Steroid contents and cortical steroidogenic enzymes in non-hyperfunctioning adrenal adenoma

Indications for laparoscopic adrenalectomy for non-functional adrenal tumor with hypertension: Usefulness of adrenocortical scintigraphy

AIM

Laparoscopic adrenalectomy is currently indicated for biochemically and clinically functional adrenal tumors and potentially malignant tumors of the adrenal glands. Non-functional adenomas greater than 5 cm in diameter of the adrenal gland are generally considered to represent potentially malignant tumors. The present study shows indications of laparoscopic adrenalectomy for non-functional adrenal tumors with hypertension in a retrospective fashion.

METHODS

Between 1994 and 2004, 110 laparoscopic adrenalectomies were performed at Tokushima University Hospital. All 110 patients underwent detailed endocrinological examination before surgery. Medical and operative records of these 110 patients (57 men, 53 women), including operative parameters, histopathological findings and pre- and postoperative hypertension, were reviewed. Forty-five patients underwent laparoscopic adrenalectomy for non-functional adrenal tumors, and [(131)I]6beta-iodomethyl-19-norcholest-5(10)-en-3beta-ol (NP-59) scintigraphy was performed for patients with preoperative hypertension.

RESULTS

Mean patient age was 55.0 years (range, 22-77 years). Mean maximum tumor diameter was 42 mm (range, 20-105 mm). All adrenal tumors were removed successfully by laparoscopic surgery. Hypertension was postoperatively improved in seven of the 11 patients with preoperative hypertension, without subclinical Cushing syndrome. Importantly, all patients who improved hypertension after adrenalectomy displayed strong accumulation in adrenal tumors with visualization of the contralateral gland on NP-59 scintigraphy. Conversely, blood pressure did not improve in four patients for whom scintigraphy yielded negative results.

CONCLUSIONS

The indication of laparoscopic adrenalectomy for non-functional adrenal tumors is generally considered for lesions more than 5 cm diameter. However, the present study suggests that laparoscopic surgery should be considered even in patients with tumors less than 5 cm in diameter, if both hypertension and accumulation in tumors on NP-59 scintigraphy are present.

Regulation of differential COUP-TF-coregulator interactions in adrenal cortical steroidogenesis

Hyperfunctioning adrenocortical adenomas produce excessive amounts of various corticosteroids due to dysregulated expression of steroidogenic enzymes. Since no genetic mutations in steroidogenic enzyme genes have been identified as yet, the dysregulated expression at the transcription level may be crucial. Chicken ovalbumin upstream promoter-transcription factors (COUP-TFs) and steroidogenic factor-1 (SF-1) play key roles in the transcriptional regulation of steroidogenic P450 genes. Transfection studies showed that SF-1 activated and COUP-TFs repressed the transcription of bovine CYP17 gene promoter from the CRS2 element in a mutually exclusive manner in Y-1 cells. The results indicate that COUP-TFs negatively regulate the transcriptional activity of SF-1, a steroidogenic cell-specific activator of various steroidogenic P450 genes. Expression of both COUP-TFI and COUP-TFII was significantly decreased in the cortisol-producing adenomas, in which CYP17 was drastically overexpressed, indicating that decreased expression of COUP-TFs play a key role in overexpression of CYP17 in this type of tumors. We then screened for COUP-TFI-interacting proteins from a cortisol-producing adenoma cDNA library using a yeast two-hybrid system and identified a novel RING finger-containing protein which can function as a coregulator for COUP-TFI. Notably, COUP-TFI activated rather than repressed several target genes including the human CYP11B2 gene promoter, the results of which were opposite to those of the CYP17 promoter. The bifunctional activities of COUP-TFI may be derived from the promoter context and our newly identified COUP-TFI coregulator.

Expression profiles of COUP-TF, DAX-1, and SF-1 in the human adrenal gland and adrenocortical tumors: possible implications in steroidogenesis

Chicken ovalbumin upstream promoter-transcription factor (COUP-TF), DAX-1, and steroidogenic factor-1 (SF-1) are orphan members of the nuclear hormone receptor superfamily. COUP-TF and DAX-1 have been shown to negatively regulate the transcriptional activity of SF-1, a steroidogenic cell-specific activator of various steroidogenic cytochrome P450 genes. We therefore examined the expression levels and immunolocalization of COUP-TF, DAX-1, and SF-1 in human adrenal gland (NL) and adrenocortical adenomas, and compared the results with CYP17 expression levels and its enzyme activities to study their potential correlation with adrenocortical steroidogenesis. In NL (n = 10), expressions of COUP-TF, DAX-1, and SF-1 were detected in the nuclei of adrenocortical cells, but not in the medulla. In cortisol-producing adenomas causing Cushing syndrome (CS, n = 20), CYP17 expression was upregulated (298 +/- 2% vs NL 98 +/- 4%), whereas expression levels of both COUP-TFs (COUP-TFI, 52 +/- 5% vs NL 98 +/- 4%; COUP-TFII, 18 +/- 4% vs NL 98 +/- 4%) and DAX-1 (42 +/- 4% vs NL 100 +/- 4%) were reduced. In deoxycorticosterone-producing adenomas (DOC, n = 2), on the other hand, CYP17 expression was extremely reduced (8 and 12% vs NL 98 +/- 4%), whereas DAX-1 expression increased markedly (350 and 360% vs NL 100 +/- 4%). Expression levels of SF-1 did not differ between NL (100 +/- 8%) and CS (106 +/- 10%), but its expression appeared to be decreased in DOC (25 and 20%). These results showed CYP17 expression to be upregulated and downregulated in CS and DOC, respectively, in a manner reciprocal to that of its repressors, COUP-TF and/or DAX-1. In summary, the results indicate that co-localization of COUP-TF, DAX-1, and SF-1 in NL was lost in adrenocortical tumors and that these orphan receptors play an important role in the regulation of steroidogenesis in human adrenals.

Differential expression of an orphan receptor COUP-TFI and corepressors in adrenal tumors

Recently, it has been shown that CYP17 gene transcription is activated by SF-1 (Steroidogenic Factor-1) binding to a cyclic AMP-responsive sequence within the promoter region of the gene, whereas it is inhibited by COUP-TF (Chicken Ovalbumin Upstream Promoter-Transcription Factor) binding to the sequence. We have shown that transcriptional repression by COUP-TFI is mediated by corepressors, N-CoR (nuclear receptor corepressor) and SMRT (silencing mediator for retinoid and thyroid hormone-receptor). Therefore, we compared the expression of COUP-TFI, N-CoR and SMRT in non-hyperfunctioning adrenocortical adenomas and normal adrenal glands. We found significantly higher expression of COUP-TFI mRNA in non-hyperfunctioning adenomas (n=5, 227+/-18%) than in normal adrenals (n=5, 96+/-4%). Interestingly, the pattern of N-CoR and SMRT expression was different compared with COUP-TFI expression. These data suggest that COUP-TFI, N-CoR, and SMRT may play a differential role in steroid biosynthesis of non-hyperfunctioning adenomas.

Gene expression of angiotensin II receptor in blood cells of Cushing's syndrome

The relation between serum cortisol, plasma renin activity, angiotensin II (Ang II), or aldosterone levels and peripheral blood cell (mononuclear leukocytes and platelets) angiotensin II type 1A (AT1A) and 1B (AT1B) receptor mRNA levels was examined in both patients with Cushing's syndrome (seven patients with Cushing's syndrome due to unilateral adrenal cortical adenoma) and control subjects (seven normotensive patients with renal cell carcinoma). Blood was collected from each participant for estimation of plasma renin activity and plasma angiotensin II, aldosterone, and cortisol concentrations and for isolation of mononuclear leukocytes and platelets, which were then used to measure AT1A and AT1B receptor mRNA levels before and after adrenalectomy with the use of reverse transcription-polymerase chain reaction. In patients with Cushing's syndrome, both mononuclear leukocyte and platelet AT1A mRNA levels, which were elevated, were reduced after removal of the adrenal tumors, whereas AT1B receptor mRNA levels of both types of blood cells did not significantly change after adrenalectomy. In contrast, in control subjects, both AT1A and AT1B receptor mRNA levels did not significantly change after unilateral adrenalectomy and nephrectomy. In the adrenal tumors of patients with Cushing's syndrome, gene expression of AT1A receptor was decreased compared with that from adrenals of control subjects. AT1A receptors of the platelets were shown to be upregulated in a manner similar to those of mononuclear leukocytes in patients with Cushing's syndrome. These results suggest that cortisol excess is an important factor upregulating AT1A receptor mRNA levels in human blood cells.