Transcriptome and methylome analysis reveals three cellular origins of pituitary tumors

Mesenchymal Stem Cells Induce an Immunosuppressive Microenvironment in Pituitary Tumors

CONTEXT

The tumor microenvironment (TME) includes diverse cellular components such as mesenchymal stem cells (MSCs) and immune cells, among others. MSC have been isolated from different tumors and they favor tumor cell growth; however, their role in pituitary tumors (PTs) remains unknown.

OBJECTIVE

Herein we report the presence of MSCs in 2 adrenocorticotropin (ACTH)-secreting PTs causing Cushing disease (MCU), 2 nonfunctioning adenomas of gonadotrope differentiation (MNF), and 2 nontumoral pituitary glands (MS).

METHODS

We have analyzed the transcriptomic profiles by RNA sequencing and compared MSCs in terms of their immunosuppressive effects against lymphoid T-cell and macrophage populations by means of cocultures and flow cytometry.

RESULTS

Our transcriptomic analysis revealed molecular differences between MSCs derived from nontumoral pituitaries and MSCs derived from PTs. Two distinct subpopulations of MSC emerged: one displaying immunosuppressive properties and the other with increased proproliferative capabilities, regardless of their origin. MSCs derived from ACTH- and nonfunctioning PTs, but not those derived from nontumoral glands, significantly inhibited the proliferation of activated T cells, favored the generation of regulatory T cells, and promoted M2 macrophage polarization. Such immunosuppressive effects were correlated with an upregulation of programmed death ligand 1 and intracellular expression of macrophage colony-stimulating factor (M-CSF) and interleukin-10. Importantly, MSC derived from ACTH-PTs showed a higher immunosuppressive potential than MSC isolated from nonfunctioning tumors.

CONCLUSION

This study demonstrates the presence of at least 2 MSC subpopulations in the pituitary gland and suggests that immunosuppressive effects of MSCs may have important implications in PT growth.

The 2022 WHO classification of tumors of the pituitary gland: An update on aggressive and metastatic pituitary neuroendocrine tumors

The vast majority of pituitary neuroendocrine tumors (PitNETs) are benign and slow growing with a low relapse rate over many years after surgical resection. However, about 40% are locally invasive and may not be surgically cured, and about one percentage demonstrate an aggressive clinical behavior. Exceptionally, these aggressive tumors may metastasize outside the sellar region to the central nervous system and/or systemically. The 2017 (4th Edition) WHO Classification of Pituitary Tumors abandoned the terminology "atypical adenoma" for tumors previously considered to have potential for a more aggressive behavior since its prognostic value was not established. The 2022 (5th Edition) WHO Classification of the Pituitary Tumors emphasizes the concept that morphological features distinguish indolent tumors from locally aggressive ones, however, the proposed histological subtypes are not consistent with the real life clinical characteristics of patients with aggressive tumors/carcinomas. So far, no single clinical, radiological or histological parameter can determine the risk of growth or malignant progression. Novel promising molecular prognostic markers, such as mutations in ATRX, TP53, SF3B1, and epigenetic DNA modifications, will need to be verified in larger tumor cohorts. In this review, we provide a critical analysis of the WHO guidelines for prognostic stratification and diagnosis of aggressive and metastatic PitNETs. In addition, we discuss the new WHO recommendations for changing ICD-O and ICD-11 codes for PitNET tumor behavior from a neoplasm either "benign" or "unspecified, borderline, or uncertain behavior" to "malignant" neoplasm regardless of the clinical presentation, histopathological subtype, and tumor location. We encourage multidisciplinary initiatives for integrated clinical, histological and molecular classification, which would enable early recognition of these challenging tumors and initiation of more appropriate and aggressive treatments, ultimately improving the outcome.

Longitudinal multiomics analysis of aggressive pituitary neuroendocrine tumors: comparing primary and recurrent tumors from the same patient, reveals genomic stability and heterogeneous transcriptomic profiles with alterations in metabolic pathways

Pituitary neuroendocrine tumors (PitNET) represent the vast majority of sellar masses. Some behave aggressively, growing rapidly and invading surrounding tissues, with high rates of recurrence and resistance to therapy. Our aim was to establish patterns of genomic, transcriptomic and methylomic evolution throughout time in primary and recurrent tumors from the same patient. Therefore, we performed transcriptome- and exome-sequencing and methylome microarrays of aggressive, primary, and recurrent PitNET from the same patient. Primary and recurrent tumors showed a similar exome profile, potentially indicating a stable genome over time. In contrast, the transcriptome of primary and recurrent PitNET was dissimilar. Gonadotroph, silent corticotroph, as well as metastatic corticotroph and a somatotroph PitNET expressed genes related to fatty acid biosynthesis and metabolism, phosphatidylinositol signaling, glycerophospholipid and phospholipase D signaling, respectively. Diacylglycerol kinase gamma (DGKG), a key enzyme in glycerophospholipid metabolism and phosphatidylinositol signaling pathways, was differentially expressed between primary and recurrent PitNET. These alterations did not seem to be regulated by DNA methylation, but rather by several transcription factors. Molecular docking showed that dasatinib, a small molecule tyrosine kinase inhibitor used in the treatment of chronic lymphocytic and acute lymphoblastic leukemia, could target DGKG. Dasatinib induced apoptosis and decreased proliferation in GH3 cells. Our data indicate that pituitary tumorigenesis could be driven by transcriptomically heterogeneous clones, and we describe alternative pharmacological therapies for aggressive and recurrent PitNET.

Grading and staging for pituitary neuroendocrine tumors

Pituitary adenoma/pituitary neuroendocrine tumors (PitNETs) are the second most common primary intracranial tumor and the most frequent neuroendocrine tumors/neoplasms of the human body. Thus, they are one of the most frequent diagnoses in neuropathologist's practise. 2022 5th edition WHO Classification of Endocrine and Neuroendocrine Tumors does not support a grading and/or staging system for PitNETs and argues that histological typing and subtyping are more robust than proliferation rate and invasiveness to stratify tumors. Numerous studies suggest the existence of clinically relevant molecular subgroups encouraging an integrated histo-molecular approach to the diagnosis of PitNETs to deepen the understanding of their biology and overcome the unresolved problem of grading system. The present review illustrates the main issues involved in establishing a grading and a staging system, as well as alternative systems validated by independent series to date. The state of art of the current histological and molecular markers is detailed, demonstrating that a standardized and reproducible clinico-pathological approach, combined with the integration of molecular data may help build a workflow to refine the definition of PitNETs with 'malignant potential' and most importantly, avoid delay in patient treatment. Next molecular studied are needed to validate an integrated histo-molecular grading for PitNETs.

Immune landscape and progress in immunotherapy for pituitary neuroendocrine tumors

Pituitary neuroendocrine tumors (pitNETs) are the second most common primary brain tumors. Despite their prevalence, the tumor immune microenvironment (TIME) and its clinical implications remain largely unexplored. This review provides a comprehensive overview of current knowledge on the immune landscape and advancements in targeted immunotherapy for pitNETs. Macrophages and T cells are principal immune infiltrates within the TIME. Different subtypes of pitNETs display distinct immune patterns, influencing tumor progressive behaviors. PD-L1, the most extensively studied immune checkpoint, is prominently expressed in hormonal pitNETs and correlates with tumor growth and invasion. Cytokines and chemokines including interleukins, CCLs, and CXCLs have complex correlations with tumor subtypes and immune cell infiltration. Crosstalk between macrophages and pitNET cells highlights bidirectional regulatory roles, suggesting potential macrophage-targeted strategies. Recent preclinical studies have demonstrated the efficacy of anti-PD-L1 therapy in a mouse model of corticotroph pitNET. Moreover, anti-PD-1 and/or anti-CTLA-4 immunotherapy has been applied globally in 28 cases of refractory pitNETs, showing more favorable responses in pituitary carcinomas than aggressive pitNETs. In conclusion, the TIME of pitNETs represents a promising avenue for targeted immunotherapy and warrants further investigation.

Genome-Wide DNA Methylation Profiling as a Prognostic Marker in Pituitary Adenomas-A Pilot Study

BACKGROUND

The prediction of the regrowth potential of pituitary adenomas after surgery is challenging. The genome-wide DNA methylation profiling of pituitary adenomas may separate adenomas into distinct methylation classes corresponding to histology-based subtypes. Specific genes and differentially methylated probes involving regrowth have been proposed, but no study has linked this epigenetic variance with regrowth potential and the clinical heterogeneity of nonfunctioning pituitary adenomas. This study aimed to investigate whether DNA methylation profiling can be useful as a clinical prognostic marker.

METHODS

A DNA methylation analysis by Illumina's MethylationEPIC array was performed on 54 pituitary macroadenomas from patients who underwent transsphenoidal surgery during 2007-2017. Twelve patients were excluded due to an incomplete postoperative follow-up, degenerated biobank-stored tissue, or low DNA methylation quality. For the quantitative measurement of the tumor regrowth rate, we conducted a 3D volumetric analysis of tumor remnant volume via annual magnetic resonance imaging. A linear mixed effects model was used to examine whether different DNA methylation clusters had different regrowth patterns.

RESULTS

The DNA methylation profiling of 42 tissue samples showed robust DNA methylation clusters, comparable with previous findings. The subgroup of 33 nonfunctioning pituitary adenomas of an SF1-lineage showed five subclusters with an approximately unbiased score of 86%. There were no overall statistically significant differences when comparing hazard ratios for regrowth of 100%, 50%, or 0%. Despite this, plots of correlated survival estimates suggested higher regrowth rates for some clusters. The mixed effects model of accumulated regrowth similarly showed tendencies toward an association between specific DNA methylation clusters and regrowth potential.

CONCLUSION

The DNA methylation profiling of nonfunctioning pituitary adenomas may potentially identify adenomas with increased growth and recurrence potential. Larger validation studies are needed to confirm the findings from this explorative pilot study.

The molecular biology of sporadic acromegaly

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

Association between Intracellular Calcium Signaling and Tumor Recurrence in Human Non-Functioning Pituitary Adenomas

Clinically non-functioning pituitary adenomas (CNFPAs) are the second most frequent sellar tumor among studies on community-dwelling adults. They are characterized by the absence of hormonal hypersecretion syndrome, and patients present with compressive symptoms, such as a headache and visual field defects. Immunohistochemically, most CNFPAs are of gonadotrope differentiation, with only a few of them being truly null cell adenomas. Although these tumors express receptors for one or more hypothalamic releasing hormones, to what extent this has an impact on the biological and clinical behavior of these neoplasms remains to be defined. In this research, we evaluated the basal and hypothalamic secretagogue-stimulated intracellular calcium mobilization in 13 CNFPAs, trying to correlate this response to the phenotypic features of the patients. Our results indicate that the recurrence of a CNFPA correlates positively with cellular responsiveness, as measured by spontaneous intracellular calcium activity and the ability to respond to multiple hypothalamic secretagogues. We conclude that this finding may be a useful tool for predicting the clinicopathologic behavior of CNFPAs, by testing the variation of cellular responsiveness to hypothalamic secretagogues.

Transcriptome Analysis Reveals Distinct Patterns Between the Invasive and Noninvasive Pituitary Neuroendocrine Tumors

Although most pituitary neuroendocrine tumors (PitNETs)/pituitary adenomas remain intrasellar, a significant proportion of tumors show parasellar invasive growth and 6% to 8% infiltrate the bone structures, thus affecting the prognosis. There is an unmet need to identify novel markers that can predict the parasellar growth of PitNETs. Furthermore, mechanisms that regulate bone invasiveness of PitNETs and factors related to tumor vascularization are largely unknown. We used genome-wide mRNA analysis in a cohort of 77 patients with PitNETs of different types to explore the differences in gene expression patterns between invasive and noninvasive tumors with respect to the parasellar growth and regarding the rare phenomenon of bone invasiveness. Additionally, we studied the genes correlated to the contrast enhancement quotient, a novel radiological parameter of tumor vascularization. Most of the genes differentially expressed related to the parasellar growth were genes involved in tumor invasiveness. Differentially expressed genes associated with bone invasiveness are involved in NF-κB pathway and antitumoral immune response. Lack of clear clustering regarding the parasellar and bone invasiveness may be explained by the influence of the cell lineage-related genes in this heterogeneous cohort of PitNETs. Our transcriptomics analysis revealed differences in the molecular fingerprints between invasive, including bone invasive, and noninvasive PitNETs, although without clear clustering. The contrast enhancement quotient emerged as a radiological parameter of tumor vascularization, correlating with several angiogenesis-related genes. Several of the top genes related to the PitNET invasiveness and vascularization have potential prognostic and therapeutic application requiring further research.

Erythropoietin-producing hepatocellular receptor B6 is highly expressed in non-functioning pituitary neuroendocrine tumors and its expression correlates with tumor size

BACKGROUND

Erythropoietin-producing hepatocellular (EPH) receptors are the largest known family of receptor tyrosine kinases characterized in humans. These proteins are involved in tissue organization, synaptic plasticity, vascular development and the progression of various diseases including cancer. The Erythropoietin-producing hepatocellular receptor tyrosine kinase member EphB6 is a pseudokinase which has not attracted an equivalent amount of interest as its enzymatically-active counterparts. The aim of this study was to assess the expression of EphB6 in pituitary tumors.

METHODS AND RESULTS

Human normal pituitaries and pituitary tumors were examined for EphB6 mRNA expression using real-time PCR and for EphB6 protein by immunohistochemistry and Western blotting. EphB6 was highly expressed in non-functioning pituitary neuroendocrine tumors (NF-PitNETs) versus the normal pituitary and GH-secreting PitNETs. EphB6 mRNA expression was correlated with tumor size.

CONCLUSIONS

Our results suggest EphB6 aberrant expression in NF-PitNETs. Future studies are warranted to determine the role and significance of EphB6 in NF-PitNETs tumorigenesis.

Pituitary neuroendocrine tumors with PIT1/SF1 co-expression show distinct clinicopathological and molecular features

Pituitary neuroendocrine tumors (PitNETs) are classified according to cell lineage, which requires immunohistochemistry for adenohypophyseal hormones and the transcription factors (TFs) PIT1, SF1, and TPIT. According to the current WHO 2022 classification, PitNETs with co-expression of multiple TFs are termed "plurihormonal". Previously, PIT1/SF1 co-expression was prevailingly reported in PitNETs, which otherwise correspond to the somatotroph lineage. However, little is known about such tumors and the WHO classification has not recognized their significance. We compiled an in-house case series of 100 tumors, previously diagnosed as somatotroph PitNETs. Following TF staining, histopathological features associated with PIT1/SF1 co-expression were assessed. Integration of in-house and publicly available sample data allowed for a meta-analysis of SF1-associated clinicopathological and molecular features across a total of 270 somatotroph PitNETs. The majority (74%, 52/70) of our densely granulated somatotroph PitNETs (DGST) unequivocally co-expressed PIT1 and SF1 (DGST-PIT1/SF1). None (0%, 0/30) of our sparsely granulated somatotroph PitNETs (SGST) stained positive for SF1 (SGST-PIT1). Among DGST, PIT1/SF1 co-expression was significantly associated with scarce FSH/LH expression and fewer fibrous bodies compared to DGST-PIT1. Integrated molecular analyses including publicly available samples confirmed that DGST-PIT1/SF1, DGST-PIT1 and SGST-PIT1 represent distinct tumor subtypes. Clinicopathological meta-analyses indicated that DGST-PIT1 respond more favorably towards treatment with somatostatin analogs compared to DGST-PIT1/SF1, while both these subtypes show an overall less aggressive clinical course than SGST-PIT1. In this study, we spotlight that DGST with co-expression of PIT1 and SF1 represent a common, yet underrecognized, distinct PitNET subtype. Our study questions the rationale of generally classifying such tumors as "plurihormonal", and calls for a refinement of the WHO classification. We propose the term "somatogonadotroph PitNET".

Implications of cellular senescence in paediatric pituitary tumours

The long-standing view of senescent cells as passive and dysfunctional biological remnants has recently shifted into a new paradigm where they are main players in the development of many diseases, including cancer. The senescence programme represents a first line of defence that prevents tumour cell growth but also leads to the secretion of multiple pro-inflammatory and pro-tumourigenic factors that fuel tumour initiation, growth, and progression. Here, we review the main molecular features and biological functions of senescent cells in cancer, including the outcomes of inducing or targeting senescence. We discuss evidence on the role of cellular senescence in pituitary tumours, with an emphasis on adamantinomatous craniopharyngioma (ACP) and pituitary adenomas. Although senescence has been proposed to be a tumour-preventing mechanism in pituitary adenomas, research in ACP has shown that senescent cells are tumour-promoting in both murine models and human tumours. Future studies characterizing the impact of targeting senescent cells may result in novel therapies against pituitary tumours.

From Genes to Therapy: Pituitary Adenomas in the Era of Precision Medicine

This review presents a comprehensive analysis of pituitary adenomas, a type of brain tumor with diverse behaviors and complexities. We cover various treatment approaches, including surgery, radiotherapy, chemotherapy, and their integration with newer treatments. Key to the discussion is the role of biomarkers in oncology for risk assessment, diagnosis, prognosis, and the monitoring of pituitary adenomas. We highlight advances in genomic, epigenomic, and transcriptomic analyses and their contributions to understanding the pathogenesis and molecular pathology of these tumors. Special attention is given to the molecular mechanisms, including the impact of epigenetic factors like histone modifications, DNA methylation, and transcriptomic changes on different subtypes of pituitary adenomas. The importance of the tumor immune microenvironment in tumor behavior and treatment response is thoroughly analyzed. We highlight potential breakthroughs and innovations for a more effective management and treatment of pituitary adenomas, while shedding light on the ongoing need for research and development in this field to translate scientific knowledge into clinical advancements, aiming to improve patient outcomes.

Genomics, Transcriptomics, and Epigenetics of Sporadic Pituitary Tumors

Pituitary tumors (PT) are highly heterogeneous neoplasms, comprising functioning and nonfunctioning lesions. Functioning PT include prolactinomas, causing amenorrhea-galactorrhea in women and sexual dysfunction in men; GH-secreting adenomas causing acromegaly-gigantism; ACTH-secreting corticotrophinomas causing Cushing disease (CD); and the rare TSH-secreting thyrotrophinomas that result in central hyperthyroidism. Nonfunctioning PT do not result in a hormonal hypersecretion syndrome and most of them are of gonadotrope differentiation; other non-functioning PT include null cell adenomas and silent ACTH-, GH- and PRL-adenomas. Less than 5% of PT occur in a familial or syndromic context whereby germline mutations of specific genes account for their molecular pathogenesis. In contrast, the more common sporadic PT do not result from a single molecular abnormality but rather emerge from several oncogenic events that culminate in an increased proliferation of pituitary cells, and in the case of functioning tumors, in a non-regulated hormonal hypersecretion. In recent years, important advances in the understanding of the molecular pathogenesis of PT have been made, including the genomic, transcriptomic, epigenetic, and proteomic characterization of these neoplasms. In this review, we summarize the available molecular information pertaining the oncogenesis of PT.

Role of Tumor Microenvironment in Pituitary Neuroendocrine Tumors: New Approaches in Classification, Diagnosis and Therapy

Adenohypophysal pituitary tumors account for 10-15% of all intracranial tumors, and 25-55% display signs of invasiveness. Nevertheless, oncology still relies on histopathological examination to establish the diagnosis. Considering that the classification of pituitary tumors has changed significantly in recent years, we discuss the definition of aggressive and invasive tumors and the latest molecular criteria used for classifying these entities. The pituitary tumor microenvironment (TME) is essential for neoplastic development and progression. This review aims to reveal the impact of TME characteristics on stratifying these tumors in view of finding appropriate therapeutic approaches. The role of the pituitary tumor microenvironment and its main components, non-tumoral cells and soluble factors, has been addressed. The variable display of different immune cell types, tumor-associated fibroblasts, and folliculostellate cells is discussed in relation to tumor development and aggressiveness. The molecules secreted by both tumoral and non-tumoral cells, such as VEGF, FGF, EGF, IL6, TNFα, and immune checkpoint molecules, contribute to the crosstalk between the tumor and its microenvironment. They could be considered potential biomarkers for diagnosis and the invasiveness of these tumors, together with emerging non-coding RNA molecules. Therefore, assessing this complex network associated with pituitary neuroendocrine tumors could bring a new era in diagnosing and treating this pathology.

Oxidative stress in pituitary neuroendocrine tumors: Affecting the tumor microenvironment and becoming a new target for pituitary neuroendocrine tumor therapy

Pituitary adenomas (PAs), or pituitary neuroendocrine tumors (PitNETs), are commonly found in the anterior pituitary gland. Although the majority of PitNETs are benign and stable, several tumors have malignant characteristics. The tumor microenvironment (TME) plays an important role in the process of tumorigenesis and is composed of several types of cells. Various cells in the TME are significantly affected by oxidative stress. It has been reported that immunotherapeutic strategies have good effects in several cancers. However, the clinical potential of immunotherapies in PitNETs has not yet been fully discussed. Oxidative stress can regulate PitNET cells and immune cells in the TME, thus affecting the immune status of the TME of PitNETs. Therefore, modulation of oxidative stress-regulated immune cells using a combination of several agents and the immune system to suppress PitNETs is a promising therapeutic direction. In this review, we systematically analyzed the oxidative stress process within PitNET cells and various immune cells to elucidate the potential value of immunotherapy.

Tumour microenvironment and pituitary tumour behaviour

The pituitary tumour microenvironment encompasses a spectrum of non-tumoural cells, such as immune, stromal or endothelial cells, as well as enzymes and signalling peptides like cytokines, chemokines and growth factors, which surround the tumour cells and may influence pituitary tumour behaviour and tumourigenic mechanisms. Recently, there has been intensive research activity in this field describing various pituitary tumour-infiltrating immune and stromal cell subpopulations, and immune- and microenvironment-related pathways. Key changes in oncological therapeutic avenues resulted in the recognition of pituitary as a target of adverse events for patients treated with immune checkpoint regulators. However, these phenomena can be turned into therapeutic advantage in severe cases of pituitary tumours. Therefore, unravelling the pituitary tumour microenvironment will allow a better understanding of the biology and behaviour of pituitary tumours and may provide further developments in terms of diagnosis and management of patients with aggressively growing or recurrent pituitary tumours.

The hallmarks of cancer… in pituitary tumors?

Over 20 years ago, Hanahan and Weinberg published a seminal review that addressed the biological processes that underly malignant transformation. This classical review, along with two revisions published in 2011 and 2022, has remain a classic of the oncology literature. Since many of the addressed biological processes may apply to non-malignant tumorigenesis, we evaluated to what extent these hallmarks pertain to the development of pituitary adenomas.Some of the biological processes analyzed in this review include genome instability generated by somatic USP8 and GNAS mutations in Cushing's diseases and acromegaly respectively; non-mutational epigenetic reprograming through changes in methylation; induction of angiogenesis through alterations of VEGF gene expression; promotion of proliferative signals mediated by EGFR; evasion of growth suppression by disrupting cyclin dependent kinase inhibitors; avoidance of immune destruction; and the promotion of inflammation mediated by alteration of gene expression of immune check points. We also elaborate further on the existence of oncogene induced senescence in pituitary tumors. We conclude that a better understanding of these processes can help us dilucidated why pituitary tumors are so resistant to malignant transformation and can potentially contribute to the development of novel anticancer treatments.

The immune microenviroment in somatotropinomas: from biology to personalized and target therapy

Pituitary tumors are rare neoplasms, with a heterogeneous biological and clinical behavior, due to their clinical course, local invasive growth, resistance to conventional therapies and the risk of disease progression. Recent studies on tumor microenvironment (TME) provided new knowledge on the biology of these neoplasia, that may explain the different phenotypes of these tumors and suggest new biomarkers able to predict the prognosis and the treatment outcome. The identification of molecular markers that act as targets for biological therapies may open new perspectives in the medical treatments of aggressive pituitary tumors.In this paper, we will review data of TME and target therapies in somatotropinomas.

The molecular biology of thyrotroph pituitary neuroendocrine tumors

Pituitary neuroendocrine tumors (PitNETs), which were formerly known as pituitary adenomas, are classified in 5th Edition of the WHO Classification of Endocrine and Neuroendocrine Tumors. Since thyrotroph PitNETs are rare PitNETs, most previous studies about former thyroid stimulating hormone (TSH)-secreting pituitary adenoma have focused on a small number of cases. However, the diagnostic rate of thyrotroph PitNET has increased because of increased sensitivity of serum TSH measurement and widespread recognition that thyrotroph PitNETs are the cause of syndrome of inappropriate secretion of TSH (SITSH). Therefore, knowledge on the molecular mechanism of thyrotroph PitNET is gradually accumulating. Recently, comprehensive chromosomal, genetic, and epigenomic alterations in thyrotroph PitNET have been revealed with the availability of comprehensive gene and protein analyses, and the nature of thyrotroph PitNET is gradually being elucidated. However, further analysis is needed to determine whether the causes of these changes are directly responsible for the development of tumors.

Single Cell Metabolic Landscape of Pituitary Neuroendocrine Tumor Subgroups and Lineages

Pituitary neuroendocrine tumors (PitNETs) are common intracranial tumors comprising numerous subtypes whose metabolic profiles have yet to be fully examined. The present in silico study analyzed single-cell expression profiles from 2311 PitNET cells from various lineages and subtypes to elucidate differences in metabolic activities. Gonadotroph tumors exhibited high activities with histidine metabolism, whose activity is low in lactotroph tumors. Somatotroph tumors enriched for sulfur and tyrosine metabolism, while lactotroph tumors were enriched metabolism of nitrogen, ascorbate, and aldarate. PIT-1 lineage tumors exhibited high sulfur and thiamine metabolism. These results set precedence for further translational studies for subgroup/lineage specific targeted therapies.

Transcriptome of GH-producing pituitary neuroendocrine tumours and models are significantly affected by somatostatin analogues

Pituitary neuroendocrine tumours (PitNETs) are neoplasms of the pituitary that overproduce hormones or cause unspecific symptoms due to mass effect. Growth hormone overproducing GH-producing PitNETs cause acromegaly leading to connective tissue, metabolic or oncologic disorders. The medical treatment of acromegaly is somatostatin analogues (SSA) in specific cases combined with dopamine agonists (DA), but almost half of patients display partial or full SSA resistance and potential causes of this are unknown. In this study we investigated transcriptomic landscape of GH-producing PitNETs on several levels and functional models-tumour tissue of patients with and without SSA preoperative treatment, tumour derived pituispheres and GH3 cell line incubated with SSA to study effect of medication on gene expression. MGI sequencing platform was used to sequence total RNA from PitNET tissue, pituispheres, mesenchymal stromal stem-like cells (MSC), and GH3 cell cultures, and data were analysed with Salmon-DeSeq2 pipeline. We observed that the GH-producing PitNETs have distinct changes in growth hormone related pathways related to its functional status alongside inner cell signalling, ion transport, cell adhesion and extracellular matrix characteristic patterns. In pituispheres model, treatment regimens (octreotide and cabergoline) affect specific cell proliferation (MKI67) and core functionality pathways (RYR2, COL8A2, HLA-G, ARFGAP1, TGFBR2). In GH3 cells we observed that medication did not have transcriptomic effects similar to preoperative treatment in PitNET tissue or pituisphere model. This study highlights the importance of correct model system selection for cell transcriptomic profiling and data interpretation that could be achieved in future by incorporating NGS methods and detailed cell omics profiling in PitNET model research.

Integrating methylome and transcriptome signatures expands the molecular classification of the pituitary tumors

PURPOSE

To explore pituitary tumors by methylome and transcriptome signatures in a heterogeneous ethnic population.

DESIGN

Retrospective cross-sectional study.

PATIENTS AND METHODS

Clinicopathological features, methylome and transcriptome were evaluated in pituitary tumors from 77 patients (61% women, age: 12-72 years) followed due to functioning (FPT: GH-secreting n = 18, ACTH-secreting n = 14) and non-functioning pituitary tumors (NFPT, n = 45) at Ribeirao Preto Medical School, University of Sao Paulo.

RESULTS

Unsupervised hierarchical clustering analysis (UHCA) of methylome (n = 77) and transcriptome (n = 65 out of 77) revealed three clusters each: one enriched by FPT, other by NFPT, and another by ACTH-secreting and NFPT. Comparison between each omics-derived clusters identified 3,568 and 5,994 differentially methylated and expressed genes, respectively, which were associated with each other, with tumor clinical presentation, and with 2017 and 2022 WHO classifications. UHCA considering 11 transcripts related to pituitary development/differentiation also supported three clusters: POU1F1-driven somatotroph, TBX19-driven corticotroph, and NR5A1-driven gonadotroph adenomas, with rare exceptions (NR5A1 expressed in few GH-secreting and corticotroph-silent adenomas; POU1F1 in few ACTH-secreting adenomas; and TBX19 in few NFPTs).

CONCLUSIONS

This large heterogenic ethnic Brazilian cohort confirms that integrated methylome and transcriptome signatures classify FPT and NFPT, which are associated with clinical presentation and tumor invasiveness. Moreover, the cluster NFPT/ACTH-secreting adenomas raises interest regarding tumor heterogeneity, supporting the challenge raised by the 2017 and 2022 WHO definition regarding the discrepancy, in rare cases, between clinical presentation and pituitary lineage markers. Finally, making our data publicly available enables further studies to validate genes/pathways involved in pituitary tumor pathogenesis and prognosis.

Novel neoplasms associated with syndromic pediatric medulloblastoma: integrated pathway delineation for personalized therapy

Medulloblastoma is the most common pediatric embryonal brain tumor, and may occur in cancer predisposition syndromes. We describe novel associations of medulloblastoma with atypical prolactinoma and dural high-grade sarcoma in Li-Fraumeni syndrome (LFS), and epidural desmoid fibromatosis in familial adenomatous polyposis (FAP)/Turcot syndrome. Genomic analysis showing XRCC3 alterations suggested radiotherapy as contributing factor to the progression of LFS-associated medulloblastoma, and demonstrated different mechanisms of APC inactivation in the FAP-associated tumors. The integrated genomic-transcriptomic analysis uncovered the growth pathways driving tumorigenesis, including the prolactin-prolactin receptor (PRLR) autocrine loop and Shh pathway in the LFS-associated prolactinoma and medulloblastoma, respectively, the Wnt pathway in both FAP-associated neoplasms, and the TGFβ and Hippo pathways in the soft tissue tumors, regardless of germline predisposition. In addition, the comparative analysis of paired syndromic neoplasms revealed several growth pathways susceptible to therapeutic intervention by PARP, PRLR, and selective receptor tyrosine kinase (RTK) inhibitors. These could target the defective DNA damage repair in the LFS-associated medulloblastoma, the prolactin autocrine loop in the atypical prolactinoma, the EPHA3/7 and ALK overexpression in the FAP-associated medulloblastoma, and the multi-RTK upregulation in the soft tissue neoplasms. This study presents the spatiotemporal evolution of novel neoplastic associations in syndromic medulloblastoma, and discusses the post-radiotherapy risk for secondary malignancies in syndromic pediatric patients, with important implications for the biology, diagnosis, and therapy of these tumors. Video Abstract.

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.

The microenvironment of pituitary adenomas: biological, clinical and therapeutical implications

The microenvironment of pituitary adenomas (PAs) includes a range of non-tumoral cells, such as immune and stromal cells, as well as cell signaling molecules such as cytokines, chemokines and growth factors, which surround pituitary tumor cells and may modulate tumor initiation, progression, invasion, angiogenesis and other tumorigenic processes. The microenvironment of PAs has been actively investigated over the last years, with several immune and stromal cell populations, as well as different cytokines, chemokines and growth factors being recently characterized in PAs. Moreover, key microenvironment-related genes as well as immune-related molecules and pathways have been investigated, with immune check point regulators emerging as promising targets for immunotherapy. Understanding the microenvironment of PAs will contribute to a deeper knowledge of the complex biology of PAs, as well as will provide developments in terms of diagnosis, clinical management and ultimately treatment of patients with aggressive and/or refractory PAs.

The Genomic Landscape of Corticotroph Tumors: From Silent Adenomas to ACTH-Secreting Carcinomas

Corticotroph cells give rise to aggressive and rare pituitary neoplasms comprising ACTH-producing adenomas resulting in Cushing disease (CD), clinically silent ACTH adenomas (SCA), Crooke cell adenomas (CCA) and ACTH-producing carcinomas (CA). The molecular pathogenesis of these tumors is still poorly understood. To better understand the genomic landscape of all the lesions of the corticotroph lineage, we sequenced the whole exome of three SCA, one CCA, four ACTH-secreting PA causing CD, one corticotrophinoma occurring in a CD patient who developed Nelson syndrome after adrenalectomy and one patient with an ACTH-producing CA. The ACTH-producing CA was the lesion with the highest number of single nucleotide variants (SNV) in genes such as USP8, TP53, AURKA, EGFR, HSD3B1 and CDKN1A. The USP8 variant was found only in the ACTH-CA and in the corticotrophinoma occurring in a patient with Nelson syndrome. In CCA, SNV in TP53, EGFR, HSD3B1 and CDKN1A SNV were present. HSD3B1 and CDKN1A SNVs were present in all three SCA, whereas in two of these tumors SNV in TP53, AURKA and EGFR were found. None of the analyzed tumors showed SNV in USP48, BRAF, BRG1 or CABLES1. The amplification of 17q12 was found in all tumors, except for the ACTH-producing carcinoma. The four clinically functioning ACTH adenomas and the ACTH-CA shared the amplification of 10q11.22 and showed more copy-number variation (CNV) gains and single-nucleotide variations than the nonfunctioning tumors.

The kinome, cyclins and cyclin-dependent kinases of pituitary adenomas, a look into the gene expression profile among tumors from different lineages

Background

Pituitary adenomas (PA) are the second most common intracranial tumors and are classified according to hormone they produce, and the transcription factors they express. The majority of PA occur sporadically, and their molecular pathogenesis is incompletely understood.

Methods

Here we performed transcriptome and proteome analysis of tumors derived from POU1F1 (GH-, TSH-, and PRL-tumors, N = 16), NR5A1 (gonadotropes and null cells adenomas, n = 17) and TBX19 (ACTH-tumors, n = 6) lineages as well as from silent ACTH-tumors (n = 3) to determine expression of kinases, cyclins, CDKs and CDK inhibitors.

Results

The expression profiles of genes encoding kinases were distinctive for each of the three PA lineage: NR5A1-derived tumors showed upregulation of ETNK2 and PIK3C2G and alterations in MAPK, ErbB and RAS signaling, POU1F1-derived adenomas showed upregulation of PIP5K1B and NEK10 and alterations in phosphatidylinositol, insulin and phospholipase D signaling pathways and TBX19-derived adenomas showed upregulation of MERTK and STK17B and alterations in VEGFA-VEGFR, EGF-EGFR and Insulin signaling pathways. In contrast, the expression of the different genes encoding cyclins, CDK and CDK inhibitors among NR5A1-, POU1F1- and TBX19-adenomas showed only subtle differences. CDK9 and CDK18 were upregulated in NR5A1-adenomas, whereas CDK4 and CDK7 were upregulated in POUF1-adenomas.

Conclusions

The kinome of PA clusters these lesions into three distinct groups according to the transcription factor that drives their terminal differentiation. And these complexes could be harnessed as molecular therapy targets.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-022-01206-y.

Acute elevation of interleukin 6 and matrix metalloproteinase 9 during the onset of pituitary apoplexy in Cushing's disease

PURPOSE

Pituitary apoplexy is a rare endocrine emergency. The purpose of this study is to characterize physiological changes involved in pituitary apoplexy, especially during the acute phase.

METHODS

A Cushing's disease patient experienced corticotroph releasing hormone (CRH)-induced pituitary apoplexy during inferior petrosal sinus sampling (IPSS). The IPSS blood samples from the Cushing's disease patient were retrospectively analyzed for cytokine markers. For comparison, we also analyzed cytokine markers in blood samples from two pituitary ACTH-secreting microadenoma patients and one patient with an ectopic ACTH-secreting tumor.

RESULTS

Acute elevation of interleukin 6 (IL-6) and matrix metalloproteinase 9 (MMP9) was observed in the IPSS blood sample on the apoplectic hemorrhagic site of the tumor. In contrast, such a change was not observed in the blood samples from the contralateral side of the apoplexy patient and in other IPSS samples from two non-apoplexy Cushing's disease patient and a patient with ectopic Cushing's syndrome.

CONCLUSION

IL-6 and MMP9 may be involved in the acute process of pituitary apoplexy in Cushing's disease.

Annotation of pituitary neuroendocrine tumors with genome-wide expression analysis

Pituitary neuroendocrine tumors (PitNETs) are common, generally benign tumors with complex clinical characteristics related to hormone hypersecretion and/or growing sellar tumor mass. PitNETs can be classified based on the expression pattern of anterior pituitary hormones and three main transcriptions factors (TF), SF1, PIT1 and TPIT that regulate differentiation of adenohypophysial cells. Here, we have extended this classification based on the global transcriptomics landscape using tumor tissue from a well-defined cohort comprising 51 PitNETs of different clinical and histological types. The molecular profiles were compared with current classification schemes based on immunohistochemistry. Our results identified three main clusters of PitNETs that were aligned with the main pituitary TFs expression patterns. Our analyses enabled further identification of specific genes and expression patterns, including both known and unknown genes, that could distinguish the three different classes of PitNETs. We conclude that the current classification of PitNETs based on the expression of SF1, PIT1 and TPIT reflects three distinct subtypes of PitNETs with different underlying biology and partly independent from the expression of corresponding hormones. The transcriptomic analysis reveals several potentially targetable tumor-driving genes with previously unknown role in pituitary tumorigenesis.

Enhancing Gonadotrope Gene Expression Through Regulatory lncRNAs

The world of long non-coding RNAs (lncRNAs) has opened up massive new prospects in understanding the regulation of gene expression. Not only are there seemingly almost infinite numbers of lncRNAs in the mammalian cell, but they have highly diverse mechanisms of action. In the nucleus, some are chromatin-associated, transcribed from transcriptional enhancers (eRNAs) and/or direct changes in the epigenetic landscape with profound effects on gene expression. The pituitary gonadotrope is responsible for activation of reproduction through production and secretion of appropriate levels of the gonadotropic hormones. As such, it exemplifies a cell whose function is defined through changes in developmental and temporal patterns of gene expression, including those that are hormonally induced. Roles for diverse distal regulatory elements and eRNAs in gonadotrope biology have only just begun to emerge. Here, we will present an overview of the different kinds of lncRNAs that alter gene expression, and what is known about their roles in regulating some of the key gonadotrope genes. We will also review various screens that have detected differentially expressed pituitary lncRNAs associated with changes in reproductive state and those whose expression is found to play a role in gonadotrope-derived nonfunctioning pituitary adenomas. We hope to shed light on this exciting new field, emphasize the open questions, and encourage research to illuminate the roles of lncRNAs in various endocrine systems.

Pituitary Remodeling Throughout Life: Are Resident Stem Cells Involved?

The pituitary gland has the primordial ability to dynamically adapt its cell composition to changing hormonal needs of the organism throughout life. During the first weeks after birth, an impressive growth and maturation phase is occurring in the gland during which the distinct hormonal cell populations expand. During pubertal growth and development, growth hormone (GH) levels need to peak which requires an adaptive enterprise in the GH-producing somatotrope population. At aging, pituitary function wanes which is associated with organismal decay including the somatopause in which GH levels drop. In addition to these key time points of life, the pituitary's endocrine cell landscape plastically adapts during specific (patho-)physiological conditions such as lactation (need for PRL) and stress (engagement of ACTH). Particular resilience is witnessed after physical injury in the (murine) gland, culminating in regeneration of destroyed cell populations. In many other tissues, adaptive and regenerative processes involve the local stem cells. Over the last 15 years, evidence has accumulated that the pituitary gland houses a resident stem cell compartment. Recent studies propose their involvement in at least some of the cell remodeling processes that occur in the postnatal pituitary but support is still fragmentary and not unequivocal. Many questions remain unsolved such as whether the stem cells are key players in the vivid neonatal growth phase and whether the decline in pituitary function at old age is associated with decreased stem cell fitness. Furthermore, the underlying molecular mechanisms of pituitary plasticity, in particular the stem cell-linked ones, are still largely unknown. Pituitary research heavily relies on transgenic in vivo mouse models. While having proven their value, answers to pituitary stem cell-focused questions may more diligently come from a novel powerful in vitro research model, termed organoids, which grow from pituitary stem cells and recapitulate stem cell phenotype and activation status. In this review, we describe pituitary plasticity conditions and summarize what is known on the involvement and phenotype of pituitary stem cells during these pituitary remodeling events.

Proteomic and Transcriptomic Analysis Identify Spliceosome as a Significant Component of the Molecular Machinery in the Pituitary Tumors Derived from POU1F1- and NR5A1-Cell Lineages

Background: Pituitary adenomas (PA) are the second most common tumor in the central nervous system and have low counts of mutated genes. Splicing occurs in 95% of the coding RNA. There is scarce information about the spliceosome and mRNA-isoforms in PA, and therefore we carried out proteomic and transcriptomic analysis to identify spliceosome components and mRNA isoforms in PA. Methods: Proteomic profile analysis was carried out by nano-HPLC and mass spectrometry with a quadrupole time-of-flight mass spectrometer. The mRNA isoforms and transcriptomic profiles were carried out by microarray technology. With proteins and mRNA information we carried out Gene Ontology and exon level analysis to identify splicing-related events. Results: Approximately 2000 proteins were identified in pituitary tumors. Spliceosome proteins such as SRSF1, U2AF1 and RBM42 among others were found in PA. These results were validated at mRNA level, which showed up-regulation of spliceosome genes in PA. Spliceosome-related genes segregate and categorize PA tumor subtypes. The PA showed alterations in CDK18 and THY1 mRNA isoforms which could be tumor specific. Conclusions: Spliceosome components are significant constituents of the PA molecular machinery and could be used as molecular markers and therapeutic targets. Splicing-related genes and mRNA-isoforms profiles characterize tumor subtypes.