Micro chromosome maintenance protein (MCM) is the main regulator of eukaryotic DNA replication and plays an important role in the initiation and extension of DNA replication. Its family member MCM2 is not expressed in quiescent cells, but overexpressed in proliferating and transforming cells, which can accurately reflect the proliferative activity of cells. In the study of precancerous lesions of colon cancer, lung cancer and other epithelial tissues, MCM2 is better than Ki-67 as a reference basis for cell proliferation. In cervical cancer, the expression of MCM2 can reflect the proliferation of cervical squamous epithelial cells, which is positively correlated with HPV16 infection. MCM2 also contributes to the study of malignant mesothelioma and reactive mesothelial hyperplasia.