Phosphodiesterase 11A (PDE11A) and genetic predisposition to adrenocortical tumors

Abstract

Purpose: We have reported previously nonsense inactivating mutations of the phosphodiesterase 11A (PDE11A) gene in patients with micronodular adrenocortical hyperplasia and Cushing syndrome. The aim of this study is to investigate the presence of somatic or germ-line PDE11A mutations in various types of adrenocortical tumors: ACTH-independent macronodular adrenocortical hyperplasia (AIMAH), adrenocortical adenoma (ACA), and adrenocortical cancer (ACC).

Experimental design: PDE11A was sequenced in 117 adrenocortical tumors and 192 controls subjects; immunohistochemistry for PDE11A and tumor cyclic AMP levels were studied in a subgroup of adrenocortical tumors.

Results: One PDE11A inactivating mutation (R307X) was found in one ACA, 22 germ-line missense variants (18.8%) were found in adrenocortical tumors, and only 11 missense variants (5.7%) were found in controls. By comparing the common mutations, a higher frequency of mutations in adrenocortical tumors than in age/sex-matched controls were observed [16% versus 10% in ACC, 19% versus 10% in ACA, and 24% versus 9% in AIMAH; odds ratio (OR), 3.53; P = 0.05]. Somatic DNA from adrenocortical tumors with missense variants showed a wild-type allelic loss. A significant difference between ACC and controls was observed for a polymorphism in exon 6 (E421E; OR, 2.1; P = 0.03) and three associated polymorphisms located in intron 10-exon 11-intron 11 (OR, 0.5; P = 0.01). In AIMAH/ACA, cyclic AMP levels were higher than in normal adrenals and decreased PDE11A immunostaining was present in adrenocortical tumors with PDE11A variants.

Conclusions: The present investigation of a large cohort of adrenocortical tumors suggests that PDE11A sequence defects predispose to a variety of lesions (beyond micronodular adrenocortical hyperplasia) and may contribute to the development of these tumors in the general population.

Figure 1. Localization of mutations and missense variants on the PDE11A gene

The PDE11A gene contains 23 exons; coding starts from exon 3 and ends with exon 23; exons 3 to 12 sequences code for the GAF a and GAF b domain (cGMP binding PDE) and exons 14 to 22 code for the catalytic domain. ▲, ACC; ■ ACA; ●, AIMAH; ○, controls.

Figure 2. Example of mutations in 2 ACC and 1 ACA

A and B, missense mutations in 2 ACC (R804H and A349) and 1 ACA (M878V) in leukocyte DNA (heterozygous state) and in the corresponding tumor (hemizygous state). In the tumor sample, the wild-type allele is lost and only the mutated allele is present. C, wild-type sequence.

Figure 3. Effect of PDE11A variants in cAMP levels

cAMP activity in adrenal tissue lysates of 6 AIMAH and 5 ACA wild-type for PDE11A (). cAMP activity in adrenal tissue lysates of 5 AIMAH and 5 ACA with PDE11A variants (R804H, H664G, A349T, D609N, and R867G and R307X, M878V, R804H, R867G, and T727C, respectively; ■). Tissue lysates from three normal adrenal glands were assayed separately for cAMP content (□). All experiments were repeated at least twice and each sample was run in duplicate.

Figure 4. PDE11A immunohistochemistry

Decreased PDE11A protein in two adrenocortical tumors with PDE11A missense substitutions: one ACC (A) and one ACA (C). PDE11A immunostaining in three wild-type adrenocortical tumors: one ACC (B), one ACA (D), and one AIMAH (F). Immunopositivity for PDE11A in Leydig cell from normal testis tissue was used as positive control (E). Magnification, ×400 (A and E), ×200 (B and F), and ×100 (C and D).