Inhibition of Bcl3 gene expression mediates the anti-proliferative action of estrogen in pituitary lactotrophs in primary culture

• Published in: Molecular and cellular endocrinology Vol. 345; no. 1-2; pp. 68 - 78
• Main Authors: Mitsui, Tetsuo, Ishida, Maho, Izawa, Michi, Kagami, Yoshihiro, Arita, Jun
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier Ireland Ltd 15.10.2011
• Subjects: AKT protein; Animals; Bcl3; Cell culture; Cell Proliferation - drug effects; DNA microarrays; Enzyme Activation - drug effects; estradiol; Estradiol - pharmacology; Estrogen; Estrogens; Extracellular signal-regulated kinase; Extracellular Signal-Regulated MAP Kinases - metabolism; Female; Gene expression; Gene Expression Regulation - drug effects; Gene Knockdown Techniques; genes; Humans; Insulin-like growth factor I; Insulin-Like Growth Factor I - pharmacology; Lactotroph; Lactotrophs - cytology; Lactotrophs - drug effects; Lactotrophs - enzymology; Lactotrophs - metabolism; microarray technology; NF-kappa B - antagonists & inhibitors; NF-kappa B - metabolism; Oligonucleotide Array Sequence Analysis; Phosphorylation; Phosphorylation - drug effects; Pituitary; Polymerase chain reaction; Primary Cell Culture; Proliferation; Protein kinase; protein kinases; Proto-Oncogene Proteins - genetics; Proto-Oncogene Proteins - metabolism; Proto-Oncogene Proteins c-akt - metabolism; quantitative polymerase chain reaction; Rats; Rats, Wistar; Real-Time Polymerase Chain Reaction; RNA; Signal Transduction - drug effects; transcription factor NF-kappa B; Transcription Factors - genetics; Transcription Factors - metabolism; Proliferation; Lactotroph; Estrogen; Bcl3
• DOI: 10.1016/j.mce.2011.07.021
• ISSN: 0303-7207

► We investigated how estrogen inhibited the proliferation of pituitary lactotrophs. ► DNA microarray analysis identified Bcl3 as an estrogen-downregulated gene. ► Overexpression of Bcl3 blocked the antiproliferative action of estrogen. ► Bcl3 is implicated in the antiproliferative action of estrogen on lactotrophs. In addition to their well-known stimulatory action, estrogens have an anti-proliferative effect. The present study was undertaken to investigate the mechanism by which 17β-estradiol (E2) inhibits insulin-like growth factor-1 (IGF-1)-induced proliferation in vitro in the rat pituitary lactotroph, a typical estrogen-responsive cell. E2 treatment of pituitary cells did not change levels of IGF-1-induced phosphorylation of proliferation-related protein kinases such as Erk1/2 and Akt. We performed global gene expression profiling by DNA microarray analysis and identified 177 genes regulated by E2 in the presence of IGF-1. These results were verified by quantitative real time PCR. The estrogen-regulated genes included several NFκB family related genes. As pharmacological inhibition of the NFκB pathway blocked IGF-1-induced lactotroph proliferation, we chose to investigate whether one NFκB pathway gene, Bcl3, was involved in the anti-proliferative action of E2. RNA interference-mediated knockdown of Bcl3 expression attenuated IGF-1-induced lactotroph proliferation. Even minimal induced overexpression of Bcl3 blocked the anti-proliferative action of E2. In contrast, Nfkb2, another E2-downregulated protein, required maximal overexpression to block the anti-proliferative action of E2. These results suggest that inhibition of Bcl3 expression is involved in the anti-proliferative action of estrogens in pituitary lactotrophs in culture.