Genetic and epigenetic analyses of aldosterone-producing adenoma with hypercortisolemia

DNA methylation is associated with excess cortisol and aldosterone. The DNA encoding aldosterone synthase (CYP11B2) and 11β-hydroxylase (CYP11B1), which catalyzes the final step of cortisol biosynthesis, is less methylated in aldosterone-producing adenomas (APA) and cortisol-producing adenomas (CPA), respectively. Several studies have reported specific gene mutations in APA and CPA, and some APAs also cause hypercortisolemia. The aim of this study was to clarify the molecular mechanisms of cortisol co-production in APA using genetic and epigenetic analyses. We evaluated 16 patients with APA between 2011 and 2018 at Kanazawa University Hospital (Ishikawa, Japan). The diagnostic criteria for hypercortisolemia were based on the guideline from the Endocrine Society. Gene mutation and DNA methylation analyses of the CYP11B2 and CYP11B1 promoters in APA were performed. Of the 16 patients with APA, six also had hypercortisolemia. In the genetic analysis, all six APAs with hypercortisolemia as well as eight of the 10 APAs without hypercortisolemia had a KCNJ5 mutation. In the epigenetic analyses, the methylation status of the CYP11B2 promoter was similar in the APAs with and without hypercortisolemia. However, in the APAs with hypercortisolemia, the CYP11B1 promoter was significantly less methylated, especially at two CpG sites near the Ad1/cAMP response element binding site within the CYP11B1 promoter. In conclusion, the genetic analysis revealed no association between hypercortisolemia and the evaluated gene mutations. However, the epigenetic analysis suggested that DNA methylation of the CYP11B1 promoter plays a role in concurrent hypercortisolemia and APA.