Comparative evaluation of affibody- and antibody fragments-based CAIX imaging probes in mice bearing renal cell carcinoma xenografts

Sci Rep. 2019 Oct 17;9(1):14907. doi: 10.1038/s41598-019-51445-w.


Carbonic anhydrase IX (CAIX) is a cancer-associated molecular target for several classes of therapeutics. CAIX is overexpressed in a large fraction of renal cell carcinomas (RCC). Radionuclide molecular imaging of CAIX-expression might offer a non-invasive methodology for stratification of patients with disseminated RCC for CAIX-targeting therapeutics. Radiolabeled monoclonal antibodies and their fragments are actively investigated for imaging of CAIX expression. Promising alternatives are small non-immunoglobulin scaffold proteins, such as affibody molecules. A CAIX-targeting affibody ZCAIX:2 was re-designed with the aim to decrease off-target interactions and increase imaging contrast. The new tracer, DOTA-HE3-ZCAIX:2, was labeled with 111In and characterized in vitro. Tumor-targeting properties of [111In]In-DOTA-HE3-ZCAIX:2 were compared head-to-head with properties of the parental variant, [99mTc]Tc(CO)3-HE3-ZCAIX:2, and the most promising antibody fragment-based tracer, [111In]In-DTPA-G250(Fab')2, in the same batch of nude mice bearing CAIX-expressing RCC xenografts. Compared to the 99mTc-labeled parental variant, [111In]In-DOTA-HE3-ZCAIX:2 provides significantly higher tumor-to-lung, tumor-to-bone and tumor-to-liver ratios, which is essential for imaging of CAIX expression in the major metastatic sites of RCC. [111In]In-DOTA-HE3-ZCAIX:2 offers significantly higher tumor-to-organ ratios compared with [111In]In-G250(Fab')2. In conclusion, [111In]In-DOTA-HE3-ZCAIX:2 can be considered as a highly promising tracer for imaging of CAIX expression in RCC metastases based on our results and literature data.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Monoclonal / administration & dosage
  • Antibodies, Monoclonal / chemistry
  • Antibodies, Monoclonal / immunology
  • Antibodies, Monoclonal / pharmacology
  • Antigens, Neoplasm / immunology
  • Antigens, Neoplasm / metabolism
  • Carbonic Anhydrase IX / antagonists & inhibitors*
  • Carbonic Anhydrase IX / immunology
  • Carbonic Anhydrase IX / metabolism
  • Carcinoma, Renal Cell / diagnostic imaging*
  • Carcinoma, Renal Cell / pathology
  • Cell Line, Tumor
  • Female
  • Humans
  • Immunoglobulin Fragments / administration & dosage
  • Immunoglobulin Fragments / immunology
  • Immunoglobulin Fragments / pharmacology
  • Indium Radioisotopes
  • Kidney Neoplasms / diagnostic imaging*
  • Kidney Neoplasms / pathology
  • Mice
  • Molecular Imaging / methods*
  • Molecular Probes / administration & dosage*
  • Molecular Probes / chemistry
  • Molecular Probes / immunology
  • Molecular Probes / pharmacology
  • Radioactive Tracers
  • Single Photon Emission Computed Tomography Computed Tomography / methods
  • Tissue Distribution
  • Xenograft Model Antitumor Assays


  • Antibodies, Monoclonal
  • Antigens, Neoplasm
  • Immunoglobulin Fragments
  • Indium Radioisotopes
  • Molecular Probes
  • Radioactive Tracers
  • Indium-111
  • CA9 protein, human
  • Carbonic Anhydrase IX