Several researchers had used PD to screen breast cancer cells and obtained some binding peptides, such as aFGF-binding peptide called AP8 (10), novel peptides that specifically bind with CD44 (11), peptide LS-7 (LQNAPRS)-specific CD133-binding ligand (24), and potential highly specific HER2-binding peptides (25). Here, ERBB2 is linked to breast cancer.