MCM3 (EP202)

MCM3, minichromosome maintenance protein 3, belongs to the MCM family of highly conserved group of DNA-binding proteins known to have a role in the initiation and regulation of DNA replication during the cell cycle.1-7 MCM3 expression is up-regulated in proliferating cells and absent in terminally differentiated cells. Like Ki-67, MCM3 marks proliferating cells. In a study performed by Endl E., et al., Ki-67 and MCM3 double staining was performed on human tonsil showing that MCM3 stains proliferating cells like Ki-67, and in addition marks cells present in the intermediate layer of epithelium (which are typically negative for Ki-67). Both Ki-67 and MCM3 are not detectable in differentiated cells.6 However, unlike Ki-67, MCM3 protein down-regulation is delayed. This suggests that Ki-67 may be expressed during a shorter interval of the cell cycle than MCM3. Anti-MCM3 may be a more reliable proliferation marker than anti-Ki-67.1