PIM1 belongs to the Ser/Thr protein kinase family, and PIM subfamily. This protein is expressed primarily in B-lymphoid and myeloid cell lines, and is overexpressed in hematopoietic malignancies and in prostate cancer. It plays a role in signal transduction in blood cells, contributing to both cell proliferation and survival, and thus provides a selective advantage in tumorigenesis. Both the human and orthologous mouse genes have been reported to encode two isoforms (with preferential cellular localization) resulting from the use of alternative in-frame translation initiation codons, the upstream non-AUG (CUG) and downstream AUG codons. Recombinant human Pim1 protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.