PET Imaging of Carbonic Anhydrase IX Expression of HT-29 Tumor Xenograft Mice with 68Ga-Labeled Benzenesulfonamides

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• 作者：Joseph Lau ; Zhengxing Zhang ; Silvia Jenni ; Hsiou-Ting Kuo ; Zhibo Liu ; Daniela Vullo ; Claudiu T. Supuran ; Kuo-Shyan Lin ; François Bénard
• 刊名：Molecular Pharmaceutics
• 出版年：2016
• 出版时间：March 7, 2016
• 年：2016
• 卷：13
• 期：3
• 页码：1137-1146
• 全文大小：442K
• ISSN：1543-8392

文摘

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 ⁶⁸Ga-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 (K_i: 7.7–25.4 nM). ⁶⁸Ga-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 ⁶⁸Ga-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.