Double somatic mutations in CTNNB1 and GNA11 in an aldosterone-producing adenoma

Double somatic mutations in CTNNB1 and GNA11/Q have recently been identified in a small subset of aldosterone-producing adenomas (APAs). As a possible pathogenesis of APA due to these mutations, an association with pregnancy, menopause, or puberty has been proposed. However, because of its rarity, characteristics of APA with these mutations have not been well characterized. A 46-year-old Japanese woman presented with hypertension and hypokalemia. She had two pregnancies in the past but had no history of pregnancy-induced hypertension. She had regular menstrual cycle at presentation and was diagnosed as having primary aldosteronism after endocrinologic examinations. Computed tomography revealed a 2 cm right adrenal mass. Adrenal venous sampling demonstrated excess aldosterone production from the right adrenal gland. She underwent right laparoscopic adrenalectomy. The resected right adrenal tumor was histologically diagnosed as adrenocortical adenoma and subsequent immunohistochemistry (IHC) revealed diffuse immunoreactivity of aldosterone synthase (CYP11B2) and visinin like 1, a marker of the zona glomerulosa (ZG), whereas 11β-hydroxylase, a steroidogenic enzyme for cortisol biosynthesis, was mostly negative. CYP11B2 IHC-guided targeted next-generation sequencing identified somatic CTNNB1 (p.D32Y) and GNA11 (p.Q209H) mutations. Immunofluorescence staining of the tumor also revealed the presence of activated β-catenin, consistent with features of the normal ZG. The expression patterns of steroidogenic enzymes and related proteins indicated ZG features of the tumor cells. PA was clinically and biochemically cured after surgery. In conclusion, our study indicated that CTNNB1 and GNA11-mutated APA has characteristics of the ZG. The disease could occur in adults with no clear association with pregnancy or menopause.

Somatic SLC30A1 mutations altering zinc transporter ZnT1 cause aldosterone-producing adenomas and primary aldosteronism

Primary aldosteronism (PA) is the most common form of endocrine hypertension and is characterized by inappropriately elevated aldosterone production via a renin-independent mechanism. Driver somatic mutations for aldosterone excess have been found in approximately 90% of aldosterone-producing adenomas (APAs). Other causes of lateralized adrenal PA include aldosterone-producing nodules (APNs). Using next-generation sequencing, we identified recurrent in-frame deletions in SLC30A1 in four APAs and one APN (p.L51_A57del, n = 3; p.L49_L55del, n = 2). SLC30A1 encodes the ubiquitous zinc efflux transporter ZnT1 (zinc transporter 1). The identified SLC30A1 variants are situated close to the zinc-binding site (His43 and Asp47) in transmembrane domain II and probably cause abnormal ion transport. Cases of PA with SLC30A1 mutations showed male dominance and demonstrated increased aldosterone and 18-oxocortisol concentrations. Functional studies of the SLC30A151_57del variant in a doxycycline-inducible adrenal cell system revealed pathological Na+ influx. An aberrant Na+ current led to depolarization of the resting membrane potential and, thus, to the opening of voltage-gated calcium (Ca2+) channels. This resulted in an increase in cytosolic Ca2+ activity, which stimulated CYP11B2 mRNA expression and aldosterone production. Collectively, these data implicate zinc transporter alterations as a dominant driver of aldosterone excess in PA.

ACTH-independent production of 11-oxygenated androgens and glucocorticoids in an adrenocortical adenoma

SIGNIFICANCE STATEMENT

Due to its rarity, biochemical and histologic characteristics of androgen and glucocorticoid co-secreting adrenocortical adenomas are largely unknown. Herein, we report a case of adrenocortical adenoma that caused marked hyperandrogenemia and mild autonomous cortisol secretion. In this study, we investigated serum steroid profiles using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and histologic characteristics of the resected tumor. LC-MS/MS revealed highly elevated levels of 11-oxygenated androgens which have not been well studied in adrenal tumors. The expression patterns of steroidogenic enzymes determined by immunohistochemistry supported the results of steroid profiling and suggested the capacity of the tumor cells to produce 11-oxygenated androgens. Measurement of 11-oxygenated steroids should facilitate a better understanding of androgen-producing adrenocortical neoplasms.

Histopathology and Genetic Causes of Primary Aldosteronism in Young Adults

CONTEXT

Due to its rare incidence, molecular features of primary aldosteronism (PA) in young adults are largely unknown. Recently developed targeted mutational analysis identified aldosterone-driver somatic mutations in aldosterone-producing lesions, including aldosterone-producing adenomas (APAs), aldosterone-producing nodules (APNs), and aldosterone-producing micronodules, formerly known as aldosterone-producing cell clusters.

OBJECTIVE

To investigate histologic and genetic characteristics of lateralized PA in young adults.

METHODS

Formalin-fixed, paraffin-embedded adrenal tissue sections from 74 young patients with lateralized PA (<35 years old) were used for this study. Immunohistochemistry (IHC) for aldosterone synthase (CYP11B2) was performed to define the histopathologic diagnosis. Somatic mutations in aldosterone-producing lesions were further determined by CYP11B2 IHC-guided DNA sequencing.

RESULTS

Based on the CYP11B2 IHC results, histopathologic classification was made as follows: 48 APAs, 20 APNs, 2 multiple aldosterone-producing nodules (MAPN), 1 double APN, 1 APA with MAPN, and 2 nonfunctioning adenomas (NFAs). Of 45 APAs with successful sequencing, 43 (96%) had somatic mutations, with KCNJ5 mutations being the most common genetic cause of young-onset APA (35/45, 78%). Of 18 APNs with successful sequencing, all of them harbored somatic mutations, with CACNA1D mutations being the most frequent genetic alteration in young-onset APN (8/18, 44%). Multiple CYP11B2-expressing lesions in patients with MAPN showed several aldosterone-driver mutations. No somatic mutations were identified in NFAs.

CONCLUSION

APA is the most common histologic feature of lateralized PA in young adults. Somatic KCNJ5 mutations are common in APAs, whereas CACNA1D mutations are often seen in APNs in this young PA population.

Primary aldosteronism caused by a pI157S somatic KCNJ5 mutation in a black adolescent female with aldosterone-producing adenoma

Aldosterone-producing adenoma is a rare cause of hypertension in children. Only a limited number of cases of aldosterone-producing adenomas with somatic KCNJ5 gene mutations have been described in children. Blacks are particularly more susceptible to developing long-standing cardiovascular effects of aldosterone-induced severe hypertension. Somatic CACNA1D gene mutations are particularly more prevalent in black males whereas KCNJ5 gene mutations are most frequently present in black females. We present here a novel somatic KCNJ5 p.I157S mutation in an aldosterone-producing adenoma from a 16-year-old black female whose severe drug-resistant hypertension significantly improved following unilateral adrenalectomy. Prompt diagnosis of aldosterone-producing adenoma and early identification of gene mutation would enable appropriate therapy and significantly reduce cardiovascular sequelae.

The Age-Dependent Changes of the Human Adrenal Cortical Zones Are Not Congruent

BACKGROUND

While previous studies indicate that the zonae reticularis (ZR) and glomerulosa (ZG) diminish with aging, little is known about age-related transformations of the zona fasciculata (ZF).

OBJECTIVES

To investigate the morphological and functional changes of the adrenal cortex across adulthood, with emphasis on (i) the understudied ZF and (ii) sexual dimorphisms.

METHODS

We used immunohistochemistry to evaluate the expression of aldosterone synthase (CYP11B2), visinin-like protein 1 (VSNL1), 3β-hydroxysteroid dehydrogenase type II (HSD3B2), 11β-hydroxylase (CYP11B1), and cytochrome b5 type A (CYB5A) in adrenal glands from 60 adults (30 men), aged 18 to 86. Additionally, we employed mass spectrometry to quantify the morning serum concentrations of cortisol, 11-deoxycortisol (11dF), 17α-hydroxyprogesterone, 11-deoxycorticosterone, corticosterone, and androstenedione in 149 pairs of age- and body mass index-matched men and women, age 21 to 95 years.

RESULTS

The total cortical area was positively correlated with age (r = 0.34, P = 0.008). Both the total (VSNL1-positive) and functional ZG (CYP11B2-positive) areas declined with aging in men (r = -0.57 and -0.67, P < 0.01), but not in women. The CYB5A-positive area declined with age in both sexes (r = -0.76, P < 0.0001). In contrast, the estimated ZF area correlated positively with age in men (r = 0.59, P = 0.0006) and women (r = 0.49, P = 0.007), while CYP11B1-positive area remained unchanged across ages. Serum cortisol, corticosterone, and 11-deoxycorticosterone levels were stable across ages, while 11dF levels increased slightly with age (r = 0.16, P = 0.007).

CONCLUSION

Unlike the ZG and ZR, the ZF and the total adrenal cortex areas enlarge with aging. An abrupt decline of the ZG occurs with age in men only, possibly contributing to sexual dimorphism in cardiovascular risk.

Primary Cultures and Cell Lines for In Vitro Modeling of the Human Adrenal Cortex

The human adrenal cortex is a complex endocrine organ that produces mineralocorticoids, glucocorticoids and androgens. These steroids are produced in distinct cell types located within the glomerulosa, fasciculata and reticularis of the adrenal cortex. Abnormal adrenal steroidogenesis leads to a variety of diseases that can cause hypertension, metabolic syndrome, infertility and premature adrenarche. The adrenal cortex can also develop steroid-producing adenomas and rarely adrenocortical carcinomas. In vitro cell culture models provide important tools to study molecular and cellular mechanisms controlling both the physiologic and pathologic conditions of the adrenal cortex. In addition, the presence of multiple steroid-metabolizing enzymes within adrenal cells makes it a model for defining possible endocrine disruptors that might block these enzymes. The regulation and dysregulation of human adrenal steroid production and cell division/tumor growth can be studied using freshly isolated cells but this requires access to human adrenal glands, which are not available to most investigators. Immortalized human adrenocortical cell lines have proven to be of considerable value in studying the molecular and biochemical mechanisms controlling adrenal steroidogenesis and tumorigenesis. Current human adrenal cell lines include the original NCI-H295 and its substrains: H295A, H295R, HAC13, HAC15, HAC50 and H295RA as well as the recently established MUC-1, CU-ACC1 and CU-ACC2. The current review will discuss the use of primary cultures of fetal and adult adrenal cells as well as adrenocortical cell lines as in vitro models for the study of human adrenal physiology and pathophysiology.

Prevalence of Somatic Mutations in Aldosterone-Producing Adenomas in Japanese Patients

CONTEXT

Results of previous studies demonstrated clear racial differences in the prevalence of somatic mutations among patients with aldosterone-producing adenoma (APA). For instance, those in East Asian countries have a high prevalence of somatic mutations in KCNJ5, whereas somatic mutations in other aldosterone-driving genes are rare.

OBJECTIVES

To determine somatic mutation prevalence in Japanese APA patients using an aldosterone synthase (CYP11B2) immunohistochemistry (IHC)-guided sequencing approach.

METHOD

Patients with a unilateral form of primary aldosteronism who underwent adrenalectomy at the Tohoku University Hospital were studied. Based on CYP11B2 immunolocalization of resected adrenals, genomic DNA was isolated from the relevant positive area of 10% formalin-fixed, paraffin-embedded tissue of the APAs. Somatic mutations in aldosterone-driving genes were studied in APAs by direct Sanger sequencing and targeted next-generation sequencing.

RESULTS

CYP11B2 IHC-guided sequencing determined APA-related somatic mutations in 102 out of 106 APAs (96%). Somatic KCNJ5 mutation was the most frequent genetic alteration (73%) in this cohort of Japanese patients. Somatic mutations in other aldosterone-driving genes were also identified: CACNA1D (14%), ATP1A1 (5%), ATP2B3 (4%), and CACNA1H (1%), including 2 previously unreported mutations. KCNJ5 mutations were more often detected in APAs from female patients compared with those from male patients [95% (36/38) vs 60% (41/68); P < 0.0001].

CONCLUSION

IHC-guided sequencing defined somatic mutations in over 95% of Japanese APAs. While the dominance of KCNJ5 mutations in this particular cohort was confirmed, a significantly higher KCNJ5 prevalence was detected in female patients. This study provides a better understanding of genetic spectrum of Japanese APA patients.

Identification of Somatic Mutations in CLCN2 in Aldosterone-Producing Adenomas

Somatic mutations driving aldosterone production have been identified in approximately 90% of aldosterone-producing adenomas (APAs) using an aldosterone synthase (CYP11B2) immunohistochemistry (IHC)-guided DNA sequencing approach. In the present study, using CYP11B2-guided whole-exome sequencing (WES) and targeted amplicon sequencing, we detected 2 somatic variants in CLCN2 in 2 APAs that were negative for currently known aldosterone-driver mutations. The CLCN2 gene encodes the voltage-gated chloride channel ClC-2. CLCN2 germline variants have previously been shown to cause familial hyperaldosteronism type II. Somatic mutations in CLCN2 were identified in 2 of 115 APAs, resulting in a prevalence of 1.74%. One of the CLCN2 somatic mutations (c.G71A,p.G24D) was identical to a previously described germline variant causing early-onset PA, but was present only as a somatic mutation. The second CLCN2 mutation, which affects the same region of the gene, has not been reported previously (c.64-2_74del). These findings prove that WES of CYP11B2-guided mutation-negative APAs can help determine rarer genetic causes of sporadic PA.

SAT-554 Genetic Profile of Early-Onset Aldosterone-Producing Adenomas

Background: Aldosterone-producing adenoma (APA) is a major subtype of primary aldosteronism (PA) which is the most common cause of endocrine-related hypertension. The Endocrine Society clinical practice guideline suggests that young patients (< 35 years old) with a CT-detected adrenocortical adenoma and typical phenotype of PA may not need adrenal venous sampling prior to adrenalectomy. In recent years, aldosterone-driver somatic mutations have been identified in APA, and prevalence studies suggest potential effects of patient age and sex. However, the rare nature of early-onset PA has prevented a detailed study of the histologic characteristics and aldosterone-driver somatic mutations in adrenal tumors from these patients.

Objective: To determine histologic and somatic mutation profile in early-onset APA.

Methods: Fifty-five formalin-fixed paraffin-embedded (FFPE) adrenals from patients at the age of 35 years old or younger who underwent adrenalectomy at the participating centers were studied (45 women, 9 men, and 1 unknown sex). CYP11B2 immunohistochemistry (IHC)-guided tumor capturing was used to selectively obtain DNA from APA. Mutation status was determined either by Sanger sequencing or targeted next-generation sequencing.

Results: CYP11B2 IHC identified APAs in all adrenal specimens. Solitary APAs were found in 53 adrenals. One adrenal had multiple APAs and one had a dominant CYP11B2-negative tumor and a smaller APA. In total, DNA from 57 APAs were sequenced. Two APAs were excluded from the analysis due to low sample quality. In 52 of the 55 APAs, somatic mutations were identified in one of the aldosterone-driver genes or CTNNB1 gene, encoding β-catenin. The most common genetic alteration was seen in KCNJ5 (37/55, 67%), followed by CACNA1D (7/55, 13%), ATP1A1 (3/55, 5%), CTNNB1 (3/55, 5%), and ATP2B3 (2/55, 4%). No sex difference in the prevalence of KCNJ5 mutation was observed in this age group.

Conclusion: The majority of adrenals from early-onset PA patients had a solitary APA. Regardless of sex, the most common genetic cause of early-onset APA was somatic mutations in KCNJ5.

SAT-549 Identification of Somatic Mutations in CLCN2 as a Cause of Aldosterone-Producing Adenomas

Background: Primary aldosteronism (PA) results from both unilateral and bilateral adrenal disease. Unilateral disease is most often caused by aldosterone-producing adenomas (APAs). We recently identified aldosterone-driver somatic mutations in approximately 90% of APAs using an aldosterone synthase (CYP11B2) immunohistochemistry (IHC)-guided DNA sequencing approach. In the present study, we analyzed DNA from APA samples found to be mutation negative. Methods: Formalin-fixed paraffin-embedded tissue samples from PA patients who underwent adrenalectomy were studied. Genomic DNA was isolated from 118 APAs (identified by CYP11B2 IHC). Next generation sequencing (NGS) was performed to identify known aldosterone-driver mutations in KCNJ5, ATP1A1, ATP2B3, and CACNA1D. APA DNA that was mutation negative and the adjacent normal adrenal tissue DNA were subjected to Whole Exome Sequencing (WES). Results: Targeted NGS and WES detected two variants in the voltage-gated chloride channel ClC-2 (encoded by CLCN2), which were confirmed by Sanger sequencing. One of the CLCN2 mutations (p.Gly24Asp) was identical to that previously found to cause germline early-onset PA. The second CLCN2 mutation, which would affect the same region of the protein, was an unreported PA mutation (p.Met22fs). The presence of these variants in two tumors suggests that CLCN2 mutations as a cause of APAs are rare with an approximate prevalence of 1.7% (2/118 APAs). Conclusion: In this study, we identified somatic mutations in CLCN2, in two of 118 APAs. Germline variants in this gene have previously been shown to cause of familial hyperaldosteronism type II and the current findings indicate that similar mutations cause a small proportion of APAs. These findings also indicate that WES of CYP11B2-guided mutation negative APAs can help determine rarer genetic causes of sporadic PA.

Somatic CACNA1H Mutation As a Cause of Aldosterone-Producing Adenoma

Driver somatic mutations for aldosterone excess have been found in ≈90% of aldosterone-producing adenomas (APAs) using an aldosterone synthase (CYP11B2)-guided sequencing approach. In the present study, we identified a novel somatic CACNA1H mutation (c.T4289C, p.I1430T) in an APA without any currently known aldosterone-driver mutations using CYP11B2 immunohistochemistry-guided whole exome sequencing. The CACNA1H gene encodes a voltage-dependent T-type calcium channel alpha-1H subunit. Germline variants in this gene are known as a cause of familial hyperaldosteronism IV. Targeted next-generation sequencing detected identical CACNA1H variants in 2 additional APAs in a cohort of the University of Michigan, resulting in a prevalence of 4% (3/75) in APAs. We tested the functional effect of the variant on adrenal cell aldosterone production and CYP11B2 mRNA expression using the human adrenocortical HAC15 cell line with a doxycycline-inducible CACNA1H^I1430T mutation. Doxycycline treatment increased CYP11B2 mRNA levels as well as aldosterone production, supporting a pathological role of the CACNA1H p.I1430T mutation on the development of primary aldosteronism. In conclusion, somatic CACNA1H mutation is a genetic cause of APAs. Although the prevalence of this mutation is low, this study will provide better understanding of molecular mechanism of inappropriate aldosterone production in APAs.

Genetics of aldosterone-producing adenomas with pathogenic KCNJ5 variants

Somatic variants in genes that regulate intracellular ion homeostasis have been identified in aldosterone-producing adenomas (APA). Although the mechanisms leading to an increased aldosterone production in APA cells has been well studied, the molecular events that cause cell proliferation and tumor formation are poorly understood. In the present study, we have performed whole exome sequencing (WES) to characterize the landscape of somatic alterations in a homogeneous series of APA with pathogenic KCNJ5 variants. In the WES analysis on eleven APA, 84 exonic somatic events were called by 3 different somatic callers. Besides the KCNJ5 gene, only two genes (MED13 and ZNF669) harbored somatic variants in more than one APA. Unlike adrenocortical carcinomas, no chromosomal instability was observed by the somatic copy-number alteration and loss of heterozygosity analyses. The estimated tumor purity ranged from 0.35 to 0.67, suggesting a significant proportion of normal cell infiltration. Based on the results of PureCN analysis, the KCNJ5 variants appear to be clonal. In conclusion, in addition to KCNJ5 somatic pathogenic variant, no significant somatic event that would obviously explain proliferation or tumor growth was observed in our homogeneous cohort of KCNJ5-mutated APA. The molecular mechanisms causing APA growth and tumorigenesis remain to be elucidated.