KRAS and leukemia: Lentiviral vectors have been used to study 1) drug resistant and cell viability genes via loss-of-function mutation in mouse and human cells (Koike-Yusa et al., 2014; Shalem et al., 2014; Wang et al., 2014; Zhou et al., 2014); 2) leukemia causing genes in mouse hematopoietic cells (Heckl et al., 2014); 3) the role of p53 and Pten in the formation of liver tumors using mouse 3T3 cells (Xue et al., 2014a) and 4) Kras gain-of-function mutation (KRAS G12D) in the Neuro-2a neuroblastoma cell line (Platt et al., 2014).