Protein kinase Pim-1 is a serine/threonine kinase that has been implicated in the development of hematopoietic and prostatic malignancies. Two isoforms, the 44 and 33 kDa Pim-1, are expressed in all human prostate cancer cell lines examined. The subcellular localization of human 44 kDa Pim-1 is primarily on the plasma membrane, while the 33 kDa isoform is present in both the cytosol and nucleus in PCA cells (1). The nuclear location of Pim-1 is essential for its regulation of the levels of HDM2 protein, and possibly for additional biological activities of this protein kinase. Studies imply a physiological role of the Pim-1 protooncogene during hematopoietic development and a deregulation in various leukemias. Pim-1 is capable of enhancing the rate of occurrence of c-Myc-induced lymphomas, and functions to block factor-withdrawal and genotoxic stress-induced apoptosis. During human fetal hematopoiesis Pim-1 is highly expressed in the liver and spleen. In contrast, at the adult stage it is only slightly expressed in circulating granulocytes (2-3).

WB, IHC, ICC