Tumor microenvironment defines the invasive phenotype of AIP-mutation-positive pituitary tumors

Lactate activates CCL18 expression via H3K18 lactylation in macrophages to promote tumorigenesis of ovarian cancer

This study investigates the role of lactate in the genesis and progression of ovarian cancer (OV) and explores the underlying mechanisms. Serum lactate levels show a positive correlation with tumor grade and poor prognosis in patients with OV. Bioinformatics analysis identifies CCL18 as a lactate-related gene in OV. CCL18 is up-regulated in cancerous tissues and positively related to serum lactate levels in OV patients. THP-1 cells are exposed to phorbol-12-myristate-13-acetate for M0 macrophage induction. The results of RT-qPCR and ELISA for M1/M2 macrophage-related markers and inflammatory cytokines show that the exposure of lactate to macrophages induces M2 polarization. Based on the coculture of OV cells with macrophages, lactate-treated macrophages induces a significant increase in the proliferation and migration of OV cells. However, these effects can be reversed by silencing of Gpr132 in macrophages or treatment with anti-CCL18 antibody. Experiments using the xenograft model verify that the oncogenic role of lactate in tumor growth and metastasis relies on Gpr132 and CCL18. ChIP-qPCR and luciferase reporter assays reveal that lactate regulates CCL18 expression via H3K18 lactylation. In conclusion, lactate is a potential therapeutic target for OV. It is involved in tumorigenesis by activating CCL18 expression via H3K18 lactylation in macrophages.

An Update on the Genetic Drivers of Corticotroph Tumorigenesis

The genetic landscape of corticotroph tumours of the pituitary gland has dramatically changed over the last 10 years. Somatic changes in the USP8 gene account for the most common genetic defect in corticotrophinomas, especially in females, while variants in TP53 or ATRX are associated with a subset of aggressive tumours. Germline defects have also been identified in patients with Cushing's disease: some are well-established (MEN1, CDKN1B, DICER1), while others are rare and could represent coincidences. In this review, we summarise the current knowledge on the genetic drivers of corticotroph tumorigenesis, their molecular consequences, and their impact on the clinical presentation and prognosis.

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.

Clinical and therapeutic implications of cavernous sinus invasion in pituitary adenomas

Invasion of the cavernous sinus by pituitary adenomas impedes complete surgical resection, compromises biochemical remission, and increases the risk of further tumor recurrence. Accurate preoperative MRI-based diagnosis or intraoperative direct inspection of cavernous sinus invasion are essential for optimal surgical planning and for tailoring postoperative therapeutic strategies, depending on whether a total resection has been achieved, or tumoral tissue has been left in surgically inaccessible locations. The molecular mechanisms underlying the invasive behavior of pituitary adenomas remain poorly understood, hindering the development of targeted therapies. Some studies have identified genes overexpressed in pituitary adenomas invading the cavernous sinus, offering insights into the acquisition of invasive behavior. Their main limitation however lies in comparing purely intrasellar specimens obtained from invasive and non-invasive adenomas. Further, precise anatomical knowledge of the medial wall of the cavernous sinus is crucial for grasping the mechanisms of invasion. Recently, alongside the standard intrasellar surgery, extended endoscopic intracavernous surgical procedures with systematic selective resection of the medial wall of the cavernous sinus have shown promising results for invasive secreting pituitary adenomas. The first- and second-generation somatostatin agonist ligands and cabergoline are used with variable efficacy to control secretory activity and/or growth of intracavernous remnants. Tumor regrowth usually requires surgical reintervention, sometimes combined with radiotherapy or radiosurgery which is applied despite their benign nature. Unraveling the molecular pathways driving invasive behavior of pituitary adenomas and their tropism to the cavernous sinuses is the key for developing efficient innovative treatment modalities that could reduce the need for repeated surgery or radiotherapy.

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.

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

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

Primary Cilia as a Tumor Marker in Pituitary Neuroendocrine Tumors

Pituitary neuroendocrine tumors (PitNETs) account for approximately 15% of all intracranial neoplasms. Although they usually appear to be benign, some tumors display worse behavior, displaying rapid growth, invasion, refractoriness to treatment, and recurrence. Increasing evidence supports the role of primary cilia (PC) in regulating cancer development. Here, we showed that PC are significantly increased in PitNETs and are associated with increased tumor invasion and recurrence. Serial electron micrographs of PITNETs demonstrated different ciliation phenotypes (dot-like versus normal-like cilia) that represented PC at different stages of ciliogenesis. Molecular findings demonstrated that 123 ciliary-associated genes (eg, doublecortin domain containing protein 2, Sintaxin-3, and centriolar coiled-coil protein 110) were dysregulated in PitNETs, representing the upregulation of markers at different stages of intracellular ciliogenesis. Our results demonstrate, for the first time, that ciliogenesis is increased in PitNETs, suggesting that this process might be used as a potential target for therapy in the future.

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.

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

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

Effects of the Cortisol Milieu on Tumor-Infiltrating Immune Cells in Corticotroph Tumors

CONTEXT

Corticotrophs are susceptible to lymphocyte cytotoxicity, as seen in hypophysitis, suggesting that an immunological approach may be a potential strategy for corticotroph-derived tumors.

OBJECTIVE

We aimed to clarify whether corticotroph tumors that induce hypercortisolemia (ACTHomas) could be targets for immunotherapy.

METHODS

Tumor-infiltrating immune cells were immunohistochemically analyzed. ACTHomas were compared with other pituitary tumors, and further divided into 3 different cortisol-exposed milieus: Naïve (ACTHomas without preoperative treatment), Met (ACTHomas with preoperative metyrapone), and SCA (silent corticotroph adenomas). A 3-dimensional cell culture of resected tumors was used to analyze the effects of immune checkpoint inhibitors.

RESULTS

The number of tumor-infiltrating lymphocytes (TILs) was low in ACTHomas. Among these, the number of CD8+ cells was lower in ACTHomas than in both somatotroph and gonadotroph tumors (both P < .01). Then we compared the differences in TILs among Naïve, Met, and SCA. The number of CD4+ cells, but not CD8+ cells, was higher in both Met and SCA than in Naïve. Next, we investigated tumor-associated macrophages, which could negatively affect T cell infiltration. The numbers of CD163+ and CD204+ cells were positively associated with cortisol levels. Moreover, tumor size was positively correlated with the number of CD204+ cells.

CONCLUSION

We found the possibility that ACTHomas were immunologically cold in a cortisol-independent manner. In contrast, the tumor infiltration of CD4+ cells and M2-macrophages were associated with the cortisol milieu. Future studies are needed to validate these results and develop effective immunotherapy while considering the cortisol milieu.

Targeting Tumor Heterogeneity with Neoantigen-Based Cancer Vaccines

Neoantigen-based cancer vaccines have emerged as a promising immunotherapeutic approach to treat cancer. Nevertheless, the high degree of heterogeneity in tumors poses a significant hurdle for developing a vaccine that targets the therapeutically relevant neoantigens capable of effectively stimulating an immune response as each tumor contains numerous unique putative neoantigens. Understanding the complexities of tumor heterogeneity is crucial for the development of personalized neoantigen-based vaccines, which hold the potential to revolutionize cancer treatment and improve patient outcomes. In this review, we discuss recent advancements in the design of neoantigen-based cancer vaccines emphasizing the identification, validation, formulation, and targeting of neoantigens while addressing the challenges posed by tumor heterogeneity. The review highlights the application of cutting-edge approaches, such as single-cell sequencing and artificial intelligence to identify immunogenic neoantigens, while outlining current limitations and proposing future research directions to develop effective neoantigen-based vaccines.

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.

Digital image analysis allows objective stratification of patients with silent PIT1-lineage pituitary neuroendocrine tumors

Studies describing the clinical presentation and prognosis of patients with silent PIT1 (pituitary specific transcription factor)-lineage pituitary neuroendocrine tumors (PitNETs) are rare. We identified patients with positive PIT1 tumor staining but without evidence of hormone hypersecretion at a tertiary center. Clusters were obtained according to cell morphology and immunostaining from each patient's digitally segmented whole slide image. We compared the clinical presentations, radiological features, and prognoses of the different clusters. We identified 146 patients (68 male, 42.9 ± 14.1 years old) with silent PIT1-lineage PitNETs. Morphology clustering suggested that tumors with large nuclei and apparent eccentricity were associated with a higher proportion of aggressiveness and a higher hazard of recurrence [hazard ratio (HR): 2.64, (95% CI, 1.06-6.55), p = 0.037]. Immunohistochemical clustering suggested that tumors with thyroid stimulating hormone (TSH) staining or all negative PIT1-lineage hormones were associated with a higher proportion of aggressiveness and a higher risk of recurrence [HR: 12.4, (95% CI, 1.60-93.5), p = 0.015]. We obtained three-tier risk profiles by combining morphological and immunohistochemical clustering. Patients with the high-risk profile presented the highest recurrence rate compared with those in the medium-risk and low-risk profiles [HR: 3.54, (95% CI, 1.40-8.93), p = 0.002]. In conclusion, digital image analysis based on cell morphology and immunohistochemical staining allows objective stratification of patients with silent PIT1-lineage tumors. Typical morphological characteristics of high-risk tumors are large tumor nuclei and high eccentricity, and typical immunostaining characteristics are TSH staining or negative staining for all PIT1-lineage hormones.

Therapeutic targeting of the pituitary tumor microenvironment

The tumor microenvironment (TME), the complex environment in which tumors develop, has been increasingly targeted for cancer treatment in recent years. Aggressive pituitary tumors and pituitary carcinomas have been so far targeted with immune-checkpoint inhibitors (28 cases, including a large cohort), and anti-angiogenic drugs (34 cases), specifically bevacizumab (30 cases), sunitinib (three cases), and apatinib (one case). Here, we reviewed all these cases, reporting tumor response, potential predictors of response, as well as adverse events. Given that the histological type could potentially influence treatment response, we present the existing data separately for each type. Briefly, under ICIs, complete response was noted in one case, partial response in a third of cases, stable disease in 10% of cases, while 54% of tumors progressed. Under BVZ monotherapy, most cases (57%) showed stable disease, while 36% of tumors progressed; partial response was reported in only one case. The three cases treated with sunitinib monotherapy progressed. Regarding predictive factors of response, the tumor type (aggressive pituitary tumor versus pituitary carcinoma) appears as the strongest predictor of response to ICIs. To date, no predictor of response to anti-angiogenic drugs in the treatment of pituitary carcinomas and aggressive pituitary tumors has been identified. The interest of BZV add-on to first- or second-line chemotherapy warrants further investigation. In addition, we discuss perspectives regarding the TME-targeting in aggressive pituitary tumors and pituitary carcinomas, including perspectives on immunotherapy, anti-angiogenic drugs, as well as on other TME components, namely stromal cells, extracellular matrix, and secreted molecules.

Cancer-associated fibroblasts facilitate breast cancer progression through exosomal circTBPL1-mediated intercellular communication

Breast cancer is the major common malignancy worldwide among women. Previous studies reported that cancer-associated fibroblasts (CAFs) showed pivotal roles in regulating tumor progression via exosome-mediated cellular communication. However, the detailed mechanism underlying the exosomal circRNA from CAFs in breast cancer progression remains ambiguous. Here, exosomal circRNA profiling of breast cancer-derived CAFs and normal fibroblasts (NFs) was detected by high-throughput sequencing, and upregulated circTBPL1 expression was identified in CAF exosomes. The exosomal circTBPL1 from CAFs could be transferred to breast cancer cells and promoted cell proliferation, migration, and invasion. Consistently, circTBPL1 knockdown in CAFs attenuated their tumor-promoting ability. Further exploration identified miR-653-5p as an inhibitory target of circTBPL1, and ectopic expression of miR-653-5p could partially reverse the malignant phenotypes induced by circTBPL1 overexpression in breast cancer. Additionally, TPBG was selected as a downstream target gene, and circTBPL1 could protect TPBG from miR-653-5p-mediated degradation, leading to enhanced breast cancer progression. Significantly, the accelerated tumor progression triggered by exosomal circTBPL1 from CAFs was confirmed in xenograft models. Taken together, these results revealed that exosomal circTBPL1 derived from CAFs contributed to cancer progression via miR-653-5p/TPBG pathway, indicating the potential of exosomal circTBPL1 as a biomarker and novel therapeutic target for breast cancer.

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.

ZNF451 favors triple-negative breast cancer progression by enhancing SLUG-mediated CCL5 transcriptional expression

Triple-negative breast cancer (TNBC) is the most aggressive subtype with limited effective therapies because of the absence of definitive targets. Here, we demonstrate that the expression of ZNF451, a poorly characterized vertebrate zinc-finger protein, is upregulated in TNBC and associated with a poor prognosis. Elevated ZNF451 expression facilitates TNBC progression by interacting with and enhancing the activity of the transcriptional activator snail family transcriptional repressor 2 (SLUG). Mechanistically, the ZNF451-SLUG complex preferentially recruits the acetyltransferase p300/CBP-associated factor (PCAF) to the CCL5 promoter, selectively facilitating CCL5 transcription by enhancing the acetylation of SLUG and local chromatin, leading to recruitment and activation of tumor-associated macrophages (TAMs). Disturbing the ZNF451-SLUG interaction using a peptide suppresses TNBC progression by reducing CCL5 expression and counteracting the migration and activation of TAMs. Collectively, our work provides mechanistic insights into the oncogene-like functions of ZNF451 and suggests that ZNF451 is a potential target for development of effective therapies against TNBC.

Pituitary Tumorigenesis-Implications for Management

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

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.

Biological and Therapeutic Implications of the Tumor Microenvironment in Pituitary Adenomas

Pituitary adenomas (PAs) are neoplasms derived from the endocrine cells of the anterior pituitary gland. Most frequently, they are benign tumors, but may sometimes display an aggressive course, and in some cases metastasize. Their biology, including their wide range of behavior, is only partly understood. In terms of therapeutic targeting, most PAs are easily treated with available medical treatments, surgery, and sometimes radiotherapy. Nevertheless, gonadotroph adenomas lack medical therapeutic options, and treatment of aggressive PAs and pituitary carcinomas remains challenging. Here, we present an overview of the implications of the tumor microenvironment in PAs, reviewing its composition and function, as well as published cases that have been treated thus far using tumor microenvironment-targeting therapies. Additionally, we discuss emerging views, such as the concept of nonangiogenic tumors, and present perspectives regarding treatments that may represent future potential therapeutic options. Tumor-infiltrating lymphocytes, tumor-associated macrophages, folliculostellate cells, tumor-associated fibroblasts, angiogenesis, as well as the extracellular matrix and its remodeling, all have complex roles in the biology of PAs. They have been linked to hormone production/secretion, size, invasion, proliferation, progression/recurrence, and treatment response in PAs. From a therapeutic perspective, immune-checkpoint inhibitors and bevacizumab have already shown a degree of efficacy in aggressive PAs and pituitary carcinomas, and the use of numerous other tumor microenvironment-targeting therapies can be foreseen. In conclusion, similar to other cancers, understanding the tumor microenvironment improves our understanding of PA biology beyond genetics and epigenetics, and constitutes an important tool for developing future therapies.

Surgical anatomic findings of sphenoid sinus in 1009 Iranian patients with pituitary adenoma undergoing endoscopic transsphenoidal surgery

OBJECTIVE

The most common surgical technique for the management of pituitary adenomas is the endoscopic endonasal transsphenoidal approach (EEA). preoperative neuroimaging along with detecting surgical landmarks of the sphenoid sinus during surgery is important for making a successful operation.

METHOD

This study includes 1009 patients with pituitary adenomas who underwent EEA between 2013 and 2020. We evaluated the anatomical features of the sphenoid sinus through a panel of items obtained from imaging and intra-operative findings.

RESULTS

Our result includes 57.38% nonfunctional, 8.42% cushing, 12.39% prolactinoma, and 21.8% acromegaly patients who had undergone endoscopic endonasal transsphenoidal surgery. The mean age of the patients was 45 with a male to female ratio of 1.2:1. Sellar sphenoid type was the most common (91.8%) with only 12% symmetrical inter sphenoid septa, Internal carotid artery dehiscence was found in 1.7% of the cases. Apoplexy was present in 6.3% of patients, which was found more prevalent in nonfunctional adenomas (9.67%, Odds ratio: 4.85, 95% CI 2.24-11.79) and further investigation revealed a significant association between apoplexy and sphenoid mucosal edema and hemorrhage (Odds ratio: 43.0, 95% CI 22.50-84.26), and between apoplexy and cystic lesions (OR = 4.14, 95% CI 1.87-8.45, P-value < 0.0001). Acromegaly is associated with the increased number of lateral recces (Odds ratio: 11.41, 95% CI 7.54-17.52), septation of the sphenoid sinus (Marginal mean: 3.92, 95% CI 3.69-4.14), edematous sinonasal mucosa (Odds ratio: 6.7; 95% CI 4.46-10.08), and higher bony (OR: 4.81, 95% CI 2.60-8.97, P-value < 0.001) and cavernous (OR: 1.7, 95% CI 1.13-2.46, P-value < 0.01) invasion.

CONCLUSION

The present study provides anatomical data about the sphenoid sinus and its adjacent vital structures with adenomal specific changes that are necessary to prevent complications during endoscopic advanced transsphenoidal surgery.

Immunotherapy in pituitary carcinomas and aggressive pituitary tumors

After temozolomide failure, no evidence-based treatment option is currently available for aggressive pituitary tumors (APTs) and pituitary carcinomas (PCs). Moreover, once temozolomide has failed, the survival of these patients is very poor. The use of immune-checkpoint inhibitors (ICIs) has been so far reported in a large cohort, a small phase 2 clinical trial, and in another five isolated cases (24 cases in total). Here, we review the available evidence on the efficacy and potential predictors of response to ICIs in PCs and APTs, namely the histological type (corticotroph versus lactotroph), the tumor type (PC versus APT), the presence of uncontrolled endogenous hypercortisolism, the type of protocol (combined ICIs versus monotherapy), programmed death-ligand 1 (PD-L1) expression, CD8+ cell infiltration, tumor mutational burden (TMB), microsatellite instability (MSI), and mismatch repair (MMR) status. We also discuss key clinical aspects that can already be implemented in the everyday practice and identify future research needs.

Molecular genetic testing in the management of pituitary disease

OBJECTIVE

Most pituitary tumours occur sporadically without a genetically identifiable germline abnormality, a small but increasing proportion present with a genetic defect that predisposes to pituitary tumour development, either isolated (e.g., aryl hydrocarbon receptor-interacting protein, AIP) or as part of a tumour-predisposing syndrome (e.g., multiple endocrine neoplasia (MEN) type 1, Carney complex, McCune-Albright syndrome or pituitary tumour and paraganglioma association). Genetic alterations in sporadic pituitary adenomas may include somatic mutations (e.g., GNAS, USP8). In this review, we take a practical approach: which genetic syndromes should be considered in case of different presentation, such as tumour type, family history, age of onset and additional clinical features of the patient.

DESIGN

Review of the recent literature in the field of genetics of pituitary tumours.

RESULTS

Genetic testing in the management of pituitary disease is recommended in a significant minority of the cases. Understanding the genetic basis of the disease helps to identify patients and at-risk family members, facilitates early diagnosis and therefore better long-term outcome and opens up new pathways leading to tumorigenesis.

CONCLUSION

We provide a concise overview of the genetics of pituitary tumours and discuss the current challenges and implications of these genetic findings in clinical practice.

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.

Aryl-hydrocarbon receptor-interacting protein regulates tumorigenic and metastatic properties of colorectal cancer cells driving liver metastasis

BACKGROUND

Liver metastasis is the primary cause of colorectal cancer (CRC)-associated death. Aryl-hydrocarbon receptor-interacting protein (AIP), a putative positive intermediary in aryl-hydrocarbon receptor-mediated signalling, is overexpressed in highly metastatic human KM12SM CRC cells and other highly metastatic CRC cells.

METHODS

Meta-analysis and immunohistochemistry were used to assess the relevance of AIP. Cellular functions and signalling mechanisms mediated by AIP were assessed by gain-of-function experiments and in vitro and in vivo experiments.

RESULTS

A significant association of high AIP expression with poor CRC patients' survival was observed. Gain-of-function and quantitative proteomics experiments demonstrated that AIP increased tumorigenic and metastatic properties of isogenic KM12C (poorly metastatic) and KM12SM (highly metastatic to the liver) CRC cells. AIP overexpression dysregulated epithelial-to-mesenchymal (EMT) markers and induced several transcription factors and Cadherin-17 activation. The former induced the signalling activation of AKT, SRC and JNK kinases to increase adhesion, migration and invasion of CRC cells. In vivo, AIP expressing KM12 cells induced tumour growth and liver metastasis. Furthermore, KM12C (poorly metastatic) cells ectopically expressing AIP became metastatic to the liver.

CONCLUSIONS

Our data reveal new roles for AIP in regulating proteins associated with cancer and metastasis to induce tumorigenic and metastatic properties in colon cancer cells driving liver metastasis.

Identification of Dysregulated Expression of G Protein Coupled Receptors in Endocrine Tumors by Bioinformatics Analysis: Potential Drug Targets?

Background: Many studies link G protein-coupled receptors (GPCRs) to cancer. Some endocrine tumors are unresponsive to standard treatment and/or require long-term and poorly tolerated treatment. This study explored, by bioinformatics analysis, the tumoral profiling of the GPCR transcriptome to identify potential targets in these tumors aiming at drug repurposing. Methods: We explored the GPCR differentially expressed genes (DEGs) from public datasets (Gene Expression Omnibus (GEO) database and The Cancer Genome Atlas (TCGA)). The GEO datasets were available for two medullary thyroid cancers (MTCs), eighty-seven pheochromocytomas (PHEOs), sixty-one paragangliomas (PGLs), forty-seven pituitary adenomas and one-hundred-fifty adrenocortical cancers (ACCs). The TCGA dataset covered 92 ACCs. We identified GPCRs targeted by approved drugs from pharmacological databases (ChEMBL and DrugBank). Results: The profiling of dysregulated GPCRs was tumor specific. In MTC, we found 14 GPCR DEGs, including an upregulation of the dopamine receptor (DRD2) and adenosine receptor (ADORA2B), which were the target of many drugs. In PGL, seven GPCR genes were downregulated, including vasopressin receptor (AVPR1A) and PTH receptor (PTH1R), which were targeted by approved drugs. In ACC, PTH1R was also downregulated in both the GEO and TCGA datasets and was the target of osteoporosis drugs. Conclusions: We highlight specific GPCR signatures across the major endocrine tumors. These data could help to identify new opportunities for drug repurposing.

Implications of Heterogeneity of Epithelial-Mesenchymal States in Acromegaly Therapeutic Pharmacologic Response

Acromegaly is caused by excess growth hormone (GH) produced by a pituitary tumor. First-generation somatostatin receptor ligands (SRLs) are the first-line treatment. Several studies have linked E-cadherin loss and epithelial-mesenchymal transition (EMT) with resistance to SRLs. Our aim was to study EMT and its relationship with SRLs resistance in GH-producing tumors. We analyzed the expression of EMT-related genes by RT-qPCR in 57 tumors. The postsurgical response to SRLs was categorized as complete response, partial response, or nonresponse if IGF-1 was normal, had decreased more than 30% without normalization, or neither of those, respectively. Most tumors showed a hybrid and variable EMT expression profile not specifically associated with SRL response instead of a defined epithelial or mesenchymal phenotype. However, high SNAI1 expression was related to invasive and SRL-nonresponsive tumors. RORC was overexpressed in tumors treated with SRLs before surgery, and this increased expression was more prominent in those cases that normalized postsurgical IGF-1 levels under SRL treatment. In conclusion, GH-producing tumors showed a heterogeneous expression pattern of EMT-related genes that would partly explain the heterogeneous response to SRLs. SNAI1 and RORC may be useful to predict response to SRLs and help medical treatment decision making.

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.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

RET signalling provides tumorigenic mechanism and tissue specificity for AIP-related somatotrophinomas

It is unclear how loss-of-function germline mutations in the widely-expressed co-chaperone AIP, result in young-onset growth hormone secreting pituitary tumours. The RET receptor, uniquely co-expressed in somatotrophs with PIT1, induces apoptosis when unliganded, while RET supports cell survival when it is bound to its ligand. We demonstrate that at the plasma membrane, AIP is required to form a complex with monomeric-intracellular-RET, caspase-3 and PKCδ resulting in PIT1/CDKN2A-ARF/p53-apoptosis pathway activation. AIP-deficiency blocks RET/caspase-3/PKCδ activation preventing PIT1 accumulation and apoptosis. The presence or lack of the inhibitory effect on RET-induced apoptosis separated pathogenic AIP variants from non-pathogenic ones. We used virogenomics in neonatal rats to demonstrate the effect of mutant AIP protein on the RET apoptotic pathway in vivo. In adult male rats altered AIP induces elevated IGF-1 and gigantism, with pituitary hyperplasia through blocking the RET-apoptotic pathway. In females, pituitary hyperplasia is induced but IGF-1 rise and gigantism are blunted by puberty. Somatotroph adenomas from pituitary-specific Aip-knockout mice overexpress the RET-ligand GDNF, therefore, upregulating the survival pathway. Somatotroph adenomas from patients with or without AIP mutation abundantly express GDNF, but AIP-mutated tissues have less CDKN2A-ARF expression. Our findings explain the tissue-specific mechanism of AIP-induced somatotrophinomas and provide a previously unknown tumorigenic mechanism, opening treatment avenues for AIP-related tumours.

Pituitary metastasis: From pathology to clinical and radiological considerations

PURPOSE

A review of the literature with respect to pituitary metastases (PM) with clinical and radiological considerations are summarized to facilitate clinical decision making in the management of PM METHODS: A review of literature associated with PM and tumour to tumour metastases in the English literature was reviewed and summarized RESULTS: Pituitary metastases account for 1.0-3.6% of all surgically treated pituitary lesions. Often identified in parallel with extensive disseminated disease, once diagnosed, the prognosis is generally poor, although survival is highly heterogeneous and dependent on the primary tumor histology. Within this anatomical region is also the observation of tumor-to-tumor metastases and collision tumours. Both the tumor macro- and microenvironment play central roles to the progression of disease with distinctive radiological features that may suggest a metastatic sellar lesion as opposed to a primary pituitary lesion. Surgical resection is the first line of therapy followed by adjuvant chemoradiotherapy and endocrinological evaluation for hormonal supplementation CONCLUSION: PMs are relatively rare but important oncological entities representing disseminated disease in the majority of cases. Careful consideration of the relevant clinical history and radiological features can aid the clinician differentiate between a metastatic lesion to the pituitary region and a primary pituitary tumor. While surgical resection is first line therapy, stereotactic radiosurgery in carefully selected patients is emerging as a viable alternative.

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.

Immune profiling of pituitary tumors reveals variations in immune infiltration and checkpoint molecule expression

PURPOSE

Pituitary tumors are the second most common primary brain tumors. Functional tumors demonstrate increased PD-L1 expression, but expression of other checkpoint regulators has not been characterized. We sought to characterize the immune microenvironment of human pituitary tumors to identify new treatment opportunities.

METHODS

72 pituitary tumors were evaluated for expression of the immune regulatory markers programmed death ligand 1 (PD-L1), programmed death ligand 2 (PD-L2), V-domain Ig suppressor of T cell activation (VISTA), lymphocyte activation gene 3 (LAG3) and tumor necrosis factor receptor superfamily member 4 (OX40) by immunohistochemistry (IHC). Lymphocyte infiltration, macrophage infiltration, and angiogenesis were analyzed using IHC. Expression of pituitary tumor initiating cell marker CD15 and mismatch repair proteins MutS protein homolog 2 (MSH2) and MutS protein homolog 6 (MSH6) was also assessed.

RESULTS

Pituitary tumors were infiltrated by macrophages and T cells, and they expressed varying levels of PD-L1, PD-L2, VISTA, LAG3, and OX40. Functional tumors and tumors with high expression of tumor stem cell markers had higher immune cell infiltration and greater expression of immunosuppressive checkpoint regulators. Increased PD-L1 and LAG3 and reduced VISTA were observed in primary tumors compared to recurrent tumors.

CONCLUSION

Immune cell infiltration and checkpoint regulator expression vary depending on functional status and presence of pituitary tumor initiating cells. Functional tumors may have a particularly immunosuppressive microenvironment. Further studies of immune checkpoint blockade of pituitary tumors, particularly functional tumors, are warranted, though combination therapy may be required.

Cytokeratin 8/18-negative somatotroph pituitary neuroendocrine tumours (PitNETs, adenomas) show variable morphological features and do not represent a clinicopathologically distinct entity

AIMS

In somatotroph pituitary neuroendocrine tumours (adenomas), a pattern of cytokeratin (CK) 18 expression is used for tumour subclassification, with possible clinical implications. Rare somatotroph tumours do not express CK 18. We aimed to characterise this subset clinically and histologically.

METHODS AND RESULTS

Clinical and pathological data for the study were derived from a previously published data set of a cohort of 110 patients with acromegaly. Data included serum levels of insulin-like growth factor 1 (IGF1), growth hormone (GH), prolactin and thyroid-stimulating hormone (TSH), tumour diameter, tumour invasion defined by Knosp grade and immunohistochemical data concerning the expression of Ki67, p53, E-cadherin, somatostatin receptor (SSTR)1, SSTR2A, SSTR3, SSTR5 and D2 dopamine receptor. Additional immunohistochemical analysis (AE1/3, CK 8/18, vimentin, neurofilament light chain, internexin-α) was performed. CK 18 was negative in 10 of 110 (9.1%) tumours. One of these tumours was immunoreactive with CK 8/18 antibody, while the remainder expressed only internexin-α intermediate filament in patterns similar to CK 18 (perinuclear fibrous bodies). CK-negative tumours showed no significant differences with respect to biochemical, radiological or pathological features. They showed significantly higher expression of SSTR2A compared to the sparsely granulated subtype and significantly lower expression of E-cadherin compared to the non-sparsely granulated subtypes of tumours. The tumours showed divergent morphology and hormonal expression: two corresponded to densely granulated tumours and three showed co-expression of prolactin and morphology of either mammosomatotroph or somatotroph-lactotroph tumours. Four tumours showed morphology and immunoprofile compatible with plurihormonal Pit1-positive tumours.

CONCLUSIONS

CK-negative somatotroph tumours do not represent a distinct subtype of somatotroph tumours, and can be further subdivided according to their morphology and immunoprofile.

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.

Lactate-induced M2 polarization of tumor-associated macrophages promotes the invasion of pituitary adenoma by secreting CCL17

Background: Lactate greatly contributes to the regulation of intracellular communication within the tumor microenvironment (TME). However, the role of lactate in pituitary adenoma (PA) invasion is unclear. In this study, we aimed to clarify the effects of lactate on the TME and the effects of TME on PA invasion.

Methods: To explore the correlation between TME acidosis and tumor invasion, LDHA and LAMP2 expression levels were quantified in invasive (n = 32) and noninvasive (n = 32) PA samples. The correlation between immune cell infiltration and tumor invasion was evaluated in 64 PAs. Critical chemokine and key signaling pathway components were detected by qPCR, Western blotting, siRNA knockdown, and specific inhibitors. The functional consequences of CCR4 signaling inhibition were evaluated in vitro and in vivo.

Results: Lactate was positively associated with PA invasion. Of the 64 PA tissues, invasive PAs were related to high infiltration of M2-like tumor-associated macrophages (TAMs) (P < 0.05). Moreover, lactate secreted from PA cells facilitated M2 polarization via the mTORC2 and ERK signaling pathways, while activated TAMs secreted CCL17 to promote PA invasion via the CCL17/CCR4/mTORC1 axis. According to univariate analysis of clinical data, high CCL17 expression was associated with larger tumor size (P = 0.0438), greater invasion (P = 0.0334), and higher susceptibility to postoperative recurrence (P = 0.0195) in human PAs.

Conclusion: This study illustrates the dynamics between PA cells and immune TME in promoting PA invasion via M2 polarization. CCL17 levels in the TME are related to the PA invasiveness and clinical prognosis, and the CCL17/CCR4/mTOCR1 axis may serve as potential therapeutic targets for Pas.

Cancer-associated fibroblasts-derived exosomal miR-3656 promotes the development and progression of esophageal squamous cell carcinoma via the ACAP2/PI3K-AKT signaling pathway

Esophageal squamous cell carcinoma (ESCC) is one of the most common gastrointestinal tumors, accounting for almost half a million deaths per year. Cancer-associated fibroblasts (CAFs) are the major constituent of the tumor microenvironment (TME) and dramatically impact ESCC progression. Recent evidence suggests that exosomes derived from CAFs are able to transmit regulating signals and promote ESCC development. In this study, we compared different the component ratios of miRNAs in exosomes secreted by CAFs in tumors and with those from normal fibroblasts (NFs) in precancerous tissues. The mRNA level of hsa-miR-3656 was significantly upregulated in the former exosomes. Subsequently, by comparing tumor cell development in vitro and in vivo, we found that the proliferation, migration and invasion capabilities of ESCC cells were significantly improved when miR-3656 was present. Further target gene analysis confirmed ACAP2 was a target gene regulated by miR-3656 and exhibited a negative regulatory effect on tumor proliferation. Additionally, the downregulation of ACAP2 triggered by exosomal-derived miR-3656 further promotes the activation of the PI3K/AKT and β-catenin signaling pathways and ultimately improves the growth of ESCC cells both in vitro and in xenograft models. These results may represent a potential therapeutic target for ESCC and provide a new basis for clinical treatment plans.

Epithelial-Mesenchymal Transition in the Resistance to Somatostatin Receptor Ligands in Acromegaly

Epithelial-mesenchymal transition (EMT) is a dynamic process by which epithelial cells loss their phenotype and acquire mesenchymal traits, including increased migratory and invasive capacities. EMT is involved in physiological processes, such as embryogenesis and wound healing, and in pathological processes such as cancer, playing a pivotal role in tumor progression and metastasis. Pituitary tumors, although typically benign, can be locally invasive. Different studies have shown the association of EMT with increased tumor size and invasion in pituitary tumors, and in particular with a poor response to Somatostatin Receptor Ligands (SRLs) treatment in GH-producing pituitary tumors, the main cause of acromegaly. This review will summarize the current knowledge regarding EMT and SRLs resistance in acromegaly and, based on this relation, will suggest new biomarkers and possible therapies to SRLs resistant tumors.

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.

Novel Insights into Pituitary Tumorigenesis: Genetic and Epigenetic Mechanisms

Substantial advances have been made recently in the pathobiology of pituitary tumors. Similar to many other endocrine tumors, over the last few years we have recognized the role of germline and somatic mutations in a number of syndromic or nonsyndromic conditions with pituitary tumor predisposition. These include the identification of novel germline variants in patients with familial or simplex pituitary tumors and establishment of novel somatic variants identified through next generation sequencing. Advanced techniques have allowed the exploration of epigenetic mechanisms mediated through DNA methylation, histone modifications and noncoding RNAs, such as microRNA, long noncoding RNAs and circular RNAs. These mechanisms can influence tumor formation, growth, and invasion. While genetic and epigenetic mechanisms often disrupt similar pathways, such as cell cycle regulation, in pituitary tumors there is little overlap between genes altered by germline, somatic, and epigenetic mechanisms. The interplay between these complex mechanisms driving tumorigenesis are best studied in the emerging multiomics studies. Here, we summarize insights from the recent developments in the regulation of pituitary tumorigenesis.

Transcriptome and methylome analysis reveals three cellular origins of pituitary tumors

Pituitary adenomas (PA) are the second most common intracranial tumors. These neoplasms are classified according to the hormone they produce. The majority of PA occur sporadically, and their molecular pathogenesis is incompletely understood. The present transcriptomic and methylomic analysis of PA revealed that they segregate into three molecular clusters according to the transcription factor driving their terminal differentiation. First cluster, driven by NR5A1, consists of clinically non-functioning PA (CNFPA), comprising gonadotrophinomas and null cell; the second cluster consists of clinically evident ACTH adenomas and silent corticotroph adenomas, driven by TBX19; and the third, POU1F1-driven TSH-, PRL- and GH-adenomas, segregated together. Genes such as CACNA2D4, EPHA4 and SLIT1, were upregulated in each of these three clusters, respectively. Pathway enrichment analysis revealed specific alterations of these clusters: calcium signaling pathway in CNFPA; renin-angiotensin system for ACTH-adenomas and fatty acid metabolism for the TSH-, PRL-, GH-cluster. Non-tumoral pituitary scRNAseq data confirmed that this clustering also occurs in normal cytodifferentiation. Deconvolution analysis identify potential mononuclear cell infiltrate in PA consists of dendritic, NK and mast cells. Our results are consistent with a divergent origin of PA, which segregate into three clusters that depend on the specific transcription factors driving late pituitary cytodifferentiation.

Immune Landscape of Pituitary Tumors Reveals Association Between Macrophages and Gonadotroph Tumor Invasion

PURPOSE

Pituitary neuroendocrine tumors (PitNETs) are frequent intracranial neoplasms that present heterogenic characteristics. Little is known about the immune cell network that exists in PitNETs and its contribution to their aggressive behavior.

METHODS

Here we combined flow cytometry, t-SNE analysis, and histological approaches to define the immune landscape of surgically resected PitNETs. Xenografts of rodent pituitary tumor cells and resected PitNETs were performed in Rag2KO mice, in combination with in vitro analysis aimed at dissecting the role of pituitary tumor-cells in monocyte recruitment.

RESULTS

We report that gonadotroph PitNETs present an increased CD68+ macrophage signature compared to somatotroph, lactotroph, and corticotroph PitNETs. Transcriptomic and histological characterizations confirmed gonadotroph infiltrating macrophages expressed CD163, MRC-1, ARG1, and CSF1R M2 macrophage markers. Use of growth hormone (GH)3/GH4 somatotroph and LβT2/αT3.1 gonadotroph cells drove THP1 macrophage migration through respective expression of CCL5 or CSF1. Although both LβT2 and GH3 cells recruited F4/80 macrophages following their engraftment in mice, only LβT2 gonadotroph cells showed a capacity for M2-like polarization. Similar observations were performed on patient-derived xenografts from somatotroph and gonadotroph tumors. Analysis of clinical data further demonstrated a significant correlation between the percentage of CD68+ and CD163+ infiltrating macrophages and the invasive character of gonadotroph tumors.

CONCLUSIONS

Gonadotroph tumor drive the recruitment of macrophages and their subsequent polarization to an M2-like phenotype. More importantly, the association between infiltrating CD68+/CD163+ macrophages and the invasiveness of gonadotroph tumors points to macrophage-targeted immunotherapies being a potent strategy to limit the progression of gonadotroph PitNETs.

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

PURPOSES

Immunotherapies for solid tumor are gaining traction in the clinic, however, the immunological landscape of pituitary adenomas (PAs) is not well defined. In the present study, we used the RNA-seq data of PAs to investigate the impact of immunological landscape on clinical features of pituitary adenomas and aim to evaluate the potential immunotherapy for PAs.

METHODS

We analyzed tumor-infiltrating immune cells in 115 PA samples using RNA-seq. Main immune cell types (B cells, CD8⁺ T cells, CD4⁺ T cells, macrophages and NK cells) were detected from the expression of genes. The association between immune cells abundance and immune checkpoint, as well as inflammatory factors were analyzed. 10 additional patients were enrolled for validation.

RESULTS

In RNA sequencing data, landscape of PAs were identified. Our computationally inferred immune infiltrates significantly associate with patient clinical features. Growth hormone-secreting adenomas (GHomas) were found with higher B cells and CD8⁺ T cells infiltration. Moreover, GHomas showed relative different genetic background, significant invasive behavior and independently correlated with reduced progress-free time. Tumor progression was related to increased expression of PD-1/PD-L1 and was associated with higher immune infiltration. Analysis of cancer-testis antigen expression and CD8⁺ T-cell abundance suggested CTAG2 and TSPYL6 were potential immunotherapeutic targets in GHomas and non-functioning adenomas, respectively.

CONCLUSIONS

Tumor-infiltrating immune cells confer important clinical and biological implications. Our results of immune-infiltrate levels in PAs may inform effective cancer vaccine and checkpoint blockade therapies and make it possible to take immunotherapy into invasive PAs.

Update on the Genetics of Pituitary Tumors

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

Platelet-derived PDGF promotes the invasion and metastasis of cholangiocarcinoma by upregulating MMP2/MMP9 expression and inducing EMT via the p38/MAPK signalling pathway

Cholangiocarcinoma (CCA) is an aggressive tumour with a poor prognosis due to its late clinical presentation and the lack of effective non-surgical therapies. Previous studies have reported that platelets are implicated in tumour invasion and metastasis, while their role and the underlying mechanism in CCA remain unclear. Here, we show that platelets are hyperactivated in patients with CCA and that platelet-derived growth factor (PDGF) promotes the migration of CCA tumour cells both in vitro and in vivo. Further investigations revealed that PDGF can upregulate the expression of MMP2/MMP9 and induce epithelial-mesenchymal transition (EMT) by activating the p38/MAPK signalling pathway in CCA cells. In addition, the expression of MMP2/MMP9 was associated with lymph node metastasis and poor prognosis in CCA patients after surgical resection. In conclusion, our findings demonstrate that platelets play an important role in facilitating the invasion and metastasis of CCA cells by secreting PDGF, which may provide a novel target for CCA treatment.

The CCL5/CCR5 Axis in Cancer Progression

Tumor cells can “hijack” chemokine networks to support tumor progression. In this context, the C-C chemokine ligand 5/C-C chemokine receptor type 5 (CCL5/CCR5) axis is gaining increasing attention, since abnormal expression and activity of CCL5 and its receptor CCR5 have been found in hematological malignancies and solid tumors. Numerous preclinical in vitro and in vivo studies have shown a key role of the CCL5/CCR5 axis in cancer, and thus provided the rationale for clinical trials using the repurposed drug maraviroc, a CCR5 antagonist used to treat HIV/AIDS. This review summarizes current knowledge on the role of the CCL5/CCR5 axis in cancer. First, it describes the involvement of the CCL5/CCR5 axis in cancer progression, including autocrine and paracrine tumor growth, ECM (extracellular matrix) remodeling and migration, cancer stem cell expansion, DNA damage repair, metabolic reprogramming, and angiogenesis. Then, it focuses on individual hematological and solid tumors in which CCL5 and CCR5 have been studied preclinically. Finally, it discusses clinical trials of strategies to counteract the CCL5/CCR5 axis in different cancers using maraviroc or therapeutic monoclonal antibodies.

The tumour microenvironment of pituitary neuroendocrine tumours

The tumour microenvironment (TME) includes a variety of non-neoplastic cells and non-cellular elements such as cytokines, growth factors and enzymes surrounding tumour cells. The TME emerged as a key modulator of tumour initiation, progression and invasion, with extensive data available in many cancers, but little is known in pituitary tumours. However, the understanding of the TME of pituitary tumours has advanced thanks to active research in this field over the last decade. Different immune and stromal cell subpopulations, and several cytokines, growth factors and matrix remodelling enzymes, have been characterised in pituitary tumours. Studying the TME in pituitary tumours may lead to a better understanding of tumourigenic mechanisms, identification of biomarkers useful to predict aggressive disease, and development of novel therapies. This review summarises the current knowledge on the different TME cellular/non-cellular elements in pituitary tumours and provides an overview of their role in tumourigenesis, biological behaviour and clinical outcomes.

Large-scale second-hit AIP deletion causing a pediatric growth hormone-secreting pituitary adenoma: Case report and review of literature

Gigantism (early-onset acromegaly) is a rare pediatric disorder caused by a growth hormone (GH)-secreting pituitary adenoma. Approximately 50% patients of gigantism have a germline mutation, most commonly an inactivating mutation in the aryl-hydrocarbon interacting receptor protein (AIP) gene on chromosome 11q13.2. We present an 11-year-old male patient with a GH-secreting pituitary macroadenoma who presented with excessive growth spurts, behavioral changes, and frontal headaches. He was successfully treated with an endoscopic endonasal gross total resection and subsequently demonstrated biochemical cure. Whole-exome sequencing showed a heterozygous germline mutation in the AIP gene suggesting pituitary adenoma predisposition. Analysis of the tumor tissue revealed a large-scale deletion on chromosome 11 overlapping with AIP leading to bi-allelic AIP loss. Coincident germline and somatic AIP mutations were likely causal in formation of a GH-secreting adenoma with an aggressive phenotype. This case exemplifies the need for early diagnosis and curative surgery in the management of AIP-mutated pituitary adenomas.