A novel 111indium-labeled dual carbonic anhydrase 9-targeted probe as a potential SPECT imaging radiotracer for detection of hypoxic colorectal cancer cells

Siao-Syun Guan; Cheng-Tien Wu; Tse-Zung Liao; Kun-Liang Lin; Cheng-Liang Peng; Ying-Hsia Shih; Mao-Feng Weng; Chun-Tang Chen; Chung-Hsin Yeh; Ying-Chieh Wang; Shing-Hwa Liu

doi:10.1016/j.ejpb.2021.08.004

A novel ¹¹¹indium-labeled dual carbonic anhydrase 9-targeted probe as a potential SPECT imaging radiotracer for detection of hypoxic colorectal cancer cells

Eur J Pharm Biopharm. 2021 Nov:168:38-52. doi: 10.1016/j.ejpb.2021.08.004. Epub 2021 Aug 25.

Affiliations

¹ Institute of Nuclear Energy Research, Atomic Energy Council, Taoyuan, Taiwan.
² Department of Nutrition, China Medical University, Taichung 40402, Taiwan; Master Program of Food and Drug Safety, China Medical University, Taichung 40402, Taiwan.
³ Institute of Toxicology, College of Medicine, National Taiwan University, No.1, Jen-Ai Road Section 1, Taipei 10051, Taiwan; Department of Medical Research, China Medical University Hospital, China Medical University, Taichung, Taiwan; Department of Pediatrics, National Taiwan University Hospital, Taipei, Taiwan. Electronic address: shinghwaliu@ntu.edu.tw.

PMID: 34450241
DOI: 10.1016/j.ejpb.2021.08.004

Abstract

Tumor hypoxia is a common feature in colorectal cancer (CRC), and is associated with resistance to radiotherapy and chemotherapy. Thus, a specifically targeted probe for the detection of hypoxic CRC cells is urgently needed. Carbonic anhydrase 9 (CA9) is considered to be a specific marker for hypoxic CRC diagnosis. Here, a nuclear imaging Indium-111 (¹¹¹In)-labeled dual CA9-targeted probe was synthesized and evaluated for CA9 detection in in vitro, in vivo, and in human samples. The CA9-targeted peptide (CA9tp) and CA9 inhibitor acetazolamide (AAZ) were combined to form a dual CA9-targeted probe (AAZ-CA9tp) using an automatic microwave peptide synthesizer, which then was conjugated with 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) for radioisotope (¹¹¹In) labeling (¹¹¹In-DOTA-AAZ-CA9tp). The assays for cell binding, stability, and toxicity were conducted in hypoxic CRC HCT15 cells. The analyses for imaging and biodistribution were performed in an HCT15 xenograft mouse model. The binding and distribution of ¹¹¹In-DOTA-AAZ-CA9tp were detected in human CRC samples using microautoradiography. AAZ-CA9tp possessed good CA9-targeting ability in hypoxic HCT15 cells. The dual CA9-targeted radiotracer showed high serum stability, high surface binding, and high affinity in vitro. After exposure of ¹¹¹In-DOTA-AAZ-CA9tp to the HCT15-bearing xenograft mice, the levels of ¹¹¹In-DOTA-AAZ-CA9tp were markedly and specifically increased in the hypoxic tumor tissues compared to control mice. ¹¹¹In-DOTA-AAZ-CA9tp also targeted the areas of CA9 overexpression in human colorectal tumor tissue sections. The results of this study suggest that the novel ¹¹¹In-DOTA-AAZ-CA9tp nuclear imaging agent may be a useful tool for the detection of hypoxic CRC cells in clinical practice.

Keywords: Carbonic anhydrase 9-targeted probe; Colorectal cancer; Indium-111 label; SPECT imaging; Tumor hypoxia.

MeSH terms

Acetazolamide / pharmacology
Animals
Antigens, Neoplasm / metabolism*
Carbonic Anhydrase IX / metabolism*
Carbonic Anhydrase Inhibitors / pharmacology
Cell Hypoxia
Cell Line, Tumor
Colorectal Neoplasms / diagnostic imaging*
Colorectal Neoplasms / pathology
Humans
Indium Radioisotopes
Male
Mice
Mice, Inbred BALB C
Mice, Nude
Tissue Distribution
Tomography, Emission-Computed, Single-Photon / methods*
Xenograft Model Antitumor Assays

Substances

Antigens, Neoplasm
Carbonic Anhydrase Inhibitors
Indium Radioisotopes
Indium-111
CA9 protein, human
Carbonic Anhydrase IX
Acetazolamide