To functionally explore the significance of MEF2C in patients with ETP-ALL, we used the LOUCY line, which has an immature T-ALL phenotype that expresses MEF2C due to a chromosomal rearrangement near the MEF2C locus at chromosomal band 5q14.3 and that lacks NOTCH1 or FBXW7 mutations (13, 15). Here, NOTCH1 is linked to acute lymphoblastic leukemia.