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.
Pascual-Le Tallec
Laurent
L
Institut National de la Santé et de la Recherche Médicale Unité 567, Centre National de la Recherche Scientifique Unité Mixte de Recherche 8104, Department of Endocrinology, Université Paris 5, 24 rue du Faubourg Saint-Jacques, 75014 Paris, France.
Dulmet
Elisabeth
E
Bertagna
Xavier
X
de Keyzer
Yves
Y
D000324:Adrenocorticotropic Hormone / Q000378:metabolism*; D000328:Adult; D001984:Bronchial Neoplasms / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D002276:Carcinoid Tumor / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D018076:DNA, Complementary / Q000032:analysis; D005260:Female; D015870:Gene Expression; D006801:Humans; D008175:Lung Neoplasms / Q000737:chemistry / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D010911:Pituitary Neoplasms / Q000737:chemistry / Q000378:metabolism; D011333:Pro-Opiomelanocortin / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA
D018076:DNA, Complementary; D012333:RNA, Messenger; D011333:Pro-Opiomelanocortin; D000324:Adrenocorticotropic Hormone