Gene expression profiling identifies ESRP1 as a potential regulator of epithelial mesenchymal transition in somatotroph adenomas from a large cohort of patients with acromegaly

ACLY alternative splicing correlates with cancer phenotypes

ATP-citrate lyase (ACLY) links carbohydrate and lipid metabolism and provides nucleocytosolic acetyl-CoA necessary for protein acetylation. ACLY has two major splice isoforms: the full-length canonical "long" isoform and an uncharacterized "short" isoform in which exon 14 is spliced out. Exon 14 encodes 10 amino acids within a disordered region of the protein and includes at least 1 site that is dynamically phosphorylated. Both isoforms are expressed in healthy tissues to varying degrees. Analysis of human transcriptomic data revealed that the Percent Spliced In (PSI) of exon 14, i.e., the proportion of long isoform, is increased in several cancers and correlated with poorer overall survival in a pan-cancer analysis, though not in individual tumor types, which prompted us to explore potential biochemical and functional differences between ACLY isoforms. Here, we show that there are no discernible differences in enzymatic activity or stability between isoforms or phosphomutants of ACLY in vitro. Similarly, both isoforms and phosphomutants were able to rescue ACLY functions, including fatty acid synthesis and bulk histone acetylation, when re-expressed in Acly knockout cells. Deletion of Acly exon 14 in mice did not overtly impact development or metabolic physiology, nor did it attenuate tumor burden in a genetic model of intestinal cancer. Notably, expression of epithelial splicing regulatory protein 1 (ESRP1) is highly correlated with ACLY PSI. We report that ACLY splicing is regulated by ESRP1. In turn, both ESRP1 expression and ACLY PSI are correlated with specific immune signatures in tumors. Despite these intriguing patterns of ACLY splicing in healthy and cancer tissues, functional differences between the isoforms remain elusive.

Revisiting the usefulness of the short acute octreotide test to predict treatment outcomes in acromegaly

Introduction

We previously described that a short version of the acute octreotide test (sAOT) can predict the response to first-generation somatostatin receptor ligands (SRLs) in patients with acromegaly. We have prospectively reassessed the sAOT in patients from the ACROFAST study using current ultra-sensitive GH assays. We also studied the correlation of sAOT with tumor expression of E-cadherin and somatostatin receptor 2 (SSTR2) .

Methods

A total of 47 patients treated with SRLs for 6 months were evaluated with the sAOT at diagnosis and correlated with SRLs' response. Those patients whose IGF1 decreased to <3SDS from normal value were considered responders and those whose IGF1 was ≥3SDS, were considered non-responders. The 2 hours GH value (GH2h) after s.c. administration of 100 mcg of octreotide was used to define predictive cutoffs. E-cadherin and SSTR2 immunostaining in somatotropinoma tissue were investigated in 24/47 and 18/47 patients, respectively.

Results

In all, 30 patients were responders and 17 were non-responders. GH2h was 0.68 (0.25-1.98) ng/mL in responders vs 2.35 (1.59-9.37) ng/mL in non-responders (p<0.001). GH2h = 1.4ng/mL showed the highest ability to identify responders (accuracy of 81%, sensitivity of 73.3%, and specificity of 94.1%). GH2h = 4.3ng/mL was the best cutoff for non-response prediction (accuracy of 74%, sensitivity of 35.3%, and specificity of 96.7%). Patients with E-cadherin-positive tumors showed a lower GH2h than those with E-cadherin-negative tumors [0.9 (0.3-2.1) vs 3.3 (1.5-12.1) ng/mL; p<0.01], and patients with positive E-cadherin presented a higher score of SSTR2 (7.5 ± 4.2 vs 3.3 ± 2.1; p=0.01).

Conclusion

The sAOT is a good predictor tool for assessing response to SRLs and correlates with tumor E-cadherin and SSTR2 expression. Thus, it can be useful in clinical practice for therapeutic decision-making in patients with acromegaly.

Multiomics Approach to Acromegaly: Unveiling Translational Insights for Precision Medicine

The clinical characteristics and prognoses of acromegaly vary among patients. Assessment of current and novel predictors can lead to multilevel categorization of patients, allowing integration into new clinical guidelines and a reduction in the increased morbidity and mortality associated with acromegaly. Despite advances in the diagnosis and treatment of acromegaly, its pathophysiology remains unclear. Recent advancements in multiomics technologies, including genomics, transcriptomics, proteomics, metabolomics, and radiomics, have offered new opportunities to unravel the complex pathophysiology of acromegaly. This review comprehensively explores the emerging role of multiomics approaches in elucidating the molecular landscape of acromegaly. We discuss the potential implications of multiomics data integration in the development of novel diagnostic tools, identification of therapeutic targets, and the prospects of precision medicine in acromegaly management. By integrating diverse omics datasets, these approaches can provide valuable insights into disease mechanisms, facilitate the identification of diagnostic biomarkers, and identify potential therapeutic targets for precision medicine in the management of acromegaly.

Tumour microenvironment and pituitary tumour behaviour

The pituitary tumour microenvironment encompasses a spectrum of non-tumoural cells, such as immune, stromal or endothelial cells, as well as enzymes and signalling peptides like cytokines, chemokines and growth factors, which surround the tumour cells and may influence pituitary tumour behaviour and tumourigenic mechanisms. Recently, there has been intensive research activity in this field describing various pituitary tumour-infiltrating immune and stromal cell subpopulations, and immune- and microenvironment-related pathways. Key changes in oncological therapeutic avenues resulted in the recognition of pituitary as a target of adverse events for patients treated with immune checkpoint regulators. However, these phenomena can be turned into therapeutic advantage in severe cases of pituitary tumours. Therefore, unravelling the pituitary tumour microenvironment will allow a better understanding of the biology and behaviour of pituitary tumours and may provide further developments in terms of diagnosis and management of patients with aggressively growing or recurrent pituitary tumours.

Molecular characterization of epithelial-mesenchymal transition and medical treatment related-genes in non-functioning pituitary neuroendocrine tumors

INTRODUCTION

Different medical therapies have been developed for pituitary adenomas. However, Non-Functioning Pituitary Neuroendocrine Tumors (NF-PitNET) have shown little response to them. Furthermore, epithelial-mesenchymal transition (EMT) has been linked to resistance to medical treatment in a significant number of tumors, including pituitary adenomas.

METHODS

We aimed to evaluate the expression of EMT-related markers in 72 NF-PitNET and 16 non-tumoral pituitaries. To further explore the potential usefulness of medical treatment for NF-PitNET we assessed the expression of somatostatin receptors and dopamine-associated genes.

RESULTS

We found that SNAI1, SNAI2, Vimentin, KLK10, PEBP1, Ki-67 and SSTR2 were associated with invasive NF-PitNET. Furthermore, we found that the EMT phenomenon was more common in NF-PitNET than in GH-secreting pituitary tumors. Interestingly, PEBP1 was overexpressed in recurrent NF-PitNET, and could predict growth recurrence with 100% sensitivity but only 43% specificity. In parallel with previously reported studies, SSTR3 is highly expressed in our NF-PitNET cohort. However, SSTR3 expression is highly heterogeneous among the different histological variants of NF-PitNET with very low levels in silent corticotroph adenomas.

CONCLUSION

NF-PitNET showed an enhanced EMT phenomenon. SSTR3 targeting could be a good therapeutic candidate in NF-PitNET except for silent corticotroph adenomas, which express very low levels of this receptor. In addition, PEBP1 could be an informative biomarker of tumor regrowth, useful for predictive medicine in NF-PitNET.

The microenvironment of pituitary adenomas: biological, clinical and therapeutical implications

The microenvironment of pituitary adenomas (PAs) includes a range of non-tumoral cells, such as immune and stromal cells, as well as cell signaling molecules such as cytokines, chemokines and growth factors, which surround pituitary tumor cells and may modulate tumor initiation, progression, invasion, angiogenesis and other tumorigenic processes. The microenvironment of PAs has been actively investigated over the last years, with several immune and stromal cell populations, as well as different cytokines, chemokines and growth factors being recently characterized in PAs. Moreover, key microenvironment-related genes as well as immune-related molecules and pathways have been investigated, with immune check point regulators emerging as promising targets for immunotherapy. Understanding the microenvironment of PAs will contribute to a deeper knowledge of the complex biology of PAs, as well as will provide developments in terms of diagnosis, clinical management and ultimately treatment of patients with aggressive and/or refractory PAs.

Distribution of E- and N-cadherin in subgroups of non-functioning pituitary neuroendocrine tumours

PURPOSE

Clinically non-functioning pituitary neuroendocrine tumours (NF-PitNETs) present a varying degree of aggressiveness, and reliable prognostic markers are lacking. We aimed to characterise the distribution of E- and N-cadherin in corticotroph, PIT1 and null-cell NF-PitNETs, and link it to the course of the tumours.

METHODS

The distribution of E- and N-cadherin was investigated by immunohistochemistry in a retrospective cohort of 30 tumours of the less common NF-PitNETs (corticotroph (N = 18), PIT1 (N = 8) and null-cell PitNETs (N = 4)). Immunoreactive scores (IRS) were compared to previously presented cohorts of gonadotroph NF-PitNETs (N = 105) and corticotroph functioning PitNETs (N = 17).

RESULTS

We found a low IRS for the extra-cellular domain of E-cadherin (median 0 (IQR 0-0, N = 135)), a medium to high IRS for the intra-cellular domain of E-cadherin (median 6 (IQR 4-9)) and a high IRS for N-cadherin (median 12 (IQR 10.5-12)) throughout the cohort of NF-PitNETs. The corticotroph NF-PitNETs presented a higher IRS for both the extra- and intra-cellular domain of E-cadherin (median 0 (IQR 0-1) and median 9 (IQR 6-12), respectively) than the gonadotroph NF-PitNETs (p < 0.001 for both comparisons). Presence of nuclear E-cadherin was associated with a weaker staining for the intra-cellular domain of E-cadherin (median 4 (IQR 0.5-6) and median 9 (IQR 9-12), for tumours with and without nuclear E-cadherin, respectively), and with a lower rate of re-intervention (p = 0.03).

CONCLUSIONS

Considering our results and the benign course of NF-PitNETs, we suggest that a high N-cadherin and downregulation of membranous E-cadherin are not associated with a more aggressive tumour behaviour in these subgroups of NF-PitNETs.

Implications of Heterogeneity of Epithelial-Mesenchymal States in Acromegaly Therapeutic Pharmacologic Response

Acromegaly is caused by excess growth hormone (GH) produced by a pituitary tumor. First-generation somatostatin receptor ligands (SRLs) are the first-line treatment. Several studies have linked E-cadherin loss and epithelial-mesenchymal transition (EMT) with resistance to SRLs. Our aim was to study EMT and its relationship with SRLs resistance in GH-producing tumors. We analyzed the expression of EMT-related genes by RT-qPCR in 57 tumors. The postsurgical response to SRLs was categorized as complete response, partial response, or nonresponse if IGF-1 was normal, had decreased more than 30% without normalization, or neither of those, respectively. Most tumors showed a hybrid and variable EMT expression profile not specifically associated with SRL response instead of a defined epithelial or mesenchymal phenotype. However, high SNAI1 expression was related to invasive and SRL-nonresponsive tumors. RORC was overexpressed in tumors treated with SRLs before surgery, and this increased expression was more prominent in those cases that normalized postsurgical IGF-1 levels under SRL treatment. In conclusion, GH-producing tumors showed a heterogeneous expression pattern of EMT-related genes that would partly explain the heterogeneous response to SRLs. SNAI1 and RORC may be useful to predict response to SRLs and help medical treatment decision making.

Potential biomarkers and lncRNA-mRNA regulatory networks in invasive growth hormone-secreting pituitary adenomas

PURPOSE

Growth hormone-secreting pituitary adenomas (GH-PAs) are common subtypes of functional PAs. Invasive GH-PAs play a key role in restricting poor outcomes. The transcriptional changes in GH-PAs were evaluated.

METHODS

In this study, the transcriptome analysis of six different GH-PA samples was performed. The functional roles, co-regulatory network, and chromosome location of differentially expressed (DE) genes in invasive GH-PAs were explored.

RESULTS

Bioinformatic analysis revealed 101 DE mRNAs and 70 DE long non-coding RNAs (lncRNAs) between invasive and non-invasive GH-PAs. Functional enrichment analysis showed that epithelial cell differentiation and development pathways were suppressed in invasive GH-PAs, whereas the pathways of olfactory transduction, retinol metabolism, drug metabolism-cytochrome P450, and metabolism of xenobiotics by cytochrome P450 had an active trend. In the protein-protein interaction network, 11 main communities were characterized by cell- adhesion, -motility, and -cycle; transport process; phosphorus and hormone metabolic processes. The SGK1 gene was suggested to play a role in the invasiveness of GH-PAs. Furthermore, the up-regulated genes OR51B6, OR52E4, OR52E8, OR52E6, OR52N2, MAGEA6, MAGEC1, ST8SIA6-AS1, and the down-regulated genes GAD1-AS1 and SPINT1-AS1 were identified in the competing endogenous RNA network. The RT-qPCR results further supported the aberrant expression of those genes. Finally, the enrichment of DE genes in chromosome 11p15 and 12p13 regions were detected.

CONCLUSION

Our findings provide a new perspective for studies evaluating the underlying mechanism of invasive GH-PAs.

Cytokeratin 8/18-negative somatotroph pituitary neuroendocrine tumours (PitNETs, adenomas) show variable morphological features and do not represent a clinicopathologically distinct entity

AIMS

In somatotroph pituitary neuroendocrine tumours (adenomas), a pattern of cytokeratin (CK) 18 expression is used for tumour subclassification, with possible clinical implications. Rare somatotroph tumours do not express CK 18. We aimed to characterise this subset clinically and histologically.

METHODS AND RESULTS

Clinical and pathological data for the study were derived from a previously published data set of a cohort of 110 patients with acromegaly. Data included serum levels of insulin-like growth factor 1 (IGF1), growth hormone (GH), prolactin and thyroid-stimulating hormone (TSH), tumour diameter, tumour invasion defined by Knosp grade and immunohistochemical data concerning the expression of Ki67, p53, E-cadherin, somatostatin receptor (SSTR)1, SSTR2A, SSTR3, SSTR5 and D2 dopamine receptor. Additional immunohistochemical analysis (AE1/3, CK 8/18, vimentin, neurofilament light chain, internexin-α) was performed. CK 18 was negative in 10 of 110 (9.1%) tumours. One of these tumours was immunoreactive with CK 8/18 antibody, while the remainder expressed only internexin-α intermediate filament in patterns similar to CK 18 (perinuclear fibrous bodies). CK-negative tumours showed no significant differences with respect to biochemical, radiological or pathological features. They showed significantly higher expression of SSTR2A compared to the sparsely granulated subtype and significantly lower expression of E-cadherin compared to the non-sparsely granulated subtypes of tumours. The tumours showed divergent morphology and hormonal expression: two corresponded to densely granulated tumours and three showed co-expression of prolactin and morphology of either mammosomatotroph or somatotroph-lactotroph tumours. Four tumours showed morphology and immunoprofile compatible with plurihormonal Pit1-positive tumours.

CONCLUSIONS

CK-negative somatotroph tumours do not represent a distinct subtype of somatotroph tumours, and can be further subdivided according to their morphology and immunoprofile.

Molecular determinants of enhanced response to somatostatin receptor ligands after debulking in large GH-producing adenomas

OBJECTIVE

Large somatotrophic adenomas depict poor response to somatostatin receptor ligands (SRLs). Debulking has shown to enhance SRLs effect in some but not all cases and tumour volume reduction has been proposed as the main predictor of response. No biological studies have been performed so far in this matter. We aimed to identify molecular markers of response to SRLs after surgical debulking in GH-secreting adenomas.

DESIGN

We performed a multicenter retrospective study.

PATIENTS

24 patients bearing large GH-producing tumours.

MEASUREMENTS

Clinical data and SRLs response both before and after surgical debulking were collected, and 21 molecular biomarkers of SRLs response were studied in tumour samples by gene expression.

RESULTS

From the 21 molecular markers studied, only two of them predicted enhanced SRLs response after surgery. Tumours with improved response to SRLs after surgical debulking showed lower levels of Ki-67 (MKI67, FC = 0.17 and P = .008) and higher levels of RAR-related orphan receptor C (RORC) (FC = 3.1 and P ˂ .001). When a cut-off of no detectable expression was used for Ki-67, the model provided a sensitivity of 100% and a specificity of 52.6% with an area under the curve of 65.8%. Using a cut-off of 2 units of relative expression of RORC, the prediction model showed 100% of sensitivity and specificity.

CONCLUSIONS

High levels of RORC and low levels of Ki-67 identify improved SRLs response after surgical debulking in large somatotropic adenomas. To determine their expression would facilitate medical treatment decision-making after surgery.

Large Scale Molecular Studies of Pituitary Neuroendocrine Tumors: Novel Markers, Mechanisms and Translational Perspectives

Simple Summary

Pituitary neuroendocrine tumors are non-cancerous tumors of the pituitary gland, that may overproduce hormones leading to serious health conditions or due to tumor size cause chronic headache, vertigo or visual impairment. In recent years pituitary neuroendocrine tumors are studied with the latest molecular biology methods that simultaneously investigate a large number of factors to understand the mechanisms of how these tumors develop and how they could be diagnosed or treated. In this review article, we have studied literature reports, compiled information and described molecular factors that could affect the development and clinical characteristics of pituitary neuroendocrine tumors, discovered factors that overlap between several studies using large scale molecular analysis and interpreted the potential involvement of these factors in pituitary tumor development. Overall, this study provides a valuable resource for understanding the biology of pituitary neuroendocrine tumors.

Abstract

Pituitary neuroendocrine tumors (PitNETs) are non-metastatic neoplasms of the pituitary, which overproduce hormones leading to systemic disorders, or tumor mass effects causing headaches, vertigo or visual impairment. Recently, PitNETs have been investigated in large scale (exome and genome) molecular analyses (transcriptome microarrays and sequencing), to uncover novel markers. We performed a literature analysis on these studies to summarize the research data and extrapolate overlapping gene candidates, biomarkers, and molecular mechanisms. We observed a tendency in samples with driver mutations (GNAS, USP8) to have a smaller overall mutational rate, suggesting driver-promoted tumorigenesis, potentially changing transcriptome profiles in tumors. However, direct links from drivers to signaling pathways altered in PitNETs (Notch, Wnt, TGF-β, and cell cycle regulators) require further investigation. Modern technologies have also identified circulating nucleic acids, and pinpointed these as novel PitNET markers, i.e., miR-143-3p, miR-16-5p, miR-145-5p, and let-7g-5p, therefore these molecules must be investigated in the future translational studies. Overall, large-scale molecular studies have provided key insight into the molecular mechanisms behind PitNET pathogenesis, highlighting previously reported molecular markers, bringing new candidates into the research field, and reapplying traditional perspectives to newly discovered molecular mechanisms.

Medication for Acromegaly Reduces Expression of MUC16, MACC1 and GRHL2 in Pituitary Neuroendocrine Tumour Tissue

Acromegaly is a disease mainly caused by pituitary neuroendocrine tumor (PitNET) overproducing growth hormone. First-line medication for this condition is the use of somatostatin analogs (SSAs), that decrease tumor mass and induce antiproliferative effects on PitNET cells. Dopamine agonists (DAs) can also be used if SSA treatment is not effective. This study aimed to determine differences in transcriptome signatures induced by SSA/DA therapy in PitNET tissue. We selected tumor tissue from twelve patients with somatotropinomas, with half of the patients receiving SSA/DA treatment before surgery and the other half treatment naive. Transcriptome sequencing was then carried out to identify differentially expressed genes (DEGs) and their protein–protein interactions, using pathway analyses. We found 34 upregulated and six downregulated DEGs in patients with SSA/DA treatment. Three tumor development promoting factors MUC16, MACC1, and GRHL2, were significantly downregulated in therapy administered PitNET tissue; this finding was supported by functional studies in GH3 cells. Protein–protein interactions and pathway analyses revealed extracellular matrix involvement in the antiproliferative effects of this type of the drug treatment, with pronounced alterations in collagen regulation. Here, we have demonstrated that somatotropinomas can be distinguished based on their transcriptional profiles following SSA/DA therapy, and SSA/DA treatment does indeed cause changes in gene expression. Treatment with SSA/DA significantly downregulated several factors involved in tumorigenesis, including MUC16, MACC1, and GRHL2. Genes that were upregulated, however, did not have a direct influence on antiproliferative function in the PitNET cells. These findings suggested that SSA/DA treatment acted in a tumor suppressive manner and furthermore, collagen related interactions and pathways were enriched, implicating extracellular matrix involvement in this anti-tumor effect of drug treatment.

Pasireotide in the Personalized Treatment of Acromegaly

The delay in controlling the disease in patients who do not respond to first-line treatment with first generation somatostatin receptor ligands (first-generation SRLs) can be quantified in years, as every modification in the medical therapy requires some months to be fully evaluated. Considering this, acromegaly treatment should benefit from personalized medicine therapeutic approach by using biomarkers identifying drug response. Pasireotide has been positioned mostly as a compound to be used in first-generation SRLs resistant patients and after surgical failure, but sufficient data are now available to indicate it is a first line therapy for patients with certain characteristics. Pasireotide has been proved to be useful in patients in which hyperintensity T2 MRI signal is shown and in those depicting low SST2 and high expression of SST5, low or mutated AIP condition and sparsely granulated immunohistochemical pattern. This combination of clinical and pathological characteristics is unique for certain patients and seems to cluster in the same cases, strongly suggesting an etiopathogenic link. Thus, in this paper we propose to include this clinico-pathologic phenotype in the therapeutic algorithm, which would allow us to use as first line medical treatment those compounds with the highest potential for achieving the fastest control of GH hypersecretion as well as a positive effect upon tumor shrinkage, therefore accelerating the implementation of precision medicine for acromegaly. Moreover, we suggest the development, validation and clinical use of a pasireotide acute test, able to identify patients responsive to pasireotide LAR as the acute octreotide test is able to do for SRLs.

Epithelial-Mesenchymal Transition in the Resistance to Somatostatin Receptor Ligands in Acromegaly

Epithelial-mesenchymal transition (EMT) is a dynamic process by which epithelial cells loss their phenotype and acquire mesenchymal traits, including increased migratory and invasive capacities. EMT is involved in physiological processes, such as embryogenesis and wound healing, and in pathological processes such as cancer, playing a pivotal role in tumor progression and metastasis. Pituitary tumors, although typically benign, can be locally invasive. Different studies have shown the association of EMT with increased tumor size and invasion in pituitary tumors, and in particular with a poor response to Somatostatin Receptor Ligands (SRLs) treatment in GH-producing pituitary tumors, the main cause of acromegaly. This review will summarize the current knowledge regarding EMT and SRLs resistance in acromegaly and, based on this relation, will suggest new biomarkers and possible therapies to SRLs resistant tumors.

Distinct Pattern of Endoplasmic Reticulum Protein Processing and Extracellular Matrix Proteins in Functioning and Silent Corticotroph Pituitary Adenomas

Simple Summary

Corticotroph pituitary adenomas present a spectrum of functionality regarding hormonal production, ranging from functioning to silent tumors. Moreover, they show different invasiveness and recurrent behavior profiles, the silent being considered an aggressive type of adenomas. Through analyses of global transcriptome and proteome, we show that both groups expressed genes and protein related to protein synthesis and vesicular transport, and present a distinct pattern of collagen/ extracellular matrix proteins. Endoplasmic reticulum protein processing is a key factor for hormone production in functioning corticotroph adenomas. Furthermore, a distinct cell adhesion profile in silent corticotroph adenomas may explain the aggressive behavior. Together, our findings shed light on the different repertoires of activated signaling pathways in corticotroph pituitary adenomas and may reveal new potential medical targets.

Abstract

Functioning (FCA) and silent corticotroph (SCA) pituitary adenomas act differently from a clinical perspective, despite both subtypes showing positive TBX19 (TPIT) and/or adrenocorticotropic hormone (ACTH) staining by immunohistochemistry. They are challenging to treat, the former due to functional ACTH production and consequently hypercortisolemia, and the latter due to invasive and recurrent behavior. Moreover, the molecular mechanisms behind their distinct behavior are not clear. We investigated global transcriptome and proteome changes in order to identify signaling pathways that can explain FCA and SCA differences (e.g., hormone production vs. aggressive growth). In the transcriptomic study, cluster analyses of differentially expressed genes revealed two distinct groups in accordance with clinical and histological classification. However, in the proteomic study, a greater degree of heterogeneity within the SCA group was found. Genes and proteins related to protein synthesis and vesicular transport were expressed by both adenoma groups, although different types and a distinct pattern of collagen/extracellular matrix proteins were presented by each group. Moreover, several genes related to endoplasmic reticulum protein processing were overexpressed in the FCA group. Together, our findings shed light on the different repertoires of activated signaling pathways in corticotroph adenomas, namely, the increased protein processing capacity of FCA and a specific pattern of adhesion molecules that may play a role in the aggressiveness of SCA.

FSH Levels Are Related to E-cadherin Expression and Subcellular Location in Nonfunctioning Pituitary Tumors

CONTEXT

Gonadotroph pituitary neuroendocrine tumors (PitNETs) can express follicle-stimulating hormone (FSH) and luteinizing hormone (LH) or be hormone negative, but they rarely secrete hormones. During tumor development, epithelial cells develop a mesenchymal phenotype. This process is characterized by decreased membranous E-cadherin and translocation of E-cadherin to the nucleus. Estrogen receptors (ERs) regulate both E-cadherin and FSH expression and secretion. Whether the hormone status of patients with gonadotroph PitNETs is regulated by epithelial-to-mesenchymal transition (EMT) and ERs is unknown.

OBJECTIVES

To study the effect of EMT on hormone expression in gonadotroph nonfunctioning (NF)-PitNETs.

DESIGN

Molecular and clinical analyses of 105 gonadotroph PitNETs. Immunohistochemical studies and real-time quantitative polymerase chain reaction were performed for FSH, LH, E-cadherin, and ERα. Further analyses included blood samples, clinical data, and radiological images.

SETTING

All patients were operated on in the same tertiary referral center.

RESULTS

NF-PitNET with high FSH expression had decreased immunohistochemical staining for membranous E-cadherin (P < .0001) and increased staining for nuclear E-cadherin (P < .0001). Furthermore, high FSH expression was associated with increased ERα staining (P = .0002) and ERα mRNA (P = .0039). Circulating levels of plasma-FSH (P-FSH) correlated with FSH staining in gonadotroph NF-PitNET (P = .0025). Tumor size and invasiveness was not related to FSH staining, E-cadherin, or ERα. LH expression was not associated with E-cadherin or ERα.

CONCLUSION

In gonadotroph PitNETs, FSH staining is related to E-cadherin, ERα expression, and circulating levels of P-FSH. There was no association between FSH staining and invasiveness. The clinical significance of these findings will be investigated in ongoing prospective studies.

The tumour microenvironment of pituitary neuroendocrine tumours

The tumour microenvironment (TME) includes a variety of non-neoplastic cells and non-cellular elements such as cytokines, growth factors and enzymes surrounding tumour cells. The TME emerged as a key modulator of tumour initiation, progression and invasion, with extensive data available in many cancers, but little is known in pituitary tumours. However, the understanding of the TME of pituitary tumours has advanced thanks to active research in this field over the last decade. Different immune and stromal cell subpopulations, and several cytokines, growth factors and matrix remodelling enzymes, have been characterised in pituitary tumours. Studying the TME in pituitary tumours may lead to a better understanding of tumourigenic mechanisms, identification of biomarkers useful to predict aggressive disease, and development of novel therapies. This review summarises the current knowledge on the different TME cellular/non-cellular elements in pituitary tumours and provides an overview of their role in tumourigenesis, biological behaviour and clinical outcomes.

Potential markers of disease behavior in acromegaly and gigantism

Introduction: Acromegaly and gigantism entail increased morbidity and mortality if left untreated, due to the systemic effects of chronic GH and IGF-1 excess. Guidelines for the diagnosis and treatment of patients with GH excess are well established; however, the presentation, clinical behavior and response to treatment greatly vary among patients. Numerous markers of disease behavior are routinely used in medical practice, but additional biomarkers have been recently identified as a result of basic and clinical research studies.Areas covered: This review focuses on genetic, molecular and genomic features of patients with GH excess that have recently been linked to disease progression and response to treatment. A PubMed search was conducted to identify markers of disease behavior in acromegaly and gigantism. Markers already considered as part of routine studies in clinical care guidelines were excluded. Literature search was expanded for each marker identified. Novel markers not included or only partially covered in previously published reviews on the subject were prioritized.Expert opinion: Recognizing the most relevant markers of disease behavior may help the medical team tailoring the strategies for approaching each case of acromegaly and gigantism. This customized plan should make the evaluation, treatment and follow up process more efficient, greatly improving the patients' outcomes.

Molecular determinants of the response to medical treatment of growth hormone secreting pituitary neuroendocrine tumors

Acromegaly is a chronic systemic disease mainly caused by a growth hormone (GH)-secreting pituitary neuroendocrine tumor (PitNETs), which is associated with many health complications and increased mortality when not adequately treated. Transsphenoidal surgery is considered the treatment of choice in GH-secreting PitNETs, but patients in whom surgery cannot be considered or with persistent disease after surgery require medical therapy. Treatment with available synthetic somatostatin analogues (SSAs) is considered the mainstay in the medical management of acromegaly which exert their beneficial effects through the binding to a family of G-protein coupled receptors encoded by 5 genes (SSTR1-5). However, although it has been demonstrated that the SST1-5 receptors are physically present in tumor cells, SSAs are in many cases ineffective (i.e. approximately 10-30% of patients with GH-secreting PitNET are unresponsive to SSAs), suggesting that other cellular/molecular determinants could be essential for the response to the pharmacological treatment in patients with GH-secreting PitNETs. Therefore, the scrutiny of these determinants might be used for the identification of subgroups of patients in whom an appropriate pharmacological treatment can be successfully employed (responders vs. non-responders). In this review, we will describe some of the existing, classical and novel, genetic and molecular determinants involved in the response of patients with GH-secreting PitNETs to the available therapeutic treatments, as well as new molecular/therapeutic approaches that could be potentially useful for the treatment of GH-secreting PitNETs.

Tumor microenvironment defines the invasive phenotype of AIP-mutation-positive pituitary tumors

The molecular mechanisms leading to aryl hydrocarbon receptor interacting protein (AIP) mutation-induced aggressive, young-onset growth hormone-secreting pituitary tumors are not fully understood. In this study, we have identified that AIP-mutation-positive tumors are infiltrated by a large number of macrophages compared to sporadic tumors. Tissue from pituitary-specific Aip-knockout (Aip^Flox/Flox;Hesx1^Cre/+) mice recapitulated this phenotype. Our human pituitary tumor transcriptome data revealed the "epithelial-to-mesenchymal transition (EMT) pathway" as one of the most significantly altered pathways in AIPpos tumors. Our in vitro data suggest that bone marrow-derived macrophage-conditioned media induces more prominent EMT-like phenotype and enhanced migratory and invasive properties in Aip-knockdown somatomammotroph cells compared to non-targeting controls. We identified that tumor-derived cytokine CCL5 is upregulated in AIP-mutation-positive human adenomas. Aip-knockdown GH3 cell-conditioned media increases macrophage migration, which is inhibited by the CCL5/CCR5 antagonist maraviroc. Our results suggest that a crosstalk between the tumor and its microenvironment plays a key role in the invasive nature of AIP-mutation-positive tumors and the CCL5/CCR5 pathway is a novel potential therapeutic target.

Biomarker Discovery for Immunotherapy of Pituitary Adenomas: Enhanced Robustness and Prediction Ability by Modern Computational Tools

Pituitary adenoma (PA) is prevalent in the general population. Due to its severe complications and aggressive infiltration into the surrounding brain structure, the effective management of PA is required. Till now, no drug has been approved for treating non-functional PA, and the removal of cancerous cells from the pituitary is still under experimental investigation. Due to its superior specificity and safety profile, immunotherapy stands as one of the most promising strategies for dealing with PA refractory to the standard treatment, and various studies have been carried out to discover immune-related gene markers as target candidates. However, the lists of gene markers identified among different studies are reported to be highly inconsistent because of the greatly limited number of samples analyzed in each study. It is thus essential to substantially enlarge the sample size and comprehensively assess the robustness of the identified immune-related gene markers. Herein, a novel strategy of direct data integration (DDI) was proposed to combine available PA microarray datasets, which significantly enlarged the sample size. First, the robustness of the gene markers identified by DDI strategy was found to be substantially enhanced compared with that of previous studies. Then, the DDI of all reported PA-related microarray datasets were conducted to achieve a comprehensive identification of PA gene markers, and 66 immune-related genes were discovered as target candidates for PA immunotherapy. Finally, based on the analysis of human protein⁻protein interaction network, some promising target candidates (GAL, LMO4, STAT3, PD-L1, TGFB and TGFBR3) were proposed for PA immunotherapy. The strategy proposed together with the immune-related markers identified in this study provided a useful guidance for the development of novel immunotherapy for PA.

Identification of Transcriptional Metabolic Dysregulation in Subtypes of Pituitary Adenoma by Integrated Bioinformatics Analysis

BACKGROUND

Pituitary adenoma (PA) is a prevalent intracranial tumor. Metabolites differ between pituitary tumor and healthy tissues or among different tumor subtypes. However, the transcriptional changes in metabolic enzymes, which are usually seemed as targets for metabolic therapy, remain unidentified.

METHODS

Using microarray data for 160 samples from the Gene Expression Omnibus database, across the four most common tumor subtypes, we present the integrated identification of differentially expressed genes (DEGs) between tumors and controls.

RESULTS

Subtype-specific DEGs revealed 1081 prolactin tumor-specific DEGs, 437 nonfunctioning tumor-specific DEGs, and 217 common DEGs among the four subtypes. Functional enrichment showed that a lot of biological functions related to metabolism had changed. Twenty-one prolactin and twenty-three nonfunctioning tumor-specific metabolic-related DEGs are mainly involved in fatty acid and nucleotide metabolism, redox reaction, and gluconeogenesis. Eighteen metabolic-related DEGs enriched in the metabolism of xenobiotics by the cytochrome P450 pathway, sulfur metabolism, retinoid metabolism, and glucose homeostasis were abnormal in all subtypes of PA.

CONCLUSION

Based on a comprehensive bioinformatics analysis of the available PA-related transcriptomics data, we identified specific DEGs related to metabolism, and some of them might be new attractive therapeutic targets. Especially, PDK4 and PCK1 might be new attractive biomarkers and therapeutic targets.

Molecular Network Basis of Invasive Pituitary Adenoma: A Review

Cases with pituitary adenoma comprise 10-25% of intracranial neoplasm, being the third most common intracranial tumor, most of the adenomas are considered to be benign. About 35% of pituitary adenomas are invasive. This review summarized the known molecular basis of the invasiveness of pituitary adenomas. The study pointed out that hypoxia-inducible factor-1α, pituitary tumor transforming gene, vascular endothelial growth factor, fibroblast growth factor-2, and matrix metalloproteinases (MMPs, mainly MMP-2, and MMP-9) are core molecules responsible for the invasiveness of pituitary adenomas. The reason is that these molecules have the ability to directly or indirectly induce cell proliferation, epithelial-to-mesenchymal transition, angiogenesis, degradation, and remodeling of extracellular matrix. HIF-1α induced by hypoxia or apoplexy inside the adenoma might be the initiating factor of invasive transformation, followed with angiogenesis for overexpressed VEGF, EMT for overexpressed PTTG, degradation of ECM for overexpressed MMPs, creating a suitable microenvironment within the tumor. Together, they form a complex interactive network. More investigations are required to further elucidate the mechanisms underlying the invasiveness of pituitary adenomas.

Epithelial–Mesenchymal Transition Induced by SMAD4 Activation in Invasive Growth Hormone-Secreting Adenomas

Background

The detection and treatment of invasive growth hormone-secreting pituitary adenoma (GHPA) remains challenging. Several transcription factors promoting the epithelial–mesenchymal transition (EMT) can act as cofactors for the transforming growth factor-beta (TGF-ß)/SMAD4. The goal of this study was to investigate the association of SMAD4 expression and clinicopathologic features using a tissue microarray analysis (TMA). The levels of SMAD4 and the related genes of EMT in GHPAs were analyzed by q-PCR and western blot. SMAD4 was strongly expressed in 15/19 cases (78.9%) of invasive GHPA and 10/42 cases (23.8%) of noninvasive GHPA (χ2=10.887,p=0.000). In the high SMAD4 group, a headache was reported in 16/25 cases (64%) compared with 13/36 cases (36.1%) in the low SMAD4 group (χ2=4.565,p=0.032). The progression-free survival (PFS) in the high group was lower than that in the low group (p=0.026). qRT-PCR and western blot analysis further revealed a significant downregulation of E-cadherin and upregulation of N-cadherin and vimentin in the invasive GHPA group. SMAD4 was associated with increased levels of invasion of GH3 cells, as determined by a transwell test. SMAD4 downregulated E-cadherin levels and increased the levels of N-cadherin and vimentin. Our data provide evidence that SMAD4 is a potential prognosis biomarker and a therapeutic target for patients with invasive GHPA.

Gene expression profiling of fast- and slow-growing non-functioning gonadotroph pituitary adenomas

OBJECTIVE

Reliable biomarkers associated with aggressiveness of non-functioning gonadotroph adenomas (GAs) are lacking. As the growth of tumor remnants is highly variable, molecular markers for growth potential prediction are necessary. We hypothesized that fast- and slow-growing GAs present different gene expression profiles and reliable biomarkers for tumor growth potential could be identified, focusing on the specific role of epithelial-mesenchymal transition (EMT).

DESIGN AND METHODS

Eight GAs selected for RNA sequencing were equally divided into fast- and slow-growing group by the tumor volume doubling time (TVDT) median (27.75 months). Data were analyzed by tophat2, cufflinks and cummeRbund pipeline. 40 genes were selected for RT-qPCR validation in 20 GAs based on significance, fold-change and pathway analyses. The effect of silencing MTDH (metadherin) and EMCN (endomucin) on in vitro migration of human adenoma cells was evaluated.

RESULTS

350 genes were significantly differentially expressed (282 genes upregulated and 68 downregulated in the fast group, P-adjusted <0.05). Among 40 selected genes, 11 showed associations with TVDT (-0.669<R<-0.46, P < 0.05). These were PCDH18, UNC5D, EMCN, MYO1B, GPM6A and six EMT-related genes (SPAG9, SKIL, MTDH, HOOK1, CNOT6L and PRKACB). MTDH, but not EMCN, demonstrated involvement in cell migration and association with EMT markers.

CONCLUSIONS

Fast- and slow-growing GAs present different gene expression profiles, and genes related to EMT have higher expression in fast-growing tumors. In addition to MTDH, identified as an important contributor to aggressiveness, the other genes might represent markers for tumor growth potential and possible targets for drug therapy.

Multi-chaperone function modulation and association with cytoskeletal proteins are key features of the function of AIP in the pituitary gland

Despite the well-recognized role of loss-of-function mutations of the aryl hydrocarbon receptor interacting protein gene (AIP) predisposing to pituitary adenomas, the pituitary-specific function of this tumor suppressor remains an enigma. To determine the repertoire of interacting partners for the AIP protein in somatotroph cells, wild-type and variant AIP proteins were used for pull-down/quantitative mass spectrometry experiments against lysates of rat somatotropinoma-derived cells; relevant findings were validated by co-immunoprecipitation and co-localization. Global gene expression was studied in AIP mutation positive and negative pituitary adenomas via RNA microarrays. Direct interaction with AIP was confirmed for three known and six novel partner proteins. Novel interactions with HSPA5 and HSPA9, together with known interactions with HSP90AA1, HSP90AB1 and HSPA8, indicate that the function/stability of multiple chaperone client proteins could be perturbed by a deficient AIP co-chaperone function. Interactions with TUBB, TUBB2A, NME1 and SOD1 were also identified. The AIP variants p.R304* and p.R304Q showed impaired interactions with HSPA8, HSP90AB1, NME1 and SOD1; p.R304* also displayed reduced binding to TUBB and TUBB2A, and AIP-mutated tumors showed reduced TUBB2A expression. Our findings suggest that cytoskeletal organization, cell motility/adhesion, as well as oxidative stress responses, are functions that are likely to be involved in the tumor suppressor activity of AIP.

ADAM12 induces EMT and promotes cell migration, invasion and proliferation in pituitary adenomas via EGFR/ERK signaling pathway

Pituitary adenomas are the second most common primary brain tumor with invasive properties. We have previously identified that ADAM12 (a disintegrin and metalloprotease 12) overexpression is associated with the tumor invasion of pituitary adenomas, however, the underlying mechanism remains unknown. This study aims to elucidate the mechanistic role of ADAM12 in regulating the tumor invasion of pituitary adenomas. In this study, we first showed that ADAM12 expression was concomitant with epithelial to mesenchymal transition (EMT) process in clinical specimens of human pituitary adenomas. Further functional studies showed that ADAM12 silencing in pituitary adenoma cells significantly inhibited the EMT process and suppressed cell migration, invasion and proliferation without influencing cell apoptosis. Mechanistically, ADAM12 silencing significantly reduced ectodomain shedding of epidermal growth factor receptor (EGFR) ligands and attenuated the EGFR/ERK signaling pathway. Blocking of EGFR signaling resulted in EMT suppression similar to silencing of ADAM12 and reduced cell migration, invasion and proliferation, while EGFR activation abolished the suppression on EMT, proliferation, migration and invasion induced by ADAM12 silencing. Moreover, ADAM12 silencing significantly impaired tumorigenesis and EMT of pituitary adenoma cells in vivo. Taken together, our study provide crucial evidence that ADAM12 induces EMT and promotes cell migration, invasion and proliferation in pituitary adenomas via EGFR/ERK signaling pathway. These finds strongly suggest that ADAM12 might serve as a novel valuable therapeutic target for pituitary adenomas.

Growth Hormone and the Epithelial-to-Mesenchymal Transition

CONTEXT

Previous studies have implicated growth hormone (GH) in the progression of several cancers, including breast, colorectal, and pancreatic. A mechanism by which GH may play this role in cancer is through the induction of the epithelial-to-mesenchymal transition (EMT). During the EMT process, epithelial cells lose their defining phenotypes, causing loss of cellular adhesion and increased cell migration. This review aims to carefully summarize the previous two decades of research that points to GH as an initiator of EMT, in both cancerous and noncancerous tissues.

EVIDENCE ACQUISITION

Sources were collected using PubMed and Google Scholar search engines by using specific GH- and/or EMT-related terms. Identified manuscripts were selected for further analysis based on presentation of GH-induced molecular markers of the EMT process in vivo or in vitro.

EVIDENCE SYNTHESIS

Cellular mechanisms involved in GH-induced EMT are the focus of this review, both in cancerous and noncancerous epithelial cells.

CONCLUSIONS

Our findings suggest that a myriad of molecular mechanisms are induced by GH that cause EMT and may point to potential therapeutic use of GH antagonists or any downregulator of GH action in EMT-related disease.

Elucidating the Role of the Desmosome Protein p53 Apoptosis Effector Related to PMP-22 in Growth Hormone Tumors

Densely granulated and sparsely granulated (SG) growth hormone (GH) pituitary adenomas differ in biological behavior, which may be correlated with their known differences in cytoplasmic keratin distribution and E-cadherin expression. We wanted to explore candidate genes that might further explain this behavior. Exon expression microarray was performed on 21 GH tumors (10 SG and 11 densely granulated) and 20 normal control pituitaries from autopsy. Bioinformatic analyses confirmed a differential molecular signature between normal pituitary and GH tumors as well as between the GH tumor subtypes. There was a consistent downregulation of transcripts involved in the structure and function of the desmosome, including desmoplakin (eightfold), desmoglein 2 (sixfold), plakophilin 2 (sevenfold), and p53 apoptosis effector related to PMP-22 (PERP; sixfold) in SG tumors compared with normal pituitary. PERP is lost in more aggressive SG human GH pituitary tumors. PERP re-expression in GH3 rat GH tumor cells resulted in decreased colony formation compared with vector transfectants, confirming the role of PERP as a tumor suppressor with no effects on proliferation. Increased PERP expression was associated with loss of a survival advantage in a hypoxic environment, as assessed by terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (P < 0.05) and cleaved caspase-3 (P < 0.05). Downregulation of desmosomal formation transcripts including PERP may contribute to the aggressive phenotype seen in SG GH pituitary tumors and their behavior in response to surgery and medical therapy.

Epigenomic annotation of noncoding mutations identifies mutated pathways in primary liver cancer

Evidence that noncoding mutation can result in cancer driver events is mounting. However, it is more difficult to assign molecular biological consequences to noncoding mutations than to coding mutations, and a typical cancer genome contains many more noncoding mutations than protein-coding mutations. Accordingly, parsing functional noncoding mutation signal from noise remains an important challenge. Here we use an empirical approach to identify putatively functional noncoding somatic single nucleotide variants (SNVs) from liver cancer genomes. Annotation of candidate variants by publicly available epigenome datasets finds that 40.5% of SNVs fall in regulatory elements. When assigned to specific regulatory elements, we find that the distribution of regulatory element mutation mirrors that of nonsynonymous coding mutation, where few regulatory elements are recurrently mutated in a patient population but many are singly mutated. We find potential gain-of-binding site events among candidate SNVs, suggesting a mechanism of action for these variants. When aggregating noncoding somatic mutation in promoters, we find that genes in the ERBB signaling and MAPK signaling pathways are significantly enriched for promoter mutations. Altogether, our results suggest that functional somatic SNVs in cancer are sporadic, but occasionally occur in regulatory elements and may affect phenotype by creating binding sites for transcriptional regulators. Accordingly, we propose that noncoding mutation should be formally accounted for when determining gene- and pathway-mutation burden in cancer.

Non-functioning pituitary adenomas: growth and aggressiveness

Pituitary adenomas (PAs) are common, comprising approximately one third of all intracranial tumors. Non-functioning pituitary adenomas (NFPAs) are the most common PAs. Although usually benign, the NFPAs represent therapeutic challenges because of their location close to the optic chiasm and nerves, and the proximity to the pituitary gland. The therapeutic alternatives are surgery and radiation. To date there is no effective medical treatment. NFPAs are classified according to different modalities, but there are no reliable marker of aggressiveness to guide the clinician in monitoring the patient. More information on growth patterns with constituent biological markers are needed to tailor the care of this patient group. Studies characterizing the membrane receptors of NFPAs have shown promising results, which may give rise to the development of medical treatment.

Combining Cadherin Expression with Molecular Markers Discriminates Invasiveness in Growth Hormone and Prolactin Pituitary Adenomas

Although growth hormone (GH)- and prolactin (PRL)-secreting pituitary adenomas are considered benign, in many patients, tumour growth and/or invasion constitute a particular challenge. In other tumours, progression relies in part on dysfunction of intercellular adhesion mediated by the large family of cadherins. In the present study, we have explored the contribution of cadherins in GH and PRL adenoma pathogenesis, and evaluated whether this class of adherence molecules was related to tumour invasiveness. We have first established, by quantitative polymerase chain reaction and immunohistochemistry, the expression profile of classical cadherins in the normal human pituitary gland. We show that the cadherin repertoire is restricted and cell-type specific. Somatotrophs and lactotrophs express mainly E-cadherin and cadherin 18, whereas N-cadherin is present in the other endocrine cell types. This repertoire undergoes major differential modification in GH and PRL tumours: E-cadherin is significantly reduced in invasive GH adenomas, and this loss is associated with a cytoplasmic relocalisation of cadherin 18 and catenins. In invasive prolactinomas, E-cadherin distribution is altered and is accompanied by a mislocalisation of cadherin 18, β-catenin and p120 catenin. Strikingly, de novo expression of N-cadherin is present in a subset of adenomas and cells exhibit a mesenchymal phenotype exclusively in invasive tumours. Binary tree analysis, performed by combining the cadherin repertoire with the expression of a subset of known molecular markers, shows that cadherin/catenin complexes play a significant role in discrimination of tumour invasion.

Growth hormone tumor histological subtypes predict response to surgical and medical therapy

Growth hormone (GH) pituitary tumors are associated with significant morbidity and mortality. Current treatments, including surgery and medical therapy with somatostatin analogs (SSA), dopamine agonists and/or a GH receptor antagonist, result in disease remission in approximately half of patients. Predictors of GH tumor response to different therapies have been incompletely defined based on histologic subtype, particularly densely (DG) versus sparsely (SG) granulated adenomas. The aim of this study was to examine our own institutional experience with GH adenomas and correlate how subtype related to clinical parameters as well as response to surgery and medical therapies. A retrospective chart review of 101 acromegalic patients operated by a single neurosurgeon was performed. Clinical data were correlated with histologic subtype and disease control, as defined by IGF-1 levels, and random growth hormone levels in response to surgery and/or medical therapies. SG tumors, compared to DG, occurred in younger patients (p = 0.0010), were 3-fold larger (p = 0.0030) but showed no differences in tumor-invasion characteristics (p = 0.12). DG tumors had a higher rate of remission in response to surgery compared to SG, 65.7 vs. 14.3 % (p < 0.0001), as well as to medical therapy with SSAs (68.8 % for DG vs. 28.6 % for SG tumors; p = 0.028). SG tumors not controlled with SSAs consistently responded to a switch to, or addition of, a GH receptor antagonist. Histological GH tumor subtyping implicates a different clinical phenotype and biologic behavior, and provides prognostic significance for surgical success and response to medical therapies.

Genetic and epigenetic mutations of tumor suppressive genes in sporadic pituitary adenoma

Human pituitary adenomas are the most common intracranial neoplasms. Approximately 5% of them are familial adenomas. Patients with familial tumors carry germline mutations in predisposition genes, including AIP, MEN1 and PRKAR1A. These mutations are extremely rare in sporadic pituitary adenomas, which therefore are caused by different mechanisms. Multiple tumor suppressive genes linked to sporadic tumors have been identified. Their inactivation is caused by epigenetic mechanisms, mainly promoter hypermethylation, and can be placed into two groups based on their functional interaction with tumor suppressors RB or p53. The RB group includes CDKN2A, CDKN2B, CDKN2C, RB1, BMP4, CDH1, CDH13, GADD45B and GADD45G; AIP and MEN1 genes also belong to this group. The p53 group includes MEG3, MGMT, PLAGL1, RASSF1, RASSF3 and SOCS1. We propose that the tumor suppression function of these genes is mainly mediated by the RB and p53 pathways. We also discuss possible tumor suppression mechanisms for individual genes.

Epithelial splicing regulator protein 1 and alternative splicing in somatotroph adenomas

Somatotroph adenomas secrete supraphysiological amounts of GH, causing acromegaly. We have previously hypothesized that epithelial mesenchymal transition (EMT) may play a central role in the progression of these adenomas and that epithelial splicing regulator 1 (ESRP1) may function prominently as a master regulator of the EMT process in pituitary adenomas causing acromegaly. To further elucidate the role of ESRP1 in somatotroph adenomas and in EMT progression, we used RNA sequencing (RNAseq) to sequence somatotroph adenomas characterized by high and low ESRP1 levels. Transcripts identified by RNAseq were analyzed in 65 somatotroph adenomas and in GH-producing pituitary rat cells with a specific knockdown of Esrp1. The clinical importance of the transcripts was further investigated by correlating mRNA expression levels with clinical indices of disease activity and treatment response. Many of the transcripts and isoforms identified by RNAseq and verified by quantitative PCR were involved in vesicle transport and calcium signaling and were associated with clinical outcomes. Silencing Esrp1 in GH3 cells resulted in changes of gene expression overlapping the data observed in human somatotroph adenomas and revealed a decreased granulation pattern and attenuated GH release. We observed an alternative splicing pattern for F-box and leucine-rich repeat protein 20, depending on the ESPR1 levels and on changes in circulating IGF-I levels after somatostatin analog treatment. Our study indicates that ESRP1 in somatotroph adenomas regulates transcripts that may be essential in the EMT progression and in the response to somatostatin analog treatment.

Attenuated RORC expression in the presence of EMT progression in somatotroph adenomas following treatment with somatostatin analogs is associated with poor clinical recovery

Somatostatin analogs (SA) have been established as the first line medical treatment for acromegaly, but following long-term treatment, SA normalizes GH and IGF-I levels in only 40–60% of patients. The epithelial marker E-cadherin plays a crucial role in the epithelial mesenchymal transition (EMT) and is associated with a poor response to SA treatment. We hypothesized that the characterization of transcripts regulated by SA in somatotroph adenomas with high and low E-cadherin expression may identify signaling pathways and mediators that can explain the poor response to SA treatment. We performed a microarray analysis of sixteen adenomas with different levels of E-cadherin and SA treatment to identify regulated transcripts. Candidate transcripts were further explored in vivo in sixty-five adenomas, and interactions between SA treatment and EMT progression on mRNA expression profiles and associations with clinical recovery were assessed. Finally, the effects of SA treatment on adenoma cells in vitro from acromegalic patients were determined. Microarray analysis of selected adenomas with differential E-cadherin expression, as a marker of EMT progression, identified 172 genes that displayed differential expression that was dependent on SA treatment. The validation of selected candidates in the entire cohort identified 9 transcripts that showed an interaction between E-cadherin expression and SA treatment. Further analysis of the impact of these genes suggests that attenuated RORC expression in somatotroph adenomas is associated with increased tumor size and a blunted clinical response. Our study indicates that attenuated RORC may be involved in the poor clinical response to SA treatment in patients with acromegaly.

During embryogenesis, esrp1 expression is restricted to a subset of epithelial cells and is associated with splicing of a number of developmentally important genes

BACKGROUND

Development of a mature organism from a single cell requires a series of important morphological changes, which is in part regulated by alternative splicing. In this article, we report the expression of Esrp1 during early mouse embryogenesis, a splicing factor implicated in epithelial to mesenchymal transitions.

RESULTS

By qRT-PCR, we find higher expression of Esrp1 and Esrp2 in placenta compared to the embryos. We also find a correlation between the expression of Esrp1 and alternative splicing of several known target exons. Using in situ RNA hybridization we show that while Esrp1 expression is ubiquitous in embryonic day (E)6.5 mouse embryos, expression becomes restricted to the chorion and definitive endoderm starting at E7.5. Esrp1 expression was consistently restricted to a subset of epithelial cell types in developing embryos from E9.5 to E13.5.

CONCLUSIONS

Our results suggest that Esrp1 could play an important role in the morphological changes underlying embryogenesis of the placenta and embryo.