine tumor (NFT) and functioning corticotroph tumor (FCT) or so-called Cushing disease adenoma.

METHODS

We searched PubMed and Web of Science for data of interest. Odds ratio (OR), mean difference (MD), hazard ratio (HR), and their 95% confidence intervals (CI) were pooled using the random-effect model.

RESULTS

Twenty-nine studies with 985 SCTs were included in meta-analyses. In comparison to other NFTs, SCTs were more commonly associated with female gender, younger age, cavernous sinus invasion, apoplexy, and radiotherapy administration. Postoperatively, SCT patients were more likely to experience hypocortisolism, new-onset visual disturbances, and a higher risk for tumor progression than other NFTs. We did not find any significant differences between SCT type I and type II. Compared to FCTs, SCTs were more likely male, older age, and had larger tumor sizes. The prevalence of a USP8 mutation was significantly higher in FCT than in SCT.

CONCLUSION

SCT was demographically, clinicopathologically, and prognostically distinct from other NFTs and FCTs. These tumors should be considered high-risk; appropriate treatment decisions and more stringent follow-up should be tailored to improve patient outcomes.

Genomics, Transcriptomics, and Epigenetics of Sporadic Pituitary Tumors

Pituitary tumors (PT) are highly heterogeneous neoplasms, comprising functioning and nonfunctioning lesions. Functioning PT include prolactinomas, causing amenorrhea-galactorrhea in women and sexual dysfunction in men; GH-secreting adenomas causing acromegaly-gigantism; ACTH-secreting corticotrophinomas causing Cushing disease (CD); and the rare TSH-secreting thyrotrophinomas that result in central hyperthyroidism. Nonfunctioning PT do not result in a hormonal hypersecretion syndrome and most of them are of gonadotrope differentiation; other non-functioning PT include null cell adenomas and silent ACTH-, GH- and PRL-adenomas. Less than 5% of PT occur in a familial or syndromic context whereby germline mutations of specific genes account for their molecular pathogenesis. In contrast, the more common sporadic PT do not result from a single molecular abnormality but rather emerge from several oncogenic events that culminate in an increased proliferation of pituitary cells, and in the case of functioning tumors, in a non-regulated hormonal hypersecretion. In recent years, important advances in the understanding of the molecular pathogenesis of PT have been made, including the genomic, transcriptomic, epigenetic, and proteomic characterization of these neoplasms. In this review, we summarize the available molecular information pertaining the oncogenesis of PT.

Clinical Spectrum of USP8 Pathogenic Variants in Cushing's Disease

Cushing's disease (CD) is a life-threatening condition with a challenging diagnostic process and scarce treatment options. CD is caused by usually benign adrenocorticotrophic hormone (ACTH)-secreting pituitary neuroendocrine tumors (PitNETs), known as corticotropinomas. These tumors are predominantly of sporadic origin, and usually derive from the monoclonal expansion of a mutated cell. Somatic activating variants located within a hotspot of the USP8 gene are present in 11-62% of corticotropinomas, making USP8 the most frequent genetic driver of corticotroph neoplasia. In contrast, other somatic defects such as those affecting the glucocorticoid receptor gene (NR3C1), the BRAF oncogene, the deubiquitinase-encoding gene USP48, and TP53 are infrequent. Moreover, patients with familial tumor syndromes, such as multiple endocrine neoplasia, familial isolated pituitary adenoma, and DICER1 rarely develop corticotropinomas. One of the main molecular alterations in USP8-driven tumors is an overactivation of the epidermal growth factor receptor (EGFR) signaling pathway, which induces ACTH production. Hotspot USP8 variants lead to persistent EGFR overexpression, thereby perpetuating the hyper-synthesis of ACTH. More importantly, they condition a characteristic transcriptomic signature that might be useful for the clinical prognosis of patients with CD. Nevertheless, the clinical phenotype associated with USP8 variants is less well defined. Hereby we discuss the current knowledge on the molecular pathogenesis and clinical picture associated with USP8 hotspot variants. We focus on the potential significance of the USP8 mutational status for the design of tailored clinical strategies in CD.

Interpetrosal sphingosine-1-phosphate ratio predicting Cushing's disease tumor laterality and remission after surgery

Background

Cushing's disease (CD) poses significant challenges in its treatment due to the lack of reliable biomarkers for predicting tumor localization or postoperative clinical outcomes. Sphingosine-1-phosphate (S1P) has been shown to increase cortisol biosynthesis and is regulated by adrenocorticotropic hormone (ACTH).

Methods

We employed bilateral inferior petrosal sinus sampling (BIPSS), which is considered the gold standard for diagnosing pituitary sources of CD, to obtain blood samples and explore the clinical predictive value of the S1P concentration ratio in determining tumor laterality and postoperative remission. We evaluated 50 samples from 25 patients who underwent BIPSS to measure S1P levels in the inferior petrosal sinuses bilaterally.

Results

Serum S1P levels in patients with CD were significantly higher on the adenoma side of the inferior petrosal sinus than on the nonadenoma side (397.7 ± 15.4 vs. 261.9 ± 14.88; P < 0.05). The accuracy of diagnosing tumor laterality with the interpetrosal S1P and ACTH ratios and the combination of the two was 64%, 56% and 73%, respectively. The receiver operating characteristic curve analysis revealed that the combination of interpetrosal S1P and ACTH ratios, as a predictor of tumor laterality, exhibited a sensitivity of 81.82% and a specificity of 75%, with an area under the curve value of 84.09%. Moreover, we observed that a high interpetrosal S1P ratio was associated with nonremission after surgery. Correlation analyses demonstrated that the interpetrosal S1P ratio was associated with preoperative follicle-stimulating hormone (FSH), luteinizing hormone (LH), and postoperative ACTH 8 am levels (P < 0.05).

Conclusion

Our study demonstrated a significant association between the interpetrosal S1P ratio and tumor laterality, as well as postoperative remission in CD, suggesting that the interpetrosal S1P ratio could serve as a valuable biomarker in clinical practice.

Aggressive PitNETs and Potential Target Therapies: A Systematic Review of Molecular and Genetic Pathways

Recently, advances in molecular biology and bioinformatics have allowed a more thorough understanding of tumorigenesis in aggressive PitNETs (pituitary neuroendocrine tumors) through the identification of specific essential genes, crucial molecular pathways, regulators, and effects of the tumoral microenvironment. Target therapies have been developed to cure oncology patients refractory to traditional treatments, introducing the concept of precision medicine. Preliminary data on PitNETs are derived from preclinical studies conducted on cell cultures, animal models, and a few case reports or small case series. This study comprehensively reviews the principal pathways involved in aggressive PitNETs, describing the potential target therapies. A search was conducted on Pubmed, Scopus, and Web of Science for English papers published between 1 January 2004, and 15 June 2023. 254 were selected, and the topics related to aggressive PitNETs were recorded and discussed in detail: epigenetic aspects, membrane proteins and receptors, metalloprotease, molecular pathways, PPRK, and the immune microenvironment. A comprehensive comprehension of the molecular mechanisms linked to PitNETs' aggressiveness and invasiveness is crucial. Despite promising preliminary findings, additional research and clinical trials are necessary to confirm the indications and effectiveness of target therapies for PitNETs.

Aggressive Pituitary Tumors and Pituitary Carcinomas: From Pathology to Treatment

Aggressive pituitary tumors (APTs) and pituitary carcinomas (PCs) are heterogeneous with regard to clinical presentation, proliferative markers, clinical course, and response to therapy. Half of them show an aggressive course only many years after the first apparently benign presentation. APTs and PCs share several properties, but a Ki67 index greater than or equal to 10% and extensive p53 expression are more prevalent in PCs. Mutations in TP53 and ATRX are the most common genetic alterations; their detection might be of value for early identification of aggressiveness. Treatment requires a multimodal approach including surgery, radiotherapy, and drugs. Temozolomide is the recommended first-line chemotherapy, with response rates of about 40%. Immune checkpoint inhibitors have emerged as second-line treatment in PCs, with currently no evidence for a superior effect of dual therapy compared to monotherapy with PD-1 blockers. Bevacizumab has resulted in partial response (PR) in few patients; tyrosine kinase inhibitors and everolimus have generally not been useful. The effect of peptide receptor radionuclide therapy is limited as well. Management of APT/PC is challenging and should be discussed within an expert team with consideration of clinical and pathological findings, age, and general condition of the patient. Considering that APT/PCs are rare, new therapies should preferably be evaluated in shared standardized protocols. Prognostic and predictive markers to guide treatment decisions are needed and are the scope of ongoing research.

Refractory corticotroph adenomas

The majority of corticotroph adenomas are benign but some are locally invasive, demonstrate high rates of recurrence, and exhibit a relatively poor response to often repeated surgical, medical, and radiation treatment. Herein, we summarize the currently known somatic and genetic mutations and other molecular factors that influence the pathogenesis of these tumors and discuss currently available therapies. Although recent molecular studies have advanced our understanding of the pathogenesis and behavior of these refractory corticotroph adenomas, these insights do not reliably guide treatment choices at present. Development of additional diagnostic tools and novel tumor-directed therapies that offer efficacious treatment choices for patients with refractory corticotroph adenomas are needed.

Pituitary Tumorigenesis-Implications for Management

Pituitary neuroendocrine tumors (PitNETs), the third most common intracranial tumor, are mostly benign. However, some of them may display a more aggressive behavior, invading into the surrounding structures. While they may rarely metastasize, they may resist different treatment modalities. Several major advances in molecular biology in the past few years led to the discovery of the possible mechanisms involved in pituitary tumorigenesis with a possible therapeutic implication. The mutations in the different proteins involved in the Gsa/protein kinase A/c AMP signaling pathway are well-known and are responsible for many PitNETS, such as somatotropinomas and, in the context of syndromes, as the McCune-Albright syndrome, Carney complex, familiar isolated pituitary adenoma (FIPA), and X-linked acrogigantism (XLAG). The other pathways involved are the MAPK/ERK, PI3K/Akt, Wnt, and the most recently studied HIPPO pathways. Moreover, the mutations in several other tumor suppressor genes, such as menin and CDKN1B, are responsible for the MEN1 and MEN4 syndromes and succinate dehydrogenase (SDHx) in the context of the 3PAs syndrome. Furthermore, the pituitary stem cells and miRNAs hold an essential role in pituitary tumorigenesis and may represent new molecular targets for their diagnosis and treatment. This review aims to summarize the different cell signaling pathways and genes involved in pituitary tumorigenesis in an attempt to clarify their implications for diagnosis and management.

The hallmarks of cancer… in pituitary tumors?

Over 20 years ago, Hanahan and Weinberg published a seminal review that addressed the biological processes that underly malignant transformation. This classical review, along with two revisions published in 2011 and 2022, has remain a classic of the oncology literature. Since many of the addressed biological processes may apply to non-malignant tumorigenesis, we evaluated to what extent these hallmarks pertain to the development of pituitary adenomas.Some of the biological processes analyzed in this review include genome instability generated by somatic USP8 and GNAS mutations in Cushing's diseases and acromegaly respectively; non-mutational epigenetic reprograming through changes in methylation; induction of angiogenesis through alterations of VEGF gene expression; promotion of proliferative signals mediated by EGFR; evasion of growth suppression by disrupting cyclin dependent kinase inhibitors; avoidance of immune destruction; and the promotion of inflammation mediated by alteration of gene expression of immune check points. We also elaborate further on the existence of oncogene induced senescence in pituitary tumors. We conclude that a better understanding of these processes can help us dilucidated why pituitary tumors are so resistant to malignant transformation and can potentially contribute to the development of novel anticancer treatments.

New advances in endocrine hypertension: from genes to biomarkers

Hypertension (HT) is a major cardiovascular risk factor that affects 10% to 40% of the general population in an age-dependent manner. Detection of secondary forms of HT is particularly important because it allows the targeted management of the underlying disease. Among hypertensive patients, the prevalence of endocrine HT reaches up to 10%. Adrenal diseases are the most frequent cause of endocrine HT and are associated with excess production of mineralocorticoids (mainly primary aldosteronism), glucocorticoids (Cushing syndrome), and catecholamines (pheochromocytoma). In addition, a few rare diseases directly affecting the action of mineralocorticoids and glucocorticoids in the kidney also lead to endocrine HT. Over the past years, genomic and genetic studies have allowed improving our knowledge on the molecular mechanisms of endocrine HT. Those discoveries have opened new opportunities to transfer knowledge to clinical practice for better diagnosis and specific treatment of affected subjects. In this review, we describe the physiology of adrenal hormone biosynthesis and action, the clinical and biochemical characteristics of different forms of endocrine HT, and their underlying genetic defects. We discuss the impact of these discoveries on diagnosis and management of patients, as well as new perspectives related to the use of new biomarkers for improved patient care.

Ubiquitin-Specific Proteases (USPs) and Metabolic Disorders

Ubiquitination and deubiquitination are reversible processes that modify the characteristics of target proteins, including stability, intracellular localization, and enzymatic activity. Ubiquitin-specific proteases (USPs) constitute the largest deubiquitinating enzyme family. To date, accumulating evidence indicates that several USPs positively and negatively affect metabolic diseases. USP22 in pancreatic β-cells, USP2 in adipose tissue macrophages, USP9X, 20, and 33 in myocytes, USP4, 7, 10, and 18 in hepatocytes, and USP2 in hypothalamus improve hyperglycemia, whereas USP19 in adipocytes, USP21 in myocytes, and USP2, 14, and 20 in hepatocytes promote hyperglycemia. In contrast, USP1, 5, 9X, 14, 15, 22, 36, and 48 modulate the progression of diabetic nephropathy, neuropathy, and/or retinopathy. USP4, 10, and 18 in hepatocytes ameliorates non-alcoholic fatty liver disease (NAFLD), while hepatic USP2, 11, 14, 19, and 20 exacerbate it. The roles of USP7 and 22 in hepatic disorders are controversial. USP9X, 14, 17, and 20 in vascular cells are postulated to be determinants of atherosclerosis. Moreover, mutations in the Usp8 and Usp48 loci in pituitary tumors cause Cushing syndrome. This review summarizes the current knowledge about the modulatory roles of USPs in energy metabolic disorders.

Advances in Molecular Pathophysiology and Targeted Therapy for Cushing's Disease

Cushing's disease is caused by autonomous secretion of adrenocorticotropic hormone (ACTH) from corticotroph pituitary neuroendocrine tumors. As a result, excess cortisol production leads to the overt manifestation of the clinical features of Cushing's syndrome. Severe complications have been reported in patients with Cushing's disease, including hypertension, menstrual disorders, hyperglycemia, osteoporosis, atherosclerosis, infections, and mental disorders. Cushing's disease presents with a variety of clinical features, ranging from overt to subtle. In this review, we explain recent advances in molecular insights and targeted therapy for Cushing's disease. The pathophysiological characteristics of hormone production and pituitary tumor cells are also explained. Therapies to treat the tumor growth in the pituitary gland and the autonomous hypersecretion of ACTH are discussed. Drugs that target corticotroph pituitary neuroendocrine tumors have been effective, including cabergoline, a dopamine receptor type 2 agonist, and pasireotide, a multi-receptor-targeted somatostatin analog. Some of the drugs that target adrenal hormones have shown potential therapeutic benefits. Advances in potential novel therapies for Cushing's disease are also introduced.

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.

Epigenomic and somatic mutations of pituitary tumors with clinical and pathological correlations in 111 patients

OBJECTIVE

To profile clinically non-aggressive and aggressive pituitary adenomas (PAs)/pituitary neuroendocrine tumours (PitNETs) and pituitary carcinomas for somatic mutations and epigenetic alterations of genes involved in cell proliferation/differentiation, microRNAs (miRNA)/long noncoding RNA (LncRNA)-post-transcriptional regulators and therapy targets.

DESIGN

Retrospective observational study.

PATIENTS AND MEASUREMENTS

A total of 64 non-aggressive and 41 aggressive PAs/PitNETs and 6 pituitary carcinomas treated by endoscopic surgery with ≥1-year follow-up were included. Somatic mutations of 17 genes and DNA methylation of 22 genes were assessed. Ten normal pituitaries were used as control.

RESULTS

We found at least one mutation in 17 tumours, including 6/64 non-aggressive, 10/41 aggressive PAs/PitNETs, and 1/6 pituitary carcinoma. AIP (N = 6) was the most frequently mutated gene, followed by NOTCH (4), and TP53 (3). Hypermethylation of PARP15, LINC00599, ZAP70 was more common in aggressive than non-aggressive PAs/PITNETs (p &lt; .05). Lower levels of methylation of AIP, GNAS and PDCD1 were detected in aggressive PAs/PITNETs than non-aggressive ones (p &lt; .05). For X-linked genes, males presented higher level of methylation of FLNA, UXT and MAGE family (MAGEA11, MAGEA1, MAGEC2) genes in aggressive vs. non-aggressive PAs/PITNETs (p &lt; .05). In pituitary carcinomas, methylation of autosomal genes PARP15, LINC00599, MIR193 and ZAP70 was higher than in PAs/PITNETs, while X-linked genes methylation level was lower.

CONCLUSIONS

Somatic mutations and methylation levels of genes involved in cell proliferation/differentiation, miRNA/LncRNA-post-transcriptional regulators and targets of antineoplastic therapies are different in non-aggressive and in aggressive PAs/PitNETs. Methylation profile also varies according to gender. Combined genetic-epigenetic analysis, in association with clinico-radiological-pathological data, may be of help in predicting PA/PitNET behaviour.

The Expression of Cell Cycle-Related Genes in USP8-Mutated Corticotroph Neuroendocrine Pituitary Tumors and Their Possible Role in Cell Cycle-Targeting Treatment

Protein deubiquitinases USP8 and USP48 are known driver genes in corticotroph pituitary neuroendocrine tumors (PitNETs). USP8 mutations have pleiotropic effects that include notable changes in genes' expression. Genes involved in cell cycle regulation were found differentially expressed in mutated and wild-type tumors. This study aimed to verify difference in the expression level of selected cell cycle-related genes and investigate their potential role in response to cell cycle inhibitors. Analysis of 70 corticotroph PitNETs showed that USP8-mutated tumors have lower CDKN1B, CDK6, CCND2 and higher CDC25A expression. USP48-mutated tumors have lower CDKN1B and CCND1 expression. A lower p27 protein level in mutated than in wild-type tumors was confirmed that may potentially influence the response to small molecule inhibitors targeting the cell cycle. We looked for the role of USP8 mutations or a changed p27 level in the response to palbociclib, flavopiridol and roscovitine in vitro using murine corticotroph AtT-20/D16v-F2 cells. The cells were sensitive to each agent and treatment influenced the expression of genes involved in cell cycle regulation. Overexpression of mutated Usp8 in the cells did not affect the expression of p27 nor the response to the inhibitors. Downregulating or upregulating p27 expression in AtT-20/D16v-F2 cells also did not affect treatment response.

Diagnosis and management of hypertension in patients with Cushing's syndrome: a position statement and consensus of the Working Group on Endocrine Hypertension of the European Society of Hypertension

Endogenous/exogenous Cushing's syndrome is characterized by a cluster of systemic manifestations of hypercortisolism, which cause increased cardiovascular risk. Its biological basis is glucocorticoid excess, acting on various pathogenic processes inducing cardiovascular damage. Hypertension is a common feature in Cushing's syndrome and may persist after normalizing hormone excess and discontinuing steroid therapy. In endogenous Cushing's syndrome, the earlier the diagnosis the sooner management can be employed to offset the deleterious effects of excess cortisol. Such management includes combined treatments directed against the underlying cause and tailored antihypertensive drugs aimed at controlling the consequences of glucocorticoid excess. Experts on endocrine hypertension and members of the Working Group on Endocrine Hypertension of the European Society of Hypertension (ESH) prepared this Consensus document, which summarizes the current knowledge in epidemiology, genetics, diagnosis, and treatment of hypertension in Cushing's syndrome.

Molecular genetic testing in the management of pituitary disease

OBJECTIVE

Most pituitary tumours occur sporadically without a genetically identifiable germline abnormality, a small but increasing proportion present with a genetic defect that predisposes to pituitary tumour development, either isolated (e.g., aryl hydrocarbon receptor-interacting protein, AIP) or as part of a tumour-predisposing syndrome (e.g., multiple endocrine neoplasia (MEN) type 1, Carney complex, McCune-Albright syndrome or pituitary tumour and paraganglioma association). Genetic alterations in sporadic pituitary adenomas may include somatic mutations (e.g., GNAS, USP8). In this review, we take a practical approach: which genetic syndromes should be considered in case of different presentation, such as tumour type, family history, age of onset and additional clinical features of the patient.

DESIGN

Review of the recent literature in the field of genetics of pituitary tumours.

RESULTS

Genetic testing in the management of pituitary disease is recommended in a significant minority of the cases. Understanding the genetic basis of the disease helps to identify patients and at-risk family members, facilitates early diagnosis and therefore better long-term outcome and opens up new pathways leading to tumorigenesis.

CONCLUSION

We provide a concise overview of the genetics of pituitary tumours and discuss the current challenges and implications of these genetic findings in clinical practice.

Molecular Derangements and the Diagnosis of ACTH-Dependent Cushing's Syndrome

Endogenous Cushing's syndrome (CS) is associated with morbidities (diabetes, hypertension, clotting disorders) and shortens life because of infections, pulmonary thromboembolism, and cardiovascular disease. Its clinical presentation is immensely variable, and diagnosis and treatment are often delayed. Thus, there are many opportunities for basic and clinical research leading to better tests, faster diagnosis, and optimized medical treatments. This review focuses on CS caused by excessive adrenocorticotropin (ACTH) production. It describes current concepts of the regulation of ACTH synthesis and secretion by normal corticotropes and mechanisms by which dysregulation occurs in corticotrope (termed "Cushing's disease") and noncorticotrope (so-called ectopic) ACTH-producing tumors. ACTH causes adrenal gland synthesis and pulsatile release of cortisol; the excess ACTH in these forms of CS leads to the hypercortisolism of endogenous CS. Again, the differences between healthy individuals and those with CS are highlighted. The clinical presentations and their use in the interpretation of CS screening tests are described. The tests used for screening and differential diagnosis of CS are presented, along with their relationship to cortisol dynamics, pathophysiology, and negative glucocorticoid feedback regulation in the two forms of ACTH-dependent CS. Finally, several gaps in current understanding are highlighted in the hope of stimulating additional research into this challenging disorder.

TP53 mutations in functional corticotroph tumors are linked to invasion and worse clinical outcome

Corticotroph macroadenomas are rare but difficult to manage intracranial neoplasms. Mutations in the two Cushing's disease mutational hotspots USP8 and USP48 are less frequent in corticotroph macroadenomas and invasive tumors. There is evidence that TP53 mutations are not as rare as previously thought in these tumors. The aim of this study was to determine the prevalence of TP53 mutations in corticotroph tumors, with emphasis on macroadenomas, and their possible association with clinical and tumor characteristics. To this end, the entire TP53 coding region was sequenced in 86 functional corticotroph tumors (61 USP8 wild type; 66 macroadenomas) and the clinical characteristics of patients with TP53 mutant tumors were compared with TP53/USP8 wild type and USP8 mutant tumors. We found pathogenic TP53 variants in 9 corticotroph tumors (all macroadenomas and USP8 wild type). TP53 mutant tumors represented 14% of all functional corticotroph macroadenomas and 24% of all invasive tumors, were significantly larger and invasive, and had higher Ki67 indices and Knosp grades compared to wild type tumors. Patients with TP53 mutant tumors had undergone more therapeutic interventions, including radiation and bilateral adrenalectomy. In conclusion, pathogenic TP53 variants are more frequent than expected, representing a relevant amount of functional corticotroph macroadenomas and invasive tumors. TP53 mutations associated with more aggressive tumor features and difficult to manage disease.

Improved pasireotide response in USP8 mutant corticotroph tumours in vitro

Cushing's disease is a rare but devastating and difficult to manage condition. The somatostatin analogue pasireotide is the only pituitary-targeting pharmaceutical approved for the treatment of Cushing's disease but is accompanied by varying efficacy and potentially severe side effects. Finding means to predict which patients are more likely to benefit from this treatment may improve their management. More than half of corticotroph tumours harbour mutations in the USP8 gene, and there is evidence of higher somatostatin receptor 5 (SSTR5) expression in the USP8-mutant tumours. Pasireotide has a high affinity for SSTR5, indicating that these tumours may be more sensitive to treatment. To test this hypothesis, we examined the inhibitory action of pasireotide on adrenocorticotrophic hormone synthesis in primary cultures of human corticotroph tumour with assessed USP8 mutational status and in immortalized murine corticotroph tumour cells overexpressing human USP8 mutants frequent in Cushing's disease. Our in vitro results demonstrate that pasireotide exerts a higher antisecretory response in USP8-mutant corticotroph tumours. Overexpressing USP8 mutants in a murine corticotroph tumour cell model increased endogenous somatostatin receptor 5 (Sstr5) transcription. The murine Sstr5 promoter has two binding sites for the activating protein 1 (AP-1) and USP8 mutants possibly to mediate their action by stimulating AP-1 transcriptional activity. Our data corroborate the USP8 mutational status as a potential marker of pasireotide response and describe a potential mechanism through which USP8 mutants may regulate SSTR5 gene expression.

The corticotroph cells from early development to tumorigenesis

During development, highly specialized differentiated cells, such as pituitary secretory cells, acquire their identity and properties through a series of specification events exerted by transcription factors to implement a unique gene expression program and epigenomic state. The investigation of these developmental processes informs us on the unique features of a cell lineage, both to explain these features and also to outline where these processes may fail and cause disease. This review summarizes present knowledge on the developmental origin of pituitary corticotroph and melanotroph cells and on the underlying molecular mechanisms. At the onset, comparison of gene expression programs active in pituitary progenitors compared to those active in differentiated corticotrophs or melanotrophs indicated dramatic differences in the control of, for example, the cell cycle. Tpit is the transcription factor that determines terminal differentiation of pro-opiomelanocortin (POMC) lineages, both corticotrophs and melanotrophs, and its action involves this switch in cell cycle control in parallel with activation of cell-specific gene expression. There is thus far more to making a corticotroph cell than just activating transcription of the POMC gene. Indeed, Tpit also controls implementation of mechanisms for enhanced protein translation capacity and development of extensive secretory organelles. The corticotroph cell identity also includes mechanisms responsible for homotypic cell-cell interactions between corticotrophs and for privileged heterotypic cell interactions with pituitary cells of other lineages. The review also summarizes current knowledge on how a pioneer transcription factor, Pax7, remodels the epigenome such that the same determination transcription factor, Tpit, will implement the melanotroph program of gene expression. Finally, this canvas of regulatory mechanisms implementing POMC lineage identities constitutes the background to understand alterations that characterize corticotroph adenomas of Cushing's disease patients. The integration of all these data into a unified scheme will likely yield a scheme to globally understand pathogenic mechanisms in Cushing's disease.

Genetics of Cushing's disease

Corticotroph tumours are primarily sporadic monoclonal neoplasms and only rarely found in genetic syndromes. Recurrent mutations in the ubiquitin specific protease 8 (USP8) gene are found in around half of cases. Mutations in other genes such as USP48 and NR3C1 are less frequent, found in less than ~20% of cases. TP53 and ATXR mutations are reported in up to one out of four cases, when focusing in USP8 wild type or aggressive corticotroph tumours and carcinomas. At present, USP8 mutations are the primary driver alterations in sporadic corticotroph tumours, TP53 and ATXR mutations may indicate transition to more aggressive tumour phenotype. Next generation sequencing efforts have identified additional genomic alterations, whose role and importance in corticotroph tumorigenesis remains to be elucidated.

Disease Modeling of Pituitary Adenoma Using Human Pluripotent Stem Cells

Simple Summary

Pituitary adenoma pathophysiology has been studied mainly using murine cell lines, animal models, and pituitary tumor samples. However, the lack of human pituitary cell line is a significant limiting factor in studying the molecular mechanisms of human pituitary tumors. Recently, pituitary induction methods from human-induced pluripotent stem cells (hiPSCs) have been established. These methods can induce human pituitary hormone-producing cells that retain physiological properties. hiPSCs in which tumor-causing gene mutations are introduced using genome-editing techniques, such as CRISPR/Cas9 systems, provide great opportunities to establish in vitro human pituitary adenoma disease models. The models will be a novel platform to discover novel drugs and investigate tumorigenesis and pathophysiology. The purpose of this review is to provide an overview of the applications of iPSCs for pituitary and neoplastic disorder research and genome-editing technologies to create strategies for developing pituitary adenoma models using iPSCs.

Abstract

Pituitary adenomas are characterized by abnormal growth in the pituitary gland. Surgical excision is the first-line treatment for functional (hormone-producing) pituitary adenomas, except for prolactin-producing adenomas; however, complete excision is technically challenging, and many patients require long-term medication after the treatment. In addition, the pathophysiology of pituitary adenomas, such as tumorigenesis, has not been fully understood. Pituitary adenoma pathophysiology has mainly been studied using animal models and animal tumor-derived cell lines. Nevertheless, experimental studies on human pituitary adenomas are difficult because of the significant differences among species and the lack of reliable cell lines. Recently, several methods have been established to differentiate pituitary cells from human pluripotent stem cells (hPSCs). The induced pituitary hormone-producing cells retain the physiological properties already lost in tumor-derived cell lines. Moreover, CRISPR/Cas9 systems have expedited the introduction of causative gene mutations in various malignant tumors into hPSCs. Therefore, hPSC-derived pituitary cells have great potential as a novel platform for studying the pathophysiology of human-specific pituitary adenomas and developing novel drugs. This review presents an overview of the recent progresses in hPSC applications for pituitary research, functional pituitary adenoma pathogenesis, and genome-editing techniques for introducing causative mutations. We also discuss future applications of hPSCs for studying pituitary adenomas.

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.

Concurrent mutations of germline GPR101 and somatic USP8 in a pediatric giant pituitary ACTH adenoma: a case report

BACKGROUND

Cushing's disease (CD) is rare in pediatric patients. It is characterized by elevated plasma adrenocorticotropic hormone (ACTH) from pituitary adenomas, with damage to multiple systems and development. In recent years, genetic studies have shed light on the etiology and several mutations have been identified in patients with CD.

CASE PRESENTATION

A girl presented at the age of 10 years and 9 months with facial plethora, hirsutism and acne. Her vision and eye movements were impaired. A quick weight gain and slow growth were also observed. Physical examination revealed central obesity, moon face, buffalo hump, supra-clavicular fat pads and bruising. Her plasma ACTH level ranged between 118 and 151 pg/ml, and sella enhanced MRI showed a giant pituitary tumor of 51.8 × 29.3 × 14.0 mm. Transsphenoidal pituitary debulk adenomectomy was performed and immunohistochemical staining confirmed an ACTH-secreting adenoma. Genetic analysis identified a novel germline GPR101 (p.G169R) and a somatic USP8 (p. S719del) mutation. They were hypothesized to impact tumor growth and function, respectively.

CONCLUSIONS

We reported a rare case of pediatric giant pituitary ACTH adenoma and pointed out that unusual concurrent mutations might contribute to its early onset and large volume.

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.

The Genomic Landscape of Corticotroph Tumors: From Silent Adenomas to ACTH-Secreting Carcinomas

Corticotroph cells give rise to aggressive and rare pituitary neoplasms comprising ACTH-producing adenomas resulting in Cushing disease (CD), clinically silent ACTH adenomas (SCA), Crooke cell adenomas (CCA) and ACTH-producing carcinomas (CA). The molecular pathogenesis of these tumors is still poorly understood. To better understand the genomic landscape of all the lesions of the corticotroph lineage, we sequenced the whole exome of three SCA, one CCA, four ACTH-secreting PA causing CD, one corticotrophinoma occurring in a CD patient who developed Nelson syndrome after adrenalectomy and one patient with an ACTH-producing CA. The ACTH-producing CA was the lesion with the highest number of single nucleotide variants (SNV) in genes such as USP8, TP53, AURKA, EGFR, HSD3B1 and CDKN1A. The USP8 variant was found only in the ACTH-CA and in the corticotrophinoma occurring in a patient with Nelson syndrome. In CCA, SNV in TP53, EGFR, HSD3B1 and CDKN1A SNV were present. HSD3B1 and CDKN1A SNVs were present in all three SCA, whereas in two of these tumors SNV in TP53, AURKA and EGFR were found. None of the analyzed tumors showed SNV in USP48, BRAF, BRG1 or CABLES1. The amplification of 17q12 was found in all tumors, except for the ACTH-producing carcinoma. The four clinically functioning ACTH adenomas and the ACTH-CA shared the amplification of 10q11.22 and showed more copy-number variation (CNV) gains and single-nucleotide variations than the nonfunctioning tumors.

USP8, USP48, and BRAF mutations differ in their genotype-phenotype correlation in Asian Indian patients with Cushing's disease

PURPOSE

To estimate the prevalence of USP8, USP48, and BRAF mutations in patients with Cushing's disease (CD) from the Indian subcontinent, and determine their genotype-phenotype correlation.

METHODS

We prospectively recruited 46 patients with CD who underwent surgery between September 2015 and July 2019 at our institute. Fresh frozen tumour tissue was obtained in all patients. Using Sanger sequencing, the presence of somatic USP8 mutations was documented and the frequency of USP48 and BRAF mutations in USP8 wild-type corticotroph adenomas was determined. Clinical, hormonal, and surgical data were then compared between USP8-, USP48- and BRAF-variant carriers and patients with wild-type tumours.

RESULTS

Signature USP8 mutations were detected in 17 (37%) patients. Of the 29 USP8 wild-type adenomas, 4 (13.8%) harboured USP48 mutations, one of them being a splice-site mutation that has previously not been described. BRAF mutations were not found in any of the 29 patients. Corticotroph adenomas with USP8 mutations had a higher incidence of Crooke's hyaline change than wild-type tumours (70.6 vs. 37.9%, p = 0.032). Adenomas with USP48 mutations had a higher rate of cavernous sinus invasion than their wild-type counterparts (50 vs. 4%, p = 0.042). No other significant phenotypic difference could be established between mutant and wild-type tumours.

CONCLUSIONS

The prevalence of USP8 mutations in our series of patients with CD was 37%. The prevalence of USP48 mutations in USP8 wild-type adenomas was 13.8%, including a novel splice-site mutation. BRAF mutations were not found in any USP8 wild-type tumour. USP8-mutants showed significantly more Crooke's hyaline change and USP48-mutants were more likely to demonstrate cavernous sinus invasion.

Molecular mechanisms involved in somatostatin receptor regulation in corticotroph tumors: the role of cytoskeleton and USP8 mutations

Adrenocorticotropic hormone (ACTH)-secreting pituitary tumors mainly express somatostatin receptor 5 (SSTR5) since SSTR2 is downregulated by the elevated levels of glucocorticoids that characterize patients with Cushing's disease (CD). SSTR5 is the molecular target of pasireotide, the only approved pituitary tumor-targeted drug for the treatment of CD. However, the molecular mechanisms that regulate SSTR5 are still poorly investigated. This review summarizes the experimental evidence supporting the role of the cytoskeleton actin-binding protein filamin A (FLNA) in the regulation of SSTR5 expression and signal transduction in corticotroph tumors. Moreover, the correlations between the presence of somatic USP8 mutations and the expression of SSTR5 will be reviewed. An involvement of glucocorticoid-mediated β-arrestins modulation in regulating SSTRs expression and function in ACTH-secreting tumors will also be discussed.

Paediatric Cushing's disease: Epidemiology, pathogenesis, clinical management and outcome

Cushing's disease (CD) is rare in paediatric practice but requires prompt investigation, diagnosis and therapy to prevent long-term complications. Key presenting features are a change in facial appearance, weight gain, growth failure, virilization, disturbed puberty and psychological disturbance. Close consultation with an adult endocrinology department is recommended regarding diagnosis and therapy. The incidence of CD, a form of ACTH-dependent Cushing's syndrome (CS), is equal to approximately 5% of that seen in adults. The majority of ACTH-secreting adenomas are monoclonal and sporadic, although recent studies of pituitary tumours have shown links to several deubiquitination gene defects. Diagnosis requires confirmation of hypercortisolism followed by demonstration of ACTH-dependence. Identification of the corticotroph adenoma by pituitary MRI and/or bilateral inferior petrosal sampling for ACTH may contribute to localisation before pituitary surgery. Transsphenoidal surgery (TSS) with selective microadenomectomy is first-line therapy, followed by external pituitary irradiation if surgery is not curative. Medical therapy to suppress adrenal steroid synthesis is effective in the short-term and bilateral adrenalectomy should be considered in cases unfit for TSS or radiotherapy or when urgent remission is needed after unsuccessful surgery. TSS induces remission of hypercortisolism and improvement of symptoms in 70-100% of cases, particularly when performed by a surgeon with experience in children. Post-TSS complications include pituitary hormone deficiencies, sub-optimal catch-up growth, and persisting excess of BMI. Recurrence of hypercortisolism following remission is recognised but infrequent, being less common than in adult CD patients. With experienced specialist medical and surgical care, the overall prognosis is good. Early referral to an experienced endocrine centre is advised.

Molecular basis of ubiquitin-specific protease 8 autoinhibition by the WW-like domain

Ubiquitin-specific protease 8 (USP8) is a deubiquitinating enzyme involved in multiple membrane trafficking pathways. The enzyme activity is inhibited by binding to 14-3-3 proteins. Mutations in the 14-3-3-binding motif in USP8 are related to Cushing’s disease. However, the molecular basis of USP8 activity regulation remains unclear. This study identified amino acids 645–684 of USP8 as an autoinhibitory region, which might interact with the catalytic USP domain, as per the results of pull-down and single-molecule FRET assays performed in this study. In silico modelling indicated that the region forms a WW-like domain structure, plugs the catalytic cleft, and narrows the entrance to the ubiquitin-binding pocket. Furthermore, 14-3-3 inhibited USP8 activity partly by enhancing the interaction between the WW-like and USP domains. These findings provide the molecular basis of USP8 autoinhibition via the WW-like domain. Moreover, they suggest that the release of autoinhibition may underlie Cushing’s disease due to USP8 mutations.

In order to advance our understanding of the regulation of Ubiquitin-specific protease 8 (USP8), which is known to play a role in Cushing’s Disease, Kakihara et al identify and characterise amino acids 645–684 of USP8, which serve as an autoinhibitory region. Their pull-down and single-molecule FRET analysis, as well as in silico modelling, suggest that the release of USP8 autoinhibition may underlie Cushing’s disease.

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.

Two Distinctive POMC Promoters Modify Gene Expression in Cushing Disease

CONTEXT

Mechanisms underlying pituitary corticotroph adenoma adrenocorticotropin (ACTH) production are poorly understood, yet circulating ACTH levels closely correlate with adenoma phenotype and clinical outcomes.

OBJECTIVE

We characterized the 5' ends of proopiomelanocortin (POMC) gene transcripts, which encode the precursor polypeptide for ACTH, in order to investigate additional regulatory mechanisms of POMC gene transcription and ACTH production.

METHODS

We examined 11 normal human pituitary tissues, 32 ACTH-secreting tumors, as well as 6 silent corticotroph adenomas (SCAs) that immunostain for but do not secrete ACTH.

RESULTS

We identified a novel regulatory region located near the intron 2/exon 3 junction in the human POMC gene, which functions as a second promoter and an enhancer. In vitro experiments demonstrated that CREB binds the second promoter and regulates its transcriptional activity. The second promoter is highly methylated in SCAs, partially demethylated in normal pituitary tissue, and highly demethylated in pituitary and ectopic ACTH-secreting tumors. In contrast, the first promoter is demethylated in all POMC-expressing cells and is highly demethylated only in pituitary ACTH-secreting tumors harboring the ubiquitin-specific protease 8 (USP8) mutation. Demethylation patterns of the second promoter correlate with clinical phenotypes of Cushing disease.

CONCLUSION

We identified a second POMC promoter regulated by methylation status in ACTH-secreting pituitary tumors. Our findings open new avenues for elucidating subcellular regulation of the hypothalamic-pituitary-adrenal axis and suggest the second POMC promoter may be a target for therapeutic intervention to suppress excess ACTH production.

Genetic Profiling of a Cohort of Italian Patients with ACTH-Secreting Pituitary Tumors and Characterization of a Novel USP8 Gene Variant

Simple Summary

Cushing’s Disease (CD) is a rare but severe endocrine disorder due to an adrenocorticotropic hormone (ACTH)-secreting pituitary tumor, and pathogenetics remained a puzzling issue for a long time. The recent identification of somatic mutations in the 14-3-3 protein binding motif of ubiquitin specific peptidase 8 gene (USP8), present in a consistent subgroup of ACTH-secreting pituitary tumors, have represented a major advance in the understanding of CD pathogenesis. In our cohort of 60 patients we found an incidence of 11.7% of USP8 recurrent somatic mutations whereas a novel USP8 variant (G664R) located upstream the canonical USP8 mutational hotspot was identified in one case. This alteration has never been reported by previous records. The present study provides USP8 G664R variant in vitro functional characterization in AtT-20 cells and demonstrates its possible implication in ACTH-secreting tumor pathogenesis, contributing to enlarge the genetic landscape of CD.

Abstract

Cushing’s Disease (CD) is a rare condition characterized by an overproduction of ACTH by an ACTH-secreting pituitary tumor, resulting in an excess of cortisol release by the adrenal glands. Somatic mutations in the deubiquitinases USP8 and USP48, and in BRAF genes, have been reported in a subset of patients affected by CD. The aim of this study was to characterize the genetic profile of a cohort of 60 patients with ACTH-secreting tumors, searching for somatic mutations in USP8, USP48, and BRAF hotspot regions. Seven patients were found to carry USP8 somatic mutations in the well-characterized 14-3-3 protein binding motif (n = 5 P720R, n = 1 P720Q, n = 1 S718del); 2 patients were mutated in USP48 (M415I); no mutation was identified in BRAF. In addition, a novel USP8 variant, G664R, located in exon 14, upstream of the 14-3-3 protein binding motif, was identified in 1 patient. Functional characterization of USP8 G664R variant was performed in murine corticotroph tumor AtT-20 cells. Transient transfection with the USP8 G664R variant resulted in a significant increase of ACTH release and cell proliferation (+114.5 ± 53.6% and +28.3 ± 2.6% vs. empty vector transfected cells, p < 0.05, respectively). Notably, USP8 proteolytic cleavage was enhanced in AtT-20 cells transfected with G664R USP8 (1.86 ± 0.58–fold increase of N-terminal USP8 fragment, vs. WT USP8, p < 0.05). Surprisingly, in situ Proximity Ligation Assay (PLA) experiments showed a significant reduction of PLA positive spots, indicating USP8/14-3-3 proteins colocalization, in G664R USP8 transfected cells with respect to WT USP8 transfected cells (−47.9 ± 6.6%, vs. WT USP8, p < 0.001). No significant difference in terms of ACTH secretion, cell proliferation and USP8 proteolytic cleavage, and 14-3-3 proteins interaction was observed between G664R USP8 and S718del USP8 transfected cells. Immunofluorescence experiments showed that, contrary to S718del USP8 but similarly to WT USP8 and other USP8 mutants, G664R USP8 displays an exclusive cytoplasmic localization. In conclusion, somatic mutations were found in USP8 (13.3% vs. 36.5% incidence of all published mutations) and USP48 (3.3% vs. 13.3% incidence) hotspot regions. A novel USP8 variant was identified in a CD patient, and in vitro functional studies in AtT-20 cells suggested that this somatic variant might be clinically relevant in ACTH-secreting tumor pathogenesis, expanding the characterization of USP8 functional domains.

Large Scale Molecular Studies of Pituitary Neuroendocrine Tumors: Novel Markers, Mechanisms and Translational Perspectives

Simple Summary

Pituitary neuroendocrine tumors are non-cancerous tumors of the pituitary gland, that may overproduce hormones leading to serious health conditions or due to tumor size cause chronic headache, vertigo or visual impairment. In recent years pituitary neuroendocrine tumors are studied with the latest molecular biology methods that simultaneously investigate a large number of factors to understand the mechanisms of how these tumors develop and how they could be diagnosed or treated. In this review article, we have studied literature reports, compiled information and described molecular factors that could affect the development and clinical characteristics of pituitary neuroendocrine tumors, discovered factors that overlap between several studies using large scale molecular analysis and interpreted the potential involvement of these factors in pituitary tumor development. Overall, this study provides a valuable resource for understanding the biology of pituitary neuroendocrine tumors.

Abstract

Pituitary neuroendocrine tumors (PitNETs) are non-metastatic neoplasms of the pituitary, which overproduce hormones leading to systemic disorders, or tumor mass effects causing headaches, vertigo or visual impairment. Recently, PitNETs have been investigated in large scale (exome and genome) molecular analyses (transcriptome microarrays and sequencing), to uncover novel markers. We performed a literature analysis on these studies to summarize the research data and extrapolate overlapping gene candidates, biomarkers, and molecular mechanisms. We observed a tendency in samples with driver mutations (GNAS, USP8) to have a smaller overall mutational rate, suggesting driver-promoted tumorigenesis, potentially changing transcriptome profiles in tumors. However, direct links from drivers to signaling pathways altered in PitNETs (Notch, Wnt, TGF-β, and cell cycle regulators) require further investigation. Modern technologies have also identified circulating nucleic acids, and pinpointed these as novel PitNET markers, i.e., miR-143-3p, miR-16-5p, miR-145-5p, and let-7g-5p, therefore these molecules must be investigated in the future translational studies. Overall, large-scale molecular studies have provided key insight into the molecular mechanisms behind PitNET pathogenesis, highlighting previously reported molecular markers, bringing new candidates into the research field, and reapplying traditional perspectives to newly discovered molecular mechanisms.

USP8 and TP53 Drivers are Associated with CNV in a Corticotroph Adenoma Cohort Enriched for Aggressive Tumors

CONTEXT

Pituitary corticotroph adenomas are rare tumors that can be associated with excess adrenocorticotropin (ACTH) and adrenal cortisol production, resulting in the clinically debilitating endocrine condition Cushing disease. A subset of corticotroph tumors behave aggressively, and genomic drivers behind the development of these tumors are largely unknown.

OBJECTIVE

To investigate genomic drivers of corticotroph tumors at risk for aggressive behavior.

DESIGN

Whole-exome sequencing of patient-matched corticotroph tumor and normal deoxyribonucleic acid (DNA) from a patient cohort enriched for tumors at risk for aggressive behavior.

SETTING

Tertiary care center.

PATIENTS

Twenty-seven corticotroph tumors from 22 patients were analyzed. Twelve tumors were macroadenomas, of which 6 were silent ACTH tumors, 2 were Crooke's cell tumors, and 1 was a corticotroph carcinoma.

INTERVENTION

Whole-exome sequencing.

MAIN OUTCOME MEASURE

Somatic mutation genomic biomarkers.

RESULTS

We found recurrent somatic mutations in USP8 and TP53 genes, both with higher allelic fractions than other somatic mutations. These mutations were mutually exclusive, with TP53 mutations occurring only in USP8 wildtype (WT) tumors, indicating they may be independent driver genes. USP8-WT tumors were characterized by extensive somatic copy number variation compared with USP8-mutated tumors. Independent of molecular driver status, we found an association between invasiveness, macroadenomas, and aneuploidy.

CONCLUSIONS

Our data suggest that corticotroph tumors may be categorized into a USP8-mutated, genome-stable subtype versus a USP8-WT, genome-disrupted subtype, the latter of which has a TP53-mutated subtype with high level of chromosome instability. These findings could help identify high risk corticotroph tumors, namely those with widespread CNV, that may need closer monitoring and more aggressive treatment.

The oncogenic role of ubiquitin specific peptidase (USP8) and its signaling pathways targeting for cancer therapeutics

USP8 is a deubiquitinating enzyme in the family of ubiquitin-specific proteases (USPs) which can remove ubiquitin from the substrate and protect the substrate from degradation. The upregulated or mutated USP8 becomes hyperactivated and stabilizes numerous oncogenes or proto-oncogenes leading to cancer progression and survival by activating multiple signaling pathways. Moreover, USP8 inhibition is also important to overcome anticancer drug-resistant. This review is the first study to find, combine, analyze, and represent the multiple oncogenic signaling pathways with their downstream and upstream regulation activated or enhanced by USP8, which will help the researchers to find any therapeutic strategy for drug discovery by inhibiting or suppressing the multi-targeted USP8.

Somatostatin Receptor as a Molecular Imaging Target in Human and Canine Cushing Disease

OBJECTIVES

Fluorescence-guided surgery may improve completeness of resection in transsphenoidal surgery for Cushing disease (CD) by enabling visualization of residual tumor tissue at the margins. In this review we discuss somatostatin receptors (SSTRs) as targets for fluorescence-guided surgery and overview existing SSTR-specific imaging agents. We also compare SSTR expression in normal pituitary and corticotrophinoma tissues from human and canine CD patients to assess canines as a translational model for CD.

METHODS

A PubMed literature search was conducted for publications containing the terms canine, somatostatin receptor, Cushing's disease, and corticotroph adenoma. SSTR expression data from each study was documented as the presence or absence of expression or, when possible, the number of tumors expressing a given SSTR subtype within a group of tumors being studied. Studies that used reverse transcription polymerase chain reaction to quantify SSTR expression were selected for additional comparative analysis.

RESULTS

SSTR5 is strongly expressed in human corticotroph adenomas and weakly expressed in surrounding pituitary parenchyma, a pattern not conclusively observed in canine patients. SSTR2 mRNA expression is similar in human normal pituitary and corticotrophinoma cells but may be significantly higher in canine normal pituitary tissue than in corticotroph tumoral tissue. Limited data were available on SSTR subtypes 1, 3, and 4.

CONCLUSIONS

Further studies must fill the knowledge gaps related to species-specific SSTR expression, so using canine CD as a translational model may be premature. We do conclude that the expression profile of SSTR5 (i.e., high local expression in pituitary adenomas relative to normal surrounding tissues) makes SSTR5 a promising molecular target for FGS.

Differential microRNA Expression in USP8-Mutated and Wild-Type Corticotroph Pituitary Tumors Reflect the Difference in Protein Ubiquitination Processes

Background: USP8 mutations are the most common driver changes in corticotroph pituitary tumors. They have direct effect on cells’ proteome through disturbance of ubiquitination process and also influence gene expression. The aim of this study was to compare microRNA profiles in USP8-mutated and wild-type tumors and determine the probable role of differential microRNA expression by integrative microRNA and mRNA analysis. Methods: Patients with Cushing’s disease (n = 28) and silent corticotroph tumors (n = 20) were included. USP8 mutations were identified with Sanger sequencing. MicroRNA and gene expression was determined with next-generation sequencing. Results: USP8-mutated patients with Cushing’s disease showed higher rate of clinical remission and trend towards lower tumor volume than wild-type patients. Comparison of microRNA profiles of USP8-mutated and wild-type tumors revealed 68 differentially expressed microRNAs. Their target genes were determined by in silico prediction and microRNA/mRNA correlation analysis. GeneSet Enrichment analysis of putative targets showed that the most significantly overrepresented genes are involved in protein ubiquitination-related processes. Only few microRNAs influence the expression of genes differentially expressed between USP8-mutated and wild-type tumors. Conclusions: Differences in microRNA expression in corticotropinomas stratified according to USP8 status reflect disturbed ubiquitination processes, but do not correspond to differences in gene expression between these tumors.