Mouse iPS cells are indistinguishable from ES cells in many aspects and produce germline-competent chimeras. Reactivation of the c-Myc retrovirus, however, results in an increased tumorigenicity in the chimeras and progeny mice, thus hindering clinical applications. In the current study, we developed a modified protocol for the induction of iPS cells, which does not require the Myc retrovirus. Elimination of c-Myc sharply reduces tumorigenesis, as measured by cancer-related deaths of chimeric mice derived from iPS cells. Furthermore, we were able to generate human iPS cells from adult dermal fibroblasts without MYC. These findings are important for the clinical application of this iPS cell technology.
Nakagawa, M., Koyanagi, M., Tanabe, K., Takahashi, K., Ichisaka, T., Aoi, T., Okita, K., Mochiduki, Y., Takizawa, N., and Yamanaka, S. (2008). Generation of induced pluripotent stem cells without Myc from mouse and human fibroblasts. Nat Biotechnol 26, 101-106.