SPI1 and leukemia: The resulting leukemias were further phenotyped using flow cytometry with NRAS(G12D) leukemic thymic cells having a more differentiated CD4+/CD8+ immunophenotype and TCF7-SPI1 + NRAS(G12D) leukemic cells a CD4−/CD8−, (intracellular) CD3+ and CD117+ immature immunophenotype (Fig. 4e).