Since ETV6-RUNX1 expression was maintained constitutively in all hematopoietic cells in the ETV6-ETV6–RUNX1 + Sca1-Cre model (Figure 1B), the results suggested that ETV6-RUNX1 restricted the tumor type to lymphoid ALL, and a second hit further determined the ALL subtype. Here, RUNX1 is linked to acute lymphoblastic leukemia.