Mechanisms of Disease: adrenocortical tumors—molecular advances and clinical perspectives

Mosaic PRKACA duplication causing a novel and distinct phenotype of early-onset Cushing's syndrome and acral cutaneous mucinosis

SIGNIFICANCE STATEMENT

We describe a mosaic PRKACA duplication in a young infant who presented with a Carney-like complex: bilateral non-pigmented micronodular adrenal hyperplasia, severe early-onset Cushing's syndrome, and distinct acral soft tissue overgrowth due to cutaneous mucinosis. This represents a novel manifestation of PRKACA disruption and broadens the extra-adrenal phenotype of PRKACA-associated Cushing's syndrome. Our data suggest that Cushing's syndrome phenotypes arising from somatic and germline PRKACA abnormalities can exist on a spectrum. We emphasise the value of ascertaining a genetic diagnosis for PRKACA-mediated adrenal and extra-adrenal disease to guide individualised and targeted care.

Challenges in surgical pathology of adrenocortical tumours

Adrenocortical carcinomas are rare tumours that can be diagnostically challenging. Numerous multiparametric scoring systems and diagnostic algorithms have been proposed to differentiate adrenocortical adenoma from adrenocortical carcinoma. Adrenocortical neoplasms must also be differentiated from other primary adrenal tumours, such as phaeochromocytoma and unusual primary adrenal tumours, as well as metastases to the adrenal gland. Myxoid, oncocytic and sarcomatoid variants of adrenocortical tumours must be recognized so that they are not confused with other tumours. The diagnostic criteria for oncocytic adrenocortical carcinoma are different from those for conventional adrenocortical carcinomas. Adrenocortical neoplasms in children are particularly challenging to diagnose, as histological features of malignancy in adrenocortical neoplasms in adults may not be associated with aggressive disease in the tumours of children. Recent histological and immunohistochemical studies and more comprehensive and integrated genomic characterizations continue to advance our understanding of the tumorigenesis of these aggressive neoplasms, and may provide additional diagnostic and prognostic utility and guide the development of therapeutic targets.

cAMP signaling in cortisol-producing adrenal adenoma

The cAMP signaling pathway is one of the major players in the regulation of growth and hormonal secretion in adrenocortical cells. Although its role in the pathogenesis of adrenocortical hyperplasia associated with Cushing's syndrome has been clarified, a clear involvement of the cAMP signaling pathway and of one of its major downstream effectors, the protein kinase A (PKA), in sporadic adrenocortical adenomas remained elusive until recently. During the last year, a report by our group and three additional independent groups showed that somatic mutations of PRKACA, the gene coding for the catalytic subunit α of PKA, are a common genetic alteration in patients with Cushing's syndrome due to adrenal adenomas, occurring in 35-65% of the patients. In vitro studies revealed that those mutations are able to disrupt the association between catalytic and regulatory subunits of PKA, leading to a cAMP-independent activity of the enzyme. Despite somatic PRKACA mutations being a common finding in patients with clinically manifest Cushing's syndrome, the pathogenesis of adrenocortical adenomas associated with subclinical hypercortisolism seems to rely on a different molecular background. In this review, the role of cAMP/PKA signaling in the regulation of adrenocortical cell function and its alterations in cortisol-producing adrenocortical adenomas will be summarized, with particular focus on recent developments.

Clinical and functional impact of TARBP2 over-expression in adrenocortical carcinoma

Deregulation of microRNA (miRNA) expression in adrenocortical carcinomas (ACCs) has been documented to have diagnostic, prognostic, as well as functional implications. Here, we evaluated the mRNA expression of DROSHA, DGCR8, DICER (DICER1), TARBP2, and PRKRA, the core components in the miRNA biogenesis pathway, in a cohort of 73 adrenocortical tumors (including 43 adenomas and 30 carcinomas) and nine normal adrenal cortices using a RT-qPCR approach. Our results show a significant over-expression of TARBP2, DICER, and DROSHA in the carcinomas compared with adenomas or adrenal cortices (P<0.001 for all comparisons). Using western blot and immunohistochemistry analyses, we confirmed the higher expression of TARBP2, DICER, and DROSHA at the protein level in carcinoma cases. Furthermore, we demonstrate that mRNA expression of TARBP2, but not DICER or DROSHA, is a strong molecular predictor to discriminate between adenomas and carcinomas. Functionally, we showed that inhibition of TARBP2 expression in human NCI-H295R ACC cells resulted in a decreased cell proliferation and induction of apoptosis. TARBP2 over-expression was not related to gene mutations; however, copy number gain of the TARBP2 gene was observed in 57% of the carcinomas analyzed. In addition, we identified that miR-195 and miR-497 could directly regulate TARBP2 and DICER expression in ACC cells. This is the first study to demonstrate the deregulation of miRNA-processing factors in adrenocortical tumors and to show the clinical and biological impact of TARBP2 over-expression in this tumor type.

Progression to adrenocortical tumorigenesis in mice and humans through insulin-like growth factor 2 and β-catenin

Dysregulation of the WNT and insulin-like growth factor 2 (IGF2) signaling pathways has been implicated in sporadic and syndromic forms of adrenocortical carcinoma (ACC). Abnormal β-catenin staining and CTNNB1 mutations are reported to be common in both adrenocortical adenoma and ACC, whereas elevated IGF2 expression is associated primarily with ACC. To better understand the contribution of these pathways in the tumorigenesis of ACC, we examined clinicopathological and molecular data and used mouse models. Evaluation of adrenal tumors from 118 adult patients demonstrated an increase in CTNNB1 mutations and abnormal β-catenin accumulation in both adrenocortical adenoma and ACC. In ACC, these features were adversely associated with survival. Mice with stabilized β-catenin exhibited a temporal progression of increased adrenocortical hyperplasia, with subsequent microscopic and macroscopic adenoma formation. Elevated Igf2 expression alone did not cause hyperplasia. With the combination of stabilized β-catenin and elevated Igf2 expression, adrenal glands were larger, displayed earlier onset of hyperplasia, and developed more frequent macroscopic adenomas (as well as one carcinoma). Our results are consistent with a model in which dysregulation of one pathway may result in adrenal hyperplasia, but accumulation of a second or multiple alterations is necessary for tumorigenesis.

The role of microRNA deregulation in the pathogenesis of adrenocortical carcinoma

Adrenocortical carcinoma (ACC) is an aggressive tumor showing frequent metastatic spread and poor survival. Although recent genome-wide studies of ACC have contributed to our understanding of the disease, major challenges remain for both diagnostic and prognostic assessments. The aim of this study was to identify specific microRNAs (miRNAs) associated with malignancy and survival of ACC patients. miRNA expression profiles were determined in a series of ACC, adenoma, and normal cortices using microarray. A subset of miRNAs showed distinct expression patterns in the ACC compared with adrenal cortices and adenomas. Among others, miR-483-3p, miR-483-5p, miR-210, and miR-21 were found overexpressed, while miR-195, miR-497, and miR-1974 were underexpressed in ACC. Inhibition of miR-483-3p or miR-483-5p and overexpression of miR-195 or miR-497 reduced cell proliferation in human NCI-H295R ACC cells. In addition, downregulation of miR-483-3p, but not miR-483-5p, and increased expression of miR-195 or miR-497 led to significant induction of cell death. Protein expression of p53 upregulated modulator of apoptosis (PUMA), a potential target of miR-483-3p, was significantly decreased in ACC, and inversely correlated with miR-483-3p expression. In addition, high expression of miR-503, miR-1202, and miR-1275 were found significantly associated with shorter overall survival among patients with ACC (P values: 0.006, 0.005, and 0.042 respectively). In summary, we identified additional miRNAs associated with ACC, elucidated the functional role of four miRNAs in the pathogenesis of ACC cells, demonstrated the potential involvement of the pro-apoptotic factor PUMA (a miR-483-3p target) in adrenocortical tumors, and found novel miRNAs associated with survival in ACC.

A new mutation in the menin gene causes the multiple endocrine neoplasia type 1 syndrome with adrenocortical carcinoma

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant tumor syndrome that may be caused by mutations in the MEN1 gene on 11q13. Loss of function of the tumor suppressor gene MEN1 leads to synchronous or metachronous appearance of neuroendocrine tumors arising from neuroendocrine cells of the parathyroid and pituitary glands, the duodenum and pancreatic islets, and other endocrine organs such as the adrenal cortex. We here present a patient with MEN1 who developed hyperparathyroidism, multiple well differentiated functionally inactive neuroendocrine tumors of the pancreas and an adrenal carcinoma. We describe a new mutation at codon 443 in the coding region of exon 9 in the MEN1 gene, where a cytosine residue was exchanged for adenosine (TCC > TAC) and, consequently, serine for tyrosine (p.Ser443Tyr; c.1328C > A). [corrected] Also, we provide clinical data that may add to the genotype-phenotype discussion. We conclude that the novel mutation in the MEN1 gene described herein was clinically relevant.

Rare and unusual endocrine cancer syndromes with mutated genes

The study of a number of rare familial syndromes associated with endocrine tumor development has led to the identification of genes involved in the development of these tumors. Major advances have expanded our understanding of the pathophysiology of these rare endocrine tumors, resulting in the elucidation of causative genes in rare familial diseases and a better understanding of the signaling pathways implicated in endocrine cancers. Recognition of the familial syndrome associated with a particular patient's endocrine tumor has important implications in terms of prognosis, screening of family members, and screening for associated conditions.

Pathogenesis of benign adrenocortical tumors

Most adrenocortical tumors (ACT) are benign unilateral adrenocortical adenomas, often discovered incidentally. Exceptionally, ACT are bilateral. However bilateral ACT have been very helpful to progress in the pathophysiology of ACT. Although most ACT are of sporadic origin, they may also be part of syndromic and/or hereditary disorders. The identification of the genetics of familial diseases associated with benign ACT has been helpful to define somatic alterations in sporadic ACT: for example, identification of PRKAR1A mutations in Carney complex or alterations of the Wnt/β-catenin pathway in Familial Adenomatous Polyposis Coli. Components of the cAMP signaling pathway-for example, adrenocorticotropic-hormone receptors and other membrane receptors, Gs protein, phosphodiesterases and protein kinase A-can be altered to various degrees in benign cortisol-secreting ACT. These progress have been important for the understanding of the pathogenesis of benign ACT, but already have profound implications for clinical management, for example in unraveling the genetic origin of disease in some patients with ACT. They also have therapeutic consequences, and should help to develop new therapeutic options.

Surgical management of nonmultiple endocrine neoplasia endocrinopathies: state-of-the-art review

The development of genetic testing has given patients with familial endocrine diseases the opportunity to be identified earlier in life. The importance of this technological advancement cannot be underestimated, as some of these heritable diseases have significant potential for malignancy. This article focuses on the identification and surgical management of familial endocrinopathies of the thyroid, parathyroid, adrenal glands, and pancreas. Familial endocrinopathies discussed include hereditary nonmedullary carcinoma of the thyroid, Cowden disease, familial adenomatous polyposis, Carney complex, Werner syndrome, familial medullary thyroid carcinoma, Pendred syndrome, hereditary hyperparathyroidism jaw-tumor syndrome, familial isolated hyperparathyroidism, Beckwith- Wiedemann syndrome, Li-Fraumeni syndrome, neurofibromatosis I, von Hippel-Lindau disease, and tuberous sclerosis.

Inactivation of the Carney complex gene 1 (protein kinase A regulatory subunit 1A) inhibits SMAD3 expression and TGF beta-stimulated apoptosis in adrenocortical cells

The cyclic AMP signaling pathway can be altered at multiple levels in endocrine tumors. Its central component is the protein kinase A (PKA). Carney complex (CNC) is a hereditary multiple neoplasia syndrome resulting from inactivating mutations of the gene encoding the PKA type I alpha regulatory subunit (PRKAR1A). Primary pigmented nodular adrenocortical disease is the most frequent endocrine tumor of CNC. Transforming growth factor beta (TGFbeta) regulates adrenal cortex physiology and signals through SMAD2/3. We used an interference approach to test the effects of PRKAR1A inactivation on PKA and TGFbeta pathways and on apoptosis in adrenocortical cells. PRKAR1A silencing stimulates PKA activity and increases transcriptional activity of a PKA reporter construct and expression of the endogenous PKA target, NR4A2, under basal conditions or after forskolin stimulation. PRKAR1A inactivation also decreased SMAD3 mRNA and protein levels via PKA, altering the cellular response to TGFbeta. SMAD3 expression was also inhibited by adrenocorticorticotropic hormone in the mouse adrenal gland and by forskolin in H295R cells. TGFbeta stimulates apoptosis in H295R cells, and this effect was counteracted by PRKAR1A inactivation. PRKAR1A silencing decreased the percentage of apoptotic cells and the cleavage of apoptosis mediators [caspase-3, poly(ADP-ribose) polymerase, and lamin A/C]. Inactivating mutations of PRKAR1A observed in adrenocortical tumors alter SMAD3, leading to resistance to TGFbeta-induced apoptosis. This cross-talk between the PKA and the TGFbeta signaling pathways reveals a new mechanism of endocrine tumorigenesis.

Changing the clinical picture of challenging tumors: tales becoming reality?

The treatment of neoplastic diseases has become increasingly dependent on tumor biology and is focused on targeted therapy. Understanding complex networks of intracellular signaling pathways, blockades of specific targets and a myriad of other approaches has brought new fuel to the battle against many types of cancer. Unfortunately, the degree of benefit achieved in this new era of cancer treatment has not been distributed homogeneously among the different disease types. Neoplasms with lower incidence rates, but that are also highly challenging, are not consistently given due attention by research leaders. This article aims to evaluate new insights and potential gains obtained with new therapies in a particular group of tumors: those rarely debated in clinical practice, but which still pose a considerable challenge to clinical oncology.

Molecular classification and prognostication of adrenocortical tumors by transcriptome profiling

PURPOSE

Our understanding of adrenocortical carcinoma (ACC) has improved considerably, yet many unanswered questions remain. For instance, can molecular subtypes of ACC be identified? If so, what is their underlying pathogenetic basis and do they possess clinical significance?

EXPERIMENTAL DESIGN

We did a whole genome gene expression study of a large cohort of adrenocortical tissues annotated with clinicopathologic data. Using Affymetrix Human Genome U133 Plus 2.0 oligonucleotide arrays, transcriptional profiles were generated for 10 normal adrenal cortices (NC), 22 adrenocortical adenomas (ACA), and 33 ACCs.

RESULTS

The overall classification of adrenocortical tumors was recapitulated using principal component analysis of the entire data set. The NC and ACA cohorts showed little intragroup variation, whereas the ACC cohort revealed much greater variation in gene expression. A robust list of 2,875 differentially expressed genes in ACC compared with both NC and ACA was generated and used in functional enrichment analysis to find pathways and attributes of biological significance. Cluster analysis of the ACCs revealed two subtypes that reflected tumor proliferation, as measured by mitotic counts and cell cycle genes. Kaplan-Meier analysis of these ACC clusters showed a significant difference in survival (P < 0.020). Multivariate Cox modeling using stage, mitotic rate, and gene expression data as measured by the first principal component for ACC samples showed that gene expression data contains significant independent prognostic information (P < 0.017).

CONCLUSIONS

This study lays the foundation for the molecular classification and prognostication of adrenocortical tumors and also provides a rich source of potential diagnostic and prognostic markers.

Bone morphogenetic proteins 2 and 5 are down-regulated in adrenocortical carcinoma and modulate adrenal cell proliferation and steroidogenesis

Bone morphogenetic proteins (BMP) have been shown to affect tumorigenesis in a variety of tumors. Quantitative PCR analysis revealed down-regulation of BMP2 and BMP5 in tissue samples from adrenocortical carcinoma and adrenocortical tumor cell lines compared with normal adrenal glands. Integrity of BMP-dependent pathways in these cell lines could be shown by activation of the Smad1/5/8 pathway with subsequent increase of ID protein expression upon incubation with BMP2 or BMP5. On a functional level, BMP treatment resulted in inhibition of cell proliferation and viability in a dose- and time-dependent manner. This growth inhibitory effect was associated with BMP-dependent reduction of AKT phosphorylation under baseline conditions and under insulin-like growth factor costimulation. Furthermore, steroidogenic function, including melanocortin-2 receptor and steroidogenic enzyme expressions, was profoundly reduced. In vitro demethylation treatment and overexpression of GATA6 resulted in reactivation of BMP-dependent pathways with concomitant modulation of steroidogenesis. Taken together, we show that loss of expression of members of the BMP family of ligands is a common finding in adrenocortical tumors and we provide evidence that BMP-dependent pathways are likely to be involved in the modulation of the malignant and functional phenotype of adrenocortical cancer cells.

MicroRNA signature of primary pigmented nodular adrenocortical disease: clinical correlations and regulation of Wnt signaling

MicroRNAs comprise a novel group of gene regulators implicated in the development of different types of cancer; however, their role in primary pigmented nodular adrenocortical disease (PPNAD) has not been investigated. PPNAD is a bilateral adrenal hyperplasia often associated with Carney complex, a multiple neoplasia syndrome; both disorders are caused by protein kinase A (PKA) regulatory subunit type 1A (PRKARIA)-inactivating mutations. We identified a 44-microRNA gene signature of PPNAD after comparing PPNAD with normal adrenal samples. Specifically, 33 microRNAs were up-regulated and 11 down-regulated in PPNAD relative to normal tissues. These results were validated by stem loop real-time PCR analysis. Comparison of microRNA microarray data with clinicopathologic variables revealed a negative correlation (r = -0.9499) between let-7b expression and cortisol levels in patients with PPNAD. Integration of microRNA microarray with serial analysis of gene expression data together with bioinformatic algorithm predictions revealed nine microRNA-gene target pairs with a potential role in adrenal pathogenesis. Using a PPNAD cell line, we showed that miR-449 was up-regulated and identified its direct target, WNT1-inducible signaling pathway protein 2 (WISP2); in addition, pharmacologic inhibition of PKA resulted in the up-regulation of miR-449 leading to the suppression of WISP2. Overall, we investigated, for the first time, the microRNA profile and its clinical significance in PPNAD; these data also suggest that PKA, via microRNA regulation, affects the Wnt signaling pathway, which through expression and clinical studies is suspected to be a primary mediator of PRKAR1A-related tumorigenesis.

Gene expression profiling reveals a new classification of adrenocortical tumors and identifies molecular predictors of malignancy and survival

PURPOSE

Adrenocortical tumors, especially cancers, remain challenging both for their diagnosis and prognosis assessment. The aim of this article is to identify molecular predictors of malignancy and of survival.

PATIENTS AND METHODS

One hundred fifty-three unilateral adrenocortical tumors were studied by microarray (n = 92) or reverse transcription quantitative polymerase chain reaction (n = 148). A two-gene predictor of malignancy was built using the disease-free survival as the end point in a training cohort (n = 47), then validated in an independent validation cohort (n = 104). The best candidate genes were selected using Cox models, and the best gene combination was validated using the log-rank test. Similarly, for malignant tumors, a two-gene predictor of survival was built using the overall survival as the end point in a training cohort (n = 23), then tested in an independent validation cohort (n = 35).

RESULTS

Unsupervised clustering analysis discriminated robustly the malignant and benign tumors, and identified two groups of malignant tumors with very different outcome. The combined expression of DLG7 and PINK1 was the best predictor of disease-free survival (log-rank P approximately 10(-12)), could overcome the uncertainties of intermediate pathological Weiss scores, and remained significant after adjustment to the Weiss score (P < 1.3 x 10(-2)). Among the malignant tumors, the combined expression of BUB1B and PINK1 was the best predictor of overall survival (P < 2 x 10(-6)), and remained significant after adjusting for MacFarlane staging (P < .005).

CONCLUSION

Gene expression analysis unravels two distinct groups of adrenocortical carcinomas. The molecular predictors of malignancy and of survival are reliable and provide valuable independent information in addition to pathology and tumor staging. These original tools should provide important improvements for adrenal tumors management.

[Sporadic adrenocortical tumors: genetics and perspectives for the pathologist]

Most adrenocortical tumors are benign; adrenocortical carcinomas are rare but their prognosis is poor and few therapeutic options are available. In most adrenocortical tumors, the morphological approach provides enough elements to establish the differential diagnosis between a benign and a malignant tumor but in few cases, it is insufficient. Moreover, morphology is limited for predicting prognosis of adrenocortical carcinomas. These observations led to development of other approaches, in particular immunohistochemical and genetic approaches. The comprehension of the genetic syndromes associated with adrenocortical tumors led to progress in the identification of genetic abnormalities involved in sporadic adrenocortical tumorigenesis. Thus, in sporadic adrenocortical tumorigenesis, IGF-II overexpression and cyclin E overproduction have been associated with 11p15 alterations which are observed in Bethwith-Wiedemann syndrome and TP53 inactivating mutations and 17p13 locus abnormalities which are observed in Li-Fraumeni syndrome. Activation of the Wnt/ss-catenin signaling pathway which is observed in familial adenomatous polyposis has been found in adrenocortical adenomas and carcinomas associated to mutations of CTNNB1, the gene coding ss-catenin, suggesting a central role for this pathway in adrenocortical tumorigenesis. These genetics findings already have had repercussions for patients via the development of molecular markers for diagnosis and prognosis; in the future they should be helpful in the development of new therapeutics.

Rosiglitazone inhibits adrenocortical cancer cell proliferation by interfering with the IGF-IR intracellular signaling

Rosiglitazone (RGZ), a thiazolidinedione ligand of the peroxisome proliferator-activated receptor (PPAR)-γ, has been recently described as possessing antitumoral properties. We investigated RGZ effect on cell proliferation in two cell line models (SW13 and H295R) of human adrenocortical carcinoma (ACC) and its interaction with the signaling pathways of the activated IGF-I receptor (IGF-IR). We demonstrate a high expression of IGF-IR in the two cell lines and in ACC. Cell proliferation is stimulated by IGF-I in a dose- and time-dependent manner and is inhibited by RGZ. The analysis of the main intracellular signaling pathways downstream of the activated IGF-IR, phosphatidyl inositol 3-kinase (PI3K)-Akt, and extracellular signal-regulated kinase (ERK1/2) cascades reveals that RGZ rapidly interferes with the Akt and ERK1/2 phosphorylation/activation which mediates IGF-I stimulated proliferation. In conclusion, our results suggest that RGZ exerts an inhibitory effect on human ACC cell proliferation by interfering with the PI3K/Akt and ERK1/2 signaling pathways downstream of the activated IGF-IR.

Identification of a clinically homogenous subgroup of benign cortisol-secreting adrenocortical tumors characterized by alterations of the protein kinase A (PKA) subunits and high PKA activity

OBJECTIVE

The cAMP/protein kinase A (PKA) pathway plays an important role in endocrine tumorigenesis. PKA is a heterotetramer with two regulatory subunits (four genes: PRKAR1A, PRKAR1B, PRKAR2A, PRKAR2B) and two catalytic subunits. Inactivating PRKAR1A mutations have been observed in Carney complex and a subset of adrenocortical tumors (ACT). This study was designed to search for other alterations of PKA in ACT, and to establish their correlation with the clinical characteristics.

METHODS

In this study, 35 ACT (10 non-secreting adrenocortical adenomas (ACA-NS), 13 cortisol-secreting adenomas (ACA-S), and 12 malignant s (ACC)) were studied. PKA subunits were studied by western blot and RT-qPCR. The PKA activity was measured.

RESULTS

A subgroup of ACA-S with a 96% R2B protein decrease by comparison with normal adrenal (4.1%+/-4 vs 100%+/-19, P<0.001) was identified, ACA-S2 (6/13). By contrast, no differences were observed in ACC and ACA-NS. The level of R1A mRNA was decreased in ACA-S (P<0.001), but not the level of R2B mRNA. No mutation of the R2B gene was detected in ACA-S2. The ACA-S2 group with loss of R2B protein showed a threefold higher basal PKA activity than the ACA with normal R2B protein (3.37+/-0.31 vs 1.00+/-0.20, P<0.0001). The ACA-S2 tumors with the loss of the R2B protein presented a homogenous phenotype and were all small benign cortisol-secreting tumors.

CONCLUSION

This loss of PRKAR2B protein due to a post-transcriptional mechanism in ACA-S is a new mechanism of cAMP pathway dysregulation in adrenocortical tumorigenesis. It defines a new subtype of secreting adenomas with high basal PKA activity presenting a homogenous clinical phenotype.