pre-iPSCs were isolated during reprogramming with mES-Vc, mES or 5C medium. These pre-iPSCs were further cultured with a different medium (mES-Vc and mES medium) for seven days. Additional factors (Hif1α, Hif1α overexpression; TGFβ, TGFβ1/2/3 1 ng/ml each; 3F, Ctcf, Kdm2b, and Wdr5 overexpression) were used simultaneously with mES medium. The numbers of Oct4GFP+ colonies were determined on day 7 (E). 