Identification and characterization of a novel phage display-derived peptide with affinity for human brain metastatic breast cancer

A novel peptide, BRBP1 (MYPWTEPSYLSN), was identified using an in vitro phage biopanning strategy against human brain-seeking breast carcinoma cells (231-BR cells).The peptide-phage clone, BRBP1-M13 displaying BRBP1 sequence, specifically bound to 231-BR cells and the binding could be competitively abolished by BRBP1. In vivo distribution studies showed that BRBP1-M13 preferentially homed to the 231-BR tumors. Fluorescently-labeled BRBP1, BRBP1-K(5-TAMRA), preferentially bound to 231-BR cells in a dose-dependent and energy-dependent manner and it was efficiently internalized into the cells after 2 h incubation. Near-infrared fluorophores imaging demonstrated the accumulation of Cy5.5-conjugated BRBP1 peptide in the tumors in vivo. Thus, BRBP1 is a promising peptide binding to human brain metastatic breast cancer and it may be applied to targeted delivery of cytotoxic agents to the intended tumor.