Celastrol nanoemulsion induces immunogenicity and downregulates PD-L1 to boost abscopal effect in melanoma therapy

Plant-derived natural compounds: A new frontier in inducing immunogenic cell death for cancer treatment

Immunogenic cell death (ICD) can activate adaptive immune response in the host with normal immune system. Some synthetic chemotherapeutic drugs and natural compounds have shown promising results in cancer treatment by triggering the release of damage-associated molecules (DAMPs) to trigger ICD. However, most chemotherapeutic drugs exhibit non-selective cytotoxicity and may also induce and promote metastasis, thereby significantly reducing their clinical efficacy. Among the natural compounds that can induce ICD, plant-derived compounds account for the largest proportion, which are of increasing value in the treatment of cancer. Understanding which plant-derived natural compounds can induce ICD and how they induce ICD is crucial for developing strategies to improve chemotherapy outcomes. In this review, we focus on the recent findings regarding plant-derived natural compounds that induce ICD according to the classification of flavonoids, alkaloids, glycosides, terpenoids and discuss the potential mechanisms including endoplasmic reticulum (ER) stress, DNA damage, apoptosis, necroptosis autophagy, ferroptosis. In addition, plant-derived natural compounds that can enhance the ICD induction ability of conventional therapies for cancer treatment is also elaborated. The rational use of plant-derived natural compounds to induce ICD is helpful for the development of new cancer treatment methods.

Polydopamine-Based Nanoparticles for Synergistic Chemotherapy of Prostate Cancer

Introduction

Immune regulatory small molecule JQ1 can block its downstream effector PD-L1 pathway and effectively reverse the PD-L1 upregulation induced by doxorubicin (DOX). So the synergistic administration of chemotherapeutic drug DOX and JQ1 is expected to increase the sensitivity of tumors to immune checkpoint therapy and jointly enhance the body's own immunity, thus effectively killing tumor cells. Therefore, a drug delivery system loaded with DOX and JQ1 was devised in this study.

Methods

Polydopamine nanoparticles (PDA NPs) were synthesized through spontaneous polymerization. Under appropriate pH conditions, DOX and JQ1 were loaded onto the surface of PDA NPs, and the release of DOX and JQ1 were measured using UV-Vis or high performance liquid chromatography (HPLC). The mechanism of fabricated nanocomplex in vitro was investigated by cell uptake experiment, cell viability assays, apoptosis assays, and Western blot analysis. Finally, the tumor-bearing mouse model was used to evaluate the tumor-inhibiting efficacy and the biosafety in vivo.

Results

JQ1 and DOX were successfully loaded onto PDA NPs. PDA-DOX/JQ1 NPs inhibited the growth of prostate cancer cells, reduced the expression of apoptosis related proteins and induced apoptosis in vitro. The in vivo biodistribution indicated that PDA-DOX/JQ1 NPs could accumulated at the tumor sites through the EPR effect. In tumor-bearing mice, JQ1 delivered with PDA-DOX/JQ1 NPs reduced PD-L1 expression at tumor sites, generating significant tumor suppression. Furthermore, PDA-DOX/JQ1 NPs could reduce the side effects, and produce good synergistic treatment effect in vivo.

Conclusion

We have successfully prepared a multifunctional platform for synergistic prostate cancer therapy.

Nanoparticle-mediated celastrol ER targeting delivery amplify immunogenic cell death in melanoma

INTRODUCTION

Chemoimmunotherapy, which benefits from the combination of chemotherapy and immunotherapy, has emerged as a promising strategy in cancer treatment. However, effectively inducing a robust immune response remains challenging due to the limited responsiveness across patients. Endoplasmic reticulum (ER) stress is essential for activating intracellular signaling pathways associated with immunogenic cell death (ICD), targeting drugs to ER might enhance ER stress and improve ICD-related immunotherapy.

OBJECTIVES

To improve the immune response of Chemoimmunotherapy.

METHODS

ER targeting nanoparticles TSE-CEL/NP were constructed to enhance immunogenic cancer cell death. Flow cytometry, confocal microscope, TEM and immunofluorescence were used to evaluate the ER targeting effect and immunogenic tumor cell death in vitro on B16F10 tumor cells. Unilateral and bilateral tumor models were constructed to investigate the efficacy of anti-tumor and immunotherapy in vivo. Lung metastasis B16F10 melanoma tumor-bearing mice were used to assess the anti-metastasis efficacy.

RESULTS

TSE-CEL/NP could specially accumulate in ER, thereby induce ER stress. High ER stress trigger the exposure of CRT, the extracellular release of HMGB1 and ATP. These danger signals subsequently promote the recruitment and maturation of dendritic cells (DCs), which in turn increase the proliferation of cytotoxic T lymphocytes (CD8+ T cells), ultimately resulted in an improved immunotherapy efficacy against melanoma. Invivo experiments showed that TSE-CEL/NP exhibits excellent antitumor efficacy and triggers a strong immune response.

CONCLUSION

Our findings demonstrated that celastrol ER targeting delivery could amplify immunogenic cell death in melanoma, which provide experimental basis for melanoma immunotherapy.

Immunogenic cell death inducers for cancer therapy: An emerging focus on natural products

BACKGROUND

Immunogenic cell death (ICD) is a specific form of regulated cell death induced by a variety of stressors. During ICD, the dying cancer cells release damage-associated molecular patterns (DAMPs), which promote dendritic cell maturation and tumor antigen presentation, subsequently triggering a T-cell-mediated anti-tumor immune response. In recent years, a growing number of studies have demonstrated the potential of natural products to induce ICD and enhance tumor cell immunogenicity. Moreover, there is an increasing interest in identifying new ICD inducers from natural products.

PURPOSE

This study aimed to emphasize the potential of natural products and their derivatives as ICD inducers to promote research on using natural products in cancer therapy and provide ideas for future novel immunotherapies based on ICD induction.

METHOD

This review included a thorough search of the PubMed, Web of Science, Scopus, and Google Scholar databases to identify natural products with ICD-inducing capabilities. A comprehensive search for clinical trials on natural ICD inducers was also conducted using ClinicalTrials.gov, as well as the approved patents using the Espacenet and CNKI Patent Database.

RESULTS

Natural compounds that induce ICD can be categorized into several groups, such as polyphenols, flavonoids, terpenoids, and alkaloids. Natural products can induce the release of DAMPs by triggering endoplasmic reticulum stress, activation of autophagy-related pathways, and reactive oxygen species generation, etc. Ultimately, they activate anti-tumor immune response and improve the efficacy of cancer treatments.

CONCLUSION

A growing number of ICD inducers from natural products with promising anti-cancer potential have been identified. The detailed information presented in this review will contribute to the further development of natural ICD inducers and cancer treatment strategies based on ICD-induced responses.

Elucidation of Spatial Cooperativity in Chemo-Immunotherapy by a Sequential Dual-pH-Responsive Drug Delivery System

Combining immune checkpoint blockade with chemotherapy through nanotechnology is promising in terms of safety and efficacy. However, the distinct subcellular distribution of each ingredient's action site makes it challenging to acquire an optimal synergism. Herein, a dual-pH responsive hybrid polymeric micelle system, HNP(αPDL16.9, Dox5.3), is constructed as a proof-of-concept for the spatial cooperativity in chemo-immunotherapy. HNP retains the inherent pH-transition of each polymer, with stepwise disassembly under discrete pH thresholds. Within weakly acidic extracellular tumor environment, αPDL1 is first released to block the checkpoint on cell membranes. The remaining intact Doxorubicin-loaded micelle NP(Dox)5.3 displays significant tropism toward tumor cells and releases Dox upon lysosomal pH for efficient tumor immunogenic cell death without immune toxicity. This sequential-released pattern boosts DC activation and primes CD8+ T cells, leading to enhanced therapeutic performance than single agent or an inverse-ordered combination in multiple murine tumor models. Using HNP, the indispensable role of conventional type 1 DC (cDC1) is identified in chemo-immunotherapy. A co-signature of cDC1 and CD8 correlates with cancer patient survival after neoadjuvant Pembrolizumab plus chemotherapy in clinic. This study highlights spatial cooperativity of chemo- and immuno-agents in immunoregulation and provides insights into the rational design of drug combination for future nanotherapeutics development.

Celastrol inhibits mouse B16-F10 melanoma cell survival by regulating the PI3K/AKT/mTOR signaling pathway and repressing HIF-1α expression

OBJECTIVE

Melanoma, with its high degree of malignancy, stands as one of the most dangerous skin cancers and remains the primary cause of death from skin cancer. With studies demonstrating the potential of traditional Chinese medicine to intervene and treat melanoma, we turned our attention to celastrol. Celastrol is a triterpene compound extracted from the traditional Chinese medicine derived from Tripterygium wilfordii. Previous studies have shown that celastrol exerts inhibitory effects on various malignant tumors, including melanoma. Hence, our goal was to clarify the impact of celastrol on cell viability, apoptosis, and cell cycle progression by elucidating its effects on the PI3K/AKT/mTOR pathway.

METHODS

CCK-8 and wound healing assays were used to determine the effect of celastrol on the viability and migration of B16-F10 cells. Changes in cell apoptosis, cell cycle, reactive oxygen species (ROS), and mitochondrial membrane potential were detected by flow cytometry. PI3K/AKT/mTOR pathway proteins and HIF-α mRNA expression in B16-F10 cells were detected by western blotting and qPCR. Moreover, the addition of a PI3K activator demonstrated that celastrol could inhibit the function of B16-F10 cells via the PI3K/AKT/mTOR pathway.

RESULTS

Celastrol inhibited the viability and migration of B16-F10 cells. Through the inhibition of the PI3K/AKT/mTOR pathway down-regulates the expression of HIF-α mRNA, thereby causing an increase of ROS in cells and a decrease in the mitochondrial membrane potential to promote cell apoptosis and cell cycle arrest. The inhibitory effect of celastrol on B16-F10 cells was further demonstrated by co-culturing with a PI3K activator.

CONCLUSION

Celastrol inhibits the function of B16-F10 cells by inhibiting the PI3K/AKT/mTOR cellular pathway and regulating the expression of downstream HIF-α mRNA.

Progress in the Regulation of Immune Cells in the Tumor Microenvironment by Bioactive Compounds of Traditional Chinese Medicine

The tumor microenvironment (TME) can aid tumor cells in evading surveillance and clearance by immune cells, creating an internal environment conducive to tumor cell growth. Consequently, there is a growing focus on researching anti-tumor immunity through the regulation of immune cells within the TME. Various bioactive compounds in traditional Chinese medicine (TCM) are known to alter the immune balance by modulating the activity of immune cells in the TME. In turn, this enhances the body's immune response, thus promoting the effective elimination of tumor cells. This study aims to consolidate recent findings on the regulatory effects of bioactive compounds from TCM on immune cells within the TME. The bioactive compounds of TCM regulate the TME by modulating macrophages, dendritic cells, natural killer cells and T lymphocytes and their immune checkpoints. TCM has a long history of having been used in clinical practice in China. Chinese medicine contains various chemical constituents, including alkaloids, polysaccharides, saponins and flavonoids. These components activate various immune cells, thereby improving systemic functions and maintaining overall health. In this review, recent progress in relation to bioactive compounds derived from TCM will be covered, including TCM alkaloids, polysaccharides, saponins and flavonoids. This study provides a basis for further in-depth research and development in the field of anti-tumor immunomodulation using bioactive compounds from TCM.

Collision of herbal medicine and nanotechnology: a bibliometric analysis of herbal nanoparticles from 2004 to 2023

BACKGROUND

Herbal nanoparticles are made from natural herbs/medicinal plants, their extracts, or a combination with other nanoparticle carriers. Compared to traditional herbs, herbal nanoparticles lead to improved bioavailability, enhanced stability, and reduced toxicity. Previous research indicates that herbal medicine nanomaterials are rapidly advancing and making significant progress; however, bibliometric analysis and knowledge mapping for herbal nanoparticles are currently lacking. We performed a bibliometric analysis by retrieving publications related to herbal nanoparticles from the Web of Science Core Collection (WoSCC) database spanning from 2004 to 2023. Data processing was performed using the R package Bibliometrix, VOSviewers, and CiteSpace.

RESULTS

In total, 1876 articles related to herbal nanoparticles were identified, originating from various countries, with China being the primary contributing country. The number of publications in this field increases annually. Beijing University of Chinese Medicine, Shanghai University of Traditional Chinese Medicine, and Saveetha University in India are prominent research institutions in this domain. The Journal "International Journal of Nanomedicine" has the highest number of publications. The number of authors of these publications reached 8234, with Yan Zhao, Yue Zhang, and Huihua Qu being the most prolific authors and Yan Zhao being the most frequently cited author. "Traditional Chinese medicine," "drug delivery," and "green synthesis" are the main research focal points. Themes such as "green synthesis," "curcumin," "wound healing," "drug delivery," and "carbon dots" may represent emerging research areas.

CONCLUSIONS

Our study findings assist in identifying the latest research frontiers and hot topics, providing valuable references for scholars investigating the role of nanotechnology in herbal medicine.

Nano-formulated delivery of active ingredients from traditional Chinese herbal medicines for cancer immunotherapy

Cancer immunotherapy has garnered promise in tumor progression, invasion, and metastasis through establishing durable and memorable immunological activity. However, low response rates, adverse side effects, and high costs compromise the additional benefits for patients treated with current chemical and biological agents. Chinese herbal medicines (CHMs) are a potential treasure trove of natural medicines and are gaining momentum in cancer immunomodulation with multi-component, multi-target, and multi-pathway characteristics. The active ingredient extracted from CHMs benefit generalized patients through modulating immune response mechanisms. Additionally, the introduction of nanotechnology has greatly improved the pharmacological qualities of active ingredients through increasing the hydrophilicity, stability, permeability, and targeting characteristics, further enhancing anti-cancer immunity. In this review, we summarize the mechanism of active ingredients for cancer immunomodulation, highlight nano-formulated deliveries of active ingredients for cancer immunotherapy, and provide insights into the future applications in the emerging field of nano-formulated active ingredients of CHMs.

Celastrol Elicits Antitumor Effects through Inducing Immunogenic Cell Death and Downregulating PD-L1 in ccRCC

BACKGROUND

Targeting immunogenic cell death (ICD) is considered a promising therapeutic strategy for cancer. However, the commonly identified ICD inducers promote the expression of programmed cell death ligand 1 (PD-L1) in tumor cells, thus aiding them to evade the recognition and killing by the immune system. Therefore, the finding of novel ICD inducers to avoid enhanced PD-L1 expression is of vital significance for cancer therapy. Celastrol (CeT), a triterpene isolated from Tripterygium wilfordii Hook. F induces various forms of cell death to exert anti-cancer effects, which may make celastrol an attractive candidate as an inducer of ICD.

METHODS

In the present study, bioinformatics analysis was combined with experimental validation to explore the underlying mechanism by which CeT induces ICD and regulates PD-L1 expression in clear cell renal cell carcinoma (ccRCC).

RESULTS

The results showed that EGFR, IKBKB, PRKCQ and MAPK1 were the crucial targets for CeT-induced ICD, and only MAPK1 was an independent prognostic factor for the overall survival (OS) of ccRCC patients. In addition, CeT triggered autophagy and up-regulated the expressions of HMGB1 and CRT to induce ICD in 786-O cells in vitro. Importantly, CeT can down-regulate PD-L1 expression through activating autophagy. At the molecular level, CeT suppressed PD-L1 via the inhibition of MAPK1 expression. Immunologically, the core target of celastrol, MAPK1, was tightly correlated with CD8+ T cells and CD4+ T cells in ccRCC.

CONCLUSION

These findings indicate that CeT not only induces ICD but also suppresses PD-L1 by down-regulating MAPK1 expression, which will provide an attractive strategy for ccRCC immunotherapy.

Recent progress, perspectives, and issues of engineered PD-L1 regulation nano-system to better cure tumor: A review

Currently, immune checkpoint blockade (ICB) therapies that target the programmed cell death ligand-1 (PD-L1) have been used as revolutionary cancer treatments in the clinic. Apart from restoring the antitumor response of cytotoxic T cells by blocking the interaction between PD-L1 on tumor cells and programmed cell death-1 (PD-1) on T cells, PD-L1 proteins were also newly revealed to possess the capacity to accelerate DNA damage repair (DDR) and enhance tumor growth through multiple mechanisms, leading to the impaired efficacy of tumor therapies. Nevertheless, current free anti-PD-1/PD-L1 therapy still suffered from poor therapeutic outcomes in most solid tumors due to the non-selective tumor accumulation, ineludible severe cytotoxic effects, as well as the common occurrence of immune resistance. Recently, nanoparticles with efficient tumor-targeting capacity, tumor-responsive prosperity, and versatility for combination therapy were identified as new avenues for PD-L1 targeting cancer immunotherapies. In this review, we first summarized the multiple functions of PD-L1 protein in promoting tumor growth, accelerating DDR, as well as depressing immunotherapy efficacy. Following this, the effects and mechanisms of current clinically widespread tumor therapies on tumor PD-L1 expression were discussed. Then, we reviewed the recent advances in nanoparticles for anti-PD-L1 therapy via using PD-L1 antibodies, small interfering RNA (siRNA), microRNA (miRNA), clustered, regularly interspaced, short palindromic repeats (CRISPR), peptide, and small molecular drugs. At last, we discussed the challenges and perspectives to promote the clinical application of nanoparticles-based PD-L1-targeting therapy.

Tumor Microenvironment Sequential Drug/Gene Delivery Nanosystem for Realizing Multistage Boosting of Cancer-Immunity Cycle on Cancer Immunotherapy

The antitumor immune response of cancer immunotherapy is a cascade of cancer-immunity cycles (CIC). The immunosuppression of the tumor microenvironment and low immunogenicity of tumor cells, insufficient T lymphocyte activation, trafficking, and infiltration caused the failure to initiate and run the continuous multistage CIC, leading to unsatisfactory cancer immunotherapy outcomes. A doxorubicin/interleukin-12 plasmid DNA/celecoxib (DOX/pIL-12/CXB) combination strategy was designed by targeting the cascade CIC. Then, an intratumoral CXB-detachable nanosystem, or DOX/PAC/pIL-12 micelleplexes, was developed for sequential drug/gene delivery to facilitate the multistage boosting of CIC on synergistic cancer immunotherapy. The DOX/PAC/pIL-12 micelleplexes could program intratumorally sequential release of CXB to remodulate the tumor microenvironment immunosuppression by suppressing the cyclooxygenase-2/prostaglandin E2 (COX-2/PGE2) pathway. The smaller sizes and surface charge-switched micelleplexes facilitated the codelivery and corelease of DOX and pIL-12 inside 4T1 tumor cells. These micelleplexes exerted a synergistic antitumor immune response using CIC cascade activation and amplification, providing therapeutic antitumor and antimetastasis efficacy. The drug/gene sequential delivery nanosystem provides a complete CIC-boosted combinatory strategy for developing immunotherapy against cancer.

"Closed-Loop" O2-Economizer Induced In Situ Therapeutic Vaccine against Hypoxic Tumors

Therapeutic tumor vaccines, which use tumor antigens to stimulate a cancer patient's immune system to eventually kill the tumor tissues, have emerged as one of the most attractive strategies in anticancer research. Especially, exploring in situ vaccines has become a potential field in cancer immunotherapy. However, due to the hypoxic tumor microenvironment, the generation of tumor antigens is always mild and not sufficient. Hence, in this study, we designed a closed-loop mitochondrial oxygen-economizer (TPCA) to induce enhanced phototherapy-driven in situ vaccines. The O2-economizer was developed by the integration of the photosensitizer CyI and the mitochondrial inhibitor atovaquone into the PAMAM dendrimer. In vitro and in vivo studies showed that TPCA could enter the mitochondria through (3-propylcarboxyl) triphenylphosphine bromide (TPP) and effectively restrict the respiration of tumor cells to reduce tumor hypoxia, thus providing continuous oxygen for enhanced iodinated cyanine dye mediated photodynamic therapy, which could further induce in situ vaccines for ablating the primary tumor directly and inhibiting the tumor metastasis and recurrence. Furthermore, the antitumor mechanism revealed that O2-economizer-based oxygen-boosted PDT elicited immunogenic cancer cell death with enhanced exposure and release of DAMPs and altered the immunosuppressive tumor microenvironment with increased recruitment of T cells in tumors, thereby inducing in situ vaccines and provoking the systematic antitumor responses against CT26 tumors. This study will provide innovative approaches for local, abscopal, and metastatic tumor treatment.

Four Ounces Can Move a Thousand Pounds: The Enormous Value of Nanomaterials in Tumor Immunotherapy

The application of nanomaterials in healthcare has emerged as a promising strategy due to their unique structural diversity, surface properties, and compositional diversity. In particular, nanomaterials have found a significant role in improving drug delivery and inhibiting the growth and metastasis of tumor cells. Moreover, recent studies have highlighted their potential in modulating the tumor microenvironment (TME) and enhancing the activity of immune cells to improve tumor therapy efficacy. Various types of nanomaterials are currently utilized as drug carriers, immunosuppressants, immune activators, immunoassay reagents, and more for tumor immunotherapy. Necessarily, nanomaterials used for tumor immunotherapy can be grouped into two categories: organic and inorganic nanomaterials. Though both have shown the ability to achieve the purpose of tumor immunotherapy, their composition and structural properties result in differences in their mechanisms and modes of action. Organic nanomaterials can be further divided into organic polymers, cell membranes, nanoemulsion-modified, and hydrogel forms. At the same time, inorganic nanomaterials can be broadly classified as nonmetallic and metallic nanomaterials. The current work aims to explore the mechanisms of action of these different types of nanomaterials and their prospects for promoting tumor immunotherapy.

Stimulators of immunogenic cell death for cancer therapy: focusing on natural compounds

A growing body of evidence indicates that the anticancer effect of the immune system can be activated by the immunogenic modulation of dying cancer cells. Cancer cell death, as a result of the activation of an immunomodulatory response, is called immunogenic cell death (ICD). This regulated cell death occurs because of increased immunogenicity of cancer cells undergoing ICD. ICD plays a crucial role in stimulating immune system activity in cancer therapy. ICD can therefore be an innovative route to improve anticancer immune responses associated with releasing damage-associated molecular patterns (DAMPs). Several conventional and chemotherapeutics, as well as preclinically investigated compounds from natural sources, possess immunostimulatory properties by ICD induction. Natural compounds have gained much interest in cancer therapy owing to their low toxicity, low cost, and inhibiting cancer cells by interfering with different mechanisms, which are critical in cancer progression. Therefore, identifying natural compounds with ICD-inducing potency presents agents with promising potential in cancer immunotherapy. Naturally derived compounds are believed to act as immunoadjuvants because they elicit cancer stress responses and DAMPs. Acute exposure to DAMP molecules can activate antigen-presenting cells (APCs), such as dendritic cells (DCs), which leads to downstream events by cytotoxic T lymphocytes (CTLs) and natural killer cells (NKs). Natural compounds as inducers of ICD may be an interesting approach to ICD induction; however, parameters that determine whether a compound can be used as an ICD inducer should be elucidated. Here, we aimed to discuss the impact of multiple ICD inducers, mainly focusing on natural agents, including plant-derived, marine molecules, and bacterial-based compounds, on the release of DAMP molecules and the activation of the corresponding signaling cascades triggering immune responses. In addition, the potential of synthetic agents for triggering ICD is also discussed.

Enhancing Immunogenicity in Metastatic Melanoma: Adjuvant Therapies to Promote the Anti-Tumor Immune Response

Advanced melanoma is an aggressive form of skin cancer characterized by low survival rates. Less than 50% of advanced melanoma patients respond to current therapies, and of those patients that do respond, many present with tumor recurrence due to resistance. The immunosuppressive tumor-immune microenvironment (TIME) remains a major obstacle in melanoma therapy. Adjuvant treatment modalities that enhance anti-tumor immune cell function are associated with improved patient response. One potential mechanism to stimulate the anti-tumor immune response is by inducing immunogenic cell death (ICD) in tumors. ICD leads to the release of damage-associated molecular patterns within the TIME, subsequently promoting antigen presentation and anti-tumor immunity. This review summarizes relevant concepts and mechanisms underlying ICD and introduces the potential of non-ablative low-intensity focused ultrasound (LOFU) as an immune-priming therapy that can be combined with ICD-inducing focal ablative therapies to promote an anti-melanoma immune response.

A celastrol-based nanodrug with reduced hepatotoxicity for primary and metastatic cancer treatment

BACKGROUND

Cancer is the world's leading cause of death and a key hindrance to extending life expectancy. Celastrol, a bioactive compound derived from Tripterygium wilfordii, has been shown to have excellent antitumor activity, but its poor solubility and severe organ toxicity side effects have hampered its clinical application.

METHODS

In this study, a self-assembled nanodrug (PLC-NP) was designed to deliver celastrol to tumor sites while efficiently reducing its side effects by conjugating celastrol with the bioactive material LMWH and P-selectin targeting peptide (PSN). Extensive in vitro and in vivo experiments were performed to investigate both therapeutic efficacy and adverse effects. Furthermore, the specific mechanism of the antitumor activity has also been explored.

FINDING

The PLC-NP nanodrugs were spherical in shape, with a mean particle size of 115.83 ± 6.93 nm. PLC-NP was sufficiently stable during blood circulation, with a selective target to P-selectin-highly expressed tumor cells, followed by releasing the containing celastrol under acidic environment and high levels of esterase in tumor cells. Both in vitro and in vivo results confirmed that celastrol's antitumor and anti-metastatic abilities were not attenuated and were actually strengthened after being formed into nanodrugs. More importantly, the organ toxicities of the modified celastrol nanodrug were dramatically reduced. Mechanistic study indicated that the inactivation of PI3K/Akt/mTOR signaling pathway and ROS-mediated mitochondrial dysfunction play critical roles in celastrol-mediated autophagy and apoptosis.

INTERPRETATION

Our findings could offer a potential strategy for the translation of toxic compounds into clinical therapeutic nanomedicine.

FUNDING

See a detailed list of funding bodies in the Acknowledgements section at the end of the manuscript.

Celastrol inhibits gastric cancer cell proliferation, migration, and invasion via the FOXA1/CLDN4 axis

Background

Celastrol is a biologically active compound with potent anti-tumor properties. However, the mechanism of action of celastrol in gastric cancer (GC) has not been fully elucidated.

Methods

To explore the specific mechanism of the effect of celastrol on GC cells. GC cells were transfected with forkhead box A1 (FOXA1) or claudin 4 (CLDN4), or short hairpin RNA targeting FOXA1. The expressions of FOXA1 and CLDN4 in GC cells were determined by quantitative reverse transcription PCR and Western blot. GC cell proliferation, migration, and invasion were measured by MTT assay and Transwell assay, respectively. The interaction between CLDN4 and FOXA1 was examined by luciferase reporter assay.

Resluts

CLDN4 and FOXA1 were upregulated in GC cells. Celastrol prevented the proliferation, migration, and invasion of GC cells by downregulating FOXA1 expression. Overexpression of FOXA1 or CLDN4 accelerated GC progression. CLDN4 overexpression also induced the activation of the expressions of phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) pathway. FOXA1 enhanced the transcription of CLDN4.

Conclusion

Celastrol regulated GC progression via targeting the FOXA1/CLDN4 axis to impede the PI3K/AKT pathway. Our study proposed a new mechanism of how celastrol inhibited tumorigenesis in GC, which provided evidence for the potential use of celastrol for anti-GC treatment.

Self-assembling nanoarchitectonics of size-controllable celastrol nanoparticles for efficient cancer chemotherapy with reduced systemic toxicity

Celastrol, extracted from Tripterygium wilfordii Hook F, is one of the most promising natural extract for cancer treatment. Nevertheless, insufficient tumor retention and severe systemic toxicity still hinder its application. Herein, we report for the first time that Celastrol can directly self-assemble into size-controllable nanoparticles through the anti-solvent method by using different good solvent or by the variation of Celastrol concentrations. In vitro anti-cancer experiment revealed that the as-prepared nanoparticles can kill MCF-7 cells more effectively. Moreover, the nanoparticles can efficiently accumulate in tumors of the tumor bearing mice after tail vein injection. Under the administration of lethal dosage of Celastrol, the tumors are greatly suppressed and the mice maintain the activity. These results demonstrate that anti-solvent method may be a promising strategy to fabricate Celastrol nano-drugs with controllable size and less systemic toxicity for further clinical cancer treatment.

CaCO3 powder-mediated biomineralization of antigen nanosponges synergize with PD-1 blockade to potentiate anti-tumor immunity

Antigen self-assembly nanovaccines advance the minimalist design of therapeutic cancer vaccines, but the issue of inefficient cross-presentation has not yet been fully addressed. Herein, we report a unique approach by combining the concepts of "antigen multi-copy display" and "calcium carbonate (CaCO₃) biomineralization" to increase cross-presentation. Based on this strategy, we successfully construct sub-100 nm biomineralized antigen nanosponges (BANSs) with high CaCO₃ loading (38.13 wt%) and antigen density (61.87%). BANSs can be effectively uptaken by immature antigen-presenting cells (APCs) in the lymph node upon subcutaneous injection. Achieving efficient spatiotemporal coordination of antigen cross-presentation and immune effects, BANSs induce the production of CD4⁺ T helper cells and cytotoxic T lymphocytes, resulting in effective tumor growth inhibition. BANSs combined with anti-PD-1 antibodies synergistically enhance anti-tumor immunity and reverse the tumor immunosuppressive microenvironment. Overall, this CaCO₃ powder-mediated biomineralization of antigen nanosponges offer a robust and safe strategy for cancer immunotherapy.

Tripterygium wilfordii Hook.f. ameliorates paraquat-induced lung injury by reducing oxidative stress and ferroptosis via Nrf2/HO-1 pathway

Paraquat (PQ) poisoning can induce acute lung injury and fibrosis and has an extremely high mortality rate. However, no effective treatments for PQ poisoning have been established. In this study, the potential efficacy of Tripterygium wilfordii Hook.f. (TwHF) in alleviating PQ-induced lung injury and fibrosis was investigated in a mouse model. Mice were randomly assigned to the control, PQ, PQ + TwHF1 (pretreatment before inducing poisoning), and PQ + TwHF2 (treatment after poisoning) groups. The mice in the PQ + TwHF1 group were pretreated with TwHF for 5 days before receiving one dose of PQ (120 mg/kg) and then received a daily oral gavage of the indicated dosages of TwHF until sacrifice. The mice in the PQ + TwHF2 group were treated with TwHF 2 h after PQ exposure until sacrifice. The pathological analysis and Fapi PET/CT showed that treatment with TwHF attenuated lung injury. And TwHF reduced pulmonary oxidative stress, as indicated by the reduction in, malondialdehyde (MDA), glutathione (GSH), and reactive oxygen species (ROS) levels, as well as by the increase in superoxide dismutase (SOD) levels. Accordingly, the Perls DAB staining showed increased iron concentrations and western blotting revealed a decreased GPX4 expression after PQ exposure, as well as the mitigation of the overexpression of Nrf2 and HO-1 induced by PQ. In conclusion, our study demonstrated the potential of TwHF as a treatment for PQ-induced lung injury and fibrosis. The protective mechanism of this medicinal herb may involve the regulation of ferroptosis.

Engineering nanoparticles boost TNBC therapy by CD24 blockade and mitochondrial dynamics regulation

Although cancer immunotherapy has achieved remarkable progress, the clinical treatment of triple-negative breast cancer (TNBC) is still tough to make a breakthrough. The unsatisfactory therapeutic effect may be attributed to the lack of tumor immunogenicity and the strong immunosuppressive tumor microenvironment (ITM). In order to overcome the above shortcomings, engineering nanoparticles (P-aCD24/CEL + P/shMFN1) was designed to deliver anti-CD24 monoclonal antibody (aCD24), celastrol (CEL) and mitofusin 1 shRNA (shMFN1) for synergistic tumor cells-targeted treatment and tumor-associated macrophages (TAMs)-targeted immunomodulation. CD24, highly expressed on tumor cells, interacts with Siglec10 on TAMs to protect tumor cells from phagocytosis by macrophages, and thus has become a novel and dominant immune checkpoint in TNBC. P-aCD24/CEL achieved the release of aCD24 based on the dual response of carrier to pH and MMP2 in tumor microenvironment. Moreover, CEL increased "eat me" signal CRT and induced the immunogenic cell death (ICD) of tumor cells, together with decreased "don't eat me" signal CD24, reactivated macrophage phagocytosis of tumor cells, and ultimately improves the macrophage-based immunotherapy. On the other hand, P/shMFN1 could target TAMs for mitochondrial dynamics regulation via durable MFN1 silencing in TAMs, thereby reversing the phenotype of M2-TAMs. P-aCD24/CEL and P/shMFN1 could synergistically elicit evident antitumor immune responses and long-term immune memory to significantly inhibit tumor progress and postoperative recurrence. Based on remodeling the ITM and increasing antitumor immune response, this combination immunotherapy strategy showed great potential for TNBC treatment.

Self-delivery biomedicine for enhanced photodynamic therapy by feedback promotion of tumor autophagy

Reactive oxygen species (ROS) generated during photodynamic therapy (PDT) can induce autophagy to protect tumor cell from PDT-induced apoptosis. In this work, a self-delivery autophagy regulator (designated as CeCe) is developed for autophagy promotion sensitized PDT against tumor. Briefly, CeCe is prepared by the assembly of a photosensitizer of chlorin e6 (Ce6) and autophagy promoter of celastrol. By virtue of intermolecular interactions, Ce6 and celastrol are able to self-assemble into nanomedicine with great photodynamic performance and autophagy regulation capacity. Under light irradiation, CeCe would produce ROS in tumor cells to amplify the oxidative stress and promote cell autophagy. As a result, CeCe exhibits an enhanced photo toxicity by inducing autophagic cell death. In vivo experiments indicate that CeCe can predominantly accumulate in tumor tissue for a robust PDT. Moreover, CeCe has a superior therapeutic efficiency compared to monotherapy and combined treatment of Ce6 and celastrol, suggesting a synergistic antitumor effect of PDT and autophagy promotion. This self-delivery nanomedicine may advance the development of the co-delivery nanoplatform to improve the antitumor efficacy of PDT by promoting autophagy. STATEMENT OF SIGNIFICANCE: Autophagy is a "double-edged sword" in cellular homeostasis and metabolism, which can promote tumor progression but also induce an unknown impact on tumor inhibition. In this work, a self-delivery autophagy regulator (designated as CeCe) was developed for autophagy promotion sensitized photodynamic therapy (PDT). By virtue of intermolecular interactions, Ce6 and celastrol were found to self-assemble into stable CeCe without drug excipients, which exhibited great photodynamic performance and autophagy regulation capacity. In vitro and in vivo findings demonstrated a superior tumor suppression ability of CeCe over the monotherapy as well as the combined treatment of Ce6 and celastrol, suggesting a synergistic antitumor efficacy by PDT and autophagy promotion.

Hypoxia-responsive Immunostimulatory Nanomedicines Synergize with Checkpoint Blockade Immunotherapy for Potentiating Cancer Immunotherapy

Inducing cell death while simultaneously enhancing antitumor immune responses is a promising therapeutic approach for multiple cancers. Celastrol (Cel) and 7-ethyl-10-hydroxycamptothecin (SN38) have contrasting physicochemical properties, but strong synergy in immunogenic cell death induction and anticancer activity. Herein, a hypoxia-sensitive nanosystem (CS@TAP) was designed to demonstrate effective immunotherapy for colorectal cancer by systemic delivery of an immunostimulatory chemotherapy combination. Furthermore, the combination of CS@TAP with anti-PD-L1 mAb (αPD-L1) exhibited a significant therapeutic benefit of delaying tumor growth and increased local doses of immunogenic signaling and T-cell infiltration, ultimately extending survival. We conclude that CS@TAP is an effective inducer of immunogenic cell death (ICD) in cancer immunotherapy. Therefore, this study provides an encouraging strategy to synergistically induce immunogenic cell death to enhance tumor cytotoxic T lymphocytes (CTLs) infiltration for anticancer immunotherapy.

Hypoxia-responsive Immunostimulatory Nanomedicines Synergize with Checkpoint Blockade Immunotherapy for Potentiating Cancer Immunotherapy

Inducing cell death while simultaneously enhancing antitumor immune responses is a promising therapeutic approach for multiple cancers. Celastrol (Cel) and 7-ethyl-10-hydroxycamptothecin (SN38) have contrasting physicochemical properties, but strong synergy in immunogenic cell death induction and anticancer activity. Herein, a hypoxia-sensitive nanosystem (CS@TAP) was designed to demonstrate effective immunotherapy for colorectal cancer by systemic delivery of an immunostimulatory chemotherapy combination. Furthermore, the combination of CS@TAP with anti-PD-L1 mAb (αPD-L1) exhibited a significant therapeutic benefit of delaying tumor growth and increased local doses of immunogenic signaling and T-cell infiltration, ultimately extending survival. We conclude that CS@TAP is an effective inducer of immunogenic cell death (ICD) in cancer immunotherapy. Therefore, this study provides an encouraging strategy to synergistically induce immunogenic cell death to enhance tumor cytotoxic T lymphocytes (CTLs) infiltration for anticancer immunotherapy.

Pluronic® triblock copolymer-based nanoformulations for cancer therapy: A 10-year overview

This paper provides a review of the literature on the use of Pluronic® triblock copolymers for drug encapsulation over the last 10 years. A special focus is given to the progress of drug delivery systems (e.g., micelles, liposomes, micro/nanoemulsions, hydrogels and nanogels, and polymersomes and niosomes); the beneficial aspects of Pluronic® triblock copolymers as biological response modifiers and as pharmaceutical additives, adjuvants, and stabilizers, are also discussed. The advantages and limitations encountered in developing site-specific targeting approaches based on Pluronic-based nanostructures in cancer treatment are highlighted, in addition to innovative examples for improving tumor cytotoxicity while reducing side effects.

Ginsenoside Rg3 nanoparticles with permeation enhancing based chitosan derivatives were encapsulated with doxorubicin by thermosensitive hydrogel and anti-cancer evaluation of peritumoral hydrogel injection combined with PD-L1 antibody

BACKGROUND

Combination of chemotherapy and immune checkpoint inhibitor therapy has greatly improved the anticancer effect on multiple malignancies. However, the efficiency on triple-negative breast cancer (TNBC) is limited, since most patients bear "cold" tumors with low tumor immunogenicity. Doxorubicin (DOX), one of the most effective chemotherapy agents, can induce immunogenic cell death (ICD) and thus initiating immune response.

METHODS

In this study, to maximize the ICD effect induced by DOX, chitosan and cell-penetrating peptide (R6F3)-modified nanoparticles (PNPs) loaded with ginsenoside Rg3 (Rg3) were fabricated using the self-assembly technique, followed by co-encapsulation with DOX based on thermo-sensitive hydrogel. Orthotopic tumor model and contralateral tumor model were established to observe the antitumor efficacy of the thermo-sensitive hydrogel combined with anti-PD-L1 immunotherapy, besides, the biocompatibility was also evaluated by histopathological.

RESULTS

Rg3-PNPs strengthened the immunogenic cell death (ICD) effect induced by DOX. Moreover, the hydrogel co-loading Rg3-PNPs and DOX provoked stronger immune response in originally nonimmunogenic 4T1 tumors than DOX monotherapy. Following combination with PD-L1 blocking, substantial antitumor effect was achieved due to the recruitment of memory T cells and the decline of adaptive PD-L1 enrichment.

CONCLUSION

The hydrogel encapsulating DOX and highly permeable Rg3-PNPs provided an efficient strategy for remodeling immunosuppressive tumor microenvironment and converting immune "cold" 4T1 into "hot" tumors.

Engineered nanomaterials trigger abscopal effect in immunotherapy of metastatic cancers

Despite advances in cancer treatment, metastatic cancer is still the main cause of death in cancer patients. At present, the treatment of metastatic cancer is limited to palliative care. The abscopal effect is a rare phenomenon in which shrinkage of metastatic tumors occurs simultaneously with the shrinkage of a tumor receiving localized treatment, such as local radiotherapy or immunotherapy. Immunotherapy shows promise for cancer treatment, but it also leads to consequences such as low responsiveness and immune-related adverse events. As a promising target-based approach, intravenous or intratumoral injection of nanomaterials provides new opportunities for improving cancer immunotherapy. Chemically modified nanomaterials may be able to trigger the abscopal effect by regulating immune cells. This review discusses the use of nanomaterials in killing metastatic tumor cells through the regulation of immune cells and the prospects of such nanomaterials for clinical use.

SHP2 inhibition improves celastrol-induced growth suppression of colorectal cancer

This study aimed to explore novel targets for celastrol sensitization in colorectal cancer (CRC) based on differentially regulated signals in response to high- or low-dose celastrol. Targeting signals were investigated using Western blotting or phosphorylated receptor tyrosine kinase (RTK) arrays. Corresponding inhibitors for the signals were individually combined with low-dose celastrol for the assessment of combined anti-CRC effects, based on proliferation, apoptosis, colony assays, and xenograft models. The potential mechanism for the combination of celastrol and SHP2 inhibition was further examined. Low-dose celastrol (<1 µM) did not effectively suppress AKT and ERK signals in CRC cells compared to high-dose celastrol (>1 µM). However, when combined with an AKT or ERK inhibitor, low-dose celastrol could cooperatively suppress CRC proliferation. Furthermore, failed AKT or ERK inhibition by low-dose celastrol may be due to reactivated RTK-SHP2 signaling with negative feedback. The combination of celastrol and the SHP2 inhibitor resulted in greatly reduced AKT and ERK signals, as well as greater inhibition of CRC growth than celastrol alone. Moreover, the mechanism underlying combination suppression was also involved in the activation of immune cell infiltration (mainly for CD8+ cells) in CRC tissues. Failure to inhibit RTK-SHP2-AKT/ERK signaling contributed to the lack of CRC growth suppression by low-dose celastrol. However, the combination of celastrol and the SHP2 inhibitor resulted in synergistic inhibition of CRC growth and provided a promising therapeutic target.

A polymeric IDO inhibitor based on poly(ethylene glycol)-b-poly(L-tyrosine-co-1-methyl-D-tryptophan) enables facile trident cancer immunotherapy

Indoleamine 2,3-dioxygenase (IDO), with an immunoregulatory effect related to tryptophan metabolism, has emerged as an attractive target for cancer immunotherapy. Here, a polymeric IDO inhibitor based on the poly(ethylene glycol)-b-poly(L-tyrosine-co-1-methyl-D-tryptophan) copolymer (PEG-b-P(Tyr-co-1-MT)) was developed for facile trident cancer immunotherapy. PEG-b-P(Tyr-co-1-MT) could self-assemble into nanoparticles (NPs), which were subject to enzyme degradation and capable of retarding the metabolism of L-tryptophan (TRP) to L-kynurenine (KYN) in B16F10 cancer cells. Notably, cRGD-functionalized NPs showed efficient encapsulation and an enzyme-responsive release of doxorubicin (DOX) and the BET bromodomain inhibitor JQ1. DOX in drug-loaded nanoparticles (cRGD-NPDJ) could activate immunization by inducing the discernible immunogenic cell death (ICD) of cancer cells and promoting the secretion of interferon-γ (IFN-γ), which besides activating the antitumor cellular immunity often upregulates the expression of PD-L1 and IDO to accelerate tumor progression. The encapsulated JQ1 and polymeric 1-MT in cRGD-NPDJ could reverse the expression by disrupting the binding of BET proteins with chromatin and elevating the TRP/KYN ratio. In B16F10 tumor-bearing C57BL/6 mice, cRGD-NPDJ displayed significantly increased CD8⁺ T cells, matured dendritic cells (mDCs), and cytokines (IFN-γ, TNF-α), as well as reduced regulatory T cells and downregulated PD-L1 expression at tumor sites, generating immune cascade reactions and a distinct improvement of the tumor microenvironment (TME), leading to significant tumor suppression and survival prolongation. The polymeric IDO inhibitor provides a facile strategy for the co-delivery of chemotherapeutics and inhibitors for efficient and safe combination cancer immunotherapy.

When Natural Compounds Meet Nanotechnology: Nature-Inspired Nanomedicines for Cancer Immunotherapy

Recent significant strides of natural compounds in immunomodulation have highlighted their great potential against cancer. Despite many attempts being made for cancer immunotherapy, the biomedical application of natural compounds encounters a bottleneck because of their unclear mechanisms, low solubility and bioavailability, and limited efficacy. Herein, we summarize the immune regulatory mechanisms of different natural compounds at each step of the cancer-immunity cycle and highlight their anti-tumor potential and current limitations. We then propose and present various drug delivery strategies based on nanotechnology, including traditional nanoparticles (NPs)-based delivery strategies (lipid-based NPs, micelles, and polysaccharide/peptide/protein-based NPs) and novel delivery strategies (cell-derived NPs and carrier-free NPs), thus providing solutions to break through existing bottlenecks. Furthermore, representative applications of nature-inspired nanomedicines are also emphasized in detail with the advantages and disadvantages discussed. Finally, the challenges and prospects of natural compounds for cancer immunotherapy are provided, hopefully, to facilitate their far-reaching development toward clinical translation.

Demystifying phytoconstituent-derived nanomedicines in their immunoregulatory and therapeutic roles in inflammatory diseases

In the past decades, phytoconstituents have appeared as critical mediators for immune regulations among various diseases, both in eukaryotes and prokaryotes. These bioactive molecules, showing a broad range of biological functions, would hold tremendous promise for developing new therapeutics. The discovery of phytoconstituents' capability of functionally regulating immune cells and associating cytokines, suppressing systemic inflammation, and remodeling immunity have rapidly promoted the idea of their employment as anti-inflammatory agents. In this review, we discuss various roles of phyto-derived medicines in the field of inflammatory diseases, including chronic inflammation, autoimmune diseases, and acute inflammatory disease such as COVID-19. Nevertheless, traditional phyto-derived medicines often concurred with their clinical administration limitations, such as their lack of cell specificity, inefficient cytoplasmic delivery, and rapid clearance by the immune system. As alternatives, phyto-derived nano-approaches may provide significant benefits. Both unmodified and engineered nanocarriers present the potential to serve as phytoconstituent delivery systems to improve therapeutic physio-chemical properties and pharmacokinetic profiles. Thus, the development of phytoconstituents' nano-delivery designs, their new and perspective approaches for therapeutical applications are elaborated herein.

GA&HA-Modified Liposomes for Co-Delivery of Aprepitant and Curcumin to Inhibit Drug-Resistance and Metastasis of Hepatocellular Carcinoma

Background

Tumor microenvironment (TME) plays a vital role in the development of hepatocellular carcinoma (HCC). Mounting evidence indicates that peripheral nerves could induce a shift from quiescent hepatic stellate cells (HSCs) to cancer-associated fibroblasts (CAFs) by secreting substance P (SP). The anti-tumor strategy by targeting “SP-HSCs-HCC” axis might be an effective therapy to inhibit tumor growth and metastasis.

Objective

In this study, we prepared novel liposomes (CUR-APR/HA&GA-LPs) modified with hyaluronic acid (HA) and glycyrrhetinic acid (GA) for co-delivery aprepitant (APR) and curcumin (CUR), in which APR was chosen to inhibit the activation of HSCs by blocking SP/neurokinin-1 receptor (NK-1R), and CUR was used to induce apoptosis of tumor cells.

Results

To mimic the TME, we established “SP+HSCs+HCC” co-cultured cell model in vitro. The results showed that CUR-APR/HA&GA-LPs could be taken up by CAFs and HCC simultaneously, and inhibit tumor cell migration. Meanwhile, the “SP+m-HSCs+HCC” co-implanted mice model was established to evaluate the anti-tumor effect in vivo. The results showed that CUR-APR/HA&GA-LPs could inhibit tumor proliferation and metastasis, and reduce extracellular matrix (ECM) deposition and tumor angiogenesis, indicating a superior anti-HCC effect.

Conclusion

Overall, the combination therapy based on HA&GA-LPs could be a potential nano-sized formulation for anti-HCC therapy.

Split bullets loaded nanoparticles for amplified immunotherapy

Dendritic cells (DCs) play central role in adaptive antitumor immunity, while their function is often hampered by low immunogenicity of tumor tissues and surrounding hostile microenvironment. Herein, a "split bullets" loaded nanoplatform that can bidirectionally injure mitochondria (MT) and endoplasmic reticulum (ER) of tumor cells is developed. After cellular uptake, the released "split bullets" separately target to different subcellular destinations and exert distinct effects on DCs: (1) MT-targeted "bullet" recruits peripheral DCs into tumor sites, due to its capability to trigger adenosine triphosphate release from tumor cells; (2) ER-targeted "bullet" activates tumor-infiltrating DCs, which is attributed to its ability to evoke calreticulin exposure on tumor cells. These effects collectively improve the tropism and reactivity of DCs to tumor-specific antigen in a two-pronged way. As a result of enhanced function of DCs in antigen capture, treatment of the "split bullets" loaded nanoplatform ignites robust immune response to suppress primary melanoma, and establishes systemic immune memory against post-surgical tumor recurrence. Overall, this nanoplatform offers a generalizable approach to boost DCs and augment immunotherapy.

Multifunctional Lipid Bilayer Nanocarriers for Cancer Immunotherapy in Heterogeneous Tumor Microenvironments, Combining Immunogenic Cell Death Stimuli with Immune Modulatory Drugs

In addition to the contribution of cancer cells, the solid tumor microenvironment (TME) has a critical role in determining tumor expansion, antitumor immunity, and the response to immunotherapy. Understanding the details of the complex interplay between cancer cells and components of the TME provides an unprecedented opportunity to explore combination therapy for intervening in the immune landscape to improve immunotherapy outcome. One approach is the introduction of multifunctional nanocarriers, capable of delivering drug combinations that provide immunogenic stimuli for improvement of tumor antigen presentation, contemporaneous with the delivery of coformulated drug or synthetic molecules that provide immune danger signals or interfere in immune-escape, immune-suppressive, and T-cell exclusion pathways. This forward-looking review will discuss the use of lipid-bilayer-encapsulated liposomes and mesoporous silica nanoparticles for combination immunotherapy of the heterogeneous immune landscapes in pancreatic ductal adenocarcinoma and triple-negative breast cancer. We describe how the combination of remote drug loading and lipid bilayer encapsulation is used for the synthesis of synergistic drug combinations that induce immunogenic cell death, interfere in the PD-1/PD-L1 axis, inhibit the indoleamine-pyrrole 2,3-dioxygenase (IDO-1) immune metabolic pathway, restore spatial access to activated T-cells to the cancer site, or reduce the impact of immunosuppressive stromal components. We show how an integration of current knowledge and future discovery can be used for a rational approach to nanoenabled cancer immunotherapy.

Combinational Chemoimmunotherapy for Breast Cancer by Codelivery of Doxorubicin and PD-L1 siRNA Using a PAMAM-Incorporated Liposomal Nanoplatform

Chemoimmunotherapy can synergistically enhance the therapeutic effects and decrease the side effects by a combined method. However, the effective targeted codelivery of various chemotherapeutic agents and siRNAs remains challenging. Although nanomedicine-based chemoimmunotherapy has shown great potential in cancer treatment in recent years, further effort is needed to simplify the nanocarrier designs and maintain their effective functions. Here, we report a simple but robust multifunctional liposomal nanocarrier that contains a pH-sensitive liposome (LP) shell and a dendritic core for tumor-targeted codelivery of programmed cell death ligand 1 (PD-L1) siRNA and doxorubicin (DOX) (siPD-L1@PM/DOX/LPs). siPD-L1@PM/DOX/LPs had a suitable particle size and zeta potential, excellent stability in serum, and pH-sensitive drug release in vitro. They exhibited significant cell proliferation inhibition compared to free DOX and DOX-loaded LPs and could escape endosomes, effectively release siRNA into the cytoplasm of MCF-7 cells, and significantly reduce the PD-L1 expression on tumor cells. In vivo imaging confirmed high accumulation of siPD-L1@PM/DOX/LPs at the tumor site. More importantly, compared with siPD-L1@PM/LPs or DOX alone, siPD-L1@PM/DOX/LPs were more effective in inhibiting tumor growth and activating cytotoxic T cells in vivo. In conclusion, this nanocarrier may hold promise as a codelivery nanoplatform to improve the treatment of various solid tumors.

Mitochondria-targeted polymer-celastrol conjugate with enhanced anticancer efficacy

Celastrol, a natural triterpene extracted from traditional Chinese medicine, shows anticancer effects on various cancer cells. However, its poor water-solubility, short plasma half-life, and high systemic toxicity impede its applications in vivo, necessitating a stable drug delivery system to overcome these critical drawbacks. We present here a block copolymer, poly(2-(N-oxide-N,N-dimethylamino)ethyl methacrylate)-block-poly(2-hydroxyethyl methacrylate) (OPDMA-HEMA), as the carrier for celastrol delivery. The amphiphilic polymer-celastrol conjugate can self-assemble into nanoparticles in aqueous solutions. The OPDMA outer shell confers the nanoparticles with improved pharmacokinetics and efficient mitochondria targeting capacity, and profoundly potentiates celastrol's induction of immunogenic cell death, which collectively contribute to the enhanced therapeutic effects of celastrol in vivo. This mitochondria-targeted polymer-celastrol conjugate may promise the applications of celastrol in cancer treatment.

Multifunctional Size-Expandable Nanomedicines Enhance Tumor Accumulation and Penetration for Synergistic Chemo-Photothermal Therapy

Size expansion can effectively improve tumor accumulation of nanocarriers where precise control is required. A dual-responsive nanocarrier stimulated by both endogenous pH and exogenous heat stimuli can change its size. Herein, a nanoparticle composed of poly(N,N-diethyl acrylamide) (PDEAA) and poly(2-(diisopropylamino) ethyl methacrylate) (PDPA) is developed. The antitumor drug celastrol (CLT) and the photosensitizer indocyanine green (ICG) are then loaded in it to form CIPP. ICG generates heat under near-infrared (NIR) stimulation to kill tumor cells and enhance CIPP penetration. Meanwhile, CIPP expands in response to hyperthermia and acid tumor microenvironments, preventing itself from returning to the blood flow, thus accumulating in tumor sites. Ultimately, the acidic lysosomal environment in tumor cells disintegrates CIPP to release CLT, directly inducing immunogenic cell death and sensitizing tumor cells for hyperthermia by disrupting the interaction of heat shock protein 90 and P50cdc37. Most of the tumors in B16F10-bearing mice are eradicated after single laser irradiation. The dual-responsive CIPP with multiple functions and simple design displays a synergistic antitumor effect. This study provides a basis for developing size-expandable stimulus-responsive drug delivery systems against tumors.

Celastrol in cancer therapy: Recent developments, challenges and prospects

Cancer is one of the world's biggest healthcare burdens and despite the current advancements made in treatment plans, the outcomes for oncology patients have yet to reach their full potential. Hence, there is a pressing need to develop novel anti-cancer drugs. A popular drug class for research are natural compounds, due to their multi-targeting potential and enhanced safety profile. One such promising natural bioactive compound derived from a vine, Tripterygium wilfordii is celastrol. Pre-clinical studies revolving around the use of celastrol have revealed positive pharmacological activities in various types of cancers, thus suggesting the chemical's potential anti-cancerous effects. However, despite the numerous preclinical studies carried out over the past few decades, celastrol has not reached human trials for cancer. In this review, we summarize the mechanisms and therapeutic potentials of celastrol in treatment for different types of cancer. Subsequently, we also explore the possible reasons hindering its development for human use as cancer therapy, like its narrow therapeutic window and poor pharmacokinetic properties. Additionally, after critically analysing both in vitro and in vivo evidence, we discuss about the key pathways effected by celastrol and the suitable types of cancer that can be targeted by the natural drug, thus giving insight into future directions that can be taken, such as in-depth analysis and research of the druggability of celastrol derivatives, to aid the clinical translation of this promising anti-cancer lead compound.

Celastrol Modulates Multiple Signaling Pathways to Inhibit Proliferation of Pancreatic Cancer via DDIT3 and ATF3 Up-Regulation and RRM2 and MCM4 Down-Regulation

Background

Pancreatic cancer is one of the most serious and lethal human cancers with a snowballing incidence around the world. The natural product celastrol has also been widely documented as a potent anti-inflammatory, anti-angiogenic, and anti-oxidant.

Purpose

To elucidate the antitumor effect of celastrol on pancreatic cancer cells and its modulatory role on whole genome expression.

Methods

The antitumor activity of celastrol on a panel of pancreatic cancer cells has been evaluated by Sulforhodamine B assay. Caspase 3/7 and histone-associated DNA fragments assays were done for apoptosis measurement. Additionally, prostaglandin (PGE2) inhibition was evaluated. Moreover, a microarray gene expression profiling was carried out to detect possible key players that modulate the antitumor effects of celastrol on cells of pancreatic cancer.

Results

Our findings indicated that celastrol suppresses the cellular growth of pancreatic cancer cells, induces apoptosis, and inhibits PGE2 production. Celastrol modulated many signaling genes and its cytotoxic effect was mainly mediated via over-expression of ATF3 and DDIT3, and down-expression of RRM2 and MCM4.

Conclusion

The current study aims to be a starting point to generate a hypothesis on the most significant regulatory genes and for a full dissection of the celastrol possible effects on each single gene to prevent the pancreatic cancer growth.

Nanotechnology-Based Celastrol Formulations and Their Therapeutic Applications

Celastrol (also called tripterine) is a quinone methide triterpene isolated from the root extract of Tripterygium wilfordii (thunder god vine in traditional Chinese medicine). Over the past two decades, celastrol has gained wide attention as a potent anti-inflammatory, anti-autoimmune, anti-cancer, anti-oxidant, and neuroprotective agent. However, its clinical translation is very challenging due to its lower aqueous solubility, poor oral bioavailability, and high organ toxicity. To deal with these issues, various formulation strategies have been investigated to augment the overall celastrol efficacy in vivo by attempting to increase the bioavailability and/or reduce the toxicity. Among these, nanotechnology-based celastrol formulations are most widely explored by pharmaceutical scientists worldwide. Based on the survey of literature over the past 15 years, this mini-review is aimed at summarizing a multitude of celastrol nanoformulations that have been developed and tested for various therapeutic applications. In addition, the review highlights the unmet need in the clinical translation of celastrol nanoformulations and the path forward.

Doxorubicin and PD-L1 siRNA co-delivery with stem cell membrane-coated polydopamine nanoparticles for the targeted chemoimmunotherapy of PCa bone metastases

Programmed cell death ligand 1 (PD-L1) blockade has achieved great success in cancer immunotherapy. PD-L1 siRNA can restore the immune anti-tumor activity of T cells by downregulating the level of PD-L1 on tumor cells, but the efficiency of PD-1/PD-L1 monotherapy is relatively low. Doxorubicin (DOX) can induce tumor cell apoptosis, and then increase the release of tumor antigen. But the expression of PD-L1 in tumor tissues treated with DOX will be enhanced adaptively. Therefore, DOX combination with PD-L1 siRNA can produce a good synergistic anti-tumor effect. In this study, stem cell membrane (SCM) camouflaged polydopamine nanoparticles carrying DOX and PD-L1 siRNA (PDA-DOX/siPD-L1@SCM) were constructed for targeting prostate cancer (PCa) bone metastases. PDA-DOX/siPD-L1@SCM NPs could effectively enhance blood retention and improve accumulation at tumor sites. In vitro and in vivo studies demonstrated that PDA-DOX/siPD-L1@SCM NPs showed excellent performance in synergistic chemoimmunotherapy for PCa bone metastases. Hence, this study provided an effective strategy for developing biomimetic multifunctional nanoparticles for PCa bone metastasis treatment.