A Bimetallic Polymerization Network for Effective Increase in Labile Iron Pool and Robust Activation of cGAS/STING Induces Ferroptosis-Based Tumor Immunotherapy

Abstract

Due to the inherent low immunogenicity and immunosuppressive tumor microenvironment (TME) of malignant cancers, the clinical efficacy and application of tumor immunotherapy have been limited. Herein, a bimetallic drug-gene co-loading network (Cu/ZIF-8@U-104@siNFS1-HA) is developed that increased the intracellular labile iron pool (LIP) and enhanced the weakly acidic TME by co-suppressing the dual enzymatic activities of carbonic anhydrase IX (CA IX) and cysteine desulfurylase (NFS1), inducing a safe and efficient initial tumor immunogenic ferroptosis. During this process, Cu²⁺ is responsively released to deplete glutathione (GSH) and reduce the enzyme activity of glutathione peroxidase 4 (GPX4), achieving the co-inhibition of the three enzymes and further inducing lipid peroxidation (LPO). Additionally, the reactive oxygen species (ROS) storm in target cells promoted the generation of large numbers of double-stranded DNA breaks. The presence of Zn²⁺ substantially increased the expression of cGAS/STING, which cooperated with ferroptosis to strengthen the immunogenic cell death (ICD) response and remodel the immunosuppressive TME. In brief, Cu/ZIF-8@U-104@siNFS1-HA linked ferroptosis with immunotherapy through multiple pathways, including the increase in LIP, regulation of pH, depletion of GSH/GPX4, and activation of STING, effectively inhibiting cancer growth and metastasis.

Keywords: carbon anhydrase IX; cysteine desulfurase; ferroptosis; immunogenic cell death; labile iron pool.