Differential expression of microRNAs in GH-secreting pituitary adenomas

The emerging role of miRNAs in pituitary adenomas: From molecular signatures to diagnostic potential

Pituitary adenomas (PAs) are an array of tumors originating from the pituitary gland. PAs are sorted as functional or nonfunctional according to their hormonal activity and classified according to size into microadenomas and macroadenomas. Still, the cellular events that trigger the transformations in pituitary neoplasms are not fully understood, and the current classification methods do not precisely predict clinical behavior. A rising number of researches have emphasized the role of miRNAs, that drawn more attention as oncogenic molecules or tumor suppressors. The etiopathological mechanisms of PAs include multiple molecular cascades that are influenced by different miRNAs. miRNAs control the cell cycle control, pro- or antiapoptotic processes, and tumor invasion and metastasis. miRNAs offer a novel perspective on tumor features and behaviors and might be valuable in prognostication and therapeutic plans. In pituitary adenomas, miRNAs showed a specific expression pattern depending on their size, cell origin, remission, and treatments. Screening miRNA expression patterns is promising to monitor and evaluate recurrence, as well as to investigate the efficacy of radiation and chemotherapy for PAs exhibiting aggressive behavior. Thus, the current review investigated the interplay of the miRNAs' pivotal role in offering new opportunities to translate these innovative epigenetic tools into healthcare applications.

The molecular biology of sporadic acromegaly

GH-secreting tumors represent 15 % to 20 % of all pituitary neuroendocrine tumors (pitNETs), of which 95 % occur in a sporadic context, without an identifiable inherited cause. Recent multi-omic approaches have characterized the epigenomic, genomic, transcriptomic, proteomic and kynomic landscape of pituitary tumors. Transcriptomic analysis has allowed us to discover specific transcription factors driving the differentiation of pituitary tumors and gene expression patterns. GH-secreting, along with PRL- and TSH-secreting pitNETs are driven by POU1F1; ACTH-secreting tumors are determined by TBX19; and non-functioning tumors, which are predominantly of gonadotrope differentiation are conditioned by NR5A1. Upregulation of certain miRNAs, such as miR-107, is associated with tumor progression, while downregulation of others, like miR-15a and miR-16-1, correlates with tumor size reduction. Additionally, miRNA expression profiles are linked to treatment resistance and clinical outcomes, providing insights into potential therapeutic targets. Specific somatic mutations in GNAS, PTTG1, GIPR, HGMA2, MAST and somatic variants associated with cAMP, calcium signaling, and ATP pathways have also been associated with the development of acromegaly. This review focuses on the oncogenic mechanisms by which sporadic acromegaly can develop, covering a complex series of molecular alterations that ultimately alter the balance between proliferation and apoptosis, and dysregulated hormonal secretion.

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.

miR-383-5p, miR-181a-5p, and miR-181b-5p as Predictors of Response to First-Generation Somatostatin Receptor Ligands in Acromegaly

Acromegaly is a chronic systemic disease caused in the vast majority of cases by growth hormone (GH)-secreting adenoma, with surgery being the first-line treatment. When a cure is not attained with surgery, first-generation somatostatin receptor ligands (fg-SRLs) are the most common medication prescribed. Predictors of response to fg-SRLs have been studied; however, they cannot fully predict the response to fg-SRL. MicroRNAs are small RNAs, the main role of which is messenger RNA (mRNA) post-transcriptional regulation. This study aimed to identify the microRNAs involved in resistance to treatment with fg-SRLs in acromegaly. Ten patients with acromegaly undergoing treatment with fg-SRLs were selected to undergo miRNA sequencing: five controlled and five uncontrolled with treatment. Bioinformatic analysis was performed to detect differentially expressed miRNAs. Then, the same 10 samples were used for validation by qPCR and an additional 22 samples were analyzed, totaling 32 samples. e We found 59 differentially expressed miRNAs in the first analysis. miR-181a-5p and miR-181b-5p were downregulated, and miR-383-5p was upregulated in the uncontrolled group. Receiver operating characteristic (ROC) curve analysis of miR-383-5p showed an NPV of 84.3% and a PPV of 84.5%. In summary, miR-181a-5p, miR-181b-5p, and miR-383-5p are biomarkers of response to fg-SRLs, and they can be used individually or included in prediction models as tools to guide clinical decisions.

Exosomal RNAs in the development and treatment of pituitary adenomas

Exosomes are small extracellular vesicles that carry various bioactive molecules including various RNAs that modulate the activities of recipient cells. It has drawn considerable attention as means of cell communication and drug delivery. Exosome plays important role in various tumors, but it is rarely summarized in pituitary adenoma (PA). PA is the second most common primary central nervous system tumor, and its recurrence and persistent postoperative hormone hypersecretion lead to compromised quality of life. How exactly exosomes impact tumor development and hormone secretion is important for the development of this tumor diagnosis and treatment. In this review, we discuss how exosomal RNAs impact PAs and their potential as future clinical therapies. In our literature review, first, we found that exosomal microRNA hsa-miR-1180-3p is a potential early biomarker for NFPAs. Since NFPAs are typically difficult to diagnose, this is an especially important finding. Second, exosomal protein transcripts are potential invasive biomarker, such as MMP1, N-cadherin, CDK6, RHOU, INSM1, and RASSF10. Third, exosomal contents such as hsa-miR-21-5p promote distant bone formation of GHPA patients. Fourth, tumor suppressors in the exosome constitute novel therapeutic application of exosome, including long noncoding RNA (lncRNA) H19, miR-149-5p, miR-99a-3p, and miR-423-5p. This review discusses the possible mechanisms of exosome and their contents in PA and promotes the use of exosomes in both clinical diagnosis and treatment of this tumor.

Genome wide analysis of circulating miRNAs in growth hormone secreting pituitary neuroendocrine tumor patients’ plasma

Background

Circulating plasma miRNAs have been increasingly studied in the field of pituitary neuroendocrine tumor (PitNET) research. Our aim was to discover circulating plasma miRNAs species associated with growth hormone (GH) secreting PitNETs versus assess how the plasma levels of discovered miRNA candidates are impacted by SSA therapy and whether there is a difference in their levels between GH secreting PitNETs versus other PitNET types and healthy individuals.

Design

We compared plasma miRNA content and levels before and after surgery focusing on GH secreting PitNET patients. Selected miRNA candidates from our data and literature were then tested in a longitudinal manner in somatostatin analogues (SSA) treatment group. Additionally, we validated selected targets in an independent GH secreting PitNET group.

Methods

miRNA candidates were discovered using the whole miRNA sequencing approach and differential expression analysis. Selected miRNAs were then analyzed using real-time polymerase chain reaction (qPCR).

Results

Whole miRNA sequencing discovered a total of 16 differentially expressed miRNAs (DEMs) in GH secreting PitNET patients’ plasma 24 hours after surgery and 19 DEMs between GH secreting PitNET patients’ plasma and non-functioning (NF) PitNET patients’ plasma. Seven miRNAs were selected for further testing of which miR-625-5p, miR-503-5p miR-181a-2-3p and miR-130b-3p showed a significant downregulation in plasma after 1 month of SSA treatment. mir-625-5p was found to be significantly downregulated in plasma of GH secreting PitNET patients vs. NF PitNET patients. miR-625-5p alongside miR-130b-3p were also found to be downregulated in GH PitNETs compared to healthy individuals.

Conclusions

Our study suggests that expression of plasma miRNAs miR-625-5p, miR-503-5p miR-181a-2-3p and miR-130b-3p in GH secreting PitNETs is affected by SSA treatment. Additionally, miR-625-5p can distinguish GH secreting PitNETs from other PitNET types and healthy controls warranting further research on these miRNAs for treatment efficacy.

MicroRNA in Acromegaly: Involvement in the Pathogenesis and in the Response to First-Generation Somatostatin Receptor Ligands

Acromegaly is a chronic and systemic disease due to excessive growth hormone and insulin-like growth factor type I caused, in the vast majority of cases, by a GH-secreting pituitary adenoma. About 40% of these tumors have somatic mutations in the stimulatory G protein alpha-subunit 1 gene. The pathogenesis of the remaining tumors, however, is still not fully comprehended. Surgery is the first-line therapy for these tumors, and first-generation somatostatin receptor ligands (fg-SRL) are the most prescribed medications in patients who are not cured by surgery. MicroRNAs are small, non-coding RNAs that control the translation of many mRNAs, and are involved in the post-transcriptional regulation of gene expression. Differentially expressed miRNAs can explain differences in the pathogenesis of acromegaly and tumor resistance. In this review, we focus on the most validated miRNAs, which are mainly involved in acromegaly’s tumorigenesis and fg-SRL resistance, as well as in circulating miRNAs in acromegaly.

Rno_circ_0001004 Acts as a miR-709 Molecular Sponge to Regulate the Growth Hormone Synthesis and Cell Proliferation

(1) Background: As a novel type of non-coding RNA with a stable closed-loop structure, circular RNA (circRNA) can interact with microRNA (miRNA) and influence the expression of miRNA target genes. However, circRNA involved in pituitary growth hormone (GH) regulation is poorly understood. Our previous study revealed protein kinase C alpha (PRKCA) as the target gene of miR-709. Currently, the expression and function of rno_circRNA_0001004 in the rat pituitary gland is not clarified; (2) Methods: In this study, both bioinformatics analysis and dual-luciferase report assays showed a target relationship between rno_circRNA_0001004 and miR-709. Furthermore, the rno_circRNA_0001004 overexpression vector and si-circ_0001004 were constructed and transfected into GH₃ cells; (3) Results: We found that rno_circRNA_0001004 expression was positively correlated with the PRKCA gene and GH expression levels, while it was negatively correlated with miR-709. In addition, overexpression of rno-circ_0001004 also promoted proliferation and relieved the inhibition of miR-709 in GH₃ cells; (4) Conclusions: Our findings show that rno_circ_0001004 acts as a novel sponge for miR-709 to regulate GH synthesis and cell proliferation, and are the first case of discovery of the regulatory role of circRNA_0001004 in pituitary GH.

The Involvement of miRNAs in Pituitary Adenomas Pathogenesis and the Clinical Implications

Pituitary adenomas (PAs) account for the top three primary intracranial tumors in terms of total incidence rate. PAs can cause severe endocrine disorders and even malignant features, such as invasion, metastasis, and recurrence. Therefore, the early diagnosis and accurate prognosis would be greatly beneficial for clinical treatment of PAs. MicroRNAs (miRNAs) are small, protein-noncoding RNAs that regulate gene expression posttranscriptionally. They regulate essential physiological processes, including proliferation, growth, and apoptosis, and also they involve in the invasion and metastasis of malignant tumors. At the tissue level, differential miRNA expression in endocrine malignancies including PAs has been reported. When miRNAs have been successfully detected in various biofluids and cell-free environments, their important roles as potential screening or prognostic biomarkers have been extensively investigated. The current work reviews recent studies on the emerging roles of miRNAs in PAs and the clinical significance.

MicroRNA-Mediated Drug Repurposing Unveiled Potential Candidate Drugs for Prolactinoma Treatment

INTRODUCTION

Prolactinomas, also called lactotroph adenomas, are the most encountered type of hormone-secreting pituitary neuroendocrine tumors in the clinic. The preferred first-line therapy is a medical treatment with dopamine agonists (DAs), mainly cabergoline, to reduce serum prolactin levels, tumor volume, and mass effect. However, in some cases, patients have displayed DA resistance with aggressive tumor behavior or are faced with recurrence after drug withdrawal. Also, currently used therapeutics have notorious side effects and impair the life quality of the patients.

METHODS

Since the amalgamation of clinical and laboratory data besides tumor histopathogenesis and transcriptional regulatory features of the tumor emerges to exhibit essential roles in the behavior and progression of prolactinomas; in this work, we integrated mRNA- and microRNA (miRNA)-level transcriptome data that exploit disease-specific signatures in addition to biological and pharmacological data to elucidate a rational prioritization of pathways and drugs in prolactinoma.

RESULTS

We identified 8 drug candidates through drug repurposing based on mRNA-miRNA-level data integration and evaluated their potential through in vitro assays in the MMQ cell line. Seven repurposed drugs including 5-fluorocytosine, nortriptyline, neratinib, puromycin, taxifolin, vorinostat, and zileuton were proposed as potential drug candidates for the treatment of prolactinoma. We further hypothesized possible mechanisms of drug action on MMQ cell viability through analyzing the PI3K/Akt signaling pathway and cell cycle arrest via flow cytometry and Western blotting.

DISCUSSION

We presented the transcriptomic landscape of prolactinoma through miRNA and mRNA-level data integration and proposed repurposed drug candidates based on this integration. We validated our findings through testing cell viability, cell cycle phases, and PI3K/Akt protein expressions. Effects of the drugs on cell cycle phases and inhibition of the PI3K/Akt pathway by all drugs gave us promising output for further studies using these drugs in the treatment of prolactinoma. This is the first study that reports miRNA-mediated repurposed drugs for prolactinoma treatment via in vitro experiments.

The cAMP-signaling cancers: Clinically-divergent disorders with a common central pathway

The cAMP-signaling cancers, which are defined by functionally-significant somatic mutations in one or more elements of the cAMP signaling pathway, have an unexpectedly wide range of cell origins, clinical manifestations, and potential therapeutic options. Mutations in at least 9 cAMP signaling pathway genes (TSHR, GPR101, GNAS, PDE8B, PDE11A, PRKARA1, PRKACA, PRKACB, and CREB) have been identified as driver mutations in human cancer. Although all cAMP-signaling pathway cancers are driven by mutation(s) that impinge on a single signaling pathway, the ultimate tumor phenotype reflects interactions between five critical variables: (1) the precise gene(s) that undergo mutation in each specific tumor type; (2) the effects of specific allele(s) in any given gene; (3) mutations in modifier genes (mutational "context"); (4) the tissue-specific expression of various cAMP signaling pathway elements in the tumor stem cell; and (5) and the precise biochemical regulation of the pathway components in tumor cells. These varying oncogenic mechanisms reveal novel and important targets for drug discovery. There is considerable diversity in the "druggability" of cAMP-signaling components, with some elements (GPCRs, cAMP-specific phosphodiesterases and kinases) appearing to be prime drug candidates, while other elements (transcription factors, protein-protein interactions) are currently refractory to robust drug-development efforts. Further refinement of the precise driver mutations in individual tumors will be essential for directing priorities in drug discovery efforts that target these mutations.

Architects of Pituitary Tumour Growth

The pituitary is a master gland responsible for the modulation of critical endocrine functions. Pituitary neuroendocrine tumours (PitNETs) display a considerable prevalence of 1/1106, frequently observed as benign solid tumours. PitNETs still represent a cause of important morbidity, due to hormonal systemic deregulation, with surgical, radiological or chronic treatment required for illness management. The apparent scarceness, uncommon behaviour and molecular features of PitNETs have resulted in a relatively slow progress in depicting their pathogenesis. An appropriate interpretation of different phenotypes or cellular outcomes during tumour growth is desirable, since histopathological characterization still remains the main option for prognosis elucidation. Improved knowledge obtained in recent decades about pituitary tumorigenesis has revealed that this process involves several cellular routes in addition to proliferation and death, with its modulation depending on many signalling pathways rather than being the result of abnormalities of a unique proliferation pathway, as sometimes presented. PitNETs can display intrinsic heterogeneity and cell subpopulations with diverse biological, genetic and epigenetic particularities, including tumorigenic potential. Hence, to obtain a better understanding of PitNET growth new approaches are required and the systematization of the available data, with the role of cell death programs, autophagy, stem cells, cellular senescence, mitochondrial function, metabolic reprogramming still being emerging fields in pituitary research. We envisage that through the combination of molecular, genetic and epigenetic data, together with the improved morphological, biochemical, physiological and metabolically knowledge on pituitary neoplastic potential accumulated in recent decades, tumour classification schemes will become more accurate regarding tumour origin, behaviour and plausible clinical results.

An Exploration of Non-Coding RNAs in Extracellular Vesicles Delivered by Swine Anterior Pituitary

Extracellular vesicles are lipid bilayer-delimited particles carrying proteins, lipids, and small RNAs. Previous studies have demonstrated that they had regulatory functions both physiologically and pathologically. However, information remains inadequate on extracellular vesicles from the anterior pituitary, a key endocrine organ in animals and humans. In this study, we separated and identified extracellular vesicles from the anterior pituitary of the Duroc swine model. Total RNA was extracted and RNA-seq was performed, followed by a comprehensive analysis of miRNAs, lncRNAs, and circRNAs. Resultantly, we obtained 416 miRNAs, 16,232 lncRNAs, and 495 circRNAs. Furthermore, GO and KEGG enrichment analysis showed that the ncRNAs in extracellular vesicles may participate in regulating intracellular signal transduction, cellular component organization or biogenesis, small molecule binding, and transferase activity. The cross-talk between them also suggested that they may play an important role in the signaling process and biological regulation. This is the first report of ncRNA data in the anterior pituitary extracellular vesicles from the duroc swine breed, which is a fundamental resource for exploring detailed functions of extracellular vesicles from the anterior pituitary.

Essential Role of the 14q32 Encoded miRNAs in Endocrine Tumors

BACKGROUND

The 14q32 cluster is among the largest polycistronic miRNA clusters. miRNAs encoded here have been implicated in tumorigenesis of multiple organs including endocrine glands.

METHODS

Critical review of miRNA studies performed in endocrine tumors have been performed. The potential relevance of 14q32 miRNAs through investigating their targets, and integrating the knowledge provided by literature data and bioinformatics predictions have been indicated.

RESULTS

Pituitary adenoma, papillary thyroid cancer and a particular subset of pheochromocytoma and adrenocortical cancer are characterized by the downregulation of miRNAs encoded by the 14q32 cluster. Pancreas neuroendocrine tumors, most of the adrenocortical cancer and medullary thyroid cancer are particularly distinct, as 14q32 miRNAs were overexpressed. In pheochromocytoma and growth-hormone producing pituitary adenoma, however, both increased and decreased expression of 14q32 miRNAs cluster members were observed. In the background of this phenomenon methodological, technical and biological factors are hypothesized and discussed. The functions of 14q32 miRNAs were also revealed by bioinformatics and literature data mining.

CONCLUSIONS

14q32 miRNAs have a significant role in the tumorigenesis of endocrine organs. Regarding their stable expression in the circulation of healthy individuals, further investigation of 14q32 miRNAs could provide a potential for use as biomarkers (diagnostic or prognostic) in endocrine neoplasms.

GH and IGF System: The Regulatory Role of miRNAs and lncRNAs in Cancer

Growth hormone (GH) and the insulin-like growth factor (IGF) system are involved in many biological processes and have growth-promoting actions regulating cell proliferation, differentiation, apoptosis and angiogenesis. A recent chapter in epigenetics is represented by microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) which regulate gene expression. Dysregulated miRNAs and lncRNAs have been associated with several diseases including cancer. Herein we report the most recent findings concerning miRNAs and lncRNAs regulating GH and the IGF system in the context of pituitary adenomas, osteosarcoma and colorectal cancer, shedding light on new possible therapeutic targets. Pituitary adenomas are increasingly common intracranial tumors and somatotroph adenomas determine supra-physiological GH secretion and cause acromegaly. Osteosarcoma is the most frequent bone tumor in children and adolescents and was reported in adults who were treated with GH in childhood. Colorectal cancer is the third cancer in the world and has a higher prevalence in acromegalic patients.

Elevated miR-16-5p induces somatostatin receptor 2 expression in neuroendocrine tumor cells

Somatostatin analogs, which are used to treat neuroendocrine tumors, inhibit hormone secretion or promote tumor shrinkage; however, their efficacy varies between patients, possibly because of differential expression of somatostatin receptors (SSTRs) in tumors. In this study, we evaluated the regulatory mechanism underlying the expression of SSTR2, the main octreotide target. Thirty miRNAs were found to be dysregulated in neuroendocrine cells (INS-1 cells) incubated with octreotide compared to that in placebo-treated cells. Among the upregulated miRNAs, miR-16-5p was elevated after short-term octreotide treatment. We conducted in vitro experiments to determine whether the expression of miR-16-5p was associated with the regulation of SSTR2 expression and affected octreotide sensitivity in INS-1 cells. Overexpression of miR-16-5p by transfected mimics induced upregulation of SSTR2 expression. Additionally, the expression of miR-16-5p further enhanced octreotide-induced reduction in cell proliferation in both two- and three-dimensional culture of INS-1 cells. Thus, our results reveal the mechanism underlying SSTR2 expression regulation and may aid in developing therapeutic approaches for enhancing the response to octreotide, particularly in patients unresponsive to SSTR2-targeted somatostatin analog treatment.

MiRNAs as Noninvasive Biomarkers and Therapeutic Agents of Pituitary Adenomas

Pituitary adenoma (PA) accounts for 10-15% of all intracranial neoplasms. Even though most pituitary adenomas are benign, it is known that almost 35% of them exhibit an aggressive clinical course, including rapid proliferative activity and invasion of neighboring tissues. MicroRNAs (miRNAs) are short single-stranded RNA molecules that can influence post-transcriptional regulation by controlling target genes. Based on research data on miRNAs over the past 20 years, more than 60% of genes encoding human proteins are regulated by miRNAs, which ultimately control basic cellular mechanisms, including cell proliferation, differentiation, and apoptosis. Dysregulation of miRNAs has been observed in a number of diseases, especially tumors like PA. A majority of miRNAs are expressed within the cells themselves. However, the circulating miRNAs can be detected in several biological fluids of the human body. The identification of circulating miRNAs as new molecular markers may increase the ability to detect a tumor, predict the course of a disease, plan to choose suitable treatment, and diagnose at the earliest signs of impending neoplastic transformation. Therapy of PAs with aggressive behavior is a complex task. When surgery and chemotherapy fail, radiotherapy becomes the treatment of choice against PAs. Therefore, the possibility of implementing circulating miRNAs as innovative diagnostic and therapeutic agents for PA is one of the main exciting ideas.

miR-34a is upregulated in AIP-mutated somatotropinomas and promotes octreotide resistance

Pituitary adenomas (PAs) are intracranial tumors associated with significant morbidity due to hormonal dysregulation, mass effects and have a heavy treatment burden. Growth hormone (GH)-secreting PAs (somatotropinomas) cause acromegaly-gigantism. Genetic forms of somatotropinomas due to germline AIP mutations (AIPmut+) have an early onset and are aggressive and resistant to treatment with somatostatin analogs (SSAs), including octreotide. The molecular underpinnings of these clinical features remain unclear. We investigated the role of miRNA dysregulation in AIPmut+ vs AIPmut- PA samples by array analysis. miR-34a and miR-145 were highly expressed in AIPmut+ vs AIPmut- somatotropinomas. Ectopic expression of AIPmut (p.R271W) in Aip^-/- mouse embryonic fibroblasts (MEFs) upregulated miR-34a and miR-145, establishing a causal link between AIPmut and miRNA expression. In PA cells (GH3), miR-34a overexpression promoted proliferation, clonogenicity, migration and suppressed apoptosis, whereas miR-145 moderately affected proliferation and apoptosis. Moreover, high miR-34a expression increased intracellular cAMP, a critical mitogenic factor in PAs. Crucially, high miR-34a expression significantly blunted octreotide-mediated GH inhibition and antiproliferative effects. miR-34a directly targets Gnai2 encoding Gαi2, a G protein subunit inhibiting cAMP production. Accordingly, Gαi2 levels were significantly lower in AIPmut+ vs AIPmut- PA. Taken together, somatotropinomas with AIP mutations overexpress miR-34a, which in turn downregulates Gαi2 expression, increases cAMP concentration and ultimately promotes cell growth. Upregulation of miR-34a also impairs the hormonal and antiproliferative response of PA cells to octreotide. Thus, miR-34a is a novel downstream target of mutant AIP that promotes a cellular phenotype mirroring the aggressive clinical features of AIPmut+ acromegaly.

MicroRNAs expression in pituitary tumors: differences related to functional status, pathological features, and clinical behavior

BACKGROUND

MicroRNAs (miRNAs) are small non-coding RNA molecules that regulate gene expression at post-transcriptional level, having a role in many biological processes, such as control of cell proliferation, cell cycle, and cell death. Altered miRNA expression has been reported in many neoplasms, including pituitary adenomas (PAs).

PURPOSE

In this study, we aimed to evaluate the expression of 20 miRNAs involved in pathways relevant to pituitary pathophysiology, in PAs and normal pituitary tissue and to correlate their expression profile with clinical and pathological features.

METHODS

Pituitary tumor samples were obtained during transphenoidal surgery from patients with non-functioning (NFPA, n = 12) and functioning (n = 11, 5 GH-, 3 ACTH-, 3 PRL-omas) PAs. The expression of selected miRNAs in PAs and in normal pituitary was analyzed by RT-qPCR. miRNAs expression was correlated with demographic, clinical, and neuroradiological data and with histopathological features including pituitary hormones immunostaining, Ki-67 proliferation index, and p53 immunohistochemistry evaluation.

RESULTS

All evaluated miRNAs except miR-711 were expressed in both normal and tumor pituitary tissue. Seventeen miRNAs were significantly down-regulated in pituitary tumors compared to normal pituitary. miRNAs were differentially expressed in functioning PAs or in NFPAs, as in the latter group miR-149-3p (p = 0.036), miR-130a-3p (p = 0.014), and miR-370-3p (p = 0.026) were significantly under expressed as compared to functioning tumors. Point-biserial correlation analysis demonstrated a negative correlation between miR-26b-5p and Ki-67 (p = 0.031) and between miR-30a-5p and 'atypical' morphological features (p = 0.038) or cavernous sinus invasion (p = 0.049), while 508-5p was inversely correlated with clinical aggressiveness (p = 0.043).

CONCLUSIONS

In this study, we found a significant down-regulation of 17 miRNAs in PAs vs normal pituitary, with differential expression profile related to functional status and tumor aggressiveness.

Biomarkers for Liquid Biopsies of Pituitary Neuroendocrine Tumors

Pituitary neuroendocrine tumors (PitNET) do not only belong to the most common intracranial neoplasms but seem to be generally more common than has been thought. Minimally invasive liquid biopsies have the potential to improve their early screening efficiency as well as monitor prognosis by facilitating the diagnostic procedures. This review aims to assess the potential of using liquid biopsies of different kinds of biomarker species that have only been obtained from solid pituitary tissues so far. Numerous molecules have been associated with the development of a PitNET, suggesting that it often develops from the cumulative effects of many smaller genetic or epigenetic changes. These minor changes eventually pile up to switch critical molecules into tumor-promoting states, which may be the key regulatory nodes representing the most potent marker substances for a diagnostic test. Drugs targeting these nodes may be superior for the therapeutic outcome and therefore the identification of such pituitary-specific cellular key nodes will help to accelerate their application in medicine. The ongoing genetic degeneration in pituitary adenomas suggests that repeated tumor profiling via liquid biopsies will be necessary for personalized and effective treatment solutions.

DNA Methylation Influences miRNA Expression in Gonadotroph Pituitary Tumors

microRNAs are involved in pathogenesis of cancer. DNA methylation plays a role in transcription of miRNA-encoding genes and may contribute to changed miRNA expression in tumors. This issue was not investigated in pituitary neuroendocrine tumors (PitNETs) previously. DNA methylation patterns, assessed with HumanMethylation450K arrays in 34 PitNETs and five normal pituitaries, were used to determine differentially methylated CpGs located at miRNA genes. It showed aberrant methylation in regions encoding for 131 miRNAs. DNA methylation data and matched miRNA expression profiles, determined with next-generation sequencing (NGS) of small RNAs, were correlated in 15 PitNETs. This showed relationship between methylation and expression levels for 12 miRNAs. DNA methylation and expression levels of three of them (MIR145, MIR21, and MIR184) were determined in the independent group of 80 tumors with pyrosequencing and qRT-PCR and results confirmed both aberrant methylation in PitNETs and correlation between methylation and expression. Additionally, in silico target prediction was combined with analysis of established miRNA profiles and matched mRNA expression pattern, assessed with amplicon-based NGS to indicate putative target genes of epigenetically deregulated miRNAs. This study reveals aberrant DNA methylation in miRNA-encoding genes in gonadotroph PitNETs. Methylation changes affect expression level of miRNAs that regulate putative target genes with tumorigenesis-relevant functions.

Insights into pituitary tumorigenesis: from Sanger sequencing to next-generation sequencing and beyond

Introduction: This review explores insights provided by next-generation sequencing (NGS) of pituitary tumors and the clinical implications.Areas covered: Although syndromic forms account for just 5% of pituitary tumours, past Sanger sequencing studies pragmatically focused on them. These studies identified mutations in MEN1, CDKN1B, PRKAR1A, GNAS and SDHx causing Multiple Endocrine Neoplasia-1 (MEN1), MEN4, Carney Complex-1, McCune Albright Syndrome and 3P association syndromes, respectively. Furthermore, linkage analysis of single-nucleotide polymorphisms identified AIP mutations in 20% with familial isolated pituitary adenomas (FIPA). NGS has enabled further investigation of sporadic tumours. Thus, mutations of USP8 and CABLES1 were identified in corticotrophinomas, BRAF in papillary craniopharyngiomas and CTNNB1 in adamantinomatous craniopharyngiomas. NGS also revealed that pituitary tumours occur in the DICER1 syndrome, due to DICER1 mutations, and CDH23 mutations occur in FIPA. These discoveries revealed novel therapeutic targets and studies are underway of BRAF inhibitors for papillary craniopharyngiomas, and EGFR and USP8 inhibitors for corticotrophinomas.Expert opinion: It has become apparent that single-nucleotide variants and small insertion/deletion DNA mutations cannot explain all pituitary tumorigenesis. Integrated and improved analyses including whole-genome sequencing, copy number, and structural variation analyses, RNA sequencing and epigenomic analyses, with improved genomic technologies, are likely to further define the genomic landscape.

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.

Genetics of Pituitary Tumours

Pituitary tumours are relatively common in the general population. Most often they occur sporadically, with somatic mutations accounting for a significant minority of somatotroph and corticotroph adenomas. Pituitary tumours can also develop secondary to germline mutations as part of a complex syndrome or as familial isolated pituitary adenomas. Tumours occurring in a familial setting may present at a younger age and can behave more aggressively with resistance to treatment. This chapter will focus on the genetics and molecular pathogenesis of pituitary tumours.

Emerging Role of USP8, HMGA, and Non-Coding RNAs in Pituitary Tumorigenesis

Two novel molecular mechanisms with a driver role in pituitary tumorigenesis have been recently identified. They are (a) mutations in the Ubiquitin-Specific Protease 8 (USP8) gene in corticotroph tumors and (b) overexpression of the HMGA1 and HMGA2 genes in most of the pituitary tumors. Moreover, deregulated expression of the non-coding RNAs has been very frequently observed in this neoplasia. The aim of this review is to better elucidate the role, the mechanisms, and the possible clinical impact of these novel alterations in the development of pituitary neoplasia.

Next-generation sequencing of microRNAs reveals a unique expression pattern in different types of pituitary adenomas

Pituitary adenomas (PAs) are considered the most common intracranial tumor to cause serious morbidity because of dysregulated pituitary hormone secretions. Aberrant expression of microRNAs (miRNAs) is correlated with the development and function of the pituitary gland as well as the tumorigenesis of hypothalamic-pituitary axis-related pituitary tumors. In this study, we showed the differential expression patterns of miRNAs in NFPAs (nonfunctioning pituitary adenomas), GHPAs (growth hormone-secreting pituitary adenomas) and PRLPAs (prolactin-secreting pituitary adenomas) compared to those in three normal pituitary glands using the HiSeq 2000 sequencing system (Illumina). We validated miRNA expression using real-time quantitative polymerase chain reaction (RT-qPCR) analyses of samples from 73 patients (13 GHPAs, 42 NFPAs, and 18 PRLPAs) and 6 normal pituitary gland. We observed that miR-34c-3p was significantly downregulated in our PRLPA samples (p < 0.01), along with miR-34b-5p, miR-378 and miR-338-5p (all p < 0.05). In NFPAs, miR-493-5p was downregulated, and miR-181b-5p was significantly upregulated (p < 0.01). In GHPAs, miR-184 was significantly upregulated (p < 0.05). We observed that the tumor suppressive miR-124-3p was downregulated in both NFPAs and GHPAs. Taken together, we showed distinctive miRNA expression patterns in these three PAs, and these miRNA signatures in PA may have therapeutic potential as novel biomarkers for each type of PA.

Growth hormone and prolactin-staining tumors causing acromegaly: a retrospective review of clinical presentations and surgical outcomes

OBJECTIVE

Acromegaly results in disfiguring growth and numerous medical complications. This disease is typically caused by growth hormone (GH)-secreting pituitary adenomas, which are treated first by resection, followed by radiation and/or medical therapy if needed. A subset of acromegalics have dual-staining pituitary adenomas (DSPAs), which stain for GH and prolactin. Presentations and treatment outcomes for acromegalics with DSPAs are not well understood.

METHODS

The authors retrospectively reviewed the records of more than 5 years of pituitary adenomas resected at their institution. Data were collected on variables related to clinical presentation, tumor pathology, radiological size, and disease recurrence. The Fisher's exact test, ANOVA, Student t-test, chi-square test, and Cox proportional hazards and multiple logistic regression were used to measure statistical significance.

RESULTS

Of 593 patients with pituitary adenoma, 91 presented with acromegaly. Of these 91 patients, 69 (76%) had tumors that stained for GH only (single-staining somatotrophic adenomas [SSAs]), while 22 (24%) had tumors that stained for GH and prolactin (DSPAs). Patients with DSPAs were more likely to present with decreased libido (p = 0.012), signs of acromegalic growth (p = 0.0001), hyperhidrosis (p = 0.0001), and headaches (p = 0.043) than patients with SSAs. DSPAs presented with significantly higher serum prolactin (60.7 vs 10.0 µg/L, p = 0.0002) and insulin-like growth factor-1 (IGF-1) (803.6 vs 480.0 ng/ml, p = 0.0001), and were more likely to have IGF-1 levels > 650 ng/ml (n = 13 [81.3%] vs n = 6 [21.4%], p = 0.0001) than patients with SSAs despite similar sizes (1.8 vs 1.7 cm, p = 0.5). Patients with DSPAs under 35 years of age were more likely to have a recurrence (n = 4 [50.0%] vs n = 3 [11.1%], p = 0.01) than patients with SSAs under the age of 35. DSPA patients were less likely to achieve remission with surgery than SSA patients (n = 2 [20%] vs n = 19 [68%], p = 0.01). Univariate analysis identified single-staining tumors (p = 0.02), gross-total resection (p = 0.02), and tumor diameter (p = 0.05) as predictors of surgical remission. Multiple logistic regression demonstrated that SSAs (p = 0.04) were independently associated with surgical remission of acromegaly. Kaplan-Meier analysis revealed that DSPAs had more time until disease remission (p = 0.033).

CONCLUSIONS

Acromegalics with tumors that stain for prolactin and GH, which represented almost a quarter of acromegalics in this cohort, had more aggressive clinical presentations and postoperative outcomes than SSAs. Prolactin staining provides useful information for acromegalics undergoing pituitary surgery.

circOMA1-Mediated miR-145-5p Suppresses Tumor Growth of Nonfunctioning Pituitary Adenomas by Targeting TPT1

CONTEXT

Nonfunctioning pituitary adenomas (NFPAs) are the major cause of hypopituitarism and infertility. However, the pathogenesis of NFPAs remains largely unknown. Previous studies have demonstrated the crucial role of miRNAs in the progression of pituitary adenomas. Increasing evidence has indicated that circular RNAs (circRNAs) might mediate miRNA transcriptional activity, providing new insights to study the pathogenesis of NFPAs.

OBJECTIVES

To explore the regulation and activity of the circRNA-miRNA-mRNA axis in the tumorigenesis of NFPAs.

DESIGN

The function of miR-145-5p in NFPAs was investigated invitro and invivo. The mechanical details were explored and potential targets of miR-145-5p were identified. Finally, miR-145-5p-associated circRNAs were functionally recognized and confirmed.

RESULTS

miR-145-5p was markedly decreased in NFPA samples and correlated negatively with NFPA invasiveness. Overexpression of miR-145-5p suppressed NFPA cell proliferation and invasiveness and promoted apoptosis. Further results confirmed that translationally controlled tumor protein (TPT1) is a target of miR-145-5p and mediated the effect of miR-145-5p. TPT1 and its downstream factors Mcl-1 and Bcl-xL were downregulated, and Bax was upregulated by miR-145-5p. Moreover, circOMA1 (hsa_circRNA_0002316) was demonstrated to sponge miR-145-5p, whose suppression on NFPA cells was abrogated by circOMA1 overexpression. circOMA1 silencing exhibited a similar inhibitory effect with miR-145-5p overexpression by downregulating TPT1. We found that circOMA1 could further upregulate Mcl-1 and Bcl-xL and downregulate Bax.

CONCLUSIONS

circOMA1 promotes NFPA progression by acting as the sponge of tumor suppressor miR-145-5p to regulate the TPT1 signaling pathway, revealing a therapeutic target in preventing the tumorigenesis of NFPAs.

Comprehensive analysis of circulating microRNAs in plasma of patients with pituitary adenomas

BACKGROUND

Circulating miRNAs in pituitary adenoma would help patient care especially in non-functioning adenoma cases as minimally invasive biomarkers of tumor recurrence and progression.

AIM

Our aim was to investigate plasma miRNA profile in patients with pituitary adenoma.

MATERIALS AND METHODS

149 plasma and extracellular vesicle (preoperative, early- and late postoperative) samples were collected from 45 pituitary adenoma patients. Adenomas were characterized based on anterior pituitary hormones and transcription factors by immunostaining. MiRNA next generation sequencing was performed on 36 samples (discovery set). Individual TaqMan assay was used for validation on extended sample set. PA tissue miRNAs were evaluated by TaqMan array and literature data.

RESULTS

Global downregulation of miRNA expression was observed in plasma samples of pituitary adenoma patients compared to normal samples. Expression of 29 miRNAs and isomiR variants were able to distinguish preoperative plasma samples and normal controls. MiRNAs with altered expression in both plasma and different adenoma tissues were identified. 3, 7 and 66 miRNAs expressed differentially between preoperative and postoperative plasma samples in growth hormone secreting, FSH/LH+ and hormone-immunonegative groups, respectively. MiR-143-3p was downregulated in late- but not in early postoperative plasma samples compared to preoperative ones exclusively in FSH/LH+ adenomas. Plasma level of miR-143-3p discriminated these samples with 81.8% sensitivity and 72.3% specificity (AUC=0.79; p=0.02).

CONCLUSIONS

Differentially expressed miRNAs in pituitary adenoma tissues have low abundance in plasma minimizing their role as biomarkers. Plasma miR-143-3p decreases in patients with FSH/LH+ adenoma indicated successful surgery, but its application for evaluating tumor recurrence needs further investigation.

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.

Circulating miR-103a-3p and miR-660-5p are associated with bone parameters in patients with controlled acromegaly

Background Biochemical control of GH/IGF-I excess in acromegaly (ACRO) is associated with persistent impairment of trabecular microstructure leading to increased risk of vertebral fractures. Circulating miRNAs modulate the activity of osteoblasts and osteoclasts, and may be potential biomarkers of osteoporosis. Aims Identify differentially expressed miRNAs in the serum of patients with controlled ACRO vs controls and correlate miRNA levels with both biochemical and structural bone parameters. Patients and methods Twenty-seven patients with controlled ACRO (11 males, 16 females; mean age, 48 ± 5 years; BMI, 28 ± 4 kg/m2) and 27 age-, gender- and BMI-matched controls were recruited. Areal BMD at lumbar spine and femur, and trabecular bone score were assessed; volumetric BMD was measured by quantitative computed tomography QCT-Pro (Mindways). Twenty miRNAs, chosen by their putative role in bone, were quantified in serum using real-time qPCR. Results In ACRO patients, miR-103a-3p and miR-191-5p were found overexpressed, whereas miR-660-5p was underexpressed (P < 0.001). miR-103a-3p levels were negatively associated with both trabecular vBMD at trochanter and serum osteoprotegerin concentrations (P < 0.05) and positively with vitamin D concentrations (P < 0.01) and total cross-sectional area of the femoral neck (P < 0.05). miR-660-5p levels were correlated with both trabecular vBMD at trochanter and OPG concentrations (P < 0.05), but were negatively associated with vitamin D levels (P < 0.05). A negative correlation between miR-103-a-3p and miR-660-5p was found in both groups (P < 0.001). Conclusions Circulating miR-103a-3p and miR-660-5p are differentially expressed in controlled ACRO patients and associated with bone structural parameters. miRNAs may be one of the mechanisms involved in the pathogenesis of bone disease and could be used as biomarkers in ACRO patients.

[Role of microRNA in oncogenesis of pituitary tumors and their practical significance]

Microribonucleic acids (miRNAs) are a class of noncoding RNAs that regulate posttranscriptional gene expression. These molecules are regulators of cell proliferation, metabolism, apoptosis, and differentiation. MiRNAs are not degraded by RNAases and their concentrations can be measured in different body fluids, including serum. The expression of miRNAs varies in intact tissues and tumors, including pituitary adenomas. Pituitary tumors are encountered in 22.5% of the population and, in a number of cases, may be asymptomatic, but in case of invasion or/and hormone overproduction, their clinical presentation is severe with multiple symptoms leading to disability and even death. The mechanisms for the development and progression of pituitary tumors and the markers for remission and recurrence have not been adequately investigated. This literature review discusses the biological significance of miRNAs in pituitary tumors and the potential value of circulating miRNAs as biomarkers.

A STUDY OF THE ROLE OF MICRORNA IN PITUITARY ADENOMA

MicroRNAs are a new class of small non-coding RNAs, a length of 18–22 nucleotides that play a decisive role as posttranscriptional regulators of gene expression. Due to the large number of genes, regulated microRNAs, microRNAs are involved in many cellular processes. The study of the impairment of the expression of the target genes of microRNA, often associated with changes in important biological characteristics, provides a significant understanding of the role of microRNAs in oncogenesis. New evidence suggests that aberrant microRNA expression or dysregulation of endogenous microRNAs affects the onset and development of tumors, including adenomas of the pituitary gland. In this review, the significance of some microRNAs in the pathology of the pituitary adenoma will be assessed, as well as data on the study of microRNAs as therapeutic targets and new biomarkers.

MANAGEMENT OF ENDOCRINE DISEASE: Personalized medicine in the treatment of acromegaly

Acromegaly is associated with high morbidity and elevated mortality when not adequately treated. Surgery is the first-line treatment for most patients as it is the only one that can lead to immediate cure. In patients who are not cured by surgery, treatment is currently based on a trial-and-error approach. First-generation somatostatin receptor ligands (fg-SRL) are initiated for most patients, although approximately 25% of patients present resistance to this drug class. Some biomarkers of treatment outcome are described in the literature, with the aim of categorizing patients into different groups to individualize their treatments using a personalized approach. In this review, we will discuss the current status of precision medicine for the treatment of acromegaly and future perspectives on the use of personalized medicine for this purpose.

MicroRNA-9 regulates fetal alcohol-induced changes in D2 receptor to promote prolactin production

Fetal alcohol exposure (FAE) is known to increase prolactin (PRL) secretion from the pituitary lactotropes. In this study, we determined whether microRNAs (miRs) are involved in FAE-induced alteration in PRL release. We employed a rat animal model of FAE involving feeding pregnant Fisher 344 rats with a liquid diet containing 6.7% alcohol between gestational days 7-21 (AF). Both cyclic and estradiol-implanted FAE females showed increased levels of plasma PRL and pituitary Prl mRNA but reduced levels of pituitary dopamine D2 receptor (D2r) and its short spliced form (D2s). FAE increased the expression levels of miR-9 and miR-326 and did not produce any significant changes in miR-153 or miR-200a levels in the pituitary. Effects of FAE on miR-9 and miR-326 were associated with reduced levels of D2r and D2s, increased levels of Prl in the pituitary, and in plasma. These effects of FAE on D2r, D2s and Prl were enhanced following estradiol treatment. In PRL-producing MMQ cells, ethanol increased miR-9 but not miR-326, reduced levels of D2r and D2s and increased levels of Prl Treatment of MMQ cells with an anti-miR-9 oligo reduced ethanol effects on miR-9, D2r, D2s and Prl miR-9 mimic oligos reduced the luciferase activity of reporter vector containing D2r 3'UTR, but failed to reduce the mutant luciferase activity. These data suggest that FAE programs the pituitary to produce increased amounts of miR-9 expression that represses the D2r gene and its spliced variant D2s by targeting its 3'UTR leading to an increase in PRL production and secretion.

MicroRNA-200b inhibits pituitary tumor cell proliferation and invasion by targeting PKCα

The present study aimed to investigate the expression of miR-200b and protein kinase Cα (PKCα) in pituitary tumors and to determine whether miR-200b may inhibit proliferation and invasion of pituitary tumor cells. The regulation of PKCα expression was targeted in order to find novel targets for the treatment of pituitary tumors. In total, 53 pituitary tumor tissue samples were collected; these included 28 cases of invasive pituitary tumors and 25 cases of non-invasive tumors, in addition to 5 normal pituitaries. The expression level of miR-200b in the pituitary tumor tissue was detected by quantitative polymerase chain reaction (qPCR) and the expression of PKCα protein was detected by immunohistochemistry. A PKCα 3'untranslated region (UTR) luciferase vector was constructed and a dual luciferase reporter gene assay was employed in order to examine the effect of miR-200b on the PKCα 3'UTR luciferase activity. AtT-20 cells were transfected with miR-200b mimics, PKCα siRNA and miR-200b mimics + PKCα, and the changes in cellular proliferation, invasion and apoptosis were observed via MTT, Transwell assay and flow cytometric analysis. Furthermore, PKCα mRNA expression was determined by qPCR, and Western blotting was performed to detect the expression of PKCα protein. miR-200b revealed downregulation in invasive pituitary tumor tissue, and the expression level was significantly down-regulated compared with normal and non-invasive pituitary tumor tissue (P<0.01). In addition, the positive rate of PKCα protein expression in invasive pituitary tumor tissues was significantly higher than in normal and non-invasive tissues (P<0.01). PKCα protein levels are inversely correlated with miR-200b levels in invasive pituitary tumor tissues (r=-0.436, P=0.021). The dual luciferase reporter gene assay revealed that miR-200b could specifically bind to the 3'UTR of PKCα and significantly inhibit the luciferase activity by 39% (P<0.01). Upregulation of miR-200b or downregulation of PKCα could suppress cell proliferation and invasion, and increase apoptosis of AtT-20 cells. It was revealed that PKCα siRNA could suppress both proliferation and invasion of AtT-20 cells and partially simulate the function of miR-200b. Expression of PKCα mRNA and protein decreased significantly in AtT-20 cells overexpressing miR-200b. Additionally, miR-200b was significantly down-regulated in invasive pituitary tumor tissue and inversely correlated with PKCα protein levels. In conclusion, miR-200b inhibited proliferation and invasiveness and promoted the apoptosis of pituitary tumor cells by targeting PKCα. The observations of the present study indicate that miR-200b and PKCα may serve as promising therapeutic targets for invasive pituitary tumors.

Advancements in the study of miRNA regulation during the cell cycle in human pituitary adenomas

Pituitary adenomas (PAs), single-clone adenomas arising from pituitary gland cells, comprise one of the most frequent tumors found in the sella region. The prevalence of PAs is approximately 15%, third only after gliomas and meningioma among intracranial tumors. Autopsy and radiological analysis found that the incidence of PAs is approximately 22.5%. Most PAs are benign, although a few are malignant. Just 0.1% of patients with PAs develop pituitary carcinoma. However, owing to mass effects and unregulated secretion of pituitary hormones, PAs also lead to serious morbidity. The low rate of diagnosis at onset and the lack of effective treatments for patients with recurrent disease increase the morbidity rates. Therefore, there is an urgent need to ascertain the pathological mechanism of PAs for improved diagnosis and development of specific therapies. At present, the pathogenesis of PAs is poorly understood; however, disruption of the cell cycle is known to play an important role. MicroRNAs are short noncoding RNAs that regulate gene expression at the post-transcriptional level and play a role in regulating genes involved in carcinogenesis or tumor suppression. Previous studies have demonstrated a strong connection between dysregulation of microRNAs and dysregulation of the cell cycle in PAs. In this review, we summarize the recent progress in the study of microRNA dysregulation resulting in disruption of the cell cycle in PAs.

Genetic Aspects of Pituitary Adenomas

Although most of pituitary adenomas are benign, they may cause significant burden to patients. Sporadic adenomas represent the vast majority of the cases, where recognized somatic mutations (eg, GNAS or USP8), as well as altered gene-expression profile often affecting cell cycle proteins have been identified. More rarely, germline mutations predisposing to pituitary adenomas -as part of a syndrome (eg, MEN1 or Carney complex), or isolated to the pituitary (AIP or GPR101) can be identified. These alterations influence the biological behavior, clinical presentations and therapeutic responses, and their full understanding helps to provide appropriate care for these patients.

Strategies to use microRNAs as therapeutic targets

MicroRNAs (miRNAs) are non-coding RNAs generated from endogenous hairpin-shaped transcripts that powerfully regulate gene expression at post-transcriptional level. Each miRNA is capable to regulate the expression levels of hundreds of transcripts and each mRNA may have more than one miRNA recognition sequence. There is emerging evidence that deregulation of miRNA expression leads to the alteration of pivotal physiological functions contributing to the development of diseases and neoplasms, including pituitary adenoma. This review is aimed at providing the up-to-date knowledge concerning deregulated miRNAs of pituitary tumors and their functions. In order to take stock, pituitary tumors have been sub-divided in different classes on the basis of tumor features (histotype, dimension, aggressiveness). The overview takes full consideration of the recent advances in miRNAs role as potential therapeutics and biomarkers.

Epidemiological variations of aggressive growth hormone-secreting adenomas

Acromegaly is a chronic disorder characterized by increased morbidity and mortality in uncontrolled patients. Growth hormone-secreting pituitary adenoma is the hallmark in the majority of cases, generally considered as benign due to lack of distant metastases. However, clinical behavior in a certain proportion of these adenomas could be quite aggressive, causing difficulties in their management. Aggressive pituitary adenomas have some clinical, radiological, ultrastructural and molecular features in common and they are usually resistant to the standard treatment. In the recent years, efforts have been made to define the most appropriate markers of such adenomas that would allow an early detection and efficient individualized therapeutic strategy. The aim of this review is to give an update on epidemiology and certain markers predicting aggressive behavior of somatotropinomas.

MicroRNA-409-3p regulates cell invasion and metastasis by targeting ZEB1 in breast cancer

MicroRNA-409-3p (miR-409-3p) is an miRNA expressed by embryonic stem cells, and our previous study demonstrated depressed miR-409-3p expression in human breast cancer (BC) cell lines; however, its role and function in BC metastasis are still unknown. The purpose of this study was to examine the expression levels of miR-409-3p in human BC and its role in the metastasis of BC. We analyzed the status of miR-409-3p expression in BC tissues by quantitative real-time polymerase chain reaction (PCR) and its relationship to the clinicopathologic features of patients with BC. To study the role of miR-409-3p in BC metastasis, the invasion ability of BC cells was detected by transwell invasion assays and wound healing assays. WST-1 assays and colony formation assays were used to investigate cell proliferation. Luciferase reporter assays were used to verify that miR-409-3p targeted zinc-finger E-box-binding homeobox 1 (ZEB1). Western blot analyses and transwell assays were carried out to assess ZEB1 expression and its role in BC cell metastasis. The expression of miR-409-3p was lower in tumor tissues than in noncancerous breast tissues. We verified that miR-409-3p levels were downregulated and significantly correlated with poor outcomes in patients with BC. Overexpression of miR-409-3p inhibited cellular proliferation and suppressed cellular migration and invasion in vitro and in vivo. Dual-luciferase reporter assays showed that miR-409-3p binds the 3'-untranslated region (3'-UTR) of ZEB1, suggesting that ZEB1 is a direct target of miR-409-3p. Western blot analysis confirmed that overexpression of miR-409-3p reduced ZEB1 protein levels. These data demonstrate that miR-409-3p plays an important role in regulating the metastasis of BC, which is involved in the post-transcriptional repression of ZEB1. Our results indicate that miR-409-3p can regulate the invasion and metastasis process of BC by targeting ZEB1 and may serve as a new prognostic marker and therapeutic target for treating BC metastasis. © 2016 IUBMB Life, 68(5):394-402, 2016.

Circulating miRNAs as biomarkers for endocrine disorders

Specific, sensitive and non-invasive biomarkers are always needed in endocrine disorders. miRNAs are short, non-coding RNA molecules with well-known role in gene expression regulation. They are frequently dysregulated in metabolic and endocrine diseases. Recently it has been shown that they are secreted into biofluids by nearly all kind of cell types. As they can be taken up by other cells they may have a role in a new kind of paracrine, cell-to-cell communication. Circulating miRNAs are protected by RNA-binding proteins or microvesicles hence they can be attractive candidates as diagnostic or prognostic biomarkers. In this review, we summarize the characteristics of extracellular miRNA's and our knowledge about their origin and potential roles in endocrine and metabolic diseases. Discussions about the technical challenges occurring during identification and measurement of extracellular miRNAs and future perspectives about their roles are also highlighted.

Epidrug mediated re-expression of miRNA targeting the HMGA transcripts in pituitary cells

INTRODUCTION

Transgenic mice overexpressing the high mobility group A (HMGA) genes, Hmga1 or Hmga2 develop pituitary tumours and their overexpression is also a frequent finding in human pituitary adenomas. In some cases, increased expression of HMGA2 but not that of HMGA1 is consequent to genetic perturbations. However, recent studies show that down-regulation of microRNA (miRNA), that contemporaneously target the HMGA1 and HMGA2 transcripts, are associated with their overexpression.

RESULTS

In a cohort of primary pituitary adenoma we determine the impact of epigenetic modifications on the expression of HMGA-targeting miRNA. For these miRNAs, chromatin immunoprecipitations showed that transcript down-regulation is correlated with histone tail modifications associated with condensed silenced genes. The functional impact of epigenetic modification on miRNA expression was determined in the rodent pituitary cell line, GH3. In these cells, histone tail, miRNA-associated, modifications were similar to those apparent in human adenoma and likely account for their repression. Indeed, challenge of GH3 cells with the epidrugs, zebularine and TSA, led to enrichment of the histone modification, H3K9Ac, associated with active genes, and depletion of the modification, H3K27me3, associated with silent genes and re-expression of HMGA-targeting miRNA. Moreover, epidrugs challenges were also associated with a concomitant decrease in hmga1 transcript and protein levels and concurrent increase in bmp-4 expression.

CONCLUSIONS

These findings show that the inverse relationship between HMGA expression and targeting miRNA is reversible through epidrug interventions. In addition to showing a mechanistic link between epigenetic modifications and miRNA expression these findings underscore their potential as therapeutic targets in this and other diseases.

Expression of somatostatin receptor subtype 2 in growth hormone-secreting pituitary adenoma and the regulation of miR-185

INTRODUCTION

Long-acting somatostatin analogs (SSAs) are most widely used to treat growth hormone (GH)-secreting pituitary adenoma. However, approximately 30 % of treated patients show resistance to SSAs, which may be associated with the reduction of somatostatin receptor subtype 2 (SSTR2) mRNA and protein expression.

MATERIALS AND METHODS

The present study used immunohistochemistry to detect the expression of SSTR2 and SSTR5 in twenty human GH-secreting adenoma samples treated with SSAs and seven normal pituitary samples.

RESULTS

The staining intensities of SSTR2 and SSTR5 were stronger in most adenoma samples than in normal pituitary. The expression of SSTR2 tended to be lower in the SSA non-responder group than in responders. A search of the Bioinformatics data bank and the miRCURY™ LNA array confirmed miR-185 as the putative mircoRNA (miRNA) regulating the expression of SSTR2. An in vitro study using Dual Luciferase reporter assay demonstrated that miR-185 likely targets the 3'-UTR of SSTR2 mRNA in the rat pituitary adenoma GH3 cell line. MiR-185 also downregulated or upregulated the expression of SSTR2 mRNA and SSTR2 protein, following transfection with miR-185 mimics or inhibitors, respectively.

CONCLUSION

MiR-185 enhanced the cell proliferation and inhibited the apoptosis of GH3 cells.

Deregulation of miR-183 and KIAA0101 in Aggressive and Malignant Pituitary Tumors

Changes in microRNAs (miRNAs) expression in many types of cancer suggest that they may be involved in crucial steps during tumor progression. Indeed, miRNAs deregulation has been described in pituitary tumorigenesis, but few studies have described their role in pituitary tumor progression toward aggressiveness and malignancy. To assess the role of miRNAs within the hierarchical cascade of events in prolactin (PRL) tumors during progression, we used an integrative genomic approach to associate clinical-pathological features, global miRNA expression, and transcriptomic profiles of the same human tumors. We describe the specific down-regulation of one principal miRNA, miR-183, in the 8 aggressive (A, grade 2b) compared to the 18 non-aggressive (NA, grades 1a, 2a) PRL tumors. We demonstrate that it acts as an anti-proliferative gene by directly targeting KIAA0101, which is involved in cell cycle activation and inhibition of p53-p21-mediated cell cycle arrest. Moreover, we show that miR-183 and KIAA0101 expression significantly correlate with the main markers of pituitary tumors aggressiveness, Ki-67 and p53. These results confirm the activation of proliferation in aggressive and malignant PRL tumors compared to non-aggressive ones. Importantly, these data also demonstrate the ability of such an integrative genomic strategy, applied in the same human tumors, to identify the molecular mechanisms responsible for tumoral progression even from a small cohort of patients.

Comparative Anterior Pituitary miRNA and mRNA Expression Profiles of Bama Minipigs and Landrace Pigs Reveal Potential Molecular Network Involved in Animal Postnatal Growth

The anterior pituitary is the most important endocrine organ modulating animal postnatal growth, mainly by controlling growth hormone (GH) gene transcription, synthesis, and secretion. As an ideal model for animal postnatal growth studies, the Bama minipig is characterized as having a lower growth performance and fewer individual differences compared with larger pig breeds. In this study, anterior pituitaries from Bama minipig and Landrace pig were used for miRNA and mRNA expression profile analysis using miRNA microarrays and mRNA-seq. Consequently, a total of 222 miRNAs and 12,909 transcripts were detected, and both miRNAs and mRNAs in the two breeds showed high correlation (r > 0.97). Additionally, 41 differentially expressed miRNAs and 2,254 transcripts were identified. Pathways analysis indicated that 32 pathways significantly differed in the two breeds. Importantly, two GH-regulation-signalling pathways, cAMP and inositol 1, 4, 5-triphosphate (IP3), and multiple GH-secretion-related transcripts were significantly down-regulated in Bama minipigs. Moreover, TargetScan and RNAHybrid algorithms were used for predicting differentially expressed miRNAs (DE miRNAs) and differentially expressed mRNAs (DE mRNAs) interaction. By examining their fold-changes, interestingly, most DE miRNA-DE mRNA target pairs (63.68-71.33%) presented negatively correlated expression pattern. A possible network among miRNAs, mRNAs, and GH-regulation pathways was also proposed. Among them, two miRNA-mRNA interactions (Y-47 targets FSHB; ssc-miR-133a-3p targets GNAI3) were validated by dual-luciferase assay. These data will be helpful in understanding the possible molecular mechanisms involved in animal postnatal growth.

MicroRNA Regulation of Brain Tumour Initiating Cells in Central Nervous System Tumours

CNS tumours occur in both pediatric and adult patients and many of these tumours are associated with poor clinical outcome. Due to a paradigm shift in thinking for the last several years, these tumours are now considered to originate from a small population of stem-like cells within the bulk tumour tissue. These cells, termed as brain tumour initiating cells (BTICs), are perceived to be regulated by microRNAs at the posttranscriptional/translational levels. Proliferation, stemness, differentiation, invasion, angiogenesis, metastasis, apoptosis, and cell cycle constitute some of the significant processes modulated by microRNAs in cancer initiation and progression. Characterization and functional studies on oncogenic or tumour suppressive microRNAs are made possible because of developments in sequencing and microarray techniques. In the current review, we bring recent knowledge of the role of microRNAs in BTIC formation and therapy. Special attention is paid to two highly aggressive and well-characterized brain tumours: gliomas and medulloblastoma. As microRNA seems to be altered in the pathogenesis of many human diseases, “microRNA therapy” may now have potential to improve outcomes for brain tumour patients. In this rapidly evolving field, further understanding of miRNA biology and its contribution towards cancer can be mined for new therapeutic tools.

Alteration of the miRNA expression profile in male porcine anterior pituitary cells in response to GHRH and CST and analysis of the potential roles for miRNAs in regulating GH

OBJECTIVE

Growth hormone releasing hormone (GHRH) is a major positive regulator of growth hormone (GH) in the anterior pituitary gland, while cortistatin's (CST) role is negative. miRNAs (microRNAs or miRs) are small RNA molecules modulating gene expression at the post-transcriptional level. However, little is known about the function of miRNAs in the regulation of GH synthesis and/or secretion. This study investigated potential functional miRNAs involved in GH secretion in the normal porcine pituitary.

DESIGN

Primary porcine anterior pituitary cells were cultivated and then treated with 10 nmol/L GHRH and 100 nmol/L CST, respectively. The effects of GHRH and CST on GH secretion were determined using RIA. miRNA microarrays were employed to analyze miRNA expression after treatment and then differentially expressed miRNAs were screened. Bioinformatics analysis was used to analyze the potential targets in growth hormone regulation of altered miRNAs. Furthermore, functional experiments were conducted to study the function of ssc-let-7c.

RESULTS

GHRH significantly promoted GH secretion, while CST suppressed GH secretion. 19 and 35 differentially expressed miRNAs were identified in response to GHRH and CST treatments respectively. Verification of 5 randomly selected miRNAs by quantitative real-time PCR (qRT-PCR) showed similar changes with microarray analysis. Target analysis showed that some miRNAs may be involved in GH secretion-related pathways. Importantly, ssc-let-7c was predicted to target GH1 and GHRHR mRNA 3'untranslated regions (3'UTRs), which was supported by luciferase reporter assay. Furthermore, functional experimental results showed that ssc-let-7c was involved in GH secretion regulation, and overexpression of ssc-let-7c inhibited GH secretion in porcine anterior pituitary cells.

CONCLUSIONS

GHRH and CST modulated porcine pituitary cell miRNA expression. Bioinformatics analysis revealed a complicated network among differentially expressed miRNAs, GH regulation-related genes and hormones. More interestingly, ssc-let-7c inhibited both GH1 and GHRHR mRNA 3'UTR reporter vectors' luciferase activity and overexpression of ssc-let-7c led to a decrease of GH secretion.