Wnt signalling in pituitary development and tumorigenesis

Central Endocrine Complications Among Childhood Cancer Survivors Treated With Radiation Therapy: A PENTEC Comprehensive Review

PURPOSE

Children who receive cranial radiation therapy (RT) as a component of treatment for malignancy are often at risk of long-term central endocrine toxicity secondary to radiation to the hypothalamic-pituitary axis (HPA). A comprehensive analysis was performed of central endocrine late effects in survivors of childhood cancer treated with RT as part of the Pediatric Normal Tissue Effects in the Clinic (PENTEC) consortium.

METHODS AND MATERIALS

A systematic review of the risk of RT-related central endocrine effects was performed in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). A total of 4629 publications were identified, of which 16 met criteria for inclusion in dose modeling analysis, with a total of 570 patients in 19 cohorts. Eighteen cohorts reported outcomes for growth hormone deficiency (GHD), 7 reported outcomes for central hypothyroidism (HT), and 6 reported outcomes for adrenocorticotropic hormone (ACTH) deficiency.

RESULTS

Normal tissue complication probability modeling for GHD (18 cohorts, 545 patients) yielded D50 = 24.9 Gy (95% CI, 20.9-28.0) and γ50 = 0.5 (95% CI, 0.27-0.78). The normal tissue complication probability model fit for whole brain irradiation in children with a median age of >5 years indicated a 20% risk of GHD for patients who receive a mean dose of 21 Gy in 2-Gy fractions to the HPA. For HT, among 7 cohorts (250 patients), D50 = 39 Gy (95% CI, 34.1-53.2) and γ50 = 0.81 (95% CI, 0.46-1.35), with a 20% risk of HT in children who receive a mean dose of 22 Gy in 2-Gy fractions to the HPA. For ACTH deficiency (6 cohorts, 230 patients), D50 = 61 Gy (95% CI, 44.7-119.4) and γ50 = 0.76 (95% CI, 0.5-1.19); there is a 20% risk of ACTH deficiency in children who receive a mean dose of 34 Gy in 2-Gy fractions to the HPA.

CONCLUSIONS

RT dose to the HPA increases the risk of central endocrine toxicity, including GHD, HT, and ACTH deficiency. In some clinical situations, these toxicities may be difficult to avoid, and counseling of patients and families with respect to anticipated outcomes is important.

Glycoprotein hormone subunit alpha 2 (GPHA2): A pituitary stem cell-expressed gene associated with NOTCH2 signaling

NOTCH2 is expressed in pituitary stem cells and is necessary for stem cell maintenance, proliferation, and differentiation. However, the pathways NOTCH2 engages to affect pituitary development remain unclear. In this study, we hypothesized that glycoprotein hormone subunit A2 (GPHA2), a corneal stem cell factor and ligand for the thyroid stimulating hormone receptor (TSHR), is downstream of NOTCH2 signaling. We found Gpha2 is expressed in quiescent pituitary stem cells by RNAscope in situ hybridization and scRNA seq. In Notch2 conditional knockout pituitaries, Gpha2 mRNA is reduced compared with control littermates. We then investigated the possible functions of GPHA2. Pituitaries treated with a GPHA2 peptide do not have a change in proliferation. However, in dissociated adult pituitary cells, GPHA2 increased pCREB expression and this induction was reversed by co-treatment with a TSHR inhibitor. These data suggest GPHA2 is a NOTCH2 related stem cell factor that activates TSHR signaling, potentially impacting pituitary development.

Crosstalk between aryl hydrocarbon receptor and Wnt/β-catenin signaling pathway: Possible culprit of di (2-ethylhexyl) phthalate-mediated cardiotoxicity in zebrafish larvae

Typical plasticizer di (2-ethylhexyl) phthalate (DEHP) has been demonstrated to induce cardiotoxicity in zebrafish, but the potential molecular mechanisms involved have not been fully elucidated. Aryl hydrocarbon receptor (AhR), an essential protein for inducing developmental abnormalities, has been demonstrated to be activated by DEHP in other species, but whether the AhR signaling pathway also contributes to DEHP-mediated cardiac developmental toxicity in zebrafish remains unclear. Firstly, molecular docking simulations initially confirmed the possibility that DEHP has AhR agonistic activity. To further confirm this conjecture, this work analyzed the changes of cardiac-related indexes in zebrafish stressed by DEHP at individual, protein, and gene levels. The results showed that DEHP mediated cardiac phenotypic developmental defects, increased CYP1A1 activity, and oxidative stress as well as significant changes in the expression levels of key proteins and genes of AhR, Wnt/β-catenin, and Nrf2-Keap1 signaling pathways. Notably, the addition of AhR inhibitors effectively alleviated the above negative effects, indicating that the AhR signaling pathway and its crosstalk with the Wnt/β-catenin signaling pathway is an essential pathway for DEHP-mediated cardiac developmental toxicity. Overall, this work enriches the molecular mechanism of DEHP-mediated cardiac developmental defects in zebrafish and provides a reliable biomarker for future environmental risk assessment of DEHP.

Organoid models of the pituitary gland in health and disease

The pituitary gland represents the hub of our endocrine system. Its cells produce specific hormones that direct multiple vital physiological processes such as body growth, fertility, and stress. The gland also contains a population of stem cells which are still enigmatic in phenotype and function. Appropriate research models are needed to advance our knowledge on pituitary (stem cell) biology. Over the last decade, 3D organoid models have been established, either derived from the pituitary stem cells or from pluripotent stem cells, covering both healthy and diseased conditions. Here, we summarize the state-of-the-art of pituitary-allied organoid models and discuss applications of these powerful in vitro research and translational tools to study pituitary development, biology, and disease.

A Common Variant in the CDK8 Gene Is Associated with Sporadic Pituitary Adenomas in the Portuguese Population: A Case-Control Study

The majority of pituitary adenomas occur in a sporadic context, and in the absence of known genetic predisposition. Three common variants at the NEBL (rs2359536), PCDH15 (rs10763170) and CDK8 (rs17083838) loci were previously associated with sporadic pituitary adenomas in the Han Chinese population, but these findings have not yet been replicated in any other population. The aim of this case-control study was to assess if these variants are associated with susceptibility to sporadic pituitary adenomas in the Portuguese population. Genotype and allele frequencies were determined in 570 cases and in 546 controls. The CDK8 rs17083838 minor allele (A allele) was significantly associated with sporadic pituitary adenomas, under an additive (odds ratio (OR) 1.73, 95% confidence interval (CI) 1.19–2.50, p = 0.004) and dominant (OR 1.82, 95% CI 1.24–2.68, p = 0.002) inheritance model. The NEBL rs2359536 and PCDH15 rs10763170 variants were not associated with the overall risk for the disease, although a borderline significant association was observed between the PCDH15 rs10763170 minor allele (T allele) and somatotrophinomas (dominant model, OR 1.55, 95% CI 1.02–2.35, p = 0.035). These findings suggest that the CDK8 rs17083838 variant, and possibly the PCDH15 rs10763170 variant, may increase susceptibility to sporadic pituitary adenomas in the Portuguese population.

Phosphorylation of β-catenin at Serine552 correlates with invasion and recurrence of non-functioning pituitary neuroendocrine tumours

Non-functioning pituitary tumours (NF-PitNETs) are common intracranial benign neoplasms that can exhibit aggressive behaviour by invading neighbouring structures and, in some cases, have multiple recurrences. Despite resulting in severe co-morbidities, no predictive biomarkers of recurrence have been identified for NF-PitNETs. In this study we have used high-throughput mass spectrometry-based analysis to examine the phosphorylation pattern of different subsets of NF-PitNETs. Based on histopathological, radiological, surgical and clinical features, we have grouped NF-PitNETs into non-invasive, invasive, and recurrent disease groups. Tumour recurrence was determined based on regular clinical and radiological data of patients for a mean follow-up of 10 years (SD ± 5.4 years). Phosphoproteomic analyses identified a unique phosphopeptide enrichment pattern which correlates with disease recurrence. Candidate phosphorylated proteins were validated in a large cohort of NF-PitNET patients by western blot and immunohistochemistry. We identified a cluster of 22 phosphopeptides upregulated in recurrent NF-PitNETs compared to non-invasive and invasive subgroups. We reveal significant phosphorylation of the β-catenin at Ser552 in recurrent and invasive NF-PitNETs, compared to non-invasive/non-recurrent NF-PitNET subgroup. Moreover, β-catenin pSer552 correlates with the recurrence free survival among 200 patients with NF-PitNET. Together, our results suggest that the phosphorylation status of β-catenin at Ser552 could act as potential biomarker of tumour recurrence in NF-PitNETs.

Pituitary Apoplexy: Risk Factors and Underlying Molecular Mechanisms

Pituitary apoplexy is a rare syndrome, graded from asymptomatic subclinical apoplexy to a life-threatening condition due to pituitary ischemia or haemorrhage of an enlarged pituitary gland. The risk factors and the molecular underlying mechanisms are yet to be elucidated. We provide an overview of the general concepts, the potential factors associated with pituitary adenoma susceptibility for apoplectic events and the molecular mechanisms that could be involved such as HIF-1α/VEGF pathways and metalloproteinases activation, among others. The knowledge of the molecular mechanisms that could participate in the pathogenesis of pituitary apoplexy is crucial to advancement in the identification of future diagnostic tools and therapeutic targets in this rare but sometimes fatal condition.

Collision of Craniopharyngioma and Pituitary Adenoma: Comprehensive Review of an Extremely Rare Sellar Condition

OBJECTIVE

The collision of pituitary adenoma and craniopharyngioma is extremely rare and thus there remains a paucity of data.

METHODS

We described a patient from our institution. We also performed a systematic review and subsequent quantitative synthesis of the literature (n = 21) and our institutional case to yield an integrated cohort, and a descriptive analysis was carried out.

RESULTS

Twenty-two patients (15 males and 7 females) were included in the integrated cohort. The median age was 47.0 years (range, 8-75 years). The tumor subtypes were 5 somatotropic, 5 lactotropic, 4 nonfunctioning, 3 gonadotropic, 2 corticotropic, 1 plurihormonal, and 1 silent subtype 3 for pituitary adenomas, and 19 adamantinomatous, 2 papillary, and 1 unknown subtype for craniopharyngiomas. Three different radiographic patterns were observed: solid mass with cystic component (n = 5), coexistence of two distinct solid components (n = 3), and a mixed-intensity solid mass (n = 5). The first 2 were consistent with histologically separate collision, whereas the third was consistent with histologically admixed collision. Among 19 patients in whom the postoperative course was recorded, a secondary intervention was required in 14 (73.7%) because of tumor progression or residual. The recurrence rate after gross total resection was 33.3%. Postoperative hormone replacement was required in 33.3%. The 10-year cumulative overall survival was 73.1%.

CONCLUSIONS

Most craniopharyngiomas were adamantinomatous. There are 2 types of collisions: separated and admixed. Tumor control, overall survival, and endocrinologic remission are more challenging to achieve than for solitary tumors, but gross total resection of both tumors is important for satisfactory tumor control.

Multiomics-Based Signaling Pathway Network Alterations in Human Non-functional Pituitary Adenomas

Non-functional pituitary adenoma (NFPA) seriously affects hypothanamus-pituitary-target organ axis system, with a series of molecule alterations in the multiple levels of genome, transcriptome, proteome, and post-translational modifications, and those molecules mutually interact in a molecular-network system. Meta analysis coupled with IPA pathway-network program was used to comprehensively analyze nine sets of documented NFPA omics data, including NFPA quantitative transcriptomics data [280 differentially expressed genes (DEGs)], NFPA quantitative proteomics data [50 differentially expressed proteins (DEPs)], NFPA mapping protein data (218 proteins), NFPA mapping protein nitration data (9 nitroproteins and 3 non-nitrated proteins), invasive NFPA quantitative transriptomics data (346 DEGs), invasive NFPA quantitative proteomics data (57 DEPs), control mapping protein data (1469 proteins), control mapping protein nitration data (8 nitroproteins), and control mapping phosphorylation data (28 phosphoproteins). A total of 62 molecular-networks with 861 hub-molecules and 519 canonical-pathways including 54 cancer-related canonical pathways were revealed. A total of 42 hub-molecule panels and 9 canonical-pathway panels were identified to significantly associate with tumorigenesis. Four important molecular-network systems, including PI3K/AKT, mTOR, Wnt, and ERK/MAPK pathway-systems, were confirmed in NFPAs by PTMScan experiments with altered expression-patterns and phosphorylations. Nineteen high-frequency hub-molecules were also validated in NFPAs with PTMScan experiment with at least 2.5-fold changes in expression or phosphorylation, including ERK, ERK1/2, Jnk, MAPK, Mek, p38 MAPK, AKT, PI3K complex, p85, PKC, FAK, Rac, Shc, HSP90, NFκB Complex, histone H3, AP1, calmodulin, and PLC. Furthermore, mTOR and Wnt pathway-systems were confirmed in NFPAs by immunoaffinity Western blot analysis, with significantly decreased expression of PRAS40 and increased phosphorylation levels of p-PRAS40 (Thr246) in mTOR pathway in NFPAs compared to controls, and with the decreased protein expressions of GSK-3β and GSK-3β, significantly increased phosphorylation levels of p-GSK3α (Ser21) and p-GSK3β (Ser9), and increased expression level of β-catenin in Wnt pathway in NFPAs compared to controls. Those findings provided a comphrensive and large-scale pathway network data for NFPAs, and offer the scientific evidence for insights into the accurate molecular mechanisms of NFPA and discovery of the effective biomarkers for diagnosis, prognosis, and determination of therapeutic targets.

Long Non-Coding RNA Plasmacytoma Variant Translocation 1 (PVT1) Enhances Proliferation, Migration, and Epithelial-Mesenchymal Transition (EMT) of Pituitary Adenoma Cells by Activating β-Catenin, c-Myc, and Cyclin D1 Expression

BACKGROUND As a kind of benign tumor, pituitary adenomas have attracted increasing attention from researchers. The plasmacytoma variant translocation 1 (PVT1) is a molecule in the lncRNA family protein that has been proven to play critical roles in many cancers; however, no study has explored the special biological roles of PVT1 in pituitary adenoma. MATERIAL AND METHODS The qRT-PCR assay was conducted to evaluate PVT1 expressions in various cell lines and tissues. Loss of function assays were carried out to detect the influence of silenced PVT1 on the proliferation, migration, and epithelial-mesenchymal transition (EMT) of pituitary adenoma cells. Western blotting was used to identify correlation between ß-catenin and PVT1. RESULTS The PVT1 expressions were significantly enhanced in tissues of pituitary adenoma and cancer cells. Cell migration and proliferation were inhibited when the PVT1 gene was knocked down. Knockdown of PVT1 repressed the migration and EMT of pituitary adenoma cells. The PVT1 downregulation obviously blocked Wnt/ß-catenin signaling pathway activity. PVT1 aggravated progression of pituitary adenoma through initiating the Wnt/ß-catenin signaling pathway. CONCLUSIONS PVT1 exerts an oncogenic role through activating Wnt/ß-catenin signaling in pituitary adenoma cells. The present results may provide a potential therapeutic target or approach for treating pituitary adenomas.

The Pituitary Transcriptional Response Related to Feed Conversion in Pigs

Over the decades, pig breeding objectives have focused on improving the meat content in the carcass without taking into consideration the more effective fattening indicators that affect feed conversion. At present, pig growth traits associated particularly with animal feeding have become crucial due to their economic significance. This is especially evident in countries where pigs are maintained on large farms. The present study indicates that pituitary differentially expressed genes (DEGs) are activated in response to variable feed conversion (FC) in pigs. The experiment included two native Polish breeds: Puławska and Złotnicka White (ZW). The whole pituitary transcriptome was sequenced using next-generation sequencing (NGS) technology. The RNA-seq method identified over 500 and 300 DEGs in the pituitaries of the ZW and the Puławska pig populations, respectively, that were associated with hormonal regulation, notch signaling, and Wnt pathways. Lower FC in the ZW pigs favoured increased fat content in the body and significantly higher prolactin expression. The obtained results indicate that low FC values in pigs are related to slower growth or increased fat content, which suggests various pituitary responses. Therefore, the identified candidate genes were not directly associated with feed conversion values but with other factors. However, the present study delivers new insights into pituitary regulation in pigs.

Impact of SLC20A1 on the Wnt/β‑catenin signaling pathway in somatotroph adenomas

Studies have revealed that genetic and functional aberrations of oncogenes, tumor‑suppressor genes, signaling pathways and receptors are among the most prominent events in pituitary tumorigenesis, and a potent biomarker would be helpful for early diagnosis, subsequent treatment and disease control. The present study investigated the expression signatures of solute carrier family 20 member 1, also known as phosphate transporter 1 (SLC20A1) and the Wnt/β‑catenin signaling pathway in 52 patients with somatotroph adenomas. According to immunohistochemistry analysis, the H‑score of SLC20A1 was 222.6±15.2 in invasive tumor samples and 144.5±30.4 in non‑invasive tumor samples (P<0.01), while the H‑scores of β‑catenin were 210.1±21.4 and 134.9±32.7, respectively (P<0.05). The H‑scores of Wnt inhibitory factor 1 (Wif1) exhibited the opposite trend, with scores of 134.5±22.7 and 253.6±14.8, respectively (P<0.01). The H‑scores of SLC20A1 were negatively associated with those of Wif1 in somatotroph adenomas (correlation coefficient r=‑0.367). The mean progression‑free survival in the low SLC20A1 group was longer than that in the group with high SLC20A1 H‑scores (P=0.024). Reverse transcription‑quantitative PCR (RT‑qPCR) and western blotting confirmed the interference efficiency of the segments short hairpin (Sh)‑B‑SLC20A1 and Sh‑C‑SLC20A1. Cell proliferation experiments revealed that the cell viability of the Sh‑B‑SLC20A1 group was 76.3±4.5, 65.7±3.7 and 53.1±3.2% of that of control GH3 cells after 24, 48 and 72 h of transfection, respectively, while the cell viability of the Sh‑C‑SLC20A1 group was 86.4±5.7, 75.6±4.4 and 67.5±3.8%, respectively (P<0.05). ELISA analysis demonstrated the growth hormone (GH) levels in the Sh‑B‑SLC20A1 and Sh‑C‑SLC20A1 groups to be 34.7±10.4 and 54.6±14.4%, respectively, of that of control GH3 cells (P<0.05). The transmembrane invasion assay revealed that knocking down SLC20A1 significantly suppressed cell invasion in the Sh‑B‑SLC20A1 and Sh‑C‑SLC20A1 groups. RT‑qPCR and western blotting demonstrated that Sh‑B‑SLC20A1 and Sh‑C‑SLC20A1 evidently increased the levels of Wif1 and secreted frizzled‑related protein 4. The present data suggested that SLC20A1 levels are positively associated with tumor size, invasive behavior and tumor recurrence in somatotroph adenomas. Furthermore, SLC20A1 may be associated with the activation of the Wnt/β‑catenin signaling pathway.

MicroRNA-543 promotes cell invasion and impedes apoptosis in pituitary adenoma via activating the Wnt/β-catenin pathway by negative regulation of Smad7

Pituitary adenomas (PA) are commonly occurring benign neoplasms. Identification of molecular pathway resulting in pituitary tumorigenesis remains challenges in endocrine oncology. The present study was conducted with aim of investigating the role of microRNA-543 (miR-543) in PA development. Up-regulated miR-543 and downregulated Smad7 were observed in PA tissues. Afterwards, the specific mechanism of miR-543 and Smad7 in PA were determined with the use of ectopic expression, depletion and reporter assay experiments. Smad7 was confirmed as a target gene of miR-543. HP75 cells treated with overexpressed miR-543 exhibited increased cell proliferation, migration and invasion, while decreased cell apoptosis as well as expression of Cleaved caspase-3 and Cleaved caspase-8 were observed. Suppression of miR-543 contributed to an opposite trend to the above findings. Based on the findings, the inhibition of miR-543 was found to play a tumor suppressive role in PA through the down-regulation of Wnt/β-catenin pathway by negatively regulating Smad7.

Pituitary adenomas, stem cells, and cancer stem cells: what's new?

PURPOSE

To clarify the existence of pituitary stem cells (SCs) both in the embryonic and the postnatal gland and the role for SCs in pituitary adenomas.

METHODS

This work, which does not address the pathogenesis of pituitary adenomas, reviews the latest research findings and discoveries on SCs in pituitary and cancer SCs (CSCs) in pituitary adenomas and discusses the involvement of the EMT.

RESULTS

Several groups using different approaches and techniques have demonstrated the existence of SCs and CSCs and as they are major players in pituitary adenoma onset.

CONCLUSIONS

As in other benign and malignant tumors, the hypothesis that CSCs play a pivotal role in pituitary adenoma onset has been confirmed as well as the existence of a link between the epithelial-to-mesenchymal transition (EMT) process and CSC formation in epithelial tumors.

Decreased expression of SFRP2 promotes development of the pituitary corticotroph adenoma by upregulating Wnt signaling

Cushing's disease is primarily caused by pituitary adrenocorticotropin‑secreting adenoma. However, its pathogenesis has remained obscure. In the present study, whole transcriptome analysis was performed by RNA sequencing (RNA‑Seq) and expression of secreted frizzled‑related protein 2 (SFRP2) was decreased in corticotroph tumors compared with normal pituitary glands. Furthermore, the RNA‑Seq results were validated and the expression of SFRP2 in tumor tissues was analyzed by comparing another cohort of 23 patients with Cushing's disease and 3 normal human pituitary samples using reverse transcription‑quantitative polymerase chain reaction, western blot and immunohistochemistry staining. Clinically, there was an association between lower SFRP2 expression and aggressive adenoma characteristics, including larger size and invasiveness. Conversely, SFRP2 overexpression reduced the ability of AtT20 cells to proliferate and migrate, and reduced production of the adrenocorticotrophic hormone in vitro. Mechanistically, overexpressed SFRP2 reduced the level of β‑catenin in the cytoplasm and nucleus, and decreased Wnt signaling activity in AtT20 cells. Therefore, SFRP2 appears to act as a tumor suppressor in Cushing's disease by regulating the activity of the Wnt signaling pathway.

Role of matrix Metalloproteinases in pituitary adenoma invasion

Though pituitary adenomas are benign tumors in most cases, a considerable fraction of PAs behave in a malignant-like manner and invade to the adjacent structures in sellar region, especially the cavernous sinuses. Cancer-cell invasion and metastasis remain a great challenge for physicians and surgeons in spite of emerging advances in drug therapy and surgical Treatment. matrix metalloproteinases, as a family of zinc-dependent endopeptidases, have long been known to be associated with tumor invasion and metastasis mainly via breaking down basement membrane in different tissues. Aberrant expression and activation of matrix metalloproteinases have been detected in invasive pituitary adenomas as in malignancy and correlated to tumor invasion. Therefore, matrix metalloproteinases are considered as promising biomarkers for predicting tumor behavior and even drug targets for novel therapeutic strategies. In this review, we give an overview of the expression, function, regulation and clinical prospects of matrix metalloproteinases, especially focusing on the biological network in which matrix metalloproteinases may be abnormally activated in promoting pituitary adenoma invasion.

Limitations of high throughput methods for miRNA expression profiles in non-functioning pituitary adenomas

Microarray, RT-qPCR based arrays and next-generation-sequencing (NGS) are available high-throughput methods for miRNA profiling (miRNome). Analytical and biological performance of these methods were tested in identification of biologically relevant miRNAs in non-functioning pituitary adenomas (NFPA). miRNome of 4 normal pituitary (NP) and 8 NFPA samples was determined by these platforms and expression of 21 individual miRNAs was measured on 30 (20 NFPA and 10 NP) independent samples. Complex bioinformatics was used. 132 and 137 miRNAs were detected by all three platforms in NP and NFPA, respectively, of which 25 were differentially expressed (fold change > 2). The strongest correlation was observed between microarray and TaqMan-array, while the data obtained by NGS were the most discordant despite of various bioinformatics settings. As a technical validation we measured the expression of 21 selected miRNAs by individual RT-qPCR and we were able to validate 35.1%, 76.2% and 71.4% of the miRNAs revealed by SOLiD, TLDA and microarray result, respectively. We performed biological validation using an extended number of samples (20 NFPAs and 8 NPs). Technical and biological validation showed high correlation (p < 0.001; R = 0.96). Pathway and network analysis revealed several common pathways but no pathway showed the same activation score. Using the 25 platform-independent miRNAs developmental pathways were the top functional categories relevant for NFPA genesis. The difference among high-throughput platforms is of great importance and selection of screening method can influence experimental results. Validation by another platform is essential in order to avoid or to minimalize the platform specific errors.

Pituitary stem cell regulation: who is pulling the strings?

The pituitary gland plays a pivotal role in the endocrine system, steering fundamental processes of growth, metabolism, reproduction and coping with stress. The adult pituitary contains resident stem cells, which are highly quiescent in homeostatic conditions. However, the cells show marked signs of activation during processes of increased cell remodeling in the gland, including maturation at neonatal age, adaptation to physiological demands, regeneration upon injury and growth of local tumors. Although functions of pituitary stem cells are slowly but gradually uncovered, their regulation largely remains virgin territory. Since postnatal stem cells in general reiterate embryonic developmental pathways, attention is first being given to regulatory networks involved in pituitary embryogenesis. Here, we give an overview of the current knowledge on the NOTCH, WNT, epithelial-mesenchymal transition, SHH and Hippo pathways in the pituitary stem/progenitor cell compartment during various (activation) conditions from embryonic over neonatal to adult age. Most information comes from expression analyses of molecular components belonging to these networks, whereas functional extrapolation is still very limited. From this overview, it emerges that the 'big five' embryonic pathways are indeed reiterated in the stem cells of the 'lazy' homeostatic postnatal pituitary, further magnified en route to activation in more energetic, physiological and pathological remodeling conditions. Increasing the knowledge on the molecular players that pull the regulatory strings of the pituitary stem cells will not only provide further fundamental insight in postnatal pituitary homeostasis and activation, but also clues toward the development of regenerative ideas for improving treatment of pituitary deficiency and tumors.

Aryl hydrocarbon receptor (AHR) is a potential tumour suppressor in pituitary adenomas

Pituitary adenomas (PA) represent the largest group of intracranial neoplasms and yet the molecular mechanisms driving this disease remain largely unknown. The aim of this study was to use a high-throughput screening method to identify molecular pathways that may be playing a significant and consistent role in PA. RNA profiling using microarrays on eight local PAs identified the aryl hydrocarbon receptor (AHR) signalling pathway as a key canonical pathway downregulated in all PA types. This was confirmed by real-time PCR in 31 tumours. The AHR has been shown to regulate cell cycle progression in various cell types; however, its role in pituitary tissue has never been investigated. In order to validate the role of AHR in PA behaviour, further functional studies were undertaken. Over-expression of AHR in GH3 cells revealed a tumour suppressor potential independent of exogenous ligand activation by benzo α-pyrene (BαP). Cell cycle analysis and quantitative PCR of cell cycle regulator genes revealed that both unstimulated and BαP-stimulated AHR reduced E2F-driven transcription and altered expression of cell cycle regulator genes, thus increasing the percentage of cells in G₀/G₁ phase and slowing the proliferation rate of GH3 cells. Co-immunoprecipitation confirmed the interaction between AHR and retinoblastoma (Rb1) protein supporting this as a functional mechanism for the observed reduction. Endogenous Ahr reduction using silencing RNA confirmed the tumour suppressive function of the Ahr. These data support a mechanistic pathway for the putative tumour suppressive role of AHR specifically in PA, possibly through its role as a cell cycle co-regulator, even in the absence of exogenous ligands.

Regulation of pituitary stem cells by epithelial to mesenchymal transition events and signaling pathways

The anterior pituitary gland is comprised of specialized cell-types that produce and secrete polypeptide hormones in response to hypothalamic input and feedback from target organs. These specialized cells arise from stem cells that express SOX2 and the pituitary transcription factor PROP1, which is necessary to establish the stem cell pool and promote an epithelial to mesenchymal-like transition, releasing progenitors from the niche. The adult anterior pituitary responds to physiological challenge by mobilizing the SOX2-expressing progenitor pool and producing additional hormone-producing cells. Knowledge of the role of signaling pathways and extracellular matrix components in these processes may lead to improvements in the efficiency of differentiation of embryonic stem cells or induced pluripotent stem cells into hormone producing cells in vitro. Advances in our basic understanding of pituitary stem cell regulation and differentiation may lead to improved diagnosis and treatment for patients with hypopituitarism.

Imaging of the Sella and Parasellar Region in the Pediatric Population

Masses in the sella and parasellar region comprise about 10% of all pediatric brain tumors but type and frequency differs from those in adults. Imaging is critical for diagnosis and characterization of these lesions. By assessing the site of origin, signal and contrast enhancement characteristics, and the presence or absence of characteristic patterns, differential diagnosis can narrow the possibilities. The clinical presentation is often characteristic for lesion type and should be considered. This article summarizes the characteristic imaging features of the most frequent pediatric tumors and tumor-mimicking lesions in children in this region.

The Stem Cell Connection of Pituitary Tumors

Tumors in the pituitary gland are typically benign but cause serious morbidity due to compression of neighboring structures and hormonal disruptions. Overall, therapy efficiency remains suboptimal with negative impact on health and comfort of life, including considerable risk of therapy resistance and tumor recurrence. To date, little is known on the pathogenesis of pituitary tumors. Stem cells may represent important forces in this process. The pituitary tumors may contain a driving tumor stem cell population while the resident tissue stem cells may be directly or indirectly linked to tumor development and growth. Here, we will briefly summarize recent studies that afforded a glance behind the scenes of this stem cell connection. A better knowledge of the mechanisms underlying pituitary tumorigenesis is essential to identify more efficacious treatment modalities and improve clinical management.

High FABP5 Versus CRABPII Expression Ratio in Recurrent Craniopharyngiomas: Implications for Future Treatment

BACKGROUND AND OBJECTIVE

Recurrence is a major problem in craniopharyngioma (CP) management. Recent study shows that high FABP5/CRABPII may be related to tumor growth and that all-trans retinoic acid (ATRA) may suppress primary CP growth. We studied the expression profile of FABP5 and CRABPII in recurrent CP tissue and the effect of ATRA on recurrent CP cells.

METHODS

Fifty cases of patients with CP were enrolled in the retrospective study. Among them, 15 were recurrent. Fresh specimens were collected for immunohistochemistry, reverse transcription polymerase chain reaction, and western blotting analysis of FABP5 and CRABPII. Fresh specimens from 6 primary and recurrent CPs were collected and subjected to cell culture using an explants method. ATRA at various concentrations was applied to recurrent CP cell culture, and cell growth was recorded and analyzed.

RESULTS

Immunohistochemistry, reverse transcription polymerase chain reaction, and western blot study showed that FABP5 was expressed significantly higher in recurrent tumors, whereas CRABPII was expressed significantly higher in primary tumors. The FABP5/CRABPII ratio was significantly higher in recurrent rather than primary tumors. Recurrent CP cells grew faster than primary cells, and ATRA induced cellular apoptosis and inhibited CP cell growth in a dose-dependent manner.

CONCLUSIONS

A high expression ratio between FABP5 and CRABPII may be related to CP tumor recurrence and ATRA could be a potential therapeutic agent for CP chemotherapy.

Low expression of secreted frizzled-related protein 2 and nuclear accumulation of β-catenin in aggressive nonfunctioning pituitary adenoma

The identification of a specific molecular marker for aggressiveness of nonfunctioning pituitary adenomas (NFPAs) is urgently required in order to guide the clinical diagnosis and treatment of NFPAs. In the present study, low expression of secreted frizzled-related protein 2 (sFRP2) in NFPAs was demonstrated by reverse transcription-quantitative polymerase chain reaction, western blot and immunohistochemical analyses. The results confirmed an abnormal accumulation of free β-catenin in the nuclei of NFPAs, which is the core step for the activation of the Wnt canonical signaling pathway. Furthermore, cyclin D1 and c-Myc, the downstream proteins of the Wnt canonical signaling pathway, were overexpressed in aggressive NFPAs. These findings demonstrated the activation of the Wnt canonical signaling pathway in aggressive NFPAs. In addition, sFRP2 expression was observed to be inversely correlated to the aggressiveness of NFPAs. Therefore, sFRP2 may act as a tumor suppressor through modulation of the cellular cytosolic pool of β-catenin in NFPAs. Furthermore, the expression of sFRP2 may serve as a biomarker for NFPAs aggressiveness and prognosis.

Wnt signaling pathway in cardiac fibrosis: New insights and directions

OBJECTIVE

Wnt signaling pathway significantly participates in cardiac fibrosis and CFs activation. Therefore, we reviewed current evidence on the new perspectives and biological association between Wnt signaling pathway and cardiac fibrosis.

DESIGN AND METHODS

A PubMed database search was performed for studies of Wnt signaling pathway in cardiac fibrosis and CFs activation.

RESULTS

Numerous studies have shown that the Wnt signaling pathway significantly participates in cardiac fibrosis pathogenesis. The aim of this review is to describe the present knowledge about the Wnt signaling pathway significantly participating in cardiac fibrosis and CFs activation, and look ahead on new perspectives of Wnt signaling pathway research. Moreover, we will discuss the different insights that interact with the Wnt signaling pathway-regulated cardiac fibrosis. The Wnt proteins are glycoproteins that bind to the Fz receptors on the cell surface, which lead to several important biological functions, such as cell differentiation and proliferation. There are several signals among the characterized pathways of cardiac fibrosis, including Wnt/β-catenin signaling. In this review, new insight into the Wnt signaling pathway in cardiac fibrosis pathogenesis is discussed, with special emphasis on Wnt/β-catenin.

CONCLUSION

It seems reasonable to suggest the potential targets of Wnt signaling pathway and it can be developed as a therapeutic target for cardiac fibrosis.

Common variants at 10p12.31, 10q21.1 and 13q12.13 are associated with sporadic pituitary adenoma

Pituitary adenoma is one of the most common intracranial neoplasms, and its genetic basis remains largely unknown. To identify genetic susceptibility loci for sporadic pituitary adenoma, we performed a three-stage genome-wide association study (GWAS) in the Han Chinese population. We first analyzed genome-wide SNP data in 771 pituitary adenoma cases and 2,788 controls and then carried forward the promising variants for replication in another 2 independent sets (2,542 cases and 3,620 controls in total). We identified three new susceptibility loci below the genome-wide significance threshold (P < 5 × 10(-8)) in the combined analyses: 10p12.31 (rs2359536, P(meta) = 2.25 × 10(-10) and rs10828088, P(meta) = 6.27 × 10(-10)), 10q21.1 (rs10763170, P(meta) = 6.88 × 10(-10)) and 13q12.13 (rs17083838, P(meta) = 1.89 × 10(-8)). This study is the first GWAS to our knowledge on sporadic pituitary adenoma, and our results provide insight into the genetic basis of this disease.

A pilot genome-scale profiling of DNA methylation in sporadic pituitary macroadenomas: association with tumor invasion and histopathological subtype

Pituitary adenomas (PAs) are neoplasms that may cause a variety of neurological and endocrine effects. Although known causal contributors include heredity, hormonal influence and somatic mutations, the pathophysiologic mechanisms driving tumorigenesis and invasion of sporadic PAs remain unknown. We hypothesized that alterations in DNA methylation are associated with PA invasion and histopathology subtype, and that genome-scale methylation analysis may complement current classification methods for sporadic PAs. Twenty-four surgically-resected sporadic PAs with varying histopathological subtypes were assigned dichotomized Knosp invasion scores and examined using genome-wide DNA methylation profiling and RNA sequencing. PA samples clustered into subgroups according to functional status. Compared with hormonally-active PAs, nonfunctional PAs exhibited global DNA hypermethylation (mean beta-value 0.47 versus 0.42, P = 0.005); the most significant site of differential DNA methylation was within the promoter region of the potassium voltage-gated channel KCNAB2 (FDR = 5.11×10⁻¹⁰). Pathway analysis of promoter-associated CpGs showed that nonfunctional PAs are potentially associated with the ion-channel activity signal pathway. DNA hypermethylation tended to be negatively correlated with gene expression. DNA methylation analysis may be used to identify candidate genes involved in PA function and may potentially complement current standard immunostaining classification in sporadic PAs. DNA hypermethylation of KCNAB2 and downstream ion-channel activity signal pathways may contribute to the endocrine-inactive status of nonfunctional PAs.

Identifying placental epigenetic alterations in an intrauterine growth restriction (IUGR) rat model induced by gestational protein deficiency

Poor maternal nutrition during gestation can lead to intrauterine growth retardation (IUGR), a main cause of low birth weight associated with high neonatal morbidity and mortality. Such early uterine environmental exposures can impact the neonatal epigenome to render later-in-life disease susceptibility. We established in Wistar Han rats a mild IUGR model induced by gestational protein deficiency (i.e. 9% crude protein in low protein diet vs. 21% in control, from GD 0 to 21) to identify alterations in gene expression and methylation patterns in certain genes implicated in human IUGR or in placental development. We found differential gene expression of Wnt2 and Dlk1 between IUGR and control. Notably, Wnt2 exhibited significant decrease while Dlk1 increase in IUGR placentas, correlating to decrease in fetal and placental weight. Methylation patterns encompassing 30 CpGs in the Wnt2 promoter region revealed variability in both IUGR and control placentas, but a site-specific hypomethylation was evident in IUGR placentas. Our present findings further support a key role of maternal gestational nutrition in defining the neonatal epigenome.