Endogenous Stimuli-Activatable Nanomedicine for Immune Theranostics for Cancer

Cancer immunotherapy has witnessed significant advances in the past decade, however challenges associated with immune-related adverse effects and immunosuppressive tumor microenvironment, have hindered their clinical application. Stimuli-activatable nanomedicines hold great potential for improving the efficiency of cancer immunotherapy and minimizing the side effects via tumor-specific accumulation, controllable drug release profile, and combinational therapy by integrating multiple therapeutic regimens. In this review, the recent advances of stimuli-activatable nanomedicines for cancer immunotherapy are first described, with particular focus on endogenous stimuli including pH, glutathione, reactive oxygen species, and excessive enzymes within the tumor microenvironment. Then, the endogenous stimuli-activatable nanomedicines that target tumor cells, immune cells, or periphery immune systems for eliciting sustained systemic immune activation and modulating the immunosuppressive tumor microenvironment, are described. Next, the general mechanisms underlying nanomedicine-based immunotherapy by eliciting anti-tumor immune responses and overcoming immunologic tolerance are described. Further, the emerging application of bioimaging techniques for monitoring immune response and evaluating therapy performance is described. Finally, the authors’ perspectives are provided for the clinical translation of nanomedicine-based cancer immunotherapy.     

Immune Cycle-Based Strategies for Cancer Immunotherapy

The immune system is composed of immune organs, immune cells, and immunoactive substances, which plays a vital role in antitumor immunity in cancer immunotherapy. During the process of the antitumor immune response, many factors are involved in the cancer immune cycle. Therefore, developing intelligent strategies based on the steps of the cancer immune cycle to elicit the immune responses for enhanced cancer immunotherapy is of great significance. In this review, the key factors in each step of the cancer immune cycle are discussed, and then, the intelligent therapeutic strategies for modulating the immune surveillance against cancer are highlighted. Considering the demand for cancer immunotherapy in clinic, some suggestions for constructing new intelligent strategies are also put forward, which will make antitumor immunity more effective and advance the development of cancer immunotherapy.     

A Microenvironment Dual-Responsive Nano-Drug Equipped with PD-L1 Blocking Peptide Triggers Immunogenic Pyroptosis for Prostate Cancer Self-Synergistic Immunotherapy

Induction of immunogenic cell death (ICD) in tumor combined with immune checkpoint blockade (ICB) therapy is widely developed to improve the efficacy of cancer immunotherapy. However, the current ICD induced based on apoptosis, i.e., immunogenic apoptosis, is often restricted in immunogenicity owing to the inflammatory quenching that occurs early in apoptosis. Recently, pyroptosis is demonstrated to be a more efficient ICD form, i.e., immunogenic pyroptosis. The cell contents released during pyroptosis can powerfully activate tumor immunogenicity. Herein, first, it is demonstrated that lower doses of epigenetic drug decitabine can increase GSDME expression in prostate cancer (PCa) RM-1 cells and successfully induce an apoptosis-pyroptosis transition after photodynamic therapy (PDT). Subsequently, a microenvironment dual-responsive nano-drug equipped with PD-L1 blocking peptide (TSD@LSN-D) is developed for self-synergistic cancer immunotherapy. The poorly immunogenic RM-1 PCa model confirm that the powerful antitumor immune response evoked by TSD@LSN-D not only can effectively inhibit the primary tumor but also form a long-term immune memory to prevent PCa recurrence and metastasis. To the best of authors’ knowledge, this work presents the first concept that promotes the apoptosis–pyroptosis transition after tumor PDT through epigenetic modulation. Furthermore, the powerful combination of immunogenic pyroptosis with ICB opens a new platform for PCa immunotherapy.     

Robust Nanovaccine Based on Polydopamine-Coated Mesoporous Silica Nanoparticles for Effective Photothermal-Immunotherapy Against Melanoma

Nanoparticle-based combination therapy strategy of photothermal therapy (PTT) and immunotherapy is an attractive cancer treatment for ablating tumors and eliciting host immune responses. However, this strategy is often hampered by tedious treatment process and limited immune response, and usually needs to be combined with checkpoint blockades to enhance therapeutic effect. Herein, a nanoplatform with mesoporous silica nanoparticles (MSNs) as a vector, which integrated photothermal agent polydopamine (PDA), model antigen ovalbumin (OVA), and antigen release promoter ammonium bicarbonate (ABC) in an easy way for melanoma PTT-immunotherapy is designed. The formulated MSNs-ABC@PDA-OVA nanovaccine exhibits excellent photothermal properties and effectively eliminates primary tumors. Under laser irradiation, the MSNs-ABC@PDA-OVA nanovaccine realizes rapid antigen release and endosome escape, enhances dendritic cells activation and maturation, facilitates migration to tumor-draining lymph nodes, and induces robust antitumor immune responses. Impressively, single injection of MSNs-ABC@PDA-OVA combines with single round of PTT successfully eradicates melanoma tumors with a cure rate of 75% and generates strong immunological memory to inhibit tumor recurrence and lung metastasis. Hence, the research offers a simple and promising strategy of synergistic PTT-immunotherapy to effectively treat cancer.     

Macrophage-Mediated Tumor Cell Phagocytosis: Opportunity for Nanomedicine Intervention

Macrophages are one of the most abundant non-malignant cells in the tumor microenvironment, playing critical roles in mediating tumor immunity. As important innate immune cells, macrophages possess the potential to engulf tumor cells and present tumor-specific antigens for adaptive antitumor immunity induction, leading to growing interest in targeting macrophage phagocytosis for cancer immunotherapy. Nevertheless, live tumor cells have evolved to evade phagocytosis by macrophages via the extensive expression of anti-phagocytic molecules, such as CD47. In addition, macrophages also rapidly recognize and engulf apoptotic cells (efferocytosis) in the tumor microenvironment, which inhibits inflammatory responses and facilitates immune escape of tumor cells. Thus, intervention of macrophage phagocytosis by blocking anti-phagocytic signals on live tumor cells or inhibiting tumor efferocytosis presents a promising strategy for the development of cancer immunotherapies. Here, the regulation of macrophage-mediated tumor cell phagocytosis is first summarized, followed by an overview of strategies targeting macrophage phagocytosis for the development of antitumor therapies. Given the potential off-target effects associated with the administration of traditional therapeutics (for example, monoclonal antibodies and small molecule inhibitors), the opportunity for nanomedicine in macrophage phagocytosis intervention is highlighted.     

Enhancing Triple Negative Breast Cancer Immunotherapy by ICG‐Templated Self‐Assembly of Paclitaxel Nanoparticles

Combination cancer immunotherapy has shown promising potential for simultaneously eliciting antitumor immunity and modulating the immunosuppressive tumor microenvironment (ITM). However, combination immunotherapy with multiple regimens suffers from the varied chemo‐physical properties and inconsistent pharmacokinetic profiles of the different therapeutics. To achieve tumor‐specific codelivery of the immune modulators, an indocyanine green (ICG)‐templated self‐assembly strategy for preparing dual drug‐loaded two‐in‐one nanomedicine is reported. ICG‐templated self‐assembly of paclitaxel (PTX) nanoparticles (ISPN), and the application of ISPN for combination immunotherapy of the triple negative breast cancer (TNBC) are demonstrated. The ISPN show satisfied colloidal stability and high efficacy for tumor‐specific codelivery of ICG and PTX through the enhanced tumor permeability and retention effect. Upon laser irradiation, the ICG component of ISPN highly efficiently induces immunogenic cell death of the tumor cells via activating antitumor immune response through photodynamic therapy. Meanwhile, PTX delivered by ISPN suppresses the regulatory T lymphocytes (T_regs) to combat ITM. The combination treatment of TNBC with ISPN and αPD‐L1‐medaited immune checkpoint blockade therapy displays a synergistic effect on tumor regression, metastasis inhibition, and recurrence prevention. Overall, the ICG‐templated nanomedicine may represent a robust nanoplatform for combination immunotherapy.     

Nanomedicine-Boosting Tumor Immunogenicity for Enhanced Immunotherapy

Immunotherapy has revolutionized oncology remarkably and gained great improvements in cancer therapy. However, tumor immunotherapy still encounters serious challenges, especially certain tumors barely respond to immunotherapy. The lack of immunogenicity and subsequent insufficient antitumor immune activation is a pivotal reason. Here, a general introduction and the strengthening strategies of immunogenicity of a tumor for enhanced immunotherapy are reviewed. Specifically, nanotechnology nowadays is playing important roles in increasing the antitumor efficacy of various treatments, including immunotherapy. This review highlights how nanomedicines integrating one or more anticancer therapeutic methods (e.g., cancer vaccines, chemotherapy, phototherapy, and radiotherapy) to increase the tumor immunogenicity for rousing T cell related immune responses and achieving inspiring antitumor efficacy. Given the sophisticated immune evasion mechanisms, rational designed nanodrugs with combinational formulations are summarized to improve therapeutic efficacy in synergistic ways. Nanoplatforms taking advantage of the distinct features of tumor tissue or tumor cell with stimuli-responsiveness and targeting functions are introduced to accelerate tumor accumulation of drugs successfully and greatly promote therapeutic efficacy with low-dose administration and programmed drug release. Finally, the related challenges and personal perspectives of nanomedicines for tumor immunotherapy are concluded.     

Multifunctional Nanoparticle Loaded Injectable Thermoresponsive Hydrogel as NIR Controlled Release Platform for Local Photothermal Immunotherapy to Prevent Breast Cancer Postoperative Recurrence and Metastases

For breast cancer patients who have undergone breast‐conserving surgery, effective treatments to prevent local recurrences and metastases is very essential. Here, a local injectable therapeutic platform based on a thermosensitive PLEL hydrogel with near‐infrared (NIR)‐stimulated drug release is developed to achieve synergistic photothermal immunotherapy for prevention of breast cancer postoperative relapse. Self‐assembled multifunctional nanoparticles (RIC NPs) are composed of three therapeutic components including indocyanine green, a photothermal agent; resiquimod (R848), a TLR‐7/8 agonist; and CPG ODNs, a TLR‐9 agonist. RIC NPs are physically incorporated into the thermosensitive PLEL hydrogel. The RIC NPs encapsulated PLEL hydrogel (RIC NPs@PLEL) is then locally injected into the tumor resection cavity for local photothermal therapy to ablate residue tumor tissues and produce tumor‐associated antigens. At the same time, NIR also triggers the release of immune components CPG ODNs and R848 from thermoresponsive hydrogels PLEL. The released immune components, together with tumor‐associated antigens, work as an in situ cancer vaccine for postsurgical immunotherapy by inducing effective and sustained antitumor immune effect. Overall, this work suggests that photothermal immunotherapy based on local hydrogel delivery system has great potential as a promising tool for the postsurgical management of breast cancer to prevent recurrences and metastases.     

Sono/Photodynamic Nanomedicine-Elicited Cancer Immunotherapy

Immunotherapy (e.g., cancer vaccines and checkpoint blockades), harnessing the host immune system to recognize and eradicate tumors, has emerged as one of the most potent cancer therapies. The clinical applications of cancer immunotherapies, however, have been limited by their low response rates and immune-related adverse effects. In recent years, sono/photodynamic nanomedicines (SPNs) have received increasing attention for cancer therapy since they have been reported to mediate enhanced immunotherapy by generating reactive oxygen species under site-specific exposure to exogenous energy sources. In particular, SPNs are capable of eliciting immunogenic cancer cell death, leading to the release of tumor-associated antigens and damage-associated molecular patterns. This allows for the maturation of antigen-presenting cells, thus eliminating disseminated or metastatic tumor cells by cytotoxic CD8⁺ T cells. Such immunostimulatory features of SPNs provide opportunities to enhance therapeutic potential by amplifying anticancer immunity when combined with conventional immunotherapeutics, including immune checkpoint inhibitors. This review elaborates on the recent strategies and efforts undertaken by researchers to enhance SPN-elicited cancer immunotherapy. The challenging issues and opportunities for SPNs in the activation of innate or adaptive immune responses and regulation of the tumor immunosuppressive microenvironment are also described.     

Combining Photothermal-Photodynamic Therapy Mediated by Nanomaterials with Immune Checkpoint Blockade for Metastatic Cancer Treatment and Creation of Immune Memory

The pursuit of effective treatments for metastatic cancer is still one of the most intensive areas of research in the biomedical field. In a not-so-distant past, the scientific community has witnessed the rise of immunotherapy based on immune checkpoint inhibitors (ICIs). This therapeutic modality intends to abolish immunosuppressive interactions, re-establishing T cell responses against metastasized cancer cells. Despite the initial enthusiasm, the ICIs were later found to be associated with low clinical therapeutic outcomes and immune-related side effects. To address these limitations, researchers are exploring the combination of ICIs with nanomaterial-mediated phototherapies. These nanomaterials can accumulate within the tumor and produce, upon interaction with light, a temperature increase (photothermal therapy) and/or reactive oxygen species (photodynamic therapy), causing damage to cancer cells. Importantly, these photothermal-photodynamic effects can pave the way for an enhanced ICI-based immunotherapy by inducing the release of tumor-associated antigens and danger-associated molecular patterns, as well as by relieving tumor hypoxia and triggering a pro-inflammatory response. This progress report analyses the potential of nanomaterial-mediated photothermal-photodynamic therapy in combination with ICIs, focusing on their ability to modulate T cell populations leading to an anti-metastatic abscopal effect and on their capacity to generate immune memory that prevents tumor recurrence.     

Smart Injectable Hydrogels for Cancer Immunotherapy

Hydrogels, a class of materials with a 3D network structure, are widely used in various fields especially in biomedicine. Injectable hydrogels could facilitate the encapsulation and controlled release of small molecular drugs, macromolecular therapeutics, and even cells. With the rapid development of cancer immunotherapy, such injectable hydrogels have attracted wide attention for local immunomodulation to boost systemic anticancer immune responses, realizing more effective immunotherapy at lower doses. The latest progresses in the development of various smart injectable hydrogels for cancer immunotherapy are summarized here. Although applied locally, such injectable hydrogels can activate systemic antitumor immune responses, safely and effectively inhibiting the tumor metastasis and recurrence. Moreover, it is discussed how injectable hydrogel‐based cancer immunotherapy would contribute to the development of next generation of cancer treatment together with their potential for clinical translation.     

A Checkpoint-Regulatable Immune Niche Created by Injectable Hydrogel for Tumor Therapy

Current programmed death-1 ligand (PD-L1)-based therapy focuses on local tumors. However, circulating exosomal PD-L1 possesses inherent anti-PD-L1 blockade resistance and dominates tumor metastasis, playing a critical role in systemic immunosuppression. Therefore, the efficacy of immune checkpoint therapy depends on simultaneously decreasing tumoral and circulating exosomal PD-L1. However, such therapeutic platforms have never been reported so far. Herein, a PD-L1 checkpoint-regulatable immune niche created by an injectable hydrogel is reported to reprogram PD-L1 of both tumor and circulating exosomes. Oxidized sodium alginate-armored tumor membrane vesicle (O-TMV) as a gelator, with Ca²⁺ channel inhibitor dimethyl amiloride (DMA) and cyclin-dependent kinase 5 (Cdk5) inhibitor roscovitine formed hydrogel (O-TMV@DR) in vivo, work as an antigen depot to create an immune niche. O-TMV chelates Ca²⁺ within the tumor environment and DMA continuously prevents cellular Ca²⁺ influx, suppressing Ca²⁺-governed exosome secretion with decreased exosome number. Roscovitine not only down-regulates tumor cell PD-L1 expression along with decreasing exosomal PD-L1 expression inherited from parental tumor cells via a genetic blockade effect, but also blunts the cascade connection between PD-L1 up-regulation and interferon-γ stimulation, achieving down-regulated PD-L1 expression in both tumor cells and exosomes. Therefore, a full-scale reprogramming of both tumoral PD-L1 and exosomal PD-L1 is achieved, offering an innovative immune checkpoint-regulatable cancer immunotherapy     

Engineered Oxygen Factories Synergize with STING Agonist to Remodel Tumor Microenvironment for Cancer Immunotherapy

Immunotherapy is a revolutionary achievement in cancer treatment. However, inadequate immune cells infiltration in tumor microenvironment (TME) always leads to treatment failure. Moreover, hypoxic TME hampers normal functions of immune cells. Here, it is found that hypoxia suppresses the STING signaling and immune cells activation in the work. Remodeling tumor immune microenvironment and relieving hypoxia are thus essential for enhancing immunotherapy efficiency. Herein, a spirulina platensis (SP)-based magnetic biohybrid system is constructed as an oxygen factory and loaded with stimulator of interferon genes (STING) agonist ADU-S100 (ADU@Fe-SP) for tumor immunotherapy. Magnet-guided biohybrid SP can actively target tumor tissues and produce oxygen in situ through photosynthesis, which reverses the hypoxic TME and facilitates the function of immune cells. Besides, the targeted delivery of ADU-S100 can activate the STING/TBK1/IRF3 signaling and boost cytokines production in tumor and innate immune cells. The ADU@Fe-SP system thus induces efficient immune cells infiltration in TME, which efficiently inhibits tumor progression and significantly enhances anti-PD-1 therapy efficiency in SCC VII-bearing tumor xenograft. ADU@Fe-SP exerts antitumor effect in a STING-dependent manner by in vivo STING-knockout mice model. The efficiency of this immunotherapy strategy is also demonstrated in patient-derived xenograft model originating from oral cancer, showing great clinical potential.     

Synergy of Immunostimulatory Genetherapy with Immune Checkpoint Blockade Motivates Immune Response to Eliminate Cancer

Normalizing the tumor-induced immune deficiency in the immunosuppressive tumor microenvironment (TME) through increasing the efficient infiltration and activation of antitumoral immunity in TME is the core of promising immunotherapy. Herein, a Cyclo(Arg-Gly-Asp-d -Phe-Lys) (RGD) peptides-modified combinatorial immunotherapy system based on the self-assembly of the nanoparticles named RGD-DMA composed of RGD-PEG-PLA, methoxy poly(ethylene glycol)-poly(lactide) (MPEG-PLA) and 1,2-Dioleoyl-3-trimethylammonium-propane (DOTAP) is used to codeliver the immunostimulatory chemokine CCL19-encoding plasmid DNA (CCL19 pDNA) and immune checkpoint ligand PD-L1 inhibitor (BMS-1). The RGD-DMA/pCCL19-BMS-1 system not only exhibited significant inhibition of tumor progression but also induced locally high concentrations of immunostimulatory cytokines at tumor sites without causing an obviously systemic inflammatory response. The immunosuppressive TME is efficaciously reshaped by the coadministration of RGD-DMA/pCCL19 and BMS-1, as indicated by the activated T lymphocytes, increased intratumoral-infiltration of mature dendritic cells (DCs), and the repolarization of macrophages from pro-tumoral M2-phenotype toward tumoricidal M1-phenotype. The upregulated PD-L1 expression at tumor sites caused by the increased IFN-γ levels after immunostimulatory gene therapy further demonstrated the synergistic effects of BMS-1 in counteracting the inhibitory role of PD-L1 expression in antitumor immunity. Therefore, the combination of immunostimulating therapy and immune checkpoint inhibitor that synergistically target multiple immune regulatory pathways demonstrates significant potential as a novel immunotherapy approach.     

A Smart DNA Nanoassembly Containing Multivalent Aptamers Enables Controlled Delivery of CRISPR/Cas9 for Cancer Immunotherapy

CRISPR/Cas9 system is promising for the reversal of tumor immunosuppression in immunotherapy, but the controlled delivery of CRISPR/Cas9 remains challenging. Herein, the study reported a smart DNA nanoassembly containing multivalent aptamers, realizing the controlled delivery of Cas9/sgRNA ribonucleoprotein (RNP) for enhanced cancer immunotherapy. A single-stranded DNA complementary to sgRNA in the Cas9/sgRNA RNP can initiate a cascade-clamped hybridization chain reaction (C-HCR) to wrap the Cas9/sgRNA RNP up in the DNA nanoassembly. After selective internalization of DNA nanoassembly by cancer cells, Cas9/sgRNA RNP is released to cytoplasm in response to endogenous RNase H and enters the nuclei to knock out β-catenin. The expression of the programmed death-ligand one gene is effectively suppressed, and the immunosuppressive tumor microenvironment is reprogrammed. Meanwhile, the migration of cancer cells is inhibited, and the apoptosis of cancer cells is promoted. In a breast cancer mouse model, the administration of DNA nanoassembly effectively increased the infiltration of CD8⁺ T cells, eventually achieving high therapeutic efficacy.     

A NIR-II Fluorescent PolyBodipy Delivering Cationic Pt-NHC with Type II Immunogenic Cell Death for Combined Chemotherapy and Photodynamic Immunotherapy

Tumor immunotherapy has emerged as one of the most promising clinical techniques to treat cancer tumors. Despite its clinical application, the cancerous immunosuppressive microenvironment limits the therapeutic efficiency of the treatment. To generate a stronger immunogenic therapeutic effect, herein, a platinum complex for chemotherapy and a BODIPY photosensitizer for photodynamic therapy are encapsulated into multimodal type II immunogenic cell death (ICD) induce nanoparticles. As the platinum complex and the photosensitizer are able to induce type II ICD, an exceptionally strong immune response is observed in triple-negative breast cancer cells. While remaining stable and therefore poorly cytotoxic in the dark, the nanomaterial is found to quickly dissociate upon exposure to near-infrared light, causing a multimodal mechanism of action in cancer cells as well as multicellular tumor spheroids through combined chemotherapy, photodynamic therapy, and immunotherapy. The nanoparticles are found to nearly fully eradicate a triple-negative breast cancer tumor and therefore to strongly enhance the survival of tumor-bearing mice models using low drug and light doses.     

A Near-Infrared Light-Responsive ROS Cascade Nanoplatform for Synergistic Therapy Potentiating Antitumor Immune Responses

Tumor occurrence is closely related to the unlimited proliferation and the evasion of the immune surveillance. However, it remains a challenge to kill tumor cells and simultaneously activate antitumor immunity upon spatially localized external stimuli. Herein, a robust tumor synergistic therapeutic nanoplatform is designed in combination with dual photosensitizers-loaded upconversion nanoparticles (UCNPs) and ferric-tannic acid (FeTA) nanocomplex. Dual photosensitizers-loaded UCNPs can induce photodynamic therapy (PDT) effect by generation of cytotoxic reactive oxygen species (ROS) on demand under near-infrared (NIR) light irradiation. FeTA can robustly respond to acidic tumor microenvironment to produce Fe²⁺ and subsequently induce chemodynamic therapy (CDT) by reacting with H₂O₂ in the tumor microenvironment. More importantly, the CDT/PDT synergy can not only exhibit significant antitumor ability but also induce ROS cascade to evoke immunogenic cell death. It increases tumor immunogenicity and promotes immune cell infiltration at tumor sites allowing further introduction of systemic immunotherapy responsiveness to inhibit the primary and distant tumor growth. This study provides a potential tumor microenvironment-responsive nanoplatform for imaging-guided diagnosis and combined CDT/PDT with improved immunotherapy responses and an external NIR-light control of photoactivation.     

An Integrated Nanoaircraft Carrier Modulating Antitumor Immunity to Enhance Immune Checkpoint Blockade Therapy

Immune checkpoint blockade (ICB) therapy revolutionizes cancer therapeutics. However, the effectiveness of ICB therapy is restricted. Focusing on the tumor itself and the immune system, an integrated nanoaircraft carrier that coloaded three therapeutic agents (NNG/OTC) to eradicate tumor cells, enhance T-cells intratumoral infiltration, and relieve the inhibition of tumor immunosuppressive microenvironment (TIM) is designed. First, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is used to combine with oxaliplatin for reducing tumor burden. Second, oxaliplatin is used to elicit immunogenic cell death and combine with cytosine-phosphate-guanine (CpG) to promote dendritic cells maturation, ultimately increasing T-cells intratumoral infiltration. Third, CpG is further used to repolarize M2 type of tumor-associated macrophages, thus reversing immunosuppression of TIM. The nanoaircraft carrier can effectively arrive at the tumor site and detach small-sized nanoparticles under a high concentration of matrix metalloproteinase-2, which promotes deep tumor penetration. Under the mediation of targeting ligands, three therapeutic agents loaded in small-sized nanoparticles could be launched to their target cells. NNG/OTC modulates the antitumor immunity and exhibits excellent tumor inhibition when in combination with ICB therapy, indicating the increased response of ICB therapy. Collectively, NNG/OTC can co-deliver various drugs with different physicochemical properties and provide a promising strategy for enhancing ICB therapy.     

Reversing Immunosuppression in Hypoxic and Immune-Cold Tumors with Ultrathin Oxygen Self-Supplementing Polymer Nanosheets under Near Infrared Light Irradiation

Solid tumors are characterized by a hypoxic and immunologically “cold” microenvironment that dramatically limits the therapeutic outcomes of immunotherapy. Thus, strategies and materials that are capable of reversing immunosuppression in immune-cold tumors are highly desired. Herein, it is reported that oxygen (O₂) self-supplementing conjugated microporous polymer nanosheets can be utilized to elicit a robust antitumor T cell immune response in the hypoxic and immunosuppressive tumor microenvironment. The ultrathin nanosheets can generate O₂ through the water splitting reaction and produce massive reactive oxygen species (ROS) under near infrared light irradiation. Meanwhile, the unique photothermal property of the conjugated polymer nanosheets generates hyperthermia under irradiation. Consequently, they are able to maximize the immunogenic cell death (ICD) performance by inducing adequate damage-related molecular patterns in hypoxic tumors. Other than fostering T cell infiltration by the elicited ICD, the loaded indoleamine 2,3-dioxygenase in nanosheets can reverse the immunosuppression and empower ICD effect for efficient T cells priming. In vivo experiments conclusively prove that the designed polymer nanosheets exhibit great potential for tumor eradication, metastasis prevention, as well as long-term survival. Such a photocatalytic platform opens up new paths for reversing immunosuppression in immune-cold tumors and broadens the application of polymer-based nanosheets for cancer therapy.