Identification of Adrenocorticotropin Receptor Messenger Ribonucleic Acid in the Human Pituitary and Its Loss of Expression in Pituitary Adenomas

• Published in: The journal of clinical endocrinology and metabolism 2003-12, Vol.88 (12), p.6080-6087
• Main Authors: Morris, Damian G., Kola, Blerina, Borboli, Ninetta, Kaltsas, Gregory A., Gueorguiev, Maria, McNicol, Anne Marie, Ferrier, Roderick, Jones, T. Hugh, Baldeweg, Stephanie, Powell, Michael, Czirják, Sándor, Hanzély, Zoltán, Johansson, Jan-Ove, Korbonits, Márta, Grossman, Ashley B.
• Format: Article
• Language: English
• Subjects: Adenoma; Adenoma - metabolism; Adolescent; Adrenal cortex; Adrenocorticotropic hormone; Adrenocorticotropic Hormone - blood; Adult; Aged; Biological and medical sciences; Child; Disease resistance; DNA sequencing; DNA, Complementary - genetics; Endocrinopathies; Feedback; Female; Follicle-stimulating hormone; G protein-coupled receptors; Gene expression; Growth hormones; Humans; Hybridization; Hypothalamus. Hypophysis. Epiphysis (diseases); Immunohistochemistry; In Situ Hybridization; Male; Medical sciences; Melanocortin; Middle Aged; mRNA; Non tumoral diseases. Target tissue resistance. Benign neoplasms; Pit1 protein; Pituitary; Pituitary (anterior); Pituitary Gland - metabolism; Pituitary Neoplasms - metabolism; Polymerase Chain Reaction; Pro-Opiomelanocortin - genetics; Pro-Opiomelanocortin - metabolism; Prolactin; Receptors, Corticotropin - genetics; Receptors, Corticotropin - metabolism; RNA, Messenger - metabolism; Tissue Distribution; Tumors
• ISSN: 0021-972X; 1945-7197
• DOI: 10.1210/jc.2002-022048

The ACTH receptor (ACTH-R) is the second member of the melanocortin (MC-2) receptor family that includes five seven-transmembrane G protein-coupled receptors and has been shown to be predominantly expressed in the adrenal cortex. It has been postulated that ACTH may regulate its own secretion through ultra-short-loop feedback within the pituitary. ACTH-secreting adenomas are characterized by resistance to glucocorticoid feedback, and they may have dysregulated ACTH feedback. We therefore investigated the ACTH-R in normal and adenomatous human pituitary tissue. We report here the identification of ACTH-R mRNA in the human pituitary gland, which was confirmed by direct sequencing. We studied the expression of the ACTH-R in 23 normal pituitary specimens and 53 pituitary adenomas (22 ACTH-secreting, nine GH-secreting, eight prolactin-secreting, one TSH-secreting, one FSH-secreting, 10 nonfunctioning, and two silent corticotroph adenomas), using the sensitive technique of real-time quantitative PCR. Contamination of ACTH-secreting adenomas and nonfunctioning pituitary adenomas with nonadenomatous tissue was excluded by lack of Pit-1 expression. ACTH-R mRNA was detected in all normal pituitary specimens, and in situ hybridization colocalized expression to ACTH staining cells only. However, ACTH-R mRNA levels were undetectable in 16 of 22 ACTH-secreting tumors and in both silent corticotroph tumors. Diagnostic preoperative plasma ACTH levels were significantly lower in the ACTH-R positive ACTH-secreting tumors, compared with those who were ACTH-R negative (P = 0.0006). Direct sequencing of the coding region of the ACTH-R in cDNA from three ACTH-secreting tumors positively expressing the receptor showed no mutations, as did sequencing of genomic DNA in three receptor negative ACTH-secreting tumors and the two silent corticotrophs. These results provide further evidence compatible with an ACTH feedback loop in the pituitary and suggest that loss of expression of the ACTH-R in corticotroph adenomas of patients with Cushing’s disease may play a role in the resistance to feedback of the pituitary-adrenal axis seen in these patients.