Early phago-/endosomal escape of platinum drugs via ROS-responsive micelles for dual cancer chemo/immunotherapy

Platinum-based chemotherapy: trends in organic nanodelivery systems

Despite the investment in platinum drugs research, cisplatin, carboplatin and oxaliplatin are still the only Pt-based compounds used as first line treatments for several cancers, with a few other compounds being approved for administration in some Asian countries. However, due to the severe and worldwide impact of oncological diseases, there is an urge for improved chemotherapeutic approaches. Furthermore, the pharmaceutical application of platinum complexes is hindered by their inherent toxicity and acquired resistance. Nanodelivery systems rose as a key strategy to overcome these challenges, with recognized versatility and ability towards improving the safety, bioavailability and efficacy of the available drugs. Among the known nanocarriers, organic systems have been widely applied, taking advantage of their potential as drug vehicles. Researchers have mainly focused on the development of lipidic and polymeric carriers, including supramolecular structures, with an overall improvement of encapsulated platinum complexes. Herein, an overview of recent trends and strategies is presented, with the main focus on the encapsulation of platinum compounds into organic nanocarriers, showcasing the evolution in the design and development of these promising systems. This comprehensive review highlights formulation methods as well as characterization procedures, providing insights that may be helpful for the development of novel platinum nanocarriers aiming at future pharmaceutical applications.

Nano-Engineering Strategies for Tumor-Specific Therapy

Nanodelivery systems (NDSs) provide promising prospects for decreasing drug doses, reducing side effects, and improving therapeutic effects. However, the bioapplications of NDSs are still compromised by their fast clearance, indiscriminate biodistribution, and limited tumor accumulation. Hence, engineering modification of NDSs aiming at promoting tumor-specific therapy and avoiding systemic toxicity is usually needed. An NDS integrating various functionalities, including flexible camouflage, specific biorecognition, and sensitive stimuli-responsiveness, into one sequence would be "smart" and highly effective. Herein, we systematically summarize the related principles, methods, and progress. At the end of the review, we predict the obstacles to precise nanoengineering and prospects for the future application of NDSs.

Selenium promotes immunogenic radiotherapy against cervical cancer metastasis through evoking P53 activation

Radiotherapy is still the recommended treatment for cervical cancer. However, radioresistance and radiation-induced side effects remain one of the biggest clinical problems. Selenium (Se) has been confirmed to exhibit radiation-enhancing effects for cancer treatment. However, Se species dominate the biological activities and which form of Se possesses better radiosensitizing properties and radiation safety remains elusive. Here, different Se species (the valence state of Se ranged from - 2, 0, +4 to + 6) synergy screen was carried out to identify the potential radiosensitizing effects and radiation safety of Se against cervical cancer. We found that the therapeutic effects varied with the changes in the Se valence state. Sodium selenite (+4) displayed strong cancer-killing effects but also possessed severe cytotoxicity. Sodium selenate (+6) neither enhanced the killing effects of X-ray nor possessed anticancer activity by its alone treatment. Although nano-selenium (0), especially Let-SeNPs, has better radiosensitizing activity, the - 2 organic Se, such as selenadiazole derivative SeD (-2) exhibited more potent anticancer effects and possessed a higher safe index. Overall, the selected Se drugs were able to synergize with X-ray to inhibit cell growth, clone formation, and cell migration by triggering G2/M phase arrest and apoptosis, and SeD (-2) was found to exhibit more potent enhancing capacity. Further mechanism studies showed that SeD mediated p53 pathway activation by inducing DNA damage through promoting ROS production. Additionally, SeD combined with X-ray therapy can induce an anti-tumor immune response in vivo. More importantly, SeD combined with X-ray significantly inhibited the liver metastasis of tumor cells and alleviated the side effects caused by radiation therapy in tumor-bearing mice. Taken together, this study demonstrates the radiosensitization and radiation safety effects of different Se species, which may shed light on the application of such Se-containing drugs serving as side effects-reducing agents for cervical cancer radiation treatment.

Tumor-associated macrophages in colorectal cancer metastasis: molecular insights and translational perspectives

Metastasis is the leading cause of high mortality in colorectal cancer (CRC), which is not only driven by changes occurring within the tumor cells, but is also influenced by the dynamic interaction between cancer cells and components in the tumor microenvironment (TME). Currently, the exploration of TME remodeling and its impact on CRC metastasis has attracted increasing attention owing to its potential to uncover novel therapeutic avenues. Noteworthy, emerging studies suggested that tumor-associated macrophages (TAMs) within the TME played important roles in CRC metastasis by secreting a variety of cytokines, chemokines, growth factors and proteases. Moreover, TAMs are often associated with poor prognosis and drug resistance, making them promising targets for CRC therapy. Given the prognostic and clinical value of TAMs, this review provides an updated overview on the origin, polarization and function of TAMs, and discusses the mechanisms by which TAMs promote the metastatic cascade of CRC. Potential TAM-targeting techniques for personalized theranostics of metastatic CRC are emphasized. Finally, future perspectives and challenges for translational applications of TAMs in CRC development and metastasis are proposed to help develop novel TAM-based strategies for CRC precision medicine and holistic healthcare.

PdMo nanoflowers for endogenous/exogenous-stimulated nanocatalytic therapy

The clinical application of reactive oxygen species (ROS)-mediated tumor treatment has been critically limited by inefficient ROS generation. Herein, we rationally synthesized and constructed the three-dimensional PdMo nanoflowers through a one-pot solvothermal reduction method for elaborately regulated peroxidase-like enzymatic activity and glutathione peroxidase-like enzymatic activity, to promote oxidation ROS evolvement and antioxidation glutathione depletion for achieving intensive ROS-mediated tumor therapy. The three-dimensional superstructure composed of two-dimensional nanosheet subunits can solve the issues by avoiding the appearance of tightly stacked crystalline nanostructures. Significantly, Mo is chosen as a second metal to alloy with Pd because of its more chemical valence and negative ionization energy than Pd for improved electron transfer efficiencies and enhanced enzyme-like activities. In addition, the photothermal effect generated by PdMo nanoflowers could also enhance its enzymatic activities. Thus, this work provides a promising paradigm for achieving highly ROS-mediated tumor therapeutic efficacy by regulating the multi-enzymatic activities of Pd-based nanoalloys.

Mechanisms and applications of radiation-induced oxidative stress in regulating cancer immunotherapy

Radiotherapy (RT) is an effective treatment option for cancer patients, which induces the production of reactive oxygen species (ROS) and causes oxidative stress (OS), leading to the death of tumor cells. OS not only causes apoptosis, autophagy and ferroptosis, but also affects tumor immune response. The combination of RT and immunotherapy has revolutionized the management of various cancers. In this process, OS caused by ROS plays a critical role. Specifically, RT-induced ROS can promote the release of tumor-associated antigens (TAAs), regulate the infiltration and differentiation of immune cells, manipulate the expression of immune checkpoints, and change the tumor immune microenvironment (TME). In this review, we briefly summarize several ways in which IR induces tumor cell death and discuss the interrelationship between RT-induced OS and antitumor immunity, with a focus on the interaction of ferroptosis with immunogenic death. We also summarize the potential mechanisms by which ROS regulates immune checkpoint expression, immune cells activity, and differentiation. In addition, we conclude the therapeutic opportunity improving radiotherapy in combination with immunotherapy by regulating OS, which may be beneficial for clinical treatment.

Engineered Enzyme-Loaded Erythrocyte Vesicles Precisely Deprive Tumoral Nutrients to Induce Synergistic Near-Infrared-II Photothermal Therapy and Immune Activation

Starvation therapy has been considered a promising strategy in cancer treatment for altering the tumor microenvironment (TME) and causing a cascade of therapeutic effects. However, it is still highly challenging to establish a therapeutic strategy for precisely and potently depriving tumoral nutrition. In this study, a glucose oxidase (GOx) and thrombin-incorporated erythrocyte vesicle (EV) with cyclic (Arg-Gly-Asp) (cRGD) peptide modification, denoted as EV@RGT, were synthesized for precisely depriving tumoral nutrition and sequentially inducing second near-infrared region (NIR-II) photothermal therapy (PTT) and immune activation. The EV@RGT could specifically accumulate at the tumor site and release the enzymes at the acidic TME. The combination of GOx and thrombin exhausts tumoral glucose and blocks the nutrition supply at the same time, resulting in severe energy deficiency and reactive oxygen species (ROS) enrichment within tumor cells. Subsequently, the abundant clotted erythrocytes in tumor vessels present outstanding localized NIR-II PTT for cancer eradication owing to the hemoglobin. Furthermore, the abundant ROS generated by enhanced starvation therapy repolarizes resident macrophages into the antitumor M1 phenotype via a DNA damage-induced STING/NF-κB pathway, ultimately contributing to tumor elimination. Consequently, the engineered EV@RGT demonstrates powerful antitumor efficiency based on precise nutrition deprivation, sequential NIR-II PTT, and immune activation effect. This work provides an effective strategy for the antitumor application of enzyme-based reinforced starvation therapy.

Lipid-functionalized gold nanorods with plug-to-direct mitochondria targeting ligand for synergetic photothermal-chemotherapy of tumor therapy

Mitochondria targeting therapeutic strategies are promising for more effective and precise cancer therapy. Photothermal therapy are extensively studied as noninvasive cancer treatment. With regards to all-in-one nanocarrier-mediated drug delivery platform, it is still a challenge to enhance one of the features but not compromise other merits. Herein, we present a mitochondrial targeting photothermal-chemotherapy all-in-one nanoplatform involving lipid-functionalized gold nanorods (AuNR) with plug-to-direct mitochondria targeting ligand for synergetic enhanced tumor therapy. Firstly, AuNR were modified by DSPE-PEG-SH owing to the special affinity of sulfhydryl group and gold. And then, DSPE-PEG-DOX with mitochondrial targeting character was directly inserted into DSPE-PEG-SH layer. Meanwhile, paclitaxel (PTX) was loaded in hydrophobic region of the lipid layer. Quite different from introducing additional mitochondrial targeting molecules, we incorporated amphiphilic DSPE-PEG-DOX into a DSPE-PEG-SH layer modified around AuNR to achieve both mitochondrial targeting, photothermal and dual drug loading in a simple AuNR-lipid-DOX/PTX platform, in the case that efficiently enhanced production of reactive oxygen species (ROS) in mitochondria and excellent anti-tumor efficacy were achieved. With good biocompatibility, the constructed nanoplatform based on lipid-functionalized AuNR synergistically combined mitochondrial targeted DSPE-PEG-DOX with mitochondrial-acted PTX and photothermal therapy (PTT), which provided a feasible strategy for organelle-targeted combination PTT-chemotherapy to improve therapeutic effects.

Older but Stronger: Development of Platinum-Based Antitumor Agents and Research Advances in Tumor Immunity

Platinum (Pt) drugs have developed rapidly in clinical applications because of their broad and highly effective antitumor effects. In recent years, with the rapid development of immunotherapy, Pt-based antitumor agents have gained new challenges and opportunities. Since the discovery of their pharmacological effects in immunotherapy and tumor microenvironment regulation, research into Pt drugs has progressed to multi-ligand and multi-functional Pt precursors and their own shortcomings have been further highlighted. With the development of antitumor immunotherapy and the rise of combination therapy, the development of Pt-based drugs has started to move in the direction of multi-targeting, nanocarrier modification, immunotherapy and photodynamic therapy. In this paper, we first overview the recent applications of Pt-based drugs in antitumor inorganic chemistry, with a focus on summarizing the application of Pt-based drugs and their precursors in the anticancer immune response. The paper also provides a reasonable outlook on the future development of Pt-based drugs from the chemical and immunological perspectives, relying on the existing content and problems of Pt-based drug development. On the basis of the gathered information, joint multidisciplinary programs on implementing comprehensive immune analyses for the future development of novel anticancer metal compounds should be initiated.

A CaCO3-based synergistic immunotherapy strategy for treating primary and distal tumors

Low response rate limits the widespread application of cancer immunotherapy. To improve the response rate of immunotherapy, a CaCO₃-based composite nanomaterial was developed to induce immunogenic cell death for enhancing immunotherapy against 4T1 primary and distal tumors.

A self-cascaded unimolecular prodrug for pH-responsive chemotherapy and tumor-detained photodynamic-immunotherapy of triple-negative breast cancer

Despite the success of immune checkpoint blockade (ICB) therapy in cancer management, ICB-based immunotherapy of triple-negative breast cancer (TNBC) still suffers from immunosuppressive tumor microenvironment (ITM). To break through the bottleneck of TNBC immunotherapy, a self-cascaded unimolecular prodrug consisting of an acidic pH-activatable doxorubicin and an aggregation-induced emission luminogen (AIEgen) photosensitizer coupled to a caspase-3-responsive peptide was engineered. The generated prodrug, could not only release doxorubicin initiatively in acidic tumor microenvironment, but also activate apoptosis-related caspase-3. The activated caspase-3 could in turn trigger release and in situ aggregation of photosensitizers. Importantly, the unimolecular prodrug exhibits a renal clearance pathway similar to small molecules in vivo, while the aggregated AIEgens prolong tumor retention for long-term fluorescence imaging and repeatable photodynamic therapy (PDT) by only one single-dose injection. Furthermore, the tumor-detained PDT boosts both immunogenic cell death of TNBC cells and maturation of dendritic cells. Finally, the combination of repeatable PDT with ICB therapy further promotes the proliferation and intratumoral infiltration of cytotoxic T lymphocytes, and effectively suppresses tumor growth and pulmonary metastasis. This prodrug is a proof-of-concept that confirms the first self-cascaded chemo-PDT strategy to reverse the ITM and boost the ICB-mediated TNBC immunotherapy.

Lysosomal-mediated drug release and activation for cancer therapy and immunotherapy

The development of carrier systems that are able to transport and release therapeutics to target cells is an emergent strategy to treat cancer; however, they following endocytosis are usually trapped in the endo/lysosomal compartments. The efficacy of drug conjugates and nanotherapeutics relies critically on their intracellular drug release ability, for which advanced systems responding to the unique lysosomal environment such as acidic pH and abundant enzymes (e.g. cathepsin B, sulfatase and β-glucuronidase) or equipped with photochemical internalization property have been energetically pursued. In this review, we highlight the recent designs of smart systems that promote efficient lysosomal release and/or escape of anticancer agents including chemotherapeutics (e.g. doxorubicin, platinum, chloroquine and hydrochloroquine) and biotherapeutics (e.g. proteins, siRNA, miRNA, mRNA and pDNA) to cancer cells or immunotherapeutic agents (e.g. antigens, mRNA and immunoadjuvants) to antigen-presenting cells (APCs), thereby boosting cancer therapy and immunotherapy. Lysosomal-mediated drug release presents an appealing approach to develop innovative cancer therapeutics and immunotherapeutics.

Colorimetric/SERS dual-channel nanoprobe for reactive oxygen species monitoring in elucidating the mechanism of chemotherapeutic drugs action on cancer cells

Reactive oxygen species (ROS) are involved in drug-induced cytotoxicity by regulating cell signaling, inducing oxidative stress, and damaging the DNA and proteins. Examining ROS production in cells under the stimulation of chemotherapeutic drugs is of great importance for understanding the ROS roles and identifying the mechanism of drug-induced cytotoxicity. Here, a silver/gold (Ag/Au) nanoshell-based colorimetric and surface-enhanced Raman spectroscopy (SERS) dual-response nanoprobe was proposed for ROS sensing on the basis of Ag etching. In this study, as a kind of ROS, hydrogen peroxide (H₂O₂) was detected by the prepared nanoprobe. The linear ranges of 0.5-100 μM with a limit of detection (LOD) of 0.343 μM for the colorimetric determination and 1-50 μM with LOD of 0.294 μM for SERS determination were achieved. The detection of cellular ROS concentration after stimulation by cisplatin, paclitaxel, doxorubicin, and 5-fluorouracil was validated by the nanoprobe. The nanoprobe could also be used to detect the signal pathway of ROS production by cisplatin stimulation. This study provided a simple and novel dual-response nanoplatform for detecting and monitoring ROS in cells, which holds great potential for elucidating the mechanism of occurrence and treatment of ROS-involved diseases.

Oxidative Stress in Cancer Immunotherapy: Molecular Mechanisms and Potential Applications

Immunotherapy is an effective treatment option that revolutionizes the management of various cancers. Nevertheless, only a subset of patients receiving immunotherapy exhibit durable responses. Recently, numerous studies have shown that oxidative stress induced by reactive oxygen species (ROS) plays essential regulatory roles in the tumor immune response, thus regulating immunotherapeutic effects. Specifically, studies have revealed key roles of ROS in promoting the release of tumor-associated antigens, manipulating antigen presentation and recognition, regulating immune cell phenotypic differentiation, increasing immune cell tumor infiltration, preventing immune escape and diminishing immune suppression. In the present study, we briefly summarize the main classes of cancer immunotherapeutic strategies and discuss the interplay between oxidative stress and anticancer immunity, with an emphasis on the molecular mechanisms underlying the oxidative stress-regulated treatment response to cancer immunotherapy. Moreover, we highlight the therapeutic opportunities of manipulating oxidative stress to improve the antitumor immune response, which may improve the clinical outcome.

Metallodrugs in cancer nanomedicine

Metal complexes are extensively used for cancer therapy. The multiple variables available for tuning (metal, ligand, and metal-ligand interaction) offer unique opportunities for drug design, and have led to a vast portfolio of metallodrugs that can display a higher diversity of functions and mechanisms of action with respect to pure organic structures. Clinically approved metallodrugs, such as cisplatin, carboplatin and oxaliplatin, are used to treat many types of cancer and play prominent roles in combination regimens, including with immunotherapy. However, metallodrugs generally suffer from poor pharmacokinetics, low levels of target site accumulation, metal-mediated off-target reactivity and development of drug resistance, which can all limit their efficacy and clinical translation. Nanomedicine has arisen as a powerful tool to help overcome these shortcomings. Several nanoformulations have already significantly improved the efficacy and reduced the toxicity of (chemo-)therapeutic drugs, including some promising metallodrug-containing nanomedicines currently in clinical trials. In this critical review, we analyse the opportunities and clinical challenges of metallodrugs, and we assess the advantages and limitations of metallodrug delivery, both from a nanocarrier and from a metal-nano interaction perspective. We describe the latest and most relevant nanomedicine formulations developed for metal complexes, and we discuss how the rational combination of coordination chemistry with nanomedicine technology can assist in promoting the clinical translation of metallodrugs.

Biodegradable Metal-Organic-Framework-Gated Organosilica for Tumor-Microenvironment-Unlocked Glutathione-Depletion-Enhanced Synergistic Therapy

The clinical employment of cisplatin (cis-diamminedichloroplatinum(II) (CDDP)) is largely constrained due to the non-specific delivery and resultant serious systemic toxicity. Small-sized biocompatible and biodegradable hollow mesoporous organosilica (HMOS) nanoparticles show superior advantages for targeted CDDP delivery but suffer from premature CDDP leakage. Herein, the smart use of a bimetallic Zn²⁺ /Cu²⁺ co-doped metal-organic framework (MOF) is made to block the pores of HMOS for preventing potential leakage of CDDP and remarkably increasing the loading capacity of HMOS. Once reaching the acidic tumor microenvironment (TME), the outer MOF can decompose quickly to release CDDP for chemotherapy against cancer. Besides, the concomitant release of dopant Cu²⁺ can deplete the intracellular glutathione (GSH) for increased toxicity of CDDP as well as catalyzing the decomposition of intratumoral H₂ O₂ into highly toxic •OH for chemodynamic therapy (CDT). Moreover, the substantially reduced GSH can also protect the yielded •OH from scavenging and thus greatly improve the •OH-based CDT effect. In addition to providing a hybrid HMOS@MOF nanocarrier, this study is also expected to establish a new form of TME-unlocked nanoformula for highly efficient tumor-specific GSH-depletion-enhanced synergistic chemotherapy/chemodynamic therapy.

Design of Smart Size-, Surface-, and Shape-Switching Nanoparticles to Improve Therapeutic Efficacy

Multiple biological barriers must be considered in the design of nanomedicines, including prolonged blood circulation, efficient accumulation at the target site, effective penetration into the target tissue, selective uptake of the nanoparticles into target cells, and successful endosomal escape. However, different particle sizes, surface chemistries, and sometimes shapes are required to achieve the desired transport properties at each step of the delivery process. In response, this review highlights recent developments in the design of switchable nanoparticles whose size, surface chemistry, shape, or a combination thereof can be altered as a function of time, a disease-specific microenvironment, and/or via an externally applied stimulus to enable improved optimization of nanoparticle properties in each step of the delivery process. The practical use of such nanoparticles in chemotherapy, bioimaging, photothermal therapy, and other applications is also discussed.

Multistage Cooperative Nanodrug Combined with PD-L1 for Enhancing Antitumor Chemoimmunotherapy

Combinatorial CpG oligonucleotide (CPG) and chemotherapy drug represent a promising approach to reactivate immune system. However, these two agents possess different physicochemical properties, hindering the application of direct self-assembly of these two cargos into a single nanostructure. Here, a multistage cooperative nanodrug is developed by the direct self-assembly of cis-platinum (CDDP, Pt), l-arginine (l-Arg, R), and CPG (defined as PtR/CPG) for antitumor chemoimmunotherapy. First, the CDDP can induce cell apoptosis. Meanwhile, CDDP also promotes the production of H₂ O₂ , catalyzing the conversion of l-Arg into nitric oxide (NO). The generated NO decreases the multidrug resistance of cells toward CDDP. Thus, the synergistic effects of CDDP and NO can trigger immunogenic cell death to produce tumor-associated antigens (TAAs). The TAAs and CPG will induce the maturation of dendritic cells (DCs) and enhance antigen presentation ability of DCs. In this way, the PtR/CPG can reverse the immunosuppressive microenvironment, sensitizing tumors to immune checkpoint inhibitors mediated by the programmed death-ligand 1 (PD-L1) antibody. Furthermore, the PtR/CPG combined with the PD-L1 antibody decreases the exhaustion and dysfunction of cytotoxic T lymphocytes to elicit durable systemic immune response. As a result, the prepared PtR/CPG nanodrug in combination with PD-L1 may be highly significant for cancer immunotherapy.

BSA-MnO2-SAL multifunctional nanoparticle-mediated M1 macrophages polarization for glioblastoma therapy

Glioblastoma (GBM) is a type of brain tumour with a very high fatality rate. Owing to the presence of the blood-brain barrier (BBB), it is difficult for drugs to reach the tumour site; thus, there has been little progress in GBM chemotherapeutics. Furthermore, the malignant growth of tumours largely depends on the tumour microenvironment. GBM is especially prevalent in slightly acidic, hydrogen peroxide (H₂O₂)-rich, hypoxic, and immunosuppressive microenvironments. Tumour-supporting macrophages (M₂ macrophages) are a type of immune cell that promote tumour growth. Therefore, targeting M₂ macrophages and repolarizing them into tumour-suppressor macrophages (M₁ macrophages) are important strategies for GBM treatment. Salinomycin (SAL) is an anti-tumour drug that can improve the tumour immune microenvironment. Interestingly, we found that SAL promoted the expression of M₁ macrophages in vitro, but its ability was limited in vivo because of the presence of the BBB. In this study, we combined SAL and MnO₂ to design bovine serum albumin-MnO₂-SAL (BMS), a nanoparticle that responds to acidic and H₂O₂-rich microenvironments. Our experimental results showed that BMS reduced GBM growth efficiency and had the ability to penetrate the BBB. It also enhanced the repolarization ability of SAL owing to the production of Mn²⁺ after decomposition, which could be applied in Magnetic Resonance Imaging (MRI). This study demonstrated that the multifunctional nanoparticle BMS is of great significance in inhibiting orthotopic GBM growth and improving immunosuppressive microenvironments.