No Evidence for Clonal Selection Due to Lentiviral Integration Sites in Human Induced Pluripotent Stem Cells (original) (raw)

Derivation of induced pluripotent stem (iPS) cells requires the expression of defined transcription factors (among Oct3/4, Sox2, Klf4, c-Myc, Nanog, and Lin28) in the targeted cells. Lentiviral or standard retroviral gene transfer remains the most robust and commonly used approach. Low reprogramming frequency overall, and the higher efficiency of derivation utilizing integrating vectors compared to more recent nonviral approaches, suggests that gene activation or disruption via proviral integration sites (IS) may play a role in obtaining the pluripotent phenotype. We provide for the first time an extensive analysis of the lentiviral integration profile in human iPS cells. We identified a total of 78 independent IS in eight recently established iPS cell lines derived from either human fetal fibroblasts or newborn foreskin fibroblasts after lentiviral gene transfer of Oct4, Sox2, Nanog, and Lin28. The number of IS ranged from 5 to 15 IS per individual iPS clone, and 75 IS could be ass...