Specifically, treating Cell-Derived Xenografts (CDXs) and Patient-Derived Xenografts (PDXs) models developed from T-ALL cell lines and patient samples with 12E7 anti-CD99 CAR T cells has shown delayed leukemia progression and the elimination of infiltrating leukemia cells in the spleen and bone marrow. This evidence concerns the gene CD99 and acute lymphoblastic leukemia.