DNA Demethylation of CYP11B1 Plays a Critical Role in the Cortisol Excess in Adrenal Cushing’s Syndrome

Presentation Number: MON 391
Date of Presentation: April 3rd, 2017

Mitsuhiro Kometani*1, Takashi Yoneda2, Masashi Demura1, Shigehiro Karashima1 and Yoshiyu Takeda2
1Kanazawa University, Kanazawa, Japan, 2Kanazawa University, Ishikawa, Japan

Abstract

Background: DNA methylation is a fundamental epigenetic mechanism that regulates gene expression and is often associated with the development of endocrine and metabolic diseases.

Objective: To examine whether the expression of CYP11B1, which catalyzes the final step of cortisol biosynthesis, is regulated through DNA methylation in adrenal Cushing’s syndrome, and to investigate a possible relationship between DNA methylation and somatic mutations found in adrenal Cushing’s syndrome.

Methods: We first examined the effect of DNA methylation on activity of the CYP11B1 promoter and CYP11B1 mRNA expression using human adrenocortical carcinoma H295R cells. We next performed methylation analysis of the CYP11B1 promoter in adrenal Cushing’s syndrome patients.

Results: DNA methylation reduced the CYP11B1 promoter activity in the reporter assay, and the treatment of H295R cells with demethylating agents upregulated CYP11B1 expression. Methylation status of the CYP11B1 promoter was significantly lower in adrenal Cushing’s syndrome adenomas than in adjacent adrenal glands and white blood cells. In adrenal Cushing’s syndrome adenomas with somatic mutations in either the PRKACA or GNAS gene, the CYP11B1 promoter was significantly hypomethylated.

Conclusion: These data suggest that DNA demethylation at the promoter region of the CYP11B1 gene plays an important role in CYP11B1 expression in adrenal Cushing’s adenomas. Furthermore, somatic mutations associated with adrenal Cushing’s syndrome adenomas result in activation of the cAMP/protein kinase A signaling pathway and reduce DNA methylation at the CYP11B1 promoter.

 

Nothing to Disclose: MK, TY, MD, SK, YT