ATM and leukemia: On the other hand, the splenomegaly of leukaemic mice was relieved in the Atm−/− group, as evidenced by the smaller size and lower weight of the spleen compared to those in the Atm+/+ group (Fig. 1E, F), and leukaemia infiltration was reduced in the spleen and liver in the Atm−/− group as shown by the histology analysis (Fig. 1G).