title: Combination therapy targeting integrins reduces glioblastoma tumor growth through antiangiogenic and direct antitumor activity and leads to activation of the pro-proliferative prolactin pathway.
abstract: BACKGROUND
  Tumors may develop resistance to specific angiogenic inhibitors via activation of alternative pathways. Therefore, multiple angiogenic pathways should be targeted to achieve significant angiogenic blockade. In this study we investigated the effects of a combined application of the angiogenic inhibitors endostatin and tumstatin in a model of human glioblastoma multiforme.
  
  
  RESULTS
  Inhibitors released by stably transfected porcine aortic endothelial cells (PAE) showed anti-angiogenic activity in proliferation and wound-healing assays with endothelial cells (EC). Interestingly, combination of endostatin and tumstatin (ES + Tum) also reduced proliferation of glioma cells and additionally induced morphological changes and apoptosis in vitro. Microencapsulated PAE-cells producing these inhibitors were applied for local therapy in a subcutaneous glioblastoma model. When endostatin or tumstatin were applied separately, in vivo tumor growth was inhibited by 58% and 50%, respectively. Combined application of ES + Tum, in comparison, resulted in a significantly more pronounced inhibition of tumor growth (83%). cDNA microarrays of tumors treated with ES + Tum revealed an up-regulation of prolactin receptor (PRLR). ES + Tum-induced up-regulation of PRLR in glioma cells was also found in in vitro. Moreover, exogenous PRLR overexpression in vitro led to up-regulation of its ligand prolactin and increased proliferation suggesting a functional autocrine growth loop in these cells.
  
  
  CONCLUSIONS
  Our data indicate that integrin-targeting factors endostatin and tumstatin act additively by inhibiting glioblastoma growth via reduction of vessel density but also directly by affecting proliferation and viability of tumor cells. Treatment with the ES + Tum-combination activates the PRLR pro-proliferative pathway in glioblastoma. Future work will show whether the prolactin signaling pathway represents an additional target to improve therapeutic strategies in this entity.
authors.affiliation: Department of Oncology, Hematology and Bone Marrow Transplantation with Section Pneumology, University Cancer Center Hamburg (UCCH), Universtity Medical Center Hamburg-Eppendorf, Hamburg, Germany. ferrer@uke.de.
authors.forename: Leticia
authors.initials: L
authors.lastname: Oliveira-Ferrer
authors.forename: Jasmin
authors.initials: J
authors.lastname: Wellbrock
authors.forename: Udo
authors.initials: U
authors.lastname: Bartsch
authors.forename: Eva Maria Murga
authors.initials: EM
authors.lastname: Penas
authors.forename: Jessica
authors.initials: J
authors.lastname: Hauschild
authors.forename: Marianne
authors.initials: M
authors.lastname: Klokow
authors.forename: Carsten
authors.initials: C
authors.lastname: Bokemeyer
authors.forename: Walter
authors.initials: W
authors.lastname: Fiedler
authors.forename: Gunter
authors.initials: G
authors.lastname: Schuch
mesh_terms: D020533:Angiogenesis Inhibitors / Q000008:administration & dosage; D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis; D001324:Autoantigens / Q000008:administration & dosage; D001932:Brain Neoplasms / Q000098:blood supply / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D024141:Collagen Type IV / Q000008:administration & dosage; D043169:Endostatins / Q000008:administration & dosage; D005909:Glioblastoma / Q000098:blood supply / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D061307:Human Umbilical Vein Endothelial Cells / Q000187:drug effects / Q000502:physiology; D006801:Humans; D016023:Integrins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051379:Mice; D016513:Mice, SCID; D011981:Receptors, Prolactin / Q000378:metabolism*; D015398:Signal Transduction; D034421:Sus scrofa; D023041:Xenograft Model Antitumor Assays
chemical_list: D020533:Angiogenesis Inhibitors; D001324:Autoantigens; D024141:Collagen Type IV; D043169:Endostatins; D016023:Integrins; D011981:Receptors, Prolactin; C057112:type IV collagen alpha3 chain