Enhanced Melanoma-Targeted Therapy by "Fru-Blocked" Phenyboronic Acid-Modified Multiphase Antimetastatic Micellar Nanoparticles

Design of a targeted dual drug delivery system for boosting the efficacy of photoimmunotherapy against melanoma proliferation and metastasis

INTRODUCTION

The combination of a photosensitizer and indoleamine-2,3 dioxygenase (IDO) inhibitor provides a promising photoimmunotherapy (PIT) strategy for melanoma treatment. A dual drug delivery system offers a potential approach for optimizing the inhibitory effects of PIT on melanoma proliferation and metastasis.

OBJECTIVE

To develop a dual drug delivery system based on PIT and to study its efficacy in inhibiting melanoma proliferation and metastasis.

METHODS

We constructed a multifunctional nano-porphyrin material (P18-APBA-HA) using the photosensitizer-purpurin 18 (P18), hyaluronic acid (HA), and 4-(aminomethyl) phenylboronic acid (APBA). The resulting P18-APBA-HA was inserted into a phospholipid membrane and the IDO inhibitor epacadostat (EPA) was loaded into the internal phase to prepare a dual drug delivery system (Lip\EPA\P18-APBA-HA). Moreover, we also investigated its physicochemical properties, targeting, anti-tumor immunity, and anti-tumor proliferation and metastasis effects.

RESULTS

The designed system utilized the pH sensitivity of borate ester to realize an enhanced-targeting strategy to facilitate the drug distribution in tumor lesions and efficient receptor-mediated cellular endocytosis. The intracellular release of EPA from Lip\EPA\P18-APBA-HA was triggered by thermal radiation, thereby inhibiting IDO activity in the tumor microenvironment, and promoting activation of the immune response. Intravenous administration of Lip\EPA\P18-APBA-HA effectively induced anti-tumor immunity by promoting dendritic cell maturation, cytotoxic T cell activation, and regulatory T cell suppression, and regulating cytokine secretion, to inhibit the proliferation of melanoma and lung metastasis.

CONCLUSION

The proposed nano-drug delivery system holds promise as offers a promising strategy to enhance the inhibitory effects of the combination of EPA and P18 on melanoma proliferation and metastasis.

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.

A pH/ROS dual-responsive system for effective chemoimmunotherapy against melanoma via remodeling tumor immune microenvironment

Chemotherapeutics can induce immunogenic cell death (ICD) in tumor cells, offering new possibilities for cancer therapy. However, the efficiency of the immune response generated is insufficient due to the inhibitory nature of the tumor microenvironment (TME). Here, we developed a pH/reactive oxygen species (ROS) dual-response system to enhance chemoimmunotherapy for melanoma. The system productively accumulated in tumors by specific binding of phenylboronic acid (PBA) to sialic acids (SA). The nanoparticles (NPs) rapidly swelled and released quercetin (QUE) and doxorubicin (DOX) upon the stimulation of tumor microenvironment (TME). The in vitro and in vivo results consistently demonstrated that the NPs improved anti-tumor efficacy and prolonged survival of mice, significantly enhancing the effects of the combination. Our study revealed DOX was an ICD inducer, stimulating immune responses and promoting maturation of dendritic cells (DCs). Additionally, QUE served as a TME regulator by inhibiting the cyclooxygenase-2 (COX2)-prostaglandin E2 (PGE2) axis, which influenced various immune cells, including increasing cytotoxic T cells (CLTs) infiltration, promoting M1 macrophage polarization, and reducing regulatory T cells (Tregs) infiltration. The combination synergistically facilitated chemoimmunotherapy efficacy by remodeling the immunosuppressive microenvironment. This work presents a promising strategy to increase anti-tumor efficiency of chemotherapeutic agents.

Polysaccharide-Based Stimulus-Responsive Nanomedicines for Combination Cancer Immunotherapy

Cancer immunotherapy is a promising antitumor approach, whereas nontherapeutic side effects, tumor microenvironment (TME) intricacy, and low tumor immunogenicity limit its therapeutic efficacy. In recent years, combination immunotherapy with other therapies has been proven to considerably increase antitumor efficacy. However, achieving codelivery of the drugs to the tumor site remains a major challenge. Stimulus-responsive nanodelivery systems show controlled drug delivery and precise drug release. Polysaccharides, a family of potential biomaterials, are widely used in the development of stimulus-responsive nanomedicines due to their unique physicochemical properties, biocompatibility, and modifiability. Here, the antitumor activity of polysaccharides and several combined immunotherapy strategies (e.g., immunotherapy combined with chemotherapy, photodynamic therapy, or photothermal therapy) are summarized. More importantly, the recent progress of polysaccharide-based stimulus-responsive nanomedicines for combination cancer immunotherapy is discussed, with the focus on construction of nanomedicine, targeted delivery, drug release, and enhanced antitumor effects. Finally, the limitations and application prospects of this new field are discussed.

Recent advances in targeting myeloid-derived suppressor cells and their applications to radiotherapy

Myeloid-derived suppressor cells (MDSCs) are a group of heterogenous immature myeloid cells with potent immune suppressive properties that not only constrain anti-tumor immune activation and functions, promote tumor progression, but also contribute to treatment resistance and tumor relapse. Targeting MDSCs may be a promising new cancer treatment method, but there is still a problem of low treatment efficiency. Combined application with radiotherapy may be a potential method to solve this problem. Drug delivery systems (DDSs) provide more efficient targeted drug delivery capability and can reduce the toxicity and side effects of drugs. Recent advance in DDSs targeting development, recruitment, differentiation, and elimination of MDSCs have shown promising effect in reversing immune inhibition and in overcoming radiotherapy resistance. In this review, we systematically summarized DDSs applied to target MDSCs for the first time, and classified and discussed it according to its different mechanisms of action. In addition, this paper also reviewed the biological characteristics of MDSCs and their role in the initiation, progression, and metastasis of cancer. Moreover, this review also summarizes the role of DDSs targeting MDSCs in radiosensitization. Finally, the future development of DDSs targeting MDSCs is also prospected.

Reactive oxygen species-powered cancer immunotherapy: Current status and challenges

Reactive oxygen species (ROS) are crucial signaling molecules that can arouse immune system. In recent decades, ROS has emerged as a unique therapeutic strategy for malignant tumors as (i) it can not only directly reduce tumor burden but also trigger immune responses by inducing immunogenic cell death (ICD); and (ii) it can be facilely generated and modulated by radiotherapy, photodynamic therapy, sonodynamic therapy and chemodynamic therapy. The anti-tumor immune responses are, however, mostly downplayed by the immunosuppressive signals and dysfunction of effector immune cells within the tumor microenvironment (TME). The past years have seen fierce developments of various strategies to power ROS-based cancer immunotherapy by e.g. combining with immune checkpoints inhibitors, tumor vaccines, and/or immunoadjuvants, which have shown to potently inhibit primary tumors, metastatic tumors, and tumor relapse with limited immune-related adverse events (irAEs). In this review, we introduce the concept of ROS-powered cancer immunotherapy, highlight the innovative strategies to boost ROS-based cancer immunotherapy, and discuss the challenges in terms of clinical translation and future perspectives.

A novel combination for the treatment of small cell lung cancer: Active targeted irinotecan and stattic co-loaded PLGA nanoparticles

Polymeric nanoparticles are widely used drug delivery systems for cancer treatment due to their properties such as ease of passing through biological membranes, opportunity to modify drug release, specifically targeting drugs to diseased areas, and potential of reducing side effects. Here, we formulated irinotecan and Stattic co-loaded PLGA nanoparticles targeted to small cell lung cancer. Nanoparticles were successfully conjugated with CD56 antibody with a conjugation efficiency of 84.39 ± 1.01%, and characterization of formulated nanoparticles was conducted with in-vitro and in-vivo studies. Formulated particles had sizes in the range of 130-180 nm with PDI values smaller than 0.3. Encapsulation and active targeting of irinotecan and Stattic resulted in increased cytotoxicity and anti-cancer efficiency in-vitro. Furthermore, it was shown with ex-vivo biodistribution studies that conjugated nanoparticles were successfully targeted to CD56-expressing SCLC cells and distributed mainly to tumor tissue and lungs. Compliant with our hypothesis and literature, the STAT3 pathway was successfully inhibited with Stattic solution and Stattic loaded nanoparticles. Additionally, intravenous injection of conjugated co-loaded nanoparticles resulted in decreased side effects and better anti-tumor activity than individual solutions of drugs in SCLC tumor-bearing mice. These results may indicate a new treatment option for clinically aggressive small cell lung cancer.

Inflammation-targeted cannabidiol-loaded nanomicelles for enhanced oral mucositis treatment

One of the most common complications of cancer chemotherapy is oral mucositis (OM), a serious kind of oral ulceration, but its effective treatment remains a serious challenge. In this study, we used deoxycholic acid and fucoidan to prepare inflammation-targeting nanomicelles (FD), because fucoidan can target inflammation due to its high binding affinity for P-selectin. The hydrophobic anti-inflammatory drug cannabidiol (CBD) was then loaded into the hydrophobic core of FD. The resulting CBD-loaded FD micelles (CBD/FD) had uniform particle size and morphology, as well as favorable serum stability. Moreover, administration of the FD micelles via intravenous injection or in situ dripping in an OM mouse model enhanced the accumulation and retention of CBD. CBD/FD also showed a better anti-inflammatory effect compared to free CBD after local or systemic administration in vivo, while they accelerated OM healing and inhibited Ly6G inflammatory cell infiltration and NF-κB nuclear transcription. Our results show that CBD/FD nanomicelles are a promising agent for OM treatment.

Phenylboronic-acid-based Functional Chemical Materials for Fluorescence Imaging and Tumor Therapy

Various functional chemical materials have been widely used in imaging and tumor therapy. Targeted ligands such as antibodies, peptides, and small molecules have been combined with functional materials to enhance cellular uptake and are used for active targeting of cancer cells and tumors. Among them, phenylboronic acid (PBA), as a small molecular ligand, has the characteristics of low cytotoxicity and easy modification. PBA improves the cancer cell imaging and tumor treatment effect by binding to glycans on the surface of cancer cells. In this Mini-Review, we introduced the modification strategy and targeting strategy of PBA. We focused on the applications of PBA-based functional materials in fluorescence imaging and tumor therapy. For fluorescence imaging, the potential of PBA-based functional chemical materials in cancer diagnosis and tumor targeting was proved by cell imaging and in vivo imaging. For tumor therapy, we mainly discussed the applications of PBA-based functional chemical materials in chemotherapy, gene therapy, phototherapy, and immunotherapy. PBA-based functional chemical materials provide a useful method for cancer diagnosis and treatment.

Reactive Oxygen Species-Responsive Celastrol-Loaded : Bilirubin Nanoparticles for the Treatment of Rheumatoid Arthritis

Celastrol (CLT) has shown anti-rheumatic activity against rheumatoid arthritis, while its poor water solubility and high organ toxicity restrict its further therapeutic applications. To mitigate these challenges, a reactive oxygen species (ROS)-responsive nanoparticle was developed for celastrol delivery based on the excessive ROS at the pathologic sites, which was synthesized by conjugating bilirubin to a polyethylene glycol (PEG) chain. The PEGylated bilirubin self-assembled into nanoparticle (BRNP) in aqueous solution had a hydrodynamic diameter of around 68.6 nm, and celastrol was loaded into BRNP (CLT/BRNP) with a drug encapsulation efficiency of 72.6% and a loading capacity of 6.6%. In vitro study revealed that CLT/BRNP exhibited the capacity of scavenging intracellular ROS and down-regulating the level of nitric oxide after it was effectively internalized by activated macrophages. Furthermore, in adjuvant-induced arthritis rats, BRNP was accumulated preferentially at inflamed joints, alleviating the joint swelling and bone erosion, which significantly decreased the secretion of pro-inflammatory cytokines to suppress the RA progression. Importantly, CLT/BRNP markedly enhanced its anti-arthritic effect and attenuated the toxic effect compared with free celastrol. Taken together, our results suggested that CLT/BRNP could be used for targeted drug delivery in rheumatoid arthritis.

Hierarchical dual-responsive cleavable nanosystem for synergetic photodynamic/photothermal therapy against melanoma

Currently, the combining photodynamic therapy (PDT) with photothermal therapy (PTT) modalities based on a single near infrared (NIR) laser irradiation and highly selective internalization still remain a challenge. Herein, a hierarchical dual-responsive cleavable nanosystem for synergetic NIR triggered PDT/PTT is reported. The engineered nanoplatform (Au NRs/Cur/UCNPs@PBE) is designed by loading curcumin (Cur, photosensitizer) on gold nanarods (Au NRs) to build PDT/PTT therapy system, which was encapsulated outside with upconversion nanoparticles (UCNPs) and then modified with phenylboronic double ester (PBE). The pH and ROS-responsive feature made Au NRs/Cur/UCNPs@PBE provide a fundamental structural evolution and improve the specificity and intracellular accumulation to tumors. Au NRs/Cur/UCNPs@PBE exhibited significant PDT and PTT efficiency against two type melanoma cells due to upconversion nanoparticles and Au NRs induced by an 808 nm laser. Notably, the platform can mainly activate apoptosis and partial ferroptosis to achieve the synergistic PDT/PTT, furthermore, the integrated PDT with PTT using Au NRs/Cur/UCNPs@PBE showcased a great antitumor efficacy in vivo superior to the other alone treatment. Our findings highlight that this intelligent nanoagents for synergistic phototherapy facilitate enhanced fighting melanoma and provide a promising strategy for melanoma theranostics.

Systematic Review of Cancer Targeting by Nanoparticles Revealed a Global Association between Accumulation in Tumors and Spleen

Active targeting of nanoparticles toward tumors is one of the most rapidly developing topics in nanomedicine. Typically, this strategy involves the addition of cancer-targeting biomolecules to nanoparticles, and studies on this topic have mainly focused on the localization of such formulations in tumors. Here, the analysis of the factors determining efficient nanoparticle targeting and therapy, various parameters such as types of targeting molecules, nanoparticle type, size, zeta potential, dose, and the circulation time are given. In addition, the important aspects such as how active targeting of nanoparticles alters biodistribution and how non-specific organ uptake influences tumor accumulation of the targeted nanoformulations are discussed. The analysis reveals that an increase in tumor accumulation of targeted nanoparticles is accompanied by a decrease in their uptake by the spleen. There is no association between targeting-induced changes of nanoparticle concentrations in tumors and other organs. The correlation between uptake in tumors and depletion in the spleen is significant for mice with intact immune systems in contrast to nude mice. Noticeably, modulation of splenic and tumor accumulation depends on the targeting molecules and nanoparticle type. The median survival increases with the targeting-induced nanoparticle accumulation in tumors; moreover, combinatorial targeting of nanoparticle drugs demonstrates higher treatment efficiencies. Results of the comprehensive analysis show optimal strategies to enhance the efficiency of actively targeted nanoparticle-based medicines.

Concurrent impairment of nucleus and mitochondria for synergistic inhibition of cancer metastasis

Cancer metastasis, which increases the mortality in a short period of time, has been considered as the main challenge in tumor treatment. However, tumor growth suppression also should not be ignored in cancer metastasis treatment. Recently, accumulating evidences have suggested that mitochondria play an important role in mitigating caner metastasis. Nucleus, as the repository of genetic information, plays a key role in cell proliferation. However, it remains elusive that the concurrent impairment of nucleus and mitochondria may achieve better anti-tumor and anti-metastatic effects. Here, we designed a mitochondria-penetrating peptide modified doxorubicin (MPP-Dox) loaded N-(2-hydroxypropyl) methacrylamide (HPMA) copolymer conjugates (PM), as well as a nuclear accumulating HPMA copolymer Dox conjugates (PN) by the nuclear tendency of Dox. After co-delivering the two copolymers (abbreviation for PMN), PM promoted cell apoptosis and inhibited tumor metastasis by damaging mitochondria, whereas PN suppressed cell proliferation and promoted apoptosis by destroying nucleus. Importantly, PM and PN complemented each other as expected. The mitochondrial dysfunction and tumor metastasis inhibition of PM was improved by PN, while cell proliferation suppression and apoptosis by nucleus destroying of PN was enhanced by PM. As a result, tumor growth of breast cancer 4T1 cells in vivo was significantly restrained and lung metastasis was potently decreased and almost eradicated, fully reflecting the advantages of organelle targeting combination therapy. As a consequence, our work showed that concurrent impairment of nucleus and mitochondria was feasible and beneficial to metastatic cancer treatment.

Precise Targeting Therapy of Orthotopic Gastric Carcinoma by siRNA and Chemotherapeutic Drug Codelivered in pH-Sensitive Nano Platform

Gastric cancer is one of the most common malignant tumors, which remains as an obstacle to human health. Nowadays, targeted nanoparticles to gastric tumor tissues, provide new strategy for improved therapy but still remain challenging. The major hurdle of targeted therapeutic nanoparticles comes from the limited enrichment and poor selectivity of therapeutic agents in in situ tumor. Herein, a pH-sensitive targeted nano platform coloaded As₂ O₃ and human epidermal growth factor receptor-2 (HER2)-siRNA (AH RNPs) is developed to achieve targeting therapy in orthotopic gastric carcinoma. AH RNPs can effectively prevent the degradation of siRNA and overcome the poor solubility of As₂ O₃ . In vitro studies show that AH RNPs could achieve synergistic inhibition of growth and metastasis on SGC7901 cells. Surprisingly, AH RNPs not only target gastric subcutaneous tumor, but also target in situ tumor, and express loaded genes in in situ tumor. Moreover, AH RNPs show excellent antitumor effect in orthotopic gastric tumor model and the anticancer mechanism is related about inhibiting the activation of ERK signal and downregulating the expression of cxc chemokine receptor 4 (CXCR4), HER2, MMP2, and MMP9 protein. This study provides a multi-functional vector for precise targeting therapy of gastric cancer, which may serve as a potential clinical application for future gastric cancer.

Enhanced anti-metastatic therapy with down-regulation of heparinase expression by ROS-responsive micellar nanoparticles

Metastasis is a major sign of malignant tumors which plays a vital role in cancer-related death. Suppressing metastasis is an important way to improve the survival rate of cancer patients. Herein, multifunctional PEG-LAM-PPS nanoparticles (nPLPs) are fabricated as both nanocarriers and anti-metastatic agents for tumor treatment. In this system, laminarin sulfate (LAM) suppresses metastasis by reducing heparinase and protecting the extracellular matrix; the ROS-sensitive polypropylene sulfide (PPS) improves the release of the loaded drug in the tumor microenvironment. This is the first time that laminarin sulfate has been used as a carrier to inhibit the expression of heparinase and treat melanoma lung metastasis. The blank nanoparticles are excellently safe and showed high anti-metastatic efficacy in melanoma lung metastatic mouse models, reducing metastatic nodules by 60%. They significantly improved the anti-tumor efficacy of the loaded drug doxorubicin, provided ∼33% further reduction of the tumor volume and 50% further reduction of the metastatic nodule number compared with free doxorubicin. Thus, these simple and versatile micellar nanoparticles composed of biocompatible materials offer a promising vehicle for treating invasive solid tumors and metastases.

Nitric oxide-releasing micelles with intelligent targeting for enhanced anti-tumor effect of cisplatin in hypoxia

Background

Hypoxic tumor microenvironment (TME) promotes tumor metastasis and drug resistance, leading to low efficiency of cancer chemotherapy. The development of targeted agents or multi-target therapies regulating hypoxic microenvironment is an important approach to overcome drug resistance and metastasis.

Methods

In this study, chitosan oligosaccharide (COS)-coated and sialic acid (SA) receptor-targeted nano-micelles were prepared using film dispersion method to co-deliver cisplatin (CDDP) and nitric oxide (NO) (denoted as CTP/CDDP). In addition, we explored the mechanisms by which NO reversed CDDP resistance as well as enhanced anti-metastatic efficacy in hypoxic cancer cells.

Results

Because of the different affinities of COS and SA to phenylboronic acid (PBA) under different pH regimes, CTP/CDDP micelles with intelligent targeting property increased cellular uptake of CDDP and enhanced cytotoxicity to tumors, but reduced systemic toxicity to normal organs or tissues. In addition, CTP/CDDP showed stimulus-responsive release in TME. In terms of anti-tumor mechanism, CTP/CDDP reduced CDDP efflux and inhibited epithelial-mesenchymal transition (EMT) process of tumor by down-regulating hypoxia-inducible factor-1α (HIF-1α), glutathione (GSH), multidrug resistance-associated protein 2 (MRP2) and matrix metalloproteinase 9 (MMP9) expression, thus reversing drug resistance and metastasis of hypoxic tumor cells.

Conclusions

The designed micelles significantly enhanced anti-tumor effects both in vitro and in vivo. These results suggested that CTP/CDDP represented a promising strategy to treat resistance and metastatic tumors.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-00989-z.

PEGylated phospholipid micelles containing D-α-tocopheryl succinate as multifunctional nanocarriers for enhancing the antitumor efficacy of doxorubicin

The aim of this investigation is to clarify the effect of D-α-tocopheryl succinate (vitamin E succinate, VES) and distearoylphosphatidyl ethanolamine-poly(ethylene glycol) (DSPE-PEG) on the encapsulation and controlled release of doxorubicin (DOX) in nano-assemblies and their consequences on the anti-tumor efficacy of DOX. DOX molecules were successfully loaded into the hybrid micelles with VES and DSPE-PEG (VDPM) via thin-film hydration method, exhibiting a small hydrodynamic particle size (~30 nm) and a weak negative zeta potential of around -5 mv. The obtained DOX-loaded VDPM2 displayed retarded DOX release at pH of 7.4, while substantially accelerated drug release at acidic pH of 5.0. Furthermore, the DOX-loaded VDPM2 exhibited substantially slower drug release rate at pH 7.4 compared with the drug-loaded VDPM1 or DPM preparation, benefiting for decreasing the premature DOX release during blood circulation. In vitro cell experiment indicated that DOX-loaded micelles (DPM, VDPM1 and VDPM2) improved the cellular uptake of DOX in 4T1 and MDA-MB-231 cells. The existence of VES component in the structure of DOX-loaded micelles had no obvious influence on the subcellular distribution of the encapsulated DOX molecules. Furthermore, the DOX-loaded VDPM2 exhibited more pronounced cytotoxicity to 4T1 and MDA-MB-231 cancerous cells compared with DOX-loaded DPM and free DOX solution. The hybrid nanocarriers including VES and DSPE-PEG selectively induced intracellular ROS accumulation and increased level of cytoplasmic calcium ion in cancerous cells by interacting with mitochondria and endoplasmic reticulum, bringing about the improved cytotoxicity of DOX. In vivo antitumor efficacy investigation of DOX-loaded VDPM2 against 4T1 xenograft-bearing mice displayed satisfied therapeutic activity with negligible systemic toxicity, as evidenced by the histological analysis and change of body weight. The proposed DOX-loaded VDPM preparation, as a mulifunctional chemotherapeutic nanomedicine system, holds great potential and bright prospect for clinical tumor therapy.

Emerging nanomedicine-based therapeutics for hematogenous metastatic cascade inhibition: Interfering with the crosstalk between "seed and soil"

Despite considerable progresses in cancer treatment, tumor metastasis is still a thorny issue, which leads to majority of cancer-related deaths. In hematogenous metastasis, the concept of “seed and soil” suggests that the crosstalk between cancer cells (seeds) and premetastatic niche (soil) facilitates tumor metastasis. Considerable efforts have been dedicated to inhibit the tumor metastatic cascade, which is a highly complicated process involving various pathways and biological events. Nonetheless, satisfactory therapeutic outcomes are rarely observed, since it is a great challenge to thwart this multi-phase process. Recent advances in nanotechnology-based drug delivery systems have shown great potential in the field of anti-metastasis, especially compared with conventional treatment methods, which are limited by serious side effects and poor efficacy. In this review, we summarized various factors involved in each phase of the metastatic cascade ranging from the metastasis initiation to colonization. Then we reviewed current approaches of targeting these factors to stifle the metastatic cascade, including modulating primary tumor microenvironment, targeting circulating tumor cells, regulating premetastatic niche and eliminating established metastasis. Additionally, we highlighted the multi-phase targeted drug delivery systems, which hold a better chance to inhibit metastasis. Besides, we demonstrated the limitation and future perspectives of nanomedicine-based anti-metastasis strategies.

Superior in vitro anticancer effect of biomimetic paclitaxel and triptolide co-delivery system in gastric cancer

As a well-known anticancer drug, paclitaxel (PTX), a first-line chemotherapeutic agent, remains unsatisfactory for gastric cancer therapy. It is reported that triptolide (TPL) could enhance the anti-gastric cancer effect of PTX. Considering the poor solubility of both drugs, we developed a red blood cell membrane-biomimetic nanosystem, an emerging tool in drug delivery, to co-load paclitaxel and triptolide (red blood cell membrane coated PTX and TPL co-loaded poly(lactic-co-glycolic acid) [PLGA] nanoparticles, RP(P/T)). The successful preparation was confirmed in terms of particle size, morphology, and surface markers assays. This biomimetic system could prolong circulation and escape immune surveillance. And these properties were verified by stability, in vitro drug release, and cellular uptake assays. Moreover, the MTT and colony formation assays demonstrated the superior anti-proliferation effect of the RP(P/T) to free drugs. The enhanced antitumor effects of RP(P/T) on migration and invasion were also evaluated by wound-healing and transwell assays. Overall, the bionic co-delivery nanoplatform with improved efficacy in vitro is a promising therapy for gastric cancer.

Multi-Arm PEG/Peptidomimetic Conjugate Inhibitors of DR6/APP Interaction Block Hematogenous Tumor Cell Extravasation

The binding of amyloid precursor protein (APP) expressed on tumor cells to death receptor 6 (DR6) could initiate the necroptosis pathway, which leads to necroptotic cell death of vascular endothelial cells (ECs) and results in tumor cells (TCs) extravasation and metastasis. This study reports the first inhibitor of DR6/APP interaction as a novel class of anti-hematogenous metastatic agent. By rationally utilizing three combined strategies including selection based on phage display library, d-retro-inverso modification, and multiple conjugation of screened peptidomimetic with 4-arm PEG, the polymer-peptidomimetic conjugate PEG-tAHP-DRI (tetra-(D-retro-inverso isomer of AHP-12) substitued 4-arm PEG5k ) is obtained as the most promising agent with the strongest binding potency (KD  = 51.12 × 10-9  m) and excellent pharmacokinetic properties. Importantly, PEG-tAHP-DRI provides efficient protection against TC-induced ECs necroptosis both in vitro and in vivo. Moreover, this ligand exhibits prominent anti-hematogenous metastatic activity in serval different metastatic mouse models (B16F10, 4T1, CT26, and spontaneous lung metastasis of 4T1 orthotopic tumor model) and displays no apparent detrimental effects in preliminary safety evaluation. Collectively, this study demonstrates the feasibility of exploiting DR6/APP interaction to regulate hematogenous tumor cells transendothelial migration and provides PEG-tAHP-DRI as a novel and promising inhibitor of DR6/APP interaction for developments of anti-hematogenous metastatic therapies.

Phenylboronic acid modified nanoparticles simultaneously target pancreatic cancer and its metastasis and alleviate immunosuppression

Pancreatic ductal adenocarcinoma is one of the most lethal malignant tumors, its drug resistance, immunosuppression and metastasis makes the traditional chemotherapy and immunotherapy inefficient. Here we confirmed a 3-aminophenylboronic acid-modified low molecular weight heparin-D-α-tocopheryl succinate micellar nanoparticle (PBA-LMWH-TOS NP, PLT NP) could inhibit orthotopic pancreatic tumor and its spontaneous metastases. The small particle size and high affinity of PBA to sialic acid residue (SA) made PLT/PTX NPs significantly targeted and accumulated in both pancreatic tumor tissues and metastases. The immunosuppressive microenvironment of pancreatic tumor was most caused by the infiltration of immunosuppressive cells, mainly myeloid-derived suppressor cells (MDSCs). We first reported that P-selectin glycoprotein ligand-1 (PSGL-1) was expressed on the surfaces of MDSCs in pancreatic tumor tissues. Meanwhile, we found that LMWH could inhibit the early stage of adhesion cascade between vascular endothelial cells (VECs) and MDSCs by interfering with P-selectin/PSGL-1 binding, thus inhibiting MDSC recruitment to pancreatic tumor tissues. The therapeutic results indicated that PLT/PTX NPs could significantly improve the immune microenvironment of pancreatic tumor and inhibit spontaneous metastases. This nanosystem provides a new immune microenvironment regulation mechanism based on carrier materials in pancreatic tumor, and has high clinical application potential.

Shield and sword nano-soldiers ameliorate rheumatoid arthritis by multi-stage manipulation of neutrophils

Rheumatoid arthritis (RA) is characterized by the outbreak of inflammation. Neutrophils, the main culprit of the outbreak of inflammation, are the first inflammatory cells to be recruited to inflamed joints and facilitate the recruitment of themselves by stimulating the release of chemokines. Here, based on neutrophils, a novel anti-inflammatory "shield and sword soldiers" strategy is established with LMWH-TOS nanoparticles (LT NPs). The hydrophilic fragment low molecular weight heparin (LMWH) acts as a shield which block the transvascular movement of neutrophils through inhibiting the adhesion cascade by binding to P-selectin on inflamed endothelium. Synergistically, MMP-9, which is secreted by the recruited neutrophils and degrade the main component of articular cartilage, is reduced by the hydrophobic fragment d-α-tocopheryl succinate (TOS), functioning as a sword. In collagen-induced arthritis (CIA) mouse model, LT NPs show significant targeting effect, and exhibit prominent therapeutic efficacy after enveloping the first-line anti-RA drug methotrexate. Our work proves that the multi-stage manipulation of neutrophils is feasible and effective, providing a new concept for RA treatment.

Spatiotemporally programmable cascade hybridization of hairpin DNA in polymeric nanoframework for precise siRNA delivery

DNA nanostructures have been demonstrated as promising carriers for gene delivery. In the carrier design, spatiotemporally programmable assembly of DNA under nanoconfinement is important but has proven highly challenging due to the complexity-scalability-error of DNA. Herein, a DNA nanotechnology-based strategy via the cascade hybridization chain reaction (HCR) of DNA hairpins in polymeric nanoframework has been developed to achieve spatiotemporally programmable assembly of DNA under nanoconfinement for precise siRNA delivery. The nanoframework is prepared via precipitation polymerization with Acrydite-DNA as cross-linker. The potential energy stored in the loops of DNA hairpins can overcome the steric effect in the nanoframework, which can help initiate cascade HCR of DNA hairpins and achieve efficient siRNA loading. The designer tethering sequence between DNA and RNA guarantees a triphosadenine triggered siRNA release specifically in cellular cytoplasm. Nanoframework provides stability and ease of functionalization, which helps address the complexity-scalability-error of DNA. It is exemplified that the phenylboronate installation on nanoframework enhanced cellular uptake and smoothed the lysosomal escape. Cellular results show that the siRNA loaded nanoframework down-regulated the levels of relevant mRNA and protein. In vivo experiments show significant therapeutic efficacy of using siPLK1 loaded nanoframework to suppress tumor growth.

Nanocarrier-Based Drug Delivery for Melanoma Therapeutics

Melanoma, as a tumor cell derived from melanocyte transformation, has the characteristics of malignant proliferation, high metastasis, rapid recurrence, and a low survival rate. Traditional therapy has many shortcomings, including drug side effects and poor patient compliance, and so on. Therefore, the development of an effective treatment is necessary. Currently, nanotechnologies are a promising oncology treatment strategy because of their ability to effectively deliver drugs and other bioactive molecules to targeted tissues with low toxicity, thereby improving the clinical efficacy of cancer therapy. In this review, the application of nanotechnology in the treatment of melanoma is reviewed and discussed. First, the pathogenesis and molecular targets of melanoma are elucidated, and the current clinical treatment strategies and deficiencies of melanoma are then introduced. Following this, we discuss the main features of developing efficient nanosystems and introduce the latest reports in the literature on nanoparticles for the treatment of melanoma. Subsequently, we review and discuss the application of nanoparticles in chemotherapeutic agents, immunotherapy, mRNA vaccines, and photothermal therapy, as well as the potential of nanotechnology in the early diagnosis of melanoma.

From cow manure to bioactive carbon dots: a light-up probe for bioimaging investigations, glucose detection and potential immunotherapy agent for melanoma skin cancer

Bioactive carbon dots (C-dots) with ca. 4 nm were successfully produced with singular photophysical properties, low-toxicity and interesting immunological response. The optical properties of the C-dots were investigated and the "light-up" behaviour enabled them to be explored in glucose detection and bioimaging experiments (mitochondrial selective probe). C-dots were not selective to the tumour region and several fluorescent spots were visualized spread on animal bodies. The histology investigations showed that cancer-bearing mice treated with C-dots presented a large number of regions with necrosis and inflammatory infiltrates, which were not identified for cancer-bearing mice without the treatment. These results suggested that C-dots have the potential to be explored as an immune therapy agent for melanoma skin cancer.

Design of DOX-GNRs-PNIPAM@PEG-PLA Micelle With Temperature and Light Dual-Function for Potent Melanoma Therapy

Objective: The aim of this study was to construct light and temperature dual-sensitive micellar carriers loaded with doxorubicin (DOX) and gold nanorods (DOX-GNRs-PNIPAM@PEG-PLA, DAPP) for melanoma therapy. Methods: The DAPP self-assembled using fine-tuned physicochemical properties in water. The DAPP structure, temperature- and photo-sensitivity, drug-release, in-vitro serum stability, and cytotoxicity against melanoma B16F10 cells were evaluated in detail. The corresponding in-vitro and in-vivo therapeutic mechanisms were then evaluated using a B16F10-melanoma bearing BALB/c nude mouse model (B16F10). Results: The light and temperature sensitive micellar drug-delivery system assembled from block copolymer and gold nanorods exhibited a narrow particle size and size distribution, good biocompatibility, well-designed photo-temperature conversion, controlled drug release, and high serum stability. Compared with the free DOX- and PBS-treated groups, the cell endocytosis-mediated cytotoxicity and intra-tumor accumulation of DAPP was markedly enhanced by the NIR-light exposure and induced potent in-vivo tumor inhibitory activity. Conclusion: The design of DAPP, a dual-functional micellar drug-delivery system with temperature- and light-sensitive properties, offers a new strategy for skin-cancer therapy with a potent therapeutic index.

Combination of mitochondria targeting doxorubicin with Bcl-2 function-converting peptide NuBCP-9 for synergistic breast cancer metastasis inhibition

Distant organ metastasis is the main cause of death in breast cancer patients. Evidences have shown that mitochondria also play a crucial role in tumor metastasis, except for as apoptosis center. However, the treatment of tumor growth and metastasis was reported to be limited by mitochondria-associated protein Bcl-2, which are gatekeepers of apoptosis and are found to reside in mitochondria mainly. Herein, we designed a mitochondria-targeting doxorubicin delivery system as well as a mitochondrial distributed Bcl-2 function-converting peptide NuBCP-9 delivery system, which are both based on N-(2-hydroxypropyl)methacrylamide copolymers, to achieve a synergistic effect on tumor regression and metastasis inhibition by combination therapy. After mitochondria were damaged by mitochondria-targeting peptide-modified doxorubicin, apoptosis was effectively enhanced by mitochondrial specifically distributed NuBCP-9 peptides, which converted Bcl-2 function from anti-apoptotic to pro-apoptotic and paved the way for the development of mitochondrial impairment. The combination treatment exhibited significant damage to mitochondria, including excess reactive oxygen species (ROS), the permeabilization of mitochondrial outer membrane (MOMP), and apoptosis initiation on 4T1 breast cancer cells. Meanwhile, besides enhanced tumor growth suppression, the combination treatment also improved the inhibition of 4T1 breast cancer metastasis both in vitro and in vivo. By increasing the expression of cytochrome C and decreasing the expression of Bcl-2, metal matrix protease-9 (MMP-9) as well as vascular endothelial growth factor (VEGF), the combination treatment successfully decreased 84% lung metastasis. Overall, our work provided a promising strategy for metastatic cancer treatment through mitochondria-targeting anti-cancer drug delivery and combination with mitochondrial distributed Bcl-2 function-converting peptide.

Enhanced stability and efficacy of GEM-TOS prodrug by co-assembly with antimetastatic shell LMWH-TOS

Chemotherapy agents have been widely used for cancer treatment, while the insolubility, instability and toxicity seriously restrict their efficacy. Thus, prodrug strategy was devised. Since some prodrugs are still with poor solubility or stability, a synergy strategy is needed to enhance their efficacy. Gemcitabine (GEM) is a prescribed anticancer drug, however, the rapid clearance, growing resistance and serious side effects limit its clinical efficacy. Conjugating GEM with d-α-tocopherol succinate (TOS) is an effective solution, while the GEM-TOS (GT) is unstable in aqueous solution. d-α-Tocopherol polyethylene glycol succinate (TPGS) has been used to enhance the stability, but GT stabilized by TPGS (GTT) has limited effect on tumor metastases. Tumor metastases lead to high mortality in patients suffering from cancers. In order to further achieve antimetastatic effect, an amphiphilic polymer (LT) was synthesized by connecting low-molecular-weight heparin (LMWH) with TOS, and eventually obtained desired self-delivery micellar NPs (GLT) by co-assembly GT with LT. The GLT not only possessed excellent stability, but also inhibited the metastases by acting on different phases of the metastatic cascade. The hydrophobic TOS inhibited the secretion of matrix metalloproteinase-9 (MMP-9), the hydrophilic LMWH inhibited the interaction between tumor cells and platelets. As a result, GLT reduced tumor cells entering the blood and implanting at the distant organs, leading to a much more excellent inhibitory effect on the lung metastasis than GEM and GTT.

Acid-labile polysaccharide prodrug via lapatinib-sensitizing effect substantially prevented metastasis and postoperative recurrence of triple-negative breast cancer

Surgical resection and chemotherapy are routinely performed for triple-negative breast cancer (TNBC) because it is insensitive to endocrine therapy and molecular targeted therapy. Here, the optimal surface charge (-28 mV) and particle size (51 nm) enabled the acid-labile hyaluronic acid pullulan prodrug (HPP)-doxorubicin (Dox)/lapatinib (Lap) conjugate to circulate in the blood for a lengthy period of time and enhance the electron paramagnetic resonance effect, while the targeted molecule hyaluronic acid accelerated CD44 receptor-mediated 4T1 cell internalization. The inefficient anti-proliferation capability of Lap increased more than 10-fold after sensitization of Dox to metastatic 4T1 cells, while cellular uptake significantly increased, and cell viability dramatically decreased to nearly 20% of the free Dox group. Furthermore, HPP-Dox/Lap more effectively inhibited lateral mobility, vertical migration, and invasion ability of 4T1 cells. The ex vivo biodistribution of representative Dox indicated that Lap obviously facilitated the intratumoral infiltration and accumulation. The in vivo research revealed that there were overwhelming advantages in using HPP-Dox/Lap to inhibit tumor growth, progression, and lung metastasis even at a low dosage (1 mg kg-1), and it decreased postoperative recurrence and pulmonary metastatic nodules. Because of the excellent biosafety and visible therapeutic effect on the 4T1 metastasis and recurrence model, there is great potential value for HPP-Dox/Lap to be used to treat metastatic TNBC.

Mechanotactic Activation of TGF-β by PEDOT Artificial Microenvironments Triggers Epithelial to Mesenchymal Transition

Epithelial to mesenchymal transition (EMT) is integral for cells to acquire metastatic properties, and ample evidence links it to bioorganic framework of the tumor microenvironment (TME). Hydroxymethyl-functionalized 3,4-ethylenedioxythiophene polymer (PEDOT-OH) enables construction of diverse nanotopography size and morphologies and is therefore exploited to engineer organic artificial microenvironments bearing nanodots from 300 to 1000 nm in diameter to understand spatiotemporal EMT regulation by biophysical components of the TME. MCF-7 breast cancer cells are cultured on these artificial microenvironments, and temporal regulation of cellular morphology and EMT markers is investigated. The results show that upon physical stimulation, cells on 300 nm artificial microenvironments advance to EMT and display a decreased extracellular matrix (ECM) protein secretion. In contrast, cells on 500 nm artificial microenvironments are trapped in EMT-imbalance. Interestingly, cells on 1000 nm artificial microenvironments resemble those on control surfaces. Upon further investigation, it is found that EMT induction is triggered via transforming growth factor β (TGF-β) and ECM cleaving protein, matrix metalloproteinease-9. Immunostaining EMT proteins highlighted that EMT induction is achieved through attenuation of cell-cell and cell-microenvironment adhesions. The physical stimulation-induced TGF-β perturbation can have a profound impact on the understanding of tumor-promoting signaling cascades originated by cellular microenvironment.

Self-Delivery Micellar Nanoparticles Prevent Premetastatic Niche Formation by Interfering with the Early Recruitment and Vascular Destruction of Granulocytic Myeloid-Derived Suppressor Cells

Distal metastases of tumors result from the interaction between "seeds" (circulating tumor cells, CTCs) and "soil" (premetastatic niche, PMN). Various strategies focus on CTC inhibition, but only a few strategies inhibit PMN formation. The main predisposition of PMN formation in melanoma lies in the pulmonary recruitment of granulocytic myeloid-derived suppressor cells (G-MDSCs, CD11b⁺Ly6G⁺ cells) induced by tumors, which increase vascular permeability by secreting matrix metalloproteinase-9 (MMP-9) and result in immunosuppression by secreting interleukin-10 (IL-10) in premetastatic lungs. Here, a micellar hypotoxic low molecular weight heparin-tocopherol succinate nanoparticle (LMWH-TOS nanoparticle, LT NP) was established and investigated for its influence on PMN formation in this study. We first demonstrated that the hydrophilic segment LMWH in LT NPs can inhibit early pulmonary recruitment of G-MDSCs through interrupting their extravasation by inhibiting P-selectin/PSGL-1-mediated adhesion between vascular endothelial cells and G-MDSCs. In addition, the hydrophobic segment (TOS) in LT NPs significantly inhibited the expression of MMP-9 in G-MDSCs. As a result, the drug-free nanoparticles could maintain the normal microenvironment of lungs, thus effectively inhibiting implantation and colonization of CTCs. Further, phenylboronic acid (PBA)-modified and doxorubicin/immunopotentiator α-galactosylceramide (αGC)-coloaded nanoparticles (PLT/DOX/αGC NPs) were exploited. PBA modification achieved targeted chemotherapy by binding to overexpressed sialic acid residues on the tumor cell surface. This nanosystem effectively inhibited the postoperative metastasis and tumor recurrence simultaneously. Our work provides a proof of concept that the prevention of PMN formation through interfering G-MDSCs with self-delivery nanosystems is a safe and effective antimetastasis strategy.

Construction of Dually Responsive Nanotransformers with Nanosphere-Nanofiber-Nanosphere Transition for Overcoming the Size Paradox of Anticancer Nanodrugs

Tumor microenvironment (TME)-responsive nanosystems represent a category of intelligent nanomaterials for precise anticancer drug delivery. Herein, we report a smart size-/morphology-switchable nanodrug that can respond to the acidic TME and near-infrared (NIR) laser irradiation for effective tumor ablation and tumor metastasis inhibition. The nanoagent is physically assembled by a cytolytic peptide, melittin (MEL), an NIR-absorbing molecule, cypate, and a tumor-targeting polymer, hyaluronic acid (HA). At pH 7.4, the as-formed MEL/Cypate@HA complexes are negatively charged nanospheres (∼50 nm), which are suitable for long-term systemic circulation. When these nanospheres actively target tumors, the weakly acidic TME triggers an in situ transformation of the nanospheres to net-like nanofibers. Compared with the nanospheres, the nanofibers not only exhibit an inhibitory effect on tumor cell mobility but also significantly prolong the retention time of MEL/Cypate@HA in tumor tissues for MEL-based chemotherapy. Moreover, the nanofibers can be photodegraded into small nanospheres (∼25 nm) by NIR laser irradiation during cypate-mediated photothermal therapy, which enables deep tumor penetration of the loaded MEL and thus achieves effective tumor eradication. This work provides a facile strategy for converting naturally occurring therapeutic peptides into a TME-responsive drug delivery system and may inspire the development of nanomaterials with changeable structures for therapeutic purposes.

Multifunctional polymeric micelle-based chemo-immunotherapy with immune checkpoint blockade for efficient treatment of orthotopic and metastatic breast cancer

Immunotherapy has become a highly promising paradigm for cancer treatment. Herein, a chemo-immunotherapy was developed by encapsulating chemotherapeutic drug doxorubicin (DOX) and Toll-like receptor 7 agonist imiquimod (IMQ) in low molecular weight heparin (LMWH)-d-α-tocopheryl succinate (TOS) micelles (LT). In this process, LMWH and TOS were conjugated by ester bond and they were not only served as the hydrophilic and hydrophobic segments of the carrier, but also exhibited strong anti-metastasis effect. The direct killing of tumor cells mediated by DOX-loaded micelles (LT-DOX) generated tumor-associated antigens, initiating tumor-specific immune responses in combination with IMQ-loaded micelles (LT-IMQ). Furthermore, the blockade of immune checkpoint with programmed cell death ligand 1 (PD-L1) antibody further elevated the immune responses by up-regulating the maturation of DCs as well as the ratios of CD8+ CTLs/Treg and CD4+ Teff/Treg. Therefore, such a multifunctional strategy exhibited great potential for inhibiting the growth of orthotopic and metastatic breast cancer.