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

The effect of miR-23b-3p on regulating GH by targeting POU1F1 in Yanbian yellow cattle

This study aimed to evaluate the effect of miR-23b-3p on growth hormone (GH) in pituitary cells of Yanbian yellow cattle. The mRNA and protein levels of GH and miR-23b-3p target genes were measured by real time fluorescence quantitative PCR (qPCR) and Western blot, respectively. The target relationship of miR-23b-3p was validated by double luciferase reporter gene system. The results showed that GH mRNA and protein levels in pituitary cells of Yanbian yellow cattle were significantly lower in the miR-23b-3p-mi group than in the NC group (P<0.01), while GH mRNA and protein levels were higher in the miR-23b-3p-in group than in the iNC group (P<0.05). The result of bioinformatics analysis and double luciferase reporter gene system validation proved that miR-23b-3p targeted 3'UTR of pituitary specific transcription factor 1 (POU1F1). POU1F1 mRNA and protein levels were lower miR-23b-3p-mi group than in the NC group (P<0.01), while POU1F1 mRNA and protein levels were higher in the miR-23b-3p-in group than in the iNC group (P<0.01). These results demonstrated that miR-23b-3p could regulate GH expression in pituitary cells by regulating POU1F1 gene.

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.

Resistance of neuroendocrine tumours to somatostatin analogs

INTRODUCTION

A common feature shared by most neuroendocrine tumors (NETs) is the expression on their surface of somatostatin receptors (SSTRs) that are essential for their pathophysiological regulation, diagnosis, and management. The first-generation synthetic somatostatin analogs (SSAs), octreotide and lanreotide, constitute the cornerstone of treatment for growth hormone secreting pituitary adenomas and functioning, progressive functioning, and non-functioning gastro-entero-pancreatic (GEP-NETs). SSAs exert their mechanism of action through binding to the SSTRs; however, their therapeutic response is frequently attenuated or diminished by the development of resistance. The phenomenon of resistance is complex implicating the presence of additional epigenetic and genetic mechanisms.

AREAS COVERED

We aim to analyze the molecular, genetic, and epigenetic mechanisms of resistance to SSA treatment. We also summarize recent clinical data related to the development of resistance on conventional and non-conventional modes of administration of the first-generation SSAs and the second-generation SSA pasireotide. We explore mechanisms used to counteract the resistance to SSAs using higher doses or more frequent mode of administration of SSAs and/or combination treatments.

EXPERT OPINION

There is considerable heterogeneity in the development of resistance to SSAs that is tumor-specific necessitating the delineation of the underlying pathophysiological processes to further expand their therapeutic applications.

Emerging Roles of miRNA, lncRNA, circRNA, and Their Cross-Talk in Pituitary Adenoma

Pituitary adenoma (PA) is a common intracranial tumor without specific biomarkers for diagnosis and treatment. Non-coding RNAs (ncRNAs), including microRNAs (miRNA), long non-coding RNA (lncRNA), and circular RNA (circRNA), regulate a variety of cellular processes, such as cell proliferation, differentiation, and apoptosis. Increasing studies have shown that the dysregulation of ncRNAs, especially the cross-talk between lncRNA/circRNA and miRNA, is related to the pathogenesis, diagnosis, and prognosis of PA. Therefore, ncRNAs can be considered as promising biomarkers for PA. In this review, we summarize the roles of ncRNAs from different specimens (i.e., tissues, biofluids, cells, and exosomes) in multiple subtypes of PA and highlight important advances in understanding the contribution of the cross-talk between ncRNAs (e.g., competing endogenous RNAs) to PA disease.

Genetic and Epigenetic Pathogenesis of Acromegaly

Simple Summary

Various genetic and epigenetic factors are involved in the pathogenesis of somatotroph tumors. Although GNAS mutations are the most prevalent cause of somatotroph tumors, the cause of half of all pathogenesis occurrences remains unclarified. However, recent findings including the pangenomic analysis, such as genome, transcriptome, and methylome approaches, and histological characteristics of pituitary tumors, the involvement of AIP and GPR101, the mechanisms of genomic instability, and possible involvement of miRNAs have gradually unveiled the whole landscape of underlying mechanisms of somatotroph tumors. In this review, we will focus on the recent advances in the pathogenesis of somatotroph tumors.

Abstract

Acromegaly is caused by excessive secretion of GH and IGF-I mostly from somatotroph tumors. Various genetic and epigenetic factors are involved in the pathogenesis of somatotroph tumors. While somatic mutations of GNAS are the most prevalent cause of somatotroph tumors, germline mutations in various genes (AIP, PRKAR1A, GPR101, GNAS, MEN1, CDKN1B, SDHx, MAX) are also known as the cause of somatotroph tumors. Moreover, recent findings based on multiple perspectives of the pangenomic approach including genome, transcriptome, and methylome analyses, histological characterization, genomic instability, and possible involvement of miRNAs have gradually unveiled the whole landscape of the underlying mechanisms of somatotroph tumors. In this review, we will focus on the recent advances in genetic and epigenetic pathogenesis of somatotroph tumors.

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.

Circulating Plasma MicroRNA in Patients With Active Acromegaly

CONTEXT

Excessive production of growth hormone causes marked multiorgan changes in patients with acromegaly, which may involve epigenetic mechanisms.

OBJECTIVE

To evaluate differences in circulating microRNAs (miRNAs) associated with chronic growth hormone overproduction in adults.

DESIGN AND SETTING

A cross-sectional case-control study was conducted at a tertiary medical center.

PARTICIPANTS

We enrolled 12 consecutive patients with acromegaly along with 12 age- and sex-matched controls in the discovery phase of the study and then extended this cohort to 47 patients with acromegaly and 28 healthy controls for the validation study.

MAIN OUTCOME MEASURES

Plasma miRNAs were quantified by next-generation sequencing (NGS) in the discovery phase. Levels of selected miRNAs were validated on extended cohorts using reverse transcription quantitative polymerase chain reaction (RT-qPCR), compared between groups, and correlated with clinical parameters.

RESULTS

Based on NGS data, we selected 3 plasma miRNAs downregulated in patients with acromegaly compared to healthy controls: miR-4446-3p -1.317 (P = 0.001), miR-215-5p -3.040 (P = 0.005), and miR-342-5p -1.875 (P = 0.013) without multiplicity correction for all 3 miRNAs. These results were confirmed by RT-qPCR in the validation phase for 2 miRNAs out of 3: miR-4446-3p (P < 0.001, Padjusted < 0.001), area under the receiver-operator curve (AUC) 0.862 (95% CI 0.723-0.936; P < 0.001) and miR-215-5p (P < 0.001, Padjusted < 0.001), AUC 0.829 (95% CI 0.698-0.907; P < 0.001) to differentiate patients with acromegaly from healthy controls.

CONCLUSIONS

In a 2-phase experiment using 2 different techniques we found and validated the downregulation of plasma miR-4446-3p and miR-215-5p in patients with acromegaly compared to healthy subjects, which makes them promising biomarkers for further research.

MicroRNAs as Potential Biomarkers in Pituitary Adenomas

Pituitary adenomas (PAs) are one of the most common lesions of intracranial neoplasms, occurring in approximately 15% of the general population. They are typically benign, although some adenomas show aggressive behavior, exhibiting rapid growth, drug resistance, and invasion of surrounding tissues. Despite ongoing improvements in diagnostic and therapeutic strategies, late first diagnosis is common, and patients with PAs are prone to relapse. Therefore, earlier diagnosis and prevention of recurrence are of importance to improve patient care. MicroRNAs (miRNAs) are short non-coding single stranded RNAs that regulate gene expression at the post-transcriptional level. An increasing number of studies indicate that a deregulation of their expression patterns is related with pituitary tumorigenesis, suggesting that these small molecules could play a critical role in contributing to tumorigenesis and the onset of these tumors by acting either as oncosuppressors or as oncogenes, depending on the biological context. This paper provides an overview of miRNAs involved in PA tumorigenesis, which might serve as novel potential diagnostic and prognostic non-invasive biomarkers, and for the future development of miRNA-based therapeutic strategies for PAs.

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.

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.

The Search of miRNA Related to Invasive Growth of Nonfunctioning Gonadotropic Pituitary Tumors

PURPOSE

Nonfunctioning gonadotropic pituitary neuroendocrine tumors (PitNETs) are among the most frequent neoplasms of pituitary gland. Although PitNETs are commonly considered benign, a notable part of patients suffer from tumor recurrence after treatment. Invasive growth of pituitary tumor is among the most important prognostic factors. Since molecular features of invasiveness are of potential clinical usefulness, this study was aimed to verify whether invasive and noninvasive nonfunctioning gonadotropic PitNETs differ in the miRNA expression profile and whether the differences could provide a possible molecular classifier.

METHODS

miRNA profiles were determined in 20 patients (11 invasive and 9 noninvasive tumors) using next-generation sequencing. The expression of selected miRNAs was assessed in the independent cohort of 80 patients with qRT-PCR.

RESULTS

When miRNA profiles of invasive and noninvasive tumors were compared, 29 miRNAs were found differentially expressed. Hsa-miR-184, hsa-miR-181a-2-3p, hsa-miR-93-3p, hsa-miR-574-5p, hsa-miR-185-5p, and hsa-miR-3200-5p showed a potential clinical value according to ROC curve analysis. Unfortunately, differential expression of only hsa-miR-185-5p was confirmed in the validation cohort, with AUG at 0.654.

CONCLUSION

Differences in miRNAs expression profiles in invasive and noninvasive gonadotropic PitNETs are slight and the level of miRNA expression seems not to be applicable as useful classifier of tumor invasiveness.

Reduction of miR-212 contributes to pituitary adenoma cell invasion via targeting c-Met

The current study aimed to evaluate the expression and role of miR-212 in the progression of pituitary adenoma (PA), thereby providing a theoretical basis and potential therapy methods for PA patients. Our data showed that miR-212 levels were significantly reduced in PA tissues than normal pituitary tissues. However, no significant difference was identified in the serum of PA patients and healthy control. In addition, the expression of miR-212 in invasive PA was significantly lower than that in noninvasive and normal pituitary tissues. Moreover, the level of miR-212 was decreased with the increase of tumor invasion. Meanwhile, the expression of miR-212 in giant adenomas was significantly lower than that in macroadenomas and microadenomas. Furthermore, inhibition of miR-212 significantly enhanced the proliferation and invasive capacity of GH3 cells. Dual luciferase reporter assay and western blot analysis confirmed that c-Met was a target gene of miR-212. More importantly, upregulation of c-Met significantly prompted PA cell proliferation mainly as a result of the enhanced level of phosphorylation of AKT. This effect could be abolished when c-Met was silenced in GH3 cells. In summary, reduced miR-212 expression in PA contributed to abnormal cancer cell proliferation and invasion mainly by targeting c-Met.

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.

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.

MicroRNAs in pituitary tumors

Since the presence of microRNAs was first observed in normal pituitary, the majority of scientific publications addressing their role and the function of microRNAs in the pituitary have been based on pituitary tumor studies. In this review, we briefly describe the involvement of microRNAs in the synthesis of pituitary hormones and we present a comprehensive inventory of microRNA suppressors and inducers of pituitary tumors. Finally, we summarize the functional role of microRNAs in tumorigenesis, progression and aggressiveness of pituitary tumors, mechanisms contributing to the regulation (transcription factors, genomic modifications or epigenetic) or modulation (pharmacological treatment) of microRNAs in these tumors, and the interest of thoroughly studying the expression of miRNAs in body fluids.

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.