SSTR3 is a putative target for the medical treatment of gonadotroph adenomas of the pituitary

CPEB2 inhibits preeclampsia progression by regulating SSTR3 translation through polyadenylation

AIMS

Trophoblast cell dysfunction is one of the important factors leading to preeclampsia (PE). Cytoplasmic polyadenylation element-binding 2 (CPEB2) has been found to be differentially expressed in PE patients, but whether it mediates PE process by regulating trophoblast cell function is unclear.

METHODS

The expression of CPEB2 and somatostatin receptor 3 (SSTR3) was detected by quantitative real-time PCR, Western blot (WB) and immunofluorescence staining. Cell functions were analyzed by CCK-8 assay, EdU assay, flow cytometry and transwell assay. Epithelial-mesenchymal transition (EMT)-related protein levels were detected by WB. The interaction of CPEB2 and SSTR3 was confirmed by RIP assay, dual-luciferase reporter assay and PCR poly(A) tail assay. Animal experiments were performed to explore the effect of CPEB2 on PE progression in vivo, and the placental tissues of rat were used for H&E staining, immunohistochemical staining and TUNEL staining.

RESULTS

CPEB2 was lowly expressed in PE patients. CPEB2 upregulation accelerated trophoblast cell proliferation, migration, invasion and EMT, while its knockdown had an opposite effect. CPEB2 bound to the CPE site in the 3'-UTR of SSTR3 mRNA to suppress SSTR3 translation through reducing poly(A) tails. Besides, SSTR3 overexpression suppressed trophoblast cell proliferation, migration, invasion and EMT, while its silencing accelerated trophoblast cell functions. However, these effects could be reversed by CPEB2 upregulation and knockdown, respectively. In vivo experiments, CPEB2 overexpression relieved histopathologic changes, inhibited apoptosis, promoted proliferation and enhanced EMT in the placenta of PE rat by decreasing SSTR3 expression.

CONCLUSION

CPEB2 inhibited PE progression, which promoted trophoblast cell functions by inhibiting SSTR3 translation through polyadenylation.

The Novel SSTR3 Agonist ITF2984 Exerts Antimitotic and Proapoptotic Effects in Human Non-Functioning Pituitary Neuroendocrine Tumor (NF-PitNET) Cells

Somatostatin receptor ligands (SRLs) with high affinity for somatostatin receptors 2 and 5 (SSTR2 and SSTR5) are poorly efficacious in NF-PitNETs, expressing high levels of SSTR3. ITF2984 is a pan-SSTR ligand with high affinity for SSTR3, able to induce SSTR3 activation and to exert antitumoral activity in the MENX rat model. The aim of this study was to test ITF2984's antiproliferative and proapoptotic effects in NF-PitNET primary cultured cells derived from surgically removed human tumors and to characterize their SSTR expression profile. We treated cells derived from 23 NF-PitNETs with ITF2984, and a subset of them with octreotide, pasireotide (SRLs with high affinity for SSTR2 or 5, respectively), or cabergoline (DRD2 agonist) and we measured cell proliferation and apoptosis. SSTR3, SSTR2, and SSTR5 expression in tumor tissues was analyzed by qRT-PCR and Western blot. We demonstrated that ITF2984 reduced cell proliferation (-40.8 (17.08)%, p < 0.001 vs. basal, n = 19 NF-PitNETs) and increased cell apoptosis (+41.4 (22.1)%, p < 0.001 vs. basal, n = 17 NF-PitNETs) in all tumors tested, whereas the other drugs were only effective in some tumors. In our model, SSTR3 expression levels did not correlate with ITF2984 antiproliferative nor proapoptotic effects. In conclusion, our data support a possible use of ITF2984 in the pharmacological treatment of NF-PitNET.

Somatostatin and Somatostatin Receptors in Tumour Biology

Somatostatin (SST), a growth hormone inhibitory peptide, is expressed in endocrine and non-endocrine tissues, immune cells and the central nervous system (CNS). Post-release from secretory or immune cells, the first most appreciated role that SST exhibits is the antiproliferative effect in target tissue that served as a potential therapeutic intervention in various tumours of different origins. The SST-mediated in vivo and/or in vitro antiproliferative effect in the tumour is considered direct via activation of five different somatostatin receptor subtypes (SSTR1-5), which are well expressed in most tumours and often more than one receptor in a single cell. Second, the indirect effect is associated with the regulation of growth factors. SSTR subtypes are crucial in tumour diagnosis and prognosis. In this review, with the recent development of new SST analogues and receptor-specific agonists with emerging functional consequences of signaling pathways are promising therapeutic avenues in tumours of different origins that are discussed.

Update on Current Evidence for the Diagnosis and Management of Nonfunctioning Pituitary Neuroendocrine Tumors

Pituitary neuroendocrine tumors (PitNETs) are the third most frequently diagnosed intracranial tumors, with nonfunctioning PitNETs (nfPitNETs) accounting for 30% of all pituitary tumors and representing the most common type of macroPitNETs. NfPitNETs are usually benign tumors with no evidence of hormone oversecretion except for hyperprolactinemia secondary to pituitary stalk compression. Due to this, they do not typically present with clinical syndromes like acromegaly, Cushing's disease or hyperthyroidism and instead are identified incidentally on imaging or from symptoms of mass effects (headache, vision changes, apoplexy). With the lack of effective medical interventions, first-line treatment is transsphenoidal surgical resection, however, nfPitNETs often have supra- or parasellar extension, and total resection of the tumor is often not possible, resulting in residual tumor regrowth or reoccurrence. While functional PitNETs can be easily followed for recurrence using hormonal biomarkers, there is no similar parameter to predict recurrence in nfPitNETs, hence delaying early recognition and timely management. Therefore, there is a need to identify prognostic biomarkers that can be used for patient surveillance and as therapeutic targets. This review focuses on summarizing the current evidence on nfPitNETs, with a special focus on potential new biomarkers and therapeutics.

Expression prevalence and dynamics of GPCR somatostatin receptors 2 and 3 as cancer biomarkers beyond NET: a paired immunohistochemistry approach

Somatostatin receptors are clinically validated GPCR biomarkers for diagnosis and treatment of various neuroendocrine tumors (NET). Among the five somatostatin receptors, SST2 and SST3 are associated with apoptosis and cell cycle arrest, making these receptor subtypes better differentiated targets in precision oncology. In this study we performed immunohistochemistry of paired tissue microarrays containing 1125 cores, representing 43 tumor types, each stained for SST2 and SST3. A 12-point immunoreactive scoring (IRS) range was used for interpretation of the staining results. We analyzed the results twice, using the conventional positivity IRS cutoffs ≥ 3 and more stringent ≥ 6. Evaluation of receptors expression dynamics was performed for tumor-nodes-metastases (TNM) defined subgroups (ovarian and hepatocellular adenocarcinomas) as a function of their tumor stage. Our results indicate that two-thirds of tested cores exhibit clinically significant expression of at least SST2 or SST3 (IRS ≥ 6). The expression prevalence of both receptors tends to decline with tumor progression. However, an unexpected upregulation of both SST2 and SST3 reemerged in metastases suggesting conserved receptors genetic potential during tumor life cycle. We suggest that SST2 and SST3 should be further explored as potential biomarkers and therapeutic tools for maximizing the efficiency of somatostatin-based precision oncology of solid tumors beyond NET.

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.

Clinical characteristics of functioning gonadotroph adenoma in women presenting with ovarian hyperstimulation: Audit of UK pituitary centres

OBJECTIVE

Functioning gonadotroph adenomas (FGAs) are rare pituitary tumours stimulating ovarian function with potential life-threatening consequences in women. However, a lack of aggregated clinical experience of FGAs impairs management in affected women. The aim of this study is to present the clinical course of FGA-induced ovarian hyperstimulation syndrome (OHSS) cases as identified by some of the largest UK pituitary endocrine tertiary centres with a view to increasing awareness and improving diagnosis and management of women with FGA.

DESIGN

A retrospective observational study; audit of eight UK regional pituitary centres for cases of FGAs.

SETTING

Specialist neuroendocrine centres in the United Kingdom.

PATIENTS AND MEASUREMENTS

Women diagnosed with FGA-induced OHSS. Description of their clinical course.

RESULTS

Seven cases of FGA were identified in women, all causing OHSS. Mean age was 33.4 years at diagnosis. Abdominal pain, irregular periods, headache, and visual disturbances were reported at presentation by 100%, 71%, 57% and 43% of women, respectively. Three of seven women underwent ovarian surgery before FGA diagnosis. Six women underwent transsphenoidal surgery (TSS) with incomplete tumour resection in five of those, but all showed improvement or resolution in symptoms and biochemistry postoperatively.

CONCLUSION

FGA is a rare cause of spontaneous OHSS. TSS improves clinical and biochemical features of ovarian hyperstimulation in FGAs. Improved awareness of FGA will prevent inappropriate emergency ovarian surgery.

Integrated Multi-Omic Analysis Reveals Immunosuppressive Phenotype Associated with Poor Outcomes in High-Grade Serous Ovarian Cancer

High-grade serous ovarian cancer (HGSOC) is characterized by a complex genomic landscape, with both genetic and epigenetic diversity contributing to its pathogenesis, disease course, and response to treatment. To better understand the association between genomic features and response to treatment among 370 patients with newly diagnosed HGSOC, we utilized multi-omic data and semi-biased clustering of HGSOC specimens profiled by TCGA. A Cox regression model was deployed to select model input features based on the influence on disease recurrence. Among the features most significantly correlated with recurrence were the promotor-associated probes for the NFRKB and DPT genes and the TREML1 gene. Using 1467 transcriptomic and methylomic features as input to consensus clustering, we identified four distinct tumor clusters-three of which had noteworthy differences in treatment response and time to disease recurrence. Each cluster had unique divergence in differential analyses and distinctly enriched pathways therein. Differences in predicted stromal and immune cell-type composition were also observed, with an immune-suppressive phenotype specific to one cluster, which associated with short time to disease recurrence. Our model features were additionally used as a neural network input layer to validate the previously defined clusters with high prediction accuracy (91.3%). Overall, our approach highlights an integrated data utilization workflow from tumor-derived samples, which can be used to uncover novel drivers of clinical outcomes.

Identification of a Novel SSTR3 Full Agonist for the Treatment of Nonfunctioning Pituitary Adenomas

Somatostatin receptor (SSTR) agonists have been extensively used for treating neuroendocrine tumors. Synthetic therapeutic agonists showing selectivity for SSTR2 (Octreotide) or for SSTR2 and SSTR5 (Pasireotide) have been approved for the treatment of patients with acromegaly and Cushing's syndrome, as their pituitary tumors highly express SSTR2 or SSTR2/SSTR5, respectively. Nonfunctioning pituitary adenomas (NFPAs), which express high levels of SSTR3 and show only modest response to currently available SSTR agonists, are often invasive and cannot be completely resected, and therefore easily recur. The aim of the present study was the evaluation of ITF2984, a somatostatin analog and full SSTR3 agonist, as a new potential treatment for NFPAs. ITF2984 shows a 10-fold improved affinity for SSTR3 compared to Octreotide or Pasireotide. Molecular modeling and NMR studies indicated that the higher affinity for SSTR3 correlates with a higher stability of a distorted β-I turn in the cyclic peptide backbone. ITF2984 induces receptor internalization and phosphorylation, and triggers G-protein signaling at pharmacologically relevant concentrations. Furthermore, ITF2984 displays antitumor activity that is dependent on SSTR3 expression levels in the MENX (homozygous mutant) NFPA rat model, which closely recapitulates human disease. Therefore, ITF2984 may represent a novel therapeutic option for patients affected by NFPA.

Current medical treatment and perspective in gonadotroph tumors

Gonadotroph cell adenoma is the most common clinically nonfunctioning pituitary adenoma; and is pathologically defined by immunopositivity for SF-1, GATA2 and ER-α. Most tumors also stain for follicle stimulating hormone and luteinizing hormone β-subunits, but are usually hormonally silent and discovered incidentally or due to local mass effects. Complete transsphenoidal resection should be attempted when surgery is indicated. Post-surgical treatment can include radiation of the tumor remnant and medical treatment. Among medical treatments, dopamine agonists show the best evidence for preventing the need for recurrent surgery or radiation, and should be considered in patients with relatively bulky remnants or who have high risk features associated with tumor progression. Temozolomide is indicated for aggressive adenomas and carcinomas. Less well-established treatments include somatostatin receptor ligands, peptide receptor radionucleotide therapy and immunomodulatory agents.

Updating the Landscape for Functioning Gonadotroph Tumors

Functioning gonadotroph adenomas (FGAs) are rare tumors, as the overwhelming majority of gonadotroph tumors are clinically silent. Literature is based on case reports and small case series. Gonadotroph tumors are poorly differentiated and produce and secrete hormones inefficiently, but in exceptional cases, they cause clinical syndromes due to hypersecretion of intact gonadotropins. The clinical spectrum of endocrine dysfunction includes an exaggerated response of ovaries characterized as ovarian hyperstimulation syndrome (OHSS) in premenopausal females and adolescent girls, testicular enlargement in males, and isosexual precocious puberty in children. Transsphenoidal surgery and removal of tumor reduces hormonal hypersecretion, improves endocrine dysfunction, and provides tissue for further analysis. Medical therapies (somatostatin analogues, dopamine agonists, GnRH agonists/antagonists) are partially or totally ineffective in many cases, especially with respect to antitumor effect. This review aims to update recent literature on these rare functioning tumors and highlight their therapeutic management.

A Convolutional Neural Network Model for Detecting Sellar Floor Destruction of Pituitary Adenoma on Magnetic Resonance Imaging Scans

Objective

Convolutional neural network (CNN) is designed for image classification and recognition with a multi-layer neural network. This study aimed to accurately assess sellar floor invasion (SFI) of pituitary adenoma (PA) using CNN.

Methods

A total of 1413 coronal and sagittal magnetic resonance images were collected from 695 patients with PAs. The enrolled images were divided into the invasive group (n = 530) and the non-invasive group (n = 883) according to the surgical observation of SFI. Before model training, 100 images were randomly selected for the external testing set. The remaining 1313 cases were randomly divided into the training and validation sets at a ratio of 80:20 for model training. Finally, the testing set was imported to evaluate the model performance.

Results

A CNN model with a 10-layer structure (6-layer convolution and 4-layer fully connected neural network) was constructed. After 1000 epoch of training, the model achieved high accuracy in identifying SFI (97.0 and 94.6% in the training and testing sets, respectively). The testing set presented excellent performance, with a model prediction accuracy of 96%, a sensitivity of 0.964, a specificity of 0.958, and an area under the receptor operator curve (AUC-ROC) value of 0.98. Four images in the testing set were misdiagnosed. Three images were misread with SFI (one with conchal type sphenoid sinus), and one image with a relatively intact sellar floor was not identified with SFI.

Conclusion

This study highlights the potential of the CNN model for the efficient assessment of PA invasion.

Recent advancements in the molecular biology of pituitary adenomas

INTRODUCTION

Pituitary adenomas are a common and diverse group of intracranial tumors arising from the anterior pituitary that are usually slow-growing and benign, but still pose a significant healthcare burden to patients. Additionally, they are increasing in both incidence and prevalence, leading to a need for better understanding of molecular changes in the development of these tumors.

AREAS COVERED

A PubMed literature search was conducted using the terms 'pituitary adenoma' in combination with keywords related to secretory subtype: lactotroph, somatotroph, corticotroph, gonadotroph and null cell, in addition to their transcription factor expression: PIT1, TPIT, and SF-1. Articles resulting from this search were analyzed, as well as relevant articles cited as their references. In this review, we highlight recent advances in the genetic and epigenetic characterization of individual pituitary adenoma subtypes and the effect it may have on guiding future clinical treatment of these tumors.

EXPERT OPINION

Understanding the molecular biology of pituitary adenomas is a fundamental step toward advancing the treatment of these tumors. Yet crucial knowledge gaps exist in our understanding of the underlying molecular biology of pituitary adenomas which can potentially be addressed by turning to differentially activated molecular pathways in tumor relative to normal gland.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Pituitary adenoma & nuclear medicine: Recent outcomes and ongoing developments

In order to explore pituitary adenoma (PA), magnetic resonance imaging (MRI) remains the cornerstone. However, there are some limitations and MRI can be non-conclusive. The development of additional imaging modalities like nuclear medicine explorations may help to confirm PA diagnosis, guide management and follow up. Nuclear medicine uses radiopharmaceuticals for imaging with single photon emission computed tomography (SPECT), or positron emission tomography (PET), coupled to CT scan. Radiopharmaceuticals products target specific cellular elements which allow to explore several biological pathways. Nuclear medicine may also be used for therapeutic purposes and recent developments of approach based on Peptide Receptor Radionuclide Therapy (PRRT) for treatment of aggressive PA and pituitary carcinoma will be reviewed. Several radiotracers have been studied in the context of PA, and the aim of this paper is to discuss their respective performances and clinical interest.

Angpt2/Tie2 autostimulatory loop controls tumorigenesis

Invasive nonfunctioning (NF) pituitary neuroendocrine tumors (PitNETs) are non‐resectable neoplasms associated with frequent relapses and significant comorbidities. As the current therapies of NF‐PitNETs often fail, new therapeutic targets are needed. The observation that circulating angiopoietin‐2 (ANGPT2) is elevated in patients with NF‐PitNET and correlates with tumor aggressiveness prompted us to investigate the ANGPT2/TIE2 axis in NF‐PitNETs in the GH3 PitNET cell line, primary human NF‐PitNET cells, xenografts in zebrafish and mice, and in MENX rats, the only autochthonous NF‐PitNET model. We show that PitNET cells express a functional TIE2 receptor and secrete bioactive ANGPT2, which promotes, besides angiogenesis, tumor cell growth in an autocrine and paracrine fashion. ANGPT2 stimulation of TIE2 in tumor cells activates downstream cell proliferation signals, as previously demonstrated in endothelial cells (ECs). Tie2 gene deletion blunts PitNETs growth in xenograft models, and pharmacological inhibition of Angpt2/Tie2 signaling antagonizes PitNETs in primary cell cultures, tumor xenografts in mice, and in MENX rats. Thus, the ANGPT2/TIE2 axis provides an exploitable therapeutic target in NF‐PitNETs and possibly in other tumors expressing ANGPT2/TIE2. The ability of tumor cells to coopt angiogenic signals classically viewed as EC‐specific expands our view on the microenvironmental cues that are essential for tumor progression.

Current opinion on the diagnosis and management of non-functioning pituitary adenomas

INTRODUCTION

Non-functioning pituitary adenomas (NFPAs) are clinically silent tumors and the second most common pituitary adenoma. Surgery is the mainstay of treatment as there is, as yet, no effective medical treatment.

AREAS COVERED

We present current knowledge on the clinical diagnosis, histopathological classification, molecular data, and management strategies in NFPA.

EXPERT OPINION

NFPA is a heterogeneous group of tumors, in respect to their origin and clinical course. In recent years, research on pathology and molecular biology have advanced our knowledge of NFPA pathogenesis. NFPA exhibit, in the majority of cases, an indolent behavior, with satisfactory response to treatment. In aggressive cases, multimodal management is needed; however, even this approach may be insufficient, so the development of new treatments is warranted for better management. In this setting, the understanding of the mechanisms involved in the genesis and progression of NFPA is crucial for the identification and development of directed treatments with higher chances of response.

Gender-Specific Efficacy Revealed by Head-to-Head Comparison of Pasireotide and Octreotide in a Representative In Vivo Model of Nonfunctioning Pituitary Tumors

Simple Summary

No effective medical therapy exists for residual/recurrent nonfunctioning pituitary tumors (NFPTs). First-generation somatostatin analogs (SSAs) like octreotide targeting somatostatin receptor type 2 (SSTR2) are the mainstay therapy for functioning PTs, but have shown little effect in NFPTs. This is in agreement with an SSTR profile characterized by low SSTR2, and high SSTR3 levels in the latter. Pasireotide a multi-SSTR-preferring SSA, should be effective against NFPTs. To test this hypothesis, we conducted a head-to-head comparison of octreotide and pasireotide in the only spontaneous in vivo model of NFPTs (MENX rats), which recapitulates the human disease. Pasireotide showed a superior anti-tumor effect vs. octreotide, especially in females. Interestingly, Sstr3 levels were higher in female vs. male NFPTs. A sex-related SSTR3 expression may extend to human NFPTs, thereby representing a tool for patient stratification. Our results have translational relevance for the medical treatment of patients with residual/recurrent NFPTs currently lacking efficacious therapeutic options.

Abstract

Invasive nonfunctioning pituitary tumors (NFPTs) are non-resectable neoplasms associated with frequent relapse and significant comorbidities. Current treatments, including somatostatin receptor 2 (SSTR2)-directed somatostatin analogs (SSAs), often fail against NFPTs. Thus, identifying effective therapies is clinically relevant. As NFPTs express SSTR3 at high levels, pasireotide, a multireceptor-targeted SSA, might be beneficial. Here we evaluated pasireotide in the only representative model of spontaneous NFPTs (MENX rats) in vivo. Octreotide long-acting release (LAR), pasireotide LAR, or placebo, were administered to age-matched, tumor-bearing MENX rats of both sexes for 28 d or 56 d. Longitudinal high-resolution magnetic resonance imaging monitored tumor growth. While tumors in placebo-treated rats increased in volume over time, PTs in drug-treated rats displayed significant growth suppression, and occasional tumor shrinkage. Pasireotide elicited stronger growth inhibition. Radiological responses correlated with tumors’ proliferation rates. Both SSAs, but especially pasireotide, were more effective in female vs. male rats. Basal Sstr3 expression was significantly higher in the former group. It is noteworthy that female human NFPTs patients also have a trend towards higher SSTR3 expression. Altogether, our studies provide the rationale for testing pasireotide in patients with residual/recurrent NFPTs. If confirmed, the sex-related SSTR3 expression might be used as criteria to stratify NFPTs patients for treatment with pasireotide.

Magnetic resonance fingerprinting for preoperative differentiation between gonadotroph and non-gonadotroph pituitary macroadenomas

OBJECTIVES

To use magnetic resonance fingerprinting (MRF)-derived T1 and T2 values to differentiate gonadotroph from non-gonadotroph pituitary macroadenomas based on the 2017 World Health Organization classification of pituitary adenomas.

METHODS

A total of 57 patients with suspected pituitary macroadenomas were enrolled for analyses in this study between May 2018 and January 2020. Conventional magnetic resonance imaging (MRI) and MRF were performed in all patients before surgery using a 3-T MRI scanner. MRF-derived T1 and T2 values were compared between the gonadotroph and non-gonadotroph pituitary macroadenomas using a Mann-Whitney U test. The Knosp classification was used to evaluate cavernous sinus invasion by the adenomas. Receiver operating characteristic analyses were used to determine the diagnostic performance of T1 and T2 values.

RESULTS

Quantitative T1 and T2 values yielded from MRF of gonadotroph pituitary macroadenomas were significantly higher than those of the non-gonadotroph pituitary macroadenomas (p < 0.001 and = 0.002, respectively). The AUC for the T2 value (0.888) was significantly greater than that for the T1 value (0.742) (p = 0.034). The AUC for combined T1 and T2 values was 0.885. Non-gonadotroph pituitary macroadenomas were more likely to invade the cavernous sinus than gonadotroph pituitary macroadenomas (55% vs 26%, p = 0.026).

CONCLUSIONS

MRF may help to preoperatively differentiate between gonadotroph and non-gonadotroph pituitary macroadenomas and may be useful in guiding the treatment of these adenomas.

KEY POINTS

• Somatostatin receptor type 3 is the most abundant receptor subtype in gonadotroph pituitary adenomas. • Magnetic resonance fingerprinting may help to preoperatively differentiate between gonadotroph and non-gonadotroph pituitary macroadenomas. • Magnetic resonance fingerprinting shows potential for guiding the treatment of pituitary macroadenomas.

Prepubertal exposure to high dose of cadmium induces hypothalamic injury through transcriptome profiling alteration and neuronal degeneration in female rats

Cadmium (Cd) is a toxic metal, which seems to be crucial during the prepubertal period. Cd can destroy the structural integrity of the blood-brain barrier (BBB) and enters into the brain. Although the brain is susceptible to neurotoxicity induced by Cd, the effects of Cd on the brain, particularly hypothalamic transcriptome, are still relatively poorly understood. Therefore, we investigated the molecular effects of Cd exposure on the hypothalamus by profiling the transcriptomic response of the hypothalamus to high dose of Cd (25 mg/kg bw/day cadmium chloride (CdCl₂)) during the prepubertal period in Sprague-Dawley female rats. After sequencing and annotation, differential expression analysis revealed 1656 genes that were differentially expressed that 108 of them were classified into 37 transcription factor (TF) families. According to gene ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, these differentially expressed genes (DEGs) were involved in different biological processes and neurological disorders including Alzheimer's disease (AD), Huntington's disease (HD), and Parkinson's disease (PD), prolactin signaling pathway, PI3K/Akt signaling, and dopaminergic synapse. Five transcripts were selected for further analyses with Real-time quantitative PCR (RT-qPCR). The RT-qPCR results were mostly consistent with those from the high throughput RNA sequencing (RNA-seq). Cresyl violet staining clearly showed an increased neuronal degeneration in the dorsomedial hypothalamus (DMH) and arcuate (Arc) nuclei of the CdCl₂ group. Overall, this study demonstrates that prepubertal exposure to high doses of Cd induces hypothalamic injury through transcriptome profiling alteration in female rats, which reveals the new mechanisms of pathogenesis of Cd in the hypothalamus.

TGFBR3L-An Uncharacterised Pituitary Specific Membrane Protein Detected in the Gonadotroph Cells in Non-Neoplastic and Tumour Tissue

Simple Summary

Pituitary neuroendocrine tumours originate from the endocrine cells of the anterior pituitary gland and may develop from any of the cell lineages responsible for producing the different pituitary hormones. The details related to tumour differentiation and hormone production in these tumours are not fully understood. The aim of our study was to investigate an uncharacterised pituitary enriched protein, transforming growth factor beta-receptor 3 like (TGFBR3L). The TGFBR3L protein is highly expressed in the pituitary compared to other organs. We found the protein to be gonadotroph-specific, i.e., detected in the cells that express follicle-stimulating and luteinizing hormones (FSH/LH). The gonadotroph-specific nature of TGFBR3L, a correlation to both FSH and LH as well as an inverse correlation to membranous E-cadherin and oestrogen receptor β suggests a role in gonadotroph cell development and function and, possibly, tumour progression.

Abstract

Here, we report the investigation of transforming growth factor beta-receptor 3 like (TGFBR3L), an uncharacterised pituitary specific membrane protein, in non-neoplastic anterior pituitary gland and pituitary neuroendocrine tumours. A polyclonal antibody produced within the Human Protein Atlas project (HPA074356) was used for TGFBR3L staining and combined with SF1 and FSH for a 3-plex fluorescent protocol, providing more details about the cell lineage specificity of TGFBR3L expression. A cohort of 230 pituitary neuroendocrine tumours were analysed. In a subgroup of previously characterised gonadotroph tumours, correlation with expression of FSH/LH, E-cadherin, oestrogen (ER) and somatostatin receptors (SSTR) was explored. TGFBR3L showed membranous immunolabeling and was found to be gonadotroph cell lineage-specific, verified by co-expression with SF1 and FSH/LH staining in both tumour and non-neoplastic anterior pituitary tissues. TGFBR3L immunoreactivity was observed in gonadotroph tumours only and demonstrated intra-tumour heterogeneity with a perivascular location. TGFBR3L immunostaining correlated positively to both FSH (R = 0.290) and LH (R = 0.390) immunostaining, and SSTR3 (R = 0.315). TGFBR3L correlated inversely to membranous E-cadherin staining (R = −0.351) and oestrogen receptor β mRNA (R = −0.274). In conclusion, TGFBR3L is a novel pituitary gland specific protein, located in the membrane of gonadotroph cells in non-neoplastic anterior pituitary gland and in a subset of gonadotroph pituitary tumours.

Somatostatin receptor expression and patients' response to targeted medical treatment in pituitary tumors: evidences and controversies

BACKGROUND

Somatostatin receptors (SSTs) are widely co-expressed in pituitary tumors. SST₂ and SST₅ are the most represented SST subtypes. First-generation somatostatin receptor ligands (SRLs) mainly target SST₂, while pasireotide, a multi-receptor ligand, shows high binding affinity for both SST₅ and SST₂. Therefore, SRLs are routinely used as medical treatment for GH-, TSH-, and ACTH-secreting pituitary tumors.

METHODS

Critical revision of literature data correlating SST expression with patients' response to SRLs.

RESULTS

SST₂ expression in somatroph tumors directly correlates with GH and IGF-1 decrease after first-generation SRL treatment. SST₂ immunohistochemistry represents a valuable tool to predict biochemical response to first-generation SRLs in acromegalic patients. Pasireotide seems to exert its biological effects via SST₂ in unselected patients. However, in those subjects resistant to first-generation SRLs, harbouring tumors with negligible SST₂ expression, pasireotide can act throughout SST₅. More than somatotroph tumors, TSH-omas represent the paradigm of tumors showing a satisfactory response to SRLs. This is probably due to the high SST₂ expression observed in nearly 100% of cases, as well as to the balanced amount of SST₅. In corticotroph tumors, pasireotide mainly act via SST₅, although there is a need for translational studies correlating its efficacy with SST expression in this peculiar tumor histotype.

CONCLUSIONS

The assumption "more target receptor, more drug efficacy" is not straightforward for SRLs. The complex pathophysiology of SSTs, and the technical challenges faced to translate research findings into clinical practice, still need our full commitment to make receptor evaluation a worthwhile procedure for individualizing treatment decisions.

Treatment Options for Gonadotroph Tumors: Current State and Perspectives

CONTEXT

Gonadotroph tumors represent approximatively one-third of anterior pituitary tumors, but despite their frequency, no medical treatment is currently recommended for them. This would be greatly needed because following surgery, which is the first-line treatment, a significant percentage of gonadotroph tumors regrow.

EVIDENCE ACQUISITION

We performed PubMed searches in March 2020 using the term "gonadotroph" in combination with 36 different keywords related to dopamine type 2 receptor agonists, somatostatin receptor (SST) ligands, temozolomide, peptide receptor radionuclide therapy (PRRT), immunotherapy, vascular endothelial growth factor receptor (VEGFR)-targeted therapy, mammalian target of rapamycin (mTOR) inhibitors, and tyrosine kinase inhibitors. Articles resulting from these searches, as well as relevant references cited by these articles were reviewed.

EVIDENCE SYNTHESIS

SST2 analogs have demonstrated only very limited antitumor effect, while high-dose cabergoline has been more effective in preventing tumor regrowth, but still in only a minority of cases. In the setting of an aggressive gonadotroph tumor, temozolomide is the recommended medical treatment, but has demonstrated also only limited efficacy. Still, its efficacy has been so far better than that of PRRT. No case of a gonadotroph tumor treated with pasireotide, VEGFR-targeted therapy, mTOR inhibitors, tyrosine kinase inhibitors, or immune checkpoint inhibitors is reported in literature.

CONCLUSIONS

Gonadotroph tumors need better phenotyping in terms of both tumor cells and associated tumor microenvironment to improve their treatment. Until formal recommendations will be available, we provide the readers with our suggested approach for the management of gonadotroph tumors, management that should be discussed within multidisciplinary teams.

Quantitative Analysis of Somatostatin and Dopamine Receptors Gene Expression Levels in Non-functioning Pituitary Tumors and Association with Clinical and Molecular Aggressiveness Features

The primary treatment for non-functioning pituitary tumors (NFPTs) is surgery, but it is often unsuccessful. Previous studies have reported that NFPTs express receptors for somatostatin (SST_1-5) and dopamine (DRDs) providing a rationale for the use of dopamine agonists and somatostatin analogues. Here, we systematically assessed SST_1-5 and DRDs expression by real-time quantitative PCR (RT-qPCR) in a large group of patients with NFPTs (n = 113) and analyzed their potential association with clinical and molecular aggressiveness features. SST_1-5 expression was also evaluated by immunohistochemistry. SST₃ was the predominant SST subtype detected, followed by SST₂, SST₅, and SST₁. DRD2 was the dominant DRD subtype, followed by DRD4, DRD5, and DRD1. A substantial proportion of NFPTs displayed marked expression of SST₂ and SST₅. No major association between SST_s and DRDs expression and clinical and molecular aggressiveness features was observed in NFPTs.

The GALANT trial: study protocol of a randomised placebo-controlled trial in patients with a 68Ga -DOTATATE PET-positive, clinically non-functioning pituitary macroadenoma on the effect of lan reotide on t umour size

INTRODUCTION

At present, there is no approved medical treatment option for patients with non-functioning pituitary adenoma. A number of open-label studies suggest that treatment with somatostatin analogues may prevent tumour progression. In vivo somatostatin receptor imaging using ⁶⁸Ga-DOTATATE PET (PET, positron emission tomography) could help in preselecting patients potentially responsive to treatment. Our aim is to investigate the effect of the somatostatin analogue lanreotide as compared with placebo on tumour size in patients with a ⁶⁸Ga-DOTATATE PET-positive non-functioning pituitary macroadenoma (NFMA).

METHODS AND ANALYSIS

The GALANT study is a multicentre, randomised, double-blind, placebo-controlled trial in adult patients with a suprasellar extending NFMA. Included patients undergo a ⁶⁸Ga-DOTATATE PET/CT of the head and tracer uptake is assessed after coregistration with pituitary MRI. Forty-four patients with a ⁶⁸Ga-DOTATATE PET-positive NFMA are randomised in a 1:1 ratio between lanreotide 120 mg or placebo, both administered as subcutaneous injections every 28 days for 72 weeks. The primary outcome is the change in cranio-caudal tumour diameter on pituitary MRI after treatment. Secondary outcomes are change in tumour volume, time to tumour progression, change in quality of life and number of adverse events. Final results are expected in the second half of 2021.

ETHICS AND DISSEMINATION

The study protocol has been approved by the Medical Research Ethics Committee of the Academic Medical Centre (AMC) of the Amsterdam University Medical Centres and by the Dutch competent authority. It is an investigator-initiated study with financial support by Ipsen Farmaceutica BV. The AMC, as sponsor, remains owner of all data. Results will be submitted for publication in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

NL5136 (Netherlands Trial Register); pre-recruitment.

TBR-760, a Dopamine-Somatostatin Compound, Arrests Growth of Aggressive Nonfunctioning Pituitary Adenomas in Mice

TBR-760 (formerly BIM-23A760) is a chimeric dopamine (DA)-somatostatin (SST) compound with potent agonist activity at both DA type 2 (D2R) and SST type 2 (SSTR2) receptors. Studies have shown that chimeric DA-SST compounds are more efficacious than individual DA and/or SST analogues, either alone or combined, in inhibiting secretion from primary cultures of human somatotroph and lactotroph tumor cells. Nonfunctioning pituitary adenomas (NFPAs) express both D2R and SSTR2 and, consequently, may respond to TBR-760. We used a mouse model with the pro-opiomelanocortin (POMC) gene knocked out that spontaneously develops aggressive NFPAs. Genomic microarray and DA and SST receptor messenger RNA expression analysis indicate that POMC KO mouse tumors and human NFPAs have similar expression profiles, despite arising from different cell lineages, establishing POMC KO mice as a model for study of NFPAs. Treatment with TBR-760 for 8 weeks resulted in nearly complete inhibition of established tumor growth, whereas tumors from vehicle-treated mice increased in size by 890 ± 0.7%. Comparing TBR-760 with its individual DA and SST components, TBR-760 arrested tumor growth. Treatment with equimolar or 10×-higher doses of the individual SST or DA agonists, either alone or in combination, had no significant effect. One exception was the lower dose of DA agonist that induced modest suppression of tumor growth. Only the chimeric compound TBR-760 arrested tumor growth in this mouse model of NFPA. Further, significant tumor shrinkage was observed in 20% of the mice treated with TBR-760. These results support the development of TBR-760 as a therapy for patients with NFPA.

Contemporary Management of Clinically Non-functioning Pituitary Adenomas: A Clinical Review

Non-functioning pituitary adenomas (NFPAs) are benign pituitary tumours that constitute about one-third of all pituitary adenomas. They typically present with symptoms of mass effects resulting in hypopituitarism, visual symptoms, or headache. Most NFPAs are macroadenomas (>1 cm in diameter) at diagnosis that can occasionally grow quite large and invade the cavernous sinus causing acute nerve compression and some patients may develop acute haemorrhage due to pituitary apoplexy. The progression from benign to malignant pituitary tumours is not fully understood; however, genetic and epigenetic abnormalities may be involved. Non-functioning pituitary carcinoma is extremely rare accounting for only 0.1% to 0.5 % of all pituitary tumours and presents with cerebrospinal, meningeal, or distant metastasis along with the absence of features of hormonal hypersecretion. Pituitary surgery through trans-sphenoidal approach has been the treatment of choice for symptomatic NFPAs; however, total resection of large macroadenomas is not always possible. Recurrence of tumours is frequent and occurs in 51.5% during 10 years of follow-up and negatively affects the overall prognosis. Adjuvant radiotherapy can decrease and prevent tumour growth but at the cost of significant side effects. The presence of somatostatin receptor types 2 and 3 (SSTR3 and SSTR2) and D2-specific dopaminergic receptors (D2R) within NFPAs has opened a new perspective of medical treatment for such tumours. The effect of dopamine agonist from pooled results on patients with NFPAs has emerged as a very promising treatment modality as it has resulted in reduction of tumour size in 30% of patients and stabilization of the disease in about 58%. Despite the lack of long-term studies on the mortality, the available limited evidence indicates that patients with NFPA have higher standardized mortality ratios (SMR) than the general population, with women particularly having higher SMR than men. Older age at diagnosis and higher doses of glucocorticoid replacement therapy are the only known predictors for increased mortality.

Targeted systemic and peptide radio-ligand therapy for aggressive pituitary tumors and carcinomas

Aggressive pituitary tumors comprise a rare but challenging subset of pituitary tumors. A major issue currently is the absence of a holistic definition that reliably identifies these tumors in a prospective manner. Although comprehensive evaluation of patient gender, age, local invasiveness, treatment responses, radiological and histopathological features may be informative to assess the potential for aggressiveness, a definitive diagnosis of this entity cannot be confidently made until disease progression is actually observed despite standard medical and surgical therapy. Failure to diagnose these aggressive pituitary tumors early may impede initiation of suitable intensive stepwise multimodal treatments, and lessen their ultimate therapeutic success. Even though current therapeutic options for aggressive pituitary tumors are suboptimal in many cases, large-scale randomized prospective clinic trials are impractical and will likely never be conducted due to the rarity of this disease entity. Therefore, the majority of novel therapies in this subset of tumors derive from case reports or small case series, which greatly reduces their validity to make strong recommendations. This chapter, as part of this series on aggressive pituitary tumors, focuses on the role of systemic targeted medical and peptide radio-receptor therapy in treatment of aggressive pituitary tumors and carcinomas, and discusses future directions in these fields.

Gonadotroph Tumors Show Subtype Differences That Might Have Implications for Therapy

Gonadotroph tumors, although frequent, are poorly studied and understood, being usually included in the larger nonfunctioning pituitary neuroendocrine tumors (PitNETs) group. Moreover, in comparison to the other types of PitNETs, no established medical treatment is currently available for gonadotroph tumors. Here, we performed a retrospective study and analyzed the clinicopathological characteristics of 98 gonadotroph tumors operated in a single large pituitary center. Although being larger in men (p = 0.01), the aggressiveness of gonadotroph tumors did not appear to be sex-related. LH tumors were rare (4/98) and exclusively encountered in men. Somatostatin receptor type 5 (SST5) was absent in all analyzed tumors. The immunoreactive score (IRS) of somatostatin receptor type 2 (SST2) and of estrogen receptor alpha (ERα) was associated with the histological subtype (p = 0.01 and p = 0.02). IRS ERα correlated moderately with IRS SST2 in all (rho = 0.44, adjusted p-value = 0.0001) and in male (rho = 0.51, adjusted p-value = 0.0002) patients, and with follicle-stimulating hormone (FSH) percentage in all (rho = 0.40, adjusted p-value = 0.0005) and in female (rho = 0.58, adjusted p-value = 0.004) patients. In conclusion, gonadotroph tumors exhibit histological characteristics pinpointing the existence of several subtypes. Their heterogeneity warrants further investigations and may have to be taken into account when studying these tumors and investigating treatment options.

Lower 68 Ga-DOTATOC uptake in nonfunctioning pituitary neuroendocrine tumours compared to normal pituitary gland-A proof-of-concept study

OBJECTIVES

⁶⁸  Ga-DOTATOC PET targets somatostatin receptors (SSTRs) and is well established for the detection of SSTR-expressing tumors, such as gastrointestinal neuroendocrine tumors. Pituitary adenomas, recently designated as pituitary neuroendocrine tumors (PitNETs), also express SSTRs, but there has been no previous evaluations of ⁶⁸  Ga-DOTATOC PET in PitNET patients. The aim of this pilot study was to evaluate the diagnostic properties of ⁶⁸  Ga-DOTATOC PET in the most common PitNET, ie non-functioning (NF)-PitNET.

DESIGN/PATIENTS

NF-PitNET patients (n = 9) and controls (n = 13) were examined preoperatively with ⁶⁸  Ga-DOTATOC PET for 45 min after tracer injection in dynamic list mode. Tumor specimens were collected during surgery in patients. MRI and PET images were co-registered using PMOD software. The maximum standard uptake value (SUV_max ) was analyzed in manually outlined regions of interest (ROI) around the tumor in patients and around the pituitary gland in controls. Immunohistochemical analyses were conducted on tumor specimens for assessment of tumor cell type and SSTR expression.

RESULTS

Median SUV_max (IQR) was lower in patients than in controls (3.9 [3.4-8.5] vs 14.1 [12.5-15.9]; P < .01]. In ROC analysis, the area under the curve was 0.87 (P < .01) for SUV_max , with 78% sensitivity and 92% specificity. Immunohistochemical analysis showed NF-PitNETs were of gonadotroph (n = 7) and corticotroph (n = 2) origin. SSTR expression was high for SSTR3, low-to-moderate for SSTR2, and low for SSTR1 and SSTR5.

CONCLUSIONS

This proof-of-concept study shows that ⁶⁸ Ga-DOTATOC PET can be used to differentiate between normal pituitary tissue and NF-PitNET.

A Somatostatin Receptor Subtype-3 (SST3) Peptide Agonist Shows Antitumor Effects in Experimental Models of Nonfunctioning Pituitary Tumors

PURPOSE

Somatostatin analogues (SSA) are efficacious and safe treatments for a variety of neuroendocrine tumors, especially pituitary neuroendocrine tumors (PitNET). Their therapeutic effects are mainly mediated by somatostatin receptors SST₂ and SST₅. Most SSAs, such as octreotide/lanreotide/pasireotide, are either nonselective or activate mainly SST₂. However, nonfunctioning pituitary tumors (NFPTs), the most common PitNET type, mainly express SST₃ and finding peptides that activate this particular somatostatin receptor has been very challenging. Therefore, the main objective of this study was to identify SST₃-agonists and characterize their effects on experimental NFPT models.

EXPERIMENTAL DESIGN

Binding to SSTs and cAMP level determinations were used to screen a peptide library and identify SST₃-agonists. Key functional parameters (cell viability/caspase activity/chromogranin-A secretion/mRNA expression/intracellular signaling pathways) were assessed on NFPT primary cell cultures in response to SST₃-agonists. Tumor growth was assessed in a preclinical PitNET mouse model treated with a SST₃-agonist.

RESULTS

We successfully identified the first SST₃-agonist peptides. SST₃-agonists lowered cell viability and chromogranin-A secretion, increased apoptosis in vitro, and reduced tumor growth in a preclinical PitNET model. As expected, inhibition of cell viability in response to SST₃-agonists defined two NFPT populations: responsive and unresponsive, wherein responsive NFPTs expressed more SST₃ than unresponsive NFPTs and exhibited a profound reduction of MAPK, PI3K-AKT/mTOR, and JAK/STAT signaling pathways upon SST₃-agonist treatments. Concurrently, SSTR3 silencing increased cell viability in a subset of NFPTs.

CONCLUSIONS

This study demonstrates that SST₃-agonists activate signaling mechanisms that reduce NFPT cell viability and inhibit pituitary tumor growth in experimental models that expresses SST₃, suggesting that targeting this receptor could be an efficacious treatment for NFPTs.

Multimodal therapy in aggressive pituitary tumors

The concept of aggressive pituitary tumor (APT) has been precisely defined in recent years. These tumors are characterized by morphological (radiological or histopathological) data of invasion, proliferative activity superior to that of typical adenomas and a clinical behavior characterized by resistance to standard therapies and frequent recurrences. The absence of cerebrospinal or distant metastases differentiates them from the pituitary carcinoma. APTs account for about 10% of all pituitary neoplasm. Proper diagnostic implies participation not only of radiological and hormonal investigation but also a thorough pathological assessment including proliferation markers and immunohistochemistry for hormones and transcription factors. Surgical resection, aiming gross total resection or tumor debulking, is the mainstay initial therapy in most patients. Most patients with APTs need more than one surgical intervention, pituitary radiation, sometimes on more than one occasion, and multiple sequential or combined medical treatments, to finally be doomed to unusual treatments, such as alkylating agents (temozolomide alone or in combination), molecular targeted therapies, or peptide receptor radionuclide therapy. Multimodal therapy, implemented by experts, preferably in specialized centers with high volume caseload, is the only way to improve the prognosis of patients with these uncommon tumors. The research needs in this area are multiple and include a greater knowledge of the molecular biology of these tumors, establishment of protocols for monitoring and sequencing of treatments, development of multicenter studies and international registries.

Splicing Machinery is Dysregulated in Pituitary Neuroendocrine Tumors and is Associated with Aggressiveness Features

Pituitary neuroendocrine tumors (PitNETs) constitute approximately 15% of all brain tumors, and most have a sporadic origin. Recent studies suggest that altered alternative splicing and, consequently, appearance of aberrant splicing variants, is a common feature of most tumor pathologies. Moreover, spliceosome is considered an attractive therapeutic target in tumor pathologies, and the inhibition of SF3B1 (e.g., using pladienolide-B) has been shown to exert antitumor effects. Therefore, we aimed to analyze the expression levels of selected splicing-machinery components in 261 PitNETs (somatotropinomas/non-functioning PitNETS/corticotropinomas/prolactinomas) and evaluated the direct effects of pladienolide-B in cell proliferation/viability/hormone secretion in human PitNETs cell cultures and pituitary cell lines (AtT-20/GH3). Results revealed a severe dysregulation of splicing-machinery components in all the PitNET subtypes compared to normal pituitaries and a unique fingerprint of splicing-machinery components that accurately discriminate between normal and tumor tissue in each PitNET subtype. Moreover, expression of specific components was associated with key clinical parameters. Interestingly, certain components were commonly dysregulated throughout all PitNET subtypes. Finally, pladienolide-B reduced cell proliferation/viability/hormone secretion in PitNET cell cultures and cell lines. Altogether, our data demonstrate a drastic dysregulation of the splicing-machinery in PitNETs that might be associated to their tumorigenesis, paving the way to explore the use of specific splicing-machinery components as novel diagnostic/prognostic and therapeutic targets in PitNETs.

Clinical and Pathological Aspects of Silent Pituitary Adenomas

CONTEXT

Silent pituitary adenomas are anterior pituitary tumors with hormone synthesis but without signs or symptoms of hormone hypersecretion. They have been increasingly recognized and represent challenging diagnostic issues.

EVIDENCE ACQUISITION

A comprehensive literature search was performed using MEDLINE and EMBASE databases from January 2000 to March 2018 with the following key words: (i) pituitary adenoma/tumor and nonfunctioning; or (ii) pituitary adenoma/tumor and silent. All titles and abstracts of the retrieved articles were reviewed, and recent advances in the field of silent pituitary adenomas were summarized.

EVIDENCE SYNTHESIS

The clinical and biochemical picture of pituitary adenomas reflects a continuum between functional and silent adenomas. Although some adenomas are truly silent, others will show some evidence of biochemical hypersecretion or could have subtle clinical signs and, therefore, can be referred to as clinically silent or "whispering" adenomas. Silent tumors seem to be more aggressive than their secreting counterparts, with a greater recurrence rate. Transcription factors for pituitary cell lineages have been introduced into the 2017 World Health Organization guidelines: steroidogenic factor 1 staining for gonadotroph lineage; PIT1 (pituitary-specific positive transcription factor 1) for growth hormone, prolactin, and TSH lineage, and TPIT for the corticotroph lineage. Prospective studies applying these criteria will establish the value of the new classification.

CONCLUSIONS

A concise review of the clinical and pathological aspects of silent pituitary adenomas was conducted in view of the new World Health Organization classification of pituitary adenomas. New classifications, novel prognostics markers, and emerging imaging and therapeutic approaches need to be evaluated to better serve this unique group of patients.

International Union of Basic and Clinical Pharmacology. CV. Somatostatin Receptors: Structure, Function, Ligands, and New Nomenclature

Somatostatin, also known as somatotropin-release inhibitory factor, is a cyclopeptide that exerts potent inhibitory actions on hormone secretion and neuronal excitability. Its physiologic functions are mediated by five G protein-coupled receptors (GPCRs) called somatostatin receptor (SST)1-5. These five receptors share common structural features and signaling mechanisms but differ in their cellular and subcellular localization and mode of regulation. SST₂ and SST₅ receptors have evolved as primary targets for pharmacological treatment of pituitary adenomas and neuroendocrine tumors. In addition, SST₂ is a prototypical GPCR for the development of peptide-based radiopharmaceuticals for diagnostic and therapeutic interventions. This review article summarizes findings published in the last 25 years on the physiology, pharmacology, and clinical applications related to SSTs. We also discuss potential future developments and propose a new nomenclature.

The Treatment of Refractory Pituitary Adenomas

Refractory pituitary adenomas (PAs) are defined as aggressive-invasive PAs characterized by a high Ki-67 index, rapid growth, frequent recurrence, and resistance to conventional treatments. It is notoriously difficult to manage refractory PAs because the efficacy of current therapeutic options is limited. The purpose of this review is to address currently employed and promising therapeutic strategies for the treatment of refractory PAs. Except for prolactinomas, neurosurgery is the first-line option, but most refractory PAs often recur or re-grow after initial surgery and require further treatments. Medical therapy, radiotherapy and re-operation are explored when surgery has failed to completely resect tumors; however, refractory PAs are usually resistant to these treatments. As a salvage treatment, temozolomide (TMZ) has shown promising results and is currently used for all types of refractory PAs. However, not all refractory PAs are responsive to TMZ treatment, and some of these PAs are resistant to TMZ. Although targeted therapies such as vascular endothelial growth factor, epidermal growth factor and mTOR inhibitors have also been used to treat refractory PAs, the effectiveness of these targeted therapies is still not known due to a lack of data from randomized prospective trials. As a novel therapeutic method, cancer immunotherapy is a promising strategy for the treatment of refractory PAs, but further preclinical research and clinical trials are needed to assess the efficacy of this new approach. In summary, early identification and a multidisciplinary approach are required to treat refractory PAs.

The role of E and N-cadherin in the postoperative course of gonadotroph pituitary tumours

PURPOSE

Gonadotroph tumours are the most abundant of the clinically silent pituitary tumours. There is a lack of reliable prognostic markers predicting their clinical course. Our aim was to determine the level of E-cadherin and N-cadherin in a cohort of clinically silent gonadotroph pituitary tumours, and compare them to the rate of reintervention.

METHODS

Tumour tissue from primary surgery was retrospectively investigated and compared with clinical data. Immunohistochemical (N = 105) and real time-qPCR (N = 85) analyses for the levels of N-cadherin and the extra- and intracellular domains of E-cadherin were performed. The immunoreactive scores (IRS) and mRNA relative quantity were compared to the rate of reintervention.

RESULTS

The tumours presented a high IRS for N-cadherin (Median 12 (IQR 12-12)) and almost no immunoreactivity for the extracellular domain of E-cadherin (Median 0 (IQR 0-0)). The membranous staining for the intracellular domain of E-cadherin varied (Median 6 (IQR 4-6). Reduced membranous expression of the intracellular domain of E-cadherin was associated with nuclear presence of the same domain. Nuclear staining for the intracellular domain of E-cadherin was associated with a lower rate of reintervention (p = 0.01).

CONCLUSION

We found that silent gonadotroph tumours presented high IRS for N-cadherin and low IRS for the extracellular domain of E-cadherin. A substantial proportion of the tumours presented nuclear staining for the intracellular domain of E-cadherin, accompanied by a reduced membranous expression of the intracellular domain of E-cadherin. Absence of nuclear staining for the intracellular domain of E-cadherin served as an independent predictor of reintervention.

Malignant transformation in non-functioning pituitary adenomas (pituitary carcinoma)

Non-functioning pituitary carcinomas (NFPC) are defined as tumours of adenophyseal origin with craniospinal or systemic dissemination, with the absence of a hormonal hypersecretion syndrome. These are a histologically heterogenous group of tumours, comprising gonadotroph, null cell, "silent" tumours of corticotroph, somatotroph or lactotroph cell lineages as well as plurihormonal Pit-1 tumours. NFPC are exceedingly rare, and hence few cases have been described. This review has identified 38 patients with NFPC reported in the literature. Recurrent invasive non-functioning pituitary adenomas (NFPA) were observed in a majority of patients. Various factors have been identified as markers of the potential for aggressive behaviour, including rapid tumour growth, growth after radiotherapy, gain or shift of hormone secretion and raised proliferative markers. Typically, there is a latency of several years from the original presentation with an NFPA to identification of metastases and only 5 cases reported with rapidly progressive malignant disease within 1 month of presentation. Therapeutic options include debulking surgery, radiation therapy and chemotherapy with temozolomide recommended as first line systemic treatment. Although long-term survivors are described, prognosis remains generally very poor (median survival 8 months). Improvements in molecular tumour profiling may assist in predicting tumour behaviour, guide therapeutic choices and identify novel therapies.

Histopathological classification of non-functioning pituitary neuroendocrine tumors

Non-functioning pituitary neuroendocrine tumors do not cause endocrine symptoms related to hypersecretion of adenohypophyseal hormones and are clinically characterized by symptoms due to growing sellar tumor mass. Histopathological classification of this tumor group has always been challenging due to their heterogeneity, limited knowledge on their biology, and diverse methodological problems. We have searched PubMed database for data related to the histopathological classification of non-functioning pituitary tumors and methods for its application. Principles of the classification and grading presented in the recently released 4th edition of the World Health Organization classification of endocrine tumors have been summarized. Based on the expression of anterior pituitary hormones and pituitary specific transcription factors, gonadotroph tumors dominate within the group of clinically non-functioning tumors, followed by corticotroph type; however, other less common types of the non-functioning tumors can be identified. Assessment of tumor cell proliferation is important to identify "high-risk adenomas." A few subtypes of non-functioning tumors belong to the category of potentially aggressive tumors, independent of the cell proliferation rate. Here, we present up to date criteria for the classification of clinically non-functioning pituitary tumors, offer a diagnostic approach for the routine clinical use, and emphasize a need for inclusion of prognostic and predictive markers in the classification.

Management of NFAs: medical treatment

INTRODUCTION

Non-functioning pituitary adenomas (NFPAs) are in general large tumors that present with symptoms secondary to local pressure on adjacent structures. Transsphenoidal surgery is the first line of treatment but residual tumor mass is often detected post-operatively. Medical therapy, in any stage of tumor management, is not well established.

METHODS

A literature search was performed to review the available data on medical treatment of NFPAs.

RESULTS

Medications investigated for the treatment of NFPAs include dopamine receptor agonists (DA) and somatostatin receptor ligands. Randomized controlled trials are lacking, but available data suggest that DA have a positive effect on tumor remnant stabilization after surgery and could be considered in this setting. Temozolomide is reserved for aggressive tumors, although future studies are required.

CONCLUSIONS

NFPA are often not amenable to complete surgical resection. Conservative follow-up after surgery is associated with a high prevalence of tumor remnant progression. DA therapy may prevent residual tumor enlargement in over 85% of these patients, with a substantial consequent reduction in the need for repeat surgery or radiation therapy. It is our view that DA treatment should be routinely considered for the management of NFPA patients with incompletely resected tumors.

Bioinformatic analysis of gene expression profiles of pituitary gonadotroph adenomas

The aim of the present study was to identify genes, microRNAs (miRNAs/miRs) or pathways associated with the development of pituitary gonadotroph adenomas. The array data of GSE23207, which included 16 samples of multiple endocrine neoplasia-associated rat pituitary homozygous mutations and 5 pituitary tissue samples from healthy rats, were downloaded from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) were analyzed prior to functional enrichment analysis and protein-protein interaction (PPI) network construction. miRNAs associated with DEGs were predicted, and an miRNA-target regulatory network was constructed. A total of 187 upregulated and 370 downregulated DEGs were identified in the pituitary gonadotroph adenoma group compared with the healthy (control) group. Cyclin-dependent kinase (Cdk) 1 exhibited the highest degree in the PPI network. The upregulated DEGs were predominately enriched in ‘neuroactive ligand-receptor interaction’ pathway, and downregulated DEGs were mainly enriched in ‘cell cycle’. The DEGs in module were predominately enriched in the ‘cell cycle’, whereas DEGs in module b and c were enriched in ‘neuroactive ligand-receptor interaction’. miR-374, −153, −145 and −33 were identified as important miRNAs in the regulation of the DEGs. Cdk1, cyclin (Ccn) A2, Ccnb1, ‘cell cycle’ and ‘neuroactive ligand-receptor interaction’ pathways may serve important roles in the development of pituitary gonadotroph adenomas; Ccna2 and Ccnb1 may contribute to this development via an effect on the ‘cell cycle’ pathway. Furthermore, miR-374 and −145 may contribute to the development of pituitary gonadotroph adenomas via regulation of the expression of target genes.

Somatostatin receptor subtype 1 as a potential diagnostic marker and therapeutic target in prostate cancer

BACKGROUND

Prostate cancer (PCa) is a highly prevalent neoplasia that is strongly influenced by the endocrine system. Somatostatin (SST) and its five receptors (sst1-5 encoded by SSTR1-5 genes) comprise a pleiotropic system present in most endocrine-related cancers, some of which are successfully treated with SST analogs. Interestingly, it has been reported that SSTR1 is overexpressed in PCa, but its regulation, functional role, and clinical implications are still poorly known.

METHODS

PCa specimens (n = 52) from biopsies and control prostates from cystoprostatectomies (n = 12), as well as in silico databases were used to evaluate SSTR1 and miRNAs expression. In vitro studies in 22Rv1 PCa cells were implemented to explore the regulation of SSTR1/sst1 by different miRNAs, and to evaluate the consequences of SSTR1/sst1 overexpression, silencing and/or activation [with the specific BIM-23926 sst1 agonist (IPSEN)] on cell-proliferation, migration, signaling-pathways, and androgen-signaling.

RESULTS

We found that SSTR1 is overexpressed in multiple cohorts of PCa samples, as compared with normal prostate tissues, wherein it correlates with androgen receptor (AR) expression, and appears to be associated with aggressiveness (metastasis). Furthermore, our data revealed that SSTR1/sst1 expression might be regulated by specific miRNAs in PCa, including miR-24, which is downregulated in PCa samples and correlates inversely with SSTR1 expression. In vitro studies indicated that treatment with the BIM-23926 sst1 agonist, as well as SSTR1 overexpression, decreased, whereas SSTR1 silencing increased, cell-proliferation in 22Rv1 cells, likely through the regulation of PI3K/AKT-CCND3 signaling-pathway. Importantly, sst1 action was also able to modulate androgen/AR activity, and reduced PSA secretion from PCa cell lines.

CONCLUSIONS

Altogether, our results indicate that SSTR1 is overexpressed in PCa, where it can exert a relevant pathophysiological role by decreasing cell-proliferation and PSA secretion. Therefore, sst1, possibly in combination with miR-24, could be used as a novel tool to explore therapeutic targets in PCa.

Estrogen Receptor α, a Sex-Dependent Predictor of Aggressiveness in Nonfunctioning Pituitary Adenomas: SSTR and Sex Hormone Receptor Distribution in NFPA

CONTEXT

Nonfunctioning pituitary adenomas (NFPAs) are fairly common and require a multidisciplinary approach. Reliable markers of a clinically aggressive course are lacking. Medical treatment is not available, and transsphenoidal surgery is the preferred primary treatment.

OBJECTIVE

We aimed to characterize the somatostatin, estrogen, and progesterone receptor distribution for NFPAs and compare it with factors of tumor aggressiveness.

DESIGN

Tumor samples for immunohistochemistry (n = 145) and quantitative reverse transcription polymerase chain reaction (n = 106) analyses of somatostatin receptor (SSTR) 1, SSTR2, SSTR3, SSTR5, estrogen receptor α (ERα), and progesterone receptor (PR) were measured by immunoreactive score (IRS) and messenger RNA relative quantity and retrospectively compared with variables of aggressiveness.

SETTING

All patients were operated at the same tertiary referral center.

PARTICIPANTS

A total of 164 patients with NFPA and tumor tissue from the primary operation were included.

RESULTS

SSTR3 was expressed abundantly by immunohistochemistry in all NFPAs. The IRS of ERα correlated with that of SSTR2 in male patients only (males, P < 0.001; females, P = 0.8). Low ERα level was linked to a higher reintervention rate (P = 0.001) and earlier reintervention (P = 0.004) in male patients only (females, P = 0.95 and P = 0.65, respectively). Absence of ERα together with age provided a good prediction model for reintervention in male patients with gonadotroph adenomas.

CONCLUSIONS

SSTR3 is expressed abundantly in NFPAs and is therefore a possible target for medical treatment. Absence of ERα together with young age may predict tumor recurrence in groups of NFPAs. Further validation in systematic prospective studies is needed.

18F-Fluorodeoxyglucose uptake on positron emission tomography/computed tomography is associated with metastasis and epithelial-mesenchymal transition in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth leading cause of cancer mortality worldwide. Several studies have investigated the relationship between ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) uptake on positron emission tomography and the prognosis of patients with HCC, although the relationship between ¹⁸F-FDG uptake and expression of EMT-related proteins in these patients remains unclear. We retrospectively enrolled 116 patients with HCC treated by curative surgical resection and who underwent ¹⁸F-FDG positron emission tomography/computed tomography (PET/CT) for preoperative staging. The relationship between the tumor-to-liver standardized uptake value ratio (TLR) and the presence of metastasis was determined. By using HCC cell lines with different ¹⁸F-FDG uptake, we assessed the effect of ¹⁸F-FDG uptake on in vitro cell proliferation and migration on the inhibition of glucose uptake. Ten (29.4%) of 34 patients with high TLRs had extrahepatic metastases, whereas six (7.3%) of 82 patients with low TLRs had extrahepatic metastases (p = 0.002). Hepatocellular carcinomas with high TLRs showed higher expression of glucose transporter isoform 1 and EMT markers than did HCCs with low TLRs. After treatment with a glucose uptake inhibitor, HCC cells with high ¹⁸F-FDG uptake showed decreased cell proliferation and migration and a reversal in the expression of EMT markers. High ¹⁸F-FDG uptake on PET/CT is associated with frequent extrahepatic metastasis and EMT in patients with HCC. Inhibition of glucose uptake reduced cell proliferation, reversed EMT-related protein expression, and decreased cellular migration. Glycolytic regulation could be a new therapeutic target to reduce tumor growth and metastatic potential in HCCs with a high glycolytic phenotype.

Oncogenic features of the bone morphogenic protein 7 (BMP7) in pheochromocytoma

BMP7 is a growth factor playing pro- or anti-oncogenic roles in cancer in a cell type-dependent manner. We previously reported that the BMP7 gene is overexpressed in pheochromocytomas (PCCs) developing in MENX-affected rats and human patients. Here, analyzing a large cohort of PCC patients, we found that 72% of cases showed elevated levels of the BMP7 protein. To elucidate the role of BMP7 in PCC, we modulated its levels in PCC cell lines (overexpression in PC12, knockdown in MPC and MTT cells) and conducted functional assays. Active BMP signaling promoted cell proliferation, migration, and invasion, and sustained survival of MENX rat primary PCC cells. In PCC, BMP7 signals through the PI3K/AKT/mTOR pathway and causes integrin β1 up-regulation. Silencing integrin β1 in PC12 cells suppressed BMP7-mediated oncogenic features. Treatment of MTT cells with DMH1, a novel BMP antagonist, suppressed proliferation and migration. To verify the clinical applicability of our findings, we evaluated a dual PI3K/mTOR inhibitor (NVP-BEZ235) in MENX-affected rats in vivo. PCCs treated with NVP-BEZ235 had decreased proliferation and integrin β1 levels, and higher apoptosis. Altogether, BMP7 activates pro-oncogenic pathways in PCC. Downstream effectors of BMP7-mediated signaling may represent novel targets for treating progressive/inoperable PCC, still orphan of effective therapy.

Suction Filter in Endoscopic Endonasal Surgery: A Technical Note

BACKGROUND

The collection of the greatest possible amount of pathologic tissue is of paramount importance in neurosurgery to achieve the most accurate histopathologic diagnosis, to perform all of the necessary biomolecular tests on the pathologic specimen, and to collect biological material for basic or translational science studies. This problem is particularly relevant in pituitary surgery because of the possible small size and soft consistency of tumors, which make them suitable for removal through suction, reducing the amount of available pathologic tissue. To solve this issue, we adopted a filter connected to the suction tube, which allows the surgeon to collect all of the tissue aspirated during surgery.

METHODS

Our experience of 1734 endoscopic endonasal procedures, performed adopting this device since 1998 to December 2015, has been revised to assess its advantages and limitations.

RESULTS

This system is easy-to-use, does not impair the surgical maneuvers, and does not add any relevant cost to the surgery. The tissue collected through the filter proved useful for diagnostic histologic and biomolecular analyses and for research purposes, without any relevant artifacts as a result of this method of collection.

CONCLUSIONS

The use of a filter has allowed us to obtain the greatest amount possible of pathologic tissue at each surgery. This surgical material has revealed to be helpful both for diagnostic and basic science purposes. The use of the filter has proven to be of particular importance for microadenomas, soft tumors, and supradiaphragmatic or skull base lesions with heterogeneous features, improving the accuracy of histopathologic diagnosis.

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.

Non-functioning pituitary adenomas: growth and aggressiveness

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

Identification of Phosphorylation Sites Regulating sst3 Somatostatin Receptor Trafficking

The human somatostatin receptor 3 (sst3) is expressed in about 50% of all neuroendocrine tumors and hence a promising target for multireceptor somatostatin analogs. The sst3 receptor is unique among ssts in that it exhibits a very long intracellular C-terminal tail containing a huge number of potential phosphate acceptor sites. Consequently, our knowledge about the functional role of the C-terminal tail in sst3 receptor regulation is very limited. Here, we have generated a series of phosphorylation-deficient mutants that enabled us to determine crucial sites for its agonist-induced β-arrestin mobilization, internalization, and down-regulation. Based on this information, we generated phosphosite-specific antibodies for C-terminal Ser(337)/Thr(341), Thr(348), and Ser(361) that enabled us to investigate the temporal patterns of sst3 phosphorylation and dephosphorylation. We found that the endogenous ligand somatostatin induced a rapid and robust phosphorylation that was completely blocked by the sst3 antagonist NVP-ACQ090. The stable somatostatin analogs pasireotide and octreotide promoted clearly less phosphorylation compared with somatostatin. We also show that sst3 phosphorylation occurred within seconds to minutes, whereas dephosphorylation of the sst3 receptor occurred at a considerable slower rate. In addition, we also identified G protein-coupled receptor kinases 2 and 3 and protein phosphatase 1α and 1β as key regulators of sst3 phosphorylation and dephosphorylation, respectively. Thus, we here define the C-terminal phosphorylation motif of the human sst3 receptor that regulates its agonist-promoted phosphorylation, β-arrestin recruitment, and internalization of this clinically relevant receptor.

Aggressive Pituitary Tumors or Localized Pituitary Carcinomas: Defining Pituitary Tumors

Pituitary tumors are common and exhibit a wide spectrum of hormonal, proliferative and invasive behaviors. Traditional classifications consider them malignant only when they exhibit metastasis. Patients who suffer morbidity and mortality from aggressive tumors classified as "adenomas" are denied support provided to patients with "cancers" and in many jurisdictions, these tumors are considered curiosities that do not warrant reporting in health registries. We propose use of the term "tumor" rather than "adenoma" to align with other neuroendocrine tumors. The features that can serve as diagnostic, prognostic and predictive markers are reviewed. Clinico-pathological and radiographic classifications provide important information and to date, no single biomarker has been able to offer valuable insight to guide the management of patients with pituitary tumors.