OP.3A.02] RETINOIC ACID RECEPTOR SIGNALING CONTRIBUTES TO ADRENAL CORTEX MORPHOLOGY AND FUNCTIONAL ZONATION

Abstract

Objective: Recurrent somatic mutations in KCNJ5, CACNA1D, ATP1A1 and ATP2B3 have been identified in aldosterone producing adenoma (APA). Although the role of these mutations in regulating aldosterone biosynthesis has been clearly established, the mechanisms involved in proliferation and APA formation still remains to be elucidated. The aim of our study was to identify pathways involved in adrenal cortex nodulation and APA formation. Design and method: We have analyzed transcriptome data generated from 123 APA and 11 control adrenals and correlated gene expression to the genetic, morphological and functional characteristics of the tumors. To evaluate the role of retinoic acid receptor RAR in the development of APA, we have investigated the consequences of modulation of RAR signaling in cell lines derived from human adrenal cortex and in rarα-/- mice. Results: We have identified RAR signaling as a central molecular network involved in APA formation independently of the mutation status Treatment of H295R cells with all-trans retinoic acid and 9-cis retinoic acid reduced cell viability in a time- and dose-dependent manner. This effect was due to decreased cell proliferation and increased cell apoptosis. In contrast to the effects observed in vitro, 9-cis retinoic acid did not modify tumor progression in a mouse xenograft model. RARα invalidation by shRNA transduction in H295R cells did not affect their proliferative properties, but induced a major change in cellular phenotype with cells forming spheroid structures. Investigation of the adrenal phenotype of rarα-/- mice demonstrated that in young (12 weeks) and old (52 weeks) rarα-/- mice the characteristic cellular arrangement of the adrenal cortex was replaced by an enlarged zona glomerulosa and a disorganized zona fasciculata, this effect being more pronounced in old mice. RARα invalidation resulted in a significant decrease of CYP11B2 expression and/or aldosterone production, both in cell and mice models. Conclusions: Our results suggest that RAR signaling contributes to normal adrenal morphology and functional zonation and that its disruption could contribute to abnormal cell proliferation in the adrenal cortex, creating a propitious environment for the emergence of specific driver mutations in APA.