3β-Hydroxysteroid dehydrogenase isoforms in human aldosterone-producing adenoma

Functional interaction of Clock genes and bone morphogenetic proteins in the adrenal cortex

The bone morphogenetic protein (BMP) system in the adrenal cortex plays modulatory roles in the control of adrenocortical steroidogenesis. BMP-6 enhances aldosterone production by modulating angiotensin (Ang) II-mitogen-activated protein kinase (MAPK) signaling, whereas activin regulates the adrenocorticotropin (ACTH)-cAMP cascade in adrenocortical cells. A peripheral clock system in the adrenal cortex was discovered and it has been shown to have functional roles in the adjustment of adrenocortical steroidogenesis by interacting with the BMP system. It was found that follistatin, a binding protein of activin, increased Clock mRNA levels, indicating an endogenous function of activin in the regulation of Clock mRNA expression. Elucidation of the interrelationships among the circadian clock system, the BMP system and adrenocortical steroidogenesis regulated by the hypothalamic-pituitary-adrenal (HPA) axis would lead to an understanding of the pathophysiology of adrenal disorders and metabolic disorders and the establishment of better medical treatment from the viewpoint of pharmacokinetics.

Histopathologic Features of Adrenal Cortical Carcinoma

Adrenal cortical carcinoma (ACC) is a rare and aggressive malignancy that poses challenging issues regarding the diagnostic workup. Indeed, no presurgical technique or clinical parameters can reliably distinguish between adrenal cortical adenomas, which are more frequent and have a favorable outcome, and ACC, and the final diagnosis largely relies on histopathologic analysis of the surgical specimen. However, even the pathologic assessment of malignancy in an adrenal cortical lesion is not straightforward and requires a combined evaluation of multiple histopathologic features. Starting from the Weiss score, which was developed in 1984, several histopathologic scoring systems have been designed to tackle the difficulties of ACC diagnosis. Dealing with specific histopathologic variants (eg, Liss-Weiss-Bisceglia scoring system for oncocytic ACC) or patient characteristics (eg, Wieneke index in the pediatric setting), these scores remarkably improved the diagnostic workup of ACC and its subtypes. Nevertheless, cases with misleading features or discordant correlations between pathologic findings and clinical behavior still occur. Owing to multicentric collaborative studies integrating morphologic features with ancillary immunohistochemical markers and molecular analysis, ACC has eventually emerged as a multifaceted, heterogenous malignancy, and, while innovative and promising approaches are currently being tested, the future clinical management of patients with ACC will mainly rely on personalized medicine and target-therapy protocols. At the dawn of the new Fifth World Health Organization classification of endocrine tumors, this review will tackle ACC from the pathologist's perspective, thus focusing on the main available diagnostic, prognostic, and predictive tissue-tethered features and biomarkers and providing relevant clinical and molecular correlates.

Phenotype-genotype correlation in aldosterone-producing adenomas characterized by intracellular cholesterol metabolism

Aldosterone-producing adenoma (APA) is histologically composed of clear and compact tumor cells. KCNJ5- mutated APAs were reported to be associated with higher plasma aldosterone concentration and more abundant clear tumor cells containing lipid droplets than non-KCNJ5- mutated APAs. However, the association among cholesterol uptake and/or synthesis, cellular morphology and genotypes has remained unknown. Therefore, in order to explore these differences, 52 APA cases (KCNJ5 mt: n = 33, non-KCNJ5 mt: n = 19; ATP1A1: n = 3, ATP2B3: n = 3, CACNA1D: n = 5, CTNNB1: n = 1, tumors without any mutation above: n = 7), zona glomerulosa (ZG) tissue adjacent to APA and 10 non-pathological adrenal glands (NAs) were examined for quantitative histopathological analysis of tumor morphology and immunohistochemical analysis of cholesterol receptors (SR-B1, LDL-R), cholesterol metabolic enzymes (ACAT1, ACAT2, HSL, DHCR24, StAR), and the enzymes required for steroid synthesis (CYP11A1, CYP17A, 3βHSD, CYP11B1, CYP11B2). Gas chromatography-mass spectrometry (GC-MS) analysis was further performed to profile cholesterol precursors and metabolites in 21 APA cases (KCNJ5 mt: n = 16, non-KCNJ5 mt: n = 5) and 14 adrenal cortex of adjacent adrenal tissues. Results demonstrated that both SR-B1 and DHCR24 were significantly lower in the ZG than in fasciculata or reticularis of NAs but LDL-R was not significantly different among them in immunohistochemical analysis. SR-B1 and DHCR24 were both significantly higher in APAs than in ZG tissue adjacent to APA. In GC-MS analysis, most cholesterol precursors and metabolites, except for lanosterol, and their metabolic ratios (= concentration of cholesterol/ precursor) were higher in APAs than in the adjacent adrenal cortex tissue. LDL-R, ACAT1/2, HSL, DHCR24 were all significantly lower in clear than in compact tumor cells of APA. LDL-R was significantly lower and cholesterol/lanosterol ratio was significantly higher in KCNJ5- mutated than non-KCNJ5- mutated APAs. We demonstrated SR-B1 mediated selective uptake of cholesterol ester and de novo cholesterol synthesis were both enhanced in APAs. In addition, cholesterol uptake and metabolism were different between clear and compact tumor cells. KCNJ5- mutated APAs were predominantly composed of clear tumor cells containing abundant cholesteryl ester but less activated LDL-R mediated uptake and increased de novo synthesis. Those findings above indicated their more pronounced functional deviation from the normal ZG cells in terms of their steroidogenic and intracellular cholesterol metabolism.

Visualization of calcium channel blockers in human adrenal tissues and their possible effects on steroidogenesis in the patients with primary aldosteronism (PA)

Voltage-gated L-type calcium channel (CaV) isoforms are well known to play pivotal tissue-specific roles not only in vasoconstriction but also in adrenocortical steroidogenesis including aldosterone biosynthesis. Alpha-1C subunit calcium channel (CC) (CaV1.2) is the specific target of anti-hypertensive CC blockers (CCBs) and its Alpha-1D subunit (CaV1.3) regulates depolarization of cell membrane in aldosterone-producing cells. Direct effects of CCBs on aldosterone biosynthesis were previously postulated but their intra-adrenal distribution and effects on steroid production in primary aldosteronism (PA) patients have remained virtually unknown. In this study, frozen tissue specimens constituting tumor, adjacent adrenal gland and peri-adrenal adipose tissues of nine aldosterone-producing adenoma (APA) cases were examined for visualization of amlodipine and aldosterone themselves using matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI). Liquid chromatography-mass spectrometry (LC-MS) analysis was also performed to quantify amlodipine and 17 adrenal steroids in those cases above and compared the findings with immunohistochemical analysis of steroidogenic enzymes and calcium channels (CaV1.2 and CaV1.3). Effects of amlodipine on mRNA level of aldosterone biosynthetic enzymes were also explored using human adrenocortical carcinoma cell line (H295R). Amlodipine-specific peak (m/z 407.1 > 318.1) was detected only in amlodipine treated cases. Accumulation of amlodipine was marked in adrenal cortex compared to peri-adrenal adipose tissues but not significantly different between APA tumors and adjacent adrenal glands, which was subsequently confirmed by LC-MS quantification. Intra-adrenal distribution of amlodipine was generally consistent with that of CCs. In addition, quantitative steroid profiles using LC-MS and in vitro study demonstrated the lower HSD3B activities in amlodipine treated cases. Immunoreactivity of CaV1.2 and HSD3B2 were also correlated. We report the first demonstration of specific visualization of amlodipine in human adrenal tissues by MALDI-MSI. Marked amlodipine accumulation in the adrenal glands suggested its direct effects on steroidogenesis in PA patients, possibly targeting on CaV1.2 and suppressing HSD3B activity.

The Association of Cholesterol Uptake and Synthesis with Histology and Genotype in Cortisol-Producing Adenoma (CPA)

Cortisol-producing adenoma (CPA) is composed of clear and compact cells. Clear cells are lipid abundant, and compact ones lipid poor but associated with higher production of steroid hormones. PRKACA mutation (PRKACA mt) in CPA patients was reported to be associated with more pronounced clinical manifestation of Cushing's syndrome. In this study, we examined the association of histological features and genotypes with cholesterol uptake receptors and synthetic enzymes in 40 CPA cases, and with the quantitative results obtained by gas chromatography-mass spectrometry (GC-MS) analysis in 33 cases to explore their biological and clinical significance. Both cholesterol uptake receptors and synthetic enzymes were more abundant in compact cells. GC-MS analysis demonstrated that the percentage of compact cells was inversely correlated with the concentrations of cholesterol and cholesterol esters, and positively with the activity of cholesterol biosynthesis from cholesterol esters. In addition, hormone-sensitive lipase (HSL), which catalyzes cholesterol biosynthesis from cholesterol esters, tended to be more abundant in compact cells of PRKACA mt CPAs. These results demonstrated that both cholesterol uptake and biosynthesis were more pronounced in compact cells in CPA. In addition, more pronounced HSL expression in compact cells of PRKACA mt CPA could contribute to their more pronounced clinical manifestation.

The role of mineralocorticoids and glucocorticoids under the impact of 11β-hydroxysteroid dehydrogenase in human breast lesions

We attempted to explore the possible involvement of the in situ availability of mineralocorticoids and mineralocorticoid receptor (MR) in the pathogenesis of mammary ductal carcinoma. We also explored their individual profiles among different subtypes of invasive ductal carcinomas of no special type (IDC-NST) by evaluating the status of MR, Glucocorticoid receptor (GR), and 11β hydroxysteroid dehydrogenase (HSD) 1/2 at each stage of the putative cascade of the mammary ductal proliferative disorders. In this study, IDC-NST, ductal carcinoma in situ (DCIS), atypical ductal hyperplasia (ADH), and non-pathological breast tissues were all evaluated by immunohistochemistry. MR was significantly lower in ADH than in DCIS or IDC-NST. 11βHSD2 was significantly lower in ADH than normal breast tissue and 11βHSD1 was significantly higher in DCIS than normal, ADH, or IDC-NST. MR in progesterone receptor (PR)-positive IDC-NST cases tended to be associated with the Ki-67 labeling index. Results of the present study demonstrated that the status of MR and GR in conjunction with the 11βHSDs was correlated with the development of low-grade proliferative disorders in mammary glands. In addition, the potential crosstalk between MR and PR could also influence cell proliferation of breast carcinoma cells but further investigations are required for clarification.

Molecular Mechanisms of Functional Adrenocortical Adenoma and Carcinoma: Genetic Characterization and Intracellular Signaling Pathway

The adrenal cortex produces steroid hormones as adrenocortical hormones in the body, secreting mineralocorticoids, glucocorticoids, and adrenal androgens, which are all considered essential for life. Adrenocortical tumors harbor divergent hormonal activity, frequently with steroid excess, and disrupt homeostasis of the body. Aldosterone-producing adenomas (APAs) cause primary aldosteronism (PA), and cortisol-producing adenomas (CPAs) are the primary cause of Cushing’s syndrome. In addition, adrenocortical carcinoma (ACC) is a highly malignant cancer harboring poor prognosis. Various genetic abnormalities have been reported, which are associated with possible pathogenesis by the alteration of intracellular signaling and activation of transcription factors. In particular, somatic mutations in APAs have been detected in genes encoding membrane proteins, especially ion channels, resulting in hypersecretion of aldosterone due to activation of intracellular calcium signaling. In addition, somatic mutations have been detected in those encoding cAMP-PKA signaling-related factors, resulting in hypersecretion of cortisol due to its driven status in CPAs. In ACC, mutations in tumor suppressor genes and Wnt-β-catenin signaling-related factors have been implicated in its pathogenesis. In this article, we review recent findings on the genetic characteristics and regulation of intracellular signaling and transcription factors in individual tumors.

Cellular Senescence in Human Aldosterone-Producing Adrenocortical Cells and Related Disorders

In situ cortisol excess was previously reported to promote cellular senescence, a cell response to stress, in cortisol-producing adenomas (CPA). The aim of this study was to explore senescence pathways in aldosterone-producing cells and related disorders, and the influence of aldosterone overproduction on in situ senescence. We analyzed 30 surgical cases of aldosterone-producing adenoma (APA), 10 idiopathic hyperaldosteronism (IHA) and 19 normal adrenals (NA). CYP11B2 and senescence markers p16 and p21 were immunolocalized in all those cases above and results were correlated with histological/endocrinological findings. In the three cohorts examined, the zona glomerulosa (ZG) was significantly more senescent than other corticosteroid-producing cells. In addition, the ZG of adjacent non-pathological adrenal glands of APA and IHA had significantly higher p16 expression than adjacent non-pathological zona fasciculata (ZF), reticularis (ZR) and ZG of NA. In addition, laboratory findings of primary aldosteronism (PA) were significantly correlated with p21 status in KCNJ5-mutated tumors. Results of our present study firstly demonstrated that non-aldosterone-producing cells in the ZG were the most senescent compared to other cortical zones and aldosterone-producing cells in PA. Therefore, aldosterone production, whether physiological or pathological, could be maintained by suppression of cell senescence in human adrenal cortex.

Recent Development toward the Next Clinical Practice of Primary Aldosteronism: A Literature Review

For the last seven decades, primary aldosteronism (PA) has been gradually recognized as a leading cause of secondary hypertension harboring increased risks of cardiovascular incidents compared to essential hypertension. Clinically, PA consists of two major subtypes, surgically curable and uncurable phenotypes, determined as unilateral or bilateral PA by adrenal venous sampling. In order to further optimize the treatment, surgery or medications, diagnostic procedures from screening to subtype differentiation is indispensable, while in the general clinical practice, the work-up rate is extremely low even in the patients with refractory hypertension because of the time-consuming and labor-intensive nature of the procedures. Therefore, a novel tool to simplify the diagnostic flow has been recently in enormous demand. In this review, we focus on recent progress in the following clinically important topics of PA: prevalence of PA and its subtypes, newly revealed histopathological classification of aldosterone-producing lesions, novel diagnostic biomarkers and prediction scores. More effective strategy to diagnose PA based on better understanding of its epidemiology and pathology should lead to early detection of PA and could decrease the cardiovascular and renal complications of the patients.

Intratumoral heterogeneity of the tumor cells based on in situ cortisol excess in cortisol-producing adenomas; ∼An association among morphometry, genotype and cellular senescence∼

Cortisol-producing adrenocortical adenomas (CPAs) are associated with ACTH-independent Cushing's syndrome and histologically composed of two cellular subtypes: compact (lipid-poor) and clear (lipid-rich) tumor cells. However, the details of hormonal and biological activities of these tumor cells have remained unknown, especially in CPAs. CPAs frequently harbored unique histological features different from those of aldosterone-producing adenomas (APAs) including a senescent phenotype. Therefore, we explored the association between morphological features and the immunoreactivity of steroidogenic enzymes in CPAs with different genotypes and compared them with cellular senescence markers as well as clinicopathological factors of the cases. Hormonal activities (3βHSD, CYP21A, CYP17A1, CYP11B1 and DHEA-ST) and cellular senescence markers (p16, p21 and Ki-67) within different morphological features (clear and compact) were evaluated in 40 CPAs. CPA genotypes (PRKACA, GNAS and CTNNB1) were examined by Sanger sequencing and then compared them with the factors above. p21 immunoreactivity was significantly positively correlated with that of CYP21A (p = 0.0110), CYP17A1 (p = 0.0356) and DHEA-ST (p = 0.0420) but inversely with tumor size (p = 0.0015). CYP21A (p = 0.0016), CYP11B1 (p = 0.0001), CYP17A1 (p < 0.0001) and p16 (p = 0.0137) immunoreactivity were all significantly higher in compact cells than those in clear cells. CYP17A1 (p = 0.0056) and 3βHSD (p = 0.0437) immunoreactivity was significantly higher in PRKACA-mutated than wild type CPAs. p16 immunoreactivity and serum DHEA-S level were both significantly higher in GNAS-mutated than PRKACA-mutated (p = 0.0250) and wild type (p = 0.0180) CPAs. Results of our present study did demonstrate that compact tumor cells were hormonally active and more senescent than clear tumor cells in CPAs. PRKACA- and GNAS-mutated tumor cells were more hormonally active and senescent than those without mutations despite the similar morphological features. We herein proposed a novel histological classification of the tumor cell subtypes based on in situ cortisol excess, genotypes and the status of cell senescence in CPAs.

Histological Characterization of Aldosterone-producing Adrenocortical Adenomas with Different Somatic Mutations

CONTEXT

Aldosterone-producing adrenocortical adenomas (APAs) are mainly composed of clear (lipid rich) and compact (eosinophilic) tumor cells. The detailed association between these histological features and somatic mutations (KCNJ5, ATP1A1, ATP2B3, and CACNA1D) in APAs is unknown.

OBJECTIVE

To examine the association between histological features and individual genotypes in APAs.

METHODS

Examination of 39 APAs subjected to targeted next-generation sequencing (11 KCNJ5, 10 ATP1A1, 10 ATP2B3, and 8 CACNA1D) and quantitative morphological and immunohistochemical (CYP11B2 and CYP17A1) analyses using digital imaging software.

RESULTS

KCNJ5- and ATP2B3-mutated APAs had clear cell dominant features (KCNJ5: clear 59.8% [54.4-64.6%] vs compact 40.2% (35.4-45.6%), P = .0022; ATP2B3: clear 54.3% [48.2-62.4 %] vs compact 45.7% (37.6-51.8 %), P = .0696). ATP1A1- and CACNA1D-mutated APAs presented with marked intratumoral heterogeneity. A significantly positive correlation of immunoreactivity was detected between CYP11B2 and CYP17A1 in tumor cells of KCNJ5-mutated APAs (P = .0112; ρ = 0.7237), in contrast, significantly inverse correlation was detected in ATP1A1-mutated APAs (P = .0025; ρ = -0.8667).

CONCLUSION

KCNJ5-mutated APAs, coexpressing CYP11B2 and CYP17A1, were more deviated in terms of zonation-specific differentiation of adrenocortical cells than ATP1A1- and ATP2B3-mutated APAs.

Histopathological Analysis of Tumor Microenvironment and Angiogenesis in Pheochromocytoma

Pheochromocytomas (PHEOs) are relatively rare catecholamine-producing tumors derived from adrenal medulla. Tumor microenvironment (TME) including neoangiogenesis has been explored in many human neoplasms but not necessarily in PHEOs. Therefore, in this study, we examined tumor infiltrating lymphocytes (CD4 and CD8), tumor associated macrophages (CD68 and CD163), sustentacular cells (S100p), and angiogenic markers (CD31 and areas of intratumoral hemorrhage) in 39 cases of PHEOs in the quantitative fashion. We then compared the results with pheochromocytoma of the adrenal gland scaled score (PASS), grading system for pheochromocytoma and paraganglioma (GAPP) and the status of intra-tumoral catecholamine-synthesizing enzymes (TH, DDC, and PNMT) as well as their clinicopathological factors. Intratumoral CD8 (p = 0.0256), CD31 (p = 0.0400), and PNMT (p = 0.0498) status was significantly higher in PHEOs with PASS <4 than PASS ≧4. In addition, intratumoral CD8⁺ lymphocytes were also significantly more abundant in well-than moderately differentiated PHEO according to GAPP score (p = 0.0108) and inversely correlated with tumor size (p = 0.0257). Intratumoral CD68⁺ cells were significantly higher in PHEOs with regular or normal histological patterns than those not (p = 0.0370) and inversely correlated with tumor size (p = 0.0457). The status of CD163 was significantly positively correlated with that of CD8 positive cells (p = 0.0032). The proportion of intratumoral hemorrhage areas was significantly higher in PHEOs with PASS ≧4 (p = 0.0172). DDC immunoreactivity in tumor cells was significantly positively correlated with PASS score (p = 0.0356) and TH status was significantly higher in PHEOs harboring normal histological patterns (p = 0.0236) and cellular monotony (p = 0.0219) than those not. Results of our present study did demonstrate that abundant CD8⁺ and CD68⁺ cells could represent a histologically low-scored tumor. In particular, PHEOs with increased intratumoral hemorrhage should be considered rather malignant. In addition, abnormal catecholamine-producing status of tumor cells such as deficient PNMT and TH and increased DDC could also represent more aggressive PHEOs.

The crosstalk between aldosterone and calcium metabolism in primary aldosteronism: A possible calcium metabolism-associated aberrant "neoplastic" steroidogenesis in adrenals

Intracellular calcium (Ca) levels play pivotal roles in aldosterone biosynthesis. Several somatic mutations of ion channels associated with aldosterone over-production were reported to result in over-inflow of Ca ion. Recently, the main regulators of extracellular Ca including VDR, CaSR and PTH1R were also reported to regulate steroidogenesis including aldosterone production. Therefore, not only intracellular but also extracellular Ca levels could regulate aldosterone biosynthesis. In addition, primary aldosteronism (PA) is clinically associated with not only more frequent cardiovascular events but also secondary metabolic disorders including abnormal calcium metabolism, osteoporosis and others. However, the details of Ca metabolic abnormalities associated with, including the potential correlation between those abnormalities and aldosterone overproduction, have remained virtually unknown. Therefore, in this study, we first immunolocalized Ca metabolism-related receptors (CaSR, VDR and PTH1R) in normal adrenal glands (NAs), aldosterone-producing adenomas (APAs) and cortisol-producing adenoma (CPA). We then compared the findings with clinicopathological parameters of these patients and the patterns of KCNJ5 somatic mutation of the tumors among APA patients. In vitro study was also performed to further explore the potential effects of extracellular Ca, PTH, Vitamin D and ionophore on aldosterone production. Ca metabolism-related receptors were predominantly localized in aldosterone-producing cells (ZG and APA) in both immunohistochemistry and qRT-PCR analysis. CYP11B2 mRNA was significantly increased by CaCl₂ treatment and further by adding ionophore. All the key enzymes related to aldosterone and cortisol biosynthesis including CYP11B2, CYP17A1 and CYP11B1 were upregulated by PTH treatment in this model and PTH could serve as a co-stimulator of ANG II to increase CYP11B2 expression. VDR mRNA levels were positively correlated with those of CYP11B2, CYP17A1 and CYP11B1 in APA tumor tissues and significantly higher in KCNJ5 mutated APAs than wild type. CYP11B1 levels were also significantly increased by VitD treatment. PTH1R mRNA levels were positively correlated with those of CYP17A1 and CYP11B1, both involved in cortisol production. In addition, the status of VDR was correlated with TRACP-5b levels, and that of PTH1R with serum Ca levels as well as urinary Ca excretion, respectively. Results of our present study did firstly demonstrate that aldosterone-producing cells were more sensitive to the fluctuations of extracellular Ca levels and Ca metabolism could directly influence steroidogenesis, especially "neoplastic" co-secretion of aldosterone and cortisol in APA patients.

Clock genes and cancer development in particular in endocrine tissues

Circadian rhythms at a central and peripheral level are operated by transcriptional/translational feedback loops involving a set of genes called 'clock genes' that have been implicated in the development of several diseases, including malignancies. Dysregulation of the Clock system can influence cancer susceptibility by regulating DNA damage and repair mechanisms, as well as apoptosis. A number of oncogenic pathways can be dysregulated via clock genes' epigenetic alterations, including hypermethylation of clock genes' promoters or variants of clock genes. Clock gene disruption has been studied in breast, lung and prostate cancer, and haematological malignancies. However, it is still not entirely clear whether clock gene disruption is the cause or the consequence of tumourigenesis and data in endocrine neoplasms are scarce. Recent findings suggest that clock genes are implicated in benign and malignant adrenocortical neoplasias. They have been also associated with follicular and papillary thyroid carcinomas and parathyroid adenomas, as well as pituitary adenomas and craniopharyngiomas. Dysregulation of clock genes is also encountered in ovarian and testicular tumours and may also be related with their susceptibility to chemotherapeutic agents. The most common clock genes that are implicated in endocrine neoplasms are PER1, CRY1; in most cases their expression is downregulated in tumoural compared to normal tissues. Although there is still a lot to be done for the better understanding of the role of clock genes in endocrine tumourigenenesis, existing evidence could guide research and help identify novel therapeutic targets aiming mainly at the peripheral components of the clock gene system.

Tumor Cell Subtypes Based on the Intracellular Hormonal Activity in KCNJ5-Mutated Aldosterone-Producing Adenoma

Aldosterone-producing adenomas (APAs) harbor marked intratumoral heterogeneity in terms of morphology, steroidogenesis, and genetics. However, an association of biological significance of morphologically identified tumor cell subtypes and genotypes is virtually unknown. KCNJ5 mutation is most frequently detected and generally considered a curable phenotype by adrenalectomy. Therefore, to explore the biological significance of KCNJ5 mutation in APA based on intracellular hormonal activities, 35 consecutively selected APAs (n=18; KCNJ5 mutated, n=17; wild type) were quantitatively examined in the whole tumor areas by newly developed digital image analysis incorporating their histological and ultrastructural features (14 cells from 2 KCNJ5-mutated APAs and 15 cells from 1 wild type) and CYP11B2 immunoreactivity. Results demonstrated that KCNJ5-mutated APAs had significantly lower nuclear/cytoplasm ratio and more abundant clear cells than wild type. CYP11B2 immunoreactivity was not significantly different between these genotypes, but a significant correlation was detected between the proportion of clear cells and CYP11B2 immunoreactivity in all of the APAs examined. CYP11B2 was predominantly immunolocalized in clear cells in KCNJ5-mutated APAs. Quantitative ultrastructural analysis revealed that KCNJ5-mutated APAs had significantly more abundant and smaller-sized mitochondria with well-developed cristae than wild type, whereas wild type had more abundant lipid droplets per unit area despite the small number of the cases examined. Our results did provide the novel insights into the morphological features of APA based on their biological significance. KCNJ5-mutated APAs were characterized by predominance of enlarged lipid-rich clear cells possibly resulting in increased neoplastic aldosterone biosynthesis.

Role of Cryptochrome-1 and Cryptochrome-2 in Aldosterone-Producing Adenomas and Adrenocortical Cells

Mice lacking the core-clock components, cryptochrome-1 (CRY1) and cryptochrome-2 (CRY2) display a phenotype of hyperaldosteronism, due to the upregulation of type VI 3β-hydroxyl-steroid dehydrogenase (Hsd3b6), the murine counterpart to the human type I 3β-hydroxyl-steroid dehydrogenase (HSD3B1) gene. In the present study, we evaluated the role of CRY1 and CRY2 genes, and their potential interplay with HSD3B isoforms in adrenal pathophysiology in man. Forty-six sporadic aldosterone-producing adenomas (APAs) and 20 paired adrenal samples were included, with the human adrenocortical cells HAC15 used as the in vitro model. In our cohort of sporadic APAs, CRY1 expression was 1.7-fold [0.75–2.26] higher (p = 0.016), while CRY2 showed a 20% lower expression [0.80, 0.52–1.08] (p = 0.04) in APAs when compared with the corresponding adjacent adrenal cortex. Type II 3β-hydroxyl-steroid dehydrogenase (HSD3B2) was 317-fold [200–573] more expressed than HSD3B1, and is the main HSD3B isoform in APAs. Both dehydrogenases were more expressed in APAs when compared with the adjacent cortex (5.7-fold and 3.5-fold, respectively, p < 0.001 and p = 0.001) and HSD3B1 was significantly more expressed in APAs composed mainly of zona glomerulosa-like cells. Treatment with angiotensin II (AngII) resulted in a significant upregulation of CRY1 (1.7 ± 0.25-fold, p < 0.001) at 6 h, and downregulation of CRY2 at 12 h (0.6 ± 0.1-fold, p < 0.001), through activation of the AngII type 1 receptor. Independent silencing of CRY1 and CRY2 genes in HAC15 cells resulted in a mild upregulation of HSD3B2 without affecting HSD3B1 expression. In conclusion, our results support the hypothesis that CRY1 and CRY2, being AngII-regulated genes, and showing a differential expression in APAs when compared with the adjacent adrenal cortex, might be involved in adrenal cell function, and in the regulation of aldosterone production.

Immunohistochemical Biomarkers of Adrenal Cortical Neoplasms

Careful morphological evaluation forms the basis of the workup of an adrenal cortical neoplasm. However, the adoption of immunohistochemical biomarkers has added tremendous value to enhance diagnostic accuracy. The authors provide a brief review of immunohistochemical biomarkers that have been used in the confirmation of adrenal cortical origin and in the detection of the source of functional adrenal cortical proliferations, as well as diagnostic, predictive, and prognostic biomarkers of adrenal cortical carcinoma. In addition, a brief section on potential novel theranostic biomarkers in the prediction of treatment response to mitotane and other relevant chemotherapeutic agents is also provided. In the era of precision and personalized medical practice, adoption of combined morphology and immunohistochemistry provides a new approach to the diagnostic workup of adrenal cortical neoplasms, reflecting the evolution of clinical responsibility of pathologists.

Tumor microenvironment in functional adrenocortical adenomas: immune cell infiltration in cortisol-producing adrenocortical adenoma

The tumor microenvironment plays pivotal roles in various human neoplasms. However, that of benign tumor, particularly hormone-secreting endocrine tumors, has remained virtually unknown. Therefore, we firstly attempted to analyze the tumor microenvironment of autonomous hormone-secreting adrenocortical adenomas. We first histologically evaluated 21 cortisol-producing adrenocortical adenoma (CPA) and 13 aldosterone-producing adrenocortical adenoma (APA) cases. Quantitative histologic analysis revealed that intratumoral immune cell infiltration (ICI) was more pronounced in CPAs than in APAs. We then evaluated the cytokine and chemokine profiles using polymerase chain reaction arrays in APAs and CPAs. Angiogenic chemokines, C-X-C motif chemokine ligand (CXCL) 1 and CXCL2, were significantly more abundant in CPAs than in APAs using subsequent quantitative polymerase chain reaction and immunohistochemical analyses. We then examined the vascular density between these 2 adenomas, and the density was significantly higher in overt CPAs than in APAs. Of particular interest, CXCL12-positive vessels were detected predominantly in CPAs, and their infiltrating immune cells were C-X-C motif chemokine receptor 4 (CXCR4) positive. These results above indicated that CXCL12-CXCR4 signaling could partly account for ICI detected predominantly in CPAs. We then further explored the etiology of ICI in CPAs by evaluating the senescence of tumor cells possibly caused by excessive cortisol in CPAs. The status of senescence markers, p16 and p21, was significantly more abundant in CPAs than in APAs. In addition, all CPA cases examined were positive for senescence-associated β-galactosidase. These results all indicated that exposure to local excessive cortisol could result in senescence of tumors cells and play essential roles in constituting the characteristic tissue microenvironment of CPAs.

Development of monoclonal antibodies against the human 3β-hydroxysteroid dehydrogenase/isomerase isozymes

The human 3β-hydroxysteroid dehydrogenase/isomerase (HSD3B) enzymes catalyze the conversion of 3β-hydroxy Δ5-6 steroids into 3-keto Δ4-5 steroids, which is required for the synthesis of the mature steroid hormones secreted by the adrenal and gonads. The human has 2 isozymes, the HSD3B1 that is traditionally located in placenta and extra-adrenal tissues and the HSD3B2 that is expressed in the adrenal and gonads. Mice with both cryptochrome 1 and 2 genes deletion were recently found to have salt-sensitive hypertension and hyperaldosteronism. These deletions were also associated with overexpression of the Hsd3b6 enzyme, the homolog of the human HSD3B1, in the zona glomerulosa which was believed to explain the hyperaldosteronism. A report using antibodies against human HSD3B1 suggested that it was expressed in the zona glomerulosa of normal human adrenals and in patients with idiopathic hyperaldosteronism and the HSD3B2 expressed in both the zona fasciculata and glomerulosa. We have developed specific monoclonal antibodies against the human HSD3B1 and HSD3B2 isozymes and found that the main enzyme expressed in the zona glomerulosa was the HSD3B2. Faint staining of the adrenal was also obtained using the anti-HSD3B1antibody only at high concentrations of antibody. This study fails to confirm that HSD3B1 expression in the human zona glomerulosa and double immunofluorescence clearly shows that the HSD3B2 is expressed in the zona glomerulosa and fasciculata and in the zona glomerulosa HSD3B2 is co-expressed with aldosterone synthase (CYP11B2).

Expression of CYP11B2 in Aldosterone-Producing Adrenocortical Adenoma: Regulatory Mechanisms and Clinical Significance

Aldosterone-producing adrenocortical adenoma (APA) is responsible for the majority of cases clinically diagnosed as primary aldosteronism. Aldosterone synthase (CYP11B2) is one of the enzymes that play essential roles in aldosterone synthesis and is involved in the pathogenesis of APA. Recent studies have demonstrated that various factors and regulators influence the expression and function of CYP11B2 in APA. In particular, somatic mutations, such as gain-of-function and loss-of-function mutations, have been identified in several genes, each of which encodes a pivotal protein that affects the calcium signaling pathway, the expression of CYP11B2, and aldosterone production. The gain-of-function mutations were reported in KCNJ5 that encodes G-protein activated inward rectifier K⁺ channel 4 (Kir3.4) and in CACNA1D, encoding calcium channel, voltage-dependent, L type, alpha subunit Cav1.3. The loss-of-function mutations were found in ATP1A1 that encodes Na⁺/K⁺ ATPase α subunit and in ATP2B3, encoding Ca²⁺ ATPase. Furthermore, the aberrant expression of gonadotropin-releasing hormone receptor is associated with the overexpression of CYP11B2 and overproduction of aldosterone in APA with activating mutations in CTNNB1 encoding β-catenin. On the other hand, CYP11B2 also catalyzes the conversion of cortisol to 18-hydroxycortisol and subsequently converts 18-hydroxycortisol to 18-oxocortisol. The recent studies have identified 18-oxocortisol as an important and distinct biomarker to diagnose primary aldosteronism. In this review, we summarize the recent findings on CYP11B2 and discuss the molecular pathogenesis of APA and the clinical significance of CYP11B2.

Histopathological Classification of Cross-Sectional Image-Negative Hyperaldosteronism

Context

Approximately half of patients with primary aldosteronism (PA) have clinically evident disease according to clinical (hypertension) and/or laboratory (aldosterone and renin levels) findings but do not have nodules detectable in routine cross-sectional imaging. However, the detailed histopathologic, steroidogenic, and pathobiological features of cross-sectional image-negative PA are controversial.

Objective

To examine histopathology, steroidogenic enzyme expression, and aldosterone-driver gene somatic mutation status in cross-sectional image-negative hyperaldosteronism.

Methods

Twenty-five cross-sectional image-negative cases were retrospectively reviewed. In situ adrenal aldosterone production capacity was determined using immunohistochemistry (IHC) of steroidogenic enzymes. Aldosterone-driver gene somatic mutation status (ATP1A1, ATP2B3, CACNA1D, and KCNJ5) was determined in the CYP11B2 immunopositive areas [n = 35; micronodule, n = 32; zona glomerulosa (ZG), n = 3] using next-generation sequencing after macrodissection.

Results

Cases were classified as multiple adrenocortical micronodules (MN; n = 13) or diffuse hyperplasia (DH) of ZG (n = 12) based upon histopathological evaluation and CYP11B2 IHC. Aldosterone-driver gene somatic mutations were detected in 21 of 26 (81%) of CYP11B2-positive cortical micronodules in MN; 17 (65%) mutations were in CACNA1D, 2 (8%) in KCNJ5, and 1 each (4% each) in ATP1A1 and ATP2B. One of 6 (17%) of nodules in DH harbored somatic aldosterone-driver gene mutations (CACNA1D); however, no mutations were detected in CYP11B2-positive nonnodular DH areas.

Conclusion

Morphologic evaluation and CYP11B2 IHC enabled the classification of cross-sectional image-negative hyperaldosteronism into MN and DH. Somatic mutations driving aldosterone overproduction are common in micronodules of MN, suggesting a histological entity possibly related to aldosterone-producing cell cluster development.

Characteristics of Japanese aldosterone-producing adenomas with KCNJ5 mutations

Somatic mutations in KCNJ5 gene have been identified in patients with adrenal aldosterone-producing adenomas (APAs). We previously reported that Japanese patients with APAs had distinct characteristics from patients in Western countries; i.e. they had a high frequency of KCNJ5 mutations and exhibited a frequent association with cortisol co-secretion. Therefore, APAs among Japanese patients may have different features from those in Western countries. We added recent cases, examined 47 cases (43% male) of APAs, including clinicopathological features, KCNJ5 mutations, and the mRNA levels of several steroidogenic enzymes, and compared the results obtained to those reported in other countries. While the prevalence of KCNJ5 mutations is approximately 40% in Western countries, 37 APA cases (78.7%) showed mutations: 26 with p.G151R and 11 with p.L168R. Although a significant gender difference has been reported in the frequency of KCNJ5 mutations in Europe, we did not find any gender difference. However, the phenotypes of Japanese patients with mutations were similar to those of patients in Western countries; patients were younger and had higher plasma aldosterone levels, lower potassium levels, and higher diastolic blood pressure. Reflecting these phenotypes, APAs with mutations had higher CYP11B2 mRNA levels. However, in contrast to APAs in Western countries, Japanese APAs with mutations showed lower CYP11B1, CYP17A1, and CYP11A1 mRNA levels. These findings demonstrated that Japanese APA patients may have distinct features including a higher prevalence of KCNJ5 mutations, no gender difference in the frequency of these mutations, and characteristics similar to the zona glomerulosa.

Clock genes and salt-sensitive hypertension: a new type of aldosterone-synthesizing enzyme controlled by the circadian clock and angiotensin II

With the current societal norm of shiftwork and long working hours, maintaining a stable daily life is becoming very difficult. An irregular lifestyle disrupts circadian rhythms, resulting in the malfunction of body physiology and ultimately leading to lifestyle-related diseases, including hypertension. By analyzing completely arrhythmic Cry1/Cry2 double-knockout (Cry-null) mice, we found salt-sensitive hypertension accompanied by hyperaldosteronism. On the basis of a DNA microarray analysis of the adrenal gland and subsequent biochemical analyses, we discovered that Hsd3b6/HSD3B1, a subtype of 3β-HSD, is markedly overexpressed in aldosterone-producing cells in the Cry-null adrenal cortex. In addition, we found that Hsd3b6/HSD3B1, which converts pregnenolone to progesterone, is a clock-controlled gene and might also be a key enzyme for the regulation of aldosterone biosynthesis, in addition to the previously established CYP11B2, which synthesizes aldosterone from deoxycorticosterone. Importantly, angiotensin II induces HSD3B1 via the transcription factor NGFIB in human adrenocortical H295R cells, similarly to CYP11B2. As HSD3B1 levels are abnormally high in the adrenal aldosterone-producing cells of idiopathic hyperaldosteronism (IHA), the temporal component of this system in the pathophysiology of IHA is a promising area for future research.

Immunohistochemistry of the adrenal in primary aldosteronism

PURPOSE OF REVIEW

Primary aldosteronism is a major cause of hypertension; aldosterone-producing adenomas (APA) cause about half of primary aldosteronism; idiopathic hyperplasia of adrenal glomerulosa cells are responsible for the rest. A surprising variety of mutations have recently been identified in ion channels and pumps in a significant number of APA. The present review addresses histological and molecular aspects of APA and the surrounding adrenal.

RECENT FINDINGS

Specific antibodies against the CYP11B2 and CYP11B1 enzymes, the last enzyme in aldosterone and cortisol synthesis, respectively, allow for the first time study of the steroidogenic capabilities of cells within the APA and adjacent adrenal. Cells expressing CYP11B2 may be scattered and/or in clusters throughout the normal adrenal zona glomerulosa. APA differ widely in the number of cells expressing CYP11B2; some did not express it at all, but were surrounded by cells, some in clusters or micronodules, that expressed CYP11B2. Some APAs also comprised cells expressing both CYP11B1 and CYP17A1. In some samples, analysis of the tissue adjacent to APA detected ion channel and pump mutations heretofore associated only with APA.

SUMMARY

APAs have a complex structure and expression of steroidogenic enzymes.

Expression of steroidogenic enzymes and their transcription factors in cortisol-producing adrenocortical adenomas: immunohistochemical analysis and quantitative real-time polymerase chain reaction studies

Adrenal Cushing syndrome (CS) is caused by the overproduction of cortisol in adrenocortical tumors including adrenal cortisol-producing adenoma (CPA). In CS, steroidogenic enzymes such as 17α-hydroxylase/17, 20-lase (CYP17A1), 3β-hydroxysteroid dehydrogenase (HSD3B), and 11β-hydroxylase (CYP11B1) are abundantly expressed in tumor cells. In addition, several transcriptional factors have been reported to play pivotal roles in the regulation of these enzymes in CPA, but their correlations with those enzymes above have still remained largely unknown. Therefore, in this study, we examined the status of steroidogenic enzymes and their transcriptional factors in 78 and 15 CPA cases by using immunohistochemistry and quantitative real-time polymerase chain reaction (qPCR), respectively. Immunoreactivity of HSD3B2, CYP11B1, CYP17A1, steroidogenic factor-1 (SF1[NR5A1]), GATA6, and nerve growth factor induced-B (NGFIB[NR4A1]) was detected in tumor cells. Results of qPCR analysis revealed that expression of HSD3B2 mRNA was significantly higher than that of HSD3B1, and CYP11B1 mRNA was significantly higher than CYP11B2. In addition, the expression of CYP11B1 mRNA was positively correlated with those of NR5A1, GATA6, and NR4A1. These results all indicated that HSD3B2 but not HSD3B1 was mainly involved in cortisol overproduction in CPA. In addition, NR5A1, GATA6, and NR4A1 were all considered to play important roles in cortisol overproduction through regulating CYP11B1 gene transcription.

Estimation of the Mechanism of Adrenal Action of Endocrine-Disrupting Compounds Using a Computational Model of Adrenal Steroidogenesis in NCI-H295R Cells

Adrenal toxicity is one of the major concerns in drug development. To quantitatively understand the effect of endocrine-active compounds on adrenal steroidogenesis and to assess the human adrenal toxicity of novel pharmaceutical drugs, we developed a mathematical model of steroidogenesis in human adrenocortical carcinoma NCI-H295R cells. The model includes cellular proliferation, intracellular cholesterol translocation, diffusional transport of steroids, and metabolic pathways of adrenal steroidogenesis, which serially involve steroidogenic proteins and enzymes such as StAR, CYP11A1, CYP17A1, HSD3B2, CYP21A2, CYP11B1, CYP11B2, HSD17B3, and CYP19A1. It was reconstructed in an experimental dynamics of cholesterol and 14 steroids from an in vitro steroidogenesis assay using NCI-H295R cells. Results of dynamic sensitivity analysis suggested that HSD3B2 plays the most important role in the metabolic balance of adrenal steroidogenesis. Based on differential metabolic profiling of 12 steroid hormones and 11 adrenal toxic compounds, we could estimate which steroidogenic enzymes were affected in this mathematical model. In terms of adrenal steroidogenic inhibitors, the predicted action sites were approximately matched to reported target enzymes. Thus, our computer-aided system based on systems biological approach may be useful to understand the mechanism of action of endocrine-active compounds and to assess the human adrenal toxicity of novel pharmaceutical drugs.

Intratumoral heterogeneity of steroidogenesis in aldosterone-producing adenoma revealed by intensive double- and triple-immunostaining for CYP11B2/B1 and CYP17

INTRODUCTION

Cytochrome P450 11B2 (CYP11B2) plays a pivotal role in aldosterone synthesis, while cytochrome P450 11B1 (CYP11B1) and cytochrome P450 17A1 (CYP17) are involved in cortisol synthesis in normal human adrenal glands. However, their detailed distribution in aldosterone-producing adenoma (APA) remains incompletely settled.

MATERIALS AND METHODS

We examined the status of CYP11B1/CYP11B2 and CYP11B2/CYP17A1 expressions in 27 APA (double staining) cases and 21 APA (triple staining) cases by using immunofluorescence staining and semi-quantitative evaluation.

RESULTS

Tumor cells co-expressing CYP11B1/B2 (hybrid cell type A), CYP11B2/17 (hybrid cell type B), CYP11B1/17 (hybrid cell type C), and CYP11B1/B2/17 (triple-positive cell) were identified. The area and cell number of these cells were relatively small, but the size of individual hybrid cells were different between three hybrid cell types (A/B/C) and triple-positive cells.

CONCLUSION

The presence of hybrid cells indicated the marked intratumoral heterogeneity of steroidogenesis in APAs, particularly in those producing glucocorticoids and mineralocorticoids.

Steroid Hormone Production in Patients with Aldosterone Producing Adenomas

Primary aldosteronism encompasses 2 major underlying causes: (1) aldosterone producing adenoma and (2) bilateral adrenal hyperplasia. In addition to the aldosterone excess, increased production of other compounds of the steroidogenic pathways may be involved. Until recently, most studies examined the production of steroids other than aldosterone in tumor tissue, urine, or peripheral plasma samples, but several new studies have also addressed steroid levels in adrenal venous blood samples using liquid chromatography tandem mass spectrometry. Plasma and tissue levels of several precursors of aldosterone with mineralocorticoid activity are higher in patients with aldosterone producing adenomas than in those with bilateral hyperplasia. These include corticosterone, deoxycorticosterone, and their 18-hydroxylated metabolites. Similarly, urinary, peripheral, and adrenal venous concentrations of the hybrid steroids 18-oxocortisol and 18-hydroxycortisol are higher in patients with aldosterone producing adenomas than in bilateral hyperplasia. Differences in the pathophysiology and in clinical and biochemical phenotypes caused by aldosterone producing adenomas and bilateral adrenal hyperplasia may be related to the differential expression of steroidogenic enzymes, and associated to specific underlying somatic mutations. Correct appreciation of differences in steroid profiling between aldosterone producing adenomas and bilateral adrenal hyperplasia may not only contribute to a better understanding of the pathogenesis of primary aldosteronism but may also be helpful for future subtyping of primary aldosteronism.

Aldosterone biosynthesis in the human adrenal cortex and associated disorders

Aldosterone is one of the mineralocorticoids synthesized and secreted by the adrenal glands, and it plays pivotal roles in regulating extracellular fluid volume and blood pressure. Autonomous excessive aldosterone secretion resulting from adrenocortical diseases is known as primary aldosteronism, and it constitutes one of the most frequent causes of secondary hypertension. Therefore, it is important to understand the molecular mechanisms of aldosterone synthesis in both normal and pathological adrenal tissues. Various factors have been suggested to be involved in regulation of aldosterone biosynthesis, and several adrenocortical cell lines have been developed for use as in vitro models of adrenal aldosterone-producing cells, for analysis of the underlying molecular mechanisms. In this review, we summarize the available reports on the regulation of aldosterone biosynthesis in the normal adrenal cortex, in associated disorders, and in in vitro models.

Pre-B Lymphocyte Protein 3 (VPREB3) Expression in the Adrenal Cortex: Precedent for non-Immunological Roles in Normal and Neoplastic Human Tissues

The pre-B lymphocyte protein 3 (VPREB3) is expressed during B cell differentiation and in subsets of mature B lymphocytes and is mainly found in bone marrow and lymphoid tissue germinative centers. So far, its function in B cells remains to be clarified. The messenger RNA (mRNA) of VPREB3 was previously detected in aldosterone-producing adenomas (APA); however, further information about this protein in human adrenocortical cells and tissues is currently unavailable. Therefore, in the present study, we, for the first time, investigate the protein expression of VPREB3 in human adrenocortical tissues. In addition, we approach the previously suggested similarities in expression patterns of aldosterone-producing cells and Purkinje neurons. Immunohistochemical analysis of VPREB3 was performed in 13 nonpathological adrenals (NA), 6 adrenal glands with idiopathic hyperaldosteronism (IHA), 18 APA, 5 cortisol-producing adenomas (CPA), and 5 nonpathological human cerebellum specimens. The mRNA levels of VPREB3, steroidogenic enzymes, and other aldosterone biosynthesis markers were detected in 53 APA samples using real-time RT-PCR (qPCR) and compared to the clinical data of APA patients. In our results, the VPREB3 protein was diffusely detected in APA, partially or weakly detected in CPA, and immunolocalized in the zona glomerulosa of NA and IHA, as well as in the cytoplasm of cerebellar Purkinje cells. In APA, VPREB3 mRNA levels were significantly correlated to plasma aldosterone (P = 0.026; R = 0.30), KCNJ5 mutations (P = 0.0061; mutated 34:19 wild type), CYP11B2 (P < 0.0001; R = 0.65), Purkinje cell protein 4 (PCP4; P < 0.0001; R = 0.53), and voltage-dependent calcium channels CaV1.3 (P = 0.023; R = 0.31) and CaV3.2 (P = 0.0019; R = 0.42). Based on our data, we hypothesize a possible role for VPREB3 in aldosterone biosynthesis, and present ideas for future functional studies.

Molecular and Cellular Mechanisms of Aldosterone Producing Adenoma Development

Primary aldosteronism (PA) is the most common form of secondary hypertension with an estimated prevalence of ~10% in referred patients. PA occurs as a result of a dysregulation of the normal mechanisms controlling adrenal aldosterone production. It is characterized by hypertension with low plasma renin and elevated aldosterone and often associated with hypokalemia. The two major causes of PA are unilateral aldosterone producing adenoma (APA) and bilateral adrenal hyperplasia, accounting together for ~95% of cases. In addition to the well-characterized effect of excess mineralocorticoids on blood pressure, high levels of aldosterone also have cardiovascular, renal, and metabolic consequences. Hence, long-term consequences of PA include increased risk of coronary artery disease, myocardial infarction, heart failure, and atrial fibrillation. Despite recent progress in the management of patients with PA, critical issues related to diagnosis, subtype differentiation, and treatment of non-surgically correctable forms still persist. A better understanding of the pathogenic mechanisms of the disease should lead to the identification of more reliable diagnostic and prognostic biomarkers for a more sensitive and specific screening and new therapeutic options. In this review, we will summarize our current knowledge on the molecular and cellular mechanisms of APA development. On one hand, we will discuss how various animal models have improved our understanding of the pathophysiology of excess aldosterone production. On the other hand, we will summarize the major advances made during the last few years in the genetics of APA due to transcriptomic studies and whole exome sequencing. The identification of recurrent and somatic mutations in genes coding for ion channels (KCNJ5 and CACNA1D) and ATPases (ATP1A1 and ATP2B3) allowed highlighting the central role of calcium signaling in autonomous aldosterone production by the adrenal.