NFKBIE and leukemia: However, in vivo BrdU labeling of NSG mice that had received either NFKBIE-wt or NFKBIE-ko cells showed a higher percentage of proliferating leukemia cells in the latter cohort, suggesting that the growth advantage of the NFKBIE-ko cells was at least in part a consequence of a greater capacity to respond to proliferative microenvironmental signals (Fig. 4C).