title: Spontaneous reversion of the angiogenic phenotype to a nonangiogenic and dormant state in human tumors.
abstract: The angiogenic switch, a rate-limiting step in tumor progression, has already occurred by the time most human tumors are detectable. However, despite significant study of the mechanisms controlling this switch, the kinetics and reversibility of the process have not been explored. The stability of the angiogenic phenotype was examined using an established human liposarcoma xenograft model. Nonangiogenic cells inoculated into immunocompromised mice formed microscopic tumors that remained dormant for approximately 125 days (vs. <40 days for angiogenic cells) whereupon the vast majority (>95%) initiated angiogenic growth with second-order kinetics. These original, clonally derived angiogenic tumor cells were passaged through four in vivo cycles. At each cycle, a new set of single-cell clones was established from the most angiogenic clone and characterized for in vivo for tumorigenic activity. A total of 132 single-cell clones were tested in the second, third, and fourth in vivo passage. Strikingly, at each passage, a portion of the single-cell clones formed microscopic, dormant tumors. Following dormancy, like the original cell line, these revertant tumors spontaneously switched to the angiogenic phenotype. Finally, revertant clones were transcriptionally profiled and their angiogenic output determined. Collectively, these data demonstrate that the angiogenic phenotype in tumors is malleable and can spontaneously revert to the nonangiogenic phenotype in a population of human tumor cells.
  
  
  CONCLUSIONS
  Leveraging the rate of reversion to the nonangiogenic phenotype and tumor dormancy may be a novel anticancer strategy.
authors.affiliation: Authors' Affiliations: Departments of Surgery and 2Anesthesia; 3the Vascular Biology Program, Boston Children's Hospital; 4Harvard Medical School, Boston, Massachusetts; 5Department of Microbiology, Haukeland University Hospital; 6Section for Microbiology, The Gade Institute; 7Centre for Cancer Biomarkers CCBIO, Department of Clinical Medicine; and 8Section of Oncology, Institute of Internal Medicine, University of Bergen, Bergen, Norway.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Rogers
authors.forename: Katherine
authors.initials: K
authors.lastname: Novak
authors.forename: David
authors.initials: D
authors.lastname: Zurakowski
authors.forename: Lorna M
authors.initials: LM
authors.lastname: Cryan
authors.forename: Anna
authors.initials: A
authors.lastname: Blois
authors.forename: Eugene
authors.initials: E
authors.lastname: Lifshits
authors.forename: Trond H
authors.initials: TH
authors.lastname: Bø
authors.forename: Anne M
authors.initials: AM
authors.lastname: Oyan
authors.forename: Elise R
authors.initials: ER
authors.lastname: Bender
authors.forename: Michael
authors.initials: M
authors.lastname: Lampa
authors.forename: Soo-Young
authors.initials: SY
authors.lastname: Kang
authors.forename: Kamila
authors.initials: K
authors.lastname: Naxerova
authors.forename: Karl-Henning
authors.initials: KH
authors.lastname: Kalland
authors.forename: Oddbjorn
authors.initials: O
authors.lastname: Straume
authors.forename: Lars A
authors.initials: LA
authors.lastname: Akslen
authors.forename: Randolph S
authors.initials: RS
authors.lastname: Watnick
authors.forename: Judah
authors.initials: J
authors.lastname: Folkman
authors.forename: George N
authors.initials: GN
authors.lastname: Naumov
mesh_terms: D000818:Animals; D048708:Cell Growth Processes / Q000502:physiology; D045744:Cell Line, Tumor; D015870:Gene Expression; D064593:Heterografts; D006801:Humans; D008080:Liposarcoma / Q000098:blood supply* / Q000473:pathology*; D008297:Male; D051379:Mice; D016513:Mice, SCID; D009389:Neovascularization, Pathologic / Q000473:pathology; D010641:Phenotype