ROS-Responsive Potassium Ionophore-Based Nanoplatform Potentiates Cancer Pyroptosis-Immunotherapy via ER Stress

Pyroptosis is an emerging programmed cell death with great potential in antitumor immunotherapy. However, the actual application of pyroptosis is hampered by its nonspecificity and inefficiency. In this study, a reactive oxygen species (ROS) responsive potassium (K+) ionophore-based nanoplatform rPPAA18C6 is constructed based on the triblock polymers PEG-PPBAEM-PAA18C6 to potentiate cancer pyroptosis and immunotherapy via the K+ metabolic disturbance mediated endoplasmic reticulum (ER) stress. The PEG (P) is used to prolong the circulation time in vivo, PPBAEM (r) is used to target the tumor cells and responds to the higher ROS, and PAA18C6 is used to perturb of K+ homeostasis. Moreover, rPPAA18C6 can also function as a drug carrier for chemodrug (doxorubicin, Dox). We find that rPPAA18C6@Dox provokes immune responses in melanoma (B16F10) via pyroptosis-related immunogenic cell death (ICD), in which damage-associated molecular patterns (DAMPs) are released to promote maturation of dendritic cells (DCs), activate cytotoxic T lymphocytes (CTLs), and convert immunosuppressive “cold” tumor to immunogenic “hot” tumor. Moreover, the combined therapy with anti-PD-L1 exhibits apparent tumor suppression far more than expected, suggesting a powerful candidate of rPPAA18C6@Dox for high-efficient immune checkpoint blockade (ICB) therapy. This study thus provides a promising strategy to specifically initiate pyroptosis and potentiate immunotherapy by perturbation of K+ metabolism via a smart nanoplatform. Overall design: To detect the gene expression of B16F10 cells stimulated with rPPAA18C6@Dox, RNA-Seq was performed by OE Biotech Co., Ltd. Briefly, B16F10 cells were seeded in a 6-well plate at a density of 5.0 × 105 cells/well, and cultured at 37 °C for overnight. Then, the medium was replaced with fresh medium containing PBS and rPPAA18C6@Dox (50 µg/mL). After cultured at 37 °C for 8 h, the cells were collected in RNAiso Plus reagent for RNA isolation.