The results of immunohistochemical study of antibodies to CYP11B2 in primary hyperaldosteronism

Abstract

Background: Aldosterone-producing adrenocortical adenoma (APA) is responsible for the majority of cases clinically diagnosed as primary aldosteronism. Aldosterone synthase (CYP11B2) is one of the enzymes that play essential roles in aldosterone synthesis and is involved in the pathogenesis of primary aldosteronism. Recent studies have demonstrated that various factors influence the expression and function of CYP11B2 in APA. In particular, somatic mutations, such as gain-of-function and loss-of-function mutations have been identified in several genes, each of which encodes a pivotal protein that affects the calcium signaling pathway, the expression of CYP11B2, and aldosterone production. On the other hand, CYP11B2 also catalyzes the conversion of cortisol to 18-hydroxycortisol and subsequently converts 18-hydroxycortisol to 18-oxocortisol. The article also discusses the clinical significance of 18-oxocortisol, an important biomarker for the diagnosis of primary aldosteronism. Somatic mutations in aldosterone-driver genes are strongly associated with CYP11B2 expression and have been only detected in the CYP11B2-positive tumor area, that indicating heterogeneous expression of CYP11B2 in tumor.Aim: to assess the functional heterogeneity of adrenal tumors in primary aldosteronismMaterials and methods: Retrospective evaluation adrenal tumors from patients with primary aldosteronism (n=20). According to CT unilateral macrohyperplasia was detected in 19 patients (95% of total), all of them were confirmed to have unilateral hyperproduction of aldosterone according to AVS. Selected tumors werestained with anty-CYP11B2 antibody. We evaluated the CYP11B2 expression in the adenoma and in the adjacent adrenal cortex.Results: Immunohistochemistry studies of the resected adrenals from 20 patients with PA operated due to unilateral production of aldosterone using CYP11B2 staining showed that 10 of those with an adenoma on CT scanning showed CYP11B2 staining in the adenoma. Furthermore, 5 cases of an unilateral adenoma, showed CYP11B2 staining in the adjacent adrenal cortex and an absence of staining for CYP11B2 in the adenoma. 5 cases showed CYP11B2 expression is heterogeneously immunolocalized throughout the tumor area.Conclusion: Thus, the functional heterogeneity of adrenal tumors in primary aldosteronism has been proven. It is necessary to compare the data of immunohistochemical studies on the expression of CYP11B2 with the indicators of the level of 18-hydroxycortisol, 18-oxocortisol.