We utilized differential display to identify differentially expressed mRNAs induced by balloon angioplasty injury. A recently described subunit of the anaphase-promoting complex, APC5, is not expressed in uninjured rat carotid arteries, Expression of APC5 mRNA is detectable as early as 1 day post-injury, reached maximal levels by 3-7 days, and declined by 14 days post-injury. APC5 is not expressed in serum-starved cultured human vascular smooth muscle cells (VSMC), but is strongly induced by mitogenic factors, and to a lesser extent by nonmitogenic cytokines, The kinetics of APC5 expression is associated with cell cycle progression, and corresponds with PCNA expression in PDGF-stimulated human VSMC, Interestingly, APC5 is expressed in most human tissues examined, regardless of their proliferative state. These data are the first description of the cytokine-inducible expression of APC5 and suggest that expression of this gene may represent an important event in the pathogenesis of vascular proliferative diseases.