Endoplasmic reticulum-targeted iridium(III) photosensitizer induces pyroptosis for augmented tumor immunotherapy

An ideal tumor treatment strategy involves therapeutic approaches that can enhance the immunogenicity of the tumor microenvironment while simultaneously eliminating the primary tumor. A cholic acid-modified iridium(III) (Ir3) photosensitizer, targeted to the endoplasmic reticulum (ER), has been reported to exhibit potent type I and type II photodynamic therapeutic effects against triple-negative breast cancer (MDA-MB-231). This photosensitizer induces pyroptotic cell death mediated by gasdermin E (GSDME) through photodynamic means and enhances tumor immunotherapy. Mechanistic studies have revealed that complex Ir3 induces characteristics of damage-related molecular patterns (DAMPs) in MDA-MB-231 breast cancer cells under light conditions. These include cell-surface calreticulin (CRT) eversion, extracellular high mobility group box 1 (HMGB1) and ATP release, accompanied by ER stress and increased reactive oxygen species (ROS). Consequently, complex Ir3 promotes dendritic cell maturation and antigen presentation under light conditions, fully activates T cell-dependent immune response in vivo, and ultimately eliminates distant tumors while destroying primary tumors. In conclusion, immune regulation and targeted intervention mediated by metal complexes represent a new and promising approach to tumor therapy. This provides an effective strategy for the development of combined targeted therapy and immunotherapy.