Endocrine Abstracts

Background: Patients with heterozygote germline mutations in the aryl-hydrocarbon receptor interacting protein (AIP) gene (AIPpos) develop often aggressively growing tumours in early teenage years. The mechanism of this behaviour is not clear.

Aim: The role of the microenvironment in the invasive phenotype of AIPpos pituitary tumours.

Methods and results: We established that AIPpos GH-secreting tumours are infiltrated by a large number of macrophages and our microarray data on human AIP-mutant tissue samples compared to sporadic somatotrophinomas identified the ‘epithelial-to-mesenchymal transition’ (EMT)-pathway as one of the most significantly altered pathways in AIPpos tumours. Down-regulation of E-cadherin, beta-catenin, PERP, ESRP1 and up-regulation of ZEB1 (P<0.05–<0.0001). There is a functional relationship between tumour associated macrophages and EMT. Following validation of selected genes (RT-qPCR and immunohistochemistry), EMT was induced on stable AIP-knockdown GH3 cells using rat bone marrow macrophage-derived conditioned media (MCM) and assessed by Western blotting and immunofluorescence. MCM induced EMT-like phenotype, increased migratory and invasive properties, as assessed by transwell and matrigel invasion chambers, of AIP-KD cells. On the other hand, AIP-KD cell-derived media significantly increased macrophage migration. As chemoattractant CCL5 was highly up-regulated in AIPpos tumours, addition of CCL5 also increased macrophage migration and was blocked by CCL5-receptor inhibitor maraviroc by 50%.

Conclusions: This study showed the potential crosstalk between the pituitary adenomas with its microenvironment. Macrophages increased invasion of AIP-KD cells while tumour cell supernatant increased macrophage migration at least partly via CCL5. Data from this study will help us to understand the role of microenvironment in invasive pituitary tumour development which might lead to novel treatment targets.