Self-Delivery Photo-Immune Stimulators for Photodynamic Sensitized Tumor Immunotherapy

Tumor Microenvironment-Responsive Yolk-Shell NaCl@Virus-Inspired Tetrasulfide-Organosilica for Ion-Interference Therapy via Osmolarity Surge and Oxidative Stress Amplification

Ion-interference therapy, which utilizes ions to disturb intracellular biological processes, provides inspiration for tumor therapy. Artificially reversing osmotic pressure by transporting large amounts of physiological ions to tumor cells is a straightforward yet low-toxic strategy for ion-interference therapy. However, it is hard to achieve due to the serious limitations of single-ion delivery. Herein, we skillfully deliver NaCl nanocrystals to tumor sites and sequentially realize the explosive release of Na⁺/Cl^- inside tumor cells by utilizing a virus-mimicking and glutathione (GSH)-responsive hollow mesoporous tetrasulfide-bridged organosilica (ssss-VHMS). Once the ssss-VHMS-wrapped NaCl nanocrystals (NaCl@ssss-VHMS) accumulate in the tumors, they would rapidly invade tumor cells via spike surface-assisted endocytosis, thus bypassing Na⁺/K⁺-ATPase transmembrane ion transporters. Afterward, the intracellular overproduced GSH of tumor cells would trigger the rapid degradation of ssss-VHMS via thiol-tetrasulfide exchange, which could not only remarkably deplete the GSH but also explosively release the Na⁺/Cl^-, leading to the osmolarity surge accompanied by reactive oxygen species (ROS) generation. The cell swelling, ROS storm, and GSH exhaustion of NaCl@ssss-VHMS effectively eradicated tumor cells by caspase-1-dependent pyroptosis, caspase-3-dependent apoptosis, and GPX4-dependent ferroptosis, respectively, thus synergistically inhibiting tumor growth. We believe that NaCl@ssss-VHMS would be a potential cancer therapeutic agent, and this discovery could provide a perspective for exploring synergistic ion-interference therapy.

Watson-Crick Base Pairing-Inspired Laser/GSH Activatable miRNA-Coordination Polymer Nanoplexes for Combined Cancer Chemo-Immuno-Photothermal Therapy

The tumor immunosuppressive microenvironment (TIM) greatly hindered the efficacy of cancer immunotherapy. Overexpressed indoleamine 2,3-dioxygenase-1 (IDO1) in tumor tissues plays a vital role in TIM generation, and downregulation of IDO1 expression may reverse TIM. Inspired by the Watson-Crick base-pairing rule, a versatile noncationic miRNA vector (miDAC@PDA) is developed for cancer immunotherapy. Doxorubicin (DOX), adenosine triphosphate (ATP), and copper ions (Cu²⁺) are coassembled into coordination polymer nanoparticles (DAC) and bind miRNA via the hydrogen bond interaction (miDAC) between adenine residues (ATP) and uracil residues (miRNA). Polydopamine (PDA) is deposited onto the surface of miDAC for photothermal therapy. miDAC@PDA can efficiently accumulate into tumor tissues for cellular uptake. Under laser irradiation and high intracellular GSH levels, the PDA shell of miDAC@PDA can dissociate from miDAC for miRNA release due to local hyperthermia. Cu²⁺-mediated GSH consumption and intracellular ATP release can amplify the DOX-based immunogenic cell death (ICD) cascade, together with miR-448-mediated IDO1 inhibition, and these versatile nanoplexes will not only restrain primary tumor growth but also display a remarkable abscopal effect on distant tumors. Collectively, our study provides a unique strategy for intracellular gene delivery and an inspirational approach for multimechanism cancer management.

Iron ion-coordinated carrier-free supramolecular co-nanoassemblies of dual DNA topoisomerase-targeting inhibitors for tumor suppression

Overexpressed DNA topoisomerase II alpha (TOP-2A) is closely related to the invasion and metastasis of malignant breast tumors. Mitoxantrone (MTX) has been identified as a TOP-2A inhibitor with significant inhibitory activity against breast tumors. The tumor-homing ability of MTX has been further enhanced by using nanodrug delivery systems (nano-DDSs), reducing off-target side effects. However, conventional MTX nano-DDSs are still limited by low drug-loading capacity and material carrier-related toxicity. In this study, we developed metal iron-coordinated carrier-free supramolecular co-nanoassemblies of dual DNA topoisomerase-targeting inhibitors with high drug loading for superimposed DNA damage-augmented tumor regression. By introducing iron ions (Ⅲ) and another TOP-2A inhibitor quercetin (QU) onto the building blocks, Fe³⁺-mediated QU-MTX co-nanoassemblies are fabricated (QU-MTX-Fe) via intermolecular coordination interactions. The PEGylated co-nanoassemblies (P-QU-MTX-Fe) exhibit distinct advantages over QU/MTX solution (Sol) alone or MTX-QU mixture Sol in terms of therapeutic efficacy and systemic toxicity. Meanwhile, P-QU-MTX-Fe could efficiently suppress primary and distal breast tumor relapse by activating the CD 8⁺-mediated antitumor immune response. Overall, such iron-coordinated nanomedicines provide insights into the rational design of drug-likeness compounds with undesirable therapeutic performance for cancer therapy. STATEMENT OF SIGNIFICANCE: Aimed at the key target TOP-2A in the malignant breast tumor, the metal coordination-mediated supramolecular co-assemble strategy of one-target dual inhibitors was firstly proposed for superimposed DNA damage for cancer therapy. Multiple interactions involving π-π stacking interactions, hydrogen bonds and coordination forces maintained the stability of co-nanoassemblies. Meanwhile, this co-nanoassemblies not only had potentials to increase therapeutic efficacy and decrease systemic toxicity, but also activated the CD 8⁺-mediated antitumor immune response against distal breast tumor relapse. Such a facile and safe nanoplatform is expected to provide an important prospective for promoting the clinical transformation of drug-likeness compounds in the suppression of difficult-to-treat breast tumor.

Drug Self-delivery Nanorods Enhance Photodynamic Therapy of Triple-Negative Breast Cancer by inhibiting Oxidative Phosphorylation

Photodynamic therapy (PDT) shows very high potential for the clinical treatment of triple-negative breast cancer. However, the efficacy of PDT is significantly weakened by tumor hypoxia, the relatively high intracellular glutathione levels and the active proliferation of cancer cells. To address these issues, we developed a novel drug self-delivery nanorod (defined as AINRs) through the hydrophobic interaction among the mitochondrial complex III inhibitor (atovaquone, ATO), the photosensitizer (indocyanine green, ICG) and the dispersion stabilizer (distearoyl phosphoethanolamine-polyethylene glycol 2000, DSPE-PEG 2000). The AINRs showed a rod-like morphology with a mean diameter of 120.6 ± 5.4 nm, a zeta potential of -26.35 ± 1.63 mV and a significantly high drug loading rate of 93.48%. The results of in vitro cell experiments involving triple-negative breast cancer cell lines (4T1 cells and MDA-MB-231 cells) indicated that the AINRs could effectively block the oxidative phosphorylation of cancer cells through the inhibition of mitochondrial complex III, which results in the reduction of endogenous oxygen consumption and the decrease of the intracellular ATP level. The reduction of ATP content further inhibited the glutathione synthesis and arrested the cell cycle at the S-phase, which results in enhanced in vitro PDT efficacy of ICG. The results of in vivo antitumor activity in 4T1-bearing mice showed that the tumor growth inhibition rate of the AINRs with near-infrared laser irradiation (NIR) was 90%, whereas the tumor growth inhibition rates of the AINRs without NIR, ICG with NIR and doxorubicin (3 mg/kg) were only 31.68%, 61.15% and 24.59%, respectively. In addition, the results of safety studies, including body weights, biochemical indicators and H&E staining images of the main organs demonstrated the security of the AINRs. In summary, this study showed that the oxidative phosphorylation inhibition of triple-negative breast cancer was a safe and effective method to enhance its PDT efficacy.

Self-delivery nanomedicine for vascular disruption-supplemented chemo-photodynamic tumor therapy

Tumor vascular blockade is a promising strategy for adjuvant cancer treatment. In this work, a self-delivery nanomedicine is developed based on a vascular disruptor and photosensitizer for tumor synergistic therapy. Specifically, this nanomedicine (designated as CeCA) is comprised of combretastatin A4 (CA4) and chlorine e6 (Ce6) by self-assembly technique. Among which, CA4 could not only induce tubulin inhibition for chemotherapy but also disrupt the vasculature to cause tumor hemorrhage. Moreover, Ce6 is able to generate lots of singlet oxygen (¹O₂) for synergistic photodynamic therapy (PDT) under light irradiation. It is interesting that the carrier-free CeCA possessed a favorable stability and an improved cellular uptake behavior. After intravenous administration, CeCA prefers to accumulate at tumor site for vascular disruption-supplemented chemo-photodynamic therapy. Notably, CeCA is prepared without additional carriers, which avoids the system toxicity raised by excipients. Consequently, CeCA greatly inhibits the tumor growth and leads to a low side effect in vivo. It might open a window in the development of self-supplementary nanomedicine for synergistic tumor treatment.

Near-Infrared II Nanoadjuvant-Mediated Chemodynamic, Photodynamic, and Photothermal Therapy Combines Immunogenic Cell Death with PD-L1 Blockade to Enhance Antitumor Immunity

The efficacy of immune checkpoint inhibition in inducing death of cancer cells is affected by the immunosuppressive "cold" tumor microenvironment, which results in a poor response by the patient's antitumor immune system. However, the immunomodulatory effects of immunogenic cell death in response to irritation by heat energy and reactive oxygen species (ROS) can switch the tumor microenvironment from "cold" to "hot." This study has developed a nanoadjuvant for immune therapy using iron tungsten oxide (FeWOx)-based nanosheets with surface PEGylation (FeWOx-PEG). This FeWOx-PEG nanoadjuvant serves as a chemodynamic reagent via the Fenton reaction and acts as a photosensitizer for photodynamic and photothermal therapy under near-infrared II laser irradiation; however, it could also be used to augment tumor-infiltrating T-cells and provoke a systemic antitumor immune response by combining the immunogenic cell death triggered by ROS and photothermal therapy with the immune checkpoint blockade. This research demonstrates that application of the FeWOx-PEG nanoadjuvant under the guidance of magnetic resonance/computed tomography/photoacoustic imaging can eliminate the primary tumor and suppress the growth of distant tumors.

Self-Delivery Nanomedicine for Glutamine-Starvation Enhanced Photodynamic Tumor Therapy

Glutamine metabolism of tumor cells plays a crucial role in maintaining cell homeostasis and reducing oxidative damage. Herein, a valid strategy of inhibiting glutamine metabolism is proposed to amplify the oxidative damage of photodynamic therapy (PDT) to tumor cells. Specifically, the authors develop a drug co-delivery system (designated as CeV) based on chlorine e6 (Ce6) and V9302 via the self-assembly technology. In spite of the strong hydrophobicity of therapeutic agents, the assembled CeV holds a favorable dispersibility in water and an improved cellular uptake capability. Under light irradiation, the internalized CeV is capable of generating abundant reactive oxygen species (ROS) for PDT. More importantly, CeV can reduce the uptake of glutamine through V9302-mediated alanine-serine-cysteine transporter of type-2 (ASCT2) inhibition, leading to a reduced glutathione (GSH) production and an amplified oxidative stress. As a result, CeV has a robust PDT efficacy on tumor inhibition by the blockade of glutamine transport. Notably, CeV exhibits a superiority on tumor suppression over the single treatment as well as the combined administration of Ce6 and V9302, which indicates the advantage of CeV for synergistic treatment. It may serve as a novel nanoplatform for developing a drug co-delivery system to improve PDT efficiency by inhibiting cell metabolism.

Self-Delivery Ternary Bioregulators for Photodynamic Amplified Immunotherapy by Tumor Microenvironment Reprogramming

Abnormal metabolism of cancer cells results in complex tumor microenvironments (TME), which play a dominant role in tumor metastasis. Herein, self-delivery ternary bioregulators (designated as TerBio) are constructed for photodynamic amplified immunotherapy against colorectal cancer by TME reprogramming. Specifically, carrier-free TerBio are prepared by the self-assembly of chlorine e6, SB505124 (SB), and lonidamine (Lon), which exhibit improved tumor accumulation, tumor penetration, and cellular uptake behaviors. Interestingly, TerBio-mediated photodynamic therapy (PDT) could not only inhibit the primary tumor growth but also induce immunogenic cell death of tumors to activate the cascade immune response. Furthermore, TerBio are capable of TME reprograming by SB-triggered transforming growth factor (TGF)-β blockage and Lon-induced lactic acid efflux inhibition. As a consequence, TerBio significantly suppresses distant and metastatic tumor growth by PDT-amplified immunotherapy. This study might advance the development of self-delivery nanomedicine against malignant tumor growth and metastasis.

Binary regulation of the tumor microenvironment by a pH-responsive reversible shielding nanoplatform for improved tumor chemo-immunotherapy

The limited infiltration of specific T cells in an immunosuppressive microenvironment is a major challenge for cancer immunotherapy. Reversing tumor microenvironment and inducing an antitumor immune response are crucial for cancer therapy. Here, phenylboronic acid (PBA) derivative-stabilized ultrasmall platinum nanoparticles (PBA-Pt) and dextran-coated BLZ-945 nanoparticles (DNPs) were co-assembled through a pH-responsive borate ester bond to construct a versatile reversible shielding multifunctional nanoplatform (Pt@DNPs) for the first time. Pt@DNPs dissociated into two individual components, namely PBA-Pt and DNPs, in the tumor acid microenvironment. Both in vitro and in vivo studies revealed that Pt@DNPs induced immunogenic cell death (ICD) (through multimechanisms involving Pt^Ⅱ release and a multienzyme catalytic process by PBA-Pt) and relieved immunosuppressive microenvironment (depletion of tumor-associated macrophages by BLZ-945), which led to tumor-associated antigen release, maturation of dendritic cells, and infiltration of cytotoxic T cells for efficient antitumor immune response against both primary tumor and pulmonary metastatic tumor nodules. Therefore, Pt@DNPs is a promising option for cancer chemo-immunotherapy. STATEMENT OF SIGNIFICANCE: A versatile reversible shielding multifunctional nanoplatform (Pt@DNPs) was engineered for the first time for combinational cancer chemo-immunotherapy. Multimechanisms involving induction of immunogenic cell death by PBA-Pt and sufficient TAM depletion by DNPs could efficiently relieve tumor immunosuppressive microenvironment and activate the antitumor immune response. The synergistic effect not only increased the infiltration of specific T cells in primary tumor, but it also induced a strong immune response against pulmonary metastatic nodules. Collectively, this nanoplatform may represent a promising strategy for combinational chemo-immunotherapy for cancers.

Multifunctional inorganic nanomaterials for cancer photoimmunotherapy

Phototherapy and immunotherapy in combination is regarded as the ideal therapeutic modality to treat both primary and metastatic tumors. Immunotherapy uses different immunological approaches to stimulate the immune system to identify tumor cells for targeted elimination. Phototherapy destroys the primary tumors by light irradiation, which induces a series of immune responses through triggering immunogenic cancer cell death. Therefore, when integrating immunotherapy with phototherapy, a novel anti-cancer strategy called photoimmunotherapy (PIT) is emerging. This synergistic treatment modality can not only enhance the effectiveness of both therapies but also overcome their inherent limitations, opening a new era for the current anti-cancer therapy. Recently, the advancement of nanomaterials affords a platform for PIT. From all these nanomaterials, inorganic nanomaterials stand out as ideal mediators in PIT due to their unique physiochemical properties. Inorganic nanomaterials can not only serve as carriers to transport immunomodulatory agents in immunotherapy owing to their excellent drug-loading capacity but also function as photothermal agents or photosensitizers in phototherapy because of their great optical characteristics. In this review, the recent advances of multifunctional inorganic nanomaterial-mediated drug delivery and their contributions to cancer PIT will be highlighted.

Recent advances in nanomedicines for photodynamic therapy (PDT)-driven cancer immunotherapy

Cancer immunotherapy has made tremendous clinical progress in advanced-stage malignancies. However, patients with various tumors exhibit a low response rate to immunotherapy because of a powerful immunosuppressive tumor microenvironment (TME) and insufficient immunogenicity of tumors. Photodynamic therapy (PDT) can not only directly kill tumor cells, but also elicit immunogenic cell death (ICD), providing antitumor immunity. Unfortunately, limitations from the inherent nature and complex TME significantly reduce the efficiency of PDT. Recently, smart nanomedicine-based strategies could subtly modulate the pharmacokinetics of therapeutic compounds and the TME to optimize both PDT and immunotherapy, resulting in an improved antitumor effect. Here, the emerging nanomedicines for PDT-driven cancer immunotherapy are reviewed, including hypoxia-reversed nanomedicines, nanosized metal-organic frameworks, and subcellular targeted nanoparticles (NPs). Moreover, we highlight the synergistic nanotherapeutics used to amplify immune responses combined with immunotherapy against tumors. Lastly, the challenges and future expectations in the field of PDT-driven cancer immunotherapy are discussed.

Supramolecular biomaterials for enhanced cancer immunotherapy

Cancer immunotherapy has achieved promising clinical results. However, many limitations associated with current cancer immunotherapy still exist, including low response rates and severe adverse effects in patients. Engineering biomaterials for...

A tailored and red-emissive type I photosensitizer to potentiate photodynamic immunotherapy

Photodynamic immunotherapy (PDIT) emerges and shows great potentials in eradicating malignant tumors for the advantages on simultaneously damaging primary tumors, inhibiting tumors metastasis and recurrence. However, hypoxic microenvironment of tumor...

Carrier free photodynamic oxidizer for enhanced tumor therapy by redox homeostasis disruption

Abnormal tumor microenvironments play important roles in cancer progression. In general, tumor cells are capable of upregulating glutathione (GSH) levels to keep aberrant redox homeostasis and cause a resistance to...

Current Strategies for Tumor Photodynamic Therapy Combined With Immunotherapy

Photodynamic therapy (PDT) is a low invasive antitumor therapy with fewer side effects. On the other hand, immunotherapy also has significant clinical applications in the treatment of cancer. Both therapies, on their own, have some limitations and are incapable of meeting the demands of the current cancer treatment. The efficacy of PDT and immunotherapy against tumor metastasis and tumor recurrence may be improved by combination strategies. In this review, we discussed the possibility that PDT could be used to activate immune responses by inducing immunogenic cell death or generating cancer vaccines. Furthermore, we explored the latest advances in PDT antitumor therapy in combination with some immunotherapy such as immune adjuvants, inhibitors of immune suppression, and immune checkpoint blockade.

Immunogenic cell death inducers for enhanced cancer immunotherapy

Inducing the immunogenic cell death (ICD) of cancer cells is an important method to improve the immunogenicity of tumor cells for enhanced cancer immunotherapy. Therefore, we discuss the ICD process and then highlight various ICD inducers and strategies for triggering the ICD of cancer cells. We hope that this Feature Article will inspire readers to develop more effective ICD inducers.

Self-Remedied Nanomedicine for Surmounting the Achilles' Heel of Photodynamic Tumor Therapy

Oxygen-dependent photodynamic therapy (PDT) could exacerbate tumor hypoxia to induce the upregulation of hypoxia-inducible factor-1α (HIF-1α), which would promote tumor growth and metastasis. In this paper, a self-remedied nanomedicine is developed based on a photosensitizer and a HIF-1α inhibitor to surmount the Achilles' heel of PDT for enhanced antitumor efficacy. Specifically, the nanomedicine (designated as CYC-1) is prepared by the self-assembly of chlorine e6 (Ce6) and 3-(5'-hydroxy-methyl-2'-furyl)-1-benzylindazole (YC-1) through π-π stacking and hydrophobic interactions. Of special note, carrier-free CYC-1 holds an extremely high drug loading rate and avoids excipient-triggered adverse reactions. Intravenously administered CYC-1 prefers to accumulate in the tumor tissue for effective cellular uptake. More importantly, it is verified that CYC-1 is capable of inhibiting the HIF-1α activity, thereby improving its PDT efficacy on tumor suppression. Besides, CYC-1 has the overwhelming superiority in restraining tumor proliferation over the combined administration of Ce6 and YC-1, which highlights the advantage of this self-remedied strategy in drug delivery and tumor therapy. This study sheds light on the development of self-delivery nanomedicine for efficient PDT against malignancies.

Self-adjuvanting photosensitizer nanoparticles for combination photodynamic immunotherapy

Combination cancer immunotherapy that synergizes the advantages of multiple therapeutic agents has shown great potential in tumor treatment. Herein, we report the one-step assembly of therapeutic nanoparticles (NPs) to co-deliver photosensitizers and adjuvants for combination photodynamic therapy (PDT) and immunotherapy. The NPs are obtained via self-assembly of chlorin e6 (Ce6) and imidazoquinoline-based TLR7 agonists (IMDQ), which results in a high loading efficacy of 72.2% and 27.8% for Ce6 and IMDQ, respectively. Upon laser irradiation, the resulting NPs could not only effectively induce photodynamic immunogenic cancer cell death, but also elicit robust antitumor immunity, leading to significant inhibition of both primary and distant tumors in a bilateral tumor model. This study demonstrates the potential of self-assembled NPs in co-delivering multiple therapeutics for potential immunotherapy to enhance the antitumor efficacy.

Cancer immunogenic cell death via photo-pyroptosis with light-sensitive Indoleamine 2,3-dioxygenase inhibitor conjugate

Immune checkpoint blockade (ICB) therapy currently considered as to be effective way to cure cancer in clinic. However, the insufficient tumor immunogenicity and the immunosuppressive tumor microenvironment always result in diminished efficacy of immunotherapy. Herein, we report the synthesis of an organic photo-immune activator NBS-1MT, the combination of photosensitizer and Indoleamine 2,3-dioxygenase (IDO) inhibitor effectively stimulates lysosomes oxidative stress the releases inflammatory cytokines. This process triggers pyroptosis for the considerable immunogenic cell death (ICD) while reversing suppressive tumor microenvironment. The photo-immune drug shows outstanding potential to activate caspase-1and then remove gasdermin-D (GSDMD), which could stimulate pyroptosis and also inhibit the tumor growth successfully in both primary and distant tumor. Furthermore, pyroptosis activated by photodynamic therapy (PDT) promotes the immune related factors release, and enhance the intratumoral infiltration of cytotoxic T lymphocytes (CTLs) with the induction of ICD of tumor cells and the cascaded synergize with IDO inhibitor, so the general antitumor immune response could be strengthened effectively. Our research confirms that the use of NBS-1MT is a promising strategy to boost the immune response and eventually to inhibit tumor growth.

Biomimetic phototherapy in cancer treatment: from synthesis to application

Phototherapy, with minimally invasive and cosmetic effect, has received considerable attention and been widely studied in cancer treatment, especially in biomaterials field. However, most nanomaterials applied for the delivery of phototherapy agents are usually recognized by the immune system or cleared by liver and kidney, thus hindering their clinical applications. To overcome these limitations, bionic technology stands out by virtue of its low antigenicity and targeting properties, including membrane bionics and bionic enzymes. In this review, we will summarize the up-to-date progress in the development of biomimetic camouflage-based nanomaterials for phototherapy, from synthesis to application, and their future in cancer treatment.

Carrier Free Photodynamic Synergists for Oxidative Damage Amplified Tumor Therapy

Tumor cells adapt to excessive oxidative stress by actuating reactive oxygen species (ROS)-defensing system, leading to a resistance to oxidation therapy. In this work, self-delivery photodynamic synergists (designated as PhotoSyn) are developed for oxidative damage amplified tumor therapy. Specifically, PhotoSyn are fabricated by the self-assembly of chlorine e6 (Ce6) and TH588 through π-π stacking and hydrophobic interactions. Without additional carriers, nanoscale PhotoSyn possess an extremely high drug loading rate (up to 100%) and they are found to be fairly stable in aqueous phase with a uniform size distribution. Intravenously injected PhotoSyn prefer to accumulate at tumor sites for effective cellular uptake. More importantly, TH588-mediated MTH1 inhibition could destroy the ROS-defensing system of tumor cells by preventing the elimination of 8-oxo-2'-deoxyguanosine triphosphate (8-oxo-dG), thereby exacerbating the oxidative DNA damage induced by the photodynamic therapy (PDT) of Ce6 under light irradiation. As a consequence, PhotoSyn exhibit enhanced photo toxicity and a significant antitumor effect. This amplified oxidative damage strategy improves the PDT efficiency with a reduced side effect by increasing the lethality of ROS without generating superabundant ROS, which would provide a new insight for developing self-delivery nanoplatforms in photodynamic tumor therapy in clinic.

Versatile Nanodrugs Containing Glutathione and Heme Oxygenase 1 Inhibitors Enable Suppression of Antioxidant Defense System in a Two-Pronged Manner for Enhanced Photodynamic Therapy

The antioxidant defense system in malignant cells, which involves antioxidant enzymes and antioxidant molecules, is an innate barrier to photodynamic therapy (PDT). Because of the complexity of the endogenous antioxidant mechanisms of these cells, simply inhibiting individual antioxidant pathways has a limited effect on improving the lethality of ROS. To enhance the efficacy of PDT for tumor treatment, a versatile nanoparticle (NP)-based drug is developed, which the authors call PZB NP, containing the glutathione inhibitor l-buthionine sulfoximine (BSO) and the heme oxygenase 1 (HO-1) inhibitor protoporphyrin zinc(II) (ZnPP) to suppress the innate antioxidant defense system of cancer cells in a two-pronged manner. BSO reduces intracellular glutathione levels to minimize ROS elimination and protein protection during PDT, and ZnPP inhibits the ROS-stimulated upregulation of the antioxidant HO-1, thus preventing ROS removal by cells after PDT. Thus, BSO and ZnPP synergistically suppress the antioxidant defense systems of cancer cells both during and after protoporphyrin-IX-mediated PDT in a two-pronged manner, resulting in tumor cell death through excess oxidative pressure. The results demonstrate that the construction of nanodrugs having dual antioxidation defense suppression properties is a promising route for the development of highly efficient ROS-based therapies.

Regulating immune memory and reversing tumor thermotolerance through a step-by-step starving-photothermal therapy

Background

Photothermal therapy (PTT) is a highly effective treatment for solid tumors and can induce long-term immune memory worked like an in situ vaccine. Nevertheless, PTT inevitably encounters photothermal resistance of tumor cells, which hinders therapeutic effect or even leads to tumor recurrence. Naïve CD8+ T cells are mainly metabolized by oxidative phosphorylation (OXPHOS), followed by aerobic glycolysis after activation. And the differentiate of effector CD8+ T cell (CD8+ T_eff) into central memory CD8+ T cell (CD8+ TCM) depends on fatty acid oxidation (FAO) to meet their metabolic requirements, which is regulated by adenosine monophosphate activated protein kinase (AMPK). In addition, the tumor microenvironment (TME) is severely immunosuppressive, conferring additional protection against the host immune response mediated by PTT.

Methods

Metformin (Met) down-regulates NADH/NADPH, promotes the FAO of CD8+ T cells by activating AMPK, increases the number of CD8+ TCM, which boosts the long-term immune memory of tumor-bearing mice treated with PTT. Here, a kind of PLGA microspheres co-encapsulated hollow gold nanoshells and Met (HAuNS-Met@MS) was constructed to inhibit the tumor progress. 2-Deoxyglucose (2DG), a glycolysis inhibitor for cancer starving therapy, can cause energy loss of tumor cells, reduce the heat stress response of tumor cell, and reverse its photothermal resistance. Moreover, 2DG prevents N-glycosylation of proteins that cause endoplasmic reticulum stress (ERS), further synergistically enhance PTT-induced tumor immunogenic cell death (ICD), and improve the effect of immunotherapy. So 2DG was also introduced and optimized here to solve the metabolic competition among tumor cells and immune cells in the TME.

Results

We utilized mild PTT effect of HAuNS to propose an in situ vaccine strategy based on the tumor itself. By targeting the metabolism of TME with different administration strategy of 2DG and perdurable action of Met, the thermotolerance of tumor cells was reversed, more CD8+ TCMs were produced and more effective anti-tumor was presented in this study.

Conclusion

The Step-by-Step starving-photothermal therapy could not only reverse the tumor thermotolerance, but also enhance the ICD and produce more CD8+ TCM during the treatment.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-01011-2.

NIR-triggerable ROS-responsive cluster-bomb-like nanoplatform for enhanced tumor penetration, phototherapy efficiency and antitumor immunity

The restricted tumor penetration has been regarded as the Achilles' Heels of most nanomedicines, largely limiting their efficacy. To address this challenge, a cluster-bomb-like nanoplatform named CPIM is prepared, which for the first time combines size-transforming and transcytosis strategies, thus enhancing both passive and active transport. For passive diffusion, the "cluster-bomb" CPIM (135 nm) releases drug-loaded "bomblets" (IR780/1-methyl-tryptophan (1 MT) loaded PAMAM, <10 nm) in response to the high reactive-oxygen-species (ROS) concentration in tumor microenvironment (TME), which promotes intratumoral diffusion. Besides, IR780 generates ROS upon NIR irradiation and intensifies this responsiveness; therefore, there exists a NIR-triggered self-destructive behavior, rendering CPIM spatiotemporal controllability. For active transport, the nanoplatform is proven to be delivered via transcytosis with/without NIR irradiation. Regarding the anti-cancer performance, CPIM strengthens the photodynamic therapy (PDT)/photothermal therapy (PTT) activity of IR780 and IDO pathway inhibition effect of 1 MT, thus exhibiting a strongest inhibitory effect on primary tumor. CPIM also optimally induces immunogenic cell death, reverses the "cold" TME to a "hot" one and evokes systemic immune response, thus exerting an abscopal and anti-metastasis effects. In conclusion, this work provides a facile, simple yet effective strategy to enhance the tumor penetration, tumor-killing effect and antitumor immunity of nanomedicines.

Self-delivery oxidative stress amplifier for chemotherapy sensitized immunotherapy

Amplifying oxidative stress to break intracellular redox homeostasis could accelerate tumor cell death. In this work, a self-delivery oxidative stress amplifier is developed for chemotherapy sensitized immunotherapy. By virtue of the π-π stacking and coordination effect, copper ions (Cu2+), doxorubicin (DOX) and NLG919 are able to self-assembly into the nanosized oxidative stress amplifier (designated as Cu-DON) with a favorable stability and a biocompatibility. Intravenously administrated Cu-DON could effectively accumulate and penetrate into tumor tissues for cellular uptake. Subsequently, the GSH-responsive DOX release will initiate the immunogenic chemotherapy (IC) for primary tumor inhibition. Moreover, Cu2+-mediated GSH consumption and DOX-triggered oxidative stress could cause the intracellular redox imbalance, contributing to immunogenic cell death (ICD) response. Further, the concomitant release of NLG919 would inhibit indoleamine 2,3-dioxygenase 1 (IDO-1) to reverse immunosuppressive tumor microenvironment (ITM) for enhanced immunotherapy. Consequently, this self-delivery oxidative stress amplifier greatly restrains the growth of primary, distant as well as rechallenged tumors by chemotherapy sensitized immunotherapy, which would shed light on the development of combination therapy to block tumor growth and metastasis in clinic.

A NO/ROS/RNS cascaded-releasing nano-platform for gas/PDT/PTT/immunotherapy of tumors

Nitric oxide (NO) gas treatment offers a promising strategy for tumor therapy; however, its practical application is still limited due to its poor efficacy and biotoxicity which were caused by gas leakage during blood delivery. Herein, a nano-platform (CMH-OBN) composed of chlorin e6-melanin-hyaluronic acid nanoparticles (Ce6-MNP-HA, CMH) and oxidized bletilla striata polysaccharide microcapsules (Oxi-BSP) carrying NO donors was prepared for responsive and cascaded release of NO, reactive oxygen species (ROS) and its secondary metabolite reactive nitrogen species (RNS) in tumor sites. Melanin not only endowed CMH with good photothermal properties, but also helped Ce6 to produce a large number of ROS under near-infrared (NIR) irradiation. OBN microcapsules, which were sensitive to ROS, can release NO donors under the stimulation of ROS released by CMH nanoparticles under NIR irradiation and can further release NO in the tumor microenvironment (TME) with high expression of glutathione (GSH). NO could further up-regulate soluble guanylate cyclase-cyclic guanosine monophosphate (sGC-cGMP) signal pathways to relieve hypoxia, thus further enhancing the photodynamic therapy (PDT). Moreover, the cascaded release of ROS and NO could produce RNS with higher lethality, which could sequentially initiate the cellular apoptotic procedure and promote immunotherapy by activating T cells at the tumor sites. More interestingly, the CMH-OBN nano-platform could supply magnetic resonance imaging (MRI) and infrared photothermal imaging guidance for tumor therapy. In conclusion, the development of a CMH-OBN nano-platform provides a satisfactory demonstration by combining NO therapy with photothermal therapy (PTT), PDT and immunotherapy for the treatment of cancer.

Nanomaterials-Based Photodynamic Therapy with Combined Treatment Improves Antitumor Efficacy Through Boosting Immunogenic Cell Death

Benefiting from the rapid development of nanotechnology, photodynamic therapy (PDT) is arising as a novel non-invasive clinical treatment for specific cancers, which exerts direct efficacy in destroying primary tumors by generating excessive cytotoxic reactive oxygen species (ROS). Notably, PDT-induced cell death is related to T cell-mediated antitumor immune responses through induction of immunogenic cell death (ICD). However, ICD elicited via PDT is not strong enough and is limited by immunosuppressive tumor microenvironment (ITM). Therefore, it is necessary to improve PDT efficacy through enhancing ICD with the combination of synergistic tumor therapies. Herein, the recent progress of nanomaterials-based PDT combined with chemotherapy, photothermal therapy, radiotherapy, and immunotherapy, employing ICD-boosted treatments is reviewed. An outlook about the future application in clinics of nanomaterials-based PDT strategies is also mentioned.

Metal-coordinated nanomedicine for combined tumor therapy by inducing paraptosis and apoptosis

Apoptosis resistance of tumor cells often results in chemoresistance and treatment failure in clinic. In this work, a Cu²⁺-coordinated morusin/doxorubicin biological organizer (designated as COMBO) is designed to combat cellular resistance to apoptosis for combined tumor therapy. By virtue of the coordination and π-π stacking effects, the self-assembled COMBO possesses nanometer particle size, narrow and homogenous graininess distribution as well as a good dispersion stability. Moreover, COMBO could be disassembled by glutathione (GSH) with an effective drug release and fluorescence recovery. Morusin-mediated paraptosis could induce extensive vacuolization through the dilation of endoplasmic reticulum (ER) and mitochondria, leading to non-apoptotic programmed cell death (PCD) regardless of the cellular resistance to apoptosis. Furthermore, the released doxorubicin prefers to locate in cell nucleus to cause cell apoptosis for combined chemotherapy. By the joint action of paraptosis and apoptosis, COMBO exhibits a great superiority over monotherapy in tumor inhibition with a low system toxicity. This study may open a window in the development of self-delivery nanomedicine for overcoming apoptosis resistance in tumor therapy.

Mitochondria Targeted O2 Economizer to Alleviate Tumor Hypoxia for Enhanced Photodynamic Therapy

Photodynamic therapy (PDT) often suffers from the exacerbated tumor hypoxia and the heterogeneous distribution of photosensitizers, leading to an inefficient ROS productivity and availability. In this work, a mitochondria targeted O₂ economizer (designated as Mito-OxE) is developed to improve PDT efficiency by alleviating tumor hypoxia and enhancing the subcellular localization of photosensitizers. Specifically, the photosensitizer of protoporphyrin IX (PpIX) is modified with the hydrophilic polyethylene glycol and the lipophilic cation of triphenylphosphine (TPP) to fabricate the biocompatible mitochondria targeted photosensitizers (designated as Mito-PSs). And Mito-OxE is prepared by using Mito-PSs to load the mitochondrial oxidative phosphorylation inhibitors of atovaquone (ATO). Benefiting from the targeting capability of TPP, Mito-OxE can selectively accumulate in mitochondria after cellular uptake. Subsequently, the mitochondrial respiration would be suppressed to with the participation of ATO, resulting in a local hypoxia mitigation for enhanced PDT. Compared with Mito-PSs, Mito-OxE maximizes the therapeutic effect against hypoxic tumors under light irradiation. This design of mitochondria targeted O₂ economizer would advance the development of targeted drug delivery system for effective PDT regardless of hypoxic microenvironment.

Plasma membrane targeted photodynamic O2 economizer for hypoxic tumor therapy

The development of photodynamic therapy (PDT) is severely limited by short half-life of singlet oxygen (¹O₂) and the hypoxic microenvironment. In this work, a plasma membrane targeted photodynamic O₂ economizer (designated as P-POE) is developed to improve the subcellular delivery of photosensitizers and alleviate the tumor hypoxia for enhanced PDT effect. After self-assembly into nanomicelles, P-POE has a relatively high stability and a favorable photochemical performance, which are conducive to boosting the ¹O₂ production. Besides, the plasma membrane anchoring of P-POE contributes to enhancing the preferential retention and cellular accumulation of photosensitizers on tumor tissues and cells. More importantly, P-POE-induced mitochondrial respiratory depression is demonstrated to reduce the O₂ consumption of tumor cells to relieve the hypoxia. Consequently, P-POE still exhibits a robust PDT effect against hypoxic tumors, which greatly inhibits the proliferation of breast cancer with low adverse reactions. This innovative combination of subcellular targeting and hypoxic alleviation would advance the development of individualized drug delivery systems for photodynamic therapy against hypoxic tumors.

MOFs-Derived Fe-N Codoped Carbon Nanoparticles as O2-Evolving Reactor and ROS Generator for CDT/PDT/PTT Synergistic Treatment of Tumors

Metal-organic frameworks (MOFs) derivatives had been widely explored in electronic and environmental fields, but rarely evaluated in the biomedical applications. Herein, Fe-N codoped carbon (FeNC) nanoparticles were synthesized and characterized via facile pyrolysis of precursor ZIF-8 (Fe/Zn) nanoparticles, and their potential applications in tumor therapy were assessed in this investigation both in vitro and in vivo. After PAA (sodium polyacrylate) modification, the FeNC@PAA nanoparticles were able to initiate a Fe-based Fenton-like reaction to generate ·OH and O₂ for chemodynamic therapy (CDT) and O₂ evolution. Meanwhile, the porphyrin-like metal center in the FeNC@PAA nanoparticles could be used as a photosensitizer for photodynamic therapy (PDT) of tumors, which could be enhanced by O₂ generated in CDT. Furthermore, the FeNC@PAA nanoparticles were also found to be effective in photothermal therapy (PTT) with a photothermal conversion efficiency of 29.15%, owing to a high absorbance in the near-infrared region (NIR). In conclusion, the synthesized FeNC@PAA nanoparticles exhibited promising applications in O₂ evolution and CDT/PDT/PTT synergistic treatment of tumors.