Expression of Growth Factors in Normal and Neoplastic Pituitary Tissues

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

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

The expression of neural cell adhesion molecule and the microenvironment of pituitary neuroendocrine tumours

The neural cell adhesion molecule (NCAM) has previously been studied in pituitary neuroendocrine tumours (PitNETs), but its role in tumour biology and aggressiveness remains controversial, and its relationship with the tumour microenvironment remains unknown. We aimed to characterise NCAM expression in PitNETs, to correlate this with clinico-pathological features, and to assess the role of various microenvironment components on NCAM expression. NCAM and immune cells were investigated by immunohistochemistry in 16 human non-functioning-PitNETs (NF-PitNETs) and eight somatotrophinomas, including macrophages (CD68, CD163, HLA-DR), cytotoxic (CD8) and T helper (CD4) lymphocytes, regulatory T cells (FOXP3), B cells (CD20), and neutrophils (neutrophil elastase). Five normal pituitaries were included for comparison. The cytokine secretome from these PitNETs and from PitNET-derived tumour-associated fibroblasts (TAFs) were assessed on culture supernatants using a multiplex immunoassay panel. There were no significant NCAM expression differences between PitNETs and normal pituitary, and no difference between types of pituitary tumours (NF-PitNETs vs. somatotrophinomas). There was no association between NCAM expression and different clinico-pathological features, including cavernous sinus invasion and Ki-67, nor with serum hormone levels. NCAM immunoreactivity correlated negatively with PitNET-derived CXCL10 (rho = -0.417; p = .042) and CX3CL1 (rho = -0.423; p = .040) levels. NCAM immunoreactivity was negatively correlated with TAF-derived fibroblast growth factor (FGF)-2 (rho = -0.632; p = .009), but not with other TAF-derived cytokines. Within the PitNET cohort, there were no correlations between NCAM immunoreactivity and immune infiltrates or ratios, although, within NF-PitNETs, NCAM expression was higher in tumours with more FOXP3+ cells. NCAM expression does not differ between PitNETs and normal pituitary, and does not appear to relate to tumour invasiveness or proliferation. However, our data suggest a possible role for cytokines in the modulation of NCAM expression in PitNETs, particularly CXCL10, CX3CL1 and FGF-2, but not for immune cell infiltrates.

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.

Anterior pituitary adenomas: inherited syndromes, novel genes and molecular pathways

Pituitary adenomas are common tumors. Although rarely malignant, pituitary adenomas cause significant morbidity due to mass effects and/or hormonal hypo- and/or hyper-secretion. Molecular understanding of pituitary adenoma formation is essential for the development of medical therapies and the treatment of post-operative recurrences. In general, mutations in genes involved in genetic syndromes associated with pituitary tumors are not a common finding in sporadic lesions. By contrast, multiple endocrine neoplasia type 1 (MEN-1) and aryl hydrocarbon receptor-interacting protein (AIP) mutations may be more frequent among specific subgroups of patients, such as children and young adults, with growth hormone-producing adenomas. In this article, we present the most recent data on the molecular pathogenesis of pituitary adenomas and discuss some of the most recent findings from our laboratory. Guidelines for genetic screening and clinical counseling of patients with pituitary tumors are provided.

Pituitary tumors: prognostic indicators

Many factors influence the proliferation of pituitary adenomas: angiogenesis, apoptosis, growth factors, oncogenes, tumor suppressor genes, and hormone receptors. These elements can be demonstrated by immunohistochemistry and/or molecular pathology but no single factor can be used for determination of biological behavior resp. prognosis. Pituitary adenomas can be enclosed or invasive and may be very large or may be microadenomas, but the most important point for prognosis is the total resection in the first or second surgery or the reaction on treatments by drugs. Especially for residual tumor tissue proliferation, markers are important because they may indicate the growth rate and the aggressiveness of the tumor. Radiation therapy is indicated in many of these recurrent tumors and can improve the prognosis.