The expression of AIP-related molecules in elucidation of cellular pathways in pituitary adenomas.
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.
Department of Medical Genetics, Genome-Scale Biology Research Program, University of Helsinki, Helsinki, Finland.
Elina
E
Heliövaara
Anniina
A
Raitila
Virpi
V
Launonen
Anders
A
Paetau
Johanna
J
Arola
Heli
H
Lehtonen
Timo
T
Sane
Robert J
RJ
Weil
Outi
O
Vierimaa
Pasi
P
Salmela
Karoliina
K
Tuppurainen
Markus
M
Mäkinen
Lauri A
LA
Aaltonen
Auli
A
Karhu
D000818:Animals; D018952:Antigens, CD34 / Q000096:biosynthesis / Q000235:genetics; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D050760:Cyclin-Dependent Kinase Inhibitor p27; D015536:Down-Regulation; D015870:Gene Expression; D020869:Gene Expression Profiling; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000096:biosynthesis / Q000235:genetics; D007150:Immunohistochemistry; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009154:Mutation; D010911:Pituitary Neoplasms / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering; D018336:Receptors, Aryl Hydrocarbon / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D014162:Transfection
C497396:ARNT protein, human; D018952:Antigens, CD34; C436291:CDKN1B protein, human; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D047908:Intracellular Signaling Peptides and Proteins; D034741:RNA, Small Interfering; D018336:Receptors, Aryl Hydrocarbon; C103265:aryl hydrocarbon receptor-interacting protein; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D050760:Cyclin-Dependent Kinase Inhibitor p27