To determine whether Mapk7 and Atm are functionally linked in tumorigenesis, and given that Atm−/− mice spontaneously develop thymic lymphomas, we removed Mapk7 in the hematopoietic system of Atm−/− mice, and assessed the spontaneous rate of tumor development in Atm−/− and in Atm/Mapk7-double null mice. Here, ATM is linked to thymus lymphoma.