Development of PSMA-Targeted Liposomal Zinc for Prostate Cancer Therapy

Normal prostate epithelial cells accumulate high intracellular zinc levels that maintain optimum mitochondrial metabolism and proliferation. Prostate cancer cells lose this zinc-accumulating capacity, enabling metabolic reprogramming that supports tumor progression. Restoring intracellular zinc selectively in prostate tumors represents a promising therapeutic strategy; however, systemic zinc administration is limited by the inability of prostate cancer cells to take up free zinc resulting from ZIP1 transporter downregulation. To overcome this challenge, we developed a formulation of prostate-specific membrane antigen (PSMA)-targeted, zinc-loaded liposomes (Zn-TL) to enable tumor-selective intracellular zinc delivery. Zn-TL was prepared with uniform nanoscale size, low polydispersity, and negative surface charge. The formulation showed minimal zinc leakage during storage and sustained retention in vitro. In prostate cancer cells, Zn-TL demonstrated receptor-mediated uptake, resulting in increased cytotoxicity and apoptosis. In vivo, we performed proof-of-principle studies showing prolonged circulation and tumor accumulation of Zn-TL in mice bearing PSMA-positive tumors. While tumor growth was delayed during early and intermediate stages of tumor development, this effect diminished at later stages. The stage-dependent efficacy suggests that Zn-TL may be most effective when used earlier in disease progression. These results also suggest that Zn-TL represents a promising platform for metabolic intervention and may benefit from combination strategies to enhance efficacy in advanced disease.