In high-risk childhood ALL patients, including those with MLL gene rearrangement, which is the rearrangment of the histone lysine [K]-MethylTransferase 2A gene (KMT2A) gene on chromosome 11q23, blast cells were identified in three different maturation stages (CD34+CD19−, CD34+CD19+, and CD34−CD19+), all of which were capable of re-establishing and reconstituting the original leukemia phenotype in NOD SCID IL2Rgamma deficient -/-gamma (NSG) mice [120]. This evidence concerns the gene CD19 and leukemia.