Detection of somatic beta-catenin mutations in primary pigmented nodular adrenocortical disease (PPNAD).
BACKGROUND
Primary pigmented nodular adrenocortical disease (PPNAD) leads to Cushing syndrome (CS) and is often associated with Carney complex (CNC). Genetic alterations of the type 1-alpha regulatory subunit of cAMP-dependent protein kinase A (PRKAR1A) and phosphodiesterase 11A4 (PDE11A) genes have been found in PPNAD. Recent studies have demonstrated that beta-catenin mutations are frequent in adrenocortical adenomas and carcinomas and that the Wnt-signalling pathway is involved in PPNAD tumorigenesis. We hypothesized that adrenocortical adenomas that form in the context of PPNAD may harbour beta-catenin mutations.


METHODS
We studied 18 patients with CS secondary to PPNAD who were screened for germline PRKAR1A and PDE11A mutations. Tumor DNA was extracted from pigmented adrenocortical adenoma and nodular adrenal hyperplasia. Mutation analysis of exons 3 and 5 of beta-catenin was performed using polymerase chain reaction and direct sequencing. Sections from formalin-fixed, paraffin-embedded tumour samples were studied by immunohistochemistry with an antibody against beta-catenin.


RESULTS
Nine patients were carrying germline PRKAR1A mutations and one patient had a PDE11A mutation. We found somatic beta-catenin mutations in 2 of 18 patients (11%). In both cases, the mutations occurred in relatively large adenomas that had formed in the background of PPNAD. Tumor DNA analysis revealed a heterozygous ACC-to-GCC missense mutation in codon 41 (T41A) and a TCT-to-CCT missense mutation in codon 45 (S45P) of exon 3 of the beta-catenin gene that was confirmed at the cDNA level. There were no alterations in the DNA of PPNAD-adjacent tissues and lymphocytes from the patients, indicating somatic events. Immunohistochemistry showed nuclear accumulation of beta-catenin in more than 90% of cells in adenomatous tissue whereas no nuclear immunoreactivity was detected in adjacent PPNAD nodular cells. Nuclear translocation of beta-catenin protein in the PPNAD adenoma suggests activation of the Wnt-beta-catenin pathway in PPNAD.


CONCLUSIONS
We report, for the first time, beta-catenin mutations in adenomas associated with PPNAD, further implicating Wnt-beta-catenin signalling in tumorigenesis linked to bilateral adrenal hyperplasias.
Tadjine
Mimi
M
Division of Endocrinology, Department of Medicine, Centre hospitalier de l'Université de Montréal (CHUM) Hôtel-Dieu, Montreal, QC, Canada.
Lampron
Antoine
A
Ouadi
Lydia
L
Horvath
Anelia
A
Stratakis
Constantine A
CA
Bourdeau
Isabelle
I
D015106:3',5'-Cyclic-GMP Phosphodiesterases; D000236:Adenoma / Q000150:complications / Q000235:genetics / Q000473:pathology; D000293:Adolescent; D000303:Adrenal Cortex Diseases / Q000150:complications / Q000235:genetics*; D000306:Adrenal Cortex Neoplasms / Q000150:complications / Q000235:genetics / Q000473:pathology; D000328:Adult; D002648:Child; D002675:Child, Preschool; D054756:Cyclic AMP-Dependent Protein Kinase RIalpha Subunit / Q000235:genetics; D004252:DNA Mutational Analysis; D005260:Female; D005820:Genetic Testing; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation; D010727:Phosphoric Diester Hydrolases / Q000235:genetics; D010859:Pigmentation Disorders / Q000150:complications / Q000235:genetics; D055815:Young Adult; D051176:beta Catenin / Q000235:genetics*
D054756:Cyclic AMP-Dependent Protein Kinase RIalpha Subunit; C517834:PRKAR1A protein, human; D051176:beta Catenin; D010727:Phosphoric Diester Hydrolases; D015106:3',5'-Cyclic-GMP Phosphodiesterases; C406737:PDE11A protein, human