Pim protein kinases are a family of serine/threonine kinases consisting of three members of Ca2+/calmodulin-dependent protein kinases, including PIM1, PIM2 and PIM3, that are responsible for cell cycle regulation and antiapoptotic activity as well as homing and migration of receptor tyrosine kinases mediated through the JAK/STAT pathway. All three pim protein kinases share high homology at the amino acid level and hence exhibit greatly overlapping functions, in which 71% and 61% identical amino acids have been found between PIM1/PIM3 and between PIM1/PIM2 respectively. PIM1 comprises two isoforms of 34 and 44 kDa respectively; while PIM2 comprises three isoforms of 34, 37 and 40 kDa respectively. However, PIM3 comprises only one protein.