Variation in the safety of induced pluripotent stem cell lines

The safety of induced pluripotent stem cells seems to depend on how they were generated. Miura et al. examine the effects of the c-myc transgene, tissue of origin and selection method on the tumor-forming propensity of iPS-cell derivatives. We evaluated the teratoma-forming propensity of secondary neurospheres (SNS) generated from 36 mouse induced pluripotent stem (iPS) cell lines derived in 11 different ways. Teratoma-formation of SNS from embryonic fibroblast–derived iPS cells was similar to that of SNS from embryonic stem (ES) cells. In contrast, SNS from iPS cells derived from different adult tissues varied substantially in their teratoma-forming propensity, which correlated with the persistence of undifferentiated cells.