Recent evidence suggests that insulin is mitogenic on the adrenal cortex and stimulates adrenocortical tumor formation. We, investigated whether hyperinsulinemia is present in 13 patients with incidentally detected adrenal tumors. Patients with adrenal incidentalomas were obese (mean BMI 29.7 +/- 1.2 kg/m2, normal < 25; % body fat 35 +/- 1.5%, normal < 30%) with increased abdominal fat deposition (waist to hip ratio 0.92 +/- 0.02, normal < 0.85). All 13 patients were insulin resistant. Five had NIDDM, of the remaining patients 5 had fasting insulin concentrations above 15 microE/ml, and all 8 patients had elevated insulin concentrations after 75 g of glucose orally. To further investigate the potential role of insulin we examined its effects on the NCI-h295 cell line. Insulin (1-100 micrograms/ml) stimulated cell proliferation in a time and dose-dependent matter without affecting cortisol synthesis. At this concentrations insulin was equally potent to IGF I (10-80 ng/ml) or IGF II (10-100 ng/ml). We conclude that the majority of patients with adrenal incidentalomas are insulin-resistant/hyperinsulinemic. Insulin stimulates adrenal cancer cell lines in vitro. We propose that adrenal incidentalomas are a newly recognized manifestation of the metabolic syndrome comparable to insulin-mediated stimulation of the ovary in the polycystic ovary syndrome.
Objective: Adrenocortical carcinoma (ACC) is a rare neoplasm with poor prognosis. Discerning ACCs from benign adenomas histologically may be dif®cult if invasion into surrounding tissues or metastases are missing. Design: In order to establish molecular markers for malignancy, we analyzed seven normal adrenals, three massive macronodular ACTH-independent adrenocortical hyperplasias (MMAHs), 30 adrenocortical adenomas (ACAs) and ten ACCs. Methods: All tissues were studied for the presence of alterations in the p53 tumor suppressor gene using the PAb 1801 antibody, which detects mutant p53 protein and the pYNZ22 microsatellite marker to show loss of heterozygosity (LOH) at 17p, for expression of the proliferation-associated antigen Ki67 using the MIB1 antibody, for the rate of apoptotic tumor cells with the TdT-mediated dUTP biotin nick end labeling (TUNEL) method, and for LOH of 11q13 (menin gene locus) with the D11S956 microsatellite marker. Results: 0/3 MMAH, 1/28 ACA and 3/10 ACC revealed immunopositive staining for p53. LOH for pYNZ22 was observed in 1/3 MMAH, 1/23 informative ACA and 6/6 informative ACC. The rate of apoptotic cells was signi®cantly higher in ACC P , 0X0001 by ANOVA) than in ACA but there was some overlap between groups. The Ki67 index (% immunopositive cells) was 1X9^1X30% (mean^S.D.) in normal adrenals, 3X47^1X37% in MMAH, and 2X11^1X01% in ACA. ACC had the highest Ki67 index of 11X94^7X58% distinguishing all ACC from the ACA and MMAH studied with a cut-off level of 5%. LOH for 11q13 was detected in 2/3 MMAH, 5/26 ACA and 6/8 ACC. Conclusions: We conclude that a Ki67 index above 5% is a sensitive and speci®c indicator of ACC and may be useful in the differentiation of adenomas from carcinomas.
The mechanism(s) of tumorigenesis for the majority of adrenocortical neoplasms remain unknown. G-Protein-coupled receptors were recently proposed as candidate protooncogenes. That activating mutations of this class of receptors might be important for tumor induction or progression of endocrine neoplasms was strengthened by the recent identification of such mutations in hyperfunctioning thyroid adenomas. To examine whether the ACTH receptor (ACTH-R) gene could be an oncogene in human adrenocortical tumors, we amplified by the polymerase chain reaction and directly sequenced the entire exon of the ACTH-R gene in 25 adrenocortical tumors (17 adenomas and 8 carcinomas) and 2 adrenocortical cancer cell lines. We found no missense point mutations or even silent polymorphisms in any of the tumors and cell lines studied. We conclude that activating mutations of the ACTH-R gene do not represent a frequent mechanism of human adrenocortical tumorigenesis.
Chronic endogenous estrogen deficiency does not have major effects on the development of cardiac hypertrophy, dysfunction and dilation post-MI.
The adrenostatic compound aminoglutethimide (AG), a potent inhibitor of the P450 side chain cleavage enzyme, is used in the treatment of ACTH-dependent or adrenal Cushing's syndrome. Recently, AG has been shown to inhibit ACTH receptor (ACTH-R) mRNA expression in ovine adrenocortical cells in a time-dependent fashion. To investigate whether ACTH-R down-regulation will also be induced in tumor cells, we studied the effect of AG on ACTH-R expression in the human NCI-h295 adrenocortical carcinoma cell line, which expresses functional ACTH receptors and produces steroids of the glucocorticoid, mineralocorticoid and androgen pathway. The cells were incubated in triplicate with increasing doses of AG (3, 30, 300 µM) which suppressed steroid secretion dosedependently. After 48 h, cells were harvested, and total RNA was extracted, electrophoresed, blotted and hybridized with a human ACTH-R cDNA probe. In parallel experiments, after preincubation with AG the cells were stimulated with ACTH (10 nM) for 10 min and the intracellular cAMP accumulation was determined by RIA. AG significantly suppressed the baseline ACTH-R mRNA expression in a dose-dependent fashion (300 µM AG, 5 1%; 30 µM AG, 64 1%; 3 µM AG, 108 19% compared with control cells, 100 11%). The reduced ACTH-R mRNA expression was paralleled by low ACTH-induced cAMP accumulation indicating reduced expression of the ACTH-R protein. The adrenostatic compound metyrapone, an inhibitor of 11 -hydroxylase activity, also suppressed ACTH-R mRNA expression in a similar fashion. Stimulation of the protein kinase A pathway by simultaneous incubation of ACTH (10 nM) or forskolin (10 µM) together with AG was not able to overcome the steroid biosynthesis blockade, but reversed the inhibitory effects of AG on the ACTH-R mRNA expression. Also, cortisol (12 µM) reversed the AGinduced ACTH-R mRNA expression. We conclude that AG induces profound ACTH-R down-regulation in the NCI-h295 cell line either by affecting the gene expression or by decreasing transcript accumulation via an effect on RNA stability. This novel action of AG can be reversed by stimulation of the cAMP pathway and of the glucocorticoid-mediated signal transduction cascade. As the down-regulation occurs in vitro at concentrations which are reached during treatment with AG in humans it may contribute to its therapeutic activity in adrenal disease.
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