Colorectal cancer (CRC) is the third most common malignancy and the fourth most frequent cause of cancer
deaths worldwide. Ligand-mediated diagnosis and targeted therapy would have vital clinical applications in
cancer treatment. In this study, an orthotopic model of colorectal cancer was established in mice. In vivo phage
library selection was then utilized to isolate peptides specifically recognizing the vasculature of colorectal
cancer tissues. A phage (termed TCP-1 phage) was isolated by this manner and it homed to the colorectal
cancer tissues by 11- to 94-fold more than other organs. Chemical synthetic peptide (CTPSPFSHC, termed
TCP-1) displayed by TCP-1 phage inhibited the homing ability of the phage to the tumor mass when
co-injected intravenously with the TCP-1 phage into mice with colon cancer. Meanwhile, immunostaining
analysis indicated that TCP-1 phage and peptide localized in the vasculature of the colorectal cancer tissue, but
not of normal tissues. Moreover, TCP-1 peptide bound to blood vessels of surgical tissue samples of human
colorectal cancer. After intravenous injection of FITC-labeled TCP-1 into the tumor-bearing mice for 20 h,
there was a strong fluorescent signal in the tumors but not other tissues when observed under blue light. In
addition, TCP-1 conjugated with a pro-apoptotic peptide specifically induced apoptosis of tumor-associated
blood vessels in vivo. The data define a novel peptide TCP-1 as an effective agent for imaging detection and
drug delivery for colorectal cancer.