Intratumoural spatial distribution of S100B + folliculostellate cells is associated with proliferation and expression of FSH and ERα in gonadotroph tumours

Pituitary folliculo-stellate cells modulate tumor vasculature and extracellular matrix composition in experimental lactosomatotropinomas

Folliculo-stellate cells (FSCs) constitute 5-10 % of the adenohypophysis and have been proposed as paracrine regulators of pituitary cells. However, their participation in pituitary tumor development remains unclear. We generated a lacto-somatotropic tumor model by subcutaneous injection of GH3 (lacto-somatotrophs) and the FSCs TtT/GF, isolated or combined, in immunodeficient mice, to study the role of the FSCs on tumor formation, hormone secretion, vascularization and extra-cellular matrix involvement. The co-culture of both cell lines let us gain insight into the proliferative and secretory action of FSC in pituitary tumor modulation. Our results showed that initially GH3:TtT/GF tumors had an earlier onset, but lately, TtT/GF cells restrained GH3:TtT/GF tumor growth and their Prl synthesis, although no differences were observed in the proliferative potential of tumor cells in vivo. Instead, TtT/GF cells exerted a direct mitogenic action on GH3 cells in vitro. Moreover, GH3 tumors had fewer irrigating vessels, lower vascular area and a higher VEGF/bFGF ratio that correlated with Hif1a expression, consistent with the tissue hypoxia and hemorrhage. These features were downregulated in their co-injected counterparts, which interestingly showed an increased deposition of collagens, glycoproteins and mucopolysaccharides extra-cellular matrix (EMC) components. Isolated TtT/GF injected cells did not generate tumors, but they developed fibrous masses characterized by collagen and high bFGF production. In conclusion, our results demonstrate that FSCs are dual regulators of pituitary tumor growth, with a mitogenic action on tumor cells but also a restrictive tumor effect on the cancer processes angiogenesis, hypoxia, and ECM remodeling.

New insights in cellular senescence: The pituitary model

Pituitary tumors are characterized by slow proliferation rates and a high prevalence within the population. The pathogenesis of these tumors remains incompletely understood, although accumulating evidence suggests that the activation of the cellular senescence program, triggered by various stressors and functioning as a brake on cellular proliferation, may contribute to their typically benign nature. Multiple mediators of the senescence response are implicated in this process. Interleukin-6 (IL-6), a proinflammatory cytokine, plays a dual role in pituitary tumor biology. It is involved in both physiological pituitary growth and the senescence-associated secretory phenotype (SASP), where it mediates paracrine-proliferative signals. In addition to its secretory functions, IL-6 has been implicated in the regulation of pituitary senescence through non-secretory mechanisms. Other factors, such as growth hormone (GH), the pituitary tumor-transforming gene (PTTG), and interactions within the tumor microenvironment, including immune cell dynamics, also contribute to the senescence observed in these tumors. This review examines the latest evidence concerning the role of senescence in pituitary tumors, with a particular focus on the contribution of IL-6 to this process.

A Nexus of Biomolecular Complexities in Pituitary Neuroendocrine Tumors: Insights into Key Molecular Drivers

Approximately 90% of the lesions of hypophyseal origins are represented by pituitary neuroendocrine tumors, which further account for up to 22.5% of the intracranial tumors in the adult population. Although the intricacy of this pathology is yet to be fully understood on a biomolecular level, it is well known that these lesions develop within a microenvironment that supports their evolution and existence. The role of the tumoral microenvironment in pituitary lesions is pivotal, mainly due to this gland's distinct anatomical, histological, and physiological structure and function. Each component of the tumoral microenvironment is specifically involved in tumorigenesis, angiogenesis, tumoral growth, progression, and dissemination. By recognizing and understanding how these elements are involved in such processes, targeted treatments can emerge, and better future management of pituitary lesions can be provided. This article aims to summarize the role of each component of the tumoral microenvironment in pituitary lesions while assessing their association with biomolecular mechanisms.

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.

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.

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.