Somatotropinomas, But Not Nonfunctioning Pituitary Adenomas, Maintain a Functional Apoptotic RET/Pit1/ARF/p53 Pathway That Is Blocked by Excess GDNF

Abstract Acromegaly is caused by somatotroph cell adenomas (somatotropinomas [ACROs]), which secrete GH. Human and rodent somatotroph cells express the RET receptor. In rodents, when normal somatotrophs are deprived of the RET ligand, GDNF (Glial Cell Derived Neurotrophic Factor), RET is processed intracellularly to induce overexpression of Pit1 [Transcription factor (gene : POUF1) essential for transcription of Pituitary hormones GH, PRL and TSHb], which in turn leads to p19Arf/p53-dependent apoptosis. Our purpose was to ascertain whether human ACROs maintain the RET/Pit1/p14ARF/p53/apoptosis pathway, relative to nonfunctioning pituitary adenomas (NFPAs). Apoptosis in the absence and presence of GDNF was studied in primary cultures of 8 ACROs and 3 NFPAs. Parallel protein extracts were analyzed for expression of RET, Pit1, p19Arf, p53, and phospho-Akt. When GDNF deprived, ACRO cells, but not NFPAs, presented marked level of apoptosis that was prevented in the presence of GDNF. Apoptosis was accompanied by RET processing, Pit1 accumulation, and p14ARF and p53 induction. GDNF prevented all these effects via activation of phospho-AKT. Overexpression of human Pit1 (hPit1) directly induced p19Arf/p53 and apoptosis in a pituitary cell line. Using in silico studies, 2 CCAAT/enhancer binding protein alpha (cEBPα) consensus-binding sites were found to be 100% conserved in mouse, rat, and hPit1 promoters. Deletion of 1 cEBPα site prevented the RET-induced increase in hPit1 promoter expression. TaqMan qRT-PCR (real time RT-PCR) for RET, Pit1, Arf, TP53, GDNF, steroidogenic factor 1, and GH was performed in RNA from whole ACRO and NFPA tumors. ACRO but not NFPA adenomas express RET and Pit1. GDNF expression in the tumors was positively correlated with RET and negatively correlated with p53. In conclusion, ACROs maintain an active RET/Pit1/p14Arf/p53/apoptosis pathway that is inhibited by GDNF. Disruption of GDNF's survival function might constitute a new therapeutic route in acromegaly.

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The immunohistochemical and radiological features of nonfunctioning pituitary adenomas

Problems of Endocrinology ◽

10.14341/probl20156164-9 ◽

2015 ◽

Vol 61 (6) ◽

pp. 4-9 ◽

Cited By ~ 1

Author(s):

Anna Konstantinovna Lipatenkova ◽

Larisa Konstantinovna Dzeranova ◽

Ekaterina Aleksandrovna Pigarova ◽

Nadezhda Sergeevna Dalantaeva ◽

Ljudmila Igorevna Astaf'eva ◽

...

Keyword(s):

Pituitary Adenomas ◽

Area Under The Curve ◽

Pituitary Hormones ◽

Serum Markers ◽

Invasive Growth ◽

Null Cell ◽

Ki 67 ◽

Nonfunctioning Pituitary Adenomas ◽

Radiological Features ◽

Null Cell Adenomas

Pituitary adenomas without clinically active hypersecretion are summarized under the term nonfunctioning pituitary adenomas (NFPAs). Since there are no specific serum markers, the differential diagnosis and treatment imply special difficulties.Aim.To investigate the immunohistochemical and radiological features of NFPAs and assess the granins — chromogranin A (CgA), secretogranin II (SgII), secretoneurin (Sn) as immunohistochemical markers of NFPAs.Matherial and methods.50 pituitary adenomas excised surgically were immunostained to reveal pituitary hormones, ki-67, CgА. SgII, Sn. All patients underwent MRI, invasive growth was estimated due to J.Hardy classification (1973).Results.24 (51,1%) were gonadotropic tumors, 12 (25,5%) — null cell adenomas. Immunopositivity for ACTH was determined in 6 cases (12,7%), for GH in 5 (10,6%) cases, for PRL in 4 (8,5%). The median level of ki-67 was 2% (min. — 0.5%, max. — 7%). The CgA, SgII, Sn immunopositivity was found in 83, 93,6, 85,1% respectively, being more expressed in gonadotropinomas and null cell adenomas. Invasive growth was detected in 28 (44%) cases, among the invasive adenomas 22 tumors were giant. CgA expression is adverse prognostic factor, area under the curve (AUC) with 0,705. We did not find any correlation between ACTH-, STH-, CgII- and Sn- immunopositivity, ki-67 and invasive growth.Conclusions.Our work shows that a majority of NFPAs are truly secreting adenomas with significant numbers comprising potentially hazardous cortico- and somatotropinomas. CgA, SgII and Sn have a high expression in most of the NFPAs.

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Selective Loss of MEG3 Expression and Intergenic Differentially Methylated Region Hypermethylation in the MEG3/DLK1 Locus in Human Clinically Nonfunctioning Pituitary Adenomas

The Journal of Clinical Endocrinology & Metabolism ◽

10.1210/jc.2007-2633 ◽

2008 ◽

Vol 93 (10) ◽

pp. 4119-4125 ◽

Cited By ~ 88

Author(s):

Roger Gejman ◽

Dalia L. Batista ◽

Ying Zhong ◽

Yunli Zhou ◽

Xun Zhang ◽

...

Keyword(s):

Pituitary Adenomas ◽

Cell Types ◽

Pituitary Cell ◽

Differentially Methylated Region ◽

Tumor Type ◽

Cell Type ◽

Rt Pcr ◽

Human Pituitary ◽

Nonfunctioning Pituitary Adenomas ◽

Normal Human

Context: MEG3 is an imprinted gene encoding a novel noncoding RNA that suppresses tumor cell growth. Although highly expressed in the normal human pituitary, it is unknown which of the normal pituitary cell types and pituitary tumors express MEG3. Objectives: Our objectives were 1) to investigate cell-type- and tumor-type-specific expression of MEG3 in the human pituitary and 2) to investigate whether methylation in the intergenic differentially methylated region (IG-DMR) at the DLK1/MEG3 locus is involved in the loss of MEG3 expression in tumors. Design and Methods: RT-PCR, quantitative RT-PCR, Northern blot, and a combination of in situ hybridization and immunofluorescence were used to determine the cell-type- and tumor-type-specific MEG3 expression. Bisulfite treatment and PCR sequencing of genomic DNA were used to measure the CpG methylation status in the normal and tumor tissues. Five normal human pituitaries and 17 clinically nonfunctioning, 11 GH-secreting, seven prolactin-secreting, and six ACTH-secreting pituitary adenomas were used. Results: All normal human pituitary cell types express MEG3. However, loss of MEG3 expression occurs only in nonfunctioning pituitary adenomas of a gonadotroph origin. All other pituitary tumor phenotypes examined express MEG3. Hypermethylation of the IG-DMR at the DLK1/MEG3 locus is present in nonfunctioning pituitary adenomas. Conclusions: MEG3 is the first human gene identified expressed in multiple normal human pituitary cell types with loss of expression specifically restricted to clinically nonfunctioning pituitary adenomas. The IG-DMR hypermethylation may be an additional mechanism for MEG3 gene silencing in such tumors.

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Long-term results in transsphenoidal removal of nonfunctioning pituitary adenomas

Journal of Neurosurgery ◽

10.3171/jns.1986.64.5.0713 ◽

1986 ◽

Vol 64 (5) ◽

pp. 713-719 ◽

Cited By ~ 222

Author(s):

Michael J. Ebersold ◽

Lynn M. Quast ◽

Edward R. Laws ◽

Berndt Scheithauer ◽

Raymond V. Randall

Keyword(s):

Pituitary Adenomas ◽

Mass Effect ◽

Pituitary Hormones ◽

Long Term Results ◽

Null Cell ◽

Content Type ◽

Nonfunctioning Pituitary Adenomas ◽

Presenting Symptoms

✓ Little has been written about the long-term results of transsphenoidal treatment for clinically nonfunctioning pituitary adenomas. The records of 100 patients who had undergone a transsphenoidal procedure for excision of such tumors were reviewed. Immunocytology for pituitary hormones was performed in all cases. The group consisted predominantly of null-cell adenomas, although a small number of prolactinomas and gonadotropic tumors were found. The mean diameter of the tumors at the time of detection was slightly more than 2 cm. In most cases, the presenting symptoms were due to the mass effect of the tumor (that is, visual symptoms in 72 patients, hypopituitarism in 61, headache in 36, and cranial nerve disturbance other than visual loss in 10). Radiation therapy was recommended for patients in whom subtotal removal of the adenoma was expected. Six patients developed symptomatic tumor recurrence, and 10 patients demonstrated radiographic recurrence during the 48 to 100 months (mean 73.4 months) of follow-up observation. Only three of 10 deaths during the follow-up period were due to pituitary disease or treatment.

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TBR-760, a Dopamine-Somatostatin Compound, Arrests Growth of Aggressive Nonfunctioning Pituitary Adenomas in Mice

Endocrinology ◽

10.1210/endocr/bqaa101 ◽

2020 ◽

Vol 161 (8) ◽

Cited By ~ 1

Author(s):

Heather A Halem ◽

Ute Hochgeschwender ◽

Jeong Keun Rih ◽

Richard Nelson ◽

G Allan Johnson ◽

...

Keyword(s):

Mouse Model ◽

Tumor Growth ◽

Pituitary Adenomas ◽

Messenger Rna ◽

Expression Profiles ◽

Primary Cultures ◽

Nonfunctioning Pituitary Adenomas ◽

Mouse Tumors ◽

The Individual

Abstract TBR-760 (formerly BIM-23A760) is a chimeric dopamine (DA)-somatostatin (SST) compound with potent agonist activity at both DA type 2 (D2R) and SST type 2 (SSTR2) receptors. Studies have shown that chimeric DA-SST compounds are more efficacious than individual DA and/or SST analogues, either alone or combined, in inhibiting secretion from primary cultures of human somatotroph and lactotroph tumor cells. Nonfunctioning pituitary adenomas (NFPAs) express both D2R and SSTR2 and, consequently, may respond to TBR-760. We used a mouse model with the pro-opiomelanocortin (POMC) gene knocked out that spontaneously develops aggressive NFPAs. Genomic microarray and DA and SST receptor messenger RNA expression analysis indicate that POMC KO mouse tumors and human NFPAs have similar expression profiles, despite arising from different cell lineages, establishing POMC KO mice as a model for study of NFPAs. Treatment with TBR-760 for 8 weeks resulted in nearly complete inhibition of established tumor growth, whereas tumors from vehicle-treated mice increased in size by 890 ± 0.7%. Comparing TBR-760 with its individual DA and SST components, TBR-760 arrested tumor growth. Treatment with equimolar or 10×-higher doses of the individual SST or DA agonists, either alone or in combination, had no significant effect. One exception was the lower dose of DA agonist that induced modest suppression of tumor growth. Only the chimeric compound TBR-760 arrested tumor growth in this mouse model of NFPA. Further, significant tumor shrinkage was observed in 20% of the mice treated with TBR-760. These results support the development of TBR-760 as a therapy for patients with NFPA.

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Detection of mRNA of prolactin and ACTH in clinically nonfunctioning pituitary adenomas

Journal of Neurosurgery ◽

10.3171/jns.1988.69.5.0653 ◽

1988 ◽

Vol 69 (5) ◽

pp. 653-659 ◽

Cited By ~ 23

Author(s):

Tsuyoshi Sakurai ◽

Hisao Seo ◽

Naohito Yamamoto ◽

Takashi Nagaya ◽

Toshichi Nakane ◽

...

Keyword(s):

Pituitary Adenomas ◽

Adrenocorticotropic Hormone ◽

Pituitary Hormones ◽

Hybridization Technique ◽

Content Type ◽

Hormone Synthesis ◽

Messenger Ribonucleic Acid ◽

Nonfunctioning Pituitary Adenomas ◽

Tumor Tissues ◽

Fine Print

✓ Clinically nonfunctioning pituitary adenomas have been thought to synthesize some pituitary hormones as shown by studies involving cell culture, immunocytochemistry, or measurement of hormone levels in tumor homogenates. Nevertheless, they are not associated with hypersecretion of pituitary hormones. To further clarify hormone synthesis in such pituitary adenomas, the presence of messenger ribonucleic acid (mRNA) of prolactin (PRL) growth hormone, and adrenocorticotropic hormone (ACTH) in the cytoplasm of 16 nonfunctioning adenomas was determined by means of a hybridization technique, and compared to the immunocytochemical findings. In three adenomas (19%) PRL mRNA was detected and in one case (6%) ACTH mRNA was detected. The hybridization technique appears to be more sensitive than immunohistochemistry for detection of specific mRNA's in assigning the hormone synthesis potential to clinically nonfunctioning tumors. The results suggest that PRL and ACTH are synthesized in some cases of clinically nonfunctioning pituitary adenomas and that hybridization techniques are useful to investigate hormone synthesis in pituitary adenomas. The ability to demonstrate PRL mRNA in tumor tissues allowed differentiation between hyperprolactinemia caused by synthesis of PRL in the tumor and that due to hypersecretion from the adjacent normal pituitary.

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