The molecular pathogenesis of pituitary adenomas: an update

Plurihormonal Pituitary Neuroendocrine Tumors: Clinical Relevance of Immunohistochemical Analysis

Plurihormonal pituitary neuroendocrine tumors (PitNETs) are rare forms of tumors that express more than one hormone. The most common association is between growth hormone (GH) and prolactin (PRL), but other unusual combinations have been reported, such as GH and ACTH. Usually, the clinical dominance in these cases is related to GH hypersecretion. In these cases, immunohistochemistry (IHC) of transcription factors (TFs) is very useful for an accurate diagnosis. We included 42 patients diagnosed with pituitary neuroendocrine tumors (PitNETs): 37 patients with a confirmed diagnosis of acromegaly, and 5 patients with prolactinomas. All patients underwent transsphenoidal surgical intervention. We correlated the immunohistochemical features of plurihormonal PitNETs with clinical, hormonal, and imaging data. Tumor specimens were histologically and immunohistochemically examined. Based on the 2022 WHO classification, using IHC, 13 patients exhibited positive staining for more than one hormone, while unusual combinations like GH + ACTH and PRL + ACTH were also identified in other cases. Unusual cell combinations that produce hormones unrelated histogenetically, biochemically, or through regulatory mechanisms can appear and may display aggressive behavior, persistent disease, and high recurrence. We have not identified a clear correlation with the prognosis of these rare PitNETs.

Transcriptomic Profiles of Normal Pituitary Cells and Pituitary Neuroendocrine Tumor Cells

The pituitary gland is one of the most cellularly diverse regions of the brain. Recent advancements in transcriptomic biology, such as single-cell RNA sequencing, bring an unprecedented glimpse into the molecular composition of the pituitary, both in its normal physiological state and in disease. Deciphering the normal pituitary transcriptomic signatures provides a better insight into the ontological origin and development of five types of endocrine cells, a process involving complex cascades of transcription factors that are still being established. In parallel with these observations about normal pituitary development, recent transcriptomic findings on pituitary neuroendocrine tumors (PitNETs) demonstrate both preservations and changes in transcription factor expression patterns compared to those seen during gland development. Furthermore, recent studies also identify differentially expressed genes that drive various tumor behaviors, including hormone hypersecretion and tumor aggression. Understanding the comprehensive multiomic profiles of PitNETs is essential in developing molecular profile-based therapies for PitNETs not curable with current treatment modalities and could eventually help align PitNETs with the breakthroughs being made in applying precision medicine to other tumors.

Genomic and molecular characterization of pituitary adenoma pathogenesis: review and translational opportunities

OBJECTIVE

Innovations in genomics, epigenomics, and transcriptomics now lay the groundwork for therapeutic interventions against neoplastic disease. In the past 30 years, the molecular pathogenesis of pituitary adenomas has been characterized. This enhanced understanding of the biology of pituitary tumors has potential to impact current treatment paradigms, and there exists significant translational potential for these results. In this review the authors summarize the results of genomics and molecular biology investigations into pituitary adenoma pathogenesis and behavior and discuss opportunities to translate basic science findings into clinical benefit.

METHODS

The authors searched the PubMed and MEDLINE databases by using combinations of the keywords "pituitary adenoma," "genomics," "pathogenesis," and "epigenomics." From the initial search, additional articles were individually evaluated and selected.

RESULTS

Pituitary adenoma growth is primarily driven by unrestrained cell cycle progression, deregulation of growth and proliferation pathways, and abnormal epigenetic regulation of gene expression. These pathways may be amenable to therapeutic intervention. A significant number of studies have attempted to establish links between gene mutations and tumor progression, but a thorough mechanistic understanding remains elusive.

CONCLUSIONS

Although not currently a prominent aspect in the clinical management of pituitary adenomas, genomics and epigenomic studies may become essential in refining patient care and developing novel pharmacological agents. Future basic science investigations should aim at elucidating mechanistic understandings unique to each pituitary adenoma subtype, which will facilitate rational drug design.

Sellar Tumors

Sellar region lesions include a broad range of benign and malignant neoplastic as well as non-neoplastic entities, many of which are newly described or have recently revised nomenclature. In contrast to other intracranial sites, imaging features are relatively less specific, and the need for histopathological diagnosis is of paramount importance. This review will describe pituitary adenomas, inflammatory lesions, and tumors unique to the region (craniopharyngioma) as well as tumors which may occur in but are not exclusively localized to the sellar location (schwannoma, metastasis, etc.).

EMT-Related Markers in Serum Exosomes are Potential Diagnostic Biomarkers for Invasive Pituitary Adenomas

PURPOSE

Assessing the invasiveness of pituitary adenomas (PAs) is critical to making the best surgical and treatment plan. However, it is difficult to determine the invasiveness of pituitary adenomas based on current clinical methods, such as imaging and histological methods. The present article aims to investigate noninvasive methods to discover viable biomarkers for invasive pituitary adenomas and provide a basis for early intervention of pituitary adenomas.

METHODS

E-cadherin, N-cadherin, Epcam, TGF-β, Smad3, and Smad7 were detected in the tissues and exosomes in 10 cases of invasive PAs and 10 cases of noninvasive PAs by real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR), Western blotting, and immunohistochemical analysis.

RESULTS

Compared with that in the noninvasive group, the expression of N-cad in the exosomes of the invasive group was significantly increased, and the expression of E-cad and Epcam was reduced. In the invasive group, the expression levels of TGF-β1 and Smad3 were reduced. These results were consistent across exosomes and groups. In further cell experiments, the EMT ratio in the SIS3 treatment group, and especially in the TGF-β1 plus SIS3 treatment group (P <0.001), was significantly increased, and the EMT ratio was significantly lower when one-half the dose of TGF-β and SIS3.

CONCLUSION

The results indicate that EMT-related biomarkers in serum exosomes can be potentially used for assessing the invasiveness of pituitary adenoma.

Quantitative Analysis of Proteome in Non-functional Pituitary Adenomas: Clinical Relevance and Potential Benefits for the Patients

Background: Non-functional pituitary adenoma (NFPA) is a common tumor that occurs in the pituitary gland, and generally without any symptoms at its early stage and without clinical elevation of hormones, which is commonly diagnosed when it grows up to compress its surrounding tissues and organs. Currently, the pathogenesis of NFPA has not been clarified yet. It is necessary to investigate molecular alterations in NFPA, and identify reliable biomarkers and drug therapeutic targets for effective treatments. Methods: Tandem mass tags (TMT)-based quantitative proteomics was used to identify and quantify proteins in NFPAs. GO and KEGG enrichment analyses were used to analyze the identified proteins. Differentially expressed genes (DEGs) between NFPA and control tissues were obtained from GEO datasets. These two sets of protein and gene data were analyzed to obtain overlapped molecules (genes; proteins), followed by further GO and KEGG pathway analyses of these overlapped molecules, and molecular network analysis to obtain the hub molecules with Cytoscape. Two hub molecules (SRC and AKT1) were verified with Western blotting. Results: Totally 6076 proteins in NFPA tissues were identified, and 3598 DEGs between NFPA and control tissues were identified from GEO database. Overlapping analysis of 6076 proteins and 3598 DEGs obtained 1088 overlapped molecules (DEGs; proteins). KEGG pathway analysis of 6076 proteins obtained 114 statistically significant pathways, including endocytosis, and spliceosome signaling pathways. KEGG pathway analysis of 1088 overlapped molecules obtained 52 statistically significant pathways, including focal adhesion, cGMP-PKG pathway, and platelet activation signaling pathways. These pathways play important roles in cell energy supply, adhesion, and maintenance of the tumor microenvironment. According to the association degree in Cytoscape, ten hub molecules (DEGs; proteins) were identified, including GAPDH, ALB, ACACA, SRC, ENO2, CALM1, POTEE, HSPA8, DECR1, and AKT1. Western-blotting analysis confirmed the upregulated expressions of SRC and PTMScan experiment confirmed the increased levels of pAKT1, in NFPAs compared to controls. Conclusions: This study established the large-scale quantitative protein profiling of NFPA tissue proteome. It offers a basis for subsequent in-depth proteomics analysis of NFPAs, and insight into the molecular mechanism of NFPAs. It also provided the basic data to discover reliable biomarkers and therapeutic targets for NFPA patients.

The Role of Long Noncoding RNAs in the Biology of Pituitary Adenomas

Long noncoding RNAs (lncRNAs) are a large group of noncoding RNAs 200 nucleotides long. lncRNAs that function as regulatory factors have been identified for several complex cellular processes, such as cell death, growth, differentiation, apoptosis, epigenetic regulation, and so on. Many lncRNAs have altered expression and are likely to play a functional role in oncogenesis. The pituitary adenoma is the second most common intracranial tumor. Despite this situation, the molecular mechanism of pituitary adenoma formation has not yet been fully identified. This review summarizes recent progress in the study of lncRNAs on the pathogenesis of pituitary tumors. We cover the latest results associated with this role and highlight the therapeutic possibilities for pituitary adenomas.

Double Pituitary Adenomas with Synchronous Somatotroph and Corticotroph Clinical Presentation of Acromegaly and Cushing's Disease

BACKGROUND

Double pituitary adenomas are a rare occurrence. Synchronous clinical manifestation is extremely rare.

CASE DESCRIPTION

We report a case of a 51-year-old female with symptoms of both hypercortisolism and acromegaly during the past 2 years. Endocrine evaluation confirmed active acromegaly and revealed adrenocorticotropin hormone-dependent hypercortisolemia. Preoperative magnetic resonance imaging of the pituitary demonstrated separated double microadenomas with different intensity. Immunohistochemical analysis of each separate adenoma confirmed an exact diagnosis. The diagnosis of acromegaly and adrenocorticotropin hormone-dependent Cushing's disease was confirmed.

CONCLUSIONS

This is the third reported case in the literature of synchronous clinical manifestation of acromegaly and Cushing's disease. Extensive surgical exploration of the sella must be performed to avoid surgical failures from residual tumor. Immunohistochemical analysis is required to confirm an exact diagnosis for each of the double pituitary adenomas.

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.

Metabolic profiling reveals distinct metabolic alterations in different subtypes of pituitary adenomas and confers therapeutic targets

BACKGROUND

Pituitary adenomas are common brain tumors. Although transsphenoidal surgery are able to achieve extensive tumor removal, the rate of recurrence ranges from 5 to 20% depending on the different subtype. Further understanding of these tumors is needed to develop novel strategies to improve the prognosis of patients. But their metabolic characteristics are largely unknown.

METHODS

We used metabolomic, transcriptomic, and proteomic approaches to systematically investigate eight subtypes of pituitary adenomas and normal pituitary glands. By blocking IDH2, we investigate IDH2 play an inhibitory role in GH tumor cell growth and tumor secretion.

RESULTS

We found that all of the pituitary adenomas displayed downregulated glucose metabolism and glycolysis compared to normal tissues. Together with the differences in amino acids and fatty acids, we categorized these tumors into three clusters. We then re-established the reprogrammed metabolic flux in pituitary adenomas based on multiomic analyses. Take growth hormone-secreting pituitary adenomas as an example, we revealed that IDH2 is a key player in the reprogrammed metabolism of such tumors. By blocking IDH2, we confirmed that IDH2 is a potential target for the inhibition of tumor cell growth and tumor secretion.

CONCLUSIONS

Our study first uncovered the metabolic landscape of pituitary adenomas and demonstrated a possible way to inhibit tumor growth by regulating aberrant metabolism.

Association of ApoE haplotype with clinical evidence of pituitary adenoma

PURPOSE

To evaluate the association of the presence, invasiveness, hormonal activity and recurrence of pituitary adenoma (PA) with ApoE genotypes and alleles.

MATERIALS AND METHODS

Our study group included 142 patients with PA and the control group included 256 healthy individuals. The genotyping of ApoE (rs7412 and rs429358) was performed using a real-time PCR method.

RESULTS

After statistical analysis we found that ApoE genotype E2/E3 was associated with 2.6-fold increased odds of active PA (OR = 2.609; 95%CI: 1.380-4.932; p = 0.003), while the presence of ApoE E3/E3 decreased odds of active PA by 65% (OR = 0.343; 95%CI: 0.205-0.575; p < 0.001). The frequency of the allele ε3 was lesser in the PA group (74.3% vs. 83%, p = 0.003) when compared to controls but it was statistically significantly more frequent in the invasive PA than in the noninvasive PA subgroup (80.4% vs. 65.5%, p = 0.005). The ApoE E2/E4 genotype was more frequent in the noninvasive PA subgroup (10.3% vs. 0%, p = 0.003) than in the invasive PA subgroup. The ApoE E4/E4 genotype was more frequent in the recurrent than in the non-recurrent PA subgroup (6.6% vs. 0%, p = 0.006). No associations between ApoE polymorphisms and Ki-67 labelling index were found.

CONCLUSION

The ApoE E2/E3 genotype is associated with the presence of PA while the ApoE genotype E2/E4 is associated with noninvasive PA development. The allele ε3 could possibly have a protective effect against PA. The genotype E4/E4 is associated with the development of recurrent 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.

Differential Expression of HMGA1 and HMGA2 in pituitary neuroendocrine tumors

Defining biomarkers for invasive pituitary neuroendocrine tumors (PitNETs) is highly desirable. The high mobility group A (HMGA) proteins are among the most widely expressed cancer-associated proteins. Indeed, their overexpression is a frequent feature of human malignancies, including PitNETs. We show that nonfunctioning PitNETs (NF-PitNETs) express significantly higher levels of HMGA1 than somatotropinomas (GHs) and corticotropinomas (ACTHs). Furthermore, HMGA2 expression was detected only in NF-PitNETs and was significantly higher in larger tumors than in smaller tumors. HMGA expression analysis generally focuses on nuclear staining. Here, cytoplasmic HMGA staining was also found. PitNETs displayed strong nuclear HMGA1 and strong cytoplasmic HMGA2 immunoreactivity. Interestingly, the HMGA1 and HMGA2 nuclear expression levels were significantly higher in invasive adenomas than in noninvasive adenomas. The highest levels of nuclear HMGA2 were found in GHs. In conclusion, we show that overexpression of nuclear HMGA proteins could be a potential biomarker of invasive PitNETs, particularly HMGA2 for GHs. HMGA2 might be a reliable biomarker for NF-PitNETs.

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.

Study of major genetic factors involved in pituitary tumorigenesis and their impact on clinical and biological characteristics of sporadic somatotropinomas and non-functioning pituitary adenomas

Genetic and functional aberrations of guanine nucleotide-binding protein, alpha stimulating (GNAS), aryl hydrocarbon receptor interacting protein (AIP), and pituitary tumor transforming gene (PTTG) are among the most prominent events in pituitary tumorigenesis. A cohort of Brazilian patients with somatotropinomas (n=41) and non-functioning pituitary adenomas (NFPA, n=21) from a single tertiary-referral center were evaluated for GNAS and AIP mutations and gene expression of AIP and PTTG. Results were compared to the clinical and biological (Ki67 and p53 expression) characteristics of tumors and their response to therapy, if applicable. Genetic analysis revealed that 27% of somatotropinomas and 4.8% of NFPA harbored GNAS mutations (P=0.05). However, no differences were observed in clinical characteristics, tumor extension, response to somatostatin analog therapy, hormonal/surgical remission rates, Ki67 index, and p53 expression between mutated and non-mutated somatotropinomas patients. PTTG overexpression (RQ mean=10.6, min=4.39, max=11.9) and AIP underexpression (RQ mean=0.56, min=0.46-max=0.92) were found in virtually all cases without a statistically significant relationship with clinical and biological tumor features. No patients exhibited somatic or germline pathogenic AIP mutations. In conclusion, mutations in GNAS and abnormal PTTG and AIP expression had no impact on tumor features and treatment outcomes in this cohort. Our data support some previous studies and point to the need for further investigations, probably involving epigenetic and transcriptome analysis, to improve our understanding of pituitary tumor behavior.

Detection of circulating tumor cells in patients with pituitary tumors

BACKGROUND

Circulating tumor cells (CTCs) are tumor cells that have shed from a primary tumor and circulate in the peripheral blood. Recent experimental and clinical studies show that CTCs can be detected in early-stage disease.

CASE PRESENTATION

We report three cases of pituitary adenoma (PA) in which tumor cells with particles were detected in the interstitial vascular compartment by transmission electron microscopy. Tumors were completely resected. Immunohistochemical analysis showed a β-catenin score of 10.5 ± 1.5 in the three cases with CTCs compared with 2.4 ± 0.5 in 24 control adenomas. The Ki-67 labeling index was 2.1 ± 0.7 in CTCs vs. 0.2 ± 0.3 in control cases (p = 0.043), and the p53 score was 4.33 ± 1.3 vs. 0.31 ± 0.17 (p = 0.000). The E-cadherin score did not differ significantly between the two groups.

CONCLUSIONS

CTCs can be detected in benign tumors such as PAs and not only in late-stage malignant tumors with apparent distant metastases. The present findings suggest that pituitary carcinomas develop from adenomas.

Plurihormonal ACTH-GH Pituitary Adenoma: Case Report and Systematic Literature Review

BACKGROUND

Plurihormonal adenomas (PHAs) represent 10%-15% of all functioning pituitary adenomas. The most frequent hormonal associations are with prolactin and growth hormone (GH). Here we describe a rare case of functional adrenocorticotropic hormone (ACTH) and GH microadenoma and report our findings from a systematic literature review of PHA.

METHODS

We searched PubMed using the terms "plurihormonal pituitary adenoma," "ACTH GH pituitary adenoma," and "acromegaly AND Cushing's disease". In the 17 articles that were selected for literature review, only 20% (4/20) of patients presented with clinical signs of both diseases. Histologically, 19 were pituitary adenomas composed of two distinct cell populations, while only in 1 case was there evidence of a single cell producing both ACTH and GH. In the case reported here, a 60-year-old woman was incidentally diagnosed with a pituitary microadenoma. Endocrine assessment documented increased levels of insulin-like growth factor 1 and GH; ACTH and cortisol values were within normal ranges. Echocardiography documented ventricular hypertrophy. Because of clinical and biochemical evidence of acromegaly, surgery was recommended. Postoperatively, hormonal replacement therapy was started because of adrenal insufficiency. Her antihypertensive therapy was discontinued due to evidence of normal blood pressure values. Histological examination revealed an ACTH-GH PHA with 2 distinct populations of secreting cells. At 3-year follow-up, the patient showed stable clinical remission and was no longer receiving hormonal replacement therapy.

CONCLUSIONS

This is an additional case to the 20 previously reported cases of ACTH-GH PHA. Awareness of this relatively rare entity is clinically relevant. The cytogenesis of ACTH-GH PHA remains a matter of debate, and several hypotheses have been postulated.

The role of galectin-3 in the tumorigenesis and progression of pituitary tumors

Galectin-3 (Gal-3), a β-galactoside-binding protein, has been implicated in cell proliferation, cell adhesion, and the progression and metastasis of various types of cancer. The present study investigated the involvement of Gal-3 in the tumorigenesis and progression of pituitary tumors using three rat pituitary tumor cell lines. Following transfection with Gal-3 expression and interference vectors, the impact of Gal-3 on proliferation, apoptosis and migration of pituitary tumor cells was been investigated. Meanwhile, BCL2 associated X, apoptosis regulator (Bax), caspase-3 and matrix metalloproteinase 7 (MMP7) protein expression levels were analyzed by western blotting. The results of the present study revealed that Gal-3 expression in GH3 and GH4C1 cells was higher than in RC-4B/C cells. Furthermore, Gal-3 was demonstrated to promote the proliferation and migration of GH3 and GH4C1 cells, and inhibit cell apoptosis. Caspase-3 and MMP7 protein expression was also increased by Gal-3, while Bax expression was decreased. These results suggested that Gal-3 serves an important function in the tumorigenesis and development of pituitary tumors, and it may be a useful target for the treatment of pituitary tumors in the future.

The role of MMP-1 and FGFR4-R388 gene polymorphisms in pituitary adenoma

Background.

The pathogenesis of pituitary adenoma (PA) is complex and poorly understood. It is thought that PA has a multifactorial aetiology; genetic factors also have an impact on PA development. Since MMP1 and FGFR4 genes play an important role in tumour growth, differentiation and progression, we decided to determine if the frequency of the genotypes of MMP-1 and FGFR4-R388 polymorphisms influence the development of PA.

Materials and methods.

The study enrolled n = 100 patients with PA and n = 200 healthy controls (reference group). The genotyping tests of MMP-1 and FGFR4-R388 were carried out using the real-time polymerase chain reaction (PCR) method.

Results.

The polymorphism in the MMP-1 gene 1G/1G genotype was more frequent in the group of invasive PA than in the control group: 28.6% vs. 16.5%, p = 0.044. The 1G/2G genotype was more frequent in females of the control group compared to PA group females: 50.3% vs. 30.8%, p = 0.011. The polymorphism in the MMP-1 gene 1G/1G genotype was more frequent in the active PA group than in the control group: 28.4% vs. 16.5%, p = 0.044. FGFR4-R388 did not play any predominant role in PA development.

Conclusion.

The MMP-1 gene 1G/1G may play a role in invasive and active PA development.

MicroRNA-143 shows tumor suppressive effects through inhibition of oncogenic K-Ras in pituitary tumor

MicroRNAs (miRNAs) are a class of small non-coding RNA molecules, about 21-25 nucleotides in length. Accumulating evidence demonstrated that dysregulation or dysfunction of miRNAs are involved in various diseases, including cancer. MiR-143, recently has been reported to function as an important tumor suppressor in prostate cancer, pancreatic ductal adenocarcinoma and other kinds of cancers, but rarely systematically studied in pituitary tumor. In the present study, we firstly found that miR-143 was significantly down-regulated in pituitary tumor tissues and cell lines (GH3 and MMQ). Then, subsequent studies revealed that miR-143 inhibits cell proliferation and promotes apoptosis in both GH3 and MMQ cells. In addition, K-Ras, one of the most important oncogenes involved in many kinds of cancers, was found to be suppressed by miR-143 in pituitary tumor. Furthermore, overexpression of K-Ras greatly reversed the suppressive effect of miR-143 on pituitary tumor cells. In summary, our study demonstrated that miR-143 functions as a tumor suppressor and directly targets K-Ras in human pituitary tumor.

Increased expression of the microRNA 106b~25 cluster and its host gene MCM7 in corticotroph pituitary adenomas is associated with tumor invasion and Crooke's cell morphology

PURPOSE

MCM7 (minichromosome maintenance complex component 7), a DNA replication licensing factor, is a host gene for the oncogenic miR-106b~25 cluster. It has been recently revealed as a relevant prognostic biomarker in a variety of cancers, including pituitary adenomas. The purpose of this study was to assess whether miR-106b~25 and MCM7 levels correlate with tumor invasiveness in a cohort of ACTH-immunopositive adenomas.

METHODS

Tissue samples were obtained intraoperatively from 25 patients with pituitary adenoma. Tumor invasiveness was assessed according to the Knosp grading scale. MCM7, Ki-67 and TP53 levels were assessed by immunohistochemical staining, while the expression of miR-106b-5p, miR-93-5p, miR-93-3p and miR-25-3p were measured using quantitative real-time PCR performed on RNA isolated from FFPE tissues.

RESULTS

We have found a significant increase in MCM7 and Ki-67 labeling indices in invasive ACTHomas. Moreover, MCM7 was ubiquitously overexpressed in Crooke's cell adenomas. The expression of miR-93-5p was significantly elevated in invasive compared to noninvasive tumors. In addition, all four microRNAs from the miR-106b~25 cluster displayed marked upregulation in Crooke's cell adenomas. Remarkably, MCM7 and miR-106b-5p both strongly correlated with Knosp grade. A combination of MCM7 LI and miR-106b~25 cluster expression was able to accurately differentiate invasive from noninvasive tumors and had a significant discriminatory ability to predict postoperative tumor recurrence/progression.

CONCLUSIONS

miR-106b~25 and its host gene MCM7 are potential novel biomarkers for invasive ACTH-immunopositive pituitary adenomas. Additionally, they are both significantly upregulated in rare Crooke's cell adenomas and might therefore contribute to their aggressive phenotype.

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.

Selective molecular biomarkers to predict biologic behavior in pituitary tumors

To date, several cell proliferation markers, apoptosis, vascular markers, oncogenes, tumor suppressor genes, cell cycle mediators, microRNA (miRNAs), and long noncoding RNAs (lncRNAs) have been identified to be involved in the tumorigenesis, migration, proliferation and invasiveness of pituitary adenomas. There are still no reliable morphologic markers predictive of pituitary adenoma recurrence. Recent scientific research introduced new techniques to enable us to attain new information on the genesis and biologic behavior of pituitary adenomas. Areas covered: This review covers selected, compelling and cumulative information in regards to TACSTD family (EpCAM, TROP2), neuropilin (NRP-1), oncogene-induced senescence (OIS), fascins (FSCN1), invasion-associated genes (CLDN7, CNTNAP2, ITGA6, JAM3, PTPRC and CTNNA1) EZH2, and ENC1 genes and endocan. Expert commentary: Ongoing research provides clinicians, surgeons and researchers with new information not only on diverse pathways in tumorigenesis but also on the clinical aggressive behavior of pituitary adenomas. Newly developed molecular techniques, bioinformatics and new pharmaceutical drug options are helpful tools to widen the perspectives in our understanding of the complex nature of pituitary tumorigenesis. The discovery of new molecular biomarkers can only be accomplished by continuing to investigate pituitary embryogenesis, histogenesis and tumorigenesis.

Programmed cell senescence: role of IL-6 in the pituitary

IL-6 is a pleiotropic cytokine with multiple pathophysiological functions. As a key factor of the senescence secretome, it can not only promote tumorigenesis and cell proliferation but also exert tumor suppressive functions, depending on the cellular context. IL-6, as do other cytokines, plays important roles in the function, growth and neuroendocrine responses of the anterior pituitary gland. The multiple actions of IL-6 on normal and adenomatous pituitary function, cell proliferation, angiogenesis and extracellular matrix remodeling indicate its importance in the regulation of the anterior pituitary. Pituitary tumors are mostly benign adenomas with low mitotic index and rarely became malignant. Premature senescence occurs in slow-growing benign tumors, like pituitary adenomas. The dual role of IL-6 in senescence and tumorigenesis is well represented in pituitary tumor development, as it has been demonstrated that effects of paracrine IL-6 may allow initial pituitary cell growth, whereas autocrine IL-6 in the same tumor triggers senescence and restrains aggressive growth and malignant transformation. IL-6 is instrumental in promotion and maintenance of the senescence program in pituitary adenomas.

Progress in Endocrine Neoplasia

Most endocrine tumors are benign, and afflicted patients usually seek medical advice because of symptoms caused by too much, or too little, native hormone secretion or the impingement of their tumor on a vital structure. Malignant endocrine tumors represent a more serious problem, and patient cure often depends on early diagnosis and treatment. The recent development of novel molecular therapeutics holds great promise for the treatment of patients with locally advanced or metastatic endocrine cancer. In this CCR Focus, expert clinical investigators describe the molecular characteristics of various endocrine tumors and discuss the current status of diagnosis and treatment. Clin Cancer Res; 22(20); 4981-8. ©2016 AACR See all articles in this CCR Focus section, "Endocrine Cancers Revising Paradigms".

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.

Molecular markers in pituitary tumors

PURPOSE OF REVIEW

This review summarizes our current understanding of the mechanisms and factors involved in pituitary tumorigenesis. It provides a comprehensive review on the role of genetic mutations, epigenetics, oncogenes, tumor suppressor genes, cell cycle deregulation, and highlights recent findings of altered micro-RNA and long noncoding RNA expression in pituitary tumors.

RECENT FINDINGS

This article provides a concise summary of our knowledge regarding oncogenes, tumor suppressor genes, and cell cycle deregulation in pituitary tumors. Additionally, it highlights new findings in epigenetics and altered micro-RNA and long noncoding RNA expression in pituitary tumors.

SUMMARY

Improved understanding of the mechanism(s) and candidates implicated in pituitary tumorigenesis may result in the identification of new therapeutic targets in pituitary tumors.

MicroRNA-106b promotes pituitary tumor cell proliferation and invasion through PI3K/AKT signaling pathway by targeting PTEN

The purpose of this study was to investigate the expression of microRNA-106b (miR-106b) and phosphatase and tensin homolog deleted on chromosome 10 (PTEN) in pituitary tumor and to confirm whether miR-106b promotes proliferation and invasion of pituitary tumor cells through the PI3K/AKT signaling pathway by targeted regulation of PTEN expression, and thereby to find new targets for the treatment of pituitary tumor. Fifty-five cases of pituitary tumor tissue samples were collected, including 29 cases of invasive pituitary tumor, non-invasive 26 cases, and 8 normal pituitaries. The expression level of miR-106b in pituitary tumor tissue was detected by quantitative real-time PCR, and the expression of PTEN protein was detected by immunohistochemistry. PTEN 3'-untranslated region (UTR) luciferase vector was constructed, and dual-luciferase reporter gene assay was employed to examine the effect of miR-106b on PTEN 3'-UTR luciferase activity. AtT-20 cells were transfected with miR-106b mimics, miR-106b inhibitor, PTEN expression plasmid, and miR-106b mimics + PTEN expression plasmid respectively, and the changes in cellular proliferation and invasion were observed via MTT method and transwell assay respectively. PTEN messenger RNA (mRNA) expression was determined by quantitative real-time PCR, and western blotting was performed to detect the expression of PTEN, PI3K, AKT, and pAKT. miR-106b showed up-regulation in invasive pituitary tumor tissue: the expression level was significantly up-regulated compared with normal tissues and the non-invasive pituitary tumor tissue (P < 0.05). The positive rate of PTEN protein expression in invasive pituitary tumor tissues was significantly lower than in normal and non-invasive tissues (P < 0.01). Dual-luciferase reporter gene assay showed that miR-106b could bind to the 3'-UTR of PTEN specifically and significantly inhibited the luciferase activity, cutting the 46 % (P < 0.01). Down-regulation of miR-106b or up-regulation of PTEN could suppress cell proliferation and invasion of AtT-20 cells, and PTEN expression plasmid could partially simulate the function of miR-106b. Expression of PTEN mRNA and protein decreased significantly in AtT-20 cells overexpressing miR-106b. The expression levels of PI3K and p-AKT were significantly inhibited by miR-106b inhibitor and increased by miR-106b mimics. The expression of miR-106b showed up-regulation in pituitary tumor tissues, while the protein expression of PTEN presented opposite results. The findings of this study further demonstrated that miR-106b as an oncogene regulated the pituitary tumor cell proliferation and invasion in vitro by directly targeting PTEN through the PI3K/AKT signaling pathway. Our study suggests that miR-106b and PTEN are likely to serve as potential diagnostic biomarkers or therapeutic targets for pituitary tumor treatment in the future.

Isolated double adrenocorticotropic hormone-secreting pituitary adenomas: A case report and review of the literature

Only a few cases of double or multiple pituitary adenomas have previously been reported in the literature; however, isolated double adrenocorticotropic hormone (ACTH)-secreting pituitary adenomas are even more rare. The present study reports a rare case of a 50-year-old female patient who presented with typical clinical features of Cushing's disease and was diagnosed with isolated double ACTH-secreting pituitary adenomas. Endocrinological examination revealed an ACTH-producing pituitary adenoma, and preoperative magnetic resonance imaging (MRI) demonstrated a microadenoma with a lower intensity on the right side of the pituitary gland. The patient underwent endoscopic endonasal transsphenoidal surgery, which revealed another pituitary tumor in the left side of the pituitary gland. The two, clearly separated, pituitary adenomas identified in the same gland were completely resected. Immunohistochemistry and pathology revealed that the clearly separated double pituitary adenomas were positive for ACTH, thyroid-stimulating, growth and prolactin hormones. Postoperatively, the levels of ACTH and cortisol hormone decreased rapidly. The case reported in the present study is considerably rare, due to the presence of a second pituitary adenoma in the same gland, which was not detected by preoperative MRI scan, but was noticed during surgery. Intraoperative evaluation may be important in the identification of double or multiple pituitary adenomas.

Biomarkers of pituitary carcinomas

Pituitary carcinoma is a rare tumor originating from adenohypophyseal cells. Currently, diverse pathogenetic mechanisms, i.e. de novo versus malignant transformation from pituitary adenoma, remain obscure and require further investigation. During the last two decades, scientific research added new horizons not only in regards to general tumor concepts but also in next generation biomarker armamentarium that sheds light on alternate pathways in carcinogenesis. Areas covered: In this review, the impact of apoptotic and proliferative markers, angiogenesis, telomerase activity, H-ras, HIF-1, HER-2/neu, Rb gene, and microRNAs in pathogenetic mechanisms of pituitary carcinomas were revised. Expert commentary: It is becoming increasingly important for the need of standardization of new biomarkers but also for better comprehension of the diverse pathways in tumorigenesis. This can only be accomplished by tapping into the continuously expanding spectrum of new biomarkers.

Use of micro-positron emission tomography with (18)F-fallypride to measure the levels of dopamine receptor-D2 and (18)F-FDG as molecular imaging tracer in the pituitary glands and prolactinomas of Fischer-344 rats

Dopamine receptor-D2 (DRD2) is the most important drug target in prolactinoma. The aim of this current study was to investigate the role of using micro-positron emission tomography (micro-PET) with (18)F-fallypride and (18)F-fluorodeoxyglucose ((18)F-FDG) as molecular imaging tracer in the pituitary glands and prolactinomas of Fischer-344 (F344) rats and detect the difference of the levels of DRD2 in the pituitary glands and prolactinomas of F344 rat prolactinoma models. Female F344 rat prolactinoma models were established by subcutaneous administration of 15 mg 17β-estradiol for 8 weeks. The growth of tumors was monitored by the small-animal magnetic resonance imaging and micro-PET. A series of molecular biological experiments were also performed 4 and 6 weeks after pump implantation. The micro-PET molecular imaging with (18)F-fallypride revealed a decreased expression of DRD2 in F344 rat prolactinoma models, but the micro-PET molecular imaging with (18)F-FDG presented an increased uptake in the prolactinoma compared with the pituitary gland. A decreasing trend of levels of DRD2 in F344 rat prolactinoma models was also detected by molecular biological experiments. From this, we can conclude that micro-PET with (18)F-fallypride and (18)F-FDG can be used to assess tumorigenesis of the prolactinomas in vivo and molecular imaging detection of DRD2 level in prolactinoma may be an indication of treatment effect in the animal experiment.

Pituitary adenomas: historical perspective, surgical management and future directions

Pituitary adenomas are among the most common central nervous system tumors. They represent a diverse group of neoplasms that may or may not secrete hormones based on their cell of origin. Epidemiologic studies have documented the incidence of pituitary adenomas within the general population to be as high as 16.7%. A growing body of work has helped to elucidate the pathogenesis of these tumors. Each subtype has been shown to demonstrate unique cellular changes potentially leading to tumorigenesis. Surgical advancements over several decades have included microsurgery and the employment of the endoscope for surgical resection. These advancements increase the likelihood of gross-total resection and have resulted in decreased patient morbidity.

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.

The role of genetic and epigenetic changes in pituitary tumorigenesis

Pituitary adenomas are one of the most common intracranial tumors. Despite their benign nature, dysregulation of hormone secretion causes systemic metabolic deterioration, resulting in high mortality and an impaired quality of life. Tumorigenic pathogenesis of pituitary adenomas is mainly investigated by performing genetic analyses of somatic mutations in the tumor or germline mutations in patients. Genetically modified mouse models, which develop pituitary adenomas, are also used. Genetic analysis in rare familial pituitary adenomas, including multiple endocrine neoplasia type 1 and type 4, Carney complex, familial isolated pituitary adenomas, and succinate dehydrogenases (SDHs)-mediated paraganglioma syndrome, revealed several causal germline mutations and sporadic somatic mutations in these genes. The analysis of genetically modified mouse models exhibiting pituitary adenomas has revealed the underlying mechanisms, where cell cycle regulatory molecules, tumor suppressors, and growth factor signaling are involved in pituitary tumorigenesis. Furthermore, accumulating evidence suggests that epigenetic changes, including deoxyribonucleic acid (DNA) methylation, histone modification, micro ribonucleic acids (RNAs), and long noncoding RNAs play a pivotal role. The elucidation of precise mechanisms of pituitary tumorigenesis can contribute to the development of novel targeted therapy for pituitary adenomas.

Overexpression of EpCAM and Trop2 in pituitary adenomas

We sought to investigate the expression of EpCAM and Trop2 in Pituitary adenomas (PAs) and study the correlation of protein expression with invasiveness, proliferation, clinical functioning, recurrence/progression, and some other factors. We investigated the expression of EpCAM and Trop2 in 74 samples of PAs by immunohistochemistry and made correlative analysis of protein overexpression with clinicopathological parameters. Follow-up data was analyzed for recurrence/progression with Kaplan-Meier method and Multivariate Cox regression analysis. Immunohistochemistry results showed that overexpression rates of EpCAM and Trop2 were 51/74 (68.9%) and 43/74 (58.1%), respectively. For both EpCAM and Trop2, PAs with invasiveness showed a higher overexpression rate than PAs without invasiveness (PEpCAM = 0.001; PTrop2 = 0.006). Nonfunctional Pituitary adenomas (NFPAs) demonstrated a higher EpCAM overexpression than functional Pituitary adenomas (FPAs) (P = 0.026). Both EpCAM and Trop2 overexpression correlated significantly with expression of proliferation factor Ki-67 (PEpCAM = 0.011; PTrop2 = 0.000), but not with gender and age. Follow-up analysis revealed that Trop2 overexpression was a significantly predictive factor for recurrence/progression by means of Kaplan-Meier method d (P = 0.028) and Multivariate Cox regression analysis (P = 0.025). This study reveals that both EpCAM and Trop2 overexpression in PAs correlate significantly with invasiveness and proliferation. EpCAM presents a potential target for differential diagnosis and immunotherapy for NFPAs. Follow-up analysis shows that Trop2 is a predictive factor for recurrence/progression for PAs.

MiR-132, miR-15a and miR-16 synergistically inhibit pituitary tumor cell proliferation, invasion and migration by targeting Sox5

MiR-132, miR-15a and miR-16 have been implicated in the pathogenesis of many types of cancer, including pituitary tumors. However, the molecular mechanism of these miRNAs in pituitary tumor growth and metastasis is still unclear. Here, we showed that miR-132 and miR-15a/16 were less expressed in pituitary tumor cell lines, as well as in invasive pituitary tumor tissues, compared to non-invasive tumor tissues. We described that overexpression of miR-132 and miR-15a/16 resulted in the suppression of pituitary tumor cell proliferation, migration and invasion, respectively, and also inhibits the expression of proteins involved in Epithelial to Mesenchymal Transition (EMT). Then, we show that these miRNAs synergistically target Sox5 in pituitary tumor. Moreover, we found that Sox5 overexpression partially rescued miR-132, miR-15a and miR-16-mediated inhibition of cell migration, invasion and cell growth. Finally, we confirmed that Sox5 was upregulated in invasive pituitary tumor tissues, compared to non-invasion tissues. In conclusion, our data indicate that miR-132 and miR-15a/16 act as tumor suppressor genes in pituitary tumor by directly targetting Sox5, and imply that these miRNAs have potential as therapeutic targets for invasive pituitary tumor.

Epigenetics of pituitary tumours: an update

PURPOSE OF REVIEW

To review recent advances in our knowledge and understanding of aberrations that target the epigenome in sporadic pituitary adenomas.

RECENT FINDINGS

A more complete understanding of the pituitary epigenome has been facilitated by advances in technologies for exploring the tumour-associated epigenomic landscape, and has revealed aberration to the principle targets of these changes, namely, methylation of CpG dinucleotides, modification of histone tails and the expression of target-specific miRNA. Genome-wide investigations, of sporadic pituitary adenoma, have identified novel methylated genes that in some cases are subtype-specific. Recent studies have also shown that silenced genes may be reactivated through epidrug challenges. Moreover, in experimental settings, wherein enforced expression of specific miRNA has been employed, these have been shown to inhibit pituitary cell proliferation in vitro and in vivo.

SUMMARY

Candidate gene and genome-wide studies reveal frequent epigenetic changes in pituitary adenomas. Aberrations, concurrent with their impact on functional end-points, may display subtype specificity, whereas others appear to be independent of adenoma subtype. Changes to the epigenomic landscape, and apparent as CpG island methylation and/or as histone tail modifications, show sensitivity to epidrug-induced re-expression that concomitantly impacts on cell proliferation. Similarly, enforced expression of silenced miRNA in model systems is also associated with similar end-points. Collectively, emerging data show that these types of manipulation, alone or in combination with a more conventional therapeutic option, offer new avenues for the medical management of these tumours.