1. Glucocorticoid Receptor Antagonism Upregulates Somatostatin Receptor Subtype 2 Expression in ACTH-Producing Neuroendocrine Tumors: New Insight Based on the Selective Glucocorticoid Receptor Modulator Relacorilant.
- Author
-
Pivonello R, Munster PN, Terzolo M, Ferrigno R, Simeoli C, Puglisi S, Bali U, and Moraitis AG
- Subjects
- ACTH-Secreting Pituitary Adenoma diagnostic imaging, ACTH-Secreting Pituitary Adenoma metabolism, Adenoma diagnostic imaging, Adenoma metabolism, Adult, Aged, Animals, Bronchial Neoplasms diagnostic imaging, Bronchial Neoplasms metabolism, Cell Line, Tumor, Dexamethasone pharmacology, Down-Regulation, Female, Glucocorticoids pharmacology, Humans, In Vitro Techniques, Male, Mice, Middle Aged, Neuroendocrine Tumors diagnostic imaging, Neuroendocrine Tumors metabolism, Organometallic Compounds, Positron-Emission Tomography, Radiopharmaceuticals, Somatostatin analogs & derivatives, ACTH-Secreting Pituitary Adenoma drug therapy, Adenoma drug therapy, Adrenocorticotropic Hormone metabolism, Bronchial Neoplasms drug therapy, Isoquinolines pharmacology, Neuroendocrine Tumors drug therapy, Pyrazoles pharmacology, Pyridines pharmacology, Receptors, Glucocorticoid antagonists & inhibitors, Receptors, Somatostatin drug effects, Receptors, Somatostatin metabolism
- Abstract
Somatostatin exhibits an inhibitory effect on pituitary hormone secretion, including inhibition of growth hormone and adrenocorticotropic hormone (ACTH), and it can have antisecretory and antitumor effects on neuroendocrine tumors (NETs) that express somatostatin receptors. Although the precise mechanism remains unclear, the finding that glucocorticoids downregulate somatostatin receptor subtype 2 (SSTR2) expression has been used to explain the lack of efficacy of traditional SSTR2-targeting analogs in patients with ACTH-secreting NETs. Glucocorticoid receptor (GR) antagonism with mifepristone has been shown to reverse the glucocorticoid-induced downregulation of SSTR2; however, the effects of GR modulation on SSTR2 expression in ACTH-secreting NETs, particularly corticotroph pituitary tumors, are not well known. The current study presents new insight from in vitro data using the highly selective GR modulator relacorilant, showing that GR modulation can overcome dexamethasone-induced suppression of SSTR2 in the murine At-T20 cell line. Additional data presented from clinical case observations in patients with ACTH-secreting NETs suggest that upregulation of SSTR2 via GR modulation may re-sensitize tumors to endogenous somatostatin and/or somatostatin analogs. Clinical, laboratory, and imaging findings from 4 patients [2 ACTH-secreting bronchial tumors and 2 ACTH-secreting pituitary tumors (Cushing disease)] who were treated with relacorilant as part of two clinical studies (NCT02804750 and NCT02762981) are described. In the patients with ectopic ACTH secretion, SSTR2-based imaging (Octreoscan and
68 Ga-DOTATATE positron emission tomography) performed before and after treatment with relacorilant showed increased radiotracer uptake by the tumor following treatment with relacorilant without change in tumor size at computed tomography. In the patients with Cushing disease who received relacorilant prior to scheduled pituitary surgery, magnetic resonance imaging after a 3-month course of relacorilant showed a reduction in tumor size. Based on these findings, we propose that GR modulation in patients with ACTH-secreting NETs upregulates previously suppressed SSTR2s, resulting in tumor-specific antisecretory and anti-proliferative effects. The effect of relacorilant on pituitary corticotroph tumors is being investigated in an ongoing phase 3 study (NCT03697109; EudraCT 2018-003096-35)., Competing Interests: RP: Consultant: Ferring, Ipsen, Novartis, Pfizer, ViroPharma-Shire; Speaker: Novartis, ViroPharma-Shire; Research support: Corcept Therapeutics, Novartis, ViroPharma-Shire; Grant support: IBSA, Novartis, Pfizer, ViroPharma-Shire. PM: Consultant: Atlas, Alessa, EpiAxis, Rascal and AstraZeneca. MT: Consultant: HRA Pharma; Research support: Corcept Therapeutics. CS: Consultant: Ipsen, ViroPharma-Shire. UB: Consultant: Corcept Therapeutics; Employee: Sygnature Discovery, Ltd. AM: Employee: Corcept Therapeutics. The authors declare that the studies received funding from Corcept Therapeutics (Menlo Park, CA, USA). The funder had a role in study design, data collection and analysis. MA was employed by the company Corcept Therapeutics and, as an author of the manuscript and employee of Corcept Therapeutics, had a role in the study design, the decision to publish, the interpretation of clinical data, the revision of the manuscript, and approval of the final manuscript to submit. UB was employed by the company Sygnature Discovery Ltd. and, as an author of the manuscript and employee of Sygnature Discovery Ltd., supported by the funder, had a role in the preclinical data analysis and interpretation, decision to publish, revision of the manuscript, and approval of the final manuscript to submit. Open Access publication fees were paid by Corcept Therapeutics., (Copyright © 2022 Pivonello, Munster, Terzolo, Ferrigno, Simeoli, Puglisi, Bali and Moraitis.)- Published
- 2022
- Full Text
- View/download PDF