Progesterone induces expression of the prolactin receptor gene through cooperative action of Sp1 and C/EBP

Abstract

Prolactin (Prl) and progesterone (P) cooperate synergistically during mammary gland development and tumorigenesis. We hypothesized that one mechanism for these effects may be through mutual induction of receptors (R). EpH4 mouse mammary epithelial cells stably transfected with PR-A express elevated levels of PrlR mRNA and protein compared to control EpH4 cells that lack the PR. Likewise, T47D human breast cancer cells treated with P overexpress the PrlR and activate PrlR promoter III. PrlR promoter III does not contain a classical P response element but contains several binding sites for transcription proteins, including C/EBP, Sp1 and AP1, which may also interact with the PR. Using promoter deletion and site directed mutagenesis analyses as well as gel shift assays, cooperative activation of the C/EBP and adjacent Sp1A, but not the Sp1B or AP1, sites by P is shown to confer P responsiveness leading to increased PrlR transcription.

Hormone-Sensing Mammary Epithelial Progenitors: Emerging Identity and Hormonal Regulation

“…In one series of studies, C/EBPβ was found to be necessary for appropriate prolactin and steroid signalling in mouse mammary glands [149]. In a cell-free in vitro binding assay, as well as after transfection of ERα-negative MDA-MB-231 breast cancer cells with ERα and C/EBPβ, ERα was found to form a complex with SP1 and C/EBPβ that is required for the oestrogen-and progesterone-induced expression of PRLR mRNA in EpH4 normal mouse mammary cells [150,151].…”

Lysine Methylation of Progesterone Receptor at Activation Function 1 Regulates both Ligand-independent Activity and Ligand Sensitivity of the Receptor

“…n.s., not significant. tion with other transcription factors, such as activator protein 1 NF-B, through a tethering mechanism (53)(54)(55)(56). To assess the whole cellular effect of K464Q mutation, we generated multiple clones of stably transfected pcDNA3.1, WT PRB, PRB-K464Q, and PRB-K464F MDA-MB-231 cells, and three clones of similar levels of PR protein (Fig.…”

Progesterone receptors, their isoforms and progesterone regulated transcription

“…There is significant crosstalk between prolactin (PRL) and P in the mouse mammary gland, with many of the same genes regulated by both hormones, possibly coregulated by STAT5 (Fernandez-Valdivia et al , 2008; Goldhar et al , 2011; Hilton et al ). In human breast cancer cells both liganded and unliganded PRs upregulate PRL receptors (PRLR) (Jacobsen et al , 2002; Tseng & Zhu, 1998).…”

“…In human breast cancer cells both liganded and unliganded PRs upregulate PRL receptors (PRLR) (Jacobsen et al , 2002; Tseng & Zhu, 1998). The PRLR promoter lacks a consensus PRE but contains multiple transcription factor binding sites including ones for CEBPβ, SP1 and AP1 (Hu et al , 1998) all of which interact with PR (Goldhar et al , 2011). In normal mouse epithelial cells, P regulate inhibitor of differentiation 4 (ID4) via PRB.…”