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Immunotherapy, represented by immune checkpoint inhibitors (ICIs), has greatly improved the clinical efficacy of malignant tumor therapy. ICI-mediated antitumor responses depend on the infiltration of T cells capable of recognizing and killing tumor cells. ICIs are not effective in \"cold tumors\", which are characterized by the lack of T-cell infiltration. To realize the full potential of immunotherapy and solve this obstacle, it is essential to understand the drivers of T-cell infiltration into tumors. We present a critical review of our understanding of the mechanisms underlying \"cold tumors\", including impaired T-cell priming and deficient T-cell homing to tumor beds. \"Hot tumors\" with significant T-cell infiltration are associated with better ICI efficacy. In this review, we summarize multiple strategies that promote the transformation of \"cold tumors\" into \"hot tumors\" and discuss the mechanisms by which these strategies lead to increased T-cell infiltration. Finally, we discuss the application of nanomaterials to tumor immunotherapy and provide an outlook on the future of this emerging field. The combination of nanomedicines and immunotherapy enhances cross-presentation of tumor antigens and promotes T-cell priming and infiltration. A deeper understanding of these mechanisms opens new possibilities for the development of multiple T cell-based combination therapies to improve ICI effectiveness.

Effectively activating macrophages against cancer is promising but challenging. In particular, cancer cells express CD47, a ‘don’t eat me’ signal that interacts with signal regulatory protein alpha (SIRPα) on macrophages to prevent phagocytosis. Also, cancer cells secrete stimulating factors, which polarize tumor-associated macrophages from an antitumor M1 phenotype to a tumorigenic M2 phenotype. Here, we report that hybrid cell membrane nanovesicles (known as hNVs) displaying SIRPα variants with significantly increased affinity to CD47 and containing M2-to-M1 repolarization signals can disable both mechanisms. The hNVs block CD47-SIRPα signaling axis while promoting M2-to-M1 repolarization within tumor microenvironment, significantly preventing both local recurrence and distant metastasis in malignant melanoma models. Furthermore, by loading a stimulator of interferon genes (STING) agonist, hNVs lead to potent tumor inhibition in a poorly immunogenic triple negative breast cancer model. hNVs are safe, stable, drug loadable, and suitable for genetic editing. These properties, combined with the capabilities inherited from source cells, make hNVs an attractive immunotherapy. The application of STING agonists and the blockade of the SIRPα–CD47 signaling axis are emerging immunotherapeutic strategies. Here the authors show that hybrid cellular membrane nanovesicles loaded with a STING agonist or overexpressing high-affinity SIRPα variants can be exploited to promote anti-tumor immune responses.

The absence of tumor antigens leads to a low response rate, which represents a major challenge in immune checkpoint blockade (ICB) therapy. Pyroptosis, which releases tumor antigens and damage‐associated molecular patterns (DAMPs) that induce antitumor immunity and boost ICB efficiency, potentially leads to injury when occurring in normal tissues. Therefore, a strategy and highly efficient agent to induce tumor‐specific pyroptosis but reduce pyroptosis in normal tissues is urgently required. Here, a smart tumor microenvironmental reactive oxygen species (ROS)/glutathione (GSH) dual‐responsive nano‐prodrug (denoted as MCPP) with high paclitaxel (PTX) and photosensitizer purpurin 18 (P18) loading is rationally designed. The ROS/GSH dual‐responsive system facilitates the nano‐prodrug response to high ROS/GSH in the tumor microenvironment and achieves optimal drug release in tumors. ROS generated by P18 after laser irradiation achieves controlled release and induces tumor cell pyroptosis with PTX by chemo‐photodynamic therapy. Pyroptotic tumor cells release DAMPs, thus initiating adaptive immunity, boosting ICB efficiency, achieving tumor regression, generating immunological memory, and preventing tumor recurrence. Mechanistically, chemo‐photodynamic therapy and control‐release PTX synergistically induce gasdermin E (GSDME)‐related pyroptosis. It is speculated that inspired chemo‐photodynamic therapy using the presented nano‐prodrug strategy can be a smart strategy to trigger pyroptosis and augment ICB efficiency. A smart tumor microenvironmental reactive oxygen species/glutathione dual‐responsive nano‐prodrug (denoted as MCPP) with high paclitaxel and photosensitizer purpurin 18 loading is designed. Chemo‐photodynamic therapy using the presented nano‐prodrug strategy can be a smart strategy to trigger pyroptosis and augment the efficiency of immune checkpoint blockade therapy.

Radiotherapy is an important therapeutic strategy for cancer treatment through direct damage to cancer cells and augmentation of antitumor immune responses. However, the efficacy of radiotherapy is limited by hypoxia-mediated radioresistance and immunosuppression in tumor microenvironment. Here, we construct a stabilized theranostic nanoprobe based on quantum dots emitting in the near-infrared IIb (NIR-IIb, 1,500–1,700 nm) window modified by catalase, arginine–glycine–aspartate peptides and poly(ethylene glycol). We demonstrate that the nanoprobes effectively aggregate in the tumor site to locate the tumor region, thereby realizing precision radiotherapy with few side-effects. In addition, nanoprobes relieve intratumoral hypoxia and reduce the tumor infiltration of immunosuppressive cells. Moreover, the nanoprobes promote the immunogenic cell death of cancer cells to trigger the activation of dendritic cells and enhance T cell-mediated antitumor immunity to inhibit tumor metastasis. Collectively, the nanoprobe-mediated immunogenic radiotherapy can boost the abscopal effect to inhibit tumor metastasis and prolong survival. Hypoxia and immunosuppression contribute to tumor resistance to radiotherapy (RT). Here the authors design a nanoprobe based on NIR-IIb emitting quantum dots for image-guided RT and modified with catalase to relieve hypoxia in the tumor microenvironment, enhancing the precision and efficacy of RT and promoting anti-tumor immune responses.

Immunogenic programmed cell death, such as pyroptosis and ferroptosis, efficiently induces an acute inflammatory response and boosts antitumor immunity. However, the exploration of dual-inducers, particularly nonmetallic inducers, capable of triggering both pyroptosis and ferroptosis remains limited. Here we show the construction of a covalent organic framework (COF-919) from planar and twisted AIEgen-based motifs as a dual-inducer of pyroptosis and ferroptosis for efficient antitumor immunity. Mechanistic studies reveal that COF-919 displays stronger near-infrared light absorption, lower band energy, and longer lifetime to favor the generation of reactive oxygen species (ROS) and photothermal conversion, triggering pyroptosis. Because of its good ROS production capability, it upregulates intracellular lipid peroxidation, leading to glutathione depletion, low expression of glutathione peroxidase 4, and induction of ferroptosis. Additionally, the induction of pyroptosis and ferroptosis by COF-919 effectively inhibits tumor metastasis and recurrence, resulting in over 90% tumor growth inhibition and cure rates exceeding 80%. Pyroptosis and ferroptosis are typically induced by metal species or chemotherapeutic drugs, and able to boost a robust antitumor immunity, however their therapeutic uses have been hindered by the risks arising from metal species or chemotherapeutic drugs. Here the authors report a pyroptosis and ferroptosis dual-inducer based on non-metallic AIEgen-based covalent organic frameworks.

Linking molecules into extended crystalline networks to construct covalent organic frameworks (COFs) added in variety to the readily thriving research on molecule‐based solid‐state materials, featured by classic polymers and molecular crystals. Compared to the development of COFs for gas separation, energy storage, and conversion, where the porosity feature of COFs is utilized, the optical applications, such as fluorescence, white light emission, and photodynamic therapy, involving the molecular and crystalline feature of COFs, are much less explored. In this review, we focused on the optical properties of COFs, and how do these macroscopic properties correlate with the microscopic structure of COFs. Other than the influence from organic functional groups in previous reviews on COFs, here, three critical structure factors, the connection, orientation, and alignment of the molecular building blocks, are outlined and associated with the optical properties of COFs. We also analyze the properties of COFs from both energy and dynamic aspects in an attempt to provide further insight into the possible underlying mechanism. At the end of this review, we also discuss the remaining challenges and future directions for the design of COFs for optical applications, and unveil the potential of COFs toward this direction. In this review, we focus on the impact from geometric arrangement of molecular building blocks within COF backbone, which is closely associated with the optical property. Specifically, three critical structure factors, the connection, orientation and alignment (C, O and A) are extracted to facilitate the understanding of influence from microscopic structure features to their optical behaviors at macroscopic level.

The blood-brain barrier breakdown, as a prominent feature after traumatic brain injury, always triggers a cascade of biochemical events like inflammatory response and free radical-mediated oxidative damage, leading to neurological dysfunction. The dynamic monitoring the status of blood-brain barrier will provide potent guidance for adopting appropriate clinical intervention. Here, we engineer a near-infrared-IIb Ag 2 Te quantum dot-based Mn single-atom catalyst for imaging-guided therapy of blood-brain barrier breakdown of mice after traumatic brain injury. The dynamic change of blood-brain barrier, including the transient cerebral hypoperfusion and cerebrovascular damage, could be resolved with high spatiotemporal resolution (150 ms and ~ 9.6 µm). Notably, the isolated single Mn atoms on the surface of Ag 2 Te exhibited excellent catalytic activity for scavenging reactive oxygen species to alleviate neuroinflammation in brains. The timely injection of Mn single-atom catalyst guided by imaging significantly promoted the reconstruction of blood-brain barrier and recovery of neurological function after traumatic brain injury. Monitoring the status of blood-brain barrier (BBB) and inhibiting reactive oxygen species (ROS)-mediated oxidative damage are key issues in the treatment of traumatic brain injury (TBI). Here, the authors design a near-infrared-IIb emitting Mn single-atom catalyst for imaging-guided therapy to alleviate ROS mediated neuroinflammation in the brain and simultaneously obtain timely feedback of therapeutic effect, promoting the reconstruction of BBB and recovery of neurological function after TBI in mice.

Oncolytic viruses (OVs) show promise as a cancer treatment by selectively replicating in tumor cells and promoting antitumor immunity. However, the current immunogenicity induced by OVs for tumor treatment is relatively weak, necessitating a thorough investigation of the mechanisms underlying its induction of antitumor immunity. Here, we show that HSV-1-based OVs (oHSVs) trigger ZBP1-mediated PANoptosis (a unique innate immune inflammatory cell death modality), resulting in augmented antitumor immune effects. Mechanistically, oHSV enhances the expression of interferon-stimulated genes, leading to the accumulation of endogenous Z-RNA and subsequent activation of ZBP1. To further enhance the antitumor potential of oHSV, we conduct a screening and identify Fusobacterium nucleatum outer membrane vesicle ( Fn -OMV) that can increase the expression of PANoptosis execution proteins. The combination of Fn -OMV and oHSV demonstrates potent antitumor immunogenicity. Taken together, our study provides a deeper understanding of oHSV-induced antitumor immunity, and demonstrates a promising strategy that combines oHSV with Fn -OMV. The potential of oncolytic virus (OV) for cancer therapy is limited by the efficiency of immune response induced. Here the authors show that HSV-1-based OV is capable of triggering ZBP1-mediated PANoptosis resulting in effective tumor growth inhibition.

Effective pyroptosis induction is a promising approach to potentiate cancer immunotherapy. However, the actual efficacy of the present pyroptosis inducers can be weakened by successive biological barriers. Here, a cascaded pH‐activated supramolecular nanoprodrug (PDNP) with a stepwise size shrinkage property is developed as a pyroptosis inducer to boost antitumor immune response. PDNPs comprise multiple poly(ethylene glycol) (PEG) and doxorubicin (DOX) drug–polymer hybrid repeating blocks conjugated by ultra‐pH‐sensitive benzoic imine (bzi) and hydrazone (hyd) bonds. The PEG units endow its “stealth” property and ensure sufficient tumor accumulation. A sharp switch in particle size and detachment of PEG shielding can be triggered by the acidic extracellular pH to achieve deep intratumor penetration. Following endocytosis, second‐stage size switching can be initiated by more acidic endolysosomes, and PDNPs disassociate into ultrasmall cargo to ensure accurate intracellular delivery. The cascaded pH activation of PDNPs can effectively elicit gasdermin E (GSDME)‐mediated pyroptosis to enhance the immunological response. In combination with anti‐PD‐1 antibody, PDNPs can amplify tumor suppression and extend the survival of mice, which suggests a powerful immune adjuvant and pave the way for high‐efficiency immune checkpoint blockade therapy. A cascaded pH‐activated supramolecular nanoprodrug (PDNP) with mutistage size shrinkage property is developed to combat the successive drug delivery barriers. The size‐transformable PDNPs can precise intracellular delivery drug for effectively eliciting pyroptosis and augmenting antitumor immune response, favorable for boosting checkpoint blockade‐based immunotherapy.

Tumor tertiary lymphoid structures (TLS), especially mature TLS (mTLS), have been associated with better prognosis and improved responses to immune checkpoint blockade (ICB), but the underlying mechanisms remain incompletely understood. Here, by performing single-cell RNA, antigen receptor sequencing and spatial transcriptomics on tumor tissue from head and neck squamous cell carcinoma (HNSCC) patients with different statuses of TLS, we observe that mTLS are enriched with stem-like T cells, and B cells at various maturation stages. Notably, progenitor exhausted CD4 + T cells, with features resembling follicular helper T cells, support these responses, by activating B cells to produce plasma cells in the germinal center, and interacting with DC-LAMP + dendritic cells to support CD8 + T cell activation. Conversely, non-mTLS tumors do not promote local anti-tumor immunity which is abundant of immunosuppressive cells or a lack of stem-like B and T cells. Furthermore, patients with mTLS manifest improved overall survival and response to ICB compared to those with non-mTLS. Overall, our study provides insights into mechanisms underlying mTLS-mediated intra-tumoral immunity events against cancer. The reason of mature tertiary lymphoid structures (mTLS) correlates with better prognosis and responses to immune checkpoint blockade (ICB) remains incompletely understood. By employing sequencing and spatial transcriptomics strategies, the authors show that mTLS are enriched with progenitor exhausted CD4 + T cells that promotes activation of T and B cells.