P21WAF1

P21WAF1 is a cell cycle negative regulatory protein that can reduce the activity of cyclin dependent kinase (CDK) and proliferating cell nuclear antigen (PCNA), which will obstruct the phosphorylation of retinoblastoma protein (Rb) and inhibit DNA replication, thereby preventing the progression of cell cycle. So it has the tumor suppressive effect under normal conditions. Some clinical research suggests that P21 expression is reduced in various tumors such as nasopharyngeal cancer, laryngeal cancer, liver cancer, lung cancer, breast cancer, and ovarian cancer, closely associated with the high aggressiveness, which indicates that P21 has an important prognostic value. However, other scholars have found that P21 is overexpressed in some tumors such as gastric cancer and cervical cancer, which may promote tumor development by regulating the expression of cell migration genes. Therefore, the mechanism of P21 in different tumors has become a research highlight.