Identification of gene expression profiles associated with cortisol secretion in adrenocortical adenomas

The cortisol secretion of adrenocortical adenomas can be either subtle or overt. The mechanisms leading to the autonomous hypersecretion of cortisol are unknown.

The objective of the study was to identify the gene expression profile associated with the autonomous and excessive cortisol secretion of adrenocortical adenomas.

The transcriptome of 22 unilateral adrenocortical adenomas (5 nonsecreting, 6 subclinical cortisol producing, 11 cortisol producing) was studied and correlated with cortisol secretion. Phosphodiesterase 8B (PDE8B) expression was measured by Western blot.

Unsupervised clustering identified 2 groups of adenomas with a difference in secretion level (P = .008). Cluster 1 included only cortisol-producing adenomas (8 of 11), whereas cluster 2 was an admixture of the nonsecreting, the subclinical cortisol-secreting, and 3 of the 11 cortisol-secreting adenomas (Fisher exact, P = .002). This cluster was driven by genes related to cortisol secretion and to extracellular matrix. More than 3000 genes correlated with cortisol secretion. Among the positively correlated were the steroidogenic enzymes, genes involved in cholesterol metabolism, and glutathione S-transferases. Among the negatively correlated genes were genes related to transcripts translation and the transcription factor GATA-6. The PDE8B, which inactivates the protein kinase A pathway, unexpectedly showed the strongest positive correlation with cortisol secretion, confirmed by Western blot. The protein kinase A-activity to cAMP ratio was increased in adenomas with high PDE8B levels, suggesting counterregulation to limit downstream activation of the pathway.

The transcriptome of adrenocortical adenomas reveals a major association with cortisol secretion and identifies specific groups of genes implicated in steroid secretion, suggesting that cAMP signaling alterations might be frequent in cortisol-secreting adenomas.