PubMed Health⌕ Search

Biomedical subjects

Xavier Bertagna

Publications and source records attributed to Xavier Bertagna.

40 records · Page 3Linked to original sources
PubMed2002

Mutations of the PRKAR1A gene in Cushing's syndrome due to sporadic primary pigmented nodular adrenocortical disease.

Primary pigmented nodular adrenocortical disease (PPNAD) is a cause of ACTH-independent Cushing's syndrome. This condition can be difficult to diagnose because hypercortisolism may be periodic and adrenal imaging may not demonstrate an adrenal tumor. PPNAD can be part of the Carney complex (CNC), an autosomal dominant multiple neoplasia syndrome. Germline mutations of the regulatory subunit R1A of PKA (PRKAR1A) have been observed in about 45% of CNC kindreds. To improve our understanding of sporadic PPNAD and develop a potential diagnostic tool, we investigated the genetics of patients with sporadic and isolated PPNAD. Patients undergoing surgery for bilateral ACTH-independent Cushing's syndrome in whom pathological examination revealed PPNAD were subjected to endocrinological investigations and a systematic search for other manifestations of CNC. The PRKAR1A gene was sequenced using DNA from frozen adrenal tissues and leukocytes from three patients with sporadic isolated PPNAD and using leukocyte DNA from two additional patients. Different inactivating germline mutations of the PRKAR1A gene were found in the five patients. For three cases, study of the parents' DNA demonstrated a de novo mutation. One patient presented with an unusual 2.5-cm macronodule of the right adrenal mimicking an adrenal adenoma. A somatic 16-bp deletion of PRKAR1A gene was also found in this macronodule. Inactivating germline mutations of PRKAR1A are frequent in sporadic and isolated cases of PPNAD. The wild-type allele can be inactivated by somatic mutations, consistent with the hypothesis of the gene being a tumor suppressor gene. Thus, genetic analysis can be of help to the clinician in the diagnosis of this difficult form of adrenal Cushing's syndrome.

Adolescent↗
PubMed2002

Identification of genes associated with the corticotroph phenotype in bronchial carcinoid tumors.

The proopiomelanocortin (POMC) gene is occasionally expressed in nonpituitary tumors leading to Cushing's syndrome. Bronchial carcinoid tumors, one of the most frequent source for ectopic ACTH secretion, often display numerous features of the corticotroph phenotype. To identify new markers of corticotroph differentiation in these tumors, we compared the pattern of gene expression in ACTH-secreting (ACTH+) and nonsecreting (ACTH-) bronchial carcinoids by differential display/RT-PCR. Using groups of ACTH+ and ACTH- tumors, we initially selected approximately 300 differentially expressed genes. Fifteen were considered differentially expressed after further characterization by RT-PCR on a larger series of 8 ACTH+ and 12 ACTH- bronchial carcinoids; 11 were restricted to--or overexpressed in--ACTH+ and four in ACTH- tumors. In ACTH+, beside the expected POMC gene, we identified cFos, and KIAA1775, a large expressed sequence tag encoding a putative protocadherin-related protein. On the other hand, the tetraspanin TM4SF5 gene was specifically expressed in ACTH-. Dot blot analysis confirmed the specific expression of KIAA1775 in ACTH+ bronchial carcinoids. However, the expression of most of the differential genes, including KIAA1775, was detected by RT-PCR in pituitary or lung tumors, whether secreting ACTH or not, excepted for TM4SF5, which was only detected in some nonendocrine lung tumors. Our results show that corticotroph differentiation of bronchial carcinoid tumors is accompanied by induction and repression of specific genes. The nature of some of these genes, identified here, underlines the importance of cell-cell or cell-extracellular matrix interactions in the establishment of neoplastic corticotroph phenotype. These genes should help to better characterize ACTH+ bronchial carcinoids as well as other bronchial carcinoid subtypes.

Adrenocorticotropic Hormone↗
PubMed2002

The ectopic expression of the gastric inhibitory polypeptide receptor is frequent in adrenocorticotropin-independent bilateral macronodular adrenal hyperplasia, but rare in unilateral tumors.

Control of cortisol secretion by the abnormal expression of the gastric inhibitory polypeptide receptor (GIP-R) have been observed in some rare cases of ACTH-independent, food-dependent Cushing's syndrome (FD-ACS) due to adrenal adenoma (AA) or bilateral macronodular hyperplasia (AIMAH). This study was performed to determine the prevalence of GIP-R ectopic expression in ACS and its correlation with fasting cortisol levels. GIP-R expression was studied by RT-PCR in 30 unilateral adrenal tumors [16 AA and 14 adrenocortical cancer (AC)] and 8 AIMAH tissues. Fasting and postprandial cortisol levels were assayed, respectively, at 0800 and 1200 h in AA, AC, and AIMAH, and 1 h after a morning standard meal in 6 AIMAH patients. Similar expression of 2 GIP-R isoforms was observed in 1 of 16 AA, 0 of 14 AC, and 4 of 8 AIMAH as well as in the 4 insulinomas used as positive controls. In vitro study of the GIP-R-expressing AA showed stimulation of cortisol secretion and cAMP production by GIP. The fasting 0800-h plasma cortisol level was above 276 nmol/liter in all patients except 1 AA case and 1 AIMAH case, both of whom expressed GIP-R. In the 3 additional AIMAH cases that expressed the GIP-R, fasting plasma cortisol levels were above 276 nmol/liter. This study demonstrates that ectopic expression of GIP-R is rare in AA and is usually associated with the low fasting plasma cortisol levels that characterize FD-ACS. In contrast, GIP-R expression is frequent in AIMAH and might not always be associated with a low fasting plasma cortisol level. This suggests that maintenance of hypercortisolemia in GIP-R- expressing AIMAH does not always depend solely on GIP-R, and that simultaneous abnormal expression of other membrane receptors might be present. The expression of GIP-R could not be observed during malignant transformation of the adrenal cortex. This study highlighted the major role of cAMP alterations secondary to GIP-R ectopic expression in the pathophysiology of AIMAH and in some rare cases of well differentiated benign adrenocortical tumors.

Adenoma↗