title: MDR1 gene transfer using a lentiviral SIN vector confers radioprotection to human CD34+ hematopoietic progenitor cells.
abstract: Tumor radiotherapy with large-field irradiation results in an increase in apoptosis of the radiosensitive hematopoietic stem cells (CD34(+)). The aim of this study was to demonstrate the radioprotective potential of MDR1 overexpression in human CD34(+) cells using a lentiviral self-inactivating vector. Transduced human undifferentiated CD34(+) cells were irradiated with 0-8 Gy and held in liquid culture under myeloid-specific maturation conditions. After 12 days, MDR1 expression was determined by the rhodamine efflux assay. The proportion of MDR1-positive cells in cells from four human donors increased with increasing radiation dose (up to a 14-fold increase at 8 Gy). Determination of expression of myeloid-specific surface marker proteins revealed that myeloid differentiation was not affected by transduction and MDR1 overexpression. Irradiation after myeloid differentiation also led to an increase of MDR1-positive cells with escalating radiation doses (e.g. 12.5-16% from 0-8 Gy). Most importantly, fractionated irradiation (3 x 2 Gy; 24-h intervals) of MDR1-transduced CD34(+) cells resulted in an increase in MDR1-positive cells (e.g. 3-8% from 0-3 x 2 Gy). Our results clearly support a radioprotective effect of lentiviral MDR1 overexpression in human CD34(+) cells. Thus enhancing repopulation by surviving stem cells may increase the radiation tolerance of the hematopoietic system, which will contribute to widening the therapeutic index in radiotherapy.
authors.affiliation: Department of Radiation Oncology, Mannheim Medical Centre, University of Heidelberg, Theodor-Kutzer-Ufer 1-3, 68167 Mannheim, Germany. patrick.maier@radonk.ma.uni-heidelberg.de
authors.forename: Patrick
authors.initials: P
authors.lastname: Maier
authors.forename: Carsten
authors.initials: C
authors.lastname: Herskind
authors.forename: Katharina
authors.initials: K
authors.lastname: Fleckenstein
authors.forename: Isabel
authors.initials: I
authors.lastname: Spier
authors.forename: Stephanie
authors.initials: S
authors.lastname: Laufs
authors.forename: W Jens
authors.initials: WJ
authors.lastname: Zeller
authors.forename: Stefan
authors.initials: S
authors.lastname: Fruehauf
authors.forename: Frederik
authors.initials: F
authors.lastname: Wenz
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism*; D002470:Cell Survival / Q000528:radiation effects; D002478:Cells, Cultured; D004307:Dose-Response Relationship, Radiation; D005822:Genetic Vectors / Q000235:genetics; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000502:physiology* / Q000528:radiation effects*; D006801:Humans; D016086:Lentivirus / Q000235:genetics*; D011829:Radiation Dosage; D011835:Radiation Protection / Q000379:methods*; D011836:Radiation Tolerance / Q000502:physiology*; D017463:Receptors, Complement 3b / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection / Q000379:methods
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; C509991:CR1 protein, human; D017463:Receptors, Complement 3b; D011994:Recombinant Proteins