Wnt signalling is activated in both pituitary organogenesis and its mature function. Wnt ligands and Wnt signalling pathways are critical for the regulation of the formation of the pituitary. In the mature pituitary, Wnt signalling pathways control cell activity and may stimulate cell proliferation in both physiological and pathological processes. This review compares Wnt signalling pathways active in the developing and mature pituitary and explores how this gives us further insight into the development of pituitary adenomas.
T J G Chambers, A Giles, G Brabant, and J R E Davis
Iain R Thompson, Annisa N Chand, Peter J King, Olaf Ansorge, Niki Karavitaki, Ceri Alexander Jones, Dolkun Rahmutula, David G Gardner, Vladimir Zivkovic, Caroline P Wheeler-Jones, Imelda M McGonnell, Márta Korbonits, Richard A Anderson, John A H Wass, Alan S McNeilly, and Robert C Fowkes
C-type natriuretic peptide (CNP/Nppc) is expressed at high levels in the anterior pituitary of rats and mice and activates guanylyl cyclase B receptors (GC-B/Npr2) to regulate hormone secretion. Mutations in NPR2/Npr2 can cause achondroplasia, GH deficiency, and female infertility, yet the normal expression profile within the anterior pituitary remains to be established in humans. The current study examined the expression profile and transcriptional regulation of NPR2 and GC-B protein in normal human fetal pituitaries, normal adult pituitaries, and human pituitary adenomas using RT-PCR and immunohistochemistry. Transcriptional regulation of human NPR2 promoter constructs was characterized in anterior pituitary cell lines of gonadotroph, somatolactotroph, and corticotroph origin. NPR2 was detected in all human fetal and adult pituitary samples regardless of age or sex, as well as in all adenoma samples examined regardless of tumor origin. GC-B immunoreactivity was variable in normal pituitary, gonadotrophinomas, and somatotrophinomas. Maximal transcriptional regulation of the NPR2 promoter mapped to a region within −214 bp upstream of the start site in all anterior pituitary cell lines examined. Electrophoretic mobility shift assays revealed that this region contains Sp1/Sp3 response elements. These data are the first to show NPR2 expression in normal human fetal and adult pituitaries and adenomatous pituitary tissue and suggest a role for these receptors in both pituitary development and oncogenesis, introducing a new target to manipulate these processes in pituitary adenomas.
Maria Eugenia Sabatino, Juan Pablo Petiti, Liliana del Valle Sosa, Pablo Anibal Pérez, Silvina Gutiérrez, Carolina Leimgruber, Alexandra Latini, Alicia Inés Torres, and Ana Lucía De Paul
Although pituitary adenomas represent 25% of intracranial tumors, they are usually benign, with the mechanisms by which these tumors usually avoid an invasive profile and metastatic growth development still remaining unclear. In this context, cellular senescence might constitute a plausible explanation for the benign nature of pituitary adenomas. In this study, we investigated the emergence of cellular senescence as a growth control mechanism during the progression of estrogen-induced pituitary tumors. The quantification of Ki67-immunopositive cells in the pituitaries of estrogenized male rats after 10, 20, 40, and 60 days revealed that the mitogenic potential rate was not sustained for the whole period analyzed and successively decreased after 10 days of estrogen exposure. In addition, the expression of cellular senescence features, such as the progressive rise in the enzymatic senescence-associated b-galactosidase (SA-b-gal) activity, IL6, IL1b, and TGFb expression, was observed throughout pituitary tumor development. Furthermore, tumoral pituitary cells also displayed nuclear pATM expression, indicating activated DNA damage signaling, with a significant increase in p21 expression also being detected. The associations among DNA damage signaling activation, SA-b-gal expression, and p21 may provide a reliable combination of senescence-associated markers for in vivo pituitary senescence detection. These results suggest a role for this cellular process in the regulation of pituitary cell growth. Thus, cellular senescence should be conceived as a contributing component to the benign nature of pituitary adenomas, thereby influencing the capability of the pituitary gland to avoid unregulated cell proliferation.
Kari Hemminki, Asta Försti, and Jianguang Ji
Reliable data on familial risks are important for clinical counseling and cancer genetics. We wanted to study incidence trends and familial risks for pituitary adenomas and associated tumors through parental and sibling probands, using the nation-wide Swedish Family-Cancer Database on 10.5 million individuals, containing families with parents and offspring. Cancer data were retrieved from the Swedish Cancer Registry from years 1958 to 2002, including 3239 pituitary tumor patients. Familial risk for offspring was defined through standardized incidence ratio (SIR), adjusted for many variables. The incidence of pituitary adenoma has increased moderately from 1958 to the 1990s and declined thereafter. There were only three offspring–parent pairs with a concordant pituitary tumor, the SIR was not significant. Parental skin cancer (SIR 1.60) and leukemia (1.90, chronic lymphatic leukemia 2.59) were associated with offspring pituitary adenoma diagnosed at any age up to 70 years. There was a strong association of pituitary adenomas with nervous system hemangiopericytomas, SIR 182. The only significant association among siblings was between pituitary tumors and breast cancer (1.46). The risk of pituitary adenoma was marginally increased in individuals whose siblings were diagnosed with colorectal cancer. The results suggest an association of pituitary adenomas with nervous system hemangiopericytomas and breast and colorectal cancers, in addition to some other tumor types. Whether these associations can be explained by the recently identified pituitary adenoma predisposing gene, AIP, remains to be established.
A P Heaney and S Melmed
Pituitary tumors are common monoclonal neoplasms which cause considerable morbidity and mortality. Several molecular events underlying pituitary tumorigenesis have been elucidated in recent years, but no tumor marker has clearly emerged which assists clinical and therapeutic decisions. Activating mutations and loss of inactivating mutations, together with hypothalamic hormones, circulating hormones, growth factors and cytokines cooperatively ensure the inexorable expansion of the initial mutated pituitary cell clone. This review describes new developments in our understanding of the molecular mechanisms involved in the pathogenesis of pituitary tumors. The availability of molecular probes will allow the early prediction of tumor behavior, identify targets for designing subcellular pituitary tumor therapy and provide novel approaches to pituitary tumor management.
Luis V Syro, Fabio Rotondo, Leon D Ortiz, and Kalman Kovacs
Temozolomide is an alkylating chemotherapeutic agent used in malignant neuroendocrine neoplasia, melanoma, brain metastases and an essential component of adjuvant therapy in the treatment of glioblastoma multiforme and anaplastic astrocytoma. Since 2006, it has been used for the treatment of pituitary carcinomas and aggressive pituitary adenomas. Here, we discuss the current indications and results of temozolomide therapy in pituitary tumors, as well as frequently asked questions regarding temozolomide treatment, duration of therapy, dosage, tumor recurrence and resistance.
Paraskevi Xekouki, Emily J Lodge, Jakob Matschke, Alice Santambrogio, John R Apps, Ariane Sharif, Thomas S Jacques, Simon Aylwin, Vincent Prevot, Ran Li, Jörg Flitsch, Stefan R Bornstein, Marily Theodoropoulou, and Cynthia L Andoniadou
Tumours of the anterior pituitary can manifest from all endocrine cell types but the mechanisms for determining their specification are not known. The Hippo kinase cascade is a crucial signalling pathway regulating growth and cell fate in numerous organs. There is mounting evidence implicating this in tumour formation, where it is emerging as an anti-cancer target. We previously demonstrated activity of the Hippo kinase cascade in the mouse pituitary and nuclear association of its effectors YAP/TAZ with SOX2-expressing pituitary stem cells. Here, we sought to investigate whether these components are expressed in the human pituitary and if they are deregulated in human pituitary tumours. Analysis of pathway components by immunofluorescence reveals pathway activity during normal human pituitary development and in the adult gland. Poorly differentiated pituitary tumours (null-cell adenomas, adamantinomatous craniopharyngiomas (ACPs) and papillary craniopharyngiomas (PCPs)), displayed enhanced expression of pathway effectors YAP/TAZ. In contrast, differentiated adenomas displayed lower or absent levels. Knockdown of the kinase-encoding Lats1 in GH3 rat mammosomatotropinoma cells suppressed Prl and Gh promoter activity following an increase in YAP/TAZ levels. In conclusion, we have demonstrated activity of the Hippo kinase cascade in the human pituitary and association of high YAP/TAZ with repression of the differentiated state both in vitro and in vivo. Characterisation of this pathway in pituitary tumours is of potential prognostic value, opening up putative avenues for treatments.
Freya Mertens, Lies Gremeaux, Jianghai Chen, Qiuli Fu, Christophe Willems, Heleen Roose, Olivier Govaere, Tania Roskams, Carolina Cristina, Damasia Becú-Villalobos, Mark Jorissen, Vincent Vander Poorten, Marie Bex, Johannes van Loon, and Hugo Vankelecom
Pituitary adenomas cause significant endocrine and mass-related morbidity. Little is known about the mechanisms that underlie pituitary tumor pathogenesis. In the present study, we searched for a side population (SP) in pituitary tumors representing cells with high efflux capacity and potentially enriched for tumor stem cells (TSCs). Human pituitary adenomas contain a SP irrespective of hormonal phenotype. This adenoma SP, as well as the purified SP (pSP) that is depleted from endothelial and immune cells, is enriched for cells that express ‘tumor stemness’ markers and signaling pathways, including epithelial–mesenchymal transition (EMT)-linked factors. Pituitary adenomas were found to contain self-renewing sphere-forming cells, considered to be a property of TSCs. These sphere-initiating cells were recovered in the pSP. Because benign pituitary adenomas do not grow in vitro and have failed to expand in immunodeficient mice, the pituitary tumor cell line AtT20 was further used. We identified a SP in this cell line and found it to be more tumorigenic than the non-SP ‘main population’. Of the two EMT regulatory pathways tested, the inhibition of chemokine (C-X-C motif) receptor 4 (CXCR4) signaling reduced EMT-associated cell motility in vitro as well as xenograft tumor growth, whereas the activation of TGFβ had no effect. The human adenoma pSP also showed upregulated expression of the pituitary stem cell marker SOX2. Pituitaries from dopamine receptor D2 knockout (Drd2 −/−) mice that bear prolactinomas contain more pSP, Sox2+, and colony-forming cells than WT glands. In conclusion, we detected a SP in pituitary tumors and identified TSC-associated characteristics. The present study adds new elements to the unraveling of pituitary tumor pathogenesis and may lead to the identification of new therapeutic targets.
Chiara Villa, Maria Stefania Lagonigro, Flavia Magri, Maria Koziak, Marie-Lise Jaffrain-Rea, Raja Brauner, Jerome Bouligand, Marie Pierre Junier, Federico Di Rocco, Christian Sainte-Rose, Albert Beckers, François Xavier Roux, Adrian F Daly, and Luca Chiovato
Mutations of the aryl hydrocarbon receptor interacting protein (AIP) gene are associated with pituitary adenomas that usually occur as familial isolated pituitary adenomas (FIPA). Detailed pathological and tumor genetic data on AIP mutation-related pituitary adenomas are not sufficient. Non-identical twin females presented as adolescents to the emergency department with severe progressive headache caused by large pituitary macroadenomas require emergency neurosurgery; one patient had incipient pituitary apoplexy. Post-surgically, the patients were found to have silent somatotrope adenomas on pathological examination. Furthermore, the light microscopic, immunohistochemical, and electron microscopic studies demonstrated tumors of virtually identical characteristics. The adenomas were accompanied by multiple areas of pituitary hyperplasia, which stained positively for GH, indicating somatotrope hyperplasia. Genetic analyses of the FIPA kindred revealed a novel E216X mutation of the AIP gene, which was present in both the affected patients and the unaffected father. Molecular analysis of surgical specimens revealed loss of heterozygosity (LOH) in the adenoma but showed that LOH was not present in the hyperplastic pituitary tissue from either patient. AIP immunostaining confirmed normal staining in the hyperplastic tissue and decreased staining in the adenoma in the tumors from both patients. These results demonstrate that patients with AIP germline mutation can present with silent somatotrope pituitary adenomas. The finding of somatotrope hyperplasia unaccompanied by AIP LOH suggests that LOH at the AIP locus might be a late event in a potential progression from hyperplastic to adenomatous tissue.
M Theodoropoulou, I Cavallari, L Barzon, D M D'Agostino, T Ferro, T Arzberger, Y Gr√ºbler, L Schaaf, M Losa, F Fallo, V Ciminale, G K Stalla, and U Pagotto
Pituitary adenomas represent one of the key features of multiple endocrine neoplasia type 1. The gene involved in this syndrome (MEN1) is a putative tumor suppressor, that codes for a 610-amino acid nuclear protein termed 'menin'. Analyses of sporadic pituitary adenomas have so far failed to reveal MEN1 mutations or defects in MEN1 transcription in these tumors. In the present study we detected menin protein expression in a panel of normal and tumoral pituitary tissues, using a monoclonal antibody against the carboxy-terminus of menin. In the normal human pituitary gland, strong nuclear staining for menin was detectable in the majority of the endocrine cells of the anterior lobe, without a clear association with a particular hormone-producing type. In sporadic pituitary adenomas, menin expression was variable, with a high percentage of cases demonstrating a significant decrease in menin immunoreactivity when compared with the normal pituitary. Interestingly, metastatic tissues derived from one pituitary carcinoma had no detectable menin levels. Altogether, our data provide the first information regarding the status of menin expression in human normal and neoplastic pituitary as determined by immunohistochemistry (IHC).