The CD2-Lmo2 transgenic T-ALLs overexpressing Hhex resembled the ETP-ALL subtype in their expression of Lyl1 and Mycn. ETP-ALLs showed a much lower rate of NOTCH1 gene mutation compared to non-ETP cases, analogous to decreased Notch1 target gene activation in the murine Hhex-negative T-ALLs. This evidence concerns the gene HHEX and acute lymphoblastic leukemia.