Upregulation of CDKN2A and suppression of cyclin D1 gene expressions in ACTH-secreting pituitary adenomas.
OBJECTIVE
Cushing's disease (CD) is usually caused by ACTH-secreting pituitary microadenomas, while silent corticotroph adenomas (SCA) are macroadenomas without Cushingoid features. However, the molecular mechanism(s) underlying their different tumor growth remains unknown. The aim of the current study was to evaluate and compare the gene expression profile of cell cycle regulators and cell growth-related transcription factors in CD, SCA, and non-functioning adenomas (NFA).


METHODS
Tumor tissue specimens resected from 43 pituitary tumors were studied: CD (n=10), SCA (n=11), and NFA (n=22). The absolute transcript numbers of the following genes were quantified with real-time quantitative PCR assays: CDKN2A (or p16(INK4a)), cyclin family (A1, B1, D1, and E1), E2F1, RB1, BUB1, BUBR1, ETS1, and ETS2. Protein expressions of p16 and cyclin D1 were semi-quantitatively evaluated by immunohistochemical study.


CONCLUSIONS
CDKN2A gene expression was about fourfold greater in CD than in SCA and NFA. The gene expressions of cyclins D1, E1, and B1, but not of A1, in CD were significantly suppressed than those in NFA. Cyclin D1 gene expression positively correlated with cyclins B1 and E1. The gene expressions of E2F1, RB1, BUB1, BUBR1, ETS1, and ETS2 did not differ between each group. Positive immunostaining for p16 and negative immunostaining for cyclin D1 were more frequent in CD than in NFA; there were positive correlations between mRNA and protein expressions of p16 and cyclin D1. Thus, it is suggested that upregulated CDKN2A with the concomitant downregulated cyclin gene family is partly involved in the small size of ACTH-secreting adenoma.
Tani
Yuji
Y
Department of Clinical and Molecular Endocrinology, Tokyo Medical and Dental University Graduate School, Bunkyo-ku, Tokyo, Japan.
Inoshita
Naoko
N
Sugiyama
Toru
T
Kato
Masako
M
Yamada
Shozo
S
Shichiri
Masayoshi
M
Hirata
Yukio
Y
D049913:ACTH-Secreting Pituitary Adenoma / Q000235:genetics / Q000378:metabolism*; D019938:Cyclin D1 / Q000235:genetics / Q000378:metabolism*; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics / Q000378:metabolism*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics / Q000502:physiology; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D047748:Pituitary ACTH Hypersecretion / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
D019941:Cyclin-Dependent Kinase Inhibitor p16; D019938:Cyclin D1