Detection of Increased ⁶⁴Cu Uptake by Human Copper Transporter 1 Gene Overexpression Using PET with ⁶⁴CuCl₂ in Human Breast Cancer Xenograft Model

Abstract

Copper is an essential cofactor for a variety of biochemical processes including oxidative phosphorylation, cellular antioxidant activity, and elimination of free radicals. The copper transporter 1 is known to be involved in cellular uptake of copper ions. In this study, we evaluated the utility of human copper transporter 1 (hCTR1) gene as a new reporter gene for 64 Cu PET imaging. Methods: Human breast cancer cells (MDA-MB-231) were infected with a lentiviral vector constitutively expressing the hCTR1 gene under super cytomegalovirus promoter, and positive clones (MDA-MB-231-hCTR1) were selected. The expression of hCTR1 gene in MDA-MB-231-hCTR1 cells was measured by reverse transcription polymerase chain reaction, Western blot, and 64 Cu uptake assay. To evaluate the cytotoxic effects induced by hCTR1 expression, the dose-dependent cell survival rate after treatment with cisplatin (Cis-diaminedichloroplatinum (II) [CDDP]) was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and trypan blue dye exclusion. Small-animal PET images were acquired in tumorbearing mice from 2 to 48 h after an intravenous injection of 64 Cu.

Development of 64Cu-NOTA-Trastuzumab for HER2 Targeting: A Radiopharmaceutical with Improved Pharmacokinetics for Human Studies

“…64 Cu, with a half-life of 12.7 h, is the most widely studied PET radioisotope. It can be produced via the 64 Ni(p,n) 64 Cu reaction using a cyclotron in a carrier-free state (17). The optimal structure of the antibody-chelator conjugate for 64 Cu could be used for therapeutic b-emitter 67 Cu (half-life, 2.58 d) as a pair of radioisotopes of 64 Cu (18).…”

PET Imaging of Tenascin-C with a Radiolabeled Single-Stranded DNA Aptamer

“…Shortening the length of the aptamer for future labeling and imaging application may be essential. It has been recently shown that free 64 Cu accumulates in xenograft tumors (25). We addressed this issue by labeling the aptamer with 64 Cu and validating that there is no free copper in the blood and urine.…”

Copper-64: a real theranostic agent

“… 12 , 14 , 16 , 17 Studies of yeast cells were the first to identify the specific genes that encode the proteins responsible for Cu uptake. For example, two proteins that exhibit a high affinity for Cu uptake, Ctr1 and Ctr3, were originally characterized in Saccharomyces cerevisiae , 14 , 16 , 17 while Ctr4 and Ctr5 were found to form heteromeric complexes in Schizosaccharomyces pombe. 17 Subsequently, homology searches of databases and complementation studies of yeast mutants identified both mouse and human CTR1 homologs.…”

“… 17 Subsequently, homology searches of databases and complementation studies of yeast mutants identified both mouse and human CTR1 homologs. 16 In mammals, cellular import of Cu is primarily mediated via Ctr1 and Ctr2, and Ctr1 is the predominant transporter of dietary Cu from the intestinal lumen. 12 Details regarding the mechanisms responsible for mediating Cu uptake by human cells were limited until various Cu-binding proteins, referred to as Cu chaperone proteins, were identified.…”

“…In a cyclotron, the radionuclide, 64 Cu, is produced in no-carrier-added state via a 64 Ni (p,n) 64 Cu reaction. 16 The intermediate half-life of the resulting radionuclide is 12.7 hour and decay occurs via electron capture (44%), β + emission (17%, 0.655 MeV), and β-emission (39%, 0.573 MeV). Electron capture also leads to the release of Auger electrons, thereby facilitating its use for therapy when Cu localizes to cell nuclei.…”