In the present study, our finding indicated that, transfection with Oct4/Sox2/Klf4/Parp1(OSKP) were capable of the generation of OSKP-iPSCs that formed smaller teratoma than iPSCs reprogrammed with the conventional reprogramming factors Oct4/Sox2/Klf4/c-Myc. This evidence concerns the gene POU5F1 and teratoma.