Reprogramming human foreskin fibroblasts without genomic vector integration. (A) Episomal vectors (combination 19 from experiment 3, Table S2). pEF: the eukaryotic elongation factor 1α promoter; pCMV: the cytomegalovirus immediate-early promoter. Transgenes and other features of vectors are indicated by red and green arrows respectively. (B) Bright-field image of iPS cells obtained by transfection of combination 19 episomal vectors (clone DF19-9: “Defined Factor” combination 19, and clone 9). Scale bars, 0.1 mm. (C) Pearson correlation analyses of global gene expression (51,337 transcripts) in human fibroblast-derived iPS cell clones (combination 19). 1-PCC: Pearson Correlation Coefficient. (D) Hematoxylin and eosin staining of teratoma sections of iPS cell clone DF19-9 (53 days after injection). Teratomas were obtained from all ten iPS-DF19 clones. Scale bars, 0.1 mm. (E) PCR analysis of episomal DNA in iPS-DF19 clone 1 to 10. G: genomic DNA template; E: episomal DNA template. Genomic and episomal DNA from nontransfected and combination 19 episomal vector-transfected (day 17 posttransfection) fibroblasts were used as negative (−) and positive (+) controls respectively. 32 PCR cycles were used for all primer sets.