Preclinical Theranostic Profiling of [⁶⁴Cu]Cu-Acetate in Prostate Cancer

Copper plays a critical role in cancer biology, with tumor cells exhibiting abnormal copper metabolism that drives proliferation and tumor growth. A limited number of preclinical and clinical studies have reported promising theranostic potential of copper-based radionuclides, such as ⁶⁴Cu, for both diagnostic imaging and targeted radiotherapy in diverse cancers, including prostate cancer (PCa). In this work, we evaluated the cellular uptake and antitumor efficacy of [⁶⁴Cu]Cu-acetate using both cellular and animal models of PCa. Uptake assays revealed that ~70% of the administered dose (10 kBq) was internalized by PC-3 cells within 24 h, predominantly localizing to the cytoplasm, with around 9% detected in the nucleus. These results were corroborated by comparable natural Cu-acetate uptake levels (at equimolar dose) in PC-3 cells, as quantified by ICP-MS. Clonogenic assays revealed a dose-dependent reduction in survival following treatment with [⁶⁴Cu]Cu-acetate (3 and 6 MBq), whereas its non-radioactive counterpart [^NatCu]Cu-acetate, even at excess concentrations (10 µM), had no significant effect. Ex vivo biodistribution studies showed selective tumor accumulation/retention alongside expected hepatic uptake. Clear tumor visualization was achieved using μPET imaging with [⁶⁴Cu]Cu-acetate (10 MBq iv). A single higher dose (65 MBq iv) effectively reduced tumor growth in a subcutaneous PC-3 xenograft mouse model, without systemic toxicity, as evidenced by stable body weight. Together, these results further support the theranostic potential of [⁶⁴Cu]Cu in PCa.