A Pt(IV) Pro-drug Preferentially Targets Indoleamine-2,3-dioxygenase, Providing Enhanced Ovarian Cancer Immuno-Chemotherapy

Platinum(IV) Complexes Trigger Death Receptors and Natural Killer Cells to Suppress Breast Cancer

Chemoimmunotherapy is an alternative treatment against cancers. Platinum(IV) complexes FMP and DFMP, coupling formononetin derivative as axial ligand(s), were designed to suppress triple-negative breast cancer (TNBC) by activating death receptors (DRs) and natural killer (NK) cells. These complexes show great potential to overcome the resistance of TNBC to chemotherapy by inducing both intrinsic and extrinsic apoptosis in cancer cells. Particularly, FMP with one axial formononetin derivative not only induced the caspase-3-dependent intrinsic apoptosis but also upregulated the expression of DRs and caspase-8, triggered the extrinsic apoptosis, and enhanced the cytotoxic ability of NK92 cells. Moreover, FMP increased the release of granzyme B, restrained the proliferation and differentiation of myeloid-derived suppressor cells, and the secretion of IL-10, thus inhibiting the TNBC in vitro and in vivo. The results demonstrate that FMP overcomes the chemoresistance and immune escape of TNBC through a new mechanism involving the synergy of chemotherapy and immunotherapy.

Targeting matrix metalloproteinases activating and indoleamine 2,3-dioxygenase suppression for triple-negative breast cancer multimodal therapy

The dense extracellular matrix (ECM) and immunosuppressive tumor microenvironment represent two major challenges in the treatment of triple-negative breast cancer (TNBC). To address these obstacles, this study has developed a polymer micelle (NTP) for ECM remodeling and mitigation the immune microenvironment, based on activating endogenous matrix metalloproteinases (MMP) and suppression indoleamine 2,3-dioxygenase (IDO). Through self-assembly technology, this micelle effectively incorporates chemotherapy drugs (camptothecin (CPT) and cinnamaldehyde (CA)), reactive oxygen species (ROS) stimulants, nitric oxide (NO) donor and IDO inhibitor (NLG919), where CPT and CA have been reported to help generating ROS mainly in the mitochondrion. The guanidine group of poly-L-arginine (PArg), as an NO donor, can react with ROS to generate NO. The micelles aim to achieve significant therapeutic outcomes through robust drug penetration and anti-tumor immunity in multimodal therapy. They exhibit remarkable tumor tissue penetration ability, facilitating precise targeting of mitochondria and ROS production stimulation. Building upon this therapeutic foundation, the micellar system achieves in situ NO release, which effectively degrades the ECM through the activation of MMPs, while simultaneously promoting tumor cells apoptosis. Furthermore, the encapsulated NLG919 can be released and effectively mitigating the immunosuppressive milieu and triggering anti-tumor immune responses. Experimental results demonstrate that the micelles exhibit significant anti-tumor effects both in vitro and in vivo, accompanied by favorable biocompatibility. This study provides new insights into the application of subcellular targeting drug delivery systems in TNBC treatment, potentially heralding a new breakthrough in TNBC therapy.

Novel Indoleamine-2,3-Dioxygenase-Targeted Pt(IV) Prodrugs Regulate the Tumor Immune Microenvironment to Achieve Chemoimmunotherapy In Vitro and In Vivo

Convincing evidence revealed that some platinum-based drugs could stimulate immunological recognition, thereby inducing immunogenic cell death (ICD). Indoleamine-2,3-dioxygenase (IDO) is overexpressed in tumors, which caused exhaustion of tryptophan (T-cell energy) and constructed an immunosuppressive tumor microenvironment. Herein, considering IDO inhibition to improve chemotherapy, a series of IDOi-Pt(IV) prodrugs were designed to not only target DNA and IDO but also facilitate tumor-antigen exposure and immunomodulation. The optimal IDOi-Pt(IV) prodrugs (named compound 10) significantly enhanced intracellular accumulation 22.4-fold and cytotoxicity 61.75-fold superior to cisplatin in HeLa cells. Moreover, immunofluorescence and enzyme-linked immunosorbent assays revealed that 10 induced reactive oxygen species-mediated endoplasmic reticulum stress and secretion of damage-associated molecular patterns, thereby presenting ICD effects. Molecular docking, enzyme inhibition, and Western blot assays demonstrated that 10 could effectively inhibit IDO1 and reverse immunosuppression, as further verified by mixed leukocyte reactions. In vivo tests showed that 10 exhibited high-efficiency and low-toxicity antitumor effects compared to cisplatin, presenting successful chemoimmunotherapy.

Strategies for the development of metalloimmunotherapies

Metal ions play crucial roles in the regulation of immune pathways. In fact, metallodrugs have a long record of accomplishment as effective treatments for a wide range of diseases. Here we argue that the modulation of interactions of metal ions with molecules and cells involved in the immune system forms the basis of a new class of immunotherapies. By examining how metal ions modulate the innate and adaptive immune systems, as well as host-microbiota interactions, we discuss strategies for the development of such metalloimmunotherapies for the treatment of cancer and other immune-related diseases.

Engineering Novel Amphiphilic Platinum(IV) Complexes to Co-Deliver Cisplatin and Doxorubicin

In this study, we report a novel platinum-doxorubicin conjugate that demonstrates superior therapeutic indices to cisplatin, doxorubicin, or their combination, which are commonly used in cancer treatment. This new molecular structure (1) was formed by conjugating an amphiphilic Pt(IV) prodrug of cisplatin with doxorubicin. Due to its amphiphilic nature, the Pt(IV)-doxorubicin conjugate effectively penetrates cell membranes, delivering both cisplatin and doxorubicin payloads intracellularly. The intracellular accumulation of these payloads was assessed using graphite furnace atomic absorption spectrometry and fluorescence imaging. Since the therapeutic effects of cisplatin and doxorubicin stem from their ability to target nuclear DNA, we hypothesized that the amphiphilic Pt(IV)-doxorubicin conjugate (1) would effectively induce nuclear DNA damage toward killing cancer cells. To test this hypothesis, we used flow the cytometric analysis of phosphorylated H2AX (γH2AX), a biomarker of nuclear DNA damage. The Pt(IV)-doxorubicin conjugate (1) markedly induced γH2AX in treated MDA-MB-231 breast cancer cells, showing higher levels than cells treated with either cisplatin or doxorubicin alone. Furthermore, MTT cell viability assays revealed that the enhanced DNA-damaging capability of complex 1 resulted in superior cytotoxicity and selectivity against human cancer cells compared to cisplatin, doxorubicin, or their combination. Overall, the development of this amphiphilic Pt(IV)-doxorubicin conjugate represents a new form of combination therapy with improved therapeutic efficacy.

Alendronate PtIV Prodrug Amphiphile for Enhanced Chemotherapy Targeting and Bone Destruction Inhibition in Osteosarcoma

Chemotherapy remains the primary treatment method for osteosarcoma after surgery. However, the lack of selectivity of chemotherapy for osteosarcoma leads to unpredictable therapeutic effects, undesirable side effects, and drug resistance. A platinum(IV) (PtIV ) prodrug amphiphile (ALN-PtIV -Lipo) covalently bound to alendronate (ALN) and a lipid tail is designed to overcome these limitations. ALN-PtIV -Lipo can self-assemble into PtIV lipid nanoparticles (APtIV ) for osteosarcoma targeting chemotherapy and bone destruction inhibition. It is demonstrated that APtIV achieved an eightfold increase in the eradication of osteosarcoma cells compared to cisplatin and threefold selective inhibition of osteosarcoma cells over breast cancer cells via APtIV in vitro. After intravenous injection, APtIV effectively accumulates at the osteosarcoma site in vivo, resulting in significantly suppressed primary osteosarcoma growth, and alleviation of bone destruction. Therefore, APtIV delivers a promising solution for enhanced chemotherapy targeting and bone destruction inhibition in osteosarcoma.

Development of Platinum Complexes for Tumor Chemoimmunotherapy

Platinum complexes are potential antitumor drugs in chemotherapy. Their impact on tumor treatment could be greatly strengthened by combining with immunotherapy. Increasing evidences indicate that the antitumor activity of platinum complexes is not limited to chemical killing effects, but also extends to immunomodulatory actions. This review introduced the general concept of chemoimmunotherapy and summarized the progress of platinum complexes as chemoimmunotherapeutic agents in recent years. Platinum complexes could be developed into inducers of immunogenic cell death, blockers of immune checkpoint, regulators of immune signaling pathway, and modulators of tumor immune microenvironment, etc. The synergy between chemotherapeutic and immunomodulatory effects reinforces the antitumor activity of platinum complexes, and helps them circumvent the drug resistance and systemic toxicity. The exploration of platinum complexes for chemoimmunotherapy may create new opportunities to revive the discovery of metal anticancer drugs.

Platinum-Based Twin Drug Modulates Tumor-Infiltrating Immune Cells to Improve Immune Checkpoint Blockade Therapy

Chemoimmunotherapy is an area of active research and development with a growing body of evidence supporting its potential benefits for the treatment of cancer. However, chemotherapy components of chemoimmunotherapy have several limitations, including systemic toxicity and poor performance in reversing the immunosuppressive tumor microenvironment. Here, we designed a twin drug, MROP, complexed with all-trans retinoic acid and oxaliplatin, and showed that the twin drug significantly enhanced the synergetic therapeutic efficacy with anti-PD-1 in a colorectal cancer mouse model. We demonstrated by mechanistic analyses of tumor tissue that the combination of anti-PD-1 and MROP induced immunogenic cell death and regulated tumor-infiltrating immune cells, including the polarization of tumor-associated macrophages toward type 1, a reduction in myeloid-derived suppressor cells, and a significant increase in the proportion of T cells, particularly CD8+ T cells. This paper provides a promising strategy for cancer treatment and new insight into the mechanism of chemoimmunotherapy.

Platinum Twin and Triplet Drugs Improve Chemoimmunotherapy

Several chemoimmunotherapy regimens have been approved by the U.S. FDA, verifying the great clinical value and potential of the strategy. However, the immunomodulatory function of chemotherapy was insufficient, which did not provide extra overall survival benefits, especially in a head-to-head comparison of chemoimmunotherapy versus immunotherapy. Here, we engineered twin and triplet drugs derived from an immunogenic chemotherapeutic drug (oxaliplatin) and small-molecule inhibitors of negative immunoregulation pathways (COX2 and IDO) in tumors as an improved chemotherapeutic component within chemoimmunotherapy. The twin and triplet drugs exhibited significantly improved synergy with anti-PD-1 in a CT26 colorectal mouse tumor model. Mechanistic analyses revealed that the drug induced immunogenic cell death and restored tumor immune microenvironment toward tumor clearance in vivo, resulting in a great decrease in tumor-infiltrating Tregs and an increase in the CD8+ T/Treg ratio when combined with anti-PD-1. Our work expands the application of platinum twin drugs in combination with an immune checkpoint blockade.

Exploring the Impact of Head Group Modifications on the Anticancer Activities of Fatty-Acid-like Platinum(IV) Prodrugs: A Structure-Activity Relationship Study

We conducted the first comprehensive investigation on the impact of head group modifications on the anticancer activities of fatty-acid-like Pt(IV) prodrugs (FALPs), which are a class of platinum-based metallodrugs that target mitochondria. We created a small library of FALPs (1-9) with diverse head group modifications. The outcomes of our study demonstrate that hydrophilic modifications exclusively enhance the potency of these metallodrugs, whereas hydrophobic modifications significantly decrease their cytotoxicity. To further understand this interesting structure-activity relationship, we chose two representative FALPs (compounds 2 and 7) as model compounds: one (2) with a hydrophilic polyethylene glycol (PEG) head group, and the other (7) with a hydrophobic hydrocarbon modification of the same molecular weight. Using these FALPs, we conducted a targeted investigation on the mechanism of action. Our study revealed that compound 2, with hydrophilic modifications, exhibited remarkable penetration into cancer cells and mitochondria, leading to subsequent mitochondrial and DNA damage, and effectively eradicating cancer cells. In contrast, compound 7, with hydrophobic modifications, displayed a significantly lower uptake and weaker cellular responses. The collective results present a different perspective, indicating that increased hydrophobicity may not necessarily enhance cellular uptake as is conventionally believed. These findings provide valuable new insights into the fundamental principles of developing metallodrugs.

Synthesis and Biological Evaluation of Novel 2-Amino-1,4-Naphthoquinone Amide-Oxime Derivatives as Potent IDO1/STAT3 Dual Inhibitors with Prospective Antitumor Effects

Indoleamine-2,3-dioxygenase 1 (IDO1) and signal transducer and activator of transcription 3 (STAT3) have emerged as significant targets in the tumor microenvironment for cancer therapy. In this study, we synthesized three novel 2-amino-1,4-naphthoquinone amide-oxime derivatives and identified them as dual inhibitors of IDO1 and STAT3. The representative compound NK3 demonstrated effective binding to IDO1 and exhibited good inhibitory activity (hIDO1 IC50 = 0.06 μM), leading to its selection for further investigation. The direct interactions between compound NK3 and IDO1 and STAT3 proteins were confirmed through surface plasmon resonance analysis. A molecular docking study of compound NK3 revealed key interactions between NK3 and IDO1, with the naphthoquinone-oxime moiety coordinating with the heme iron. In the in vitro anticancer assay, compound NK3 displayed potent antitumor activity against selected cancer cell lines and effectively suppressed nuclear translocation of STAT3. Moreover, in vivo assays conducted on CT26 tumor-bearing Balb/c mice and an athymic HepG2 xenograft model revealed that compound NK3 exhibited potent antitumor activity with low toxicity relative to 1-methyl-L-tryptophan (1-MT) and doxorubicin (DOX). Overall, these findings provided evidence that the dual inhibitors of IDO1 and STAT3 may offer a promising avenue for the development of highly effective drug candidates for cancer therapy.

Supramolecular platinum complexes for cancer therapy

The rise of supramolecular chemistry offers new tools to design therapeutics and delivery platforms for biomedical applications. This review aims to highlight the recent developments that harness host-guest interactions and self-assembly to design novel supramolecular Pt complexes as anticancer agents and drug delivery systems. These complexes range from small host-guest structures to large metallosupramolecules and nanoparticles. These supramolecular complexes integrate the biological properties of Pt compounds and novel supramolecular structures, which inspires new designs of anticancer approaches that overcome problems in conventional Pt drugs. Based on the differences in Pt cores and supramolecular structures, this review focuses on five different types of supramolecular Pt complexes, and they include host-guest complexes of the FDA-approved Pt(II) drugs, supramolecular complexes of nonclassical Pt(II) metallodrugs, supramolecular complexes of fatty acid-like Pt(IV) prodrugs, self-assembled nanotherapeutics of Pt(IV) prodrugs, and self-assembled Pt-based metallosupramolecules.

Blocking xCT and PI3K/Akt pathway synergized with DNA damage of Riluzole-Pt(IV) prodrugs for cancer treatment

Cancer treatment requires the participation of multiple targets/pathways, and single approach is hard to effectively curb the proliferation and metastasis of carcinoma cells. In this work, we conjugated FDA-approved riluzole and platinum(II) drugs into a series of unreported riluzole-Pt(IV) compounds, which were designed to simultaneously target DNA, the solute carrier family 7 member 11 (SLC7A11, xCT), and the human ether a go-go related gene 1 (hERG1), to exert synergistic anticancer effect. Among them, c,c,t-[PtCl₂(NH₃)₂(OH)(glutarylriluzole)] (compound 2) displayed excellent antiproliferative activity with IC₅₀ value of 300-times lower than that of cisplatin in HCT-116, and optimal selectivity index between carcinoma and human normal liver cells (LO2). Mechanism studies indicated that compound 2 released riluzole and active Pt(II) species after entering cells to exhibit a prodrug behavior against cancer, which obviously increased DNA-damage and cell apoptosis, as well as suppressed metastasis in HCT-116. Compound 2 persisted in the xCT-target of riluzole and blocked the biosynthesis of glutathione (GSH) to trigger oxidative stress, which could boost the killing to cancer cells and reduce Pt-drug resistance. Meanwhile, compound 2 significantly inhibited invasion and metastasis of HCT-116 cells by targeting hERG1 to interrupt the phosphorylation of phosphatidylinositide 3-kinases/proteinserine-threonine kinase (PI3K/Akt), and reverse epithelial-mesenchymal transformation (EMT). Based on our results, the riluzole-Pt(IV) prodrugs studied in this work could be regarded as a new class of very promising candidates for cancer treatment compared to traditional platinum drugs.

Smart Nanosensitizers for Activatable Sono-Photodynamic Immunotherapy of Tumors by Redox-Controlled Disassembly

Tumor-targeted and stimuli-activatable nanosensitizers are highly desirable for cancer theranostics. However, designing smart nanosensitizers with multiple imaging signals and synergistic therapeutic activities switched on is challenging. Herein, we report tumor-targeted and redox-activatable nanosensitizers (1-NPs) for sono-photodynamic immunotherapy of tumors by molecular co-assembly and redox-controlled disassembly. 1-NPs show a high longitudinal relaxivity (r₁ =18.7±0.3 mM^-1  s^-1 ), but "off" dual fluorescence (FL) emission (at 547 and 672 nm), "off" sono-photodynamic therapy and indoleamine 2,3-dioxygenase 1 (IDO1) inhibition activities. Upon reduction by glutathione (GSH), 1-NPs rapidly disassemble and remotely release small molecules 2-Gd, Zn-PPA-SH and NLG919, concurrently switching on (1) dual FL emission, (2) sono-photodynamic therapy and (3) IDO1 inhibition activities. After systemic injection, 1-NPs are effective for bimodal FL and magnetic resonance (MR) imaging-guided sono-photodynamic immunotherapy of orthotropic breast and brain tumors in mice under combined ultrasound (US) and 671-nm laser irradiation.

Combination of DNA Damage, Autophagy, and ERK Inhibition: Novel Evodiamine-Inspired Multi-Action Pt(IV) Prodrugs with High-Efficiency and Low-Toxicity Antitumor Activity

Exploring multi-targeting chemotherapeutants with advantages over single-targeting agents and drug combinations is of great significance in drug discovery. Herein, we employed phytogenic evodiamine (EVO) and conventional Pt(II) drugs to design and synthesize multi-target EVO-Pt(IV) anticancer prodrugs (4-14). Among them, compound 10 exhibited a 118-fold enhancement in the IC₅₀ value compared to cisplatin and low toxicity to normal cells. Further studies proved that 10 significantly enhanced intracellular Pt accumulation and DNA damage, perturbed mitochondrial membrane potential, inhibited cell migration and invasion, upregulated reactive oxygen species levels, and induced apoptosis and autophagic cell death. Molecular docking assay revealed that 10 fits perfectly into the extracellular signal-regulated protein kinase (ERK)-1 pocket, which was verified to produce profound ERK suppression. Most strikingly, compound 10 exhibited superior in vivo antitumor efficiency and effectively attenuated systemic toxicity. Our results emphasize that functionalizing platinum drugs with the multi-target EVO could generate synergistically excellent anticancer activity with low toxicity and decreased resistance, which may represent a brand-new cancer therapy modality.

Impact of Hydrophobic Chains in Five-Coordinate Glucoconjugate Pt(II) Anticancer Agents

This study describes new platinum(II) cationic five-coordinate complexes (1-R,R') of the formula [PtR(NHC)(dmphen)(ethene)]CF₃SO₃ (dmphen = 2,9-dimethyl-1,10-phenanthroline), containing in their axial positions an alkyl group R (methyl or octyl) and an imidazole-based NHC-carbene ligand with a substituent R' of variable length (methyl or octyl) on one nitrogen atom. The Pt-carbene bond is stable both in DMSO and in aqueous solvents. In DMSO, a gradual substitution of dmphen and ethene is observed, with the formation of a square planar solvated species. Octanol/water partitioning studies have revealed the order of hydrophobicity of the complexes (1-Oct,Me > 1-Oct,Oct > 1-Me,Oct > 1-Me,Me). Their biological activity was investigated against two pairs of cancer and non-cancer cell lines. The tested drugs were internalized in cancer cells and able to activate the apoptotic pathway. The reactivity of 1-Me,Me with DNA and protein model systems was also studied using UV-vis absorption spectroscopy, fluorescence, and X-ray crystallography. The compound binds DNA and interacts in various ways with the model protein lysozyme. Remarkably, structural data revealed that the complex can bind lysozyme via non-covalent interactions, retaining its five-coordinate geometry.

Blood Components as Carriers for Small-Molecule Platinum Anticancer Drugs

The efficacy of platinum drugs is limited by severe side effects, drug resistance, and poor pharmacokinetic properties. Utilizing long-lasting blood components as drug carriers is a promising strategy to improve the circulation half-lives and tumor accumulation of platinum drugs. Non-immunogenic blood cells such as erythrocytes and blood proteins such as albumins, which have long lifespans, are suitable for the delivery of platinum drugs. In this concept, we briefly summarize the strategies of applying blood components as promising carriers to deliver small-molecule platinum drugs for cancer treatment. Examples of platinum drugs that are encapsulated, non-covalently attached, and covalently bound to erythrocytes and plasma proteins such as albumin and apoferritin are introduced. The potential methods to increase the stability of platinum-based thiol-maleimide conjugates involved in these delivery systems are also discussed. This concept may enlighten researchers with more ideas on the future development of novel platinum drugs that have excellent pharmacokinetic properties and antitumor performance in vivo.

Carboxylate-Capped Analogues of Ru265 Are MCU Inhibitor Prodrugs

The mitochondrial calcium uniporter (MCU) is a transmembrane protein that resides on the inner membrane of the mitochondria and mediates calcium uptake into this organelle. Given the critical role of mitochondrial calcium trafficking in cellular function, inhibitors of this channel have arisen as tools for studying the biological relevance of this process and as potential therapeutic agents. In this study, four new analogues of the previously reported Ru-based MCU inhibitor [ClRu(NH3)4(μ-N)Ru(NH3)4Cl]Cl3 (Ru265) are reported. These compounds, which bear axial carboxylate ligands, are of the general formula [(RCO2)Ru(NH3)4(μ-N)Ru(NH3)4(O2CR)]X3, where X = NO3- or CF3SO3- and R = H (1), CH3 (2), CH2CH3 (3), and (CH2)2CH3 (4). These complexes were fully characterized by IR spectroscopy, NMR spectroscopy, and elemental analysis. X-ray crystal structures of 1 and 3 were obtained, revealing the expected presence of both the linear Ru(μ-N)Ru core and axial formate and propionate ligands. The axial carboxylate ligands of complexes 1-4 are displaced by water in buffered aqueous solution to give the aquated compound Ru265'. The kinetics of these processes were measured by 1H NMR spectroscopy, revealing half-lives that span 5.9-9.9 h at 37 °C. Complex 1 with axial formate ligands underwent aquation approximately twice as fast as the other compounds. In vitro cytotoxicity and mitochondrial membrane potential measurements carried out in HeLa and HEK293T cells demonstrated that none of these four complexes negatively affects cell viability or mitochondrial function. The abilities of 1-4 to inhibit mitochondrial calcium uptake in permeabilized HEK293T cells were assessed and compared to that of Ru265. Fresh solutions of 1-4 are approximately 2-fold less potent than Ru265 with IC50 values in the range of 14.7-19.1 nM. Preincubating 1-4 in aqueous buffers for longer time periods to allow for the aquation reactions to proceed increases their potency of mitochondrial uptake inhibition to match that of Ru265. This result indicates that 1-4 are aquation-activated prodrugs of Ru265'. Finally, 1-4 were shown to inhibit mitochondrial calcium uptake in intact, nonpermeabilized cells, revealing their value as tools and potential therapeutic agents for mitochondrial calcium-related disorders.

Metabolic reprogramming of the tumor immune microenvironment in ovarian cancer: A novel orientation for immunotherapy

Ovarian cancer is the most lethal gynecologic tumor, with the highest mortality rate. Numerous studies have been conducted on the treatment of ovarian cancer in the hopes of improving therapeutic outcomes. Immune cells have been revealed to play a dual function in the development of ovarian cancer, acting as both tumor promoters and tumor suppressors. Increasingly, the tumor immune microenvironment (TIME) has been proposed and confirmed to play a unique role in tumor development and treatment by altering immunosuppressive and cytotoxic responses in the vicinity of tumor cells through metabolic reprogramming. Furthermore, studies of immunometabolism have provided new insights into the understanding of the TIME. Targeting or activating metabolic processes of the TIME has the potential to be an antitumor therapy modality. In this review, we summarize the composition of the TIME of ovarian cancer and its metabolic reprogramming, its relationship with drug resistance in ovarian cancer, and recent research advances in immunotherapy.

Bioengineered immunomodulatory organelle targeted nanozymes for photodynamic immunometabolic therapy

Intelligent nanomedicines integrated with stimuli-responsive components enable on-demand customizable treatment options which would improve therapeutic outcome and reduce systemic toxicity. In this work, we explore the synergistic therapeutic potential of photodynamic therapy and immunometabolic modulation to achieve tumour regression and to trigger an adaptive immunity to prevent tumour recurrence. The therapeutic potential of the fabricated Bioengineered Immunomodulatory Organelle targeted Nanozymes (BIONs) was tested on 3D printed mini-brains which could effectively recapitulate the biologically relevant interactions between glioblastoma cells and macrophages. In the presence of glioblastoma organotypic brain slices, activated BIONs upregulated the cell surface expression of CD86, a costimulatory molecule and CD83, maturation marker, on monocyte derived dendritic cells, suggesting its ability to elicit a strong immune response. Furthermore, the antigen pulsed dendritic cells by chemotaxis and transendothelial migration readily relocate into the draining lymph node where they present the antigenic cargo to enable the proliferation of T lymphocytes. The stealth and tunable catalytic activity of BIONs prevent ROS mediated diseases such as acute kidney injury by providing environment dependent protection without compromising on its promising anti-cancer activity.

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

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

Multifunctional Nanosystems Powered Photodynamic Immunotherapy

Photodynamic Therapy (PDT) with the intrinsic advantages including non-invasiveness, spatiotemporal selectivity, low side-effects, and immune activation ability has been clinically approved for the treatment of head and neck cancer, esophageal cancer, pancreatic cancer, prostate cancer, and esophageal squamous cell carcinoma. Nevertheless, the PDT is only a strategy for local control of primary tumor, that it is hard to remove the residual tumor cells and inhibit the tumor metastasis. Recently, various smart nanomedicine-based strategies are developed to overcome the barriers of traditional PDT including the drawbacks of traditional photosensitizers, limited tissue penetrability of light, inefficient induction of tumor cell death and tumor resistance to the therapy. More notably, a growing number of studies have focused on improving the therapeutic efficiency by eliciting host immune system with versatile nanoplatforms, which heralds a broader clinical application prospect of PDT in the future. Herein, the pathways of PDT induced-tumor destruction, especially the host immune response is summarized, and focusing on the recent progress of nanosystems-enhanced PDT through eliciting innate immunity and adaptive immunity. We expect it will provide some insights for conquering the drawbacks current PDT and expand the range of clinical application through this review.

Application of lipid nanovesicle drug delivery system in cancer immunotherapy

Immunotherapy has gradually emerged as the most promising anticancer therapy. In addition to conventional anti-PD-1/PD-L1 therapy, anti-CTLA-4 therapy, CAR-T therapy, etc., immunotherapy can also be induced by stimulating the maturation of immune cells or inhibiting negative immune cells, regulating the tumor immune microenvironment and cancer vaccines. Lipid nanovesicle drug delivery system includes liposomes, cell membrane vesicles, bacterial outer membrane vesicles, extracellular vesicles and hybrid vesicles. Lipid nanovesicles can be used as functional vesicles for cancer immunotherapy, and can also be used as drug carriers to deliver immunotherapy drugs to the tumor site for cancer immunotherapy. Here, we review recent advances in five kinds of lipid nanovesicles in cancer immunotherapy and assess the clinical application prospects of various lipid nanovesicles, hoping to provide valuable information for clinical translation in the future.

Tandem Chemoimmunotherapy by a Cascade-Responsive Molecular Prodrug

The limited therapeutic effects of immunotherapy for most types of cancer stimulates the pursuit for efficient methods to improve its response rate. Herein we report the design and synthesis of a cascade-responsive molecular prodrug for tandem chemoimmunotherapy. This molecular prodrug first releases doxorubicin (DOX) in the mildly acidic tumor microenvironment (TME) to induce immunogenic cell death (ICD) of tumor cells. Caspase 3/7 released during tumor cell apoptosis liberates NLG919 from the prodrug, which inhibits the activity of indoleamine 2,3-dioxygenase (IDO) and results in relief of TME immunosuppression. Meanwhile, tumor-associated antigens and immune stimulatory cytokines released during ICD activate the immune response against the tumor, leading to synergistic chemoimmunotherapy. The efficacy of this prodrug is validated by in vitro and in vivo experiments, demonstrating the success of this strategy for cancer treatment.

Epigenetic Platinum Complexes Breaking the "Eat Me/Don't Eat Me" Balance for Enhanced Cancer Chemoimmunotherapy

Platinum complexes, despite being the most successful organometallic anticancer chemotherapy drugs, still suffer from serious side effects and therapy resistance. Inspired by the immunomodulation effect of platinum drugs, an epigenetic platinum(IV) complex was synthesized for enhanced cancer chemoimmunotherapy by conjugating oxidized oxaliplatin (OXA) with 2-bromo-1-(3,3-dinitro-1-azetidinyl)ethenone (RRx-001), the latter of which as a nitric oxide (NO) donor is also an epigenetic agent. The obtained complex (named OXA-NO) could significantly increase the level of "eat me" signal CRT expression and decrease the level of "don't eat me" signal CD47 expression on cancer cell membranes to promote their phagocytosis by macrophages. In addition, OXA-NO could release nitric oxide to trigger the transformation of pro-tumorigenic M2-type macrophages into antitumor M1-type macrophages within the tumor to reverse the immunosuppressive tumor microenvironment. Compared to commercial OXA, OXA-NO exhibited much stronger tumor growth inhibition ability and was much better tolerated, with obviously weakened side effects observed in spleen, lung, and kidneys. Therefore, this epigenetic platinum(IV) complex that exhibits excellent therapeutic efficacy and safety has great potential in the clinic.

[12]aneN3-Conjugated AIEgens with Two-Photon Imaging Property for Synergistic Gene/Photodynamic Therapy in Vitro and in Vivo

Six amphiphiles (TTC-L-M-1/2/3/4/5/6), each consisting of hydrophilic macrocyclic polyamine triazole-[12]aneN3 (M) and hydrophobic photosensitizer tetraphenylethenethiophene modified cyanoacrylate (TTC) moiety linked with alkyl chains (L), have been designed and synthesized for...

Development of a series of flurbiprofen and zaltoprofen platinum(IV) complexes with anti-metastasis competence targeting COX-2, PD-L1 and DNA

To develop new anti-metastasis chemotherapeutic drugs, a series of flurbiprofen (FLP) and zaltoprofen (ZTP) platinum(IV) complexes targeting COX-2, PD-L1 and DNA were prepared and investigated. Complex 2 with dual FLP...

Ptxplatin: a multifunctional Pt(iv) antitumor prodrug

Ptxplatin, comprising paclitaxel and cisplatin, intervened in several cellular processes including the p53 apoptosis pathway, mitochondrial damage and ER stress to kill cancer cells.

A dual-responsive doxorubicin-indoximod conjugate for programmed chemoimmunotherapy

Herein we report a dual-responsive doxorubicin–indoximod conjugate (DOXIND) for programmed chemoimmunotherapy. This conjugate is able to release doxorubicin and indoximod upon exposure to appropriate stimuli for synergistic chemotherapy and immunotherapy, respectively. We demonstrate its promoting effects on immune response and inhibiting effects on tumor growth through a series of in vitro and in vivo experiments.

A dual-responsive doxorubicin–indoximod conjugate was developed, which allows for sequential on-demand release of doxorubicin and indoximod for programmed chemoimmunotherapy.

Breakdown of chemo-immune resistance by a TDO2-targeted Pt(IV) prodrug via attenuating endogenous Kyn-AhR-AQP4 metabolic circuity and TLS-promoted genomic instability

A tryptophan-2,3-dioxygenase 2 (TDO2)-targeted Pt(IV) prodrug, DN604-TDOi, was designed to prove that the multi-action compound could overcome drug resistance and relieve immunosuppression via introducing a TDO2 inhibitor to the axial position of a six-coordinate Pt(IV) hybrid. Several in vitro biological studies on cisplatin-resistant NSCLC cancer cells suggested that TDO2-targeted Pt(IV) prodrug could combat cisplatin resistance via influencing TDO2-kynurenine (Kyn)-aryl hydrocarbon receptor (AhR)-Aquaporin-4 (AQP4) metabolic circuity and AhR-human DNA polymerase (hpol) κ-induced translesion DNA synthesis (TLS) genomic instability, which are positive in drug-resistant human tumors associated with malignant progression and poor survival. Remarkably, we observed that DN604-TDOi could inhibit TDO2-mediated constitutive Kyn-AhR-AQP4 signaling pathway and suppress hpol κ expression, leading to potential decrease of cell motility and genomic instability in A549/cDDP cells. It was confirmed that TDO2-targeted Pt(IV) prodrug could harness Kyn-AhR-AQP4 metabolic circuitry and TLS genomic instability, exerting antitumor effects in C57BL6 but not TDO2^-/- mice. Moreover, the Pt(IV) prodrug improved the intratumoral infiltration of T_eff cells and reduced the recruitment of T_reg cells. The results provided compelling preclinical evidence that TDO2-targeted Pt(IV) prodrug could abrogate immune chemotherapeutic resistance via decaying TDO2-mediated Kyn-AhR-AQP4 immunosuppression and AhR-hpol κ-induced TLS genomic instability, underscoring the development of a novel Pt(IV)-based candidate as a potent immunotherapeutic agent for chemo-immune resistance prevention.

Structure-Activity Relationships of Triple-Action Platinum(IV) Prodrugs with Albumin-Binding Properties and Immunomodulating Ligands

Chemotherapy with platinum complexes is essential for clinical anticancer therapy. However, due to side effects and drug resistance, further drug improvement is urgently needed. Herein, we report on triple-action platinum(IV) prodrugs, which, in addition to tumor targeting via maleimide-mediated albumin binding, release the immunomodulatory ligand 1-methyl-d-tryptophan (1-MDT). Unexpectedly, structure-activity relationship analysis showed that the mode of 1-MDT conjugation distinctly impacts the reducibility and thus activation of the prodrugs. This in turn affected ligand release, pharmacokinetic properties, efficiency of immunomodulation, and the anticancer activity in vitro and in a mouse model in vivo. Moreover, we could demonstrate that the design of albumin-targeted multi-modal prodrugs using platinum(IV) is a promising strategy to enhance the cellular uptake of bioactive ligands with low cell permeability (1-MDT) and to improve their selective delivery into the malignant tissue. This will allow tumor-specific anticancer therapy supported by a favorably tuned immune microenvironment.

Metal- and metalloid-based compounds to target and reverse cancer multidrug resistance

Drug resistance remains the major cause of cancer treatment failure especially at the late stage of the disease. However, based on their versatile chemistry, metal and metalloid compounds offer the possibility to design fine-tuned drugs to circumvent and even specifically target drug-resistant cancer cells. Based on the paramount importance of platinum drugs in the clinics, two main areas of drug resistance reversal strategies exist: overcoming resistance to platinum drugs as well as multidrug resistance based on ABC efflux pumps. The current review provides an overview of both aspects of drug design and discusses the open questions in the field. The areas of drug resistance covered in this article involve: 1) Altered expression of proteins involved in metal uptake, efflux or intracellular distribution, 2) Enhanced drug efflux via ABC transporters, 3) Altered metabolism in drug-resistant cancer cells, 4) Altered thiol or redox homeostasis, 5) Altered DNA damage recognition and enhanced DNA damage repair, 6) Impaired induction of apoptosis and 7) Altered interaction with the immune system. This review represents the first collection of metal (including platinum, ruthenium, iridium, gold, and copper) and metalloid drugs (e.g. arsenic and selenium) which demonstrated drug resistance reversal activity. A special focus is on compounds characterized by collateral sensitivity of ABC transporter-overexpressing cancer cells. Through this approach, we wish to draw the attention to open research questions in the field. Future investigations are warranted to obtain more insights into the mechanisms of action of the most potent compounds which target specific modalities of drug resistance.

Self-delivery oxidative stress amplifier for chemotherapy sensitized immunotherapy

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

Plasmon-Driven Catalytic Chemotherapy Augments Cancer Immunotherapy through Induction of Immunogenic Cell Death and Blockage of IDO Pathway

Clinical trials confirm the combination of indoleamine 2,3-dioxygenase (IDO) blockade and immunogenic chemotherapy represents a brilliant future in cancer therapy. However, it remains challenging to precisely activate chemo-immunotherapy in situ to avoid side effects from the systemic administrations and reverse the poor immunogenicity and immunosuppressive microenvironment in tumor sites. Herein, a hybrid nanomedicine ("RPMANB NPs") to co-deliver an IDO inhibitor (NLG919) and a chemotherapeutic prodrug to amplify the therapeutic benefits are designed. Attributed to the delicate surface engineering, the RPMANB NPs possess excellent pharmacokinetics and tumor accumulation. The loaded NLG919 are released inside cancer tissues/cells due to the collapse of the metal-organic framework platform triggered by the highly concentrated phosphate, reversing the immunosuppressive tumor microenvironment by suppressing IDO activity. The potent chemotherapeutic drug is precisely activated through a highly efficient plasmon-driven catalysis in the presence of near-infrared light, eliciting antitumor immunity by triggering immunogenic cell death and avoiding side effects through in situ activation of chemotherapy. In vivo studies demonstrate that the chemo-immunotherapy greatly suppresses the tumor growth by promoting intratumoral accumulation of cytotoxic T lymphocytes and downregulating regulatory T cells. This work establishes a robust delivery platform to overcome the current obstacles of tumor treatments by combining precisely activatable chemotherapy with immunotherapy.

Unexpected photoactivation pathways in a folate-receptor-targeted trans-diazido Pt(IV) anticancer pro-drug

A conjugate between a photoactive trans-diazido Pt(iv) pro-drug, trans,trans,trans-[Pt(N3)2(OH)2(py)2], and folic acid has been synthesized and fully characterized by high resolution ESI-MS, NMR and UV-vis spectroscopy. Photoactivation of the Pt-folate conjugate with visible light confirmed the generation of cytotoxic Pt(ii) species capable of binding to guanine nucleobases. Importantly, photoreduction of the Pt(iv) complex triggered the photodecomposition of the folate vector into a p-aminobenzoate-containing fragment and several pterin derivatives, including 6-formylpterin. Besides exhibiting high dark stability in physiological-like conditions, the Pt-folate conjugate was ca. 2× more photocytotoxic towards MCF-7 breast cancer cell line than its parent Pt(iv) complex with a high photoselectivity index (PI > 6.9). The higher photocytotoxicity of the conjugate may be a consequence of its higher cellular accumulation and of the generation of a set of different cytotoxic species, including Pt(ii) photoproducts and several pterin derivatives, which are known to generate ROS.

Recent Progress on Tubulin Inhibitors with Dual Targeting Capabilities for Cancer Therapy

Microtubules play a crucial role in multiple cellular functions including mitosis, cell signaling, and organelle trafficking, which makes the microtubule an important target for cancer therapy. Despite the great successes of microtubule-targeting agents in the clinic, the development of drug resistance and dose-limiting toxicity restrict their clinical efficacy. In recent years, multitarget therapy has been considered an effective strategy to achieve higher therapeutic efficacy, in particular dual-target drugs. In terms of the synergetic effect of tubulin and other antitumor agents such as receptor tyrosine kinases inhibitors, histone deacetylases inhibitors, DNA-damaging agents, and topoisomerase inhibitors in combination therapy, designing dual-target tubulin inhibitors is regarded as a promising approach to overcome these limitations and improve therapeutic efficacy. In this Perspective, we discussed rational target combinations, design strategies, structure-activity relationships, and future directions of dual-target tubulin inhibitors.

A valproic acid-modified platinum diimine complex as potential photosensitizer for photodynamic therapy

Histone deacetylase inhibitors have often been used in combination treatment of various types of cancers due to their non-genotoxic epigenetic potential. Valproic acid (VPA) is a well-known histone deacetylase inhibitor. Conjugate of VPA with a phtoactive platinum diimine complex through an ester bond has been fabricated to potentiate the photocytotoxicity of the photosensitizer. Its capability to generate singlet oxygen, behavior in the presence of esterase, and photocytotoxicity in tumor cells have also been studied. The results revealed that the novel VPA-modified platinum diimine complex could produce singlet oxygen efficiently and release VPA in the presence of porcine liver esterase. The results also suggested that incorporation of VPA moiety into the platinum diimine complex might significantly enhance the cytotoxicity of the complex.

Novel Pt(IV) complexes to overcome multidrug resistance in gastric cancer by targeting P-glycoprotein

Systematic toxicity and drug resistance significantly limited FDA-approved platinum drugs for further clinical applications. In order to reverse the resistance (MDR) and enhance their anticancer efficiency, four Pt(IV) complexes (12-15) conjugating with P-glycoprotein (P-gp) inhibitors were designed and synthesized. Among them, complex 14 (IC₅₀ = 3.37 μM) efficiently reversed cisplatin resistance in SGC-7901/CDDP cell line and increased selectivity index (6.9) against normal HL-7702 cell line. Detailed mechanisms in SGC-7901/CDDP cells assays revealed that complex 14 efficiently induced apoptosis via down-regulating expression of P-gp for enhanced intracellular uptake of platinum, arrested cells at G2/M phase, induced DNA damage and initiated mitochondrial apoptosis pathway. Further in vivo studies demonstrated that the enhanced accumulation of complex 14 contributed to tumor inhibition of 75.6% in SGC-7901/CDDP xenografts, which was much higher than cisplatin (25.9%) and oxaliplatin (43%). Moreover, the low systematic toxicity made 14 a potential novel P-gp-mediated MDR modulator.

Immune Checkpoint Inhibitor-Based Strategies for Synergistic Cancer Therapy

Immune checkpoint blockade therapy (ICBT) targeting checkpoints, such as, cytotoxic T-lymphocyte associated protein-4 (CTLA-4), programmed death-1 (PD-1), or programmed death-ligand 1 (PD-L1), can yield durable immune response in various types of cancers and has gained constantly increasing research interests in recent years. However, the efficacy of ICBT alone is limited by low response rate and immune-related side effects. Emerging preclinical and clinical studies reveal that chemotherapy, radiotherapy, phototherapy, or other immunotherapies can reprogramm immunologically "cold" tumor microenvironment into a "hot" one, thus synergizing with ICBT. In this review, the working principle and current development of various immune checkpoint inhibitors are summarized, while the interactive mechanism and recent progress of ICBT-based synergistic therapies with other immunotherapy, chemotherapy, phototherapy, and radiotherapy in fundamental and clinical studies in the past 5 years are depicted and highlighted. Moreover, the potential issues in current studies of ICBT-based synergistic therapies and future perspectives are also discussed.

Co-delivery of IOX1 and doxorubicin for antibody-independent cancer chemo-immunotherapy

Anti-programmed cell death-1 (PD-1)/programmed cell death-ligand 1 (PD-L1) antibodies are currently used in the clinic to interupt the PD-1/PD-L1 immune checkpoint, which reverses T cell dysfunction/exhaustion and shows success in treating cancer. Here, we report a histone demethylase inhibitor, 5-carboxy-8-hydroxyquinoline (IOX1), which inhibits tumour histone demethylase Jumonji domain-containing 1A (JMJD1A) and thus downregulates its downstream β-catenin and subsequent PD-L1, providing an antibody-independent paradigm interrupting the PD-1/PD-L1 checkpoint. Synergistically, IOX1 inhibits cancer cells’ P-glycoproteins (P-gp) through the JMJD1A/β-catenin/P-gp pathway and greatly enhances doxorubicin (DOX)-induced immune-stimulatory immunogenic cell death. As a result, the IOX1 and DOX combination greatly promotes T cell infiltration and activity and significantly reduces tumour immunosuppressive factors. Their liposomal combination reduces the growth of various murine tumours, including subcutaneous, orthotopic, and lung metastasis tumours, and offers a long-term immunological memory function against tumour rechallenging. This work provides a small molecule-based potent cancer chemo-immunotherapy.

Some chemotherapeutic drugs, such as doxorubicin, induce immunogenic cell death (ICD) and promote anti-tumor immune responses. Here the authors report that the histone demethylase inhibitor 5-carboxy-8-hydroxyquinoline (IOX1) reduces the expression of PD-L1 in cancer cells and enhances doxorubicin-induced ICD, promoting T cell infiltration and reducing tumor growth in preclinical models.

Tryptophan 2, 3‑dioxygenase promotes proliferation, migration and invasion of ovarian cancer cells

Tryptophan 2,3-dioxygenase (TDO2) is a key rate-limiting enzyme in the kynurenine pathway and promotes tumor growth and escape from immune surveillance in different types of cancer. The present study aimed to investigate whether TDO2 serves a role in the development of ovarian cancer. Reverse transcription-quantitative PCR and western blotting were used to detect the expression of TDO2 in different cell lines. The effects of TDO2 overexpression, TDO2 knockdown and TDO2 inhibitor on ovarian cancer cell proliferation, migration and invasion were determined by MTS, colony formation and Transwell assays. The expression of TDO2 in ovarian cancer tissues, normal ovarian tissues and fallopian tube tissues were analyzed using the gene expression data from The Cancer Genome Atlas and Genotype-Tissue Expression project. Immune cell infiltration in cancer tissues was evaluated using the single sample gene set enrichment analysis algorithm. The present study found that Ras^V12-mediated oncogenic transformation was accompanied by the upregulation of TDO2. In addition, it was demonstrated that TDO2 was upregulated in ovarian cancer tissues compared with normal ovarian tissues. TDO2 overexpression promoted proliferation, migration and invasion of ovarian cancer cells, whereas TDO2 knockdown repressed these phenotypes. Treatment with LM10, a TDO2 inhibitor, also repressed the proliferation, migration and invasion of ovarian cancer cells. The present study indicated that TDO2 can be used as a new target for the treatment of ovarian cancer.

An intramolecular photoswitch can significantly promote photoactivation of Pt(iv) prodrugs

Selective activation of prodrugs at diseased tissue through bioorthogonal catalysis represents an attractive strategy for precision cancer treatment. Achieving efficient prodrug photoactivation in cancer cells, however, remains challenging. Herein, we report two Pt(iv) complexes, designated as rhodaplatins {rhodaplatin 1, [Pt(CBDCA-O,O)(NH3)2(RhB)OH]; rhodaplatin 2, [Pt(DACH)ox(RhB)(OH)], where CBDCA is cyclobutane-1,1-dicarboxylate, RhB is rhodamine B, DACH is (1R,2R)-1,2-diaminocyclohexane, and ox is oxalate}, that bear an internal photoswitch to realize efficient accumulation, significant co-localization, and subsequent effective photoactivation in cancer cells. Compared with the conventional platform of external photocatalyst plus substrate, rhodaplatins presented up to 4.8 104-fold increased photoconversion efficiency in converting inert Pt(iv) prodrugs to active Pt(ii) species under physiological conditions, due to the increased proximity and covalent bond between the photoswitch and Pt(iv) substrate. As a result, rhodaplatins displayed increased photocytotoxicity compared with a mixture of RhB and conventional Pt(iv) compound in cancer cells including Pt-resistant ones. Intriguingly, rhodaplatin 2 efficiently accumulated in the mitochondria and induced apoptosis without causing genomic DNA damage to overcome drug resistance. This work presents a new approach to develop highly effective prodrugs containing intramolecular photoswitches for potential medical applications.

The introduction of immunosuppressor (TDO inhibitor) significantly improved the efficacy of irinotecan in treating hepatocellular carcinoma

As TDO inhibitors can improve the efficacy of tumor chemotherapeutics, two TDO-targeted conjugates consisting of irinotecan (Ir) and a TDO inhibitor unit were designed and prepared to reverse tumor immune suppression, which could remarkably enhance antitumor activity of Ir by boosting cellular uptakes against TDO overexpressed HepG2 cancer cells. In vitro mechanistic studies demonstrated that compound PVIS-Ir and PVIG-Ir could arrest cell cycle at G2 phase and induce cell apoptosis by mitochondrial apoptotic pathway. Furthermore, compound PVIS-Ir could effectively inhibit TDO protein expression via releasing a TDO inhibitor derivative, which could also completely embed in TDO protein pocket. Further mechanism study indicated that PVIS-Ir could block kynurenine production and deactivate aryl hydrocarbon receptor (AHR), resulting in T-cell activation and proliferation. In vivo studies confirmed that PVIS-Ir could improve tumor immune microenvironment in a murine model. This combinational strategy of chemotherapy and immunotherapy can be a promising way in the treatment of hepatocellular carcinoma. Conjugates obtained by combining an immune checkpoint TDO inhibitor with irinotecan via different linkers could improve tumor immune microenvironment by inhibiting the TDO enzyme expression to block kynurenine production and induce HepG2 cancer cell apoptosis via DNA damage through releasing a TDO inhibitor and irinotecan in cancer cells.

Nanoenabled Tumor Oxygenation Strategies for Overcoming Hypoxia-Associated Immunosuppression

Cancer immunotherapy, which initiates or strengthens innate immune responses to attack cancer cells, has shown great promise in cancer treatment. However, low immune response impacted by immunosuppressive tumor microenvironment (TME) remains a key challenge, which has been found related to tumor hypoxia. Recently, nanomaterial systems are proving to be excellent platforms for tumor oxygenation, which can reverse hypoxia-associated immunosuppression, strengthen the systemic antitumor immune responses, and thus afford a striking abscopal effect to clear metastatic cancer cells. In this review, we would like to survey recent progress in utilizing nanomaterials for tumor oxygenation through approaches such as in situ O₂ generation, O₂ delivery, tumor vasculature normalization, and mitochondrial-respiration inhibition. Their effects on tumor hypoxia-associated immunosuppression are highlighted. We also discuss the ongoing challenges and how to further improve the clinical prospect of cancer immunotherapy.