TMTP1, a novel tumor-homing peptide specifically targeting metastasis.

PURPOSE Tumor metastasis continues to be the major obstacle to cancer therapy and the leading cause of cancer-related death. Methods used to detect metastasis, especially occult metastases, have received a great deal attention. In this study, a novel selective peptide was assessed for its specific binding to metastasis. METHODS The FliTrx bacterial peptide display system, an alternative to phage peptide display, was used to identify a 5-amino acid peptide termed TMTP1 (NVVRQ), which binds to the highly metastatic prostate cancer cell line PC-3M-1E8. The synthetic TMTP1 was tested in vitro for its binding specificity and affinity to highly metastatic cancer cells. The tumor targeting assays were done in vivo by i.v. injection of FITC-conjugated TMTP1 into tumor-bearing mice. RESULTS TMTP1 specifically bound to a series of highly metastatic tumor cells, including prostate cancer PC-3M-1E8, breast cancer MDA-MB-435S, lung cancer PG-BE1, and gastric cancer MKN-45sci, in vitro and in vivo but not to the poorly metastatic or nonmetastatic cell line, including prostate cancer PC-3M-2B4, breast cancer MCF-7, lung cancer PG-LH7, or murine fibroblast cell NIH/3T3. FITC-TMTP1 strongly and specifically targeted the metastasis foci in tumor-bearing mice 24 h after i.v. peptide injection. Moreover, the occult metastases were specifically detected by FITC-TMTP1. CONCLUSION Our results suggest that TMTP1 is a potential strategy for the development of new diagnostic tracers or alternative anticancer agents for tumor metastasis.