Efficient Derivation of Human Induced Pluripotent Stem Cells with a c-Myc-Free Non-Integrating Episomal Vector

Human induced pluripotent stem cells （hiPSCs） can self-renew indefinitely and have the potential to differentiate into all cell types in the human body, thus hold great promise in regen- erative medicine, drug screening and developmental biology studies. However, integrating retroviral （Takahashi et al., 2007） or lentiviral （Hockemeyer et al., 2008） gene delivery systems and the exogenous oncogene c-Myc （Takahashi et al., 2007; Hockemeyer et al., 2008） have been typically used in the reprogramming process, which could increase risks of insertional mutations or epigenetic abnormalities and conse- quently pose biosecurity concerns for basic research and clinical applications of hiPSCs.