NRAS and leukemia: Retrovirally co-expressed N-RAS(G12D), a frequent second hit mutation associated with t(8, 21) AML, has been shown to increase CD34 expression levels and colony formation numbers, enhance replating capacity, rendered cells cytokine independent in growth and improved cell engraftment in NOD/SCID mice, thereby suggesting that N-RAS plays a critical role in the stepwise transformation of t(8, 21) leukemia (Chou et al., 2011).