RASGRF2 and leukemia: As in the case of invasive/metastatic leukemia/lymphomas, this thymus–restricted tumorigenesis was observed, although at lower rates, in one–year–old wild type (≈17%, n = 25) and Rasgrf2–/– (≈22%, n = 20) mice (Figure 4D), further suggesting that Vav1 accentuates the intrinsic tendency of this mouse strain to develop thymic lymphomas rather than promoting tumorigenesis in an autonomous fashion.