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.
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