Phage Displaying The Epitope Of P53 And Its Study In Tumor Detection

p53 is an important tumor-suppressor gene in human, which has a high mutation rate in variant tumors. On many conditions p53 mutation can induce the production of serum anti-p53 antibodies (p53 Abs). At the early stage of some tumors, the anti-p53 antibodies can be detected. Thus in the studies of tumor, anti-p53 antibodies become a kind of specific marker of tumor, it has important significance to the early diagnosis of tumor and the check-up of tumors on a large scale. Phage display technique is a biological technique incorporating an extrinsic polypeptide into the N-terminal region of coat protein of filament bacteriophage fd. The extrinsic polypeptide is displayed on the surface of the phage and it doesn't loose the primary conformation and the biological activity. It can be employed in variant fields of modern biology because of its function of effector or ligand. In the field of detection of antibody, phage display technique can be used to display a linear epitope of a certain antigen. As the antigen, the hybrid phage is used to detect the specific antibodies. Low cost, convenience, satisfactory specificity and sensitivity of this method of detecting antibodies make it has large application value. In this study, we displayed DO7 epitope (SQAMDDLML) of p53 protein on the surface of the phage fd using phage display technique. The immunological character of the obtained hybrid phage was analyzed through Western blot and phage-ELISA. Then the hybrid phage was used as an antigen to detect the anti-p53 antibodies. The quantity of the antibodies was acted as an index to diagnose tumor. The results demonstrated that the DNA sequence coding DO7 epitope was inserted into the vector p88. The SDS-PAGE showed that the hybrid phage was secreted to the medium and the extrinsic epitope was displayed successfully. The displaying rate was 20-25%. From the analysis of the antigenicity through Western blot and ELISA we found the epitope displayed on the purified phage could bind p53- antibodies specifically. The detection of tumor through ELISA using the hybrid phage as coating antigen showed it has good effect in diagnosing lung cancer, nasopharyngeal cancer and colorectal cancer, and it could be a rapid, effective and cheap method for tumor diagnosis.