title: In vivo enrichment of cytidine deaminase gene-modified hematopoietic cells by prolonged cytosine-arabinoside application.
abstract: OBJECTIVE
  Drug-resistance genes have been explored as powerful in vivo selection markers in hematopoietic cell gene therapy, and cytidine deaminase (CDD) represents a particularly attractive candidate given the virtual absence of non-hematopoietic side-effects after low/intermediate dose application of the associated drug cytosine-arabinoside (Ara-C).
  
  
  METHODS
  We investigated the in vivo selection potential of CDD overexpression and prolonged low/intermediate-dose Ara-C application in a murine model. Furthermore, non-transplanted mice were utilized to study Ara-C toxicity in different hematopoietic cell compartments.
  
  
  RESULTS
  Significant protection of myelo- and thrombopoiesis and up to 6-fold in vivo enrichment of CDD-transduced hematopoietic cells was observed. Enrichment was most robust early after Ara-C application and was correlated with dosage and duration of chemotherapy. Enrichment remained significant for several weeks, indicating selection at the level of a progenitor population. This notion was supported by Ara-C toxicity studies, demonstrating profound hematotoxicity and a marked delay in hematopoietic recovery, specifically in the progenitor/stem cell compartment after low/intermediate-dose Ara-C.
  
  
  CONCLUSIONS
  These data support the concept of CDD/Ara-C as a clinically applicable in vivo selection system in hematopoietic gene therapy. The data also demonstrate marked differences in hematotoxicity between alternative Ara-C dosing schemes and suggest thorough in vivo toxicity studies to optimize further Ara-C dosing en route to safe and stable enrichment of gene-corrected hematopoiesis.
authors.affiliation: REBIRTH Cluster-of-Excellence, Research Group Reprogramming, Hannover Medical School, Hannover, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Brennig
authors.forename: Ina
authors.initials: I
authors.lastname: Rattmann
authors.forename: Nico
authors.initials: N
authors.lastname: Lachmann
authors.forename: Axel
authors.initials: A
authors.lastname: Schambach
authors.forename: David A
authors.initials: DA
authors.lastname: Williams
authors.forename: Thomas
authors.initials: T
authors.lastname: Moritz
mesh_terms: D000818:Animals; D003561:Cytarabine / Q000494:pharmacology*; D003564:Cytidine Deaminase / Q000235:genetics / Q000378:metabolism*; D005260:Female; D015316:Genetic Therapy; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL
chemical_list: D003561:Cytarabine; D003564:Cytidine Deaminase