Frequency and clinical correlates of somatic Ying Yang 1 mutations in sporadic insulinomas.

CONTEXT: Insulinomas represent pancreatic neuroendocrine neoplasms that cause severe morbidity attributed to their often pronounced endocrine activity. Apart from hereditary forms such as multiple endocrine neoplasia type 1 (MEN-1), genetic causes for sporadic insulinoma development had remained obscure until recently. Applying next-generation sequencing methods, disease-causing genetic alterations have been identified in various endocrine tumors. OBJECTIVE AND DESIGN: Paired tumor and blood DNA from eight patients with sporadic insulinomas (five females and two malignant tumors) were analyzed by whole-exome sequencing. After this initial analysis, Ying Yang 1 (YY1) mutation status was assessed in a larger cohort of 39 additional insulinomas (including eight malignant and one liver metastasis) from three German hospitals by targeted sequencing. The mutation status was correlated with various clinical parameters. RESULTS: A range of one to 12 somatic genetic variants were identified by exome sequencing. A recurrent somatic Thr372Arg YY1 point mutation was detected in two patients of the initial cohort and four patients of the second cohort (total, six of 47; 13%). The presence of the mutation was associated with a trend toward higher age (63.5 y; IQR, 48.0-74.0 vs 45.0 y; IQR, 33.0-63.0; P = .05), and all affected patients were females (six of six; P = .04). All other clinical parameters, including the presence of malignancy and metastatic spread, tumor localization, and hypoglycemic episodes were not different between YY1-mutated and nonmutated tumor carriers. CONCLUSIONS: The somatic Thr372Arg YY1 mutation is a relevant finding in female patients with sporadic insulinomas. The prevalence of this mutation in this Caucasian population is considerably lower compared to that of a recently described Asian cohort.

Constitutive activation of PKA catalytic subunit in adrenal Cushing's syndrome.

BACKGROUND: Corticotropin-independent Cushing's syndrome is caused by tumors or hyperplasia of the adrenal cortex. The molecular pathogenesis of cortisol-producing adrenal adenomas is not well understood. METHODS: We performed exome sequencing of tumor-tissue specimens from 10 patients with cortisol-producing adrenal adenomas and evaluated recurrent mutations in candidate genes in an additional 171 patients with adrenocortical tumors. We also performed genomewide copy-number analysis in 35 patients with cortisol-secreting bilateral adrenal hyperplasias. We studied the effects of these genetic defects both clinically and in vitro. RESULTS: Exome sequencing revealed somatic mutations in PRKACA, which encodes the catalytic subunit of cyclic AMP-dependent protein kinase (protein kinase A [PKA]), in 8 of 10 adenomas (c.617A→C in 7 and c.595_596insCAC in 1). Overall, PRKACA somatic mutations were identified in 22 of 59 unilateral adenomas (37%) from patients with overt Cushing's syndrome; these mutations were not detectable in 40 patients with subclinical hypercortisolism or in 82 patients with other adrenal tumors. Among 35 patients with cortisol-producing hyperplasias, 5 (including 2 first-degree relatives) carried a germline copy-number gain (duplication) of the genomic region on chromosome 19 that includes PRKACA. In vitro studies showed impaired inhibition of both PKA catalytic subunit mutants by the PKA regulatory subunit, whereas cells from patients with germline chromosomal gains showed increased protein levels of the PKA catalytic subunit; in both instances, basal PKA activity was increased. CONCLUSIONS: Genetic alterations of the catalytic subunit of PKA were found to be associated with human disease. Germline duplications of this gene resulted in bilateral adrenal hyperplasias, whereas somatic PRKACA mutations resulted in unilateral cortisol-producing adrenal adenomas. (Funded by the European Commission Seventh Framework Program and others.).