title: PET Imaging of Carbonic Anhydrase IX Expression of HT-29 Tumor Xenograft Mice with (68)Ga-Labeled Benzenesulfonamides.
abstract: Carbonic anhydrase IX (CA-IX) is a HIF-1-inducible enzyme that is overexpressed in many cancer subtypes to promote survival and invasion in hypoxic niches. Pharmacologic inhibition of CA-IX is achievable through sulfonamide-based inhibitors and has been shown to reduce primary growth of cancers and distant metastasis in preclinical models. We explored a multivalent approach for targeting CA-IX in vivo, noninvasively, with positron emission tomography. Three (68)Ga-polyaminocarboxylate chelator complex-conjugated tracers containing one, two, or three 4-(2-aminoethyl)benzenesulfonamide moieties were synthesized and evaluated for protein binding and imaging properties. Binding affinity to CA-I, -II, -IX, and -XII were determined using a stopped-flow CA catalyzed CO2 hydration assay. Biodistribution and PET/CT imaging were performed using immunocompromised mice bearing CA-IX expressing HT-29 colorectal tumors. Compounds demonstrated good binding affinity to CA-IX (Ki: 7.7-25.4 nM). (68)Ga-labeled sulfonamides were obtained in 64-91% decay-corrected average radiochemical yields with 50-536 GBq/μmol specific activity and >97% average radiochemical purity. All three tracers allowed for the visualization of tumor xenografts at 1 h postinjection, with the monomer displaying the highest contrast. Tumor uptake of the monomer was blockable in the presence of acetazolamide, confirming target specificity. The monomer was excreted predominantly through the kidneys, while the dimer and trimer were cleared by both renal and hepatobiliary pathways. According to biodistribution analysis, tumor uptake (%ID/g) of the monomeric, dimeric, and trimeric tracers were 0.81 ± 0.15, 1.93 ± 0.26, and 2.30 ± 0.53 at 1 h postinjection. This corresponded to tumor-to-muscle ratios of 5.02 ± 0.22, 4.07 ± 0.87, and 4.18 ± 0.84, respectively. Our data suggest that (68)Ga-polyaminocarboxylate chelator-conjugated sulfonamides can be used to noninvasively image CA-IX. These CA-IX targeting PET tracers may be used to identify patients who can benefit from treatments targeting this protein or serve as surrogate imaging agents for tumor hypoxia.
authors: Department of Molecular Oncology, BC Cancer Agency , Vancouver, BC, Canada.
authors: Joseph
authors: J
authors: Lau
authors: Department of Molecular Oncology, BC Cancer Agency , Vancouver, BC, Canada.
authors: Zhengxing
authors: Z
authors: Zhang
authors: Department of Molecular Oncology, BC Cancer Agency , Vancouver, BC, Canada.
authors: Silvia
authors: S
authors: Jenni
authors: Department of Molecular Oncology, BC Cancer Agency , Vancouver, BC, Canada.
authors: Hsiou-Ting
authors: HT
authors: Kuo
authors: Department of Chemistry, University of British Columbia , Vancouver, BC, Canada.
authors: Zhibo
authors: Z
authors: Liu
authors: Dipartimento Neurofarba and Laboratorio di Chimica Bioinorganica, Università degli Studi di Firenze , Florence, Italy.
authors: Daniela
authors: D
authors: Vullo
authors: Dipartimento Neurofarba and Laboratorio di Chimica Bioinorganica, Università degli Studi di Firenze , Florence, Italy.
authors: Claudiu T
authors: CT
authors: Supuran
authors: Department of Molecular Oncology, BC Cancer Agency , Vancouver, BC, Canada.|Department of Radiology, University of British Columbia , Vancouver, BC, Canada.
authors: Kuo-Shyan
authors: KS
authors: Lin
authors: Department of Molecular Oncology, BC Cancer Agency , Vancouver, BC, Canada.|Department of Radiology, University of British Columbia , Vancouver, BC, Canada.
authors: François
authors: F
authors: Bénard
mesh_terms: D000818:Animals; D000071231:Carbonic Anhydrase IX / Q000378:metabolism*; D003110:Colonic Neoplasms / Q000000981:diagnostic imaging* / Q000201:enzymology / Q000473:pathology; D004355:Drug Stability; D005455:Fluorescent Antibody Technique; D005710:Gallium Radioisotopes / Q000493:pharmacokinetics*; D006801:Humans; D008297:Male; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D013449:Sulfonamides / Q000737:chemistry*; D014018:Tissue Distribution; D014407:Tumor Cells, Cultured; D023041:Xenograft Model Antitumor Assays; D000096926:Benzenesulfonamides
chemical_list: D000071231:Carbonic Anhydrase IX; D005710:Gallium Radioisotopes; D019275:Radiopharmaceuticals; D013449:Sulfonamides; C097944:4-(2-aminoethyl)benzenesulfonamide; D000096926:Benzenesulfonamides
keywords: benzenesulfonamide; carbonic anhydrase IX; gallium-68; hypoxia; positron emission tomography