Phospholipid membrane-decorated deep-penetrated nanocatalase relieve tumor hypoxia to enhance chemo-photodynamic therapy

Size-Switchable Ru Nanoaggregates for Enhancing Phototherapy: Hyaluronidase-Triggered Disassembly to Alleviate Deep Tumor Hypoxia

Hypoxia is a critical factor for restricting photodynamic therapy (PDT) of tumor, and it becomes increasingly severe with increasing tissue depth. Thus, the relief of deep tumor hypoxia is extremely important to improve the PDT efficacy. Herein, tumor microenvironment (TME)-responsive size-switchable hyaluronic acid-hybridized Ru nanoaggregates (HA@Ru NAs) were developed via screening reaction temperature to alleviate deep tumor hypoxia for improving the tumor-specific PDT by the artful integration multiple bioactivated chemical reactions in situ and receptor-mediated targeting (RMT). In this nanosystem, Ru NPs not only enabled HA@Ru NAs to have near infrared (NIR)-mediated photothermal/photodynamic functions, but also could catalyze endogenous H2O2 to produce O2 in situ. More importantly, hyaluronidase (HAase) overexpressed in the TME could trigger disassembly of HA@Ru NAs via the hydrolysis of HA, offering the smart size switch capability from 60 to 15 nm for enhancing tumor penetration. Moreover, the RMT characteristics of HA ensured that HA@Ru NAs could specially enter CD44-overexpressed tumor cells, enhancing tumor-specific precision of phototherapy. Taken together these distinguishing characteristics, smart HA@Ru NAs successfully realized the relief of deep tumor hypoxia to improve the tumor-specific PDT.

Current advances in modulating tumor hypoxia for enhanced therapeutic efficacy

Hypoxia is a common feature of most solid tumors, which promotes the proliferation, invasion, metastasis, and therapeutic resistance of tumors. Researchers have been developing advanced strategies and nanoplatforms to modulate tumor hypoxia to enhance therapeutic effects. A timely review of this rapidly developing research topic is therefore highly desirable. For this purpose, this review first introduces the impact of hypoxia on tumor development and therapeutic resistance in detail. Current developments in the construction of various nanoplatforms to enhance tumor treatment in response to hypoxia are also systematically summarized, including hypoxia-overcoming, hypoxia-exploiting, and hypoxia-disregarding strategies. We provide a detailed discussion of the rationale and research progress of these strategies. Through a review of current trends, it is hoped that this comprehensive overview can provide new prospects for clinical application in tumor treatment. STATEMENT OF SIGNIFICANCE: As a common feature of most solid tumors, hypoxia significantly promotes tumor progression. Advanced nanoplatforms have been developed to modulate tumor hypoxia to enhanced therapeutic effects. In this review, we first introduce the impact of hypoxia on tumor progression. Current developments in the construction of various nanoplatforms to enhance tumor treatment in response to hypoxia are systematically summarized, including hypoxia-overcoming, hypoxia-exploiting, and hypoxia-disregarding strategies. We discuss the rationale and research progress of the above strategies in detail, and finally introduce future challenges for treatment of hypoxic tumors. By reviewing the current trends, this comprehensive overview can provide new prospects for clinical translatable tumor therapy.

Nanoparticles that target the mitochondria of tumor cells to restore oxygen supply for photodynamic therapy: Design and preclinical validation against breast cancer

Photodynamic therapy, in which photosensitizers locally generate cytotoxic reactive oxygen species, can treat tumor tissue with minimal effects on surrounding normal tissue, but it can be ineffective because of the anoxic tumor microenvironment. Here we developed a strategy to inactivate the mitochondria of tumor cells in order to ensure adequate local oxygen concentrations for photodynamic therapy. We conjugated the photosensitizer 5-aminolevulinic acid to the lipophilic cation triphenylphosphine, which targets mitochondria. Then we packaged the conjugate into nanoparticles that were based on biocompatible bovine serum albumin and coated with folic acid in order to target the abundant folate receptors on the tumor surface. In studies in cell culture and BALB/c mice bearing MCF-7 xenografts, we found that the nanoparticles helped solubilize the cation-photosensitizer conjugate, prolong its circulation, and enhance its photodynamic antitumor effects. We confirmed the ability of the nanoparticles to target tumor cells and their mitochondria using confocal laser microscopy and in vivo assays of pharmacokinetics, pharmacodynamics, and tissue distribution. Our results not only identify a novel nanoparticle system for treating cancer, but they demonstrate the feasibility of enhancing photodynamic therapy by reducing oxygen consumption within tumors.

Stimuli responsive nanosonosensitizers for sonodynamic therapy

Sonodynamic therapy (SDT) has gained significant attention in the treatment of deep tumors and multidrug-resistant (MDR) bacterial infections due to its high tissue penetration depth, high spatiotemporal selectivity, and noninvasive therapeutic method. SDT combines low-intensity ultrasound (US) and sonosensitizers to produce lethal reactive oxygen species (ROS) and external damage, which is the main mechanism behind this therapy. However, traditional organic small-molecule sonosensitizers display poor water solubility, strong phototoxicity, and insufficient targeting ability. Inorganic sonosensitizers, on the other hand, have low ROS yield and poor biocompatibility. These drawbacks have hindered SDT's clinical transformation and application. Hence, designing stimuli-responsive nano-sonosensitizers that make use of the lesion's local microenvironment characteristics and US stimulation is an excellent alternative for achieving efficient, specific, and safe treatment. In this review, we provide a comprehensive overview of the currently accepted mechanisms in SDT and discuss the application of responsive nano-sonosensitizers in the treatment of tumor and bacterial infections. Additionally, we emphasize the significance of the principle and process of response, based on the classification of response patterns. Finally, this review emphasizes the potential limitations and future perspectives of SDT that need to be addressed to promote its clinical transformation.

Engineering Cell Membrane-Cloaked Catalysts as Multifaceted Artificial Peroxisomes for Biomedical Applications

Artificial peroxisomes (APEXs) or peroxisome mimics have caught a lot of attention in nanomedicine and biomaterial science in the last decade, which have great potential in clinically diagnosing and treating diseases. APEXs are typically constructed from a semipermeable membrane that encloses natural enzymes or enzyme-mimetic catalysts to perform peroxisome-/enzyme-mimetic activities. The recent rapid progress regarding their biocatalytic stability, adjustable activity, and surface functionality has significantly promoted APEXs systems in real-life applications. In addition, developing a facile and versatile system that can simulate multiple biocatalytic tasks is advantageous. Here, the recent advances in engineering cell membrane-cloaked catalysts as multifaceted APEXs for diverse biomedical applications are highlighted and commented. First, various catalysts with single or multiple enzyme activities have been introduced as cores of APEXs. Subsequently, the extraction and function of cell membranes that are used as the shell are summarized. After that, the applications of these APEXs are discussed in detail, such as cancer therapy, antioxidant, anti-inflammation, and neuron protection. Finally, the future perspectives and challenges of APEXs are proposed and outlined. This progress review is anticipated to provide new and unique insights into cell membrane-cloaked catalysts and to offer significant new inspiration for designing future artificial organelles.

Recent Strategies to Address Hypoxic Tumor Environments in Photodynamic Therapy

Photodynamic therapy (PDT) has become a promising method of cancer treatment due to its unique properties, such as noninvasiveness and low toxicity. The efficacy of PDT is, however, significantly reduced by the hypoxia tumor environments, because PDT involves the generation of reactive oxygen species (ROS), which requires the great consumption of oxygen. Moreover, the consumption of oxygen caused by PDT would further exacerbate the hypoxia condition, which leads to angiogenesis, invasion of tumors to other parts, and metastasis. Therefore, many research studies have been conducted to design nanoplatforms that can alleviate tumor hypoxia and enhance PDT. Herein, the recent progress on strategies for overcoming tumor hypoxia is reviewed, including the direct transport of oxygen to the tumor site by O₂ carriers, the in situ generation of oxygen by decomposition of oxygen-containing compounds, reduced O₂ consumption, as well as the regulation of tumor microenvironments. Limitations and future perspectives of these technologies to improve PDT are also discussed.

Nanodrug-loaded Bifidobacterium bifidum conjugated with anti-death receptor antibody for tumor-targeted photodynamic and sonodynamic synergistic therapy

Using bacteria for tumor-targeted therapy has attracted much attention in recent years. However, how to improve the targeted delivery and cancer therapy efficacy is an important but challenging scientific issue. Herein, a drug delivery system using a probiotic as a carrier was developed for tumor-targeted photodynamic and sonodynamic synergistic therapy. In this system, chlorin e6 (Ce6) nanoparticles (NPs) were prepared and incorporated into B. bifidum, followed by the conjugation of anti-death receptor 5 antibody (anti-DR5 Ab). Interestingly, B. bifidum under 671 nm laser or ultrasound (US) irradiation could generate reactive oxygen species (ROS), and Ce6-B. bifidum-anti-DR5 Ab obtained could target hypoxic regions in tumor with high efficiency after intravenous injection. The ROS level generated by Ce6-B. bifidum-anti-DR5 Ab under both laser and US irradiation was much higher than the combined ROS generated separately using a laser and US for the same probiotics. The cytotoxicity and laryngeal tumor growth-inhibiting efficiency of Ce6-B. bifidum-anti-DR5 Ab under both laser and US irradiation were significant higher than the values obtained using laser or US irradiation alone, which demonstrated the synergistic effect on tumor growth. B. bifidum could be eliminated from the body without exerting harmful effects on mouse health. This strategy is a platform that can be extended to treat other solid tumors. STATEMENT OF SIGNIFICANCE: Using bacteria as drug delivery carriers will show unique advantages. However, how to improve the targeted delivery efficiency and tumor inhibiting capacity is a challenging scientific issue. Herein, a delivery system using a probiotic as carrier was developed for tumor-targeted therapy. In this delivery system, chlorin e6 nanoparticles were prepared and then incorporated into living Bifidobacterium bifidum (B.bifidum), followed by the conjugation of anti-death receptor 5 antibody. This delivery system could efficiently target to mouse tumors, accumulate the hypoxic areas and inhibit the tumor growth through the photodynamic and sonodynamic synergistic effect. Our results will provide a platform for B.bifidum-mediated tumor targeted therapy.

Strategies of engineering nanomedicines for tumor retention

The retention of therapeutic agents in solid tumors at sufficient concentration and duration is crucial for their antitumor effects. Given the important contribution of nanomedicines to oncology, we herein summarized two major strategies of nanomedicines for tumor retention, such as transformation- and interactions-mediated strategies. The transformation-mediated retention strategy was achieved by enlarging particle size of nanomedicines or modulating the morphology into fibrous structures, while the interactions-mediated retention strategy was accomplished by modulating nanomedicines to promote their interactions with versatile cells or components in tumors. Moreover, we provide some considerations and perspectives of tumor-retaining nanomedicines for effective cancer therapy.

Bioinspired Lipoproteins of Furoxans-Oxaliplatin Remodel Physical Barriers in Tumor to Potentiate T-Cell Infiltration

The infiltration of cytotoxic T lymphocytes (CTLs) in tumors is critically challenged by the intricate intratumor physical barriers, which is emerging as an important issue of anticancer immunotherapy. Herein, a reduction-sensitive nitric oxide donor conjugate of furoxans-oxaliplatin is synthesized and a stroma-cell-accessible bioinspired lipoprotein system (S-LFO) is designed, aiming to facilitate CTL infiltration in tumors for anticancer immunotherapy. S-LFO treatment significantly promotes tumor vessel normalization and eliminates multiple components of tumor stroma, ultimately producing a 2.96-fold, 5.02-fold, and 8.65-fold increase of CD3⁺ CD8⁺ T cells, their interferon-γ- and granzyme B-expressing subtypes when comparing to the negative control, and considerably facilitating their trafficking to the cancer cell regions in tumors. Moreover, the combination of S-LFO with an antiprogrammed death ligand-1 produces notable therapeutic benefits of retarded tumor growth and extends survivals in three murine tumor models. Therefore, this study provides an encouraging strategy of remodeling the intratumor physical barriers to potentiate CTL infiltration for anticancer immunotherapy.

Biomimetic ZIF8 Nanosystem With Tumor Hypoxia Relief Ability to Enhance Chemo-Photothermal Synergistic Therapy

Tumor hypoxic microenvironment can reduce the therapeutic effects of chemotherapy, radiotherapy, photodynamic therapy, immunotherapy, etc. It is also a potential source of tumor recurrence and metastasis. A biomimetic nanosystem based on zeolitic imidazolate framework 8 (ZIF8), which had multifunctions of hypoxia relief, chemotherapy, and photothermal therapy, was established to improve tumor hypoxic microenvironment and overcome the corresponding therapeutic resistance. ZIF8 enveloped with DOX and CuS nanoparticles (DC@ZIF8) was synthesized by a sedimentation method. Red blood cell membrane and catalase (CAT) were coated onto DC@ZIF8 and biomimetic nanosystem (DC@ZIF8-MEM_C) was formed. The designed DC@ZIF8-MEM_C had a shape of polyhedron with an average particle size around 254 nm. The loading content of DOX, CAT, and CuS was 4.9%, 6.2%, and 2.5%, separately. The release of DOX from DC@ZIF8-MEM_C was pH dependent and significantly faster at pH 5 due to the degradation of ZIF8. DC@ZIF8-MEM_C exhibited outstanding photothermal conversion properties and excellent antitumor effect in vitro and in vivo. Moreover, the hypoxia relief by CAT was proved to have good sensitization effect on chemo-photothermal combined therapy. DC@ZIF8-MEM_C is a prospective nanosystem, which can realize great chemo-photothermal synergistic antitumor effect under the sensitization of CAT. The biomimetic multifunctional nanoplatform provides a potential strategy of chemo-photothermal synergistic antitumor effect under the sensitization of CAT.

Nanomedicine Strategies to Circumvent Intratumor Extracellular Matrix Barriers for Cancer Therapy

The dense and heterogeneous physical network of the extracellular matrix (ECM) in tumors represents a formidable barrier that limits intratumor drug delivery and the therapeutic efficacy of many anticancer therapies. Here, the two major nanomedicine strategies to circumvent intratumor ECM barriers: regulating the physiochemical properties of nanomedicines and remodeling the components and structure of the ECM are summarized. Nanomedicines can be rationally regulated by optimizing physiochemical properties or designed with biomimetic features to promote ECM permeation capability. Meanwhile, they can also be designed to remodel the ECM by modulating signaling pathways or destroying the components and architecture of the ECM via chemical, biological, or physical treatments. These efforts produce profound improvements in intratumor drug delivery and anticancer efficacy. Moreover, to aid in their anticancer efficacy, feasible approaches for improving ECM-circumventing nanomedicines are proposed.

Tumor-Microenvironment-Responsive Nanomedicine for Enhanced Cancer Immunotherapy

The past decades have witnessed great progress in cancer immunotherapy, which has profoundly revolutionized oncology, whereas low patient response rates and potential immune-related adverse events remain major clinical challenges. With the advantages of controlled delivery and modular flexibility, cancer nanomedicine has offered opportunities to strengthen antitumor immune responses and to sensitize tumor to immunotherapy. Furthermore, tumor-microenvironment (TME)-responsive nanomedicine has been demonstrated to achieve specific and localized amplification of the immune response in tumor tissue in a safe and effective manner, increasing patient response rates to immunotherapy and reducing the immune-related side effects simultaneously. Here, the recent progress of TME-responsive nanomedicine for cancer immunotherapy is summarized, which responds to the signals in the TME, such as weak acidity, reductive environment, high-level reactive oxygen species, hypoxia, overexpressed enzymes, and high-level adenosine triphosphate. Moreover, the potential to combine nanomedicine-based therapy and immunotherapeutic strategies to overcome each step of the cancer-immunity cycle and to enhance antitumor effects is discussed. Finally, existing challenges and further perspectives in this rising field with the hope for improved development of clinical applications are discussed.

Recent advances in in situ oxygen-generating and oxygen-replenishing strategies for hypoxic-enhanced photodynamic therapy

Cancer is a leading cause of death worldwide, accounting for an estimated 10 million deaths by 2020. Over the decades, various strategies for tumor therapy have been developed and evaluated. Photodynamic therapy (PDT) has attracted increasing attention due to its unique characteristics, including low systemic toxicity and minimally invasive nature. Despite the excellent clinical promise of PDT, hypoxia is still the Achilles' heel associated with its oxygen-dependent nature related to increased tumor proliferation, angiogenesis, and distant metastases. Moreover, PDT-mediated oxygen consumption further exacerbates the hypoxia condition, which will eventually lead to the poor effect of drug treatment and resistance and irreversible tumor metastasis, even limiting its effective application in the treatment of hypoxic tumors. Hypoxia, with increased oxygen consumption, may occur in acute and chronic hypoxia conditions in developing tumors. Tumor cells farther away from the capillaries have much lower oxygen levels than cells in adjacent areas. However, it is difficult to change the tumor's deep hypoxia state through different ways to reduce the tumor tissue's oxygen consumption. Therefore, it will become more difficult to cure malignant tumors completely. In recent years, numerous investigations have focused on improving PDT therapy's efficacy by providing molecular oxygen directly or indirectly to tumor tissues. In this review, different molecular oxygen supplementation methods are summarized to alleviate tumor hypoxia from the innovative perspective of using supplemental oxygen. Besides, the existing problems, future prospects and potential challenges of this strategy are also discussed.

Nano drug delivery systems improve metastatic breast cancer therapy

Despite continual progress in the technologies and regimens for cancer therapy, the treatment outcome of fatal metastatic breast cancer is far from satisfactory. Encouragingly, nanotechnology has emerged as a valuable tool to optimize drug delivery process in cancer therapy via preventing the cargos from degradation, improving the tumor-targeting efficiency, enhancing therapeutic agents' retention in specific sites, and controlling drug release. In the last decade, several mechanisms of suppressing tumor metastasis by functional nano drug delivery systems (NDDSs) have been revealed and a guidance for the rational design of anti-metastasis NDDSs is summarized, which consist of three aspects: optimization of physiochemical properties, tumor microenvironment remodeling, and biomimetic strategies. A series of medicinal functional biomaterials and anti-metastatic breast cancer NDDSs constructed by our team are introduced in this review. It is hoped that better anti-metastasis strategies can be inspired and applied in clinic.

Advances of nanomedicines in breast cancer metastasis treatment targeting different metastatic stages

Breast cancer is the most common tumor in women, and the metastasis further increases the malignancy with extremely high mortality. However, there is almost no effective method in the clinic to completely inhibit breast cancer metastasis due to the dynamic multistep process with complex pathways and scattered occurring site. Nowadays, nanomedicines have been evidenced with great potential in treating cancer metastasis. In this review, we summarize the latest research advances of nanomedicines in anti-metastasis treatment. Strategies are categorized according to the metastasis dynamics, including primary tumor, circulating tumor cells, pre-metastatic niches and secondary tumor. In each different stage of metastasis process, nanomedicines are designed specifically with different functions. At the end of the review, we give our perspectives on current limitations and future directions in anti-metastasis therapy. We expect the review provides comprehensive understandings of anti-metastasis therapy for breast cancer, and boosts the clinical translation in the future to improve women's health.

Enolase 1, a Moonlighting Protein, as a Potential Target for Cancer Treatment

Enolase 1 (ENO1) is a moonlighting protein, function as a glycolysis enzyme, a plasminogen receptor and a DNA binding protein. ENO1 play an important role in the process of cancer development. The transcription, translation, post-translational modifying activities and the immunoregulatory role of ENO1 at the cancer development is receiving increasing attention. Some function model studies have shown that ENO1 is a potential target for cancer treatment. In this review, we provide a comprehensive overview of the characterization, function, related transduction cascades of ENO1 and its roles in the pathophysiology of cancers, which is a consequence of ENO1 signaling dysregulation. And the development of novels anticancer agents that targets ENO1 may provide a more attractive option for the treatment of cancers. The data of sarcoma and functional cancer models indicates that ENO1 may become a new potential target for anticancer therapy.

GLUT1 targeting and hypoxia-activating polymer-drug conjugate-based micelle for tumor chemo-thermal therapy

Purpose

Mitochondria are closely correlated with the proliferation and metastasis of tumor for providing suitable micro-environment and energy supply. Herein, we construct a glucose transporter 1 (GLUT1) targeting and hypoxia activating polyprodrug-based micelle (Glu-PEG-Azo-IR808-S-S-PTX) for mitochondria-specific drug delivery and tumor chemo-thermal therapy.

Results

The micelle was characterized by hypoxia-sensitive PEG outer layer detachment, high photo-thermal conversion efficiency, and glutathione (GSH)-sensitive paclitaxel （PTX） release. It showed GLUT1 specifically cellular uptake and hypoxia-sensitive mitochondria targeting on A549 cell. In vivo fluorescence imaging confirmed the micelle also could selectively accumulate in tumor and its mitochondria on A549 tumor-bearing nude mice. Consequently, it not only exhibited higher cytotoxicity, apoptosis rate, and metastasis inhibition rate on A549 cells, but also better tumor growth and metastasis inhibition rate on tumor-bearing nude mice and lower whole-body toxicity. The mechanism might be caused by destroying mitochondria and down-regulating ATP production.

Conclusion

This study provided a GLUT1 targeting, hypoxia, and reductive responsive nanomedicine that hold the potential to be exploited for tumor therapy.

Cytosolic delivery of the immunological adjuvant Poly I:C and cytotoxic drug crystals via a carrier-free strategy significantly amplifies immune response

Co-delivery of chemotherapeutics and immunostimulant or chemoimmunotherapy is an emerging strategy in cancer therapy. The precise control of the targeting and release of agents is critical in this methodology. This article proposes the asynchronous release of the chemotherapeutic agents and immunostimulants to realize the synergistic effect between chemotherapy and immunotherapy. To obtain a proof-of-concept, a co-delivery system was prepared via a drug-delivering-drug (DDD) strategy for cytosolic co-delivery of Poly I:C, a synthetic dsRNA analog to activate RIG-I signaling, and PTX, a commonly used chemotherapeutics, in which pure PTX nanorods were sequentially coated with Poly I:C and mannuronic acid via stimulating the RIG-I signaling axis. The co-delivery system with a diameter of 200 nm enables profound immunogenicity of cancer cells, exhibiting increased secretion of cytokines and chemokines, pronounced immune response in vivo, and significant inhibition of tumor growth. Also, we found that intracellularly sustained release of cytotoxic agents could elicit the immunogenicity of cancer cells. Overall, the intracellular asynchronous release of chemotherapeutics and immunomodulators is a promising strategy to promote the immunogenicity of cancer cells and augment the antitumor immune response.