Antagonists of Growth Hormone-Releasing Hormone Inhibit the Growth of Pituitary Adenoma Cells by Hampering Oncogenic Pathways and Promoting Apoptotic Signaling

Abstract

Pituitary adenomas (PAs) are intracranial tumors, often associated with excessive hormonal secretion and severe comorbidities. Some patients are resistant to medical therapies; therefore, novel treatment options are needed. Antagonists of growth hormone-releasing hormone (GHRH) exert potent anticancer effects, and early GHRH antagonists were found to inhibit GHRH-induced secretion of pituitary GH in vitro and in vivo. However, the antitumor role of GHRH antagonists in PAs is largely unknown. Here, we show that the GHRH antagonists of MIAMI class, MIA-602 and MIA-690, inhibited cell viability and growth and promoted apoptosis in GH/prolactin-secreting GH3 PA cells transfected with human GHRH receptor (GH3-GHRHR), and in adrenocorticotropic hormone ACTH-secreting AtT20 PA cells. GHRH antagonists also reduced the expression of proteins involved in tumorigenesis and cancer progression, upregulated proapoptotic molecules, and lowered GHRH receptor levels. The combination of MIA-690 with temozolomide synergistically blunted the viability of GH3-GHRHR and AtT20 cells. Moreover, MIA-690 reduced both basal and GHRH-induced secretion of GH and intracellular cAMP levels. Finally, GHRH antagonists inhibited cell viability in human primary GH- and ACTH-PA cell cultures. Overall, our results suggest that GHRH antagonists, either alone or in combination with pharmacological treatments, may be considered for further development as therapy for PAs.

Antagonist of Growth Hormone-Releasing Hormone Potentiates the Antitumor Effect of Pemetrexed and Cisplatin in Pleural Mesothelioma

“…We have previously demonstrated the ability of MIA-602 and MIA-690 to inhibit in vitro PM cell proliferation and viability and cMyc expression [ 29 ], a result confirmed here in vivo, where mice treated with MIA-690, either alone or with cisplatin/pemetrexed, showed reduced cMyc expression in PM tumors. Accordingly, the anticancer effects of MIA-690 and the downregulation of cMyc were recently shown by our group in vitro, in pituitary adenoma cell lines [ 44 ], and in a collaborative study by Recinella et al in colorectal cancer in mice, where an increase in p53 protein levels and inhibtion of COX-2, iNOS, and NF-kB gene levels were also observed [ 23 ]. Accordingly, our present results show that MIA-690 potentiates the effect of cisplatin/pemetrexed in PM xenografts also on inhibition of NF-kB, assessed as phosphorylation of p65 subunit, and STAT3 phosphorylation.…”

“…Importantly, TP53, encoding p53, is the most commonly mutated gene in human cancers, and the deletion of Pten and TP53 in mouse mesothelium results in the development of non-epithelioid mesothelioma [ 43 ]. We have previously demonstrated that MIA-602 and MIA-690, in addition to displaying antitumor activities, increase the expression of p53 in human PM cell lines [ 29 ], as well as in GH/prolactin-secreting pituitary adenoma cell lines [ 44 ] and colorectal cancer cells [ 23 ]. Furthermore, earlier GHRH antagonists counteracted the mitogenic effects of GHRH in lung cancer cell lines by increasing p53 and inhibiting MAPK activation, as well as the expression of inflammatory iNOS, COX-2 and NF-kB [ 45 ].…”

“…The GHRH-R antagonist MIA-690 [PhAc-Ada 0 -Tyr 1 , D-Arg 2 , Cpa 6 , Ala 8 , Har 9 , Fpa 510 , His 11 , Orn 12 , Abu 15 , His 20 , Orn 21 , Nle 27 , D-Arg 28 , Har 29 ] hGH-RH(1-29)NH 2 was synthesized and purified in the laboratory of one of the authors (Andrew V. Schally) at the Veterans Affairs Medical Center, University of Miami, Miami, FL, USA, as described previously [ 29 , 44 ]. For in vitro experiments, MIA-690 was dissolved in 100% dimethyl sulfoxide (DMSO) (MilliporeSigma, Milan, Italy) and diluted with appropriate incubation medium.…”

“…Protein extraction and Western blot analysis were performed as described previously [ 29 , 44 ]. Proteins (30 μg) were separated by SDS-PAGE (10% for P-STAT3, P-NF-κB, p53, P-ERK1/2, and 12% for p21 and BAX), transferred to a nitrocellulose membrane; after blocking with 1% BSA in Tris-buffered saline with 0.1% Tween for 2 h at room temperature, membranes were incubated overnight at 4 °C with the specific antibody (dilution 1:1000 for P-STAT3, P-NF-κB, P-ERK1/2, BAX and 1:500 for p53 and p21).…”

Novel neoplasms associated with syndromic pediatric medulloblastoma: integrated pathway delineation for personalized therapy

“…In addition, the tumor would not be a candidate to somatostatin receptor inhibitors, as the somatostatin receptor expression was low, as well. However, the expression analysis showed high overexpression of PRLR and GHRHR , both of these receptors representing known targets for chemotherapy in cancer [ 53 , 54 ]. Prolactin binds PRLR that in turn recruits and activates the JAK-STAT5 pathway, inducing a proliferating response through cyclin D1 transcription [ 55 ].…”