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.