sub:provenance {
  beldoc: dce:description "Approximately 61,000 statements." ;
    dce:rights "Copyright (c) 2011-2012, Selventa. All rights reserved." ;
    dce:title "BEL Framework Large Corpus Document" ;
    pav:authoredBy sub:_4 ;
    pav:version "1.4" .
  sub:_3 prov:value "Like normal tissues, tumours require an adequate supply of oxygen, metabolites and an effective way to remove waste products7. These requirements vary, however, among tumour types, and change over the course of tumour progression8. But gaining access to the host vascular system and the generation of a tumour blood supply are rate-limiting steps in tumour progression. A classical model of the regulation of tumour angiogenesis that has held up nicely in practice is illustrated by a scale laden with anti-angiogenic molecules on one side and pro-angiogenic molecules on the other (FIG. 1). figure 1 angiogenesis activators" ;
    prov:wasQuotedFrom pubmed:12778130 .
  sub:_4 rdfs:label "Selventa" .
  sub:assertion prov:hadPrimarySource pubmed:12778130 ;
    prov:wasDerivedFrom beldoc: , sub:_3 .
}