Inhibition of prolactin (PRL)-induced proliferative signals in breast cancer cells by a molecular mimic of phosphorylated PRL, S179D-PRL.

Abstract	Posttranslational modifications of prolactin (PRL), including phosphorylation, vary with physiologic state and alter biologic activity. In light of the growing evidence for a role for PRL in proliferation in mammary cancer, we examined the ability of a mimic of phosphorylated human PRL, S179D-PRL, to initiate signals to several pathways in mammary tumor cells alone and in combination with unmodified PRL. Unmodified PRL employed multiple pathways to increase cellular proliferation and cyclin D1 levels in PRL-deficient MCF-7 cells. S179D-PRL was a weak agonist compared with unmodified PRL with regard to cellular proliferation, cyclin D1 levels, and phosphorylation of signal transducer and activator of transcription 5 and ERKs. However, S179D-PRL was a potent antagonist of unmodified PRL to these endpoints. In contrast to the reduced levels of the long isoform of the PRL receptor observed in response to a 3-d incubation with unmodified PRL, S179D-PRL up-regulated expression of this isoform, 4-fold. These studies support the utility of this mutant as a PRL antagonist to proliferative signals in mammary epithelial cells, including a potential role in breast cancer therapeutics.
Authors	Matthew D Schroeder, Jennifer L Brockman, Ameae M Walker, Linda A Schuler
Journal	Endocrinology (Endocrinology) Vol. 144 Issue 12 Pg. 5300-7 (Dec 2003) ISSN: 0013-7227 [Print] United States
PMID	12970160 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)
Chemical References	DNA-Binding Proteins Milk Proteins Receptors, Prolactin STAT5 Transcription Factor Trans-Activators prolactin, Asp(179)- Cyclin D1 Prolactin Mitogen-Activated Protein Kinases
Topics	Animals Breast Neoplasms CHO Cells Cell Count Cell Division (drug effects, physiology) Cell Line, Tumor Cricetinae Cyclin D1 (metabolism) DNA-Binding Proteins (metabolism) Humans Milk Proteins Mitogen-Activated Protein Kinases (metabolism) Molecular Mimicry Phosphorylation Prolactin (metabolism, pharmacology) Receptors, Prolactin (metabolism) STAT5 Transcription Factor Signal Transduction (drug effects, physiology) Trans-Activators (metabolism)

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