A Dual-motif CAIX Ligand as nuclear imaging agent for of Hypoxic Colorectal Carcinoma Detection in Vivo

Objectives: The tumor hypoxic microenvironment is a continually changed-landscape that impact and influence cancer treatment outcome, which can be a target for precision medicine. Precision medicine is a biomedical health care strategy that provides personalized diagnosis and medical decision making to improve quality of life. However, the hypoxic molecular imaging can play important roles in selecting treatments to match this landscape. Therefore, an accurate diagnosis of tumor hypoxic microenvironment is urgent to increase the therapeutic effects and survival rate in hypoxic cancer. Carbonic anhydrase IX (CA9) is considered to be one of the reliable cellular biomarkers of hypoxia. Therefore, we aimed to utilize the CA9 (sulfonamide derivative) and anti-peptide as a dual-motif probe and label indium-111 for hypoxic CRC imaging detection in vivo. The CA9 trageted peptide (INER-GSS-01) and CA9 inhibitor (acetazolamide, AAZ) was conjugated with 1,4,7,10-Tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) and Indium-111 as a hypoxic tumor agent (¹¹¹In-DOTA-CA9-AAZ) for labeling rate and stability assay. Then, the HCT-15-induced hypoxic animal model was established and intravenous injected 1 mCi ¹¹¹In-DOTA (control group) and ¹¹¹In-DOTA-CA9-AAZ (experimental group). After 24 hours, nanoSPECT / CT was performed to observe the imaging of radio-agent location. The animals were sacrificed for bio-distribution test to confirm the distribution of the drug in the organs and tumor. Finally, we compared the drug distribution of ¹¹¹In-DOTA-CA9-AAZ and ¹⁸FMISO. The labeling efficiency of ¹¹¹In-DOTA-CA9-AAZ was more than 95%. The results displayed that the stability of ¹¹¹In-DOTA-CA9-AAZ was preserved more than 90% for 144 hours in human and mouse serum. The radionuclide imaging was significantly increased in ¹¹¹In-DOTA-CA9-AAZ-treated mice as compared with ¹¹¹In-DOTA-treated mice. For the distributions of ¹¹¹In-DOTA-CA9-AAZ in HCT15-induced xenograft mice, the tumor tissue possessed higher signals as compared with ¹¹¹In-DTPA-treated group. Finally, we observed that the ¹¹¹In-DOTA-CA9-AAZ tumor accumulative level was higher than ¹⁸FMISO at 2 hours. We considered that the radioisotope-labeled agent may be applied in CRC patients for hypoxic tumor imaging toward precision medicine.