Affinity peptide developed by phage display selection for targeting gastric cancer

AIM: To develop an affinity peptide that binds to gastric cancer used for the detection of early gastric cancer. METHODS: A peptide screen was performed by biopanning the PhD-12 phage display library, clearing non-specific binders against tumor-adjacent normal appearing gastric mucosa and obtaining selective binding against freshly harvested gastric cancer tissues. Tumortargeted binding of selected peptides was confirmed by bound phage counts, enzyme-linked immunosorbent assay, competitive inhibition, fluorescence microscopy and semi-quantitative analysis on immunohistochemistry using different types of cancer tissues. RESULTS: Approximately 92.8% of the non-specific phage clones were subtracted from the original phage library after two rounds of biopanning against normalappearing gastric mucosa. After the third round of positive screening, the peptide sequence AADNAKTKSFPV (AAD) appeared in 25% (12/48) of the analyzed phages. For the control peptide, these values were 6.8 ± 2.3, 5.1 ± 1.7, 3.5 ± 2.1, 4.6 ± 1.9 and 1.1 ± 0.5, respectively. The values for AAD peptide were statistically significant (P < 0.01) for gastric cancer as compared with other histological classifications and control peptide. CONCLUSION: A novel peptide is discovered to have a specific binding activity to gastric cancer, and can be used to distinguish neoplastic from normal gastric mucosa, demonstrating the potential for early cancer detection on endoscopy.