Panning and identification of a colon tumor binding peptide from a phage display peptide library.

Tumor-targeting therapy can be an efficacious way to cure a malignant tumor in clinical trials. Phage display is a molecular diversity technology that allows the presentation of a large number of peptides or proteins on the surface of filamentous phage for various applications. In this study, we report on using phage display to generate peptide libraries that bind to colon cancer tissues. To accomplish this, we developed a screening protocol that contained 3 rounds of in vitro positive panning on colon cancer cells (SW480) and 2 rounds of subtractive screening in vitro on normal human intestinal epithelial cells with a phage display-7 peptide library. After several rounds of panning, both phage titer and recovery efficiency were significantly improved. Through a cell-based enzyme-linked immunosorbent assay, immunofluorescence, in vivo binding assay, immunocytochemical staining, and immunohistochemical staining, peptide CP15 (VHLGYAT) was demonstrated to be the most effective peptide in targeting tumor cells (SW480 and HT29 cells) and tumor tissues but not the normal human intestinal epithelial cells and control colon tissue. These studies suggest that peptide CP15 may be a promising lead candidate in the development of a useful colon tumor diagnostic and targeted drug delivery agent.