title: Proopiomelanocortin, glucocorticoid, and CRH receptor expression in human ACTH-secreting pituitary adenomas.
abstract: ACTH-secreting pituitary tumors are by definition partially autonomous, i.e., secrete ACTH independent of physiological control. However, only few, small-sized studies on proopiomelanocortin (POMC) and its regulation by corticotropin-releasing hormone (CRH) or glucocorticoids are available. Objective of the present study was to report on constitutive and CRH- and dexamethasone-regulated POMC, CRH (CRH-R1), and glucocorticoid receptor (NR3C1) gene expression in a large series of human corticotrope adenomas. Fifty-three ACTH-secreting adenomas were incubated with 10 nM CRH or 10 nM dexamethasone for 24 h. POMC, CRH-R1, NR3C1, and its alpha and beta isoforms were quantified and medium ACTH measured. Constitutive POMC expression proved extremely variable, with macroadenomas exhibiting higher levels than microadenomas. POMC increased during CRH in most specimens; conversely, changes induced by dexamethasone were varied, ranging from decrease to paradoxical increase. No correlation between POMC and ACTH was detected in any experimental condition. CRH-R1 expression was not linked to the response to CRH while NR3C1 was expressed at greater levels in specimens who failed to inhibit during dexamethasone; glucocorticoid receptor α was the more abundant isoform and subject to down-regulation by dexamethasone. Our results demonstrate a considerable variability in POMC expression among tumors and no correlation between POMC and ACTH, suggesting that POMC peptide processing/transport plays a major role in modulating ACTH secretion. Further, CRH-R1 and NR3C1 expression were not linked to the expected ligand-induced outcome, indicating that receptor signaling rather than abundance determines corticotrope responses. Our findings pave the way to new avenues of research into Cushing's disease pathophysiology.
authors.affiliation: Neuroendocrinology Research Laboratory, Istituto Auxologico Italiano IRCCS, Cusano Milanino, Milan, Italy.
authors.forename: Maria Francesca
authors.initials: MF
authors.lastname: Cassarino
authors.affiliation: Neuroendocrinology Research Laboratory, Istituto Auxologico Italiano IRCCS, Cusano Milanino, Milan, Italy.
authors.forename: Antonella
authors.initials: A
authors.lastname: Sesta
authors.affiliation: Neuroendocrinology Research Laboratory, Istituto Auxologico Italiano IRCCS, Cusano Milanino, Milan, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Pagliardini
authors.affiliation: Department of Neurosurgery, Ospedale San Raffaele IRCCS, Milan, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Losa
authors.affiliation: Department of Neurosurgery, Istituto Clinico Humanitas, Rozzano, Milan, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Lasio
authors.affiliation: Neuroendocrinology Research Laboratory, Istituto Auxologico Italiano IRCCS, Cusano Milanino, Milan, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Cavagnini
authors.affiliation: Neuroendocrinology Research Laboratory, Istituto Auxologico Italiano IRCCS, Cusano Milanino, Milan, Italy. fpg@auxologico.it.|Department of Clinical Sciences and Community Health, University of Milan, Piazzale Brescia 20, 20149, Milan, Italy. fpg@auxologico.it.
authors.forename: Francesca
authors.initials: F
authors.lastname: Pecori Giraldi
mesh_terms: D049913:ACTH-Secreting Pituitary Adenoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D000236:Adenoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D003346:Corticotropin-Releasing Hormone / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology; D015536:Down-Regulation / Q000187:drug effects; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D005938:Glucocorticoids / Q000494:pharmacology; D006801:Humans; D008297:Male; D011333:Pro-Opiomelanocortin / Q000235:genetics / Q000378:metabolism*; D018019:Receptors, Corticotropin-Releasing Hormone / Q000235:genetics / Q000378:metabolism*; D011965:Receptors, Glucocorticoid / Q000235:genetics / Q000378:metabolism*; D000099052:CRF Receptor, Type 1
chemical_list: D005938:Glucocorticoids; D018019:Receptors, Corticotropin-Releasing Hormone; D011965:Receptors, Glucocorticoid; D000099052:CRF Receptor, Type 1; D011333:Pro-Opiomelanocortin; D003907:Dexamethasone; D003346:Corticotropin-Releasing Hormone
keywords: ACTH; CRH; Cushing’s disease; Dexamethasone; POMC