Hydrogen peroxide self-supplied nanozyme system for synergistic prostate cancer therapy via ferroptosis/pyroptosis and Ca2+ overload-induced apoptosis.

Ferroptosis, an iron-dependent and non-apoptotic regulated cell death mode, has garnered increasing attention in treating cancers with apoptosis resistance. However, the insufficient hydrogen peroxide (H2O2) supply impedes the sustained generation of highly cytotoxic free radicals, resulting in diminished ferroptosis. In addition, monotherapy with ferroptosis inducers frequently shows limited efficacy in cancer management. Thus, promotion of ferroptosis by increasing H2O2 supply, and the development of targeted combination approaches that co-activate multiple cell death pathways are essential to maximize the tumoricidal effects. Herein, we developed a multifunctional targeted nanozyme system pPB-Fe3O4@CaO2-BzATP, in which the pPB targeting cyclic peptide endowed the nanozyme system with enhanced prostate tumor-specific targeting ability. Upon tumor cell internalization, calcium peroxide (CaO2) was hydrolyzed under acidic conditions to produce H2O2 and calcium ions (Ca2+), and iron oxide (Fe3O4) nanozyme catalyzed self-supplied H2O2 to generate highly cytotoxic ·OH, thereby inducing prostate cancer cell death via augmented ferroptosis. Meanwhile, released Ca2+ can trigger calcium overload to elicit apoptosis. Moreover, 2'(3')-O-(4-benzoylbenzoyl)adenosine 5'-triphosphate (BzATP) activated the  P2X7 receptor, which not only enhanced Ca2+ influx to further reinforce calcium overload but also promoted efflux of potassium ions (K+), followed by nucleotide-binding oligomerization domain (NOD)-like receptor pyrin domain containing 3 (NLRP3) inflammasome assembly and ultimately pyroptosis induction. Both in vitro and in vivo studies verified that pPB-Fe3O4@CaO2-BzATP nanozyme system significantly enhanced the tumoricidal efficacy with negligible side effects. Overall, we propose a novel and promising strategy to combat castration-resistant prostate cancer by synergistically integrating ferroptosis, pyroptosis and calcium overload-induced apoptosis into a unified therapeutic modality.