PIM1， which is a part of the Ser/Thr protein kinase family and PIM subfamily， is expressed primarily in B-lymphoid and myeloid cell lines， and is overexpressed in hematopoietic malignancies and in prostate cancer. PIM1 functions as Proto-oncogene with serine/threonine kinase activity involved in cell survival and cell proliferation， consequently providing a selective advantage in tumorigenesis. Both human and orthologous mouse genes have been reported to encode two isoforms resulting from the use of alternative in-frame translation initiation codons， the upstream non-AUG （CUG） and downstream AUG codons.
