title: Generation of a functional and durable vascular niche by the adenoviral E4ORF1 gene.
abstract: Vascular cells contribute to organogenesis and tumorigenesis by producing unknown factors. Primary endothelial cells (PECs) provide an instructive platform for identifying factors that support stem cell and tumor homeostasis. However, long-term maintenance of PECs requires stimulation with cytokines and serum, resulting in loss of their angiogenic properties. To circumvent this hurdle, we have discovered that the adenoviral E4ORF1 gene product maintains long-term survival and facilitates organ-specific purification of PECs, while preserving their vascular repertoire for months, in serum/cytokine-free cultures. Lentiviral introduction of E4ORF1 into human PECs (E4ORF1(+) ECs) increased the long-term survival of these cells in serum/cytokine-free conditions, while preserving their in vivo angiogenic potential for tubulogenesis and sprouting. Although E4ORF1, in the absence of mitogenic signals, does not induce proliferation of ECs, stimulation with VEGF-A and/or FGF-2 induced expansion of E4ORF1(+) ECs in a contact-inhibited manner. Indeed, VEGF-A-induced phospho MAPK activation of E4ORF1(+) ECs is comparable with that of naive PECs, suggesting that the VEGF receptors remain functional upon E4ORF1 introduction. E4ORF1(+) ECs inoculated in implanted Matrigel plugs formed functional, patent, humanized microvessels that connected to the murine circulation. E4ORF1(+) ECs also incorporated into neo-vessels of human tumor xenotransplants and supported serum/cytokine-free expansion of leukemic and embryonal carcinoma cells. E4ORF1 augments survival of PECs in part by maintaining FGF-2/FGF-R1 signaling and through tonic Ser-473 phosphorylation of Akt, thereby activating the mTOR and NF-kappaB pathways. Therefore, E4ORF1(+) ECs establish an Akt-dependent durable vascular niche not only for expanding stem and tumor cells but also for interrogating the roles of vascular cells in regulating organ-specific vascularization and tumor neo-angiogenesis.
authors.affiliation: Howard Hughes Medical Institute, Weill Cornell Medical College, New York, NY 10065, USA.
authors.forename: Marco
authors.initials: M
authors.lastname: Seandel
authors.forename: Jason M
authors.initials: JM
authors.lastname: Butler
authors.forename: Hideki
authors.initials: H
authors.lastname: Kobayashi
authors.forename: Andrea T
authors.initials: AT
authors.lastname: Hooper
authors.forename: Ian A
authors.initials: IA
authors.lastname: White
authors.forename: Fan
authors.initials: F
authors.lastname: Zhang
authors.forename: Eva L
authors.initials: EL
authors.lastname: Vertes
authors.forename: Mariko
authors.initials: M
authors.lastname: Kobayashi
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Sergey V
authors.initials: SV
authors.lastname: Shmelkov
authors.forename: Neil R
authors.initials: NR
authors.lastname: Hackett
authors.forename: Sina
authors.initials: S
authors.lastname: Rabbany
authors.forename: Julie L
authors.initials: JL
authors.lastname: Boyer
authors.forename: Shahin
authors.initials: S
authors.lastname: Rafii
mesh_terms: D000256:Adenoviridae / Q000235:genetics*; D017504:Adenovirus E4 Proteins / Q000235:genetics* / Q000378:metabolism*; D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology; D018236:Carcinoma, Embryonal; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D042783:Endothelial Cells / Q000166:cytology* / Q000502:physiology; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism; D018922:HL-60 Cells; D006801:Humans; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D009368:Neoplasm Transplantation; D018919:Neovascularization, Physiologic / Q000502:physiology*; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D017468:Receptors, Fibroblast Growth Factor / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D014471:Umbilical Veins / Q000166:cytology
chemical_list: D017504:Adenovirus E4 Proteins; D016895:Culture Media, Serum-Free; D017468:Receptors, Fibroblast Growth Factor; D016222:Fibroblast Growth Factor 2; D051057:Proto-Oncogene Proteins c-akt