CF750-A33scFv-Fc-Based Optical Imaging of Subcutaneous and Orthotopic Xenografts of GPA33-Positive Colorectal Cancer in Mice

Antibody-based imaging agents are attractive as adjuvant diagnostic tools for solid tumors. GPA33 is highly expressed in most human colorectal cancers and has been verified as a diagnostic and therapeutic target. Here, we built an A33scFv-Fc antibody against GPA33 by fusing A33scFv to the Fc fragment of human IgG1 antibodies. The A33scFv-Fc specifically binds GPA33-positive colorectal cancer cells and tumor tissues. After the intravenous injection of mice bearing subcutaneous GPA33-positive LS174T tumor grafts with near-infrared fluorescence probe CF750-labeled A33scFv-Fc (CF750-A33scFv-Fc), high contrast images of the tumor grafts could be kinetically documented within 24 h using an optical imaging system. However, GPA33-negative SMMC7721 tumor grafts could not be visualized by injecting the same amount of CF750-A33scFv-Fc. Moreover, in subcutaneous LS174T tumor-bearing mice, tissue scanning revealed that the CF750-A33scFv-Fc accumulated in the tumor grafts, other than the kidney and liver. In mice with orthotopic tumor transplantations, excrescent LS174T tumor tissues in the colon were successfully removed under guidance by CF750-A33scFv-Fc-based optical imaging. These results indicate that CF750-A33scFv-Fc can target GPA33, suggesting the potential of CF750-A33scFv-Fc as an imaging agent for the diagnosis of colorectal cancer.