scholarly journals Reprimo (RPRM) Is a Novel Tumor Suppressor in Pituitary Tumors and Regulates Survival, Proliferation, and Tumorigenicity

Endocrinology ◽  
2012 ◽  
Vol 153 (7) ◽  
pp. 2963-2973 ◽  
Author(s):  
Mei Xu ◽  
Aaron J. Knox ◽  
Katherine A. Michaelis ◽  
Katja Kiseljak-Vassiliades ◽  
Bette K. Kleinschmidt-DeMasters ◽  
...  
Keyword(s):  
Growth Factor ◽  
Tumor Suppressor ◽  
Cellular Stress ◽  
Pituitary Tumors ◽  
Tumor Formation ◽  
Gh3 Cells ◽  
Pituitary Cells ◽  
Null Cell ◽  
Human Pituitary ◽  
Protein Levels

Reprimo (RPRM), initially identified as a downstream effector of p53-induced cell cycle arrest at G2/M, is a putative tumor suppressor silenced in some types of cancer. In microarrays, the RPRM transcript was repressed 26-fold in gonadotrope (null cell) human pituitary tumors compared with normal pituitary but in the absence of changes in p53. Inhibition of RPRM mRNA was confirmed by RT-PCR in all gonadotrope tumors, most GH samples, and variably in other tumor types. Human pituitary tumors showed no evidence of abnormal promoter hypermethylation as a mechanism of RPRM repression. RPRM stable expression in gonadotrope (LβT2) and GH (GH3) pituitary cells resulted in decreased rates of cell proliferation by 55 and 30%, respectively; however, RPRM reexpression did not alter G2/M transition. In addition, RPRM increased rates of apoptosis in response to growth factor deprivation as assessed by caspase-3 cleavage and nuclear condensation. Clonagenic assays showed a 5.3- and 3.7-fold suppression of colony growth in RPRM-overexpressing LβT2 and GH3 cells, respectively, supporting its role as a tumor suppressor. In cells stably expressing RPRM mRNA, protein levels were actively suppressed due to rapid degradation through ubiquitination and proteasomal targeting. Growth factor withdrawal, as a model of cellular stress, stabilized RPRM protein levels. Together these data suggest that RPRM is transiently up-regulated at a posttranscriptional level in times of cellular stress to restrict cell survival, proliferation, and tumor formation. When RPRM is silenced as in human pituitary tumors, unrestrained growth and tumor progression may occur.

scholarly journals Identification of Growth Arrest and DNA-Damage-Inducible Gene β (GADD45β) as a Novel Tumor Suppressor in Pituitary Gonadotrope Tumors

Endocrinology ◽  
2011 ◽  
Vol 152 (10) ◽  
pp. 3603-3613 ◽  
Author(s):  
Katherine A. Michaelis ◽  
Aaron J. Knox ◽  
Mei Xu ◽  
Katja Kiseljak-Vassiliades ◽  
Michael G. Edwards ◽  
...  
Keyword(s):  
Dna Damage ◽  
Tumor Suppressor ◽  
Pituitary Tumor ◽  
Growth Arrest ◽  
Pituitary Tumors ◽  
Bioinformatic Analysis ◽  
Soft Agar ◽  
Null Cell ◽  
Human Pituitary ◽  
Downstream Effectors

Gonadotrope and null cell pituitary tumors cause significant morbidity, often presenting with signs of hypogonadism together with visual disturbances due to mass effects. Surgery and radiation are the only therapeutic options to date. To identify dysregulated genes and pathways that may play a role in tumorigenesis and/or progression, molecular profiling was performed on 14 gonadotrope tumors, with nine normal human pituitaries obtained at autopsy serving as controls. Bioinformatic analysis identified putative downstream effectors of tumor protein 53 (p53) that were consistently repressed in gonadotrope pituitary tumors, including RPRM, P21, and PMAIP1, with concomitant inhibition of the upstream p53 regulator, PLAGL1(Zac1). Further analysis of the growth arrest and DNA damage-inducible (GADD45) family revealed no change in the p53 target, GADD45α, but identified repression of GADD45β in pituitary tumors in addition to the previously reported inhibition of GADD45γ. Overexpression of GADD45β in LβT2 mouse gonadotrope cells blocked tumor cell proliferation and increased rates of apoptosis in response to growth factor withdrawal. Stable gonadotrope cell transfectants expressing increased GADD45β showed decreased colony formation in soft agar, confirming its normal role as a tumor suppressor. Unlike previous studies of GADD45γ in pituitary tumors and α and β in other tumors, bisulfite sequencing showed no evidence of hypermethylation of the GADD45β promoter in human pituitary tumor samples to explain the repression of its expression. Thus, GADD45β is a novel pituitary tumor suppressor whose reexpression blocks proliferation, survival, and tumorigenesis. Together these studies identify new targets and mechanisms to explore in pituitary tumor initiation and progression.

scholarly journals Expression of epidermal growth factor receptor in neoplastic pituitary cells: evidence for a role in corticotropinoma cells

2004 ◽  
Vol 183 (2) ◽  
pp. 385-394 ◽  
Author(s):  
M Theodoropoulou ◽  
T Arzberger ◽  
Y Gruebler ◽  
M L Jaffrain-Rea ◽  
J Schlegel ◽  
...  
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Pituitary Adenomas ◽  
Egf Receptor ◽  
Pituitary Tumors ◽  
Tumor Formation ◽  
Pituitary Cells ◽  
Egfr Expression ◽  
Epidermal Growth ◽  
P27 Kip1

The oncogenic effects of epidermal growth factor (EGF) have long been established. EGF receptor (EGFr) is overexpressed in many types of tumors and constitutes a target for cancer treatment. The pituitary gland is a target of EGF action and it is very likely that EGFr plays a role in pituitary tumor formation and progression. However, there is a controversy in the literature concerning EGFr expression in the different types of pituitary adenomas. In the present study we investigated the expression pattern of the wild type EGFr (EGFrWT) and the constitutively active variant III (EGFrvIII) at the mRNA and protein levels in a large series of pituitary tumors. EGFrWT was found in a high percentage of hormone-secreting tumors, but only in a small fraction of non-functioning pituitary adenomas, while no expression of the EGFrvIII could be detected by nested RT-PCR in any tumor. Among the hormone-secreting adenomas, the highest incidence of EGFr expression was found in Cushing’s pituitary adenomas. Furthermore, immunohistochemistry for the phosphorylated EGFr revealed the presence of activated EGFr in most Cushing’s adenomas, compared with most pituitary adenomas. Taking into account that downregulation of p27/Kip1 plays a significant role in corticotrope tumorigenesis and that EGFr mitogenic signaling results in decreased p27/Kip1, we searched for a correlation between EGFr expression and p27/Kip1 levels in corticotropinomas. Low p27/Kip1 immunoreactivity was observed in corticotropinomas expressing EGFr. On the other hand, somatotropinomas expressing EGFr had high p27/Kip1 immunoreactivity. These data suggest a corticotrope-specific phenomenon and indicate that EGFr may have a role in the unbalanced growth of corticotrope tumoral cells.

scholarly journals Epidermal Growth Factor Receptor Pathway Substrate 8 Is Overexpressed in Human Pituitary Tumors: Role in Proliferation and Survival

Endocrinology ◽  
2008 ◽  
Vol 150 (5) ◽  
pp. 2064-2071 ◽  
Author(s):  
Mei Xu ◽  
Lynnette Shorts-Cary ◽  
Aaron J. Knox ◽  
B Kleinsmidt-DeMasters ◽  
Kevin Lillehei ◽  
...  
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Growth Factor Receptor ◽  
Pituitary Tumors ◽  
Pituitary Cells ◽  
Growth Factor Signaling ◽  
Fibroblast Growth Factor Receptors ◽  
Human Pituitary ◽  
Epidermal Growth ◽  
Induced Apoptosis

Based on prior work showing that human pituitary tumors overexpress epidermal and fibroblast growth factor receptors, we hypothesized that downstream components of growth factor signaling pathways may also be dysregulated. Epidermal growth factor pathway substrate number 8 (Eps8) was identified as a transcript overexpressed (5.9-fold) in human pituitary tumors compared with normal pituitary by DNA microarrays. Eps8 mRNA up-regulation was confirmed by semiquantitative RT-PCR. Immunoblot analysis showed that Eps8 protein levels and its downstream target phosphorylated ERK were also up-regulated in human pituitary tumors. Stable overexpression of Eps8 in LβT2 gonadotrope pituitary cells augmented colony formation in soft agar at d 21. Eps8 cells proliferated more robustly compared with controls in growth factor replete as well as growth-restricted conditions. In addition, the Eps8 overexpressing cells were protected from serum withdrawal-induced apoptosis compared with controls as assessed by caspase-3 cleavage. Epidermal growth factor activated a robust amplification of ERK and modest up-regulation of Akt in Eps8-overexpressing pituitary cells compared with vector controls. MAPK kinase inhibition or silencing of Eps8 blunted the proliferation of the cells in response to growth factor stimulation. Blockade of the phosphatidylinositol 3-kinase pathway or silencing of Eps8 resulted in a loss of the Eps8 protection from growth factor withdrawal-induced apoptosis. Together these data support a role of Eps8 in amplifying growth factor receptor signaling in human pituitary tumors to promote proliferation and cell survival.

scholarly journals Is IGSF1 involved in human pituitary tumor formation?

2015 ◽  
Vol 22 (1) ◽  
pp. 47-54 ◽  
Author(s):  
Fabio R Faucz ◽  
Anelia D Horvath ◽  
Monalisa F Azevedo ◽  
Isaac Levy ◽  
Beata Bak ◽  
...  
Keyword(s):  
Pituitary Tumors ◽  
Tumor Formation ◽  
Sequence Variant ◽  
Healthy Individuals ◽  
Human Pituitary ◽  
Central Hypothyroidism ◽  
Pituitary Tissue ◽  
Expression Studies ◽  
Healthy Female ◽  
Male Patients

IGSF1 is a membrane glycoprotein highly expressed in the anterior pituitary. Pathogenic mutations in the IGSF1 gene (on Xq26.2) are associated with X-linked central hypothyroidism and testicular enlargement in males. In this study, we tested the hypothesis that IGSF1 is involved in the development of pituitary tumors, especially those that produce growth hormone (GH). IGSF1 was sequenced in 21 patients with gigantism or acromegaly and 92 healthy individuals. Expression studies with a candidate pathogenic IGSF1 variant were carried out in transfected cells and immunohistochemistry for IGSF1 was performed in the sections of GH-producing adenomas, familial somatomammotroph hyperplasia, and in normal pituitary. We identified the sequence variant p.N604T, which in silico analysis suggested could affect IGSF1 function, in two male patients and one female with somatomammotroph hyperplasia from the same family. Of 60 female controls, two carried the same variant and seven were heterozygous for other variants. Immunohistochemistry showed increased IGSF1 staining in the GH-producing tumor from the patient with the IGSF1 p.N604T variant compared with a GH-producing adenoma from a patient negative for any IGSF1 variants and with normal control pituitary tissue. The IGSF1 gene appears polymorphic in the general population. A potentially pathogenic variant identified in the germline of three patients with gigantism from the same family (segregating with the disease) was also detected in two healthy female controls. Variations in IGSF1 expression in pituitary tissue in patients with or without IGSF1 germline mutations point to the need for further studies of IGSF1 action in pituitary adenoma formation.

scholarly journals Reexpression of p8 Contributes to Tumorigenic Properties of Pituitary Cells and Appears in a Subset of Prolactinomas in Transgenic Mice that Hypersecrete Luteinizing Hormone

2004 ◽  
Vol 18 (10) ◽  
pp. 2583-2593 ◽  
Author(s):  
Helai P. Mohammad ◽  
Darcie D. Seachrist ◽  
Christine C. Quirk ◽  
John H. Nilson
Keyword(s):  
Transgenic Mice ◽  
Cell Line ◽  
Cell Lines ◽  
Pituitary Tumors ◽  
Gh3 Cells ◽  
Parent Cell ◽  
Pituitary Cells ◽  
Wild Type ◽  
Altered Expression ◽  
Pituitary Tumorigenesis

Abstract Targeted overexpression of LH in transgenic mice causes hyperproliferation of Pit-1-positive pituitary cells and development of functional adenomas. To characterize gene expression changes associated with pituitary tumorigenesis, we performed microarray studies using Affymetrix GeneChips comparing expression profiles from pituitary tumors in LH-overexpressing mice to wild-type control pituitaries. We identified a number of candidate genes with altered expression in pituitary tumors. One of these, p8 (candidate of metastasis-1), encodes a native high-mobility group-like transcription factor previously shown to be necessary for ras-mediated transformation of mouse embryonic fibroblasts and also implicated in breast cancer progression. Herein, we show that expression of p8, normally quiescent in adult pituitary, localizes to tumor foci containing lactotropes, suggesting a linkage with their transformation. To further establish the functional significance of p8 in pituitary tumorigenesis, we constructed several clonal cell lines with reduced expression of p8 from a parent GH3 somatolactotrope cell line. These clonal derivates, along with the parent cell line, were tested for tumorigenicity by injection into athymic mice. When compared with wild-type GH3 with higher levels of p8, GH3 cells with reduced expression of p8 displayed attenuated tumor development or failed to develop tumors at all. Similar results were obtained with gonadotrope-derived cell lines that displayed reduced expression of p8. Together, these data suggest that maintenance of the transformed phenotype of pituitary GH3 cells requires expression of p8 and that it may play a similar role when reexpressed in a subset of lactotropes that form prolactinomas in vivo.

scholarly journals Mutation and expression analysis of the cyclin-dependent kinase inhibitor gene p27/Kip1 in pituitary tumors

1998 ◽  
Vol 157 (2) ◽  
pp. 337-341 ◽  
Author(s):  
S Takeuchi ◽  
HP Koeffler ◽  
DR Hinton ◽  
I Miyoshi ◽  
S Melmed ◽  
...  
Keyword(s):  
Pituitary Tumor ◽  
Structural Changes ◽  
Kinase Inhibitor ◽  
Pituitary Tumors ◽  
Cyclin Dependent Kinase ◽  
Coding Region ◽  
Complex Activity ◽  
Human Pituitary ◽  
Protein Levels ◽  
P27 Kip1

By regulating cyclin-cyclin-dependent kinase (CDK) complex activity, individual CDK inhibitors (CDKIs) are potential tumor suppressors. One of the CDKIs, p27/Kip1, binds to a variety of CDK-cyclin complexes. A link between loss of p27/Kip1 function and development of pituitary tumors was suggested by the formation of pituitary tumors in almost all mice with germline deletion of the p27/Kip1 gene. However, genetic aberrations in the p27/Kip1 locus have not been analyzed in human pituitary tumors. We investigated eighteen non-functioning and GH-secreting pituitary tumor samples for p27/Kip1 mutations by single-strand conformational polymorphism (SSCP) following PCR. We found five abnormally migrating samples on the PCR-SSCP analysis. The sequence of these samples revealed a polymorphism of codon 109 (Val-->Gly), which has been previously described. No other structural changes of p27/Kip1 were found in these pituitary tumors within the coding region. In addition, no difference in p27/Kip1 protein levels in pituitary tumor tissues compared with normal pituitary tissues was demonstrated by immunostaining. These data suggest that both p27/Kip1 mutations and decreases in p27/Kip1 protein levels are infrequent in the development of pituitary tumors.

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