In secondary recipient hosts, Ybx1−/− leukemias showed reduced proliferation (Fig. 2H, Supplementary Fig. 3F), failed to re-establish leukemia in 3/10 recipients (Fig. 2H, I) and significantly prolonged survival compared to Ybx1 + /+ controls (median survival of MA9-Ybx1 + /+ 76 days; MA9-Ybx1−/− 94 days; p = 0.0013**) (Fig. 2I). The gene discussed is YBX1; the disease is leukemia.