Comprehensive analysis of the immunological landscape of pituitary adenomas: implications of immunotherapy for pituitary adenomas

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.

The biological behavior and clinical outcome of pituitary adenoma are affected by the microenvironment

BACKGROUND

Pituitary adenoma is one of the most common brain tumors. Most pituitary adenomas are benign and can be cured by surgery and/or medication. However, some pituitary adenomas show aggressive growth with a fast growth rate and are resistant to conventional treatments such as surgery, drug therapy, and radiation therapy. These tumors, referred to as refractory pituitary adenomas, often relapse or regrow in the early postoperative period. The tumor microenvironment (TME) has recently been identified as an important factor affecting the biological manifestations of tumors and acts as the main battlefield between the tumor and the host immune system.

MAIN BODY

In this review, we focus on describing TME in pituitary adenomas and refractory pituitary adenomas. Research on the immune microenvironment of pituitary adenomas is currently focused on immune cells such as macrophages and lymphocytes, and extensive research and experimental verifications are still required regarding other components of the TME. In particular, studies are needed to determine the role of the TME in the specific biological behaviors of refractory pituitary adenomas, such as high invasion, fast recurrence rate, and high tolerance to traditional treatments and to identify the mechanisms involved.

CONCLUSION

Overall, we summarize the similarities and differences between the TME of pituitary adenomas and refractory pituitary adenomas as well as the changes in the biological behavior of pituitary adenomas that may be caused by the microenvironment. These changes greatly affect the outcome of patients.

The Immune Microenvironment Landscape of Pituitary NeuroEndocrine Tumors, a Transcriptomic Approach

Pituitary neuroendocrine tumors (PitNET) are known to be variably infiltrated by different immune cells. Nonetheless, their role in pituitary oncogenesis has only begun to be unveiled. The immune microenvironment could determine the biological and clinical behavior of a neoplasm and may have prognostic implications. To evaluate the expression of immune-related genes and to correlate such expression with the presence of infiltrating immune cells in forty-two PitNETs of different lineages, we performed whole transcriptome analysis and RT-qPCR. Deconvolution analysis was carried out to infer the immune cell types present in each tumor and the presence of immune cells was confirmed by immunofluorescence. We found characteristic expression profiles of immune-related genes including those encoding interleukins and chemokines for each tumor lineage. Genes such as IL4-I1, IL-36A, TIRAP, IL-17REL, and CCL5 were upregulated in all PitNETS, whereas IL34, IL20RA, and IL-2RB characterize the NR5A1-, TBX19-, and POU1F1-derived tumors, respectively. Transcriptome deconvolution analysis showed that M2 macrophages, CD4+ T cells, CD8+ T cells, NK cells, and neutrophils can potentially infiltrate PitNET. Furthermore, CD4+ and CD8+ T cells and NK cells infiltration was validated by immunofluorescence. Expression of CCL18, IL-5RA, and HLA-B as well as macrophage tumor infiltration could identify patients who can potentially benefit from treatment with immune checkpoint inhibitors.

Single-cell transcriptomics reveal distinct immune-infiltrating phenotypes and macrophage-tumor interaction axes among different lineages of pituitary neuroendocrine tumors

BACKGROUND

Pituitary neuroendocrine tumors (PitNETs) are common gland neoplasms demonstrating distinctive transcription factors. Although the role of immune cells in PitNETs has been widely recognized, the precise immunological environment and its control over tumor cells are poorly understood.

METHODS

The heterogeneity, spatial distribution, and clinical significance of macrophages in PitNETs were analyzed using single-cell RNA sequencing (scRNA-seq), bulk RNA-seq, spatial transcriptomics, immunohistochemistry, and multiplexed quantitative immunofluorescence (QIF). Cell viability, cell apoptosis assays, and in vivo subcutaneous xenograft experiments have confirmed that INHBA-ACVR1B influences the process of tumor cell apoptosis.

RESULTS

The present study evaluated scRNA-seq data from 23 PitNET samples categorized into 3 primary lineages. The objective was to explore the diversity of tumors and the composition of immune cells across these lineages. Analyzed data from scRNA-seq and 365 bulk RNA sequencing samples conducted in-house revealed the presence of three unique subtypes of tumor immune microenvironment (TIME) in PitNETs. These subtypes were characterized by varying levels of immune infiltration, ranging from low to intermediate to high. In addition, the NR5A1 lineage is primarily associated with the subtype characterized by limited infiltration of immune cells. Tumor-associated macrophages (TAMs) expressing CX3CR1+, C1Q+, and GPNMB+ showed enhanced contact with tumor cells expressing NR5A1 + , TBX19+, and POU1F1+, respectively. This emphasizes the distinct interaction axes between TAMs and tumor cells based on their lineage. Moreover, the connection between CX3CR1+ macrophages and tumor cells via INHBA-ACVR1B regulates tumor cell apoptosis.

CONCLUSIONS

In summary, the different subtypes of TIME and the interaction between TAM and tumor cells offer valuable insights into the control of TIME that affects the development of PitNET. These findings can be utilized as prospective targets for therapeutic interventions.

PitNETs and the gut microbiota: potential connections, future directions

The role of the gut microbiome has been widely discussed in numerous works of literature. The biggest concern is the association of the gut microbiome with the central nervous system through the microbiome-brain-gut axis in the past ten years. As more and more research has been done on the relationship between the disease of the central nervous system and gut microbes. This fact is being revealed that gut microbes seem to play an important role from the onset and progression of the disease to clinical symptoms, and new treatments. As a special tumor of the central nervous system, pituitary neuroendocrine tumors (PitNETs)are closely related to metabolism, endocrinology, and immunity. These factors are the vectors through which intestinal microbes interact with the central nervous system. However, little is known about the effects of gut microbes on the PitNET. In this review, the relationship of gut microbiota in PitNETs is introduced, the potential effects of the gut-brain axis in this relationship are analyzed, and future research directions are presented.

Prognostic Biomarkers in Pituitary Tumours: A Systematic Review

Pituitary tumours (PTs) are the second most common intracranial tumour. Although the majority show benign behaviour, they may exert aggressive behaviour and can be resistant to treatment. The aim of this review is to report the recently identified biomarkers that might have possible prognostic value. Studies evaluating potentially prognostic biomarkers or a therapeutic target in invasive/recurrent PTs compared with either non-invasive or non-recurrent PTs or normal pituitaries are included in this review. In the 28 included studies, more than 911 PTs were evaluated. A systematic search identified the expression of a number of biomarkers that may be positively correlated with disease recurrence or invasion in PT, grouped according to role: (1) insensitivity to anti-growth signals: minichromosome maintenance protein 7; (2) evasion of the immune system: cyclooxygenase 2, arginase 1, programmed cell death protein 1 (PD-1)/programmed death ligand 2, cluster of differentiation (CD) 80/CD86; (3) sustained angiogenesis: endothelial cell-specific molecule, fibroblast growth factor receptor, matrix metalloproteinase 9, pituitary tumour transforming gene; (4) self-sufficiency in growth signals: epidermal growth factor receptor; and (5) tissue invasion: matrix metalloproteinase 9, fascin protein. Biomarkers with a negative correlation with disease recurrence or invasion include: (1) insensitivity to anti-growth signals: transforming growth factor β1, Smad proteins; (2) sustained angiogenesis: tissue inhibitor of metalloproteinase 1; (3) tissue invasion: Wnt inhibitory factor 1; and (4) miscellaneous: co-expression of glial fibrillary acidic protein and cytokeratin, and oestrogen receptors α36 and α66. PD-1/programmed cell death ligand 1 showed no clear association with invasion or recurrence, while cyclin A, cytotoxic T lymphocyte-associated protein 4, S100 protein, ephrin receptor, galectin-3 , neural cell adhesion molecule, protein tyrosine phosphatase 4A3 and steroidogenic factor 1 had no association with invasion or recurrence of PT. With the aim to develop a more personalized approach to the treatment of PT, and because of the limited number of molecular targets currently studied in the context of recurrent PT and invasion, a better understanding of the most relevant of these biomarkers by well-d esigned interventional studies will lead to a better understanding of the molecular profile of PT. This should also meet the increased need of treatable molecular targets.

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.

Identification of biomarkers associated with the invasion of nonfunctional pituitary neuroendocrine tumors based on the immune microenvironment

Introduction

The invasive behavior of nonfunctioning pituitary neuroendocrine tumors (NF-PitNEts) affects complete resection and indicates a poor prognosis. Cancer immunotherapy has been experimentally used for the treatment of many tumors, including pituitary tumors. The current study aimed to screen the key immune-related genes in NF-PitNEts with invasion.

Methods

We used two cohorts to explore novel biomarkers in NF-PitNEts. The immune infiltration-associated differentially expressed genes (DEGs) were obtained based on high/low immune scores, which were calculated through the ESTIMATE algorithm. The abundance of immune cells was predicted using the ImmuCellAI database. WGCNA was used to construct a coexpression network of immune cell-related genes. Random forest analysis was used to select the candidate genes associated with invasion. The expression of key genes was verified in external validation set using quantitative real-time polymerase chain reaction (qRT‒PCR).

Results

The immune and invasion related DEGs was obtained based on the first dataset of NF-PitNEts (n=112). The immune cell-associated modules in NF-PitNEts were calculate by WGCNA. Random forest analysis was performed on 81 common genes intersected by immune-related genes, invasion-related genes, and module genes. Then, 20 of these genes with the highest RF score were selected to construct the invasion and immune-associated classification model. We found that this model had high prediction accuracy for tumor invasion, which had the largest area under the receiver operating characteristic curve (AUC) value in the training dataset from the first dataset (n=78), the self-test dataset from the first dataset (n=34), and the independent test dataset (n=73) (AUC=0.732/0.653/0.619). Functional enrichment analysis revealed that 8 out of the 20 genes were enriched in multiple signaling pathways. Subsequently, the 8-gene (BMP6, CIB2, FABP5, HOMER2, MAML3, NIN, PRKG2 and SIDT2) classification model was constructed and showed good efficiency in the first dataset (AUC=0.671). In addition, the expression levels of these 8 genes were verified by qRT‒PCR.

Conclusion

We identified eight key genes associated with invasion and immunity in NF-PitNEts that may play a fundamental role in invasive progression and may provide novel potential immunotherapy targets for NF-PitNEts.

PD-L1 and tumor-infiltrating CD8+ lymphocytes are correlated with clinical characteristics in pediatric and adolescent pituitary adenomas

Objective

To investigate the levels of tumor-infiltrating CD8⁺ lymphocytes (CD8⁺ TILs) and the expression of programmed cell death receptor ligand 1 (PD-L1) in the tumor microenvironment (TME) of pediatric and adolescent pituitary adenomas (PAPAs) and analyze the correlation between their levels and the clinical characteristics.

Methods

A series of 43 PAPAs cases were enrolled over a period of 5 years. To compare the TME of PAPAs and adult PAs, 43 PAPAs cases were matched with 60 adult PAs cases (30 cases were between 20 and 40 years old, and 30 cases were older than 40 years) for main clinical characteristics. The expression of immune markers in PAPAs was detected by immunohistochemistry, and their correlation with the clinical outcomes was analyzed using statistical methods.

Results

In the PAPAs group, CD8⁺ TILs level was significantly lower (3.4 (5.7) vs. 6.1 (8.5), p = 0.001), and PD-L1 expression (0.040 (0.022) vs. 0.024 (0.024), p < 0.0001) was significantly higher as compared with the older group. The level of CD8⁺ TILs was negatively correlated with the expression of PD-L1 (r = -0.312, p = 0.042). Moreover, CD8⁺ TILs and PD-L1 levels were associated with Hardy (CD8, p = 0.014; PD-L1, p = 0.018) and Knosp (CD8, p = 0.02; PD-L1, p = 0.017) classification. CD8⁺ TILs level was associated with high-risk adenomas (p = 0.015), and it was associated with the recurrence of PAPAs (HR = 0.047, 95% CI 0.003-0.632, p = 0.021).

Conclusion

Compared with the TME in adult PAs, the TME in PAPAs was found to express a significantly altered level of CD8⁺ TILs and PD-L1. In PAPAs, CD8⁺ TILs and PD-L1 levels were associated with clinical characteristics.

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 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.

A novel risk model based on the correlation between the expression of basement membrane genes and immune infiltration to predict the invasiveness of pituitary adenomas

Objective

Invasive pituitary adenomas (IPAs) are common tumors of the nervous system tumors for which invasive growth can lead to difficult total resection and a high recurrence rate. The basement membrane (BM) is a special type of extracellular matrix and plays an important role in the invasion of pituitary adenomas (PAs). The aim of this study was to develop a risk model for predicting the invasiveness of PAs by analyzing the correlation between the expression of BM genes and immune infiltration.

Methods

Four datasets, featuring samples IPAs and non-invasive pituitary adenomas (NIPAs), were obtained from the Gene Expression Omnibus database (GEO). R software was then used to identify differentially expressed genes (DEGs) and analyze their functional enrichment. Protein-protein interaction (PPI) network was used to screen BM genes, which were analyzed for immune infiltration; this led to the generation of a risk model based on the correlation between the expression of BM genes and immunity. A calibration curve and receiver operating characteristic (ROC) curve were used to evaluate and validate the model. Subsequently, the differential expression levels of BM genes between IPA and NIPA samples collected in surgery were verified by Quantitative Polymerase Chain Reaction (qPCR) and the prediction model was further evaluated. Finally, based on our analysis, we recommend potential drug targets for the treatment of IPAs.

Results

The merged dataset identified 248 DEGs that were mainly enriching in signal transduction, the extracellular matrix and channel activity. The PPI network identified 11 BM genes from the DEGs: SPARCL1, GPC3, LAMA1, SDC4, GPC4, ADAMTS8, LAMA2, LAMC3, SMOC1, LUM and THBS2. Based on the complex correlation between these 11 genes and immune infiltration, a risk model was established to predict PAs invasiveness. Calibration curve and ROC curve analysis (area under the curve [AUC]: 0.7886194) confirmed the good predictive ability of the model. The consistency between the qPCR results and the bioinformatics results confirmed the reliability of data mining.

Conclusion

Using a variety of bioinformatics methods, we developed a novel risk model to predict the probability of PAs invasion based on the correlation between 11 BM genes and immune infiltration. These findings may facilitate closer surveillance and early diagnosis to prevent or treat IPAs in patients and improve the clinical awareness of patients at high risk of IPAs.

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.

Immune-checkpoint inhibitors in pituitary malignancies

To date, there are no standardized systemic treatment options for patients with metastatic pituitary carcinoma progressed to chemo and radiation therapy. Immune-checkpoint inhibitors (ICIs) have been successfully assessed in other solid malignancies and could be a concrete hope for these patients. We performed a critical review of the literature aimed to evaluate studies assessing ICIs in pituitary malignancies. We also conducted research about published translational data assessing immune-contexture in these malignancies. Some preliminary reports reported a successful administration of pembrolizumab or the combination between nivolumab and ipilimumab in patients with metastatic ACTH-secreting pituitary carcinomas. Translational data suggest that adenomas secreting growth hormone and ACTH have a suppressed immune-microenvironment, which could be more likely to benefit from ICIs. Immune-checkpoint inhibitors can be an effective treatment in patients with pituitary carcinoma and maybe also recurrent adenoma. Tumors secreting growth hormone and ACTH are more likely to benefit from ICIs due to a different immune-microenvironment.

The intestinal flora of patients with GHPA affects the growth and the expression of PD-L1 of tumor

Context

Pituitary adenoma (PA) is a common intracranial tumor. The evidence indicates that the tumor immune microenvironment (TIME) is associated with PA and that the intestinal flora influences other tumors' growth through interacting with the TIME. However, how the intestinal microbial flora contributes to the development of PA through the immune response is unknown.

Objective and methods

Here we used high-throughput Illumina MiSeq sequencing targeting the V3−V4 region of the 16S ribosomal RNA gene to investigate the intestinal flora of patients with growth hormone-secreting pituitary adenoma (GHPA), nonfunctional pituitary adenoma (NFPA), and healthy controls. We determined their effects on tumor growth and the TIME. Fecal microbiota transplantation (FMT) was performed after adoptive transfer via peripheral blood mononuclear cells to tumor-bearing nude mice, which allowed the study of the immune response.

Result

We discovered differences in the structures and quantities of intestinal flora between patients with GHPA, patients with NFPA, and healthy controls. After FMT, the intestinal flora of GHPA patients promoted the growth of tumors in mouse models. The number of programmed cell death ligand 1 (PD-L1)-positive cells increased in tumor tissues as well as the extent of infiltration of CD8⁺ cells. Increased numbers of CD3⁺CD8⁺ cells and increased levels of sPD-L1 were detected in peripheral blood.

Conclusion

These findings indicated that the intestinal flora of patients with GHPA promoted tumor growth and that the immune system may mediate this change.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00262-021-03080-6.

Immune Checkpoints: Therapeutic Targets for Pituitary Tumors

Pituitary tumors are the third most common intracranial tumors in adults. Treatment of refractory pituitary tumors is known to be difficult due to limited treatment options. As a promising therapeutic method, tumor immunotherapy has been applied in the treatment of many tumors, including pituitary tumors. Immune checkpoint blocking is one of the effective strategies to activate antitumor immunity. Immune checkpoints prevent tissue damage by regulating the immune response of peripheral tissues and participate in the maintenance of a normal immune environment. In the presence of a tumor, inhibition of T cell activity by tumor cells binding to immune checkpoints and their ligands is an important mechanism for tumor cells to escape immune injury. In this review, we summarize the latest findings of immune checkpoints and their potential as immunotherapeutic targets for pituitary tumors.

Research advances on the immune research and prospect of immunotherapy in pituitary adenomas

Background

Pituitary adenomas are one type of intracranial tumor, which can be divided into microadenoma (≤ 1 cm), macroadenoma (> 1 cm), and giant adenoma (≥ 4 cm) according to their diametral sizes. They are benign, typically slow-progressing, whereas the biological behavior of some of them is invasive, which presents a major clinical challenge. Treatment of some pituitary adenomas is still difficult due to drug resistance or multiple relapses, usually after surgery, medication, and radiation. At present, no clear prediction and treatment biomarkers have been found in pituitary adenomas and some of them do not cause clinical symptoms, so patients are often found to be ill through physical examination, and some are even found through autopsy. With the development of research on pituitary adenomas, the immune response has become a hot spot and may serve as a novel disease marker and therapeutic target.

The distribution and function of immune cells and their secreted molecules in pituitary adenomas are extremely complex. Researchers found that infiltration of immune cells may have a positive effect on the treatment and prognosis of pituitary adenomas. In this review, we summarized the advance of tumor immunity in pituitary adenomas, revealing the immunity molecules as potential biomarkers as well as therapeutic agents for pituitary adenomas.

Conclusion

The immune studies related to pituitary adenomas may help us find relevant immune markers. At the same time, the exploration of immunotherapy also provides new options for the treatment of pituitary adenomas.

Large Scale Molecular Studies of Pituitary Neuroendocrine Tumors: Novel Markers, Mechanisms and Translational Perspectives

Simple Summary

Pituitary neuroendocrine tumors are non-cancerous tumors of the pituitary gland, that may overproduce hormones leading to serious health conditions or due to tumor size cause chronic headache, vertigo or visual impairment. In recent years pituitary neuroendocrine tumors are studied with the latest molecular biology methods that simultaneously investigate a large number of factors to understand the mechanisms of how these tumors develop and how they could be diagnosed or treated. In this review article, we have studied literature reports, compiled information and described molecular factors that could affect the development and clinical characteristics of pituitary neuroendocrine tumors, discovered factors that overlap between several studies using large scale molecular analysis and interpreted the potential involvement of these factors in pituitary tumor development. Overall, this study provides a valuable resource for understanding the biology of pituitary neuroendocrine tumors.

Abstract

Pituitary neuroendocrine tumors (PitNETs) are non-metastatic neoplasms of the pituitary, which overproduce hormones leading to systemic disorders, or tumor mass effects causing headaches, vertigo or visual impairment. Recently, PitNETs have been investigated in large scale (exome and genome) molecular analyses (transcriptome microarrays and sequencing), to uncover novel markers. We performed a literature analysis on these studies to summarize the research data and extrapolate overlapping gene candidates, biomarkers, and molecular mechanisms. We observed a tendency in samples with driver mutations (GNAS, USP8) to have a smaller overall mutational rate, suggesting driver-promoted tumorigenesis, potentially changing transcriptome profiles in tumors. However, direct links from drivers to signaling pathways altered in PitNETs (Notch, Wnt, TGF-β, and cell cycle regulators) require further investigation. Modern technologies have also identified circulating nucleic acids, and pinpointed these as novel PitNET markers, i.e., miR-143-3p, miR-16-5p, miR-145-5p, and let-7g-5p, therefore these molecules must be investigated in the future translational studies. Overall, large-scale molecular studies have provided key insight into the molecular mechanisms behind PitNET pathogenesis, highlighting previously reported molecular markers, bringing new candidates into the research field, and reapplying traditional perspectives to newly discovered molecular mechanisms.

Tumor-Associated Macrophages: New Horizons for Pituitary Adenoma Researches

Macrophages are one of the most common infiltrating immune cells and an essential component of tumor microenvironment. Macrophages and the soluble cytokines and chemokines produced play an important role in tumorigenesis, progression, invasion and metastasis in solid tumors. Despite the multiple studies in other solid tumors, there is little known about macrophages in pituitary adenomas. Recently, studies about pituitary adenoma-infiltrated macrophages have been emerging, including the immunohistochemical and immunophenotypic analysis of the pituitary adenomas and further studies into the mechanism of the crosstalk between macrophages and tumor cells in vivo and in vitro. These studies have offered us new insights into the polarization of macrophages and its role in tumorigenesis, progression and invasion of pituitary adenomas. This review describes the advances in the field of pituitary adenoma-infiltrated macrophages and the prospect of targeting macrophages as cancer therapy in pituitary adenoma.