title: Platelet-derived growth factor BB mediates the tropism of human mesenchymal stem cells for malignant gliomas.
abstract: OBJECTIVE
  Bone marrow-derived human mesenchymal stem cells (hMSCs) are capable of localizing to gliomas after systemic delivery and can be used in glioma therapy. However, the mechanism underlying the tropism of hMSCs for gliomas remains unclear. In vitro studies suggest that platelet-derived growth factor BB (PDGF-BB) may mediate this tropism. However, a causal role of PDGF-BB has not been demonstrated in vivo. Therefore, we tested the hypothesis that PDGF-BB mediates the attraction of hMSCs to gliomas in vitro and in vivo.
  
  
  METHODS
  U87 or LN229 glioma cells were transfected with plasmids encoding human PDGF-B. Stable transfected clones that secreted large amounts of PDFG-BB and clones that produced low levels of PDGF were chosen. In vitro migration of hMSCs toward PDGF-B or conditioned media from high- and low-secreting PDGF-B tumor cells was assessed using Matrigel invasion assays. For in vivo localization studies, hMSCs were tracked by bioluminescence imaging (BLI) after transduction with an adenovirus containing luciferase cDNA. In other studies, hMSCs were labeled with green fluorescent protein (gfp) and analyzed for intratumoral localization by immunohistochemistry.
  
  
  RESULTS
  In vitro invasion assays showed that significantly more hMSCs migrated toward glioma cells engineered to secrete high levels of PDGF-BB compared with low-secreting gliomas. Anti-PDGF-BB-neutralizing antibody abrogated this increase in migration. Pretreatment of hMSCs with inhibitory antibodies against PDGF receptor-beta also reduced hMSC migration. To demonstrate that PDGF-BB mediates the localization of hMSCs in vivo, hMSCs-Ad-Luc were injected into the carotid artery of mice harboring orthotopic 7-day-old U87-PDGF-BB-high secreting or U87-PDGF-BB-low secreting xenografts and analyzed by BLI. Statistically significant increases in hMSCs were seen within PDGF-BB-high xenografts compared with PDGF-BB-low xenografts. To control for PDGF-BB-induced differences in tumor size and vascularity, gfp-labeled hMSCs were injected into the carotid arteries of animals harboring 4-day old PDGF-BB-high secreting xenografts or 7-day old PDGF-BB-low secreting xenografts. At these times tumors had similar size and vessel density. Statistically significant more hMSCs localized to PDGF-BB-high secreting xenografts compared with PDGF-BB-low secreting xenografts. Pretreatment of hMSCs with anti-PDGFR-beta-inhibitory antibodies decreased the localization of hMSCs in this intracranial model.
  
  
  CONCLUSIONS
  PDGF-BB increases the attraction of hMSCs for gliomas in vitro and in vivo, and this tropism is mediated via PDGF-beta receptors on hMSCs. These findings can be exploited for advancing hMSC treatment.
authors.affiliation: Department of Neurosurgery, Brain Tumor Center, The University of Texas M. D. Anderson Cancer Center, Houston, Texas, USA.
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Hata
authors.forename: Naoki
authors.initials: N
authors.lastname: Shinojima
authors.forename: Joy
authors.initials: J
authors.lastname: Gumin
authors.forename: Raymund
authors.initials: R
authors.lastname: Yong
authors.forename: Frank
authors.initials: F
authors.lastname: Marini
authors.forename: Michael
authors.initials: M
authors.lastname: Andreeff
authors.forename: Frederick F
authors.initials: FF
authors.lastname: Lang
mesh_terms: D043925:Angiogenesis Inducing Agents / Q000276:immunology / Q000378:metabolism*; D000818:Animals; D057134:Antibodies, Neutralizing / Q000494:pharmacology; D000077214:Becaplermin; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology*; D004195:Disease Models, Animal; D005910:Glioma / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D049452:Green Fluorescent Proteins / Q000235:genetics; D006801:Humans; D008297:Male; D059630:Mesenchymal Stem Cells / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D010982:Platelet-Derived Growth Factor / Q000235:genetics / Q000276:immunology / Q000378:metabolism* / Q000627:therapeutic use*; D020574:Proto-Oncogene Proteins c-sis; D013997:Time Factors; D014162:Transfection / Q000379:methods; D014183:Transplantation, Heterologous / Q000379:methods; D023041:Xenograft Model Antitumor Assays / Q000379:methods
chemical_list: D043925:Angiogenesis Inducing Agents; D057134:Antibodies, Neutralizing; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D049452:Green Fluorescent Proteins; D000077214:Becaplermin