Necroptosis, caspase‐independent programmed necrosis, has emerged as a therapeutic target to make dying cancer cells stimulants for antitumor immune responses. The clinical translations exploiting necroptosis, however, have been limited since most cancer cells downregulate receptor‐interacting protein kinase 3 (RIPK3) as a key enzyme for necroptosis. Herein, nanobubbles (NBs) that can trigger RIPK3‐independent necroptosis, facilitating cell‐membrane rupture via the acoustic cavitation effect are reported. The NBs, imbibing perfluoropentane as the gas precursor, are prepared using an amphiphilic polymer conjugate, composed of PEGylated carboxymethyl dextran as the hydrophilic backbone and chlorin e6 as the hydrophobic sonosensitizer. When exposed to ultrasound, the NBs efficiently promote the release of biologically active damage‐associated molecular patterns by inducing burst‐mediated cell‐membrane disintegration. Consequently, the necroptosis‐inducible NBs significantly improve antitumor immunity by maturation of dendritic cells and activation of CD8+ cytotoxic T cells both in vitro and in vivo. In addition, the combination of NBs and immune checkpoint blockade leads to complete regression of the primary tumor and beneficial therapeutic activity against metastatic tumors in an RIPK3‐deficient CT26 tumor‐bearing mouse model. Overall, the innovative NB that causes immunogenic cell death of cancer via RIPK3‐independent necroptosis is a promising enhancer for cancer immunotherapy.
Cancer immunotherapy is an attractive treatment option under clinical settings. However, the major challenges of immunotherapy include limited patient response, limited tumor specificity, immune-related adverse events, and immunosuppressive tumor microenvironment. Therefore, nanoparticle (NP)-based drug delivery has been used to not only increase the efficacy of immunotherapeutic agents, but it also significantly reduces the toxicity. In particular, NP-based drug delivery systems alter the pharmacokinetic (PK) profile of encapsulated or conjugated immunotherapeutic agents to targeted cancer cells or immune cells and facilitate the delivery of multiple therapeutic combinations to targeted cells using single NPs. Recently, advanced NP-based drug delivery systems were effectively utilized in cancer immunotherapy to reduce the toxic side effects and immune-related adverse events. Repurposing these NPs as delivery systems of immunotherapeutic agents may overcome the limitations of current cancer immunotherapy. In this review, we focus on recent advances in NP-based immunotherapeutic delivery systems, such as immunogenic cell death (ICD)-inducing drugs, cytokines and adjuvants for promising cancer immunotherapy. Finally, we discuss the challenges facing current NP-based drug delivery systems that need to be addressed for successful clinical application.
Recently, metabolic glycoengineering with bioorthogonal click reactions has focused on improving the tumor targeting efficiency of nanoparticles as delivery vehicles for anticancer drugs or imaging agents. It is the key technique for developing tumor-specific metabolic precursors that can generate unnatural glycans on the tumor-cell surface. A cathepsin B-specific cleavable substrate (KGRR) conjugated with triacetylated N-azidoacetyl-d-mannosamine (RR-S-Ac ManNAz) was developed to enable tumor cells to generate unnatural glycans that contain azide groups. The generation of azide groups on the tumor cell surface was exogenously and specifically controlled by the amount of RR-S-Ac ManNAz that was fed to target tumor cells. Moreover, unnatural glycans on the tumor cell surface were conjugated with near infrared fluorescence (NIRF) dye-labeled molecules by a bioorthogonal click reaction in cell cultures and in tumor-bearing mice. Therefore, our RR-S-Ac ManNAz is promising for research in tumor-specific imaging or drug delivery.
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