Compared with the T-ALL that developed in recipients of Kras;M14-/- cells, Kras derived tumors contained a significant percentage of CD4−CD8− T-cells, including DN1 (CD44+CD25-) and DN2 (CD44+CD25+) T-cells (Fig. S4A), indicating the development of a significantly immature phenotype. This evidence concerns the gene KRAS and acute lymphoblastic leukemia.