P53 is a tumor suppressor gene located on chromosome 17. The mutation of p53 gene will change its spatial conformation and turn into oncogene, and then lose the regulation of cell growth, apoptosis and DNA repair. The mutation or deletion of p53 gene is the cause of many tumors. Compared with the wild-type protein, the mutant p53 protein has a longer half-life, so it is easier to detect by immunohistochemistry. The p53 mutant protein is expressed in many kinds of tumors, such as breast cancer, gastrointestinal cancer, hepatocellular carcinoma and respiratory tract tumor. It is mainly used for the study of various tumors and can be used as an indicator of tumor prognosis.