Increased proportion of MMC-resistant colonies 4 weeks after transplantation of transduced CD34⁺cells from 2 FA-A patients. The figure illustrates the number of colonies and the proportion of colonies resistant to FA cytotoxic doses of MMC (% of survival to 10 nM MMC) before and 4 weeks after transplantation of FA CD34⁺ cells transduced with the therapeutic PGK-FANCA.Wpre* lentiviral vector into NSG mice (blue bars). As controls, colony numbers generated by samples transduced with the nontherapeutic PGK-EGFP.Wpre* LV or samples from nontransplanted mice (red bars) are also shown. Control cultures showed that no hematopoietic colonies were generated when BM cells from nontransplanted mice were tested.