But other investigators have highlighted concerns regarding CAR targeting CD133 as a suitable approach for treating MLL-r leukemia because their data indicated that the expression level of PROM1/CD133 in early normal hematopoietic stem cells is equal to or greater than that in B-cell ALL with MLL-AF4 or MLL-AF9 [54]. The gene discussed is PROM1; the disease is leukemia.