title: Paracrine and autocrine mechanisms of apelin signaling govern embryonic and tumor angiogenesis.
abstract: Apelin and its G protein-coupled receptor APJ play important roles in blood pressure regulation, body fluid homeostasis, and possibly the modulation of immune responses. Here, we report that apelin-APJ signaling is essential for embryonic angiogenesis and upregulated during tumor angiogenesis. A detailed expression analysis demonstrates that both paracrine and autocrine mechanisms mark areas of embryonic and tumor angiogenesis. Knockdown studies in Xenopus reveal that apelin-APJ signaling is required for intersomitic vessel angiogenesis. Moreover, ectopic expression of apelin but not vascular endothelial growth factor A (VEGFA) is sufficient to trigger premature angiogenesis. In vitro, apelin is non-mitogenic for primary human endothelial cells but promotes chemotaxis. Epistasis studies in Xenopus embryos suggest that apelin-APJ signaling functions downstream of VEGFA. Finally, we show that apelin and APJ expression is highly upregulated in microvascular proliferations of brain tumors such as malignant gliomas. Thus, our results define apelin and APJ as genes of potential diagnostic value and promising targets for the development of a new generation of anti-tumor angiogenic drugs.
authors.affiliation: Institute of Pharmaceutical Sciences, Department of Chemistry and Applied Biosciences, ETH Zurich, Wolfgang-Pauli-Strasse 10, CH-8093 Zurich, Switzerland.
authors.forename: Roland E
authors.initials: RE
authors.lastname: Kälin
authors.forename: Martin P
authors.initials: MP
authors.lastname: Kretz
authors.forename: Andrea M
authors.initials: AM
authors.lastname: Meyer
authors.forename: Andreas
authors.initials: A
authors.lastname: Kispert
authors.forename: Frank L
authors.initials: FL
authors.lastname: Heppner
authors.forename: André W
authors.initials: AW
authors.lastname: Brändli
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000595:Amino Acid Sequence; D000818:Animals; D000073861:Apelin; D019898:Autocrine Communication / Q000502:physiology*; D001932:Brain Neoplasms / Q000098:blood supply / Q000378:metabolism; D016466:CHO Cells; D002478:Cells, Cultured; D006224:Cricetinae; D003412:Cricetulus; D004625:Embryo, Nonmammalian / Q000098:blood supply* / Q000502:physiology; D005910:Glioma / Q000098:blood supply / Q000378:metabolism; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D051379:Mice; D008875:Middle Aged; D008969:Molecular Sequence Data; D009389:Neovascularization, Pathologic / Q000378:metabolism*; D018919:Neovascularization, Physiologic / Q000502:physiology*; D019899:Paracrine Communication / Q000502:physiology*; D043562:Receptors, G-Protein-Coupled / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D029867:Xenopus Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*
chemical_list: C513482:APLN protein, Xenopus; C115436:APLN protein, human; C105530:APLNR protein, Xenopus; D000073861:Apelin; D036341:Intercellular Signaling Peptides and Proteins; D043562:Receptors, G-Protein-Coupled; D029867:Xenopus Proteins