Age-dependent effects of Armc5 haploinsufficiency on adrenocortical function

Inactivating mutations in the Armadillo repeat-containing 5 (ARMC5) gene have recently been discovered in primary macronodular adrenal hyperplasia (PMAH), a cause of Cushing syndrome. Biallelic ARMC5 inactivation in PMAH suggested that ARMC5 may have tumor suppressor functions in the adrenal cortex. We generated and characterized a new mouse model of Armc5 deficiency. Almost all Armc5 knockout mice died during early embryonic development, around 6.5 and 8.5 days. Knockout embryos did not undergo gastrulation, as demonstrated by the absence of mesoderm development at E7.5. Armc5 heterozygote mice (Armc5+/-) developed normally but at the age of 1 year, their corticosterone levels decreased; this was associated with a decrease of protein kinase A (PKA) catalytic subunit α (Cα) expression both at the RNA and protein levels that were also seen in human patients with PMAH and ARMC5 defects. However, this was transient, as corticosterone levels normalized later, followed by the development of hypercorticosteronemia in one-third of the mice at 18 months of age, which was associated with increases in PKA and Cα expression. Adrenocortical tissue analysis from Armc5+/- mice at 18 months showed an abnormal activation of the Wnt/β-catenin signaling pathway in a subset of zona fasciculata cells. These data confirm that Armc5 plays an important role in early mouse embryonic development. Our new mouse line can be used to study tissue-specific effects of Armc5. Finally, Armc5 haploinsufficiency leads to Cushing syndrome in mice, but only later in life, and this involves PKA, its catalytic subunit Cα, and the Wnt/β-catenin pathway.

Cofilin is a cAMP effector in mediating actin cytoskeleton reorganization and steroidogenesis in mouse and human adrenocortical tumor cells

cAMP pathway plays a major role in the pathogenesis of cortisol-producing adrenocortical adenomas (CPA). cAMP-induced steroidogenesis is preceded by actin cytoskeleton reorganization, a process regulated by cofilin activity. In this study we investigated cofilin role in mediating cAMP effects on cell morphology and steroidogenesis in adrenocortical tumor cells. We demonstrated that forskolin induced cell rounding and strongly reduced phosphorylated (P)-cofilin/total cofilin ratio in Y1 (-52 ± 16%, p < 0.001) and human CPA cells (-53 ± 18%, p < 0.05). Cofilin silencing significantly reduced both forskolin-induced morphological changes and progesterone production (1.3-fold vs 1.8-fold in controls, p < 0.05), whereas transfection of wild-type or S3A (active), but not S3D (inactive) cofilin, potentiated forskolin effects on cell rounding and increased 3-fold progesterone synthesis with respect to control (p < 0.05). Furthermore, cofilin dephosphorylation by a ROCK inhibitor potentiated forskolin-induced cell rounding and steroidogenesis (2-fold increase vs forskolin alone). Finally, we found a reduced P-cofilin/total cofilin ratio and increased cofilin expression in CPA vs endocrine inactive adenomas by western blot and immunohistochemistry. Overall, these results identified cofilin as a mediator of cAMP effects on both morphological changes and steroidogenesis in mouse and human adrenocortical tumor cells.

From benign adrenal incidentaloma to adrenocortical carcinoma: an exceptional random event

New European guidelines for the management of adrenal incidentalomas were recently released. One of the most novel recommendations is to stop following patients when they present a typical, small and non-secreting adenoma. We report here the case of a 71-year-old man with such an adenoma, who developed an adrenocortical carcinoma (ACC) fourteen years later, with subsequent metastases and death. Clinically, he had a normal blood pressure and no sign of hormonal hypersecretion. The hormonal work-up showed no hormone excess: urinary free cortisol level was normal, the diurnal cortisol rhythm was respected and urinary catecholamine metabolites levels were normal. Computed tomography (CT) scan showed a homogeneous lesion, with a low density. The lesion remained unchanged during the five years of follow-up. Eight years after the last CT, a large right heterogeneous adrenal mass was incidentally discovered during an ultrasound examination. On CT scan, it was a 6 cm heterogeneous tumor. On hormonal work-up, there was no secretion. The patient was operated of an adrenalectomy, and the histology described an ACC with a Weiss score at 8, with no benign contingent. To our knowledge, this is the first case of an ACC occurring in a patient with prior adrenal imaging showing a typical benign adenoma.

Cabergoline for Cushing's disease: a large retrospective multicenter study

OBJECTIVE

The efficacy of cabergoline in Cushing's disease (CD) is controversial. The aim of this study was to assess the efficacy and tolerability of cabergoline in a large contemporary cohort of patients with CD.

DESIGN

We conducted a retrospective multicenter study from thirteen French and Belgian university hospitals.

METHODS

Sixty-two patients with CD received cabergoline monotherapy or add-on therapy. Symptom score, biological markers of hypercortisolism and adverse effects were recorded.

RESULTS

Twenty-one (40%) of 53 patients who received cabergoline monotherapy had normal urinary free cortisol (UFC) values within 12 months (complete responders), and five of these patients developed corticotropic insufficiency. The fall in UFC was associated with significant reductions in midnight cortisol and plasma ACTH, and with clinical improvement. Compared to other patients, complete responders had similar median baseline UFC (2.0 vs 2.5xULN) and plasma prolactin concentrations but received lower doses of cabergoline (1.5 vs 3.5 mg/week, P < 0.05). During long-term treatment (>12 months), cabergoline was withdrawn in 28% of complete responders because of treatment escape or intolerance. Overall, sustained control of hypercortisolism was obtained in 23% of patients for 32.5 months (19-105). Nine patients on steroidogenesis inhibitors received cabergoline add-on therapy for 19 months (1-240). Hypercortisolism was controlled in 56% of these patients during the first year of treatment with cabergoline at 1.0 mg/week (0.5-3.5).

CONCLUSIONS

About 20-25% of CD patients are good responders to cabergoline therapy allowing long-term control of hypercortisolism at relatively low dosages and with acceptable tolerability. No single parameter, including the baseline UFC and prolactin levels, predicted the response to cabergoline.

Analysis of ARMC5 expression in human tissues

Mutations in ARMC5 gene have been recently identified as the main cause of Primary Macronodular Adrenocortical Hyperplasia (PMAH). PMAH patients have an ARMC5 germline mutation and, in addition, somatic tissue-specific mutations. This is consistent with the two-hit hypothesis of tumorigenesis and suggests that ARMC5 may be a tumor suppressor gene. As its function is still unclear, we analyzed the expression of the four ARMC5 isoforms in 46 normal human tissues. This showed that at least one ARMC5 isoform is ubiquitously expressed throughout the body; however, only 7 tissues expressed all isoforms, including the adrenal gland and the brain. Interestingly, the highest expression for ARMC5 in the brain is in the pituitary gland. The isoform ARMC5-003 was present in most endocrine tissues including the pituitary, adrenal glands and the pancreas. In this report, we present new data about the ARMC5 expression pattern in human tissues; its wide expression in brain, pituitary gland and other tissues suggest that mutations may be responsible for additional pathologies, beyond what is already known in PMAH and meningiomas.

Functional Implications of LH/hCG Receptors in Pregnancy-Induced Cushing Syndrome

Context:

Elevated human choriogonadotropin (hCG) may stimulate aberrantly expressed luteinizing hormone (LH)/hCG receptor (LHCGR) in adrenal glands, resulting in pregnancy-induced bilateral macronodular adrenal hyperplasia and transient Cushing syndrome (CS).

Objective:

To determine the role of LHCGR in transient, pregnancy-induced CS.

Design, Setting, Patient, and Intervention:

We investigated the functional implications of LHCGRs in a patient presenting, at a tertiary referral center, with repeated pregnancy-induced CS with bilateral adrenal hyperplasia, resolving after parturition.

Main Outcome Measures and Results:

Acute testing for aberrant hormone receptors was negative except for arginine vasopressin (AVP)–increased cortisol secretion. Long-term hCG stimulation induced hypercortisolism, which was unsuppressed by dexamethasone. Postadrenalectomy histopathology demonstrated steroidogenically active adrenocortical hyperplasia and ectopic cortical cell clusters in the medulla. Quantitative polymerase chain reaction showed upregulated expression of LHCGR, transcription factors GATA4, ZFPM2, and proopiomelanocortin (POMC), AVP receptors (AVPRs) AVPR1A and AVPR2, and downregulated melanocortin 2 receptor (MC2R) vs control adrenals. LHCGR was localized in subcapsular, zona glomerulosa, and hyperplastic cells. Single adrenocorticotropic hormone–positive medullary cells were demonstrated in the zona reticularis. The role of adrenal adrenocorticotropic hormone was considered negligible due to downregulated MC2R. Coexpression of CYP11B1/CYP11B2 and AVPR1A/AVPR2 was observed in ectopic cortical cells in the medulla. hCG stimulation of the patient’s adrenal cell cultures significantly increased cyclic adenosine monophosphate, corticosterone, 11-deoxycortisol, cortisol, and androstenedione production. CTNNB1, PRKAR1A, ARMC5, and PRKACA gene mutational analyses were negative.

Conclusion:

Nongenetic, transient, somatic mutation-independent, pregnancy-induced CS was due to hCG-stimulated transformation of LHCGR-positive undifferentiated subcapsular cells (presumably adrenocortical progenitors) into LHCGR-positive hyperplastic cortical cells. These cells respond to hCG stimulation with cortisol secretion. Without the ligand, they persist with aberrant LHCGR expression and the ability to respond to the same stimulus.

Genetic Landscape of Sporadic Unilateral Adrenocortical Adenomas Without PRKACA p.Leu206Arg Mutation

CONTEXT

Adrenocortical adenomas (ACAs) are among the most frequent human neoplasias. Genetic alterations affecting the cAMP/protein kinase A signaling pathway are common in cortisol-producing ACAs, whereas activating mutations in the gene encoding β-catenin (CTNNB1) have been reported in a subset of both benign and malignant adrenocortical tumors. However, the molecular pathogenesis of most ACAs is still largely unclear.

OBJECTIVE

The aim of the study was to define the genetic landscape of sporadic unilateral ACAs.

DESIGN AND SETTING

Next-generation whole-exome sequencing was performed on fresh-frozen tumor samples and corresponding normal tissue samples.

PATIENTS

Ninety-nine patients with ACAs (74 cortisol-producing and 25 endocrine inactive) negative for p.Leu206Arg PRKACA mutation.

MAIN OUTCOME MEASURES

Identification of known and/or new genetic alterations potentially involved in adrenocortical tumorigenesis and autonomous hormone secretion, genotype-phenotype correlation.

RESULTS

A total of 706 somatic protein-altering mutations were detected in 88 of 99 tumors (median, six per tumor). We identified several mutations in genes of the cAMP/protein kinase A pathway, including three novel mutations in PRKACA, associated with female sex and Cushing's syndrome. We also found genetic alterations in different genes involved in the Wnt/β-catenin pathway, associated with larger tumors and endocrine inactivity, and notably, in many genes of the Ca(2+)-signaling pathway. Finally, by comparison of our genetic data with those available in the literature, we describe a comprehensive genetic landscape of unilateral ACAs.

CONCLUSIONS

This study provides the largest sequencing effort on ACAs to date. We thereby identified somatic alterations affecting known and novel pathways potentially involved in adrenal tumorigenesis.

Serum RARRES2 Is a Prognostic Marker in Patients With Adrenocortical Carcinoma

CONTEXT

Retinoic acid receptor responder protein 2 (RARRES2) is a small secreted protein involved in multiple cancers, including adrenocortical carcinoma (ACC). However, discordant tumor and serum RARRES2 levels have been reported in various cancers. The etiology of this discordance is unknown and has not been studied in pair-matched tumor and serum samples.

OBJECTIVE

To determine tissue and serum RARRES2 levels in patients with adrenocortical neoplasm and to elucidate the prognostic implications of RARRES2 levels.

DESIGN, SETTINGS, AND PATIENTS

Tissue and serum RARRES2 levels were analyzed. A pair-matched analysis was performed to examine tissue and serum RARRES2 from 51 patients with benign adrenocortical tumors and 18 patients with ACC. Overall survival was analyzed based on RARRES2 expression. A mouse xenograft model was used to determine the source of serum RARRES2.

RESULTS

Patients with ACC had decreased tumor RARRES2 gene expression (P < .0001) and increased serum RARRES2 levels (P < .005) as compared with patients with benign adrenocortical tumors. Higher serum RARRES2 levels were associated with improved overall survival (P = .0227). A mouse xenograft model demonstrated that higher tissue RARRES2 expression was associated with higher RARRES2 secretion in the serum and that there was an intrinsic mechanism in maintaining serum RARRES2 homeostasis.

CONCLUSIONS

Serum and tissue RARRES2 expression levels are paradoxical in patients with ACC. The elevated RARRES2 in patient serum is unlikely to be secreted from tumor cells. Serum RARRES2 may be used as a novel prognostic marker for ACC.

Prognostic factors in stage III-IV adrenocortical carcinomas (ACC): an European Network for the Study of Adrenal Tumor (ENSAT) study

BACKGROUND

The clinical course of advanced adrenocortical carcinoma (ACC) is heterogeneous. Our study aimed primarily to refine and make headway in the prognostic stratification of advanced ACC.

PATIENTS AND METHODS

Patients with advanced ENSAT ACC (stage III or stage IV) at diagnosis registered between 2000 and 2009 in the ENSAT database were enrolled. The primary end point was overall survival (OS). Parameters of potential prognostic relevance were selected. Univariate and multivariate analyses were carried out: model 1 'before surgery'; model 2 'post-surgery'.

RESULTS

Four hundred and forty-four patients with advanced ENSAT ACC (stage III: 210; stage IV: 234) were analyzed. After a median follow-up of 55.2 months, the median OS was 24 months. A modified ENSAT (mENSAT) classification was validated: stage III (invasion of surrounding tissues/organs or the vena renalis/cava) and stage IVa, IVb, IVc (2, 3 or >3 metastatic organs, including N, respectively). Two- or 5-year OS was 73%, 46%, 26% and 15% or 50%, 15%, 14% and 2% for stages III, IVa, IVb and IVc, respectively. In the multivariate analysis, mENSAT stages (stages IVa, IVb, or IVc, respectively) were significantly correlated with OS (P < 0.0001), as well as additional parameters: age ≥ 50 years (P < 0.0001), tumor- or hormone-related symptoms (P = 0.01 and 0.03, respectively) in model 1 but also the R status (P = 0.001) and Grade (Weiss >6 and/or Ki67 ≥ 20%, P = 0.06) in model 2.

CONCLUSION

The mENSAT classification and GRAS parameters (Grade, R status, Age and Symptoms) were found to best stratify the prognosis of patients with advanced ACC.

Unraveling the intrafamilial correlations and heritability of tumor types in MEN1: a Groupe d'étude des Tumeurs Endocrines study

BACKGROUND

MEN1, which is secondary to the mutation of the MEN1 gene, is a rare autosomal-dominant disease that predisposes mutation carriers to endocrine tumors. Most studies demonstrated the absence of direct genotype-phenotype correlations. The existence of a higher risk of death in the Groupe d'étude des Tumeurs Endocrines-cohort associated with a mutation in the JunD interacting domain suggests heterogeneity across families in disease expressivity. This study aims to assess the existence of modifying genetic factors by estimating the intrafamilial correlations and heritability of the six main tumor types in MEN1.

METHODS

The study included 797 patients from 265 kindred and studied seven phenotypic criteria: parathyroid and pancreatic neuroendocrine tumors (NETs) and pituitary, adrenal, bronchial, and thymic (thNET) tumors and the presence of metastasis. Intrafamilial correlations and heritability estimates were calculated from family tree data using specific validated statistical analysis software.

RESULTS

Intrafamilial correlations were significant and decreased along parental degrees distance for pituitary, adrenal and thNETs. The heritability of these three tumor types was consistently strong and significant with 64% (s.e.m.=0.13; P<0.001) for pituitary tumor, 65% (s.e.m.=0.21; P<0.001) for adrenal tumors, and 97% (s.e.m.=0.41; P=0.006) for thNETs.

CONCLUSION

The present study shows the existence of modifying genetic factors for thymus, adrenal, and pituitary MEN1 tumor types. The identification of at-risk subgroups of individuals within cohorts is the first step toward personalization of care. Next generation sequencing on this subset of tumors will help identify the molecular basis of MEN1 variable genetic expressivity.

Functional Characterization of PRKAR1A Mutations Reveals a Unique Molecular Mechanism Causing Acrodysostosis but Multiple Mechanisms Causing Carney Complex

The main target of cAMP is PKA, the main regulatory subunit of which (PRKAR1A) presents mutations in two genetic disorders: acrodysostosis and Carney complex. In addition to the initial recurrent mutation (R368X) of the PRKAR1A gene, several missense and nonsense mutations have been observed recently in acrodysostosis with hormonal resistance. These mutations are located in one of the two cAMP-binding domains of the protein, and their functional characterization is presented here. Expression of each of the PRKAR1A mutants results in a reduction of forskolin-induced PKA activation (measured by a reporter assay) and an impaired ability of cAMP to dissociate PRKAR1A from the catalytic PKA subunits by BRET assay. Modeling studies and sensitivity to cAMP analogs specific for domain A (8-piperidinoadenosine 3',5'-cyclic monophosphate) or domain B (8-(6-aminohexyl)aminoadenosine-3',5'-cyclic monophosphate) indicate that the mutations impair cAMP binding locally in the domain containing the mutation. Interestingly, two of these mutations affect amino acids for which alternative amino acid substitutions have been reported to cause the Carney complex phenotype. To decipher the molecular mechanism through which homologous substitutions can produce such strikingly different clinical phenotypes, we studied these mutations using the same approaches. Interestingly, the Carney mutants also demonstrated resistance to cAMP, but they expressed additional functional defects, including accelerated PRKAR1A protein degradation. These data demonstrate that a cAMP binding defect is the common molecular mechanism for resistance of PKA activation in acrodysosotosis and that several distinct mechanisms lead to constitutive PKA activation in Carney complex.

Clinical and genetic characterization of pituitary gigantism: an international collaborative study in 208 patients

Despite being a classical growth disorder, pituitary gigantism has not been studied previously in a standardized way. We performed a retrospective, multicenter, international study to characterize a large series of pituitary gigantism patients. We included 208 patients (163 males; 78.4%) with growth hormone excess and a current/previous abnormal growth velocity for age or final height >2 s.d. above country normal means. The median onset of rapid growth was 13 years and occurred significantly earlier in females than in males; pituitary adenomas were diagnosed earlier in females than males (15.8 vs 21.5 years respectively). Adenomas were ≥10 mm (i.e., macroadenomas) in 84%, of which extrasellar extension occurred in 77% and invasion in 54%. GH/IGF1 control was achieved in 39% during long-term follow-up. Final height was greater in younger onset patients, with larger tumors and higher GH levels. Later disease control was associated with a greater difference from mid-parental height (r=0.23, P=0.02). AIP mutations occurred in 29%; microduplication at Xq26.3 - X-linked acrogigantism (X-LAG) - occurred in two familial isolated pituitary adenoma kindreds and in ten sporadic patients. Tumor size was not different in X-LAG, AIP mutated and genetically negative patient groups. AIP-mutated and X-LAG patients were significantly younger at onset and diagnosis, but disease control was worse in genetically negative cases. Pituitary gigantism patients are characterized by male predominance and large tumors that are difficult to control. Treatment delay increases final height and symptom burden. AIP mutations and X-LAG explain many cases, but no genetic etiology is seen in >50% of cases.

Paracrine control of steroidogenesis by serotonin in adrenocortical neoplasms

Serotonin (5-hydroxytryptamine; 5-HT) is able to activate the hypothalamo-pituitary-adrenal axis via multiple actions at different levels. In the human adrenal gland, 5-HT, released by subcapsular mast cells, stimulates corticosteroid production through a paracrine mode of communication which involves 5-HT receptor type 4 (5-HT4) primarily located in zona glomerulosa. As a result, 5-HT is much more efficient to stimulate aldosterone secretion than cortisol release in vitro and administration of 5-HT4 receptor agonists to healthy individuals is followed by an increase in plasma aldosterone levels without any change in plasma cortisol concentrations. Interestingly, adrenocortical hyperplasias and tumors responsible for corticosteroid hypersecretion exhibit various cellular and molecular defects which tend to reinforce the intraadrenal serotonergic tone. These pathophysiological mechanisms, which are summarized in the present review, include an increase in adrenal 5-HT production and overexpression of 5-HT receptors in adrenal neoplastic tissues. Altogether, these data support the concept of adrenal serotonergic paracrinopathy and suggest that 5-HT and its receptors may constitute valuable targets for pharmacological treatments of primary adrenal diseases.

Gigantism and acromegaly due to Xq26 microduplications and GPR101 mutation

BACKGROUND

Increased secretion of growth hormone leads to gigantism in children and acromegaly in adults; the genetic causes of gigantism and acromegaly are poorly understood.

METHODS

We performed clinical and genetic studies of samples obtained from 43 patients with gigantism and then sequenced an implicated gene in samples from 248 patients with acromegaly.

RESULTS

We observed microduplication on chromosome Xq26.3 in samples from 13 patients with gigantism; of these samples, 4 were obtained from members of two unrelated kindreds, and 9 were from patients with sporadic cases. All the patients had disease onset during early childhood. Of the patients with gigantism who did not carry an Xq26.3 microduplication, none presented before the age of 5 years. Genomic characterization of the Xq26.3 region suggests that the microduplications are generated during chromosome replication and that they contain four protein-coding genes. Only one of these genes, GPR101, which encodes a G-protein-coupled receptor, was overexpressed in patients' pituitary lesions. We identified a recurrent GPR101 mutation (p.E308D) in 11 of 248 patients with acromegaly, with the mutation found mostly in tumors. When the mutation was transfected into rat GH3 cells, it led to increased release of growth hormone and proliferation of growth hormone-producing cells.

CONCLUSIONS

We describe a pediatric disorder (which we have termed X-linked acrogigantism [X-LAG]) that is caused by an Xq26.3 genomic duplication and is characterized by early-onset gigantism resulting from an excess of growth hormone. Duplication of GPR101 probably causes X-LAG. We also found a recurrent mutation in GPR101 in some adults with acromegaly. (Funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development and others.).

Abnormal Sensitivity to Glucagon and Related Peptides in Primary Adrenal Cushing's Syndrome

Illegitimate G-protein coupled receptors are known to control cortisol secretion in adrenal adenomas and bilateral macronodular adrenal hyperplasias (BMAHs) causing Cushing's syndrome. In the present study, we have evaluated the role of glucagon in the regulation of cortisol secretion in 13 patients with BMAH or adrenocortical adenoma causing subclinical or overt Cushing's syndrome. Injection of glucagon provoked an increase in plasma cortisol in 2 patients. After surgery, immunohistochemical studies showed the presence of glucagon receptor-like immunoreactivity in clusters of spongiocytic cells in adrenal tissues from patients who were sensitive in vivo to glucagon. We also observed an in vitro cortisol response to vasoactive intestinal peptide from an adenoma, which was insensitive to glucagon and pituitary adenylate cyclase-activating peptide. Altogether, our data show that ectopic glucagon receptors are expressed in some adrenal cortisol-producing benign lesions. Our results also indicate that circulating glucagon may influence cortisol release under fasting conditions.

Comparison of the effects of PRKAR1A and PRKAR2B depletion on signaling pathways, cell growth, and cell cycle control of adrenocortical cells

The cyclic AMP/protein kinase A signaling cascade is one of the main pathways involved in the pathogenesis of adrenocortical tumors. The PKA R1A and R2B proteins are the most abundant regulatory subunits in endocrine tissues. Inactivating mutations of PRKAR1A are associated with Carney complex and a subset of sporadic tumors and the abundance of R2B protein is low in a subset of secreting adrenocortical adenomas. We previously showed that PRKAR1A and PRKAR2B inactivation have anti-apoptotic effects on the adrenocortical carcinoma cell line H295R. The aim of this study was to compare the effects of PRKAR1A and PRKAR2B depletion on cell proliferation, apoptosis, cell signaling pathways, and cell cycle regulation. We found that PRKAR2B depletion is compensated by an upregulation of R1A protein, whereas PRKAR1A depletion has no effect on the production of R2B. The depletion of either PRKAR1A or PRKAR2B promotes the expression of Bcl-xL and resistance to apoptosis; and is associated with a high percentage of cells in S and G2 phase, activates PKA and MEK/ERK pathways, and impairs the expression of IkB leading to activate the NF-κB pathway. However, we observed differences in the regulation of cyclins. The depletion of PRKAR1A leads to the accumulation of cyclin D1 and p27kip, whereas the depletion of PRKAR2B promotes the accumulation of cyclin A, B, cdk1, cdc2, and p21Cip. In conclusion, although the depletion of PRKAR1A and PRKAR2B in adrenocortical cells has similar effects on cell proliferation and apoptosis; loss of these PKA subunits differentially affects cyclin expression.

Protein kinase A alterations in adrenocortical tumors

Stimulation of the cAMP pathway by adrenocorticotropin (ACTH) is essential for adrenal cortex maintenance, glucocorticoid and adrenal androgens synthesis, and secretion. Various molecular and cellular alterations of the cAMP pathway have been observed in endocrine tumors. Protein kinase A (PKA) is a central key component of the cAMP pathway. Molecular alterations of PKA subunits have been observed in adrenocortical tumors. PKA molecular defects can be germline in hereditary disorders or somatic in sporadic tumors. Heterozygous germline inactivating mutations of the PKA regulatory subunit RIα gene (PRKAR1A) can be observed in patients with ACTH-independent Cushing's syndrome (CS) due to primary pigmented nodular adrenocortical disease (PPNAD). PRKAR1A is considered as a tumor suppressor gene. Interestingly, these mutations can also be observed as somatic alterations in sporadic cortisol-secreting adrenocortical adenomas. Germline gene duplication of the catalytic subunits Cα (PRKACA) has been observed in patients with PPNAD. Furthermore, exome sequencing revealed recently activating somatic mutations of PRKACA in about 40% of cortisol-secreting adrenocortical adenomas. In vitro and in vivo functional studies help in the progress to understand the mechanisms of adrenocortical tumors development due to PKA regulatory subunits alterations. All these alterations are observed in benign oversecreting tumors and are mimicking in some way cAMP pathway constitutive activation. On the long term, unraveling these alterations will open new strategies of pharmacological treatment targeting the cAMP pathway in adrenal tumors and cortisol-secretion disorders.

Abstract LB-182: Constitutive activation of PRKACA in adrenal Cushing's syndrome

Corticotropin-independent Cushing's syndrome may be caused by tumors or hyperplasia of the adrenal cortex. Until now genetic alterations explain only a small fraction of cases. The observation that a subset of adrenal adenomas is characterized by abnormal PKA activity despite the absence of mutations in candidate genes suggested as yet unknown alterations in the cAMP/PKA signaling cascade in these tumors. The aim of this study was the analysis of the genetic basis of Cushing's syndrome in order to reveal the gene/s responsible for the disease. Exome sequencing was performed in ten cortisol-producing adenomas and recurrent mutations in candidate genes were evaluated in additional 171 patients with adrenocortical tumors. Genome-wide copy number analysis was performed in 35 patients with cortisol secreting bilateral hyperplasias. The effects of these genetic defects were studied both clinically and in vitro. Exome sequencing in 8/10 adenomas revealed somatic mutations in the PRKACA gene, which encodes the main catalytic subunit of cyclic AMP-dependent protein kinase (PKA) (c.617A&gt;C in seven and c.595_596insCAC in one). Overall, PRKACA somatic mutations were identified in a total of 22/59 (37%) adenomas from patients with overt Cushing's syndrome while these mutations were not detectable in patients with subclinical hypercortisolism (n=40) or in other adrenal tumors (n=82). Among 35 patients with cortisol producing hyperplasias, 5 (with two patients as first degree relatives) carried germline copy number gain of the chromosome 19 region including the PRKACA gene. In vitro studies demonstrated impaired inhibition of the mutant PRKACA by the PKA regulatory subunit, while cells from patients with germline chromosomal gains showed increased protein levels; in both cases, PKA activity was increased. The present study shows that more than one third of cortisol-producing adenomas associated with overt Cushing syndrome harbor unique somatic mutations of the main cAMP-dependent kinase catalytic subunit, PRKACA resulting in constitutive PKA activation. While in these patients the mutation is present only in tumor cells, germline duplication of the PRKACA gene was identified in a group of patients with bilateral adrenal hyperplasias. This is the first report of genetic alterations of the catalytic subunit of PKA linked to human disease: Germline PRKACA duplications with bilateral adrenal hyperplasias and somatic PRKACA mutations with unilateral cortisol producing adrenal adenomas.

Citation Format: Fabio R. Faucz, Felix Beuschlei, Martin Fassnacht, Guilaume Assie, Davide Calebiro, Constantine Stratakis, Andrea Osswald, Cristina L. Ronchi, Thomas Wieland, Silviu Sbiera, Katrin Schaak, Anett Schmittfull, Thomas Schwarzmayr, Olivia Barreau, Delphine Vezzosi, Marthe Rizk-Rabbin, Ulrike Zabel, Eva Szarek, Paraskevi Salpea, Antonella Forlino, Annalisa Vetro, Orsetta Zuffardi, Caroline Kisker, Susanne Diener, Thomas Meitinger, Martin J. Lohse, Martin Reincke, Jerome Bertherat, Tim M. Strom, Bruno Allolio. Constitutive activation of PRKACA in adrenal Cushing's syndrome. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr LB-182. doi:10.1158/1538-7445.AM2014-LB-182

A rare case of familial Cushing's syndrome with a common presentation of weight gain due to a mutation of the PRKAR1A gene causing isolated primary pigmented nodular adrenocortical disease

BACKGROUND

Cushing's syndrome (CS) is uncommon in childhood and adolescence. Variable presentation with subtle symptoms and signs can make diagnosis difficult.

CASE REPORT

We report the case of a 17-year-old girl referred for acne and progressive weight gain with an adrenocorticotropic hormone-independent CS. A computed tomography scan of the adrenals showed normal-sized adrenal glands with discrete bilateral shape irregularity. Bilateral adrenalectomy was performed and the histopathological findings were characteristic of primary pigmented nodular adrenocortical disease (PPNAD). Genetic analysis confirmed a germline mutation of the PRKAR1A gene. The same mutation was found in her sister, mother, and maternal grandfather. Endocrine tests showed that the sister of our patient also presented PPNAD requiring bilateral adrenalectomy and a similar histopathological pattern was observed. No other features of Carney complex was found among all affected members of the family.

CONCLUSION

It is exceptional for PPNAD to be an isolated phenomenon as well as being revealed by progressive weight gain in adolescence.