Construction and Evaluation of Guanylyl Cyclase C–Specific Antibody for Noninvasive Diagnosis and Targeted Therapy of Colorectal Cancer

Colorectal cancer (CRC) remains the leading cause of cancer mortality worldwide despite therapeutic advances. Guanylyl cyclase C (GUCY2C), an intestinal epithelial receptor, is emerging as a promising diagnostic and therapeutic target for CRC. Thus, we are interested in developing a monoclonal antibody probe targeting GUCY2C for both in vitro and in vivo diagnosis and treatment of CRC. Methods: The GUCY2C-specific monoclonal antibody, PR15-7, was generated by hybridoma fusion. We developed [⁸⁹Zr]Zr-DFO-PR15-7 for PET imaging, Cy5-PR15-7 for near-infrared fluorescence I (NIR-I) detection, and ICG-PR15-7 for NIR-II-guided surgical navigation. The therapeutic potential was evaluated using [¹⁷⁷Lu]Lu-DOTA-PR15-7 for targeted radiotherapy. Biologic properties and antitumor activity of PR15-7 probes were evaluated in vitro and in vivo. Results: PR15-7 showed strong GUCY2C binding affinity and tumor selectivity. PR15-7 probes in antibody-based PET and NIR imaging revealed 3 times higher signal intensity in GUCY2C-positive tumors compared with controls. The NIR-II probe ICG-PR15-7 enabled precise intraoperative tumor visualization and complete resection in orthotopic models. Therapeutic administration of [¹⁷⁷Lu]Lu-DOTA-PR15-7 significantly inhibited tumor growth, with standardized tumor volumes at 16 d being markedly smaller than those in the control groups. Conclusion: We have established both optical and radionuclide probes with PR15-7 as a versatile therapeutic strategy, providing valuable insights into targeted therapy for CRC.