RNA Sequencing Provides Novel Insights into the Transcriptome of Aldosterone Producing Adenomas

Aldosterone producing adenomas (APAs) occur in the adrenal glands of around 30% of patients with primary aldosteronism, the most common form of secondary hypertension. Somatic mutations in KCNJ5, ATP1A1, ATP2B3, CACNA1D and CTNNB1 have been described in ~60% of these tumours. We subjected 15 aldosterone producing adenomas (13 with known mutations and two without) to RNA Sequencing and Whole Genome Sequencing (n = 2). All known mutations were detected in the RNA-Seq reads, and mutations in ATP2B3 (G123R) and CACNA1D (S410L) were discovered in the tumours without known mutations. Adenomas with CTNNB1 mutations showed a large number of differentially expressed genes (1360 compared to 106 and 75 for KCNJ5 and ATP1A1/ATP2B3 respectively) and clustered together in a hierarchical clustering analysis. RT-PCR in an extended cohort of 49 APAs confirmed higher expression of AFF3 and ISM1 in APAs with CTNNB1 mutations. Investigation of the expression of genes involved in proliferation and apoptosis revealed subtle differences between tumours with and without CTNNB1 mutations. Together our results consolidate the notion that CTNNB1 mutations characterize a distinct subgroup of APAs.