HOXA9 expression increases Pim1 protein and RNA levels in hematopoietic cells. The human myelomonocytic cell line U937 (A) and bone marrow cells from 5-FU–treated Hoxa9^−/− animals (B) were transduced with the same 3 vectors as described in Figure 1. Protein isolated from the cells 4 days after transfection was subjected to Western-blot analysis for Pim1 and HOXA9. While both wild-type and mutant HOXA9 vectors produced equivalent amounts of HOXA9 protein, only the wild-type protein induced Pim1 expression. (C) Pim1 protein levels are reduced in fetal liver cells from Hoxa9^−/− mice. Protein isolated from Lin⁻ cells from day-15.5 fetal livers from wild-type and Hoxa9^−/− mice was subjected to Western-blot analysis for Pim1. Pim1 protein was reduced almost 6-fold in the Hoxa9^−/− fetal liver cells. The number under the Pim1 lanes represents the relative amounts of protein compared with the control lane as measured by densitometric scanning of the Pim1 bands after normalization for loading, using either tubulin (A) or actin (B-C) as a loading control.