Pim deficiency has profound effects on the v-Abl–mediated pre–B-cell transformation. (A) Well numbers per 96-well plate showing cytokine-independent growth of v-Abl–transformed wild-type (WT) and Pim-1^−/−/Pim-2^−/− double knockout (DKO) cells. Plotted are the average well numbers. The error bars represent the SEM (n = 3). (1) Bone marrow cells from DKO and wild-type mice with the same genetic background (mixed background) were used. (2) Mice of 129 strain, which have a genetic background that makes them less susceptible to A-MuLV than the background of the DKO mice, were also included as a control. (B) Bone marrow cells from Pim-1^−/− and Pim-2^−/− mice and their wild-type littermates were infected with A-MuLV. Cells were plated on soft agar medium and transformation efficiency was scored by counting foci generated 2 weeks after infection. Results are shown as fold-difference in the number of foci in the knockout with respect to wild-type mice. (C) Experiments were done as described in panel A. Pim-1^−/−/Pim-2^−/−/Pim-3^−/− (Pim1,2,3^−/−) and wild-type (WT) mice with the same genetic background (FVB/NJ) were used. Plotted are the average well numbers. The error bars represent the SEM (n = 3). (D) Bone marrow cells from Pim-1^−/−/Pim-2^−/−, Pim-1^−/−/Pim-2^−/−/Pim-3^−/−, or wild-type mice were infected with bicistronic retroviruses encoding the p120 form of v-Abl and either Pim-1, Pim-2, Pim-3, or GFP. Transformation efficiency was scored as described in panel A. (E) Ectopic co-expression of Pim-1 with v-Abl allows the transformation of DKO cells by v-Abl. Shown is an immunoblot of v-Abl–transformed cell clones probed as indicated. Control is a v-Abl–transformed clone expressing Pim-2. (F) Ectopic co-expression of Pim-2 with v-Abl also allows the transformation of DKO cells by v-Abl as described in panel E. v-Abl–transformed wild-type (WT) clones were used as a control. Star, transgenic Pim-2; arrow, endogenous Pim-2.