RAS is also an important regulator of proliferation through the RAS/RAF/MEK/ERK pathway, and Kras-induced mouse models of T-cell leukemia/lymphoma show a strong association with the development of NOTCH1 mutations.24, 25 Activating N- and K-RAS mutations have been reported in 4–10% T-ALL patients, particularly in early T-cell precursor ALL.14, 21, 26, 27. This evidence concerns the gene NOTCH1 and acute lymphoblastic leukemia.