The expression of AIP-related molecules in elucidation of cellular pathways in pituitary adenomas.

Department of Medical Genetics, Genome-Scale Biology Research Program, University of Helsinki, Helsinki, Finland.
American Journal Of Pathology (Impact Factor: 4.6). 10/2009; 175(6):2501-7. DOI: 10.2353/ajpath.2009.081131
Source: PubMed

ABSTRACT Germline mutations in the aryl hydrocarbon receptor interacting protein (AIP) gene predispose to the development of pituitary adenomas. Here, we characterized AIP mutation positive (AIPmut+) and AIP mutation negative (AIPmut-) pituitary adenomas by immunohistochemistry. The expressions of the AIP-related proteins aryl hydrocarbon receptor (AHR), AHR nuclear translocator (ARNT), cyclin-dependent kinase inhibitor 1B encoding p27(Kip1), and hypoxia-inducible factor 1-alpha were examined in 14 AIPmut+ and 53 AIPmut- pituitary adenomas to detect possible expression differences. In addition, the expression of CD34, an endothelial and hematopoietic stem cell marker, was analyzed. We found ARNT to be less frequently expressed in AIPmut+ pituitary adenomas (P = 0.001), suggesting that AIP regulates the ARNT levels. AIP small interfering RNA-treated HeLa, HEK293, or Aip-null mouse embryonic fibroblast cells did not show lowered expression of ARNT. Instead, in the pituitary adenoma cell line GH3, Aip silencing caused a partial reduction of Arnt and a clear increase in cell proliferation. We also observed a trend for increased expression of nuclear AHR in AIPmut+ samples, although the difference was not statistically significant (P = 0.06). The expressions of p27(Kip1), hypoxia-inducible factor 1-alpha, or CD34 did not differ between tumor types. The present study shows that the expression of ARNT protein is significantly reduced in AIPmut+ tumors. We suggest that the down-regulation of ARNT may be connected to an imbalance in AHR/ARNT complex formation arising from aberrant cAMP signaling.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Aryl hydrocarbon Receptor (AHR) pathway has a key-role in cellular detoxification mechanisms and seems implicated in tumorigenesis. Moreover, polymorphisms and mutations of AHR gene have been associated with several human and animal tumours. Although AHR has been found differently expressed in pituitary adenomas, AHR gene mutation status has never been investigated in acromegalic patients. In this study we evaluated patients with apparently sporadic GH-secreting pituitary adenoma for AHR gene variants. 70 patients with sporadic GH-secreting pituitary adenoma (M=27, age 59.1±1.6 years) and 157 sex- and age-matched controls were enrolled in the study. In all patients and controls, the exons 1, 2, 3, 5 and 10 of AHR gene were evaluated for nucleotide variants by sequencing analysis. The rs2066853 polymorphism was identified in the exon 10 of 18/70 acromegalic patients and 9/157 healthy subjects (25.7 vs. 5.7%, χ(2) 18.98 p <0.0001), in homozygosis in one patient and in heterozygosis in the other 17 and in the 9 healthy subjects. Moreover, a heterozygous rs4986826 variant in exon 10 was identified in a patient with heterozygous rs2066853 polymorphism, and in the patient with homozygous rs2066853 variant. This second polymorphism was not detected in the control group. Patients with rs2066853 polymorphism showed increased IGF-1 ULN (p <0.05) and prevalence of cavernous sinus invasion (p <0.05), thyroid (p 0.02), bladder (p 0.0001) or lymphohematopoietic (p <0.05) tumours. AHR gene rs2066853 polymorphism is significantly more frequent in acromegalic patients than in healthy subjects, regardless of gender, pituitary tumour size, age at diagnosis and prevalence of colonic tumours and is associated with increased disease aggresivity. Moreover, the rs4986826 variant was detected in few patients with rs2066853 polymorphism, but its role is to be cleared. This article is protected by copyright. All rights reserved.
    Clinical Endocrinology 02/2014; · 3.35 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Our aim was to explore the interactions of intercellular adhesion molecule (sICAM-1), TNF-α (tumor necrosis factor-α), interleukin-1α (IL-1α) and interleukin-6 (IL-6) with dopamine agonists in a culture of adenomatous cells from an nonfunctional macroadenoma. Materials and methods. Tissue specimen from pituitary macroadenoma removed in transsphenoidal surgery was prepared for primary culture. Cells were counted and plated at 10 5 /well into 24-well plates in a final volume of 1ml. Cabergoline in molar doses of 10 -6 , 10 -7 , 10 -8 , 10 -9 was added and the cells were incubated for 4 days. sICAM-1, TNF-α, IL-1 α, IL-6 were measured from cell-culture supernatants by ELISA kits. Results. sICAM-1, TNF-α, IL-1α and IL-6 were detected in the untreated control cultures after a 4d period. There was a negative correlation between TNFα and IL-1α (p=0.007). The levels of PRL and hGH had measurable values above those found in culture medium without tumor cells. PRL positively correlated with IL-1α (p=0.05). hGH positively correlated with cell proliferation (p=0.049). Cabergoline treatment showed that IL-6 progressively decreased with the dose, ranging from -27.41% to -76.44%. TNF-α significantly decreased (-65.90%; p<0.03) at the cabergoline 10 -7 M dose. IL-1α progressively increased with cabergoline dose, ranging from -2.53% to 345 %. sICAM-1 was significantly reduced by cabergoline at 10 -9 (-47.12 %; p= 0.045) and 10 -6 M (-59.16%; p=0.01) doses. TNF-α positively correlated with PRL (p=0.025); IL-6 positively correlated with hGH (p=0.044); sICAM-1 negatively correlated with hGH (p=0.009), TNFα (p=0.025) and IL-1α (p=0.044). Conclusions. These data support the existence of an immunoendocrine network in pituitary tumorigenesis; TNF-α, IL-6, IL-1α, sICAM-1 significantly interfered by cabergoline treatment in a dose-dependent way. However, future studies on different types of pituitary tumours are needed to confirm these findings.
  • [Show abstract] [Hide abstract]
    ABSTRACT: The aryl hydrocarbon receptor interacting protein (AIP) is a tumor-suppressor gene underlying the pituitary adenoma predisposition. Thus far, the exact molecular mechanisms by which inactivated AIP exerts its tumor-promoting action have been unclear. To better understand the role of AIP in pituitary tumorigenesis, we performed gene expression microarray analysis to examine changes between Aip wild-type and knockout mouse embryonic fibroblast (MEF) cell lines. Transcriptional analyses implied that Aip deficiency causes a dysfunction in cyclic adenosine monophosphate (cAMP) signaling, as well as impairments in signaling cascades associated with developmental and immune-inflammatory responses. In vitro experiments showed that AIP deficiency increases intracellular cAMP concentrations in both MEF and murine pituitary adenoma cell lines. Based on knockdown of various G protein α subunits, we concluded that AIP deficiency leads to elevated cAMP concentrations through defective Gαi-2 and Gαi-3 proteins that normally inhibit cAMP synthesis. Furthermore, immunostaining of Gαi-2 revealed that AIP deficiency is associated with a clear reduction in Gαi-2 protein expression levels in human and mouse growth hormone (GH)-secreting pituitary adenomas, thus indicating defective Gαi signaling in these tumors. By contrast, all prolactin-secreting tumors showed prominent Gαi-2 protein levels, irrespective of Aip mutation status. We additionally observed reduced expression of phosphorylated extracellular signal-regulated kinases 1/2 and cAMP response element-binding protein levels in mouse and human AIP-deficient somatotropinomas. This study implies for the first time that a failure to inhibit cAMP synthesis through dysfunctional Gαi signaling underlies the development of GH-secreting pituitary adenomas in AIP mutation carriers.Oncogene advance online publication, 24 March 2014; doi:10.1038/onc.2014.50.
    Oncogene 03/2014; · 8.56 Impact Factor

Full-text (2 Sources)

Available from
May 20, 2014