The advent of induced pluripotent stem cell (iPSC) technology holds great promise to revolutionize personalized cell-based therapies.1,2,3,4,5 Recent advances in gene transfer technology therefore open up exciting possibilities for efficient and safe genetic modification of autologous cells in this context.6 As potential therapeutic applications are being considered, attention has begun to be focused on issues of safety in the clinical arena. This has arisen in part from efforts to understand the biology of reprogramming as well as from an increasing capability to scrutinize the genome and epigenome at high resolution.