Objective To select polypeptide fragment which binds to the highly metastatic prostate cancer PC-3M-1E8 cell line in vitro screened by FliTrx bacterial peptide display system.

Methods Targeting peptides were selected in vitro by screening of the FliTrx library with the paired highly metastatic and non-metastatic human prostate cancer cell lines PC-3M-1E8 and PC-3M-2B4. After bio-selection, the clones with the strongest binding capability were identified, the inserted and repeated motifs were selected and synthesized for further identification. The specific binding capacity of peptides was confirmed by binding assay, competitive inhibition assays and in vivo targeting studies.

Results The target peptide sequences enriched in the selected clone pool was NVVRQ, which we named TMTP1. Binding assay revealed that FITC-TMTP1 specially bounds to highly metastatic prostate cancer cell PC-3M-1E8, but did not bind to the non-metastatic tumor PC-3M-2B4; binding of FITC-TMTP1 and PC-3M-1E8 was concentration-dependent and could be competitively inhibited by free synthetic TMTP1. After i.v. injection, FITC-TMTP1 also specifically targeted primary and metastatic tumors induced by PC-3M-1E8.

Conclusion TMTP1 targets highly metastatic prostate cancer cells in vitro and in vivo. It suggests that TMTP1 is a potential strategy for the development of new diagnostic tracers or alternative anticancer carrier for prostate cancer.