Different immunohistochemical patterns of TGF-beta1 expression in benign and malignant adrenocortical tumours

DACH1, a zona glomerulosa selective gene in the human adrenal, activates transforming growth factor-β signaling and suppresses aldosterone secretion

Common somatic mutations in CACNAID and ATP1A1 may define a subgroup of smaller, zona glomerulosa (ZG)-like aldosterone-producing adenomas. We have therefore sought signature ZG genes, which may provide insight into the frequency and pathogenesis of ZG-like aldosterone-producing adenomas. Twenty-one pairs of zona fasciculata and ZG and 14 paired aldosterone-producing adenomas from 14 patients with Conn's syndrome and 7 patients with pheochromocytoma were assayed by the Affymetrix Human Genome U133 Plus 2.0 Array. Validation by quantitative real-time polymerase chain reaction was performed on genes >10-fold upregulated in ZG (compared with zona fasciculata) and >10-fold upregulated in aldosterone-producing adenomas (compared with ZG). DACH1, a gene associated with tumor progression, was further analyzed. The role of DACH1 on steroidogenesis, transforming growth factor-β, and Wnt signaling activity was assessed in the human adrenocortical cell line, H295R. Immunohistochemistry confirmed selective expression of DACH1 in human ZG. Silencing of DACH1 in H295R cells increased CYP11B2 mRNA levels and aldosterone production, whereas overexpression of DACH1 decreased aldosterone production. Overexpression of DACH1 in H295R cells activated the transforming growth factor-β and canonical Wnt signaling pathways but inhibited the noncanonical Wnt signaling pathway. Stimulation of primary human adrenal cells with angiotensin II decreased DACH1 mRNA expression. Interestingly, there was little overlap between our top ZG genes and those in rodent ZG. In conclusion, (1) the transcriptome profile of human ZG differs from rodent ZG, (2) DACH1 inhibits aldosterone secretion in human adrenals, and (3) transforming growth factor-β signaling pathway is activated in DACH1 overexpressed cells and may mediate inhibition of aldosterone secretion in human adrenals.

The role of transforming growth factor β1 in the regulation of blood pressure

Although human association studies suggest a link between polymorphisms in the gene encoding transforming growth factor (TGF) β1 and differing blood pressure levels, a causative mechanism for this correlation remains elusive. Recently we have generated a series of mice with graded expression of TGFβ1, ranging from approximately 10% to 300% compared to normal. We have found that blood pressure and plasma volume are negatively regulated by TGFβ1. Of note, the 10% hypomorph exhibits primary aldosteronism and markedly impaired urinary excretion of water and electrolytes. We here review previous literature highlighting the importance of TGFβ signaling as a natriuretic system, which we postulate is a causative mechanism explaining how polymorphisms in TGFβ1 could influence blood pressure levels.

Autocrine/paracrine regulatory mechanisms in adrenocortical neoplasms responsible for primary adrenal hypercorticism

A wide variety of autocrine/paracrine bioactive signals are able to modulate corticosteroid secretion in the human adrenal gland. These regulatory factors, released in the vicinity of adrenocortical cells by diverse cell types comprising chromaffin cells, nerve terminals, cells of the immune system, endothelial cells, and adipocytes, include neuropeptides, biogenic amines, and cytokines. A growing body of evidence now suggests that paracrine mechanisms may also play an important role in the physiopathology of adrenocortical hyperplasias and tumors responsible for primary adrenal steroid excess. These intra-adrenal regulatory systems, although globally involving the same actors as those observed in the normal gland, display alterations at different levels, which reinforce the capacity of paracrine factors to stimulate the activity of adrenocortical cells. The main modifications in the adrenal local control systems reported by now include hyperplasia of cells producing the paracrine factors and abnormal expression of the latter and their receptors. Because steroid-secreting adrenal neoplasms are independent of the classical endocrine regulatory factors angiotensin II and ACTH, which are respectively suppressed by hyperaldosteronism and hypercortisolism, these lesions have long been considered as autonomous tissues. However, the presence of stimulatory substances within the neoplastic tissues suggests that steroid hypersecretion is driven by autocrine/paracrine loops that should be regarded as promising targets for pharmacological treatments of primary adrenal disorders. This new potential therapeutic approach may constitute an alternative to surgical removal of the lesions that is classically recommended in order to cure steroid excess.

Tumores adrenocorticais na criança: da abordagem clínica à avaliação molecular

Tumores do córtex adrenal (TCA) são mais frequentes em crianças, mas podem ocorrer em qualquer faixa etária. São classificados como funcionantes, não funcionantes (predominam no adulto), e mistos. O diagnóstico é baseado na avaliação clínica, hormonal e exames de imagem. Em crianças, o método de escolha para diferenciar entre benigno ou maligno é a classificação baseada no estadiamento do tumor. Alguns marcadores moleculares merecem destaque: além de mutações inativadoras no gene supressor tumoral TP53, há evidências de envolvimento do IGF2 em 90% de TAC malignos, e mutações no éxon 3 do gene CTNNB1 foram encontradas em 6% dos TAC pediátricos. Além disso, microRNAs podem atuar como reguladores negativos da expressão gênica e participar da tumorigênese adrenocortical. Métodos para análise da expressão gênica permitem identificar TCA com prognóstico bom ou ruim, e espera-se que esses estudos possam facilitar o desenvolvimento de drogas para tratar pacientes de acordo com as vias de sinalização específicas que estiverem alteradas.

Discerning malignancy in resected adrenocotical tumors

BACKGROUND

The number of adrenocortical tumors discovered incidentally has recently increased owing to the advent of imaging techniques. The most important diagnostic point in evaluation of resected specimens of these tumors is to discern malignancy to determine postoperative management of the patients.

OBJECTIVE/METHODS

To determine what the effective methods of discerning malignancy in resected specimens of adrenocortical tumors are at this juncture. To provide relevant and practical information pertinent to those involved in the management of patients with adrenocortical tumors.

CONCLUSION

Careful macroscopic evaluation, including the selection of the specimens submitted and application of the criteria of Weiss for histological diagnosis, is still considered the 'gold standard' for diagnosis of adrenocortical carcinoma. However, it is important to recognize its limitations in the diagnosis of adrenocortical oncocytoma and pediatric adrenocortical tumors. The auxiliary methods that may be of clinical relevance at this juncture include the analysis of the Ki67/MIB-1 labeling index and IGF-II expression in the tumors.