The mammalian target of rapamycin (mTOR) inhibitor everolimus has been shown to display antiproliferative effects on a wide spectrum of tumors. In vitro studies demonstrated that everolimus inhibited pituitary neuroendocrine tumor (PitNET) cell growth in a subset of patients. Sensitivity to everolimus is reduced by an escape mechanism that increases AKT phosphorylation (p-AKT), leading to pro-survival pathway activation. Dopamine receptor type 2 (DRD2) mediates a reduction of p-AKT in a subgroup of non-functioning PitNETs (NF-PitNETs) and in prolactin-secreting tumor cells (MMQ cells) through a beta-arrestin 2-dependent mechanism. The aim of this study was to investigate the efficacy of everolimus combined with DRD2 agonist cabergoline in reducing NF-PitNET primary cells and MMQ cell proliferation and to evaluate AKT phosphorylation and a possible role of beta-arrestin 2. We found that 9 out of 14 NF-PitNETs were resistant to everolimus, but the combined treatment with cabergoline inhibited cell proliferation in 7 out of 9 tumors (-31.4 +/- 9.9%, p < 0.001 vs. basal) and reduced cyclin D3 expression. In the everolimus-unresponsive NF-PitNET group, everolimus determined a significant increase of p-AKT/total-AKT ratio (2.1-fold, p < 0.01, vs. basal) that was reverted by cabergoline cotreatment. To investigate the molecular mechanism involved, we used MMQ cells as a model of everolimus escape mechanism. Indeed everolimus did not affect MMQ cell proliferation and increased the p-AKT/total-AKT ratio (+1.53 +/- 0.24-fold, p < 0.001 vs. basal), whereas cabergoline significantly reduced cell proliferation (-22.8 +/- 6.8%, p < 0.001 vs. basal) and p-AKT. The combined treatment of everolimus and cabergoline induced a reduction of both cell proliferation (-34.8 +/- 18%, p < 0.001 vs. basal and p < 0.05 vs. cabergoline alone) and p-AKT/total-AKT ratio (-34.5 +/- 14%, p < 0.001 vs. basal and p < 0.05 vs. cabergoline alone). To test beta-arrestin 2 involvement, silencing experiments were performed in MMQ cells. Our data showed that the lack of beta-arrestin 2 prevented the everolimus and cabergoline cotreatment inhibitory effects on both p-AKT and cell proliferation. In conclusion, this study revealed that cabergoline might overcome the everolimus escape mechanism in NF-PitNETs and tumoral lactotrophs by inhibiting upstream AKT activation. The co-administration of cabergoline might improve mTOR inhibitor antitumoral activity, paving the way for a potential combined therapy in beta-arrestin 2-expressing NF-PitNETs or other PitNETs resistant to conventional treatments.

DRD2 Agonist Cabergoline Abolished the Escape Mechanism Induced by mTOR Inhibitor Everolimus in Tumoral Pituitary Cells / F. Mangili, E. Esposito, D. Treppiedi, R. Catalano, G. Marra, G. Di Muro, A.M. Barbieri, M. Locatelli, A.G. Lania, A. Mangone, A. Spada, M. Arosio, E. Peverelli, G. Mantovani. - In: FRONTIERS IN ENDOCRINOLOGY. - ISSN 1664-2392. - 13:3(2022), pp. 867822.1-867822.10. [10.3389/fendo.2022.867822]

DRD2 Agonist Cabergoline Abolished the Escape Mechanism Induced by mTOR Inhibitor Everolimus in Tumoral Pituitary Cells

F. Mangili
Primo
;
E. Esposito
Secondo
;
D. Treppiedi;R. Catalano;G. Marra;G. Di Muro;A.M. Barbieri;M. Locatelli;A.G. Lania;A. Mangone;A. Spada;M. Arosio;E. Peverelli
Penultimo
;
G. Mantovani
Ultimo
2022

Abstract

The mammalian target of rapamycin (mTOR) inhibitor everolimus has been shown to display antiproliferative effects on a wide spectrum of tumors. In vitro studies demonstrated that everolimus inhibited pituitary neuroendocrine tumor (PitNET) cell growth in a subset of patients. Sensitivity to everolimus is reduced by an escape mechanism that increases AKT phosphorylation (p-AKT), leading to pro-survival pathway activation. Dopamine receptor type 2 (DRD2) mediates a reduction of p-AKT in a subgroup of non-functioning PitNETs (NF-PitNETs) and in prolactin-secreting tumor cells (MMQ cells) through a beta-arrestin 2-dependent mechanism. The aim of this study was to investigate the efficacy of everolimus combined with DRD2 agonist cabergoline in reducing NF-PitNET primary cells and MMQ cell proliferation and to evaluate AKT phosphorylation and a possible role of beta-arrestin 2. We found that 9 out of 14 NF-PitNETs were resistant to everolimus, but the combined treatment with cabergoline inhibited cell proliferation in 7 out of 9 tumors (-31.4 +/- 9.9%, p < 0.001 vs. basal) and reduced cyclin D3 expression. In the everolimus-unresponsive NF-PitNET group, everolimus determined a significant increase of p-AKT/total-AKT ratio (2.1-fold, p < 0.01, vs. basal) that was reverted by cabergoline cotreatment. To investigate the molecular mechanism involved, we used MMQ cells as a model of everolimus escape mechanism. Indeed everolimus did not affect MMQ cell proliferation and increased the p-AKT/total-AKT ratio (+1.53 +/- 0.24-fold, p < 0.001 vs. basal), whereas cabergoline significantly reduced cell proliferation (-22.8 +/- 6.8%, p < 0.001 vs. basal) and p-AKT. The combined treatment of everolimus and cabergoline induced a reduction of both cell proliferation (-34.8 +/- 18%, p < 0.001 vs. basal and p < 0.05 vs. cabergoline alone) and p-AKT/total-AKT ratio (-34.5 +/- 14%, p < 0.001 vs. basal and p < 0.05 vs. cabergoline alone). To test beta-arrestin 2 involvement, silencing experiments were performed in MMQ cells. Our data showed that the lack of beta-arrestin 2 prevented the everolimus and cabergoline cotreatment inhibitory effects on both p-AKT and cell proliferation. In conclusion, this study revealed that cabergoline might overcome the everolimus escape mechanism in NF-PitNETs and tumoral lactotrophs by inhibiting upstream AKT activation. The co-administration of cabergoline might improve mTOR inhibitor antitumoral activity, paving the way for a potential combined therapy in beta-arrestin 2-expressing NF-PitNETs or other PitNETs resistant to conventional treatments.
AKT phosphorylation; cabergoline; dopamine receptor type 2; everolimus; mTOR inhibitors; pituitary neuroendocrine tumors
Settore MED/13 - Endocrinologia
PRIN201719EPEVE_01 - IN Search of early clinical and molecular Predictors of diagnosis and treatment response In patients with Rare Endocrine disorders: retrospective analysis on large healthcare database network and translational cohort studies (the INSPIRE project) - PEVERELLI, ERIKA MARIA - PRIN2017 - PRIN bando 2017 - 2019
FON_NAZ22GMANT_01 - Cytoskeleton actin-binding proteins as determinants and new biomarkers of pituitary tumor invasiveness and drug response (5° anno) - MANTOVANI, GIOVANNA - FON_NAZ - Bandi Altre Fondazioni - 2022
3-giu-2022
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/948252
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