title: Differential effects of HOXB4 on nonhuman primate short- and long-term repopulating cells.
abstract: BACKGROUND
  Hematopoietic stem cells (HSCs) or repopulating cells are able to self-renew and differentiate into cells of all hematopoietic lineages, and they can be enriched using the CD34 cell surface marker. Because of this unique property, HSCs have been used for HSC transplantation and gene therapy applications. However, the inability to expand HSCs has been a significant limitation for clinical applications. Here we examine, in a clinically relevant nonhuman primate model, the ability of HOXB4 to expand HSCs to potentially overcome this limitation.
  
  
  RESULTS
  Using a competitive repopulation assay, we directly compared in six animals engraftment of HOXB4GFP (HOXB4 green fluorescent protein) and control (yellow fluorescent protein [YFP])-transduced and expanded CD34+ cells. In three animals, cells were infused after a 3-d transduction culture, while in three other animals cells were infused after an additional 6-9 d of ex vivo expansion. We demonstrate that HOXB4 overexpression resulted in superior engraftment in all animals. The most dramatic effect of HOXB4 was observed early after transplantation, resulting in an up to 56-fold higher engraftment compared to the control cells. At 6 mo after transplantation, the proportion of marker gene-expressing cells in peripheral blood was still up to 5-fold higher for HOXB4GFP compared to YFP-transduced cells.
  
  
  CONCLUSIONS
  These data demonstrate that HOXB4 overexpression in CD34+ cells has a dramatic effect on expansion and engraftment of short-term repopulating cells and a significant, but less pronounced, effect on long-term repopulating cells. These data should have important implications for the expansion and transplantation of HSCs, in particular for cord blood transplantations where often only suboptimal numbers of HSCs are available.
authors.affiliation: Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America.
authors.forename: Xiao-Bing
authors.initials: XB
authors.lastname: Zhang
authors.forename: Brian C
authors.initials: BC
authors.lastname: Beard
authors.forename: Katherine
authors.initials: K
authors.lastname: Beebe
authors.forename: Barry
authors.initials: B
authors.lastname: Storer
authors.forename: R Keith
authors.initials: RK
authors.lastname: Humphries
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Kiem
mesh_terms: D000818:Animals; D018952:Antigens, CD34; D001426:Bacterial Proteins / Q000032:analysis; D018929:Cell Culture Techniques; D002454:Cell Differentiation; D049109:Cell Proliferation; D005819:Genetic Markers; D015316:Genetic Therapy; D005822:Genetic Vectors; D049452:Green Fluorescent Proteins / Q000032:analysis; D006412:Hematopoietic Stem Cells / Q000502:physiology*; D018398:Homeodomain Proteins / Q000096:biosynthesis* / Q000502:physiology*; D008164:Luminescent Proteins / Q000032:analysis; D008254:Macaca nemestrina; D023421:Models, Animal; D012190:Retroviridae; D033581:Stem Cell Transplantation; D014157:Transcription Factors / Q000096:biosynthesis* / Q000502:physiology*; D014161:Transduction, Genetic; D015854:Up-Regulation
chemical_list: D018952:Antigens, CD34; D001426:Bacterial Proteins; D005819:Genetic Markers; D018398:Homeodomain Proteins; D008164:Luminescent Proteins; D014157:Transcription Factors; C054562:yellow fluorescent protein, Bacteria; D049452:Green Fluorescent Proteins