Microarray, qPCR, andKCNJ5Sequencing of Aldosterone-Producing Adenomas Reveal Differences in Genotype and Phenotype between Zona Glomerulosa- and Zona Fasciculata-Like Tumors

Abstract

Aldosterone-producing adenomas (APA) are heterogeneous. The recent finding of somatic KCNJ5 mutations suggests a genetic explanation. The objectives of this study were the following: 1) to compare transcriptional profiles in APA and adjacent adrenal gland (AAG); 2) to test whether gene expression profile clusters with different cell histology; and 3) to measure the frequency of KCNJ5 mutations and determine the genotype-phenotype relationship. The design of the study included laboratory analyses of 46 unselected APA. The patients in this study had primary hyperaldosteronism with unilateral APA. The objectives of this study were the following: 1) Illumina beadchip analysis of RNA from eight paired APA-AAG; 2) a blinded review of cell histology for 46 APA; 3) laser capture microdissection of zona glomerulosa (ZG) and zona fasciculata (ZF) cells; and 4) sequencing of KCNJ5 in 46 APA. The main outcome measures of this study were the following: 1) a difference in gene expression profile and a correlation with histological markers of ZF; 2) a frequency of KCNJ5 mutations and phenotypic comparisons of wild type with mutant APA. The results of the study were the following: 1) a cluster analysis of microarray data separated APA from AAG. APA at opposite ends of the APA cluster had an approximately 800-fold difference in CYP17A1 mRNA expression, whereas histology showed 0% ZF-like cells in one vs. 100% in the other. A heat map ranking APA by CYP17A1 expression correctly predicted several genes (e.g. KCNK1, SLC24A3) to be enriched in laser capture microdissection samples of ZG; 2) known or novel mutations of KCNJ5 were found in 20 of 46 consecutive APA [43% (95% confidence interval [CI] (29, 58)%)]. The APA with KCNJ5 gene mutations were larger compared with tumors harboring the wild type, 1.63 [95% CI (1.37, 1.88)] vs. 1.14 [0.97, 1.30] cm (P = 0.0013), had predominantly ZF-like cells, and their CYP17A1 (log(2)-fold change) was higher than in wild type: -0.96 [95% CI (-0.07, -1.85)] vs. -2.54 [-1.61, -3.46], (P = 0.017). KCNJ5 mutations are common in APA, particularly those arising from ZF. The long-recognized heterogeneity among APA may have a genetic basis.