title: STAT5 and prolactin participate in a positive autocrine feedback loop that promotes angiogenesis.
abstract: We have shown previously that the murine prolactin/growth hormone family member proliferin plays a pivotal role in angiogenesis induced by the FGF2/STAT5 signaling cascade. To delineate the signaling pathway downstream of STAT5 in the human system, where proliferin does not exist, we expressed constitutively active (CA) or dominant-negative (DN) mutant STAT5A in hCMEC/D3 human brain endothelial cells. We found that conditioned medium from CA-STAT5A- but not from DN-STAT5A-overexpressing endothelial cells (EC) is sufficient to induce EC migration and tube formation but not proliferation, indicating that STAT5A regulates the secretion of autocrine proangiogenic factors. We identified prolactin (PRL) as a candidate autocrine factor. CA-STAT5A expression stimulates PRL production at the RNA and protein level, and STAT5A binds to the PRL promoter region, suggesting direct transcriptional regulation. Medium conditioned by CA-STAT5A-overexpressing EC induces phosphorylation of the PRL receptor and activates MAPK. Knockdown of PRL expression by shRNA or blocking of PRL activity with neutralizing antibodies removed the CA-STAT5A-dependent proangiogenic activity from the conditioned medium of EC. The addition of recombinant PRL restores this activity. STAT5A-induced PRL in the conditioned medium can activate STAT5, STAT1, and to a lesser extent STAT3 in hCMEC/D3 cells, suggesting the existence of a positive feedback loop between STAT5 and PRL that promotes angiogenesis. Furthermore, we find that VEGF, a potent proangiogenic factor, is induced by activation of STAT5A, and VEGF induction depends on PRL expression. These observations demonstrate a STAT5/PRL/VEGF signaling cascade in human brain EC and implicate PRL and VEGF as autocrine regulators of EC migration, invasion, and tube formation.
authors.affiliation: From the Department of Pathology and Laboratory Medicine, University of Wisconsin, Madison, Wisconsin 53705.
authors.forename: Xinhai
authors.initials: X
authors.lastname: Yang
authors.affiliation: From the Department of Pathology and Laboratory Medicine, University of Wisconsin, Madison, Wisconsin 53705.
authors.forename: Kristy
authors.initials: K
authors.lastname: Meyer
authors.affiliation: From the Department of Pathology and Laboratory Medicine, University of Wisconsin, Madison, Wisconsin 53705,; Pathology and Laboratory Medicine Service, William S. Middleton Memorial Veterans Hospital, Department of Veterans Affairs Medical Center, Madison, Wisconsin 53705, and; UW Carbone Cancer Center, Madison, Wisconsin 53792. Electronic address: afriedl@wisc.edu.
authors.forename: Andreas
authors.initials: A
authors.lastname: Friedl
mesh_terms: D043925:Angiogenesis Inducing Agents / Q000378:metabolism; D000818:Animals; D019898:Autocrine Communication / Q000187:drug effects; D002465:Cell Movement / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D017077:Culture Media, Conditioned / Q000494:pharmacology; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D025461:Feedback, Physiological / Q000187:drug effects; D020868:Gene Silencing / Q000187:drug effects; D006801:Humans; D051379:Mice; D018919:Neovascularization, Physiologic / Q000187:drug effects; D010766:Phosphorylation / Q000187:drug effects; D011388:Prolactin / Q000378:metabolism* / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects / Q000235:genetics; D034741:RNA, Small Interfering / Q000378:metabolism; D011981:Receptors, Prolactin / Q000378:metabolism; D050799:STAT5 Transcription Factor / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D025521:Tumor Suppressor Proteins / Q000378:metabolism*; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000378:metabolism
chemical_list: D043925:Angiogenesis Inducing Agents; D017077:Culture Media, Conditioned; D034741:RNA, Small Interfering; D011981:Receptors, Prolactin; D050799:STAT5 Transcription Factor; C494092:STAT5A protein, human; D025521:Tumor Suppressor Proteins; D042461:Vascular Endothelial Growth Factor A; D011388:Prolactin; D040301:Vascular Endothelial Growth Factor Receptor-2; D048049:Extracellular Signal-Regulated MAP Kinases
keywords: Angiogenesis; Autocrine Factors; Cell Migration; Cell Signaling; Prolactin; STAT Transcription Factor; STAT5