Comprehensive re-sequencing of adrenal aldosterone producing lesions reveal three somatic mutations near the KCNJ5 potassium channel selectivity filter

Abstract

Background: Aldosterone producing lesions are a common cause of hypertension, but genetic alterations for tumorigenesis have been unclear. Recently, either of two recurrent somatic missense mutations (G151R or L168R) was found in the potassium channel KCNJ5 gene in aldosterone producing adenomas. These mutations alter the channel selectivity filter and result in Na(+) conductance and cell depolarization, stimulating aldosterone production and cell proliferation. Because a similar mutation occurs in a mendelian form of primary aldosteronism, these mutations appear to be sufficient for cell proliferation and aldosterone production. The prevalence and spectrum of KCNJ5 mutations in different entities of adrenocortical lesions remain to be defined.

Materials and methods: The coding region and flanking intronic segments of KCNJ5 were subjected to Sanger DNA sequencing in 351 aldosterone producing lesions, from patients with primary aldosteronism and 130 other adrenocortical lesions. The specimens had been collected from 10 different worldwide referral centers.

Results: G151R or L168R somatic mutations were identified in 47% of aldosterone producing adenomas, each with similar frequency. A previously unreported somatic mutation near the selectivity filter, E145Q, was observed twice. Somatic G151R or L168R mutations were also found in 40% of aldosterone producing adenomas associated with marked hyperplasia, but not in specimens with merely unilateral hyperplasia. Mutations were absent in 130 non-aldosterone secreting lesions. KCNJ5 mutations were overrepresented in aldosterone producing adenomas from female compared to male patients (63 vs. 24%). Males with KCNJ5 mutations were significantly younger than those without (45 vs. 54, respectively; p<0.005) and their APAs with KCNJ5 mutations were larger than those without (27.1 mm vs. 17.1 mm; p<0.005).

Discussion: Either of two somatic KCNJ5 mutations are highly prevalent and specific for aldosterone producing lesions. These findings provide new insight into the pathogenesis of primary aldosteronism.

Figure 1. Sanger traces from 4 tumor samples with somatic mutations G433C (pE145Q), G451A and G451C (pG151R) and T503G (pL168R) in KCNJ5.

Figure 2. Comparison of different KCNJ5 orthologs.

Complete conservation of substituted amino acid residues E145, G151 and L168 across multiple specimens, from Human to Tunicate.

Figure 3. Mutation spectrum and gender distribution.

L168R and G151R substitutions account for the waste majority of the mutations found in aldosterone producing lesions. KCNJ5 mutations are more frequent in lesions from female patients, indicating a distinct gender dimorphism.

Figure 4. Heterogeneous immunoreactivity of KCNJ5 independent of mutational status.

A) Intense KCNJ5 reactivity in a 4 mm macronodule expressing only WT KCNJ5. B) Moderate KCNJ5 reactivity in a 19 mm large adenoma expressing L168R KCNJ5.