Smart Nanoparticles Turn Cold Tumors Hot for Immunotherapy

A groundbreaking advancement in cancer immunotherapy has emerged from researchers at Southwest Jiaotong University in Chengdu, China, who have developed smart polymeric nanoparticles that respond to unique signals within the tumor microenvironment. Published in Cancer Biology & Medicine (DOI: 10.20892/j.issn.2095-3941.2025.0517), the study details how these nanoparticles can overcome the critical challenge of treating “cold” tumors—solid tumors that lack immune cell infiltration and are resistant to current immunotherapies like immune checkpoint blockade (ICB). By engineering nanoparticles that respond to specific endogenous stimuli—such as acidic pH, elevated enzymes, reactive oxygen species (ROS), glutathione (GSH), hypoxia, and adenosine triphosphate (ATP) overexpression—the team has created a delivery system that releases immunotherapy precisely at the tumor site. This targeted approach not only enhances antitumor immune responses but also reduces systemic toxicity, potentially transforming “cold” tumors into immunologically “hot” ones that respond to treatment.

The review highlights several types of tumor microenvironment (TME)-responsive polymeric nanoparticles, each exploiting distinct tumor features. For example, pH-responsive systems use acid-labile bonds like hydrazone or imine to release drugs in the mildly acidic tumor environment (pH ~6.5), while enzyme-responsive nanoparticles incorporate matrix metalloproteinase (MMP)-cleavable peptides for deep tumor penetration. Redox-responsive designs capitalize on elevated ROS and GSH levels in tumors, using thioether or disulfide bonds for drug release. Hypoxia-responsive systems utilize azo derivatives or nitroimidazoles. Multi-responsive platforms, such as ROS/pH dual-responsive nanocarriers (mPEG-b-P(MTE-co-PDA)), can deliver multiple agents like the transcription factor 3 inhibitor nicosamide and synergize with oncolytic viruses (OVs) to induce gasdermin E-mediated pyroptosis, effectively remodeling the immunosuppressive microenvironment and boosting ICB efficacy. The researchers emphasize that “the tumor microenvironment is no longer just a barrier—it has become an opportunity,” and that multi-responsive systems are particularly promising due to their adaptability to the heterogeneous nature of tumors.

This technology holds immediate potential for patients with solid tumors unresponsive to existing immunotherapies, including melanoma, triple-negative breast cancer, glioblastoma, and colorectal cancer. By precisely controlling drug release within the TME, it could reduce severe immune-related adverse events like cytokine release syndrome, making immunotherapy safer for broader patient populations. Beyond cancer, the design principles may extend to other diseases with abnormal microenvironments, such as chronic inflammation and autoimmune disorders. Future clinical translation will require scalable manufacturing, rigorous safety evaluation, and combination strategies with ICB and CAR-T therapies. The original source URL provides further details, and the work was supported by the National Natural Science Foundation of China and other grants. Chuanlink Innovations, where revolutionary ideas meet their true potential, is associated with this research.