ResearchPad - research-advances-in-pituitary-tumors https://www.researchpad.co Default RSS Feed en-us © 2020 Newgen KnowledgeWorks <![CDATA[OR06-06 Pituitary Tumors and Immortalized Cell Lines Generated by Cre-Inducible Expression of SV40 T-Antigen]]> https://www.researchpad.co/article/elastic_article_6550 Pituitary and hypothalamic cell lines have been developed by targeted oncogenesis. This involved using cell-specific transcriptional regulatory sequences to drive expression of large and small SV40 T-antigens in transgenic mice. Invariably, tumors develop in some of the mice, and the cells in these tumors can sometimes be adapted to grow in culture into stable, immortalized cell lines that maintain some of the features of differentiated cells. Cell lines that represent pre-gonadotropes (αT3-1), gonadotropes (LβT2), precursors to the POU1F1 lineage (GHFT1, Pit1-zero), differentiated cells of the POU1F1 lineage (Pit1-triple, TaT1, and Pit1-PRL), and GnRH neurons (GT1-1) have been made by this approach. Tumors often develop early and cause infertility or death. To increase the opportunity for generating cell lines and to make it feasible to follow the process of tumorigenesis, we developed a mouse strain that expresses SV40 T-antigens in response to cre-recombinase. Using CRISPR/Cas9 we inserted an 8 kb cassette with coding sequences for SV40 T-antigens and IRES-GFP into the Rosa26 locus, downstream from a stop sequence flanked by loxP sites: Rosa26LSL-SV40-GFP. 30% of the progeny born from hybrid zygotes injected with template DNA, CRISPR/Cas9, and sgRNA had correctly targeted the Rosa26 locus. These mice were mated with previously established Prop1-cre and Tshb-cre transgenic lines. The majority of Rosa26LSL-SV40-GFP/+; Prop1-cre and Rosa26LSL-SV40-GFP/+; Tshb-cre mice developed dwarfism and large tumors by 4 wks. The pituitaries of Rosa26LSL-SV40-GFP/+; Tshb-cre mice appear grossly normal at birth, but they are enlarged and showing evidence of increased vascularization by 2 wks. Flow-sorted GFP-positive cells from Rosa26LSL-SV40-GFP/+; Prop1-cre and Rosa26LSL-SV40-GFP/+; Tshb-cre mice express Prop1 and TSH, respectively. Tumors from Rosa26LSL-SV40-GFP/+; Tshb-cre mice were adapted to growth in cell culture. We have established a thyrotrope-like cell line that expresses Cga and Pou1f1. These studies demonstrate the utility of the novel, Rosa26LSL-SV40-GFP mouse line for reliable targeted oncogenesis and development of unique cell lines.

The authors have nothing to disclose.

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<![CDATA[OR06-03 Serotonin Regulates Corticotroph Tumor Cell Proliferation and ACTH Secretion]]> https://www.researchpad.co/article/elastic_article_6231 Serotonin (5-HT) is an important hormonal modulator and neurotransmitter, and 5-HT has been demonstrated in pituitary tissue from several species. Previous responses to 5-HT antagonists have been reported in some patients with Cushing disease although this effect was unsustained, and ACTH and cortisol levels actually increased in some patients. To better understand the role of serotonin in the regulation of corticotroph tumor growth and ACTH secretion, we first measured serotonin levels in supernatants (SNs) derived from murine corticotroph tumor AtT20 cells. We demonstrated that AtT20 cells secrete serotonin (2±0.05ng/105cells/24h) which was ~50% of the levels secreted by the serotonin secreting mid-gut carcinoid BON-1 cell-line (4.2±0.05ng/105cells/24h). In contrast, serotonin secretion was not detected in rat pituitary tumor lactotroph (GH3) or human embryonic kidney (HEK293) cell SNs, or in our Ham’s F12 medium control. Immunocytochemical staining using serotonin specific antibodies demonstrated that serotonin was diffusively present in AtT20 cell cytoplasm, suggesting that serotonin was endogenously generated in the AtT20 cells. Using real-time PCR, we demonstrated that both serotonin synthesis enzymes, tyrosine hydroxylase-1 (THP1) and -2 (THP2) are expressed in AtT20 cells with higher relative THP1 expression, confirming endogenous corticotroph pituitary tumor serotonin production. We further demonstrated that the synthetic glucocorticoid Dexamethasone (100nM x 24h) suppressed TPH1 expression and inhibited corticotroph tumor serotonin secretion. We next evaluated the actions of serotonin and various serotonin antagonists on corticotroph tumor cell proliferation and ACTH secretion. Ritanserin (10-5M) inhibited murine corticotroph tumor proliferation by 5% and inhibited ACTH secretion by ~25%. In contrast, metergoline (10-5M) and the orally administered TPH inhibitor, telotristat etiprate (10-5M for 1-3 days), inhibited ACTH secretion by 50% and 30% respectively but did not reduce cell proliferation, suggesting that Metergoline and telotristat may regulate ACTH secretion independently of their anti-proliferative effect. Addition of serotonin (10-4~10-5M) to corticotroph tumor cells cultured in reduced serum (OptiMEM) or no serum conditions, resulted in an 80% increase in cell proliferation but had little effect on ACTH secretion with a 1-4% increase. In summary, we have demonstrated that serotonin is synthesized in and secreted from corticotroph tumor cells and that serotonin plays a role in regulation of corticotroph tumor proliferation and ACTH secretion in vitro. Our findings using inhibitors of serotonin action indicate potential for targeting this pathway as a novel treatment for patients with CD.

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<![CDATA[OR06-04 Tissue-Specific Tumorigenesis in Multiple Endocrine Neoplasia Type I]]> https://www.researchpad.co/article/N366fc7b6-5c23-45d8-8487-6de2af41a81b <![CDATA[OR06-02 TBR-760, a Chimeric Somatostatin-Dopamine Compound, Arrests Aggressive Non-Functioning Pituitary Adenoma Growth In Vivo]]> https://www.researchpad.co/article/N322b1455-1812-4f4e-9baf-2b14a35101f8 <![CDATA[OR06-05 Inadequate High Mitochondrial ATP-Synthesis Explains “Non-Fatty-Liver” in Patients with Acromegaly]]> https://www.researchpad.co/article/N2f37b4b4-465a-4645-a1ba-a896f3288359 <![CDATA[OR06-01 The Role of Germline Defects in Cushing’s Disease]]> https://www.researchpad.co/article/Nb98415e5-194d-44df-83c2-e2c83bf97744