Nigericin Boosts Anti-Tumor Immune Response via Inducing Pyroptosis in Triple-Negative Breast Cancer

SIMPLE SUMMARY: The response rate of advanced triple-negative breast cancer (TNBC) to immune checkpoint inhibitors remains unsatisfactory. Recent studies showed that inducing pyroptosis in tumor cells can amplify the anti-tumor immune response by turning “cold” tumors into “hot” tumors. Here, we demonstrated that the antibiotic nigericin caused TNBC cell death by inducing concurrent Caspase-1/GSDMD-mediated pyroptosis and Caspase-3-mediated apoptosis. Notably, we found that nigericin-induced pyroptosis promoted the infiltration and activation of T cells, as well as showing a synergistic therapeutic effect when combined with anti-PD-1 antibody treatment. This study provides a potential strategy to utilize nigericin to boost the anti-tumor immune responses required to treat advanced TNBC. ABSTRACT: Although immune checkpoint inhibitors improved the clinical outcomes of advanced triple negative breast cancer (TBNC) patients, the response rate remains relatively low. Nigericin is an antibiotic derived from Streptomyces hydrophobicus. We found that nigericin caused cell death in TNBC cell lines MDA-MB-231 and 4T1 by inducing concurrent pyroptosis and apoptosis. As nigericin facilitated cellular potassium efflux, we discovered that it caused mitochondrial dysfunction, leading to mitochondrial ROS production, as well as activation of Caspase-1/GSDMD-mediated pyroptosis and Caspase-3-mediated apoptosis in TNBC cells. Notably, nigericin-induced pyroptosis could amplify the anti-tumor immune response by enhancing the infiltration and anti-tumor effect of CD4+ and CD8+ T cells. Moreover, nigericin showed a synergistic therapeutic effect when combined with anti-PD-1 antibody in TNBC treatment. Our study reveals that nigericin may be a promising anti-tumor agent, especially in combination with immune checkpoint inhibitors for advanced TNBC treatment.