Mel-18 gene is one of the core members of the PcG (polycomb group) family,which plays an important role in embryogenesis,cell growth and proliferation and self-renewal of stem cells.Mel-18 gene expressing abnormally has been related to human tumorigenesis,development process.Mel-18 serves as a tumor suppressor gene and inhibits tumor growth through transcriptional repression of Bmi-1 and c-myc.Mel-18 expression is decreased at transcriptional and translational levels in most human cancers including breast cancer,prostate cancer,and gastric cancer and other tumors.Mel-18 is expected to become a prognostic marker for human cancers.