Alterations in gene expression in human umbilical cord blood CD34+ hematopoietic progenitor cells after lentiviral vector transduction

Aim: Transplantation of genetically modified human umbilical cord blood (UCB)-derived CD34+ hematopoietic stem/progenitor cells has emerged as a promising therapy for various malignant and non-malignant hematologic disorders. In turn, lentiviral vectors have been considered as suitable gene delivery vehicles for hematopoietic progenitor cells. However, their safety/risk profiles need to be further assessed. This study aimed to analyze the proviral-genomic integration sites and gene expression in human UCB-derived CD34+ cells transduced with a third generation HIV-1-based, vesicular stomatitis virus G glycoprotein-pseudotyped, GFP-tagged self-inactivating lentiviral vector. Materials and Methods: CD34+ cells, isolated from UCB of healthy full-term newborns, were transduced with the lentiviral vector. Proviral-genomic integration sites were analyzed by linear amplification-mediated polymerase chain reaction and DNA sequencing. Differential gene expression was analyzed by cDNA microarray. Results: Seven integration sites were identified. Two genes were up-regulated and six down-regulated, all by more than 2-fold, in the lentiviral vector-transduced CD34+ cells. The two up-regulated genes were IGSF4 (ImmunoGlobin Super Family member 4) and HEC (Highly Expressed in Cancer, rich in leucine heptad repeats), which are involved in leukemia and cell division. Conclusions: Given the importance of some of the differentially expressed genes detected in this study, the safety/risk profiles of lentiviral vectors as gene delivery vehicles for UCB-derived hematopoietic stem/progenitor cells warrant particular attention and further investigations.