G-quadruplex structural transition driven by a platinum compound.

G-quadruplex (G4) transitions play integral roles in regulating biological functions and can be modified by ligands. However, little is known about G4 transitions. Herein, we reveal distinct pathways of a platinum(II) compound Pt-phen converting parallel-stranded MYC G4 to a hybrid-type structure. Three NMR structures, 1:1 5'-end binding, 1:1 3'-end binding and 2:1 Pt-phen-MYC G4 complexes, were determined by NMR. We find that Pt-phen drives G4 transition at a low ratio. Under physiological 100 mM K+ conditions, a significant stable hydrogen-bonded T:T:A triad is formed at 3'-end of hybrid-type Myc1234, and consequently, Pt-phen first binds the 5'-end to form a 1:1 5'-end binding complex and then disrupts the 3' T:T:A triad and binds 3'-end to form a 2:1 complex with more Pt-phen. Remarkably, the G4 transition pathway is different in 5 mM K+ with Pt-phen first binding the 3'-end and then the 5'-end. 'Edgewise-loop and flanking/ligand/G-tetrad' sandwich structure formation and terminal T:T:A triad stabilization play decisive roles in advancing and altering transition pathways. Our work is the first to elucidate the molecular structures of G4 transitions driven by a small molecule. The ligand-driven G4 transition is a dynamic process that includes a quick G4 transition and multiple complexes formation.

Organometallic anti-tumor agents: targeting from biomolecules to dynamic bioprocesses.

The great clinical success of cisplatin and its derivatives has convinced people that metal complexes could play a more significant role in human cancer therapy. However, targeting and drug resistance are still two dominant problems that need to be urgently solved for metallodrugs' efficacy and clinical translation. As an important component of metal complexes, organometallics have been experiencing rapid development in recent years. Compared with platinum drugs, emerging anti-tumor organometallics targeting dynamic bioprocesses provide an effective strategy to overcome conventional problems. This review focuses on burgeoning anti-tumor strategies and provides up-to-date advances in anti-tumor organometallics development based on their action mechanisms. Specifically, important tumor-overexpressed proteins and nucleic acids as organometallics' anti-tumor targets are systematically presented, followed by organometallics that exert their anti-tumor activity by perturbing tumor intracellular energy/redox/metal/immune homeostasis. Finally, nine cell death pathways including apoptosis, paraptosis, autophagy, oncosis, necrosis, necroptosis, ferroptosis, pyroptosis, and immunogenic cell death (ICD) that can be induced by organometallics are reviewed, and their morphological and biochemical features are summarised. This review at the interface of chemistry, biology, and medicine aims to enlighten the rational development of organometallic anti-tumor agents.

Regulation of DNA-binding activity of the Staphylococcus aureus catabolite control protein A by copper (II)-mediated oxidation.

Catabolite control protein A (CcpA) of the human pathogen Staphylococcus aureus is an essential DNA regulator for carbon catabolite repression and virulence, which facilitates bacterial survival and adaptation to a changing environment. Here, we report that copper (II) signaling mediates the DNA-binding capability of CcpA in vitro and in vivo. Copper (II) catalyzes the oxidation of two cysteine residues (Cys216 and Cys242) in CcpA to form intermolecular disulfide bonds between two CcpA dimers, which results in the formation and dissociation of a CcpA tetramer of CcpA from its cognate DNA promoter. We further demonstrate that the two cysteine residues on CcpA are important for S. aureus to resist host innate immunity, indicating that S. aureus CcpA senses the redox-active copper (II) ions as a natural signal to cope with environmental stress. Together, these findings reveal a novel regulatory mechanism for CcpA activity through copper (II)-mediated oxidation.

Organic-Platinum Hybrids for Covalent Binding of G-Quadruplexes: Structural Basis and Application to Cancer Immunotherapy.

G-quadruplexes (G4s) have been revived as promising therapeutic targets with the development of immunotherapy, but the G4-mediated immune response remains unclear. We designed a novel class of G4-binding organic-platinum hybrids, L1 -cispt and L1 -transpt, with spatial matching for G4 binding and G4 DNA reactivity for binding site locking. The solution structure of L1 -transpt-MYT1L G4 demonstrated the effectiveness of the covalent binding and revealed the covalent binding-guided dynamic balance, accompanied by the destruction of the A5-T17 base pairs to achieve the covalent binding of the platinum unit to N7 of the G6 residue. Furthermore, L1 -cispt- and L1 -transpt-mediated genomic dysfunction could activate the retinoic acid-induced gene I (RIG-I) pathway and induce immunogenic cell death (ICD). The use of L1 -cispt/L1 -transpt-treated dying cells as therapeutic vaccines stimulated a robust immune response and effectively inhibited tumor growth in vivo. Our findings highlight the importance of the rational combination of specific spatial recognition and covalent locking in G4-trageting drug design and their potential in immunotherapy.

Disruption of Zinc Homeostasis by a Novel Platinum(IV)-Terthiophene Complex for Antitumor Immunity.

Zinc homeostatic medicine is of great potential for cancer chemo-immunotherapy; however, there are few reports on antitumor compounds that can trigger Zn2+ -mediated immune responses. In this work, we developed a novel cyclometalated PtIV -terthiophene complex, Pt3, that not only induces DNA damage and cellular metabolism dysregulation, but also disrupts zinc homeostasis as indicated by the abnormal transcriptional level of zinc regulatory proteins, excess accumulation of Zn2+ in cytoplasm, and down-regulation of metallothioneins (MTs), which further caused redox imbalance. The simultaneous disruption of zinc and redox homeostasis in response to Pt3 treatment activated gasdermin-D mediated pyroptosis accompanied by cytoskeleton remodeling, thus releasing pro-inflammatory cytokines to promote dendritic cell (DC) maturation and T cell tumor-infiltration, eventually eliminating both primary and distant tumors in vivo. As far as we know, this is the first metal complex that can regulate zinc homeostasis to activate antitumor immunity.

Engineered Bacteria Labeled with Iridium(III) Photosensitizers for Enhanced Photodynamic Immunotherapy of Solid Tumors.

Despite metal-based photosensitizers showing great potential in photodynamic therapy for tumor treatment, the application of the photosensitizers is intrinsically limited by their poor cancer-targeting properties. Herein, we reported a metal-based photosensitizer-bacteria hybrid, Ir-HEcN, via covalent labeling of an iridium(III) photosensitizer to the surface of genetically engineered bacteria. Due to its intrinsic self-propelled motility and hypoxia tropism, Ir-HEcN selectively targets and penetrates deeply into tumor tissues. Importantly, Ir-HEcN is capable of inducing pyroptosis and immunogenic cell death of tumor cells under irradiation, thereby remarkably evoking anti-tumor innate and adaptive immune responses in vivo and leading to the regression of solid tumors via combinational photodynamic therapy and immunotherapy. To the best of our knowledge, Ir-HEcN is the first metal complex decorated bacteria for enhanced photodynamic immunotherapy.

A Golgi-Targeted Platinum Complex Plays a Dual Role in Autophagy Regulation for Highly Efficient Cancer Therapy.

Regulating autophagy to control the homeostatic recycling process of cancer cells is a promising anticancer strategy. Golgi apparatus is a substrate of autophagy but the Golgi-autophagy (Golgiphagy) mediated antitumor pathway is rarely reported. Herein, we have developed a novel Golgi-targeted platinum (II) complex Pt3, which is ca. 20 times more cytotoxic to lung carcinoma than cisplatin and can completely eliminate tumors after intratumoral administration in vivo. Its nano-encapsulated system for tail vein administration also features a good anti-tumor effect. Mechanism studies indicate that Pt3 induces substantial Golgi stress, indicated by the fragmentation of Golgi structure, down-regulation of Golgi proteins (GM130, GRASP65/55), loss of Golgi-dependent transport and glycosylation. This triggers Golgiphagy but blocks the subsequent fusion of autophagosomes with lysosomes, that is a dual role in autophagy regulation, resulting in loss of proteostasis and apoptotic cell death. As far as we know, Pt3 is the first Golgi-targeted Pt complex that can trigger Golgi stress-mediated dual-regulation of autophagic flux and autophagy-apoptosis crosstalk for highly efficient cancer therapy.

Evoking Ferroptosis by Synergistic Enhancement of a Cyclopentadienyl Iridium-Betulin Immune Agonist.

Ferroptosis is a form of programmed cell death driven by iron-dependent lipid peroxidation (LPO) with the potential for antitumor immunity activation. In this study, a nonferrous cyclopentadienyl metal-based ferroptosis inducer [Ir(Cp*)(Bet)Cl]Cl (Ir-Bet) was developed by a metal-ligand synergistic enhancement (MLSE) strategy involving the reaction of [Ir(Cp*)Cl]2 Cl2 with the natural product Betulin. The fusion of Betulin with iridium cyclopentadienyl (Ir-Cp*) species as Ir-Bet not only tremendously enhanced the antiproliferative activity toward cancer cells, but also activated ferritinophagy for iron homeostasis regulation by PI3K/Akt/mTOR cascade inhibition with a lower dosage of Betulin, and then evoked an immune response by nuclear factor kappa-B (NF-κB) activation of Ir-Cp* species. Further immunogenic cell death (ICD) occurred by remarkable ferroptosis through glutathione (GSH) depletion, glutathione peroxidase 4 (GPX4) deactivation and ferritinophagy. An in vivo vaccination experiment demonstrated desirable antitumor and immunogenic effects of Ir-Bet by increasing the ratio of cytotoxic T cells (CTLs)/regulatory T cells (Tregs).

Structural Basis of Pyridostatin and Its Derivatives Specifically Binding to G-Quadruplexes.

The nucleic acid G-quadruplex (G4) has emerged as a promising therapeutic target for a variety of diseases such as cancer and neurodegenerative disease. Among small-molecule G4-binders, pyridostatin (PDS) and its derivatives (e.g., PyPDS) exhibit high specificity to G4s, but the structural basis for their specific recognition of G4s remains unknown. Here, we presented two solution structures of PyPDS and PDS with a quadruplex-duplex hybrid. The structures indicate that the rigid aromatic rings of PyPDS/PDS linked by flexible amide bonds match adaptively with G-tetrad planes, enhancing π-π stacking and achieving specific recognition of G4s. The aliphatic amine side chains of PyPDS/PDS adjust conformation to interact with the phosphate backbone via hydrogen bonding and electrostatic interactions, increasing affinity for G4s. Moreover, the N-H of PyPDS/PDS amide bonds interacts with two O6s of G-tetrad guanines via hydrogen bonding, achieving a further increase in affinity for G4s, which is different from most G4 ligands. Our findings reveal from structural perspectives that the rational assembly of rigid and flexible structural units in a ligand can synergistically improve the selectivity and affinity for G4s through spatial selective and adaptive matching.

Self-Amplifying Iridium(III) Photosensitizer for Ferroptosis-Mediated Immunotherapy Against Transferrin Receptor-Overexpressing Cancer.

Photoimmunotherapy is attractive for cancer treatment due to its spatial controllability and sustained responses. This work presents a ferrocene-containing Ir(III) photosensitizer (IrFc1) that can bind with transferrin and be transported into triple-negative breast cancer (TNBC) cells via a transferrin receptor-mediated pathway. When the ferrocene in IrFc1 is oxidized by reactive oxygen species, its capability to photosensitize both type I (electron transfer) and type II (energy transfer) pathways is activated through a self-amplifying process. Upon irradiation, IrFc1 induces the generation of lipid oxidation to cause ferroptosis in TNBC cells, which promotes immunogenic cell death (ICD) under both normoxia and hypoxia. In vivo, IrFc1 treatment elicits a CD8+ T-cell response, which activates ICD in TNBC resulting in enhanced anticancer immunity. In summary, this work reports a small molecule-based photosensitizer with enhanced cancer immunotherapeutic properties by eliciting ferroptosis through a self-amplifying process.

An Enhanced Photothermal Therapeutic Iridium Hybrid Platform Reversing the Tumor Hypoxic Microenvironment.

As hypoxia is closely associated with tumor progression, proliferation, invasion, metastasis, and strong resistance to therapy, regulating and overcoming the hypoxia tumor microenvironment are two increasingly important aspects of tumor treatment. Herein, we report a phototherapeutic platform that uses the organic photosensitizer diketopyrrolopyrrole (DPP) derivative and inorganic iridium salts (IrCl3) with photothermal activity and the capacity to decompose H2O2 efficiently. The characterization of their photophysical properties proved that DPP-Ir nanoparticles are capable of remarkable near-infrared (NIR) absorption, and compared to DPP nanoparticles, the photothermal conversion efficiency (PCE) increases from 42.1% in DPP nanoparticles to 67.0% in DPP-Ir nanoparticles. The hybrid nanoparticles utilize the catalytic decomposition of endogenous H2O2 to produce oxygen for the downregulation of the hypoxia-inducible factor 1 subunit alpha (HIF-1α) protein, which could reverse the tumor hypoxic microenvironment. Benefiting from the excellent optical properties and good biocompatibility, the hybrid platform exhibits efficient photothermal therapeutic effects as well as good biological safety. In conclusion, such a hybrid platform could improve photothermal therapy against cancer.

Inhibition of Quorum-Sensing Regulator from Pseudomonas aeruginosa Using a Flavone Derivative.

Quorum sensing (QS) is a cell-to-cell communication process that controls bacterial collective behaviors. The QS network regulates and coordinates bacterial virulence factor expression, antibiotic resistance and biofilm formation. Therefore, inhibition of the QS system is an effective strategy to suppress the bacterial virulence. Herein, we identify a phosphate ester derivative of chrysin as a potent QS inhibitor of the human pathogen Pseudomonas aeruginosa (P. aeruginosa) using a designed luciferase reporter assay. In vitro biochemical analysis shows that the chrysin derivative binds to the bacterial QS regulator LasR and abrogates its DNA-binding capability. In particular, the derivative exhibits higher anti-virulence activity compared to the parent molecule. All the results reveal the potential application of flavone derivative as an anti-virulence compound to combat the infectious diseases caused by P. aeruginosa.

A Nuclear-Targeted AIE Photosensitizer for Enzyme Inhibition and Photosensitization in Cancer Cell Ablation.

The nucleus is considered the ideal target for anti-tumor therapy because DNA and some enzymes in the nucleus are the main causes of cell canceration and malignant proliferation. However, nuclear target drugs with good biosafety and high efficiency in cancer treatment are rare. Herein, a nuclear-targeted material MeTPAE with aggregation-induced emission (AIE) characteristics was developed based on a triphenylamine structure skeleton. MeTPAE can not only interact with histone deacetylases (HDACs) to inhibit cell proliferation but also damage telomere and nucleic acids precisely through photodynamic treatment (PDT). The cocktail strategy of MeTPAE caused obvious cell cycle arrest and showed excellent PDT anti-tumor activity, which offered new opportunities for the effective treatment of malignant tumors.

Ferroptosis-Enhanced Cancer Immunity by a Ferrocene-Appended Iridium(III) Diphosphine Complex.

Ferroptosis is a programmed cell death pathway discovered in recent years, and ferroptosis-inducing agents have great potential as new antitumor candidates. Here, we report a IrIII complex (Ir1) containing a ferrocene-modified diphosphine ligand that localizes in lysosomes. Under the acidic environments of lysosomes, Ir1 can effectively catalyze Fenton-like reaction, produce hydroxyl radicals, induce lipid peroxidation, down-regulate glutathione peroxidase 4, and result in ferroptosis. RNA sequencing analysis shows that Ir1 can significantly affect pathways related to ferroptosis and cancer immunity. Accordingly, Ir1 can induce immunogenic cells death and suppress tumor growth in vitro, regulate T cell activity and immune microenvironments in vivo. In conclusion, we show the potential of small molecules with ferroptosis-inducing capabilities for effective cancer immunotherapy.

In Situ Prodrug Activation by an Affibody-Ruthenium Catalyst Hybrid for HER2-Targeted Chemotherapy.

Transition-metal catalysts exhibit great potential as therapeutic agents to inhibit tumor growth. However, the precise delivery and in situ catalysis are challenging in catalytic medicine. Herein, we report an anti-HER2 affibody-ruthenium catalyst hybrid, named Ru-HER2 for selective and effective killing of cancer cells. Ru-HER2 binds to the HER2 receptor on a tumor cell and in situ catalyzes the activation of gemcitabine prodrug, resulting in enhanced selectivity in suppression of tumor growth and reduction of side effects. Immunoblotting reveals that Ru-HER2 in combination with gemcitabine prodrug can not only induce DNA damage, but also effectively block the HER2 signaling pathway in cancer cells. Therefore, the HER2-targeted chemotherapy exhibits substantially high anticancer activity toward HER2-positive cancer cells in vitro and in vivo. In a word, we report the first affibody-ruthenium catalyst hybrid and reveal its potential for effective HER2-targeted cancer chemotherapy.

A Carbonic Anhydrase IX (CAIX)-Anchored Rhenium(I) Photosensitizer Evokes Pyroptosis for Enhanced Anti-Tumor Immunity.

An ideal cancer treatment should not only destroy primary tumors but also improve the immunogenicity of the tumor microenvironment to achieve a satisfactory anti-tumor immune effect. We designed a carbonic anhydrase IX (CAIX)-anchored rhenium(I) photosensitizer, named CA-Re, that not only performs type-I and type-II photodynamic therapy (PDT) with high efficiency under hypoxia (nanomolar-level phototoxicity), but also evokes gasdermin D (GSDMD) mediated pyroptotic cell death to effectively stimulate tumor immunogenicity. CA-Re could disrupt and self-report the loss of membrane integrity simultaneously. This promoted the maturation and antigen-presenting ability of dendritic cells (DCs), and fully activated T cells dependent adaptive immune response in vivo, eventually eliminating distant tumors at the same time as destroying primary tumors. To the best of our knowledge, CA-Re is the first metal complex-based pyroptosis inducer.

Simultaneous Photoactivation of cGAS-STING Pathway and Pyroptosis by Platinum(II) Triphenylamine Complexes for Cancer Immunotherapy.

Activation of the cyclic GMP-AMP synthase-stimulator of the interferon gene (cGAS-STING) pathway is a potent anticancer immunotherapeutic strategy, and the induction of pyroptosis is a feasible way to stimulate the anticancer immune responses. Herein, two PtII complexes (Pt1 and Pt2) were designed as photoactivators of the cGAS-STING pathway. In response to light irradiation, Pt1 and Pt2 could damage mitochondrial/nuclear DNA and the nuclear envelope to activate the cGAS-STING pathway, and concurrently induce pyroptosis in cancer cells, which evoked an intense anticancer immune response in vitro and in vivo. Overall, we present the first photoactivator of the cGAS-STING pathway, which may provide an innovative design strategy for anticancer immunotherapy.

Induction and Monitoring of DNA Phase Separation in Living Cells by a Light-Switching Ruthenium Complex.

Phase separation of DNA is involved in chromatin packing for the regulation of gene transcription. Visualization and manipulation of DNA phase separation in living cells present great challenges. Herein, we present a Ru(II) complex (Ru1) with high DNA binding affinity and DNA "light-switch" behavior that can induce and monitor DNA phase separation both in vitro and in living cells. Molecular dynamics simulations indicate that the two phen-PPh3 ligands with positively charged lipophilic triphenylphosphine substituents and flexible long alkyl chains in Ru1 play essential roles in the formation of multivalent binding forces between DNA molecules to induce DNA phase separation. Importantly, the unique environmental sensitive emission property of Ru1 enables direct visualization of the dynamic process of DNA phase separation in living cells by two-photon phosphorescent lifetime imaging. Moreover, Ru1 can change the gene expression pattern by modulating chromatin accessibility as demonstrated by integrating RNA-sequencing and transposase-accessible chromatin with high-throughput sequencing. In all, we present here the first small-molecule-based tracer and modulator of DNA phase separation in living cells and elucidate its impact on the chromatin state and transcriptome.

Regulating Tumor N6 -Methyladenosine Methylation Landscape using Hypoxia-Modulating OsSx Nanoparticles.

The epigenetic dysregulation and hypoxia are two important factors that drive tumor malignancy, and N6 -methyladenosine (m6 A) in mRNA is involved in the regulation of gene expression. Herein, a nanocatalyst OsSx -PEG (PEG = poly(ethylene glycol)) nanoparticles (NPs) as O2 modulator is developed to improve tumor hypoxia. OsSx -PEG NPs can significantly downregulate genes involved in hypoxia pathway. Interestingly, OsSx -PEG NPs elevate RNA m6 A methylation levels to cause the m6 A-dependent mRNA degradation of the hypoxia-related genes. Moreover, OsSx -PEG NPs can regulate the expression of RNA m6 A methyltransferases and demethylases. Finally, DOX@OsSx -PEG (DOX = doxorubicin; utilized as a model drug) NPs modulate tumor hypoxia and regulate mRNA m6 A methylation of hypoxia-related genes in vivo. As the first report about relationship between catalytic nanomaterials and RNA modifications, the research opens a new avenue for unveiling the underlying action mechanisms of hypoxia-modulating nanomaterials and shows potential of regulating RNA modification to overcome chemoresistance.

Light-Triggered Nitric Oxide Release by a Photosensitizer to Combat Bacterial Biofilm Infections.

Bacterial biofilms are a serious global health concern, often responsible for persistent infections. New strategies to prevent and treat bacterial infections by eradication of the biofilms are urgently needed. A novel ruthenium-based compound is reported in this study that functions as both a boronic acid-decorated photosensitizer (PS) and a light-triggered nitric oxide (NO) releasing agent. The compound can selectively attach to the bacterial membrane and biofilms and it is highly potent at eradicating Pseudomonas aeruginosa biofilms through the simultaneous release of NO and reactive oxygen species (ROS). The compound, which is more effective than clinical antibiotic tobramycin, also has excellent bacterial specificity and shows no significant cytotoxicity to human cells. The results reveal potential applications of this innovative dual-functional photoactivated ruthenium compound to combat bacterial biofilm infections.