Induced pluripotent stem (iPS) cells can be generated from differentiated somatic cells by over-expressing a set of specific transcription factors called reprogramming factors. Typically four reprogramming factors are chosen, Oct4, Sox2, Klf4 and c-Myc (OSKM), which are introduced into the target cells through genetic transduction using retroviral or lentiviral vectors.OSKM lentivirus (TET-inducible, Puro) expresses all four reprogramming factors Oct4, Sox2, Klf4 and c-Myc (OSKM) under the control of the Tet responsive promoter with puromycin as a selection marker.