scholarly journals Cytoskeleton Protein Filamin A Is Required for Efficient Somatostatin Receptor Type 2 Internalization and Recycling through Rab5 and Rab4 Sorting Endosomes in Tumor Somatotroph Cells

2019 ◽  
Vol 110 (7-8) ◽  
pp. 642-652 ◽  
Author(s):  
Donatella Treppiedi ◽  
Federica Mangili ◽  
Elena Giardino ◽  
Rosa Catalano ◽  
Marco Locatelli ◽  
...  
Keyword(s):  
Cultured Cells ◽  
Somatostatin Receptor ◽  
Somatostatin Analogs ◽  
Human Tumor ◽  
Pituitary Tumors ◽  
Confocal Imaging ◽  
Gh3 Cells ◽  
Filamin A ◽  
Small Interfering Rnas ◽  
Control Versus

The high expression of somatostatin receptor 2 (SST2) in growth hormone (GH)-secreting tumors represents the rationale for the clinical use of somatostatin analogs (SSAs) in acromegaly. Recently, the cytoskeletal protein Filamin A (FLNA) has emerged as key modulator of the responsiveness of GH-secreting pituitary tumors to SSAs by regulating SST2 signaling and expression. The aim of this study was to explore FLNA involvement in SST2 intracellular trafficking in tumor somatotroph cells. By biotinylation assay, we found that FLNA silencing abolished octreotide-mediated SST2 internalization in rat GH3 cell line (28.0 ± 2.7 vs. 4 ± 4.3% SST2 internalization, control versus FLNA small interfering RNAs (siRNA) cells, respectively, p < 0.001) and human GH-secreting primary cultured cells (70.3 ± 21.1 vs. 24 ± 19.2% SST2 internalization, control versus FLNA siRNA cells, respectively, p < 0.05). In addition, confocal imaging revealed impaired SST2 recycling to the plasma membrane in FLNA silenced GH3 cells. Coimmunoprecipitation and immunofluorescence experiments showed that FLNA, as well as β-arrestin2, is timely dependent recruited to octreotide-stimulated SST2 receptors both in rat and human tumor somatotroph cells. Although FLNA expression knock down did not prevent the formation of β-arrestin2-SST2 complex in GH3 cells, it significantly impaired efficient SST2 loading into cytosolic vesicles positive for the early endocytic and recycling markers Rab5 and 4, respectively (33.7 ± 8.9% down to 25.9 ± 6.9%, p < 0.05, and 28.4 ± 7.4% down to 17.6 ± 5.7%, p < 0.01, for SST2-Rab5 and SST2-Rab4 colocalization, respectively, in control versus FLNA siRNA cells). Altogether these data support an important role for FLNA in the mediation of octreotide-induced SST2 trafficking in GH-secreting pituitary tumor cells through Rab5 and 4 sorting endosomes.

scholarly journals Filamin A (FLNA) Plays an Essential Role in Somatostatin Receptor 2 (SST2) Signaling and Stabilization After Agonist Stimulation in Human and Rat Somatotroph Tumor Cells

Endocrinology ◽  
2014 ◽  
Vol 155 (8) ◽  
pp. 2932-2941 ◽  
Author(s):  
E. Peverelli ◽  
E. Giardino ◽  
D. Treppiedi ◽  
E. Vitali ◽  
V. Cambiaghi ◽  
...  
Keyword(s):  
Tumor Cells ◽  
Molecular Mechanisms ◽  
Somatostatin Receptor ◽  
Pituitary Tumors ◽  
Dominant Negative ◽  
Gh3 Cells ◽  
Dominant Negative Mutant ◽  
Filamin A ◽  
Variable Expression ◽  
Apoptotic Effect

Somatostatin receptor type 2 (SST2) is the main pharmacological target of medical therapy for GH-secreting pituitary tumors, but molecular mechanisms regulating its expression and signaling are largely unknown. The aim of this study was to investigate the role of cytoskeleton protein filamin A (FLNA) in SST2 expression and signaling in somatotroph tumor cells. We found a highly variable expression of FLNA in human GH-secreting tumors, without a correlation with SST2 levels. FLNA silencing in human tumoral cells did not affect SST2 expression and localization but abolished the SST2-induced reduction of cyclin D1 (−37% ± 15% in control cells, P &lt; .05 vs basal) and caspase-3/7 activation (+63% ± 31% in control cells, P &lt; .05 vs basal). Overexpression of a FLNA dominant-negative mutant that specifically prevents SST2-FLNA binding reduced SST2 expression after prolonged agonist exposure (−55% ± 5%, P &lt; .01 vs untreated cells) in GH3 cells. Moreover, SST2-induced apoptotic effect (77% ± 54% increase of caspase activity, P &lt; .05 vs basal) and SST2-mediated ERK1/2 inhibition (48% ± 17% reduction of ERK1/2 phosphorylation, P &lt; .01 vs basal) were abrogated in cells overexpressing another FLNA mutant that prevents FLNA interaction with partner proteins but not with SST2, suggesting a scaffold function of FLNA in somatotrophs. In conclusion, these data demonstrate that FLNA is involved in SST2 stabilization and signaling in tumoral somatotrophs, playing both a structural and functional role.

scholarly journals Octreotide promotes apoptosis in human somatotroph tumor cells by activating somatostatin receptor type 2

2006 ◽  
Vol 13 (3) ◽  
pp. 955-962 ◽  
Author(s):  
E Ferrante ◽  
C Pellegrini ◽  
S Bondioni ◽  
E Peverelli ◽  
M Locatelli ◽  
...  
Keyword(s):  
Tumor Cells ◽  
Cultured Cells ◽  
Somatostatin Receptor ◽  
Hormone Secretion ◽  
Somatostatin Analogs ◽  
Receptor Type ◽  
Apoptotic Activity ◽  
Long Acting ◽  
Induced Apoptosis

Somatostatin analogs currently used in the treatment of acromegaly and other neuroendocrine tumors inhibit hormone secretion and cell proliferation by binding to somatostatin receptor type (SST) 2 and 5. The antiproliferative pathways coupled to these receptors have been only partially characterized. The aim of this study was to evaluate the effect of octreotide and super selective SST2 (BIM23120) and SST5 (BIM23206) analogs on apoptotic activity and apoptotic gene expression in human somatotroph tumor cells. Eight somatotroph tumors expressing similar levels of SST2 and SST5 evaluated by real-time PCR and western blot analyses were included in the study. In cultured cells obtained from these tumors, octreotide induced a dose-dependent increase of caspase-3 activity (160 ± 20% vs basal at 10 nM) and cleaved cytokeratin 18 levels (172 ± 25% vs basal) at concentrations higher than 0.1 nM. This effect was due to SST2 activation since BIM23120 elicited comparable responses, while BIM23206 was ineffective. BIM23120-stimulated apoptosis was dependent on phosphatases, since it was abrogated by the inhibitor orthovanadate, and independent from the induction of apoptosis-related genes, such as p53, p63, p73, Bcl-2, Bax, BID, BIK, TNFSF8, and FADD. In somatotroph tumors, both BIM23120 and BIM2306 caused growth arrest as indicated by the increase in p27 and decrease in cyclin D1 expression. In conclusion, the present study showed that octreotide-induced apoptosis in human somatotroph tumor cells by activating SST2. This effect, together with the cytostatic action exerted by both SST2 and SST5 analogs, might account for the tumor shrinkage observed in acromegalic patients treated with long-acting somatostatin analogs.

scholarly journals X-linked acrogigantism syndrome: clinical profile and therapeutic responses

2015 ◽  
Vol 22 (3) ◽  
pp. 353-367 ◽  
Author(s):  
Albert Beckers ◽  
Maya Beth Lodish ◽  
Giampaolo Trivellin ◽  
Liliya Rostomyan ◽  
Misu Lee ◽  
...  
Keyword(s):  
Anterior Pituitary ◽  
Tumor Tissue ◽  
Clinical Phenotype ◽  
Somatostatin Receptor ◽  
Somatostatin Analogs ◽  
Pituitary Tumors ◽  
Receptor Subtype ◽  
Sporadic Cases ◽  
Somatostatin Receptor Subtype 2 ◽  
Median Height

X-linked acrogigantism (X-LAG) is a new syndrome of pituitary gigantism, caused by microduplications on chromosome Xq26.3, encompassing the geneGPR101, which is highly upregulated in pituitary tumors. We conducted this study to explore the clinical, radiological, and hormonal phenotype and responses to therapy in patients with X-LAG syndrome. The study included 18 patients (13 sporadic) with X-LAG and microduplication of chromosome Xq26.3. All sporadic cases had unique duplications and the inheritance pattern in two families was dominant, with all Xq26.3 duplication carriers being affected. Patients began to grow rapidly as early as 2–3 months of age (median 12 months). At diagnosis (median delay 27 months), patients had a median height and weight standard deviation scores (SDS) of >+3.9 SDS. Apart from the increased overall body size, the children had acromegalic symptoms including acral enlargement and facial coarsening. More than a third of cases had increased appetite. Patients had marked hypersecretion of GH/IGF1 and usually prolactin, due to a pituitary macroadenoma or hyperplasia. Primary neurosurgical control was achieved with extensive anterior pituitary resection, but postoperative hypopituitarism was frequent. Control with somatostatin analogs was not readily achieved despite moderate to high levels of expression of somatostatin receptor subtype-2 in tumor tissue. Postoperative use of adjuvant pegvisomant resulted in control of IGF1 in all five cases where it was employed. X-LAG is a new infant-onset gigantism syndrome that has a severe clinical phenotype leading to challenging disease management.

scholarly journals Novel chimeric somatostatin analogs: facts and perspectives

2007 ◽  
Vol 156 (suppl_1) ◽  
pp. S23-S28 ◽  
Author(s):  
Diego Ferone ◽  
Alexandru Saveanu ◽  
Michael D Culler ◽  
Marica Arvigo ◽  
Alberto Rebora ◽  
...  
Keyword(s):  
Human Cell ◽  
Pituitary Adenomas ◽  
Somatostatin Receptor ◽  
Somatostatin Analogs ◽  
Pituitary Tumors ◽  
Receptor Activation ◽  
Specific Cell ◽  
Pituitary Cells ◽  
Dopaminergic Drugs ◽  
Cell Functions

Dopamine and somatostatin receptor agonists inhibit hormone secretion by normal pituitary cells and pituitary adenomas. Indeed, initially several dopaminergic drugs, and lately somatostatin analogs, have been developed for the treatment of pituitary adenomas. Recently, it has been demonstrated that subtypes of somatostatin and dopamine receptors may form homo- and hetero-dimers at the membrane level, as part of their normal trafficking and function. Interestingly, a specific ligand for a given receptor may influence the activity of an apparently unrelated receptor, and the association between the two different receptors could be induced by addition of either dopamine or somatostatin. The new properties of these families of G-protein coupled receptors (GPCRs) offer a potential explanation for the apparent conflicting results observed both in vivo and in vitro in human cell systems treated with the presently available analogs. Moreover, this observation not only increases the possibilities of modulating the activities of these receptors, but also raises new questions on the role of associations of specific receptors in the control of cell functions. In fact, results from preclinical studies have shown that receptor activation may not only trigger different intracellular signaling pathways, but also induce a distinct response depending upon the specific cell type. Recently, a number of new interesting compounds (subtype selective analogs and antagonists, as well as bi-specific and hybrid somatostatin/dopamine compounds) have been developed. The effects of these new molecules have been explored in few animal and human cell lines and primary cultures from human tumors, revealing a heterogeneous, but broader, profile of activities. Further studies are certainly needed to fully elucidate the complex interplay between the GPCRs and consequent biological effects, to identify suitable therapies for controlling hormonal secretion of pituitary tumors. However, these recent observations form the basis for the application of new interesting strategies for the treatment of not only pituitary tumors but also other human malignancies.

scholarly journals Gender-Specific Efficacy Revealed by Head-to-Head Comparison of Pasireotide and Octreotide in a Representative In Vivo Model of Nonfunctioning Pituitary Tumors

Cancers ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 3097
Author(s):  
Sebastian Gulde ◽  
Tobias Wiedemann ◽  
Mathias Schillmaier ◽  
Isabel Valença ◽  
Amelie Lupp ◽  
...  
Keyword(s):  
Somatostatin Receptor ◽  
Somatostatin Analogs ◽  
Pituitary Tumors ◽  
Male Rats ◽  
In Vivo Model ◽  
Tumor Bearing ◽  
Representative Model ◽  
Long Acting ◽  
Gender Specific

Invasive nonfunctioning pituitary tumors (NFPTs) are non-resectable neoplasms associated with frequent relapse and significant comorbidities. Current treatments, including somatostatin receptor 2 (SSTR2)-directed somatostatin analogs (SSAs), often fail against NFPTs. Thus, identifying effective therapies is clinically relevant. As NFPTs express SSTR3 at high levels, pasireotide, a multireceptor-targeted SSA, might be beneficial. Here we evaluated pasireotide in the only representative model of spontaneous NFPTs (MENX rats) in vivo. Octreotide long-acting release (LAR), pasireotide LAR, or placebo, were administered to age-matched, tumor-bearing MENX rats of both sexes for 28 d or 56 d. Longitudinal high-resolution magnetic resonance imaging monitored tumor growth. While tumors in placebo-treated rats increased in volume over time, PTs in drug-treated rats displayed significant growth suppression, and occasional tumor shrinkage. Pasireotide elicited stronger growth inhibition. Radiological responses correlated with tumors’ proliferation rates. Both SSAs, but especially pasireotide, were more effective in female vs. male rats. Basal Sstr3 expression was significantly higher in the former group. It is noteworthy that female human NFPTs patients also have a trend towards higher SSTR3 expression. Altogether, our studies provide the rationale for testing pasireotide in patients with residual/recurrent NFPTs. If confirmed, the sex-related SSTR3 expression might be used as criteria to stratify NFPTs patients for treatment with pasireotide.

Somatostatin receptor type 5 modulation by Filamin A in ACTH-secreting pituitary tumors

2019 ◽  
Author(s):  
Donatella Treppiedi ◽  
Elena Giardino ◽  
Rosa Catalano ◽  
Federica Mangili ◽  
Marco Locatelli ◽  
...  
Keyword(s):  
Somatostatin Receptor ◽  
Pituitary Tumors ◽  
Receptor Type ◽  
Filamin A ◽  
Acth Secreting

Ultrastructural Correlations between Clonal Human Tumor Colonies and in Vivo Neoplasms

1982 ◽  
Vol 40 ◽  
pp. 210-211
Author(s):  
M.J. Murphy ◽  
R.R. Price ◽  
J.C. Sloman
Keyword(s):  
Cultured Cells ◽  
Human Tumor ◽  
Cell Type ◽  
Tumor Mass ◽  
Initial Cell ◽  
Cloning Assay ◽  
Human Tumor Cloning ◽  
The Relationship

The in vitro human tumor cloning assay originally described by Salmon and Hamburger has been applied recently to the investigation of differential anti-tumor drug sensitivities over a broad range of human neoplasms. A major problem in the acceptance of this technique has been the question of the relationship between the cultured cells and the original patient tumor, i.e., whether the colonies that develop derive from the neoplasm or from some other cell type within the initial cell population. A study of the ultrastructural morphology of the cultured cells vs. patient tumor has therefore been undertaken to resolve this question. Direct correlation was assured by division of a common tumor mass at surgical resection, one biopsy being fixed for TEM studies, the second being rapidly transported to the laboratory for culture.

Ultrastructure of two neoplasms in culture compared with original biopsies

1984 ◽  
Vol 42 ◽  
pp. 50-51
Author(s):  
Joseph M. Harb ◽  
James T. Casper ◽  
Vlcki Piaskowski
Keyword(s):  
Electron Microscopy ◽  
Tissue Culture ◽  
Biopsy Specimen ◽  
Cultured Cells ◽  
Light And Electron Microscopy ◽  
Human Tumor ◽  
Soft Agar ◽  
Human Tumor Cells ◽  
Morphological Distinction ◽  
Tumor Types

The application of tissue culture and the newer methodologies of direct cloning and colony formation of human tumor cells in soft agar hold promise as valuable modalities for a variety of diagnostic studies, which include morphological distinction between tumor types by electron microscopy (EM). We present here two cases in which cells in culture expressed distinct morphological features not apparent in the original biopsy specimen. Evaluation of the original biopsies by light and electron microscopy indicated both neoplasms to be undifferentiated sarcomas. Colonies of cells propagated in soft agar displayed features of rhabdomyoblasts in one case, and cultured cells of the second biopsy expressed features of Ewing's sarcoma.

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