Chondroitin Sulfate-Modified Hydroxyapatite for Caspase-1 Activated Induced Pyroptosis through Ca Overload/ER Stress/STING/IRF3 Pathway in Colorectal Cancer.

Immune checkpoint inhibitors, are the fourth most common therapeutic tool after surgery, chemotherapy, and radiotherapy for colorectal cancer (CRC). However, only a small proportion (≈5%) of CRC patients, those with "hot" (immuno-activated) tumors, benefit from the therapy. Pyroptosis, an innovative form of programmed cell death, is a potentially effective means to mediate a "cold" to "hot" transformation of the tumor microenvironment (TME). Calcium-releasing hydroxyapatite (HAP) nanoparticles (NPs) trigger calcium overload and pyroptosis in tumor cells. However, current limitations of these nanomedicines, such as poor tumor-targeting capabilities and insufficient calcium (Ca) ion release, limit their application. In this study, chondroitin sulfate (CS) is used to target tumors via binding to CD44 receptors and kaempferol (KAE) is used as a Ca homeostasis disruptor to construct CS-HAP@KAE NPs that function as pyroptosis inducers in CRC cells. CS-HAP@KAE NPs bind to the tumor cell membrane, HAP released Ca in response to the acidic environment of the TME, and kaempferol (KAE) enhances the influx of extracellular Ca, resulting in intracellular Ca overload and pyroptosis. This is associated with excessive endoplasmic reticulum stress triggered activation of the stimulator of interferon genes/interferon regulatory factor 3 pathway, ultimately transforming the TME from "cold" to "hot".