A new non-muscle-invasive bladder tumor-homing peptide identified by phage display in vivo

Bladder cancer is common and widespread, and its incidence is increasing. Many new diagnostic methods combined with state-of-the-art technology have been introduced in cystoscopy to collect real-time images of the bladder mucosa for diagnosis, but often miss inconspicuous early-stage tumors. Fluorophore-labeled peptides with high sensitivity and specificity for cancer would be a desirable tool for the detection and treatment of tiny or residual bladder tumors. Phage display and the human non-muscle-invasive bladder cancer cell line BIU-87 were used to identify a peptide. The isolated phage display peptide (CSSPIGRHC, named NYZL1) was tested in vitro for its binding specificity and affinity. Accumulation into xenograft tumors in a nude mouse model was analyzed with FITC-labeled NYZL1. NYZL1, with strong tumor-homing ability, was identified by in vivo phage library selection in the bladder cancer model. The NYZL1 phage and synthetic FITC-labeled NYZL1 peptides bound to tumor tissues and cells, but were hardly detected in normal control organs. Notably, accumulation of FITC-NYZL1 in bladder tumor cells was time-dependent. Biodistribution studies of xenografts of BIU-87 cells showed accumulation of injected FITC-NYZL1 in the tumors, and the bound peptide could not be removed by perfusion after 24 h. The mouse model of bladder tumor showed increased fluorescence intensity in the tumor-bearing bladder in comparison with normal bladder tissues after 4-6 h. In conclusion, NYZL1 may represent a lead peptide structure applicable in the development of optical molecular imaging.