CD274 and leukemia: Although no significant difference was observed between the frequencies of YFP+ leukemia cells from WT and CD274-null leukemic mice (Fig. 1d, e), the mice transplanted with MLL-AF9-induced CD274-null hematopoietic stem/progenitor cells developed leukemia somewhat more slowly than their WT counterparts (Fig. 1f, p < 0.05).