CCR5 and leukemia: A milestone of TALENs was achieved when they were primarily applied to efficiently disrupt the endogenous genes NTF3 and CCR5 in human leukemia cells via the introduction of NHEJ- or HDR-induced modification into a coding sequence, demonstrating that TALENs could be designed for selective endogenous gene cleavage.73 Interestingly, when TALENs and ZFNs were compared abreast at two human loci (CCR5 and IL2RG), TALENs showed a significant reduction in cytotoxicity.