IRE1a silences double stranded RNA through RIDD

Chemotherapy is often combined with immune checkpoint inhibitor (ICI) to enhance immunotherapy responses. Despite the approval of chemo-immunotherapy in multiple human cancers including triple-negative breast cancer (TNBC), immunologically cold tumors remain largely unresponsive due to weak chemotherapy-stimulated immune responses. The mechanisms determining the immunogenicity of chemotherapy in immunologically cold tumors remain largely unknown. Here, we identify the endoplasmic reticulum (ER) stress sensor IRE1a as a critical checkpoint that restricts the immunogenicity of taxane chemotherapy and prevents the innate immune recognition of immunologically cold TNBC. IRE1a RNase silences chemotherapy-induced double-stranded RNA (dsRNA) through RIDD (Regulated IRE1-Dependent Decay) to prevent NLRP3 inflammasome–dependent pyroptosis. Inhibition of IRE1a RNase activity with a selective RNase inhibitor ORIN1001, currently in Phase I clinical trial, allows taxane chemotherapy to induce extensive dsRNA accumulation and activate NLRP3 inflammasome–dependent gasdermin D (GSDMD) cleavage. This triggers pyroptosis and a highly effective immune response in immunologically cold TNBC. Overall design: J2-RIP and paired INPUT controls were performed in biological triplicates.