Activation of cyclic AMP signaling leads to different pathway alterations in lesions of the adrenal cortex caused by germline PRKAR1A defects versus those due to somatic GNAS mutations

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.

Primary bilateral macronodular adrenal hyperplasia: definitely a genetic disease

Primary bilateral macronodular adrenal hyperplasia (PBMAH) is an adrenal cause of Cushing syndrome. Nowadays, a PBMAH diagnosis is more frequent than previously, as a result of progress in the diagnostic methods for adrenal incidentalomas, which are widely available. Although some rare syndromic forms of PBMAH are known to be of genetic origin, non-syndromic forms of PBMAH have only been recognized as a genetic disease in the past 10 years. Genomics studies have highlighted the molecular heterogeneity of PBMAH and identified molecular subgroups, allowing improved understanding of the clinical heterogeneity of this disease. Furthermore, the generation of these subgroups permitted the identification of new genes responsible for PBMAH. Constitutive inactivating variants in ARMC5 and KDM1A are responsible for the development of distinct forms of PBMAH. To date, pathogenic variants of ARMC5 are responsible for 20-25% of PBMAH, whereas germline KDM1A alterations have been identified in >90% of PBMAH causing food-dependent Cushing syndrome. The identification of pathogenic variants in ARMC5 and KDM1A demonstrated that PBMAH, despite mostly being diagnosed in adults aged 45-60 years, is a genetic disorder. This Review summarizes the important progress made in the past 10 years in understanding the genetics of PBMAH, which have led to a better understanding of the pathophysiology, opening new clinical perspectives.

Genetic Alterations in Benign Adrenal Tumors

The genetic basis of most types of adrenal adenomas has been elucidated over the past decade, leading to the association of adrenal gland pathologies with specific molecular defects. Various genetic studies have established links between variants affecting the protein kinase A (PKA) signaling pathway and benign cortisol-producing adrenal lesions. Specifically, genetic alterations in GNAS, PRKAR1A, PRKACA, PRKACB, PDE11A, and PDE8B have been identified. The PKA signaling pathway was initially implicated in the pathogenesis of Cushing syndrome in studies aiming to understand the underlying genetic defects of the rare tumor predisposition syndromes, Carney complex, and McCune-Albright syndrome, both affected by the same pathway. In addition, germline variants in ARMC5 have been identified as a cause of primary bilateral macronodular adrenal hyperplasia. On the other hand, primary aldosteronism can be subclassified into aldosterone-producing adenomas and bilateral idiopathic hyperaldosteronism. Various genes have been reported as causative for benign aldosterone-producing adrenal lesions, including KCNJ5, CACNA1D, CACNA1H, CLCN2, ATP1A1, and ATP2B3. The majority of them encode ion channels or pumps, and genetic alterations lead to ion transport impairment and cell membrane depolarization which further increase aldosterone synthase transcription and aldosterone overproduction though activation of voltage-gated calcium channels and intracellular calcium signaling. In this work, we provide an overview of the genetic causes of benign adrenal tumors.

An Overview of the Heterogeneous Causes of Cushing’s Syndrome due to Primary Macronodular Adrenal Hyperplasia (PMAH)

Primary macronodular adrenal hyperplasia (PMAH) is considered a rare cause of adrenal Cushing syndrome, is pituitary ACTH-independent, generally results from bilateral adrenal macronodules (>1 cm), and is often associated with variable cortisol secretion, resulting in a heterogeneous clinical presentation. Recent advances in the molecular pathogenesis of PMAH have offered new insights into the comprehension of this heterogeneous and complex adrenal disorder. Different molecular mechanisms involving the actors of the cAMP/protein kinase A pathway have been implicated in the development of PMAH, including germline and/or somatic molecular defects such as hyperexpression of the G-protein aberrant receptors and pathogenic variants of MC2R, GNAS, PRKAR1A, and PDE11A. Nevertheless, since 2013, the ARMC5 gene is believed to be a major genetic cause of PMAH, accounting for more than 80% of the familial forms of PMAH and 30% of apparently sporadic cases, except in food-dependent Cushing syndrome in which ARMC5 is not involved. Recently, 2 independent groups have identified that the tumor suppressor gene KDM1A is responsible for PMAH associated specifically with food-dependent Cushing syndrome. Consequently, PMAH has been more frequently genetically associated than previously assumed. This review summarizes the most important aspects, including hormone secretion, clinical presentation, radiological imaging, and molecular mechanisms, involved in familial Cushing syndrome associated with PMAH.

Disorders of the adrenal cortex: Genetic and molecular aspects

Adrenal cortex produces glucocorticoids, mineralocorticoids and adrenal androgens which are essential for life, supporting balance, immune response and sexual maturation. Adrenocortical tumors and hyperplasias are a heterogenous group of adrenal disorders and they can be either sporadic or familial. Adrenocortical cancer is a rare and aggressive malignancy, and it is associated with poor prognosis. With the advance of next-generation sequencing technologies and improvement of genomic data analysis over the past decade, various genetic defects, either from germline or somatic origin, have been unraveled, improving diagnosis and treatment of numerous genetic disorders, including adrenocortical diseases. This review gives an overview of disorders associated with the adrenal cortex, the genetic factors of these disorders and their molecular implications.

Bilateral Adrenal Hyperplasia: Pathogenesis and Treatment

Bilateral adrenal hyperplasia is a rare cause of Cushing’s syndrome. Micronodular adrenal hyperplasia, including the primary pigmented micronodular adrenal dysplasia (PPNAD) and the isolated micronodular adrenal hyperplasia (iMAD), can be distinguished from the primary bilateral macronodular adrenal hyperplasia (PBMAH) according to the size of the nodules. They both lead to overt or subclinical CS. In the latter case, PPNAD is usually diagnosed after a systematic screening in patients presenting with Carney complex, while for PBMAH, the diagnosis is often incidental on imaging. Identification of causal genes and genetic counseling also help in the diagnoses. This review discusses the last decades’ findings on genetic and molecular causes of bilateral adrenal hyperplasia, including the several mechanisms altering the PKA pathway, the recent discovery of ARMC5, and the role of the adrenal paracrine regulation. Finally, the treatment of bilateral adrenal hyperplasia will be discussed, focusing on current data on unilateral adrenalectomy.

Gαs-Protein Kinase A (PKA) Pathway Signalopathies: The Emerging Genetic Landscape and Therapeutic Potential of Human Diseases Driven by Aberrant Gαs-PKA Signaling

Many of the fundamental concepts of signal transduction and kinase activity are attributed to the discovery and crystallization of cAMP-dependent protein kinase, or protein kinase A. PKA is one of the best-studied kinases in human biology, with emphasis in biochemistry and biophysics, all the way to metabolism, hormone action, and gene expression regulation. It is surprising, however, that our understanding of PKA's role in disease is largely underappreciated. Although genetic mutations in the PKA holoenzyme are known to cause diseases such as Carney complex, Cushing syndrome, and acrodysostosis, the story largely stops there. With the recent explosion of genomic medicine, we can finally appreciate the broader role of the Gαs-PKA pathway in disease, with contributions from aberrant functioning G proteins and G protein-coupled receptors, as well as multiple alterations in other pathway components and negative regulators. Together, these represent a broad family of diseases we term the Gαs-PKA pathway signalopathies. The Gαs-PKA pathway signalopathies encompass diseases caused by germline, postzygotic, and somatic mutations in the Gαs-PKA pathway, with largely endocrine and neoplastic phenotypes. Here, we present a signaling-centric review of Gαs-PKA-driven pathophysiology and integrate computational and structural analysis to identify mutational themes commonly exploited by the Gαs-PKA pathway signalopathies. Major mutational themes include hotspot activating mutations in Gαs, encoded by GNAS, and mutations that destabilize the PKA holoenzyme. With this review, we hope to incite further study and ultimately the development of new therapeutic strategies in the treatment of a wide range of human diseases. SIGNIFICANCE STATEMENT: Little recognition is given to the causative role of Gαs-PKA pathway dysregulation in disease, with effects ranging from infectious disease, endocrine syndromes, and many cancers, yet these disparate diseases can all be understood by common genetic themes and biochemical signaling connections. By highlighting these common pathogenic mechanisms and bridging multiple disciplines, important progress can be made toward therapeutic advances in treating Gαs-PKA pathway-driven disease.

Primary Angiosarcoma of the Adrenal Gland: Report of 2 Cases and Review of the Literature

Primary adrenal angiosarcoma is a rare, malignant, vascular neoplasm. These neoplasms typically arise in middle age (median age of 60 years) and are more common in males (65%) than in females. Although rare, these neoplasms are aggressive with a propensity for local recurrence and metastasis and a median survival of 18 months. We present 2 cases of primary adrenal angiosarcoma with synchronous, ipsilateral adrenocortical adenomas. We review the cases of adrenal angiosarcoma reported since 1988 and discuss their clinical and histopathologic characteristics.

New Prognostic Indicators in Pediatric Adrenal Tumors: Neuroblastoma and Adrenal Cortical Tumors, Can We Predict When These Will Behave Badly?

Pediatric adrenal tumors are unique entities with specific diagnostic, prognostic, and therapeutic challenges. The adrenal medulla gives rise to peripheral neuroblastic tumors (pNTs), pathologically defined by their architecture, stromal content, degree of differentiation, and mitotic-karyorrhectic index. Successful risk stratification of pNTs uses patient age, stage, tumor histology, and molecular/genetic aberrations. The adrenal cortex gives rise to adrenocortical tumors (ACTs), which present diagnostic and prognostic challenges. Histologic features that signify poor prognosis in adults can be meaningless in children, who have superior outcomes. The key clinical, pathologic, and molecular findings of pediatric ACTs have yet to be completely identified.

ARMC5 variants in PRKAR1A-mutated patients modify cortisol levels and Cushing's syndrome

Mutations in the protein kinase A (PKA) regulatory subunit type 1A (PRKAR1A) and armadillo repeat-containing 5 (ARMC5) genes cause Cushing's syndrome (CS) due to primary pigmented nodular adrenocortical disease (PPNAD) and primary bilateral macronodular adrenocortical hyperplasia (PBMAH), respectively. Between the two genes, ARMC5 is highly polymorphic with several variants in the population, whereas PRKAR1A has very little, if any, non-pathogenic variation in its coding sequence. We tested the hypothesis that ARMC5 variants may affect the clinical presentation of PPNAD and CS among patients with PRKAR1A mutations. In this study, 91 patients with PPNAD due to PRKAR1A mutations were tested for abnormal cortisol secretion or CS and for ARMC5 sequence variants. Abnormal cortisol secretion was present in 71 of 74 patients with ARMC5 variants, whereas 11 of 17 patients negative for ARMC5 variants did not have hypercortisolemia. The presence of ARMC5 variants was a statistically strong predictor of CS among patients with PRKAR1A mutations (P < 0.001). Among patients with CS due to PPNAD, ARMC5 variants were associated with lower cortisol levels at baseline (P = 0.04) and after high dose dexamethasone administration (P = 0.02). The ARMC5 p.I170V variant increased ARMC5 protein accumulation in vitro and decreased viability of NCI-H295 cells (but not HEK 293T cells). PPNAD tissues with ARMC5 variants showed stronger ARMC5 protein expression than those that carried a normal ARMC5 sequence. Taken together, our results suggest that ARMC5 variants among patients with PPNAD due to PRKAR1A defects may play the role of a genetic modifier for the presence and severity of hypercortisolemia.

Update of Genetic and Molecular Causes of Adrenocortical Hyperplasias Causing Cushing Syndrome

Bilateral hyperplasias of the adrenal cortex are rare causes of chronic endogenous hypercortisolemia also called Cushing syndrome. These hyperplasias have been classified in two categories based on the adrenal nodule size: the micronodular types include Primary Pigmented Nodular Adrenocortical Disease (PPNAD) and isolated Micronodular Adrenal Disease (iMAD) and the macronodular also named Primary Bilateral Macronodular Adrenal Hyperplasia (PBMAH). This review discusses the genetic and molecular causes of these different forms of hyperplasia that involve mutations and dysregulation of various regulators of the cAMP/protein kinase A (PKA) pathway. PKA signaling is the main pathway controlling cortisol secretion in adrenocortical cells under ACTH stimulation. Although mutations of the regulatory subunit R1α of PKA (PRKAR1A) is the main cause of familial and sporadic PPNAD, inactivation of two cAMP-binding phosphodiesterases (PDE11A and PDE8B) are associated with iMAD even if they are also found in PPNAD and PBMAH cases. Interestingly, PBMAH that is observed in multiple familial syndrome such as APC, menin, fumarate hydratase genes, has initially been associated with the aberrant expression of G-protein coupled receptors (GPCR) leading to an activation of cAMP/PKA pathway. However, more recently, the discovery of germline mutations in Armadillo repeat containing protein 5 (ARMC5) gene in 25-50% of PBMAH patients highlights its importance in the development of PBMAH. The potential relationship between ARMC5 mutations and aberrant GPCR expression is discussed as well as the potential other causes of PBMAH.

Molecular Basis of Primary Aldosteronism and Adrenal Cushing Syndrome

This review reports the main molecular alterations leading to development of benign cortisol- and/or aldosterone-secreting adrenal tumors. Causes of adrenal Cushing syndrome can be divided in 2 groups: multiple bilateral tumors or adenomas secreting cortisol. Bilateral causes are mainly primary pigmented nodular adrenocortical disease, most of the time due to PRKAR1A germline-inactivating mutations, and primary bilateral macronodular adrenal hyperplasia that can be caused in some rare syndromic cases by germline-inactivating mutations of MEN1, APC, and FH and of ARMC5 in isolated forms. PRKACA somatic-activating mutations are the main alterations in unilateral cortisol-producing adenomas. In primary hyperaldosteronism (PA), familial forms were identified in 1% to 5% of cases: familial hyperaldosteronism type I (FH-I) due to a chimeric CYP11B1/CYP11B2 hybrid gene, FH-II due to CLCN-2 germline mutations, FH-III due to KCNJ5 germline mutations, FH-IV due to CACNA1H germline mutations and PA, and seizures and neurological abnormalities syndrome due to CACNA1D germline mutations. Several somatic mutations have been found in aldosterone-producing adenomas in KCNJ5, ATP1A1, ATP2B3, CACNA1D, and CTNNB1 genes.

In addition to these genetic alterations, genome-wide approaches identified several new alterations in transcriptome, methylome, and miRnome studies, highlighting new pathways involved in steroid dysregulation.

DNA Methylation Profiling Reveals Prognostically Significant Groups in Pediatric Adrenocortical Tumors: A Report From the International Pediatric Adrenocortical Tumor Registry

PURPOSE

Pediatric adrenocortical carcinomas (ACCs) are aggressive; the overall survival of patients with ACCs is 40%-50%. Appropriate staging and histologic classification are crucial because children with incomplete resections, metastases, or relapsed disease have a dismal prognosis. The clinical course of pediatric adrenocortical tumors (ACTs) is difficult to predict using the current classification schemas, which rely on subjective microscopic and gross macroscopic variables. Recent advances in adult ACT studies have revealed distinct DNA methylation patterns with prognostic significance that have not been systematically interrogated in the pediatric population.

PATIENTS AND METHODS

We performed DNA methylation analyses on 48 newly diagnosed ACTs from the International Pediatric Adrenocortical Tumor Registry and 12 pediatric adrenal controls to evaluate for distinct methylation groups. Pediatric methylation data were also compared systematically with the adult ACC cohort from The Cancer Genome Atlas (TCGA).

RESULTS

Two pediatric ACT methylation groups were identified and showed differences in selected clinicopathologic and outcome characteristics. The A1 group was enriched for CTNNB1 variants and unfavorable outcome. The A2 group was enriched for TP53 germline variants, younger age at onset, and favorable outcome. Pediatric ACT methylation groups were maintained when International Pediatric Adrenocortical Tumor Registry cohort data were combined with TCGA cohort data. The CpG-island hypermethylator phenotype characterizing the TCGA cohort was not identified in the pediatric patients. When methylome findings were combined with independent histopathologic review using the Wieneke criteria, a high-risk population was identified with uniform fatal outcome.

CONCLUSION

Our results indicate DNA methylation analysis can enhance current diagnostic algorithms. A combination of methylation and histologic classification produced the strongest prediction model and may prove useful in future risk-adapted therapeutic trials.

High expression of adrenal P450 aromatase (CYP19A1) in association with ARMC5-primary bilateral macronodular adrenocortical hyperplasia

Primary bilateral macronodular adrenocortical hyperplasia (PBMAH) is a rare cause of ACTH-independent Cushing syndrome (CS), which has been associated with ectopic G-protein coupled receptors (GPCRs) in the adrenal cortex. We recently studied a 51-year-old male with PBMAH who presented with severe CS and hyperestronemia, manifesting clinically with a Cushingoid appearance, gynecomastia, and telangiectasias. Analysis of adrenal tissues following bilateral adrenalectomy showed high expression of P450 aromatase (CYP19A1). The patient carried a germline non-sense pathogenic variant in ARMC5 (p.R173*), with two independent somatic pathogenic variants identified in the right (p.S571*) and left (p.Q235*) adrenal tissues, respectively. The expression of ARMC5 was drastically decreased in the hyperplastic regions when compared to either the adjacent non-hyperplastic regions and samples from PBMAH without pathogenic variants in ARMC5. We found expression of CYP19A1 in other cases of PBMAH, although there were no differences in aromatase expression between ARMC5-mutant and ARMC5-non-mutant cases. We conclude that in select cases, PBMAH can be associated with aromatase expression resulting in elevated estrogens, irrespective of sex. Additionally, CYP19A1 expression does not appear to depend on the ARMC5 variant status.

Genetics of micronodular adrenal hyperplasia and Carney complex

Micronodular bilateral adrenal hyperplasia (MiBAH) is a rare cause of adrenal Cushing syndrome (CS). The investigations carried out on this disorder during the last two decades suggested that it could be divided into at least two entities: primary pigmented nodular adrenocortical disease (PPNAD) and isolated micronodular adrenocortical disease (i-MAD). The most common presentation of MiBAH is familial PPNAD as part of Carney complex (CNC) (cPPNAD). CNC, associated with multiple endocrine and non-endocrine neoplasias, was first described in 1985 in 40 patients, 10 of whom were familial cases. In 2000, we identified inactivating germline mutations of the PRKAR1A gene, encoding the regulatory subunit type 1α (RIα) of protein kinase A (PKA), in the majority of patients with CNC and PPNAD. PRKAR1A mutations causing CNC lead to increased PKA activity. Since then, additional genetic alterations in the cAMP/PKA signaling pathway leading to increased PKA activity have been described in association with MiBAH. This review summarizes older and recent findings on the genetics and pathophysiology of MiBAH, PPNAD, and related disorders.

Genetics of tumors of the adrenal cortex

This review describes the molecular alterations observed in the various types of tumors of the adrenal cortex, excluding Conn adenomas, especially the alterations identified by genomic approaches these last five years. Two main forms of bilateral adrenocortical tumors can be distinguished according to size and aspect of the nodules: primary pigmented nodular adrenal disease (PPNAD), which can be sporadic or part of Carney complex and primary bilateral macro nodular adrenal hyperplasia (PBMAH). The bilateral nature of the tumors suggests the existence of an underlying genetic predisposition. PPNAD and Carney complex are mainly due to germline-inactivating mutations of PRKAR1A, coding for a regulatory subunit of PKA, whereas PBMAH genetic seems more complex. However, genome-wide approaches allowed the identification of a new tumor suppressor gene, ARMC5, whose germline alteration could be responsible for at least 25% of PBMAH cases. Unilateral adrenocortical tumors are more frequent, mostly adenomas. The Wnt/beta-catenin pathway can be activated in both benign and malignant tumors by CTNNB1 mutations and by ZNRF3 inactivation in adrenal cancer (ACC). Some other signaling pathways are more specific of the tumor dignity. Thus, somatic mutations of cAMP/PKA pathway genes, mainly PRKACA, coding for the catalytic alpha-subunit of PKA, are found in cortisol-secreting adenomas, whereas IGF-II overexpression and alterations of p53 signaling pathway are observed in ACC. Genome-wide approaches including transcriptome, SNP, methylome and miRome analysis have identified new genetic and epigenetic alterations and the further clustering of ACC in subgroups associated with different prognosis, allowing the development of new prognosis markers.

Genetics of Adrenocortical Development and Tumors

This article links the understanding of developmental physiology of the adrenal cortex to adrenocortical tumor formation. Many molecular mechanisms that lead to formation of adrenocortical tumors have been discovered via next-generation sequencing approaches. The most frequently mutated genes in adrenocortical tumors are also factors in normal adrenal development and homeostasis, including those that alter the p53 and Wnt/β-catenin pathways. In addition, dysregulated protein kinase A signaling and ARMC5 mutations have been identified as key mediators of adrenocortical tumorigenesis. The growing understanding of genetic changes that orchestrate adrenocortical development and disease pave the way for potential targeted treatment strategies.

Cell signaling pathways in the adrenal cortex: Links to stem/progenitor biology and neoplasia

The adrenal cortex is a dynamic tissue responsible for the synthesis of steroid hormones, including mineralocorticoids, glucocorticoids, and androgens in humans. Advances have been made in understanding the role of adrenocortical stem/progenitor cell populations in cortex homeostasis and self-renewal. Recently, large molecular profiling studies of adrenocortical carcinoma (ACC) have given insights into proteins and signaling pathways involved in normal tissue homeostasis that become dysregulated in cancer. These data provide an impetus to examine the cellular pathways implicated in adrenocortical disease and study connections, or lack thereof, between adrenal homeostasis and tumorigenesis, with a particular focus on stem and progenitor cell pathways. In this review, we discuss evidence for stem/progenitor cells in the adrenal cortex, proteins and signaling pathways that may regulate these cells, and the role these proteins play in pathologic and neoplastic conditions. In turn, we also examine common perturbations in adrenocortical tumors (ACT) and how these proteins and pathways may be involved in adrenal homeostasis.

Celecoxib treatment of fibrous dysplasia (FD) in a human FD cell line and FD-like lesions in mice with protein kinase A (PKA) defects

Osteochondromyxomas (OMX) in the context of Carney complex (CNC) and fibrous dysplasia (FD)-like lesions (FDLL) in mice, as well as isolated myxomas in humans may be caused by inactivation of PRKAR1A, the gene coding for the type 1a regulatory subunit (R1α) of cAMP-dependent protein kinase (PKA). OMXs and FDLL in mice lacking Prkar1a grow from abnormal proliferation of adult bone stromal cells (aBSCs). Prkar1a and Prkaca (coding for Cα) haploinsufficiency leads to COX2 activation and prostaglandin E2 (PGE2) production that, in turn, activates proliferation of aBSCs. Celecoxib is a cyclooxygenase-2 (COX2) inhibitor. We hypothesized that COX-2 inhibition may have an effect in FD and FDLL. In vitro treatment of a human cell line prepared from a FD patient with Celecoxib resulted in decreased PGE2 and cell proliferation. Treatment of mice haploinsufficient for R1α and Cα with 1500 mg/kg Celecoxib led to decreased PGE2 and proliferation and increased apoptosis, with a corresponding gene expression profile, resulting in dramatic reduction of tumor growth. Furthermore, the treatment improved the organization of cortical bone that was adjacent to the tumor. We conclude that, in vitro and in vivo, Celecoxib had an inhibitory effect on FD cell proliferation and in mouse FDLL structure, respectively. We speculate that COX-2 inhibitors offer an attractive alternative to current treatments for benign tumors such as OMX and FD that, apart from tumor suppression, may mechanically stabilize affected bones.

PKA inhibits WNT signalling in adrenal cortex zonation and prevents malignant tumour development

Adrenal cortex physiology relies on functional zonation, essential for production of aldosterone by outer zona glomerulosa (ZG) and glucocorticoids by inner zona fasciculata (ZF). The cortex undergoes constant cell renewal, involving recruitment of subcapsular progenitors to ZG fate and subsequent lineage conversion to ZF identity. Here we show that WNT4 is an important driver of WNT pathway activation and subsequent ZG differentiation and demonstrate that PKA activation prevents ZG differentiation through WNT4 repression and WNT pathway inhibition. This suggests that PKA activation in ZF is a key driver of WNT inhibition and lineage conversion. Furthermore, we provide evidence that constitutive PKA activation inhibits, whereas partial inactivation of PKA catalytic activity stimulates β-catenin-induced tumorigenesis. Together, both lower PKA activity and higher WNT pathway activity lead to poorer prognosis in adrenocortical carcinoma (ACC) patients. These observations suggest that PKA acts as a tumour suppressor in the adrenal cortex, through repression of WNT signalling.

The adrenal cortex undergoes functional zonation to generate an outer zona glomerulosa (ZG) and inner zona fasciculata (ZF), but how this is regulated at a molecular level is unclear. Here, the authors show that ZG differentiation is stimulated by WNT signalling and that PKA blocks WNT signalling to allow ZF differentiation and also prevents WNT-induced cancer development.

A genetic and molecular update on adrenocortical causes of Cushing syndrome

Primary adrenal Cushing syndrome is the result of cortisol hypersecretion mainly by adenomas and, rarely, by bilateral micronodular or macronodular adrenocortical hyperplasia. cAMP-dependent protein kinase A (PKA) signalling is the major activator of cortisol secretion in the adrenal cortex. Many adenomas and hyperplasias associated with primary hypercortisolism carry somatic or germline mutations in genes that encode constituents of the cAMP-PKA pathway. In this Review, we discuss Cushing syndrome and its linkage to dysregulated cAMP-PKA signalling, with a focus on genetic findings in the past few years. In addition, we discuss the presence of germline inactivating mutations in ARMC5 in patients with primary bilateral macronodular adrenocortical hyperplasia. This finding has implications for genetic counselling of affected patients; hitherto, most patients with this form of adrenal hyperplasia and Cushing syndrome were thought to have a sporadic and not a familial disorder.

The Role of gsp Mutations on the Development of Adrenocortical Tumors and Adrenal Hyperplasia

Somatic GNAS point mutations, commonly known as gsp mutations, are involved in the pathogenesis of McCune-Albright syndrome (MAS) and have also been described in autonomous hormone-producing tumors, such as somatotropinoma, corticotrophoma, thyroid cancer, ovarian and testicular Leydig cell tumors, and primary macronodular adrenocortical hyperplasia (PMAH) (1-3). The involvement of gsp mutations in adrenal tumors was first described by Lyons et al. Since then, several studies have detected the presence of gsp mutations in adrenal tumors, but none of them could explain its presence along or the mechanism that leads to tumor formation and hormone hypersecretion. As a result, the molecular pathogenesis of the majority of sporadic adrenocortical tumors remains unclear (3). PMAH has also been reported with gsp somatic mutations in a few cases. Fragoso et al. identified two distinct gsp somatic mutations affecting arginine residues on codon 201 of GNAS in a few patients with PMAH who lacked any features or manifestations of MAS. Followed by this discovery, other studies have continued looking for gsp mutations based on strong prior evidence demonstrating that increased cAMP signaling is sufficient for cell proliferation and cortisol production (2, 4). With consideration for the previously reported findings, we conjecture that although somatic activating mutations in GNAS are a rare molecular event, these mutations could probably be sufficient to induce the development of macronodule hyperplasia and variable cortisol secretion. In this manuscript, we revised the presence of gsp mutations associated with adrenal cortical tumors and hyperplasia.

C-Jun NH2-Terminal Kinase and p38 Inhibition Suppresses Prostaglandin E2-Stimulated Aromatase and Estrogen Receptor Levels in Human Endometriosis

CONTEXT

Endometriosis is an estrogen-dependent disease. P38 and C-jun NH2-terminal kinase (JNK) inhibitors may have a therapeutic effect on endometriosis through regulation of prostaglandin E2 (PGE2)-induced estrogen metabolism.

OBJECTIVE

The objective of this study was to determine whether the activated MAPKs signaling pathway observed in human ectopic endometrial stromal cells (ESCs) from ovarian endometriomas influences levels of aromatase and estrogen receptor β (ERβ) protein regulated by PGE2. In turn, the effects of inhibiting MAPKs in the presence of PGE2 on estrogen production were investigated in vitro and in vivo.

RESULTS

Expression of aromatase and ERβ regulated by PGE2 were much higher in ESCs than eutopic ESCs from the same person. Activation of p38, JNK, ERK 1/2 and ERK 5 MAPKs by PGE2 were observed in ESCs, where PGE2-stimulated aromatase and ERβ expression mainly through p38 and JNK pathway. P38 and JNK inhibition or small interfering RNA knockdown blocked PGE2-induced aromatase and ERβ expression. PGE2 enhanced binding of downstream p38 and JNK transcription factors activating transcription factor-2 and c-Jun to aromatase and ERB promoter regions in ESCs. Moreover, treatment of endometriosis xenografts with inhibitors of p38 and JNK abrogated PGE2-amplified estradiol synthesis and xenograft growth.

CONCLUSIONS

PGE2 activates p38 and JNK signaling pathways, further stimulating c-Jun and activating transcription factor-2 binding to aromatase and ERB promoter regions with elevated estradiol production. Inhibition of JNK and P38 may be a potential method of treating human endometriosis.

Cholesterol Biosynthesis and Trafficking in Cortisol-Producing Lesions of the Adrenal Cortex

CONTEXT

Cortisol-producing adenomas (CPAs), primary pigmented nodular adrenocortical disease (PPNAD), and primary macronodular adrenocortical hyperplasia (PMAH) cause ACTH-independent Cushing syndrome (CS). Investigation of their pathogenesis has demonstrated their integral link to the cAMP-dependent protein kinase signaling pathway.

OBJECTIVE

The aim of this study was to identify differences in cholesterol biosynthesis among different CS-causing adrenocortical tumors. Because of the concomitant associations of cAMP levels with cholesterol and with steroid biosynthesis, we hypothesized that benign cortisol-producing tumors would display aberration of these pathways.

DESIGN AND SETTING

Twenty-three patients with CPA, PPNAD, or PMAH who underwent adrenalectomy for CS were included in the study. Preoperative biochemical analyses were performed, and excised adrenal tissues were studied.

MAIN OUTCOME MEASURES

Serum, urinary hormone levels, serum lipid profiles, and anthropometric data were obtained preoperatively. Adrenal tissues were analyzed for total protein, cholesterol, and neutral sterol content by mass spectrometry and expression of HMGCR, LDLR, ABCA1, DHCR24, and STAR genes.

RESULTS

There were differences in cholesterol content and markers of cholesterol biosynthesis and metabolism that distinguished CPAs from PMAH and PPNAD; cholesterol, lathosterol, and lathosterol/cholesterol ratio were significantly higher in CPAs. ABCA1 mRNA was lower among CPAs compared to tissues from bilateral adrenocortical hyperplasia (PMAH and PPNAD), and mRNA expression of LDL-R, DCHR24, and HMGCR tended to be higher in CPA tumor tissues.

CONCLUSION

CPAs displayed characteristics of "cholesterol-starved" tissues when compared to PPNAD and PMAH and appeared to have increased intrinsic cholesterol production and uptake from the periphery, as well as decreased cholesterol efflux. This has implications for a potential new way of treating these tumors.

Genetics of primary bilateral macronodular adrenal hyperplasia: a model for early diagnosis of Cushing's syndrome?

Long-term consequences of cortisol excess are frequent despite appropriate treatment after cure of Cushing's syndrome. This might be due to diagnostic delay, often difficult to reduce in rare diseases. The identification of a genetic predisposing factor might help to improve early diagnosis by familial screening. Primary bilateral macronodular adrenal hyperplasia (PBMAH) is a rare cause of Cushing's syndrome. Hypercortisolism in PBMAH is most often diagnosed between the fifth and sixth decades of life. The bilateral nature of the adrenocortical tumors and the occurrence of rare clear familial forms suggest a genetic origin. Indeed, a limited subset of PBMAH can be observed as part of multiple tumors syndromes due to alterations of the APC, Menin or Fumarate Hydratase genes. Rare variants of the phosphodiesterases PDE11A have been associated with PBMAH. The recent identification of ARMC5 germline alterations in 25-50% of PBMAH patients without obvious familial history or associated tumors opens new perspectives. ARMC5 alterations follow the model of a tumor suppressor gene: a first germline inactivating mutation of this 16p located gene is followed by a somatic secondary hit on the other allele (inactivating mutation or allelic loss). Functional studies demonstrate that ARMC5 controls apoptosis and steroid synthesis. The phenotype of index cases patients with the mutation seems more severe than the one of WT index cases. However, phenotype variability within a family is often observed. This review summarizes the genetics of PBMAH, focusing on ARMC5, which offer new perspectives for early diagnosis of Cushing's syndrome.

Phosphodiesterase 8B and cyclic AMP signaling in the adrenal cortex

Bilateral adrenocortical hyperplasia (BAH) in humans and mice has been recently linked to phosphodiesterase (PDE) 8B (PDE8B) and 11 (PDE11A) defects. These findings have followed the discovery that defects of primary genes of the cyclic monophosphatase (cAMP) signaling pathway, such as guanine nucleotide binding alpha subunit and PRKAR1A, are involved in the pathogenesis of BAH in humans; complete absence of Prkar1a in the adrenal cortex of mice also led to pathology that mimicked the human disease. Here, we review the most recent findings in human and mouse studies on PDE8B, a cAMP-specific PDE that appears to be highly expressed in the adrenal cortex and whose deficiency may underlie predisposition to BAH and possibly other human diseases.

Phosphodiesterase sequence variants may predispose to prostate cancer

We hypothesized that mutations that inactivate phosphodiesterase (PDE) activity and lead to increased cAMP and cyclic guanosine monophosphate levels may be associated with prostate cancer (PCa). We sequenced the entire PDE coding sequences in the DNA of 16 biopsy samples from PCa patients. Novel mutations were confirmed in the somatic or germline state by Sanger sequencing. Data were then compared to the 1000 Genome Project. PDE, CREB and pCREB protein expression was also studied in all samples, in both normal and abnormal tissue, by immunofluorescence. We identified three previously described PDE sequence variants that were significantly more frequent in PCa. Four novel sequence variations, one each in the PDE4B,PDE6C, PDE7B and PDE10A genes, respectively, were also found in the PCa samples. Interestingly, PDE10A and PDE4B novel variants that were present in 19 and 6% of the patients were found in the tumor tissue only. In patients carrying PDE defects, there was pCREB accumulation (P<0.001), and an increase of the pCREB:CREB ratio (patients 0.97±0.03; controls 0.52±0.03; P-value <0.001) by immunohistochemical analysis. We conclude that PDE sequence variants may play a role in the predisposition and/or progression to PCa at the germline and/or somatic state respectively.

Adrenal cortex tissue homeostasis and zonation: A WNT perspective

The adrenal cortex plays essential roles in the control of sodium and water homeostasis, stress response, inflammation and metabolism, through secretion of glucocorticoids and mineralocorticoids. Coordinated production of these hormones relies on functional zonation of the cortex, characterised by expression of Cyp11b2 under the control of angiotensin II and plasma potassium level in zona glomerulosa (ZG) and Cyp11b1 under the control of ACTH in zona fasciculata (ZF). The mechanisms involved in the establishment of functional zonation and its maintenance during centripetal cortex cell renewal are still poorly understood. Here, we hypothesise that the hormonal and signalling pathways that control adrenal cortex function are also involved in cortical zonation. In particular, we summarise evidence on the role of WNT/β-catenin signalling in ZG differentiation and how tight control of its activity is required to shape the adult cortex. In this context, we discuss the potential role of known WNT regulators and the possibility of a reciprocal cross-talk between PKA and WNT signalling.

The genetics of adrenocortical tumors

Advances in genomics accelerated greatly progress in the study of the genetics adrenocortical tumors. Bilateral nodular hyperplasias causing Cushing's syndrome are frequently caused by germline alterations leading to cAMP/PKA pathway activation (micronodular) and ARMC5 inactivation (macronodular). Somatic mutations of β-catenin and PRKACA are observed in non secreting or cortisol producing adenomas, respectively. Alterations of the β-catenin (CTNN1B, ZNFR3) or TP53 pathways are found in carcinomas. Mutations in cancers are more common in aggressive tumors and correlate with transcriptome or methylation profiles. Identification of these alterations helps to refine the molecular classification of these tumors and to develop molecular diagnostic tools.

[New aspects of tumor pathology of the adrenal glands]

In daily routine pathology of the adrenal glands three tumor entities are important: adrenocortical tumors, adrenomedullary tumors and metastases. The differentiation of these three main tumor types can often be difficult structurally but immunostaining enables a definite diagnosis in nearly all cases. Adrenocortical tumors are positive for steroidogenic factor 1 and melan-A and always negative for chromogranin A whereas adrenomedullary tumors express chromogranin A but never keratin. A broad spectrum of antibodies is available for the identification of metastases and even the rare epithelioid angiosarcomas. For adrenocortical tumors, adenomas and carcinomas can be differentiated using three scoring systems and the Ki-67 index in adenomas should not exceed 3%. Using scoring systems and the Ki-67 index approximately 90% of cortical tumors can be differentiated into benign or malignant tumors. For pheochromocytomas two scoring systems are used for differentiating benign and malignant tumors but the results are less dependable.

A pathological perspective on the natural history of cerebral atherosclerosis

BACKGROUND

The natural history of intracranial large artery atherosclerosis has been mainly described from lumen-based imaging studies, and much of what is reported to be known about atherosclerosis is derived from non-cerebral arteries.

AIMS

To test the hypothesis that atherosclerosis is only partially represented by stenosis and that advanced atherosclerosis is more common that severe stenosis in noncardioembolic infarcts.

METHODS

Cerebral large arteries from 196 autopsy cases were studied. The revised American Heart Association classification for atherosclerosis was used to determine the phenotype in each available artery. Cross-sectional lumen stenosis was obtained as defined by the Glagov's method.

RESULTS

As age of cases increased, there was a progressive increment in the frequency of atherosclerotic lesions, rising from 5% of all arteries at age 20-40, to more than 40% at age 60 or older. Stenosis also increased with age: less than 3% of the arteries in those ≤50 years had >40% stenosis, while one out of five arteries in those >80 years had >40% stenosis. In most cases (80%), atherosclerosis and stenosis were directly related. However, one out of five cases with advanced atherosclerosis had <30% stenosis. In arteries supplying brain areas with noncardioembolic infarcts, the majority of segments exhibiting advanced atherosclerosis had lumen stenosis of <40%.

CONCLUSION

Although intracranial atherosclerosis is typically associated with stenosis, a substantial minority of cases shows advanced atherosclerosis in the absence of stenosis >40%. Definitions based solely on stenosis may underestimate the extent and role of intracranial large artery atherosclerosis.

Whole-exome sequencing characterizes the landscape of somatic mutations and copy number alterations in adrenocortical carcinoma

CONTEXT

Adrenocortical carcinoma (ACC) is a rare and lethal malignancy with a poorly defined etiology, and the molecular genetics of ACC are incompletely understood.

OBJECTIVE

To utilize whole-exome sequencing for genetic characterization of the underlying somatic mutations and copy number alterations present in ACC.

DESIGN

Screening for somatic mutation events and copy number alterations (CNAs) was performed by comparative analysis of tumors and matched normal samples from 41 patients with ACC.

RESULTS

In total, 966 nonsynonymous somatic mutations were detected, including 40 tumors with a mean of 16 mutations per sample and one tumor with 314 mutations. Somatic mutations in ACC-associated genes included TP53 (8/41 tumors, 19.5%) and CTNNB1 (4/41, 9.8%). Genes with potential disease-causing mutations included GNAS, NF2, and RB1, and recurrently mutated genes with unknown roles in tumorigenesis comprised CDC27, SCN7A, and SDK1. Recurrent CNAs included amplification at 5p15.33 including TERT (6/41, 14.6%) and homozygous deletion at 22q12.1 including the Wnt repressors ZNRF3 and KREMEN1 (4/41 9.8% and 3/41, 7.3%, respectively). Somatic mutations in ACC-established genes and recurrent ZNRF3 and TERT loci CNAs were mutually exclusive in the majority of cases. Moreover, gene ontology identified Wnt signaling as the most frequently mutated pathway in ACCs.

CONCLUSIONS

These findings highlight the importance of Wnt pathway dysregulation in ACC and corroborate the finding of homozygous deletion of Wnt repressors ZNRF3 and KREMEN1. Overall, mutations in either TP53 or CTNNB1 as well as focal CNAs at the ZNRF3 or TERT loci denote mutually exclusive events, suggesting separate mechanisms underlying the development of these tumors.

Cushing's syndrome in childhood: update on genetics, treatment, and outcomes

PURPOSE OF REVIEW

To provide an update on the genes associated with Cushing's syndrome in children, as well as to familiarize the clinician with recent treatment guidelines and outcome data for children with Cushing's syndrome.

RECENT FINDINGS

The list of genes associated with Cushing's syndrome continues to grow. In addition, treatment for childhood Cushing's syndrome is evolving. As long-term follow-up data on children becomes available, clinicians need to be aware of the issues that require attention.

SUMMARY

Knowledge of the specific genetic causes of Cushing's syndrome has potential implications for treatment, surveillance, and counseling. Advances in surgical technique, radiation modalities, and medical therapies offer the potential for additional treatment options in Cushing's syndrome. Early identification and management of post-treatment morbidities in children treated for Cushing's syndrome is crucial in order to optimize care.

Genetics of primary macronodular adrenal hyperplasia

ACTH-independent macronodular adrenal hyperplasia is a rare cause of Cushing's syndrome (CS), accounting for <2% of all endogenous CS cases; however it is more frequently identified incidentally with sub-clinical cortisol secretion. Recently, cortisol secretion has been shown to be regulated by ectopic corticotropin, which is in turn produced by clusters of steroidogenic cells of the hyperplastic adrenal nodules. Hence, the term 'ACTH-independent' is not entirely appropriate for this disorder. Accordingly, the disease is designated primary macronodular adrenal hyperplasia (PMAH) in this review article. The means by which cortisol production is regulated in PMAH despite the suppressed levels of ACTH of pituitary origin is exceedingly complex. Several molecular events have been proposed to explain the enhanced cortisol secretion, increased cell proliferation, and nodule formation in PMAH. Nonetheless, the precise sequence of events and the molecular mechanisms underlying this condition remain unclear. The purpose of this review is therefore to present new insights on the molecular and genetic profile of PMAH pathophysiology, and to discuss the implications for disease progression.

Regulation of the adrenocortical stem cell niche: implications for disease

Stem cells are endowed with the potential for self-renewal and multipotency. Pluripotent embryonic stem cells have an early role in the formation of the three germ layers (ectoderm, mesoderm and endoderm), whereas adult tissue stem cells and progenitor cells are critical mediators of organ homeostasis. The adrenal cortex is an exceptionally dynamic endocrine organ that is homeostatically maintained by paracrine and endocrine signals throughout postnatal life. In the past decade, much has been learned about the stem and progenitor cells of the adrenal cortex and the multiple roles that these cell populations have in normal development and homeostasis of the adrenal gland and in adrenal diseases. In this Review, we discuss the evidence for the presence of adrenocortical stem cells, as well as the various signalling molecules and transcriptional networks that are critical for the embryological establishment and postnatal maintenance of this vital population of cells. The implications of these pathways and cells in the pathophysiology of disease are also addressed.

Macronodular adrenal hyperplasia due to mutations in an armadillo repeat containing 5 (ARMC5) gene: a clinical and genetic investigation

CONTEXT

Inactivating germline mutations of the probable tumor suppressor gene, armadillo repeat containing 5 (ARMC5), have recently been identified as a genetic cause of macronodular adrenal hyperplasia (MAH).

OBJECTIVE

We searched for ARMC5 mutations in a large cohort of patients with MAH. The clinical phenotype of patients with and without ARMC5 mutations was compared.

METHODS

Blood DNA from 34 MAH patients was genotyped using Sanger sequencing. Diurnal serum cortisol measurements, plasma ACTH levels, urinary steroids, 6-day Liddle's test, adrenal computed tomography, and weight of adrenal glands at adrenalectomy were assessed.

RESULTS

Germline ARMC5 mutations were found in 15 of 34 patients (44.1%). In silico analysis of the mutations indicated that seven (20.6%) predicted major implications for gene function. Late-night cortisol levels were higher in patients with ARMC5-damaging mutations compared with those without and/or with nonpathogenic mutations (14.5 ± 5.6 vs 6.7 ± 4.3, P < .001). All patients carrying a pathogenic ARMC5 mutation had clinical Cushing's syndrome (seven of seven, 100%) compared with 14 of 27 (52%) of those without or with mutations that were predicted to be benign (P = .029). Repeated-measures analysis showed overall higher urinary 17-hydroxycorticosteroids and free cortisol values in the patients with ARMC5-damaging mutations during the 6-day Liddle's test (P = .0002).

CONCLUSIONS

ARMC5 mutations are implicated in clinically severe Cushing's syndrome associated with MAH. Knowledge of a patient's ARMC5 status has important clinical implications for the diagnosis of Cushing's syndrome and genetic counseling of patients and their families.

Primary bilateral macronodular adrenal hyperplasia

PURPOSE OF REVIEW

Primary bilateral macronodular adrenal hyperplasia is a rare cause of Cushing's syndrome and is more often diagnosed as bilateral adrenal incidentalomas with subclinical cortisol production. We summarize the recent insights concerning its epidemiology, diagnosis, genetics, pathophysiology, and therapeutic options.

RECENT FINDINGS

Recent publications have modified our notions on the genetics and pathophysiology of bilateral macronodular adrenal hyperplasia. Combined germline and somatic mutations of armadillo repeat containing 5 gene were identified in familial cases, in approximately 50% of apparently sporadic cases and in the relatives of index cases; genetic testing should allow early diagnosis in the near future. The recent finding of ectopic adrenocortical production of adrenocorticotropic hormone in clusters of bilateral macronodular adrenal hyperplasia tissues and its regulation by aberrant hormone receptors opens new horizons for eventual medical therapy using melanocortin-2 receptor and G-protein-coupled receptor antagonists. Finally, some medical and surgical treatments have been updated.

SUMMARY

Recent findings indicate that bilateral macronodular adrenal hyperplasia is more frequently genetically determined than previously believed. Considering the role of paracrine adrenocorticotropic hormone production on cortisol secretion, the previous nomenclature of adrenocorticotropic hormone-independent macronodular adrenal hyperplasia appears inappropriate, and this disease should now be named primary bilateral macronodular adrenal hyperplasia.

Analysis of GNAS1 mutations in myxoid soft tissue and bone tumors

The aim of this study was to characterize the prevalence of GNAS1 mutations in various tumor types, including intramuscular myxomas, fibrous dysplasias, and other myxoid tumors and implications for malignant transformation. PCR and direct sequencing were applied to analyze GNAS1 mutation status using genomic DNA isolated from 97 formalin-fixed and paraffin-embedded samples, including 63 intramuscular myxomas, 19 various myxoid lesions, 8 cases of sporadically occurring fibrous dysplasia, and 7 cases of atrial myxoma. Mutations of GNAS1 were detected in 23 out of 63 (36.5%) intramuscular myxoma patients, with mutational hotspots R201H and R201C being equally affected. GNAS1 mutations in codon 201 were found in 5 out of 8 fibrous dysplasias (62.5%), while no mutations of GNAS1 were detected in the other studied entities, including atrial myxomas. GNAS1 mutation analysis has diagnostic value in screening patients with intramuscular myxoma and patients with fibrous dysplasia.

cAMP/PKA signaling defects in tumors: genetics and tissue-specific pluripotential cell-derived lesions in human and mouse

In the last few years, bench and clinical studies led to significant new insight into how cyclic adenosine monophosphate (cAMP) signaling, the molecular pathway that had been identified in the early 2000s as the one involved in most benign cortisol-producing adrenal hyperplasias, affects adrenocortical growth and development, as well as tumor formation. A major discovery was the identification of tissue-specific pluripotential cells (TSPCs) as the culprit behind tumor formation not only in the adrenal, but also in bone. Discoveries in animal studies complemented a number of clinical observations in patients. Gene identification continued in parallel with mouse and other studies on the cAMP signaling and other pathways.