Low aryl hydrocarbon receptor-interacting protein expression is a better marker of invasiveness in somatotropinomas than Ki-67 and p53

Genetic diagnosis in acromegaly and gigantism: From research to clinical practice

It is usually considered that only 5% of all pituitary neuroendocrine tumours are due to inheritable causes. Since this estimate was reported, however, multiple genetic defects driving syndromic and nonsyndromic somatotrophinomas have been unveiled. This heterogeneous genetic background results in overlapping phenotypes of GH excess. Genetic tests should be part of the approach to patients with acromegaly and gigantism because they can refine the clinical diagnoses, opening the possibility to tailor the clinical conduct to each patient. Even more, genetic testing and clinical screening of at-risk individuals have a positive impact on disease outcomes, by allowing for the timely detection and treatment of somatotrophinomas at early stages. Future research should focus on determining the actual frequency of novel genetic drivers of somatotrophinomas in the general population, developing up-to-date disease-specific multi-gene panels for clinical use, and finding strategies to improve access to modern genetic testing worldwide.

The aryl hydrocarbon receptor-interacting protein in cancer and immunity: Beyond a chaperone protein for the dioxin receptor

The aryl hydrocarbon receptor (AhR)-interacting protein (AIP) is a ubiquitously expressed, immunophilin-like protein best known for its role as a co-chaperone in the AhR-AIP-Hsp90 cytoplasmic complex. In addition to regulating AhR and the xenobiotic response, AIP has been linked to various aspects of cancer and immunity that will be the focus of this review article. Loss-of-function AIP mutations are associated with pituitary adenomas, suggesting that AIP acts as a tumor suppressor in the pituitary gland. However, the tumor suppressor mechanisms of AIP remain unclear, and AIP can exert oncogenic functions in other tissues. While global deletion of AIP in mice yields embryonically lethal cardiac malformations, heterozygote, and tissue-specific conditional AIP knockout mice have revealed various physiological roles of AIP. Emerging studies have established the regulatory roles of AIP in both innate and adaptive immunity. AIP interacts with and inhibits the nuclear translocation of the transcription factor IRF7 to inhibit type I interferon production. AIP also interacts with the CARMA1-BCL10-MALT1 complex in T cells to enhance IKK/NF-κB signaling and T cell activation. Taken together, AIP has diverse functions that vary considerably depending on the client protein, the tissue, and the species.

Clinical and Molecular Characteristics of Gonadotroph Pituitary Tumors According to the WHO Classification

Since 2017, hormone-negative pituitary neuroendocrine tumors expressing the steroidogenic factor SF1 have been recognized as gonadotroph tumors (GnPT) but have been poorly studied. To further characterize their bio-clinical spectrum, 54 GnPT defined by immunostaining for FSH and/or LH (group 1, n = 41) or SF1 only (group 2, n = 13) were compared and studied for SF1, βFSH, βLH, CCNA2, CCNB1, CCND1, caspase 3, D2R, and AIP gene expression by qRT-PCR. Immunohistochemistry for AIP and/or D2R was performed in representative cases. Overall, patients were significantly younger in group 1 (P = 0.040 vs group 2), with a similar trend excluding recurrent cases (P = 0.078), and no significant difference in gender, tumor size, invasion or Ki67. SF1 expression was similar in both groups but negatively correlated with the patient's age (P = 0.013) and positively correlated with βLH (P < 0.001) expression. Beta-FSH and AIP were significantly higher in group 1 (P = 0.042 and P = 0.024, respectively). Ki67 was unrelated to gonadotroph markers but positively correlated with CCNB1 (P = 0.001) and negatively correlated with CCND1 (P = 0.008). D2R and AIP were strongly correlated with each other (P < 0.001), and both positively correlated with SF1, βFSH, βLH, and CCND1. AIP immunopositivity was frequently observed in both groups, with a similar median score, and unrelated to Ki67. D2R immunostaining was best detected with a polyclonal antibody and mostly cytoplasmic. This study indicates that hormone-negative GnPT tend to occur in older patients but do not significantly differ from other GnPT in terms of invasion or proliferation. It also points out the current limits of D2R immunostaining in such tumors.

Aggressive PitNETs and Potential Target Therapies: A Systematic Review of Molecular and Genetic Pathways

Recently, advances in molecular biology and bioinformatics have allowed a more thorough understanding of tumorigenesis in aggressive PitNETs (pituitary neuroendocrine tumors) through the identification of specific essential genes, crucial molecular pathways, regulators, and effects of the tumoral microenvironment. Target therapies have been developed to cure oncology patients refractory to traditional treatments, introducing the concept of precision medicine. Preliminary data on PitNETs are derived from preclinical studies conducted on cell cultures, animal models, and a few case reports or small case series. This study comprehensively reviews the principal pathways involved in aggressive PitNETs, describing the potential target therapies. A search was conducted on Pubmed, Scopus, and Web of Science for English papers published between 1 January 2004, and 15 June 2023. 254 were selected, and the topics related to aggressive PitNETs were recorded and discussed in detail: epigenetic aspects, membrane proteins and receptors, metalloprotease, molecular pathways, PPRK, and the immune microenvironment. A comprehensive comprehension of the molecular mechanisms linked to PitNETs' aggressiveness and invasiveness is crucial. Despite promising preliminary findings, additional research and clinical trials are necessary to confirm the indications and effectiveness of target therapies for PitNETs.

Pituitary Tumorigenesis-Implications for Management

Pituitary neuroendocrine tumors (PitNETs), the third most common intracranial tumor, are mostly benign. However, some of them may display a more aggressive behavior, invading into the surrounding structures. While they may rarely metastasize, they may resist different treatment modalities. Several major advances in molecular biology in the past few years led to the discovery of the possible mechanisms involved in pituitary tumorigenesis with a possible therapeutic implication. The mutations in the different proteins involved in the Gsa/protein kinase A/c AMP signaling pathway are well-known and are responsible for many PitNETS, such as somatotropinomas and, in the context of syndromes, as the McCune-Albright syndrome, Carney complex, familiar isolated pituitary adenoma (FIPA), and X-linked acrogigantism (XLAG). The other pathways involved are the MAPK/ERK, PI3K/Akt, Wnt, and the most recently studied HIPPO pathways. Moreover, the mutations in several other tumor suppressor genes, such as menin and CDKN1B, are responsible for the MEN1 and MEN4 syndromes and succinate dehydrogenase (SDHx) in the context of the 3PAs syndrome. Furthermore, the pituitary stem cells and miRNAs hold an essential role in pituitary tumorigenesis and may represent new molecular targets for their diagnosis and treatment. This review aims to summarize the different cell signaling pathways and genes involved in pituitary tumorigenesis in an attempt to clarify their implications for diagnosis and management.

The Spectrum of Familial Pituitary Neuroendocrine Tumors

Hereditary pituitary tumorigenesis is seen in a relatively small proportion (around 5%) of patients with pituitary neuroendocrine tumors (PitNETs). The aim of the current review is to describe the main clinical and molecular features of such pituitary tumors associated with hereditary or familial characteristics, many of which have now been genetically identified. The genetic patterns of inheritance are classified into isolated familial PitNETs and the syndromic tumors. In general, the established genetic causes of familial tumorigenesis tend to present at a younger age, often pursue a more aggressive course, and are more frequently associated with growth hormone hypersecretion compared to sporadic tumors. The mostly studied molecular pathways implicated are the protein kinase A and phosphatidyl-inositol pathways, which are in the main related to mutations in the syndromes of familial isolated pituitary adenoma (FIPA), Carney complex syndrome, and X-linked acrogigantism. Another well-documented mechanism consists of the regulation of p27 or p21 proteins, with further acceleration of the pituitary cell cycle through the check points G1/S and M/G1, mostly documented in multiple endocrine neoplasia type 4. In conclusion, PitNETs may occur in relation to well-established familial germline mutations which may determine the clinical phenotype and the response to treatment, and may require family screening.

AIP gene germline variants in adult Polish patients with apparently sporadic pituitary macroadenomas

INTRODUCTION

Up to 5% of all pituitary tumors are hereditary e.g. due to MEN1 or aryl hydrocarbon receptor-interacting protein (AIP) genes mutations.

OBJECTIVES

The study was aimed at the assessment of the frequency and characteristics of AIP-mutation related tumors in patients with apparently sporadic pituitary macroadenomas in the Polish population.

MATERIALS AND METHODS

The study included 131 patients (57 males, 74 females; median age 42 years) diagnosed with pituitary macroadenomas, and with a negative family history of familial isolated pituitary adenoma (FIPA) or multiple endocrine neoplasia type 1 (MEN1) syndromes. Sanger sequencing was used for the assessment of AIP gene variants. The study was approved by the Ethics Board of JUMC.

RESULTS

AIP variants were identified in five of the 131 included subjects (3.8%): one diagnosed with Cushing's disease, two with acromegaly, and two with non-secreting adenomas. Patients harboring hereditary AIP gene alterations did not differ from the rest of the study group in median age at diagnosis (41.0 vs. 42.5 years, P=0.8), median largest tumor diameter (25 vs. 24 mm, P=0.6), gender distribution (60.0% vs. 56.3% females, P=0.8), secreting tumor frequency (60.0% vs. 67.5%, P=0.7), or acromegaly diagnosis frequency (40.0% vs.37.3%, P=0.9).

CONCLUSIONS

In our series of apparently sporadic pituitary macroadenomas, AIP gene variant carriers did not differ substantially from patients with negative genetic testing. A risk factor-centred approach to AIP genetic screening may result in missing germline variants. Considering the clinical impact of such genetic variants and their relatively low penetrance, it is, however, doubtful if general genetic screening benefits the whole cohort of pituitary macroadenoma patients and their families.

Transcription factor GTF2B regulates AIP protein expression in growth hormone-secreting pituitary adenomas and influences tumor phenotypes

BACKGROUND

Clinically, the low expression of wild-type aryl hydrocarbon receptor-interacting protein (AIP) in patients with sporadic growth hormone (GH)-secreting pituitary adenoma (GHPA) is associated with a more aggressive phenotype. However, the mechanism by which AIP expression is regulated in GHPA remains unclear. Herein, we investigated a transcription factor that regulates AIP expression and explored its role in tumor phenotypes.

METHODS

General transcription factor IIB (GTF2B) was predicted by several bioinformatic tools to regulate AIP expression transcriptionally. Regulation by GTF2B was evaluated using chromatin immunoprecipitation (ChIP), reverse transcription PCR, luciferase reporter, and western blot experiments in SH-SY5Y cells. Furthermore, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay, transwell invasive assay, ELISA, western blot, immunohistochemical staining, and terminal deoxynucleotidyl transferase dUTP nick end labeling were performed to investigate the effects of GTF2B and AIP on tumor cell proliferation, apoptosis, growth hormone secretion, and invasiveness in GH3 cells and mouse xenograft models. Moreover, correlations between GTF2B and AIP expression were explored in GHPA cases.

RESULTS

ChIP and luciferase reporter studies demonstrated that the regulation of AIP expression by GTF2B was dependent on the intergenic-5' untranslated region element of AIP and the initial residual S65 of GTF2B. In vitro and in vivo experiments indicated that GTF2B regulated AIP expression to impact GHPA phenotype; this was confirmed by data from 33 GHPA cases.

CONCLUSIONS

We determined the regulation by GTF2B of AIP transcription in GHPA and its impact on tumor phenotype. Our findings suggest that GTF2B may be a potential therapeutic target for GHPA with low AIP expression.

Aryl hydrocarbon receptor interacting protein (AIP) significantly influences prognosis of pancreatic carcinoma

INTRODUCTION

Aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor. Aryl hydrocarbon receptor interacting protein (AIP) in one of AHR ligands. The aim of this study is to analyze the prognostic influence of AIP in pancreatic carcinoma.

MATERIAL AND METHODS

Retrospective case series with immunohistochemical analysis of AIP. We have estimated a multivariate Cox's model for the outcome (progression free and overall survival).

RESULTS

204 patients were included in the study. As expected prognosis was poor and 67.8% died of disease. As for AIP 9.8% of the cases showed nuclear staining of the epithelial tumor cells and 59.4% a cytoplasmic one. Stroma was stained in 53.1% of the cases. Univariate survival analysis revealed a significantly worse prognosis of patients with cytoplasmic AIP expression (stroma and epithelium), but nuclear expression was associated to a better prognosis. In the multivariate analysis stromal AIP expression was an independent prognosticator of progression free survival, together with pT stage, histological grade and history of diabetes.

DISCUSSION

AIP Is a conserved cochaperone protein binding to many proteins. AIP has been proposed as a potential tumor suppressor gene. To date, no study has analyzed the immunohistochemical expression of AIP in pancreatic carcinoma. Our results indicate that both epithelial and stromal cytoplasmic expression of AIP is associated to bad prognosis, while nuclear translocation seems to improve prognosis.

CONCLUSION

Although we must deepen into the complex signaling pathways underlying this potential association, our results open a way to inhibiting AHR as a potential target against pancreatic carcinoma.

The impact of SST2 trafficking and signaling in the treatment of pancreatic neuroendocrine tumors

Pancreatic neuroendocrine tumors (Pan-NETs), are heterogeneous neoplasms, whose incidence and prevalence are increasing worldwide. Pan-NETs are characterized by the expression of somatostatin receptors (SSTs). In particular, SST2 is the most widely distributed SST in NETs, thus representing the main molecular target for somatostatin analogs (SSAs). SSAs are currently approved for the treatment of well-differentiated NETs, and radionuclide-labeled SSAs are used for diagnostic and treatment purposes. SSAs, by binding to SSTs, have been shown to inhibit hormone secretion and thus provide control of hypersecretion symptoms, when present, and inhibit tumor proliferation. After SSA binding to SST2, the fate of the receptor is determined by trafficking mechanisms, crucial for the response to endogenous or pharmacological ligands. Although SST2 acts mostly through G protein-dependent mechanism, receptor-ligand complex endocytosis and receptor trafficking further regulate its function. SST2 mediates the decrease of hormone secretion via a G protein-dependent mechanism, culminating with the inhibition of adenylyl cyclase and calcium channels; it also inhibits cell proliferation and increases apoptosis through the modulation of protein tyrosine phosphatases. Moreover, SST2 inhibits angiogenesis and cell migration. In this respect, the cross-talk between SST2 and its interacting proteins, including Filamin A (FLNA) and aryl hydrocarbon receptor-interacting protein (AIP), plays a crucial role for SST2 signaling and responsiveness to SSAs. This review will focus on recent studies from our and other groups that have investigated the trafficking and signaling of SST2 in Pan-NETs, in order to provide insights into the mechanisms underlying tumor responsiveness to pharmacological treatments.

C, Torres L, Quintero G. Proteína moduladora de la actividad del receptor de aril hidrocarburos (AIP): genética, bioquímica e impacto clínico

El gen AIP (proteína moduladora de la actividad del receptor de aril hidrocarburos) se localiza en la región 11q13.2 y codifica para una proteína de 330 aminoácidos que interactúa con el factor de transcripción AhR (receptor para aril hidrocarburos). Las mutaciones en este gen se han asociado con adenomas pituitarios aislados de tipo familiar (APAF). Se caracterizan por una presentación temprana (alrededor de 20 años), por lo regular producen hormona de crecimiento y/o prolactina, tienen un comportamiento clínico agresivo y poca respuesta a análogos de somatostatina.

Genetics of Acromegaly and Gigantism

Growth hormone (GH)-secreting pituitary tumours represent the most genetically determined pituitary tumour type. This is true both for germline and somatic mutations. Germline mutations occur in several known genes (AIP, PRKAR1A, GPR101, GNAS, MEN1, CDKN1B, SDHx, MAX) as well as familial cases with currently unknown genes, while somatic mutations in GNAS are present in up to 40% of tumours. If the disease starts before the fusion of the epiphysis, then accelerated growth and increased final height, or gigantism, can develop, where a genetic background can be identified in half of the cases. Hereditary GH-secreting pituitary adenoma (PA) can manifest as isolated tumours, familial isolated pituitary adenoma (FIPA) including cases with AIP mutations or GPR101 duplications (X-linked acrogigantism, XLAG) or can be a part of systemic diseases like multiple endocrine neoplasia type 1 or type 4, McCune-Albright syndrome, Carney complex or phaeochromocytoma/paraganglioma-pituitary adenoma association. Family history and a search for associated syndromic manifestations can help to draw attention to genetic causes; many of these are now tested as part of gene panels. Identifying genetic mutations allows appropriate screening of associated comorbidities as well as finding affected family members before the clinical manifestation of the disease. This review focuses on germline and somatic mutations predisposing to acromegaly and gigantism.

Ki67 in endocrine neoplasms: to count or not to count, this is the question! A systematic review from the English language literature

BACKGROUND

Endocrine neoplasms are generally slow-growing tumors that can show hormonal activity and give metastases. In most cases they are benign and clearly malignant forms are easy to diagnose. However, borderline forms may occur and be, for the pathologists, very difficult to classify. In these cases, there is a strong need to identify factors that may aid. Official classification systems for endocrine neoplasms are based on the evaluation of proliferation and, in most cases, they rely on mitotic count. In support, the study of Ki67 is carried out which, however, has not yet been included in any official classification system, except for neuroendocrine neoplasms of the gastro-entero-pancreatic tract.

PURPOSE

The aim of the present study was to investigate the proven or unproven role of Ki67 in endocrine neoplasms, in different districts, in order to bring to light the substantial differences, in terms of proliferation, existing between neoplasms so similar, but at the same time, so different.

METHODS

A thorough search of English language literature was performed, looking for articles concerning Ki67 in five endocrine neoplasms (pituitary adenomas, thyroid neoplasms, adrenocortical neoplasms, pheochromocytomas and paragangliomas).

RESULTS

From 2170, 236 articles were selected and it was seen that the endocrine neoplasm in which Ki67 was most studied was the pituitary, where it still shows a controversial role. In other neoplasms different roles were identified.

CONCLUSION

The pathologist should be aware of the contribution that this proliferative marker can give to the diagnosis and, sometimes, to the therapy selection, for the clinician.

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.

Update on the Genetics of Pituitary Tumors

Pituitary adenomas are common intracranial neoplasms, with diverse phenotypes. Most of these tumors occur sporadically and are not part of genetic disorders. Over the last decades numerous genetic studies have led to identification of somatic and germline mutations associated with pituitary tumors, which has advanced the understanding of pituitary tumorigenesis. Exploring the genetic background of pituitary neuroendocrine tumors can lead to early diagnosis associated with better outcomes, and their molecular mechanisms should lead to novel targeted therapies even for sporadic tumors. This article summarizes the genes and the syndromes associated with pituitary tumors.

SNPs of miR-23b, miR-107 and HMGA2 and their Relations with the Response to Medical Treatment in Acromegaly Patients

INTRODUCTION

Acromegaly is a chronic disease of increased growth hormone (GH) secretion and elevated insulin-like growth factor-I (IGF-I) levels induced by a pituitary adenoma. HMGA2 (high mobility group A2) and AIP (aryl hydrocarbon receptor-interacting protein) expression levels are related to GH-secreting adenomas, and also a response to Somatostatin Analogs (SSAs). We studied SNPs in miR-107 and miR-23b that related with AIP and HMGA2 genes respectively and control their expression, and also SNP in the 3'UTR of HMGA2 gene. Our aim was to investigate genotype distributions of the studied SNPs, as well as the possible relationship between disease and/or response to SSAs treatment in patients with acromegaly.

MATERIAL AND METHODS

Genotypes were determined by qRT-PCR method from DNA materials obtained blood samples of acromegaly patients (141) and healthy individuals (99). The genotype distributions of patients and healthy groups, as well as the relationship between the clinical data of the disease and genotypes were statistically compared.

RESULTS

In acromegaly patients with T-allele, p53 expression (p=0.049) was significantly higher. In patients with CT+TT genotype and T-allele who were responder to SSA-treatment Ki-67 index (respectively p=0.019, p=0.020 respectively) was higher. We did not observe the genotypes for miR-23b and miR-107 polymorphisms in the patients and control group of Turkish population.

CONCLUSION

The genetic variations of the miRNAs genes related with HMGA2 and AIP genes were not seen in our study. Although there is no relationship between HMGA2-rs1351394 polymorphism and acromegaly disease, T allele was associated with some clinical features related to adenoma in patients with acromegaly.

Potential markers of disease behavior in acromegaly and gigantism

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

Chaperones, somatotroph tumors and the cyclic AMP (cAMP)-dependent protein kinase (PKA) pathway

The cAMP-PKA pathway plays an essential role in the pituitary gland, governing cell differentiation and survival, and maintenance of endocrine function. Somatotroph growth hormone transcription and release as well as cell proliferation are regulated by the cAMP-PKA pathway; cAMP-PKA pathway abnormalities are frequently detected in sporadic as well as in hereditary somatotroph tumors and more rarely in other pituitary tumors. Inactivating variants of the aryl hydrocarbon receptor-interacting protein (AIP)-coding gene are the genetic cause of a subset of familial isolated pituitary adenomas (FIPA). Multiple functional links between the co-chaperone AIP and the cAMP-PKA pathway have been described. This review explores the role of chaperones including AIP in normal pituitary function as well as in somatotroph tumors, and their interaction with the cAMP-PKA pathway.

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.

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.

AIP-mutated acromegaly resistant to first-generation somatostatin analogs: long-term control with pasireotide LAR in two patients

Acromegaly is a rare disease due to chronic excess growth hormone (GH) and IGF-1. Aryl hydrocarbon receptor interacting protein (AIP) mutations are associated with an aggressive, inheritable form of acromegaly that responds poorly to SST2-specific somatostatin analogs (SSA). The role of pasireotide, an SSA with affinity for multiple SSTs, in patients with AIP mutations has not been reported. We studied two AIP mutation positive acromegaly patients with early-onset, invasive macroadenomas and inoperable residues after neurosurgery. Patient 1 came from a FIPA kindred and had uncontrolled GH/IGF-1 throughout 10 years of octreotide/lanreotide treatment. When switched to pasireotide LAR, he rapidly experienced hormonal control which was associated with marked regression of his tumor residue. Pasireotide LAR was stopped after >10 years due to low IGF-1 and he maintained hormonal control without tumor regrowth for >18 months off pasireotide LAR. Patient 2 had a pituitary adenoma diagnosed when aged 17 that was not cured by surgery. Chronic pasireotide LAR therapy produced hormonal control and marked tumor shrinkage but control was lost when switched to octreotide. Tumor immunohistochemistry showed absent AIP and SST2 staining and positive SST5. Her AIP mutation positive sister developed a 2.5 cm follicular thyroid carcinoma aged 21 with tumoral loss of heterozygosity at the AIP locus and absent AIP staining. Patients 1 and 2 required multi-modal therapy to control diabetes. On stopping pasireotide LAR after >10 years of treatment, Patient 1's glucose metabolism returned to baseline levels. Long-term pasireotide LAR therapy can be beneficial in some AIP mutation positive acromegaly patients that are resistant to first-generation SSA.

AIP and MEN1 mutations and AIP immunohistochemistry in pituitary adenomas in a tertiary referral center

BACKGROUND

Pituitary adenomas have a high disease burden due to tumor growth/invasion and disordered hormonal secretion. Germline mutations in genes such as MEN1 and AIP are associated with early onset of aggressive pituitary adenomas that can be resistant to medical therapy.

AIMS

We performed a retrospective screening study using published risk criteria to assess the frequency of AIP and MEN1 mutations in pituitary adenoma patients in a tertiary referral center.

METHODS

Pituitary adenoma patients with pediatric/adolescent onset, macroadenomas occurring ≤30 years of age, familial isolated pituitary adenoma (FIPA) kindreds and acromegaly or prolactinoma cases that were uncontrolled by medical therapy were studied genetically. We also assessed whether immunohistochemical staining for AIP (AIP-IHC) in somatotropinomas was associated with somatostatin analogs (SSA) response.

RESULTS

Fifty-five patients met the study criteria and underwent genetic screening for AIP/MEN1 mutations. No mutations were identified and large deletions/duplications were ruled out using MLPA. In a cohort of sporadic somatotropinomas, low AIP-IHC tumors were significantly larger (P = 0.002) and were more frequently sparsely granulated (P = 0.046) than high AIP-IHC tumors. No significant relationship between AIP-IHC and SSA responses was seen.

CONCLUSIONS

Germline mutations in AIP/MEN1 in pituitary adenoma patients are rare and the use of general risk criteria did not identify cases in a large tertiary-referral setting. In acromegaly, low AIP-IHC was related to larger tumor size and more frequent sparsely granulated subtype but no relationship with SSA responsiveness was seen. The genetics of pituitary adenomas remains largely unexplained and AIP screening criteria could be significantly refined to focus on large, aggressive tumors in young patients.

The causes and consequences of pituitary gigantism

In the general population, height is determined by a complex interplay between genetic and environmental factors. Pituitary gigantism is a rare but very important subgroup of patients with excessive height, as it has an identifiable and clinically treatable cause. The disease is caused by chronic growth hormone and insulin-like growth factor 1 secretion from a pituitary somatotrope adenoma that forms before the closure of the epiphyses. If not controlled effectively, this hormonal hypersecretion could lead to extremely elevated final adult height. The past 10 years have seen marked advances in the understanding of pituitary gigantism, including the identification of genetic causes in ~50% of cases, such as mutations in the AIP gene or chromosome Xq26.3 duplications in X-linked acrogigantism syndrome. Pituitary gigantism has a male preponderance, and patients usually have large pituitary adenomas. The large tumour size, together with the young age of patients and frequent resistance to medical therapy, makes the management of pituitary gigantism complex. Early diagnosis and rapid referral for effective therapy appear to improve outcomes in patients with pituitary gigantism; therefore, a high level of clinical suspicion and efficient use of diagnostic resources is key to controlling overgrowth and preventing patients from reaching very elevated final adult heights.

Aberrant expression of the sFRP and WIF1 genes in invasive non-functioning pituitary adenomas

Non-functioning pituitary adenomas (NFPAs) are the most common pituitary tumors and mainly invade the sphenoid, cavernous sinus or dura mate. Aberrant regulation of the Wnt signaling pathway plays an important role in tumorigenesis. This study was designed to investigate the relationships between secreted frizzled-related proteins (sFRPs), WIF1 genes and the invasion of NFPAs by tissue microassays (TMAs) of samples from 163 patients. Significantly weaker staining of WIF1 and sFRP4 were detected in the invasive group compared with the non-invasive group by TMAs (p = 0.002, p < 0.001). Univariate analysis showed a significant correlation between tumor invasion and low expression of WIF1 and sFRP4 (p = 0.002, p < 0.001). A similar trend was observed when analyzing the mRNA and protein levels through RT-PCR and western blot experiments. Methylation of the WIF1 promoter was significantly increased in invasive NFPAs compared with the noninvasive group (p = 0.004). The average progression free survival time in the high WIF1 group was longer than that in the low WIF1 group (p = 0.025). Furthermore, RT-PCR measured the levels of 11 miRNAs targeting WIF1 according to the Targetscan database and PubMed. The levels of miRNA-137, miRNA-374a-5p and miRNA-374b-5p in the invasive group were 0.037-fold, 0.577-fold and 0.44-fold that of the noninvasive group (p = 0.003, p = 0.049 and p = 0.047). Overexpression of miRNA-137 could inhibit the proliferation and invasion of GH3 cells through cell viability and Transwell experiments (p < 0.05). Furthermore, the WIF1 level was upregulated after overexpression of miRNA-137 compared with miRNA-137-NC (control miRNA) in GH3 cells. Our data suggest that WIF1 may be potential biomarker for the aggressiveness of NFPAs. miRNA-137 plays an important role in the Wnt signaling pathway by affecting promoter methylation of WIF1.

DNA methylation profiling in nonfunctioning pituitary adenomas

Nonfunctioning pituitary adenomas (NFPAs) are among the most frequent intracranial tumors but their molecular background, including changes in epigenetic regulation, remains poorly understood. We performed genome-wide DNA methylation profiling of 34 NFPAs and normal pituitary samples. Methylation status of the selected genomic regions and expression level of corresponding genes were assessed in a group of 75 patients. NFPAs exhibited distinct global methylation profile as compared to normal pituitary. Aberrant DNA methylation appears to contribute to deregulation of the cancer-related pathways as shown by preliminary functional analysis. Promoter hypermethylation and decreased expression level of SFN, STAT5A, DUSP1, PTPRE and FGFR2 was confirmed in the enlarged group of NFPAs. Difference in the methylation profiles between invasive and non-invasive NFPAs is very slight. Nevertheless, invasiveness-related aberrant epigenetic deregulation of the particular genes was found including upregulation of ITPKB and downregulation CNKSR1 in invasive tumors.

Germline mutations of aryl hydrocarbon receptor-interacting protein (AIP) gene and somatostatin receptor 1-5 and AIP immunostaining in patients with sporadic acromegaly with poor versus good response to somatostatin analogues

OBJECTIVE

To determine aryl hydrocarbon interacting protein (AIP) gene variations and AIP and somatostatin receptor (SSTR) 1-5 immunostaining in patients with apparently sporadic acromegaly with poor versus good response to somatostatin analogues (SRLs).

METHODS

A total of 94 patients (66 with poor and 28 with good response to SRLs) were screened for the AIP gene variations using Sanger sequencing. Immunostaining was performed in 60 tumors.

RESULTS

Several variations, albeit some with undetermined significance, were detected, especially in poor responder patients. The prevalence of AIP mutation was 2.1% in the whole group and 1.5% in patients with poor response to SRLs. AIP, SSTR2A, and SSTR2B immunostainings were decreased in patients with poor response (p < 0.05 for all), and other SSTRs did not differ between the groups (p > 0.05 for all). Patients with low AIP had decreased levels of SSTR2A and SSTR3 (p < 0.05 for all). AIP and SSTR2A immunostainings were positively correlated to the treatment response and age at diagnosis was negatively correlated (p < 0.05 for all). In poor responder patients with high SSTR2A immunostaining, SSTR2B immunostaining and preoperative tumor size were positively and negatively correlated, respectively, to SRL response (p < 0.05 for all).

CONCLUSIONS

Lack of response to SRLs does not necessarily increase the risk of harboring AIP mutations. The finding of decreased AIP, SSTR2A, and SSTR2B immunostaining in patients with poor response to SRLs and decreased SSTR2A and SSTR3 level in those with low AIP immunostaining suggests a possible interaction between AIP and some SSTR subtypes that might alter SRL sensitivity.

In vivo bioassay to test the pathogenicity of missense human AIP variants

Background

Heterozygous germline loss-of-function mutations in the aryl hydrocarbon receptor-interacting protein gene (AIP) predispose to childhood-onset pituitary tumours. The pathogenicity of missense variants may pose difficulties for genetic counselling and family follow-up.

Objective

To develop an in vivo system to test the pathogenicity of human AIP mutations using the fruit fly Drosophila melanogaster.

Methods

We generated a null mutant of the Drosophila AIP orthologue, CG1847, a gene located on the Xchromosome, which displayed lethality at larval stage in hemizygous knockout male mutants (CG1847^exon1_3). We tested human missense variants of ‘unknown significance’, with ‘pathogenic’ variants as positive control.

Results

We found that human AIP can functionally substitute for CG1847, as heterologous overexpression of human AIP rescued male CG1847^exon1_3 lethality, while a truncated version of AIP did not restore viability. Flies harbouring patient-specific missense AIP variants (p.C238Y, p.I13N, p.W73R and p.G272D) failed to rescue CG1847^exon1_3 mutants, while seven variants (p.R16H, p.Q164R, p.E293V, p.A299V, p.R304Q, p.R314W and p.R325Q) showed rescue, supporting a non-pathogenic role for these latter variants corresponding to prevalence and clinical data.

Conclusion

Our in vivo model represents a valuable tool to characterise putative disease-causing human AIP variants and assist the genetic counselling and management of families carrying AIP variants.

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.

AIP and the somatostatin system in pituitary tumours

Classic somatostatin analogues aimed at somatostatin receptor type 2, such as octreotide and lanreotide, represent the mainstay of medical treatment for acromegaly. These agents have the potential to decrease hormone secretion and reduce tumour size. Patients with a germline mutation in the aryl hydrocarbon receptor-interacting protein gene, AIP, develop young-onset acromegaly, poorly responsive to pharmacological therapy. In this review, we summarise the most recent studies on AIP-related pituitary adenomas, paying special attention to the causes of somatostatin resistance; the somatostatin receptor profile including type 2, type 5 and truncated variants; the role of G proteins in this pathology; the use of first and second generation somatostatin analogues; and the role of ZAC1, a zinc-finger protein with expression linked to AIP in somatotrophinoma models and acting as a key mediator of octreotide response.

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.

Role of Phosphodiesterases on the Function of Aryl Hydrocarbon Receptor-Interacting Protein (AIP) in the Pituitary Gland and on the Evaluation of AIP Gene Variants

Familial isolated pituitary adenoma (FIPA) is caused in about 20% of cases by loss-of-function germline mutations in the AIP gene. Patients harboring AIP mutations usually present with somatotropinomas resulting either in gigantism or young-onset acromegaly. AIP encodes for a co-chaperone protein endowed with tumor suppressor properties in somatotroph cells. Among other mechanisms proposed to explain this function, a regulatory effect over the 3',5'-cyclic adenosine monophosphate (cAMP) signaling pathway seems to play a prominent role. In this setting, the well-known interaction between AIP and 2 different isoforms of phosphodiesterases (PDEs), PDE2A3 and PDE4A5, is of particular interest. While the interaction with over-expressed AIP does not seem to affect PDE2A3 function, the reported effect on PDE4A5 is, in contrast, reduced enzymatic activity. In this review, we explore the possible implications of these molecular interactions for the function of somatotroph cells. In particular, we discuss how both PDEs and AIP could act as negative regulators of the cAMP pathway in the pituitary, probably both by shared and independent mechanisms. Moreover, we describe how the evaluation of the AIP-PDE4A5 interaction has proven to be a useful tool for testing AIP mutations, complementing other in silico, in vitro, and in vivo analyses. Improved assessment of the pathogenicity of AIP mutations is indeed paramount to provide adequate guidance for genetic counseling and clinical screening in AIP mutation carriers, which can lead to prospective diagnosis of pituitary adenomas.

Impact of AIP and inhibitory G protein alpha 2 proteins on clinical features of sporadic GH-secreting pituitary adenomas

INTRODUCTION

In sporadic acromegaly, downregulation of AIP protein of the adenomas associates with invasive tumor features and reduced responsiveness to somatostatin analogues. AIP is a regulator of Ga_i signaling, but it is not known how the biological function of the Ga_i pathway is controlled.

AIM

To study GNAS and AIP mutation status, AIP and Ga_i-2 protein expressions, Ki-67 proliferation indices and clinical parameters in patients having primary surgery because of acromegaly at a single center between years 2000 and 2010.

RESULTS

Sixty patients (F/M, 31/29), mean age 49 (median 50), mean follow-up 7.7 years (range 0.6-14.0) underwent primary surgery. Four adenoma specimens (6.8%) harbored an AIP and 21 (35.6%) an activating GNAS (Gsp+) mutation. Altogether 13/56 (23%) adenomas had low AIP protein levels, and 14/56 (25%) low Ga_i-2 staining. In regression modeling, AIP expression associated with Ga_i-2 (P = 2.33 × 10^-9) and lower Ki-67 (P = 0.04). In pairwise comparison, low AIP protein predicted high GH at last follow-up (mean 7.7 years after surgery, q = 0.045). Extent of treatments given for acromegaly associated with higher preoperative GH (P = 7.94 × 10^-4), KNOSP (P = 0.003) and preoperative hypopituitarism (P = 0.03) and remission at last follow-up with change in 3-month postoperative IGF1 (P = 2.07 × 10^-7).

CONCLUSIONS

We demonstrate, for the first time, that AIP protein expression associates with Ga_i-2 protein intensities in sporadic somatotropinomas, suggesting a joint regulation on somatostatin signaling. Low AIP level associates with higher proliferative activity and predicts high GH concentrations after long-term follow-up. The AIP mutation rate of 6.8% is fairly high, reflecting the genetic composition of the Finnish population.

Current biomarkers of invasive sporadic pituitary adenomas

Though pituitary adenomas (PA) are considered benign, some of them exhibit invasive behaviors such as recurrence and low rate of total surgical resection. Reliable prognostic biomarkers for invasive PA are highly desired; however they remain to be identified. In this review, we summarize the current controversial findings of biomarkers for invasive sporadic PA, and we discuss the possible reasons for the controversies.

A review on the diagnosis and treatment of patients with clinically nonfunctioning pituitary adenoma by the Neuroendocrinology Department of the Brazilian Society of Endocrinology and Metabolism

Clinically nonfunctioning pituitary adenomas (NFPA) are the most common pituitary tumors after prolactinomas. The absence of clinical symptoms of hormonal hypersecretion can contribute to the late diagnosis of the disease. Thus, the majority of patients seek medical attention for signs and symptoms resulting from mass effect, such as neuro-ophthalmologic symptoms and hypopituitarism. Other presentations include pituitary apoplexy or an incidental finding on imaging studies. Mass effect and hypopituitarism impose high morbidity and mortality. However, early diagnosis and effective treatment minimizes morbidity and mortality. In this publication, the goal of the Neuroendocrinology Department of the Brazilian Society of Endocrinology and Metabolism is to provide a review of the diagnosis and treatment of patients with NFPA, emphasizing that the treatment should be performed in reference centers. This review is based on data published in the literature and the authors' experience. Arch Endocrinol Metab. 2016;60(4):374-90.

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.

Expression of Peroxisome Proliferator-Activated Receptor alpha (PPARα) in somatotropinomas: Relationship with Aryl hydrocarbon receptor Interacting Protein (AIP) and in vitro effects of fenofibrate in GH3 cells

PURPOSE

To search for a possible role of Peroxisome Proliferator-Activated Receptor α (PPARα), a molecular partner of the Aryl hydrocarbon receptor Interacting Protein (AIP), in somatotropinomas.

METHODS

Tumours from 51 acromegalic patients were characterized for PPARα and AIP expression by immunohistochemistry (IHC) and/or Real Time RT-PCR. Data were analysed according to tumour characteristics and pre-operative treatment with somatostatin analogues (SSA). The effects of fenofibrate were studied in GH3 cells in vitro.

RESULTS

PPARα was expressed in most somatotropinomas. A modest relationship was found between PPARα and AIP expression, both being significantly higher in the presence of pre-operative SSA. However, only AIP expression was influenced by the response to treatment. Dual effects of fenofibrate were observed in GH3 cells, consisting of cell growth inhibition and an increase in GH secretion inhibited by octreotide.

CONCLUSIONS

PPARα is a new player in somatotropinomas. Potential interactions between PPARα agonists and SSA may deserve further investigation.

Factors predicting pasireotide responsiveness in somatotroph pituitary adenomas resistant to first-generation somatostatin analogues: an immunohistochemical study

AIM

To gather data regarding factors predicting responsiveness to pasireotide in acromegaly.

PATIENTS AND METHODS

SSTR2a, SSTR3, SSTR5, AIP, Ki-67 and the adenoma subtype were evaluated in somatotroph adenomas from 39 patients treated post-operatively with somatostatin analogues (SSAs). A standardized SSTR scoring system was applied (scores 0-3). All patients received first-generation SSAs, and 11 resistant patients were subsequently treated with pasireotide LAR.

RESULTS

None of the patients with negative or cytoplasmic-only SSTR2a expression (scores 0-1) were responsive to first-generation SSAs, as opposed to 20% (score 2) and 50% of patients with a score of 3 (P=0.04). None of the patients with an SSTR5 score of 0-1 were responsive to pasireotide, as opposed to 5/7 cases with a score of 2 or 3 (P=0.02). SSTR3 expression did not influence first-generation SSAs or pasireotide responsiveness. Tumours with low AIP were resistant to first-generation SSAs (100 vs 60%; P=0.02), while they had similar responsiveness to pasireotide compared to tumours with conserved AIP expression (50 vs 40%; P=0.74). Tumours with low AIP displayed reduced SSTR2 (SSTR2a scores 0-1 44.4 vs 6.7%; P=0.006) while no difference was seen in SSTR5 (SSTR5 scores 0-1 33.3 vs 23.3%; P=0.55). Sparsely granulated adenomas responded better to pasireotide compared to densely granulated ones (80 vs 16.7%; P=0.04).

CONCLUSION

The expression of SSTR5 might predict responsiveness to pasireotide in acromegaly. AIP deficient and sparsely granulated adenomas may benefit from pasireotide treatment. These results need to be confirmed in larger series of pasireotide-treated patients.

Dopamine receptor subtype 2 expression profile in nonfunctioning pituitary adenomas and in vivo response to cabergoline therapy

OBJECTIVES

To determine the dopamine receptor subtype 2 (DR2) mRNA levels and protein expression and to evaluate the effect of adjuvant cabergoline therapy on tumour volume (TV) in patients with postoperative residual nonfunctioning pituitary adenoma (NFPA).

METHODS

The mRNA expression was quantified by real-time RT-PCR (TaqMan(®)), and protein expression was evaluated by immunohistochemistry. Tumours were classified according to the percentage of immunostained cells for DR2 as scores 1 (<50% of stained cells) or 2 (≥50%). Cabergoline was started at least 6 months after surgery in nine patients with residual tumours (3 mg/week). The cabergoline effect was prospectively evaluated by magnetic resonance imaging using three-dimensional volume calculation. TV reduction >25% was considered significant.

RESULTS

The DR2 mRNA expression was variable but was observed in 100% of the samples (N = 20). DR2 protein expression was also observed in all the tumours (N = 34). Twenty-nine tumours (85%) were classified as score 2. The median DR2 mRNA expression was higher in the tumours classified as score 2 compared with score 1 (P = 0·007). TV reduction with cabergoline therapy was observed in 67% of the patients (6/9). The median TV before and after 6 months of treatment was 1·90 cm(3) (0·61-8·74) and 1·69 cm(3) (0·36-4·20) [P = 0·02], respectively.

CONCLUSION

In conclusion, DR2 is expressed in all adenomas and the majority of the patients in this study displayed tumour shrinkage on cabergoline (CAB) therapy. Thus, CAB might be useful in adjuvant therapy in NFPA patients with residual tumours after surgery.

Truncated somatostatin receptor variant sst5TMD4 confers aggressive features (proliferation, invasion and reduced octreotide response) to somatotropinomas

The GH/IGF1 response of somatotropinomas to somatostatin analogues (SSA) is associated with their pattern of somatostatin receptor (sst1-sst5) expression. Recently, we demonstrated that expression of a truncated sst5-variant (sst5TMD4) can influence the secretory response of somatotropinomas to SSA-therapy; however, its potential relationship with aggressive features (e.g. invasion/proliferation) is still unknown. Here, we show that sst5TMD4 is present in 50% of non-functioning pituitary-adenomas (NFPA) (n = 30) and 89% of somatotropinomas (n = 36), its expression levels being highest in somatotropinomas > > NFPAs > > > normal pituitaries (negligible expression; n = 8). In somatotropinomas, sst5TMD4 mRNA and protein levels correlated positively, and its expression was directly associated with tumor invasiveness (cavernous/sphenoid sinus), and inversely correlated with age and GH/IGF1 reduction after 3-6 months with octreotide-LAR therapy. GNAS+ somatotropinomas expressed lower sst5TMD4 levels. ROC analysis revealed sst5TMD4 expression as the only marker, within all sst-subtypes, capable to predict tumor invasiveness in somatotropinomas. sst5TMD4 overexpression increased cell viability in cultured somatotropinoma (n = 5). Hence, presence of sst5TMD4 associates with increased aggressive features and worse prognosis in somatotropinomas, thereby providing a potentially useful tool to refine somatotropinoma diagnosis, predict outcome of clinical response to SSA-therapy and develop new therapeutic targets.

Regulation of aryl hydrocarbon receptor interacting protein (AIP) protein expression by MiR-34a in sporadic somatotropinomas

INTRODUCTION

Patients with germline AIP mutations or low AIP protein expression have large, invasive somatotroph adenomas and poor response to somatostatin analogues (SSA).

METHODS

To study the mechanism of low AIP protein expression 31 sporadic somatotropinomas with low (n = 13) or high (n = 18) AIP protein expression were analyzed for expression of AIP messenger RNA (mRNA) and 11 microRNAs (miRNAs) predicted to bind the 3'UTR of AIP. Luciferase reporter assays of wild-type and deletion constructs of AIP-3'UTR were used to study the effect of the selected miRNAs in GH3 cells. Endogenous AIP protein and mRNA levels were measured after miRNA over- and underexpression in HEK293 and GH3 cells.

RESULTS

No significant difference was observed in AIP mRNA expression between tumors with low or high AIP protein expression suggesting post-transcriptional regulation. miR-34a was highly expressed in low AIP protein samples compared high AIP protein adenomas and miR-34a levels were inversely correlated with response to SSA therapy. miR-34a inhibited the luciferase-AIP-3'UTR construct, suggesting that miR-34a binds to AIP-3'UTR. Deletion mutants of the 3 different predicted binding sites in AIP-3'UTR identified the c.*6-30 site to be involved in miR-34a's activity. miR-34a overexpression in HEK293 and GH3 cells resulted in inhibition of endogenous AIP protein expression.

CONCLUSION

Low AIP protein expression is associated with high miR-34a expression. miR-34a can down-regulate AIP-protein but not RNA expression in vitro. miR-34a is a negative regulator of AIP-protein expression and could be responsible for the low AIP expression observed in somatotropinomas with an invasive phenotype and resistance to SSA.

The AIP (aryl hydrocarbon receptor-interacting protein) gene and its relation to the pathogenesis of pituitary adenomas

Pituitary adenomas are monoclonal neoplasms that may secrete excessive quantities of their endogenous hormones, or may not be associated with any obvious syndrome, in which case they are known as non-functioning pituitary adenomas. Around 2 % have been said to occur in a familial setting, in the absence of any other tumor, now described as familial isolated pituitary adenomas (FIPA). Some 15-30 % of such families harbor inactivating germ-line mutations in the aryl hydrocarbon receptor-interacting protein (AIP) gene, along with 20 % of pediatric seemingly sporadic cases. AIP mutants are referred to as having pituitary adenoma predisposition, and present with early onset, aggressive macroadenomas, most of which secrete somatotropin. Evidence from transfection studies implies that AIP acts as a tumor suppressor; although whether this is mediated through an interaction with the aryl hydrocarbon receptor, phosphodiesterases, or with cell cycle regulators such as survivin or RET remains controversial. However, at present an interaction with the cyclic AMP pathway seems most plausible. Recently, evidence has shown that AIP may act at the cell surface, causing changes in integrin function. The presence of AIP mutations in a significant proportion of FIPA families as well as in apparently sporadic cases, particularly in young patients, suggests a need to screen such patients for AIP mutations to enable better clinical management. However, the absence of AIP mutations in over half of such cases highlights the need to search for further gene mutations.

The role of temozolomide in the treatment of a patient with a pure silent pituitary somatotroph carcinoma

OBJECTIVE

To describe a case of a pure silent somatotroph pituitary carcinoma.

METHODS

We describe a 54-year-old female with a clinically nonfunctioning pituitary macroadenoma diagnosed 15 years earlier.

RESULTS

The patient underwent transsphenoidal surgery and no visible tumor remnant was observed for 6 years. A magnetic resonance imaging (MRI) detected the recurrence of a 1.2 × 1.5 cm macroadenoma. The patient was submitted to conventional radiotherapy (4500 cGy), and the tumor volume remained stable for 7 years. Then, an MRI revealed a slight increase in tumor size, and 2 years later, a subsequent MRI detected a very large, invasive pituitary mass. The patient was resubmitted to transsphenoidal surgery, and the histopathological examination showed diffuse positivity for growth hormone (GH). The nadir GH level during an oral glucose tolerance test was 0.06 ng/mL, and the pre- and postoperative insulin like growth factor type I (IGF-I) levels were within the normal range. Abdominal, chest, brain, and spine MRI showed multiple small and hypervascular liver and bone lesions suggestive of metastases. Liver biopsy confirmed metastasis of GH-producing pituitary carcinoma. The patient has been treated with temozolomide and zoledronic acid for 7 months and with octreotide long-acting release (LAR) for 4 months. The primary tumor and metastases are stable.

CONCLUSION

Despite being an extremely rare event, pituitary carcinoma may develop several years after the successful treatment of even a silent GH-producing pituitary adenoma, which suggests that close long-term follow-up is necessary.

ZAC1 and SSTR2 are downregulated in non-functioning pituitary adenomas but not in somatotropinomas

Introduction

There are few data regarding ZAC1 expression in clinically non-functioning pituitary adenomas (NFPA). Because somatotropinomas and NFPA behave differently with respect to tumor shrinkage during somatostatin analogs (SA) therapy, we sought to compare the ZAC1 and somatostatin receptor (sstr) types 1, 2, 3 and 5 mRNA expression in these two pituitary adenoma subtypes and in normal human pituitaries.

Methods

ZAC1 and SSTR mRNA expression levels were evaluated using real-time RT-PCR (TaqMan) in 20 NFPA and compared with the expression levels in 23 somatotropinomas and five normal pituitaries. The NFPA invasiveness was evaluated using magnetic resonance imaging with Hardy’s modified criteria. Ki-67 and p53 were evaluated using immunohistochemistry.

Results

A total of 20 patients with NFPA [6 males, median age 56 years (range: 30-78)], 23 with acromegaly [12 males, median age 43 years (range: 24–57)] and five normal pituitaries [4 males, median age 48 years (range: 36–54)] were included. Four of the patients (20%) had Hardy’s grade 2 tumors; all of the others had Hardy’s grade 3 tumors. The Ki-67 median expression was 2.35 (range: 0.2–9.23), and only four of the tumors (20%) were positive for p53. The ZAC1 mRNA expression was significantly lower in NFPA than in somatotropinomas and in normal pituitaries (p<0.001 for both), as well as the SSTR2 (p=0.001 and 0.01, respectively). The SSTR3 expression was higher in the NFPA than in the somatotropinomas and in the normal pituitaries (p=0.03 and 0.02, respectively). No correlation was found between the ZAC1 mRNA expression and the tumor invasiveness, Ki-67 and p53.

Conclusion

ZAC1 and SSTR2 are underexpressed and SSTR3 is overexpressed in NFPA compared to those in somatotropinomas and in normal pituitaries, which might explain the lack of tumor shrinkage that is observed in response to commercially available SA therapy in patients with NFPA.

Somatostatin analogues increase AIP expression in somatotropinomas, irrespective of Gsp mutations

Germline aryl hydrocarbon receptor interacting protein (AIP) gene mutations confer a predisposition to pituitary adenoma (PA), predominantly GH-secreting (GH-PA). As recent data suggest a role for AIP in the pathogenesis of sporadic GH-PA and their response to somatostatin analogues (SSA), the expression of AIP and its partner, aryl hydrocarbon receptor (AHR), was determined by semiquantitative immunohistochemistry scoring in 62 sporadic GH-PA (37 treated with SSA preoperatively). The influence of Gsp status was studied in a subset of tumours (n=39, 14 Gsp(+)) and six GH-PA were available for primary cultures. AIP and AHR were detected in most cases, with a positive correlation between AIP and cytoplasmic AHR (P=0.012). Low AIP expression was significantly more frequent in untreated vs SSA-treated tumours (44.0 vs 20.5%, P=0.016). AHR expression or localisation did not differ between the two groups. Similarly, in vitro octreotide induced a median twofold increase in AIP expression (range 1.2-13.9, P=0.027) in GH-PA. In SSA-treated tumours, the AIP score was significantly higher in the presence of preoperative IGF1 decrease or tumour shrinkage (P=0.008 and P=0.014 respectively). In untreated tumours, low AIP expression was significantly associated with invasiveness (P=0.028) and suprasellar extension (P=0.019). The only effect of Gsp status was a significantly lower nuclear AHR score in Gsp(+) vs Gsp(-) tumours (P=0.025), irrespective of SSA. In conclusion, AIP is involved in the aggressiveness of sporadic GH-PA, regardless of Gsp status, and AIP up-regulation in SSA-treated tumours is associated with a better preoperative response, with no clear role for AHR.

Ki-67 is a predictor of acromegaly control with octreotide LAR independent of SSTR2 status and relates to cytokeratin pattern

INTRODUCTION

Only one study has evaluated Ki-67 as a predictor of the response to somatostatin analog therapy in acromegaly; however, other predictors like somatostatin receptor type 2 (SSTR2) and cytokeratin pattern expressions were not considered.

OBJECTIVE

To evaluate whether Ki-67 is a predictor of octreotide LAR (OCT-LAR) response in somatotropinomas independent of SSTR2 and cytokeratin expression patterns.

METHODS

Protein expression was analyzed by immunohistochemistry. The percentage of cell nuclei that were immunolabeled for Ki-67 and the percentage of cells with positive SSTR2 staining were calculated. SSTR2 expression was considered high when ≥25%, and a cutoff of 2.3% was designated for Ki-67. Tumors were classified as densely or sparsely granulated according to the cytokeratin pattern.

RESULTS

Thirty-one somatotropinomas were studied. Fourteen patients (45.2%) were controlled with OCT-LAR therapy. The median Ki-67 labeling index (LI) was higher in patients not controlled with OCT-LAR than in those controlled (1.63 and 0.15 respectively, P=0.002). Higher SSTR2 expression and densely granulated tumors were correlated with control as well (P=0.04 and 0.038 respectively). There was no difference in Ki-67 levels between patients with high and low SSTR2 expression (P=0.651). After multivariate analysis, both Ki-67 and SSTR2 remained statistically significant as predictors of OCT-LAR response (P=0.017 and 0.012 respectively). The Ki-67 LI was higher in sparsely than in densely granulated tumors (P=0.047).

CONCLUSIONS

Ki-67 is a predictor of response to OCT-LAR in acromegaly, independent of SSTR2 expression and relates to cytokeratin patterns.

Novel pathway for somatostatin analogs in patients with acromegaly

Acromegaly is a chronic disease with increased morbidity and mortality, where usually multiple treatment modalities are used. The somatostatin analogs (SSAs) are the mainstay of medical therapy but, in many patients, including those with a germline mutation in the aryl hydrocarbon receptor-interacting protein (AIP) gene, disease activity cannot be controlled with these drugs. Previous data have suggested the involvement of the tumor-suppressor gene ZAC1 in the mechanism of action of SSAs, and more recent findings suggested that SSAs could regulate AIP, which in turn can stimulate ZAC1, therefore suggesting the existence of a SSA-AIP-ZAC1-somatostatin effect pathway. The current review discusses these novel observations, highlighting their significance in the treatment of sporadic and familial somatotroph adenomas.