Pituitary tumour fibroblast-derived cytokines influence tumour aggressiveness

Abstract

Tumour-associated fibroblasts (TAFs) are key elements of the tumour microenvironment, but their role in pituitary neuroendocrine tumours (PitNETs) has been little explored. We hypothesised that TAF-derived cytokines may play a role in tumour aggressiveness and that their release can be inhibited by somatostatin analogues. TAFs were isolated and cultured from 16 PitNETs (11 clinically non-functioning tumours and 5 somatotropinomas). The fibroblast secretome was assessed with a 42-plex cytokine array before and after multiligand somatostatin receptor agonist pasireotide treatment. Angiogenesis and epithelial-to-mesenchymal transition pathway assessment included CD31, E-cadherin and ZEB1 expression. GH3 cells treated with TAF- or skin fibroblast-conditioned medium were assessed for migration, invasion and cell morphology changes. PitNET TAFs secreted significant amounts of cytokines including CCL2, CCL11, VEGF-A, CCL22, IL-6, FGF-2 and IL-8. TAFs from PitNETs with cavernous sinus invasion secreted higher IL-6 levels compared to fibroblasts from non-invasive tumours (P = 0.027). Higher CCL2 release from TAFs correlated with more capillaries (r = 0.672, P = 0.004), and TAFs from PitNETs with a higher Ki-67 tended to secrete more CCL2 (P = 0.058). SST1 is the predominant somatostatin receptor in TAFs, and pasireotide decreased TAF-derived IL-6 by 80% (P < 0.001) and CCL2 by 35% (P = 0.038). GH3 cells treated with TAF-conditioned medium showed increased migration and invasion compared to cells treated with skin fibroblast-conditioned medium, with morphological and E-cadherin and ZEB1 expression changes suggesting epithelial-to-mesenchymal transition. TAF-derived cytokines may increase PitNET aggressiveness, alter angiogenesis and induce epithelial-to-mesenchymal transition changes. Pasireotide’s inhibitory effect on TAF-derived cytokines suggest that this effect may play a role in its anti-tumour effects.

Novel Insights into Pituitary Tumorigenesis: Genetic and Epigenetic Mechanisms

“…In this review we have concentrated on the novel genetic changes in pituitary adenomas. We refer to data on other important aspects of pituitary tumorigenesis, such as the role of senescence ( 331 , 332 ), cytokines ( 47 , 333 ) or tumor-associated fibroblasts ( 334 , 335 ) in establishing the clinical phenotype of tumors is an emerging focus of research interest ( 336 ).…”

The epidemiology of aggressive pituitary tumors (and its challenges)

“…However, not only markers of proliferation are still considered relevant for aggressive behavior [3], also local factors like cavernous sinus and/or sphenoid sinus invasion and tumor microenvironment, are considered relevant. Secretion of chemokines by the tumor facilitate macrophage, neutrophil, and T cell recruitment into the tumor [15], and tumor associated fibroblasts cultured from clinically nonfunctioning adenomas and somatotropinomas, secreted more IL-6 in those cases that presented with cavernous sinus invasion compared to fibroblasts from non-invasive tumors [16].…”

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

“…The alteration of the tumor microenvironment seems to be triggered by tumor chemokines that attract immune cells ( 42 ). Additionally, IL-6 and CCL2 produced by tumor associated fibroblasts have been associated with EMT-like morphological changes and aggressive behavior trough E-cadherin downregulation and ZEB1 upregulation in an in vitro study ( 43 ).…”

“…As an example, CCNB1 overexpression in acromegaly can be targeted with resveratrol, inhibiting CCNB1 and reverting its effects on invasion ( 31 ). Interestingly, Pasireotide, a second generation SRL, has been associated with a reduction of EMT-associated chemokines in tumor associated fibroblasts, suggesting an anti-tumor effect targeting the microenvironment ( 43 ). In contrast, other first generation SRLs do not appear to affect EMT ( 59 ).…”