Mitochondrion-targeted platinum complexes suppressing lung cancer through multiple pathways involving energy metabolism

Fighting metallodrug resistance through alteration of drug metabolism and blockage of autophagic flux by mitochondria-targeting AIEgens

PPh3-decorated mitochondrial-targeting AIEgens could fight metallodrug resistance through alteration of drug metabolism and blockage of autophagic flux.

Platinum Complexes as Inhibitors of DNA Repair Protein Ku70 and Topoisomerase IIα in Cancer Cells

Ku70 protein and topoisomerase IIα (Topo IIα) are promising targets of anticancer drugs, which play critical roles in DNA repair and replication processes. Three platinum(II) complexes, [PtCl(NH3)2(9-(pyridin-2-ylmethyl)-9H-carbazole)]NO3 (OPPC), [PtCl(NH3)2(9-(pyridin-3-ylmethyl)-9H-carbazole)]NO3 (MPPC),...

Mitochondria-targeted Pt(IV) prodrugs conjugated with an aggregation-induced emission luminogen against breast cancer cells by dual modulation of apoptosis and autophagy inhibition

Theranostic anticancer agents with dual functions of diagnosis and therapy are in highly demand for breast cancer. Herein, a triphenylphosphonium (TPP)-decorated aggregation-induced emission (AIE)-based Pt(IV) prodrug ACPt was developed, which exhibited superior anticancer performance with novel anticancer mechanism of dual modulation of apoptosis and autophagy inhibition. The experimental data showed that ACPt induced increased reactive oxygen species (ROS), and decreased mitochondrial membrane potential (MMP). The morphology and function of mitochondria were also severely damaged and ACPt showed strong inhibition to both mitochondrial and glycolytic bioenergetics. Moreover, DNA damage and cell cycle arrest in the S-phase were also observed after the ACPt treatment, eventually leading to the apoptosis and autophagy inhibition of cancer cells. Furthermore, ACPt also indicated excellent anti-proliferation activity in 3D multicellular tumor spheroids (MCTSs), suggesting the potential to inhibit solid tumors in vivo. Our observation demonstrated that ACPt could serve as a promising anticancer theranostic agent toward breast cancers for prodrug activation monitoring and image-guided chemotherapy.

From OCR and ECAR to energy: Perspectives on the design and interpretation of bioenergetics studies

Biological energy transduction underlies all physiological phenomena in cells. The metabolic systems that support energy transduction have been of great interest due to their association with numerous pathologies including diabetes, cancer, rare genetic diseases, and aberrant cell death. Commercially available bioenergetics technologies (e.g., extracellular flux analysis, high-resolution respirometry, fluorescent dye kits, etc.) have made practical assessment of metabolic parameters widely accessible. This has facilitated an explosion in the number of studies exploring, in particular, the biological implications of oxygen consumption rate (OCR) and substrate level phosphorylation via glycolysis (i.e., via extracellular acidification rate (ECAR)). Though these technologies have demonstrated substantial utility and broad applicability to cell biology research, they are also susceptible to historical assumptions, experimental limitations, and other caveats that have led to premature and/or erroneous interpretations. This review enumerates various important considerations for designing and interpreting cellular and mitochondrial bioenergetics experiments, some common challenges and pitfalls in data interpretation, and some potential "next steps" to be taken that can address these highlighted challenges.

Nanopore Sequencing Accurately Identifies the Cisplatin Adduct on DNA

Cisplatin, which selectively binds to N⁷ atoms of purines to inhibit normal replication and transcription, is a widely applied chemotherapeutic drug in the treatment of cancer. Though direct identification of cisplatin lesions on DNA is of great significance, existing sequencing methods have issues such as complications of preamplification or enrichment-induced false-positive reports. Direct identification of cisplatin lesions by nanopore sequencing (NPS) is in principle feasible. However, relevant investigations have never been reported. By constructing model sequences (83 nucleotides in length) containing a sole cisplatin lesion, identification of corresponding lesions by NPS is achieved with <10 ng of input sequencing library. Moreover, characteristic high-frequency noises caused by cisplatin lesions are consistently observed during NPS, clearly identifiable in corresponding high-pass filtered traces. This feature is, however, never observed in any other combinations of natural DNA bases and could be taken as a reference to identify cisplatin lesions on DNA. Further investigations demonstrate that cisplatin stalls the replication of phi29 DNA polymerase, which appears as a ∼5 pA level fluctuation in the single-molecule resolution. These results have confirmed the feasibility of NPS to identify cisplatin lesions at the genomic level and may provide new insights into understanding the molecular mechanism of platinum-based drugs.

A highly potent ruthenium(II)-sonosensitizer and sonocatalyst for in vivo sonotherapy

As a basic structure of most polypyridinal metal complexes, [Ru(bpy)₃]²⁺, has the advantages of simple structure, facile synthesis and high yield, which has great potential for scientific research and application. However, sonodynamic therapy (SDT) performance of [Ru(bpy)₃]²⁺ has not been investigated so far. SDT can overcome the tissue-penetration and phototoxicity problems compared to photodynamic therapy. Here, we report that [Ru(bpy)₃]²⁺ is a highly potent sonosensitizer and sonocatalyst for sonotherapy in vitro and in vivo. [Ru(bpy)₃]²⁺ can produce singlet oxygen (¹O₂) and sono-oxidize endogenous 1,4-dihydronicotinamide adenine dinucleotide (NADH) under ultrasound (US) stimulation in cancer cells. Furthermore, [Ru(bpy)₃]²⁺ enables effective destruction of mice tumors, and the therapeutic effect can reach deep tissues over 10 cm under US irradiation. This work paves a way for polypyridinal metal complexes to be applied to the noninvasive precise sonotherapy of cancer.

Sonodynamic therapy has therapeutic promise due to its safety and good tissue penetration, but is currently bottlenecked due to a lack of efficient and safe sonosensitizers. Here the authors show that [Ru(bpy)₃]²⁺ can produce singlet oxygen and sonooxidize NADH in deep tissue, and destroy mouse tumors effectively.

Redirecting Cisplatin and Doxorubicin to Mitochondria Affords Highly Effective PlatinumIV Prodrug Against Triple Negative Breast Cancer

A mitochondria targeting dual-action platinum^IV prodrug exhibits high anticancer activity in triple negative breast cancer cells. The complex intervenes in several cellular processes including DNA damage, perturbation of mitochondrial bioenergetics and induction of necrosis to kill cancer cells.

Assessing Impact of Platinum Complexes on Mitochondrial Functions

Platinum-based antitumor drugs play important roles in the clinical treatment of various tumors. Nevertheless, some deficiencies such as poor targeting ability, low bioavailability, in vivo deactivation, drug resistance, and side effects undermine the efficacy of these drugs. Mitochondria are important organelles which regulate the energy metabolism, physiological function, life span, and survival of the cells. Regulating or interfering with mitochondrial metabolism is of great significance in the prevention or treatment of cancers. Thus, a series of mitochondrion-targeted platinum complexes were prepared by modifying triphenylphosphine (TPP⁺) through chemical modifications, which endow traditional platinum drugs with new properties and mechanisms through interfering with mitochondrial DNA (mtDNA), mitochondrial membrane potential (MMP), mitochondrial morphology, mitochondrial bioenergetics, or production of reactive oxygen species (ROS), thereby opening a new path for the clinical application of platinum drugs. Here we introduce the synthesis of some TPP⁺-modified platinum (II, IV) complexes in details and the detection method of the activity parameters related to the mitochondrial functions.

Water-Soluble Iridic-Porphyrin Complex for Non-invasive Sonodynamic and Sono-oxidation Therapy of Deep Tumors

Due to conventional photodynamic therapy encountering serious problems of phototoxicity and low tissue-penetrating depth of light, other dynamic therapy-based therapeutic methods such as sonodynamic therapy (SDT) are expected to be developed. To improve the therapeutic response to SDT, more effective sonosensitizers are imperative. In this study, a novel water-soluble iridium(III)-porphyrin sonosensitizer (IrTMPPS) was synthesized and used for SDT. IrTMPPS generated ample singlet oxygen (¹O₂) under US irradiation and especially showed distinguished US-activatable abilities at more than 10 cm deep-tissue depths. Interestingly, under US irradiation, IrTMPPS sonocatalytically oxidized intracellular NADH, which would enhance SDT efficiency by breaking the redox balance in the tumor. Moreover, IrTMPPS displayed great sonocytotoxicity toward various cancer cells, and in vivo experiments demonstrated efficient tumor inhibition and anti-metastasis to the lungs in the presence of IrTMPPS and US irradiation. This report gives a novel idea of metal-based sonosensitizers for sonotherapy by fully taking advantage of non-invasiveness, water solubility, and deep tumor therapy.

BODIPY-Appended Pt(II) Complexes with High Toxicities and Anti-chemoresistance Performances in a Cisplatin Resistant In Vivo Model

Two novel fluorophore (BODIPY)-bearing complexes, pyriplatin (mCBP) and pyrimidine-chelated cisplatin (dCBP), were synthesized and characterized. The additional BODIPY-pyridine/pyridimine motifs of the two Pt(II) complexes resulted in stronger interactions with DNA in comparison with those of cisplatin. mCBP and cisplatin caused relative decreases in life span and body length in a cisplatin resistant in vivo model, N2 (wild-type) Caenorhabditis elegans. In contrast, dCBP resulted in a dramatic reduction in the two physiological parameters in N2 C. elegans, indicating high toxicity and sensitivity. The resistance factors (RF) of cisplatin, mCBP, and dCBP were determined to be 2.46, 1.04, and 0.91, respectively. The increasing RF folds for mCBP and dCBP against cisplatin were 2.36 and 2.70, respectively. This suggested they were featured with improved anti-chemoresistance capabilities. It is noteworthy that dCBP showed lowest lethal concentration (LC₅₀) values of 0.56 and 0.61 mM in cisplatin resistant and sensitive in vivo models, respectively. Upregulation of several evolutionary conservation genes that regulate cisplatin chemoresistance through cisplatin effluxing, the DNA damage response, the unfolded protein response, and detoxification (asna-1, parp-1, enpl-1, and skn-1) was observed upon exposure to cisplatin but not to mCBP and dCBP. This could explain the improved anti-chemoresistance performances of synthesized Pt(II) complexes.

Alternative mechanism of action of the DNP PtIV prodrug: intracellular cisplatin release and the mitochondria-mediated apoptotic pathway

In a recent research paper Dr. Suxing Jin et al. reported two multispecific PtIV complexes DNP and NP with non-steroidal anti-inflammatory drug naproxen (NPX) as the axial ligand(s). Herein, we clarify the mechanism of action of DNP, its therapeutic target and intracellular redox-status.

Targeting mitochondrial ion channels for cancer therapy

Pharmacological targeting of mitochondrial ion channels is emerging as a promising approach to eliminate cancer cells; as most of these channels are differentially expressed and/or regulated in cancer cells in comparison to healthy ones, this strategy may selectively eliminate the former. Perturbation of ion fluxes across the outer and inner membranes is linked to alterations of redox state, membrane potential and bioenergetic efficiency. This leads to indirect modulation of oxidative phosphorylation, which is/may be fundamental for both cancer and cancer stem cell survival. Furthermore, given the crucial contribution of mitochondria to intrinsic apoptosis, modulation of their ion channels leading to cytochrome c release may be of great advantage in case of resistance to drugs triggering apoptotic events upstream of the mitochondrial phase. In the present review, we give an overview of the known mitochondrial ion channels and of their modulators capable of killing cancer cells. In addition, we discuss state-of-the-art strategies using mitochondriotropic drugs or peptide-based approaches allowing a more efficient and selective targeting of mitochondrial ion channel-linked events.

Nanocatalytic Innate Immunity Activation by Mitochondrial DNA Oxidative Damage for Tumor-Specific Therapy

The innate immune system plays a key role in protecting the human body from tumors, which, unfortunately, is largely counteracted by their immune-suppression function. Such an immune suppression has been reported to be induced by the immunosuppressive microenvironment, including the exhausted cytotoxic T lymphocytes (CTLs) and tumor-promoting M2-polarized macrophages. Here, a novel tumor-immunotherapeutic modality based on the nanocatalytic innate immunity activation by tumor-specific mitochondrial DNA (mtDNA) oxidative damage is proposed. In detail, a nanocatalytic medicine, Fe2+ -Ru2+ -loaded mesoporous silica nanoparticle named as MSN-Ru2+ /Fe2+ (MRF), is constructed to induce oxidative damage in the mtDNA of tumor cells. Such an oxidative mtDNA is able to escape from the tumor cells and acts as an immunogenic damage-associated molecular pattern to M1-polarize tumor-associated macrophages (TAMs), resulting in the reactivated immunoresponse of macrophages against cancer cells, and the subsequent inflammatory response of innate immunity. Most importantly, the treatment strategy based on regulating the innate immune response of TAMs not only stops the primary tumor progression, but also almost completely inhibits the growth of distant tumors in the periods of treatments.

Interplay Between Thiamine and p53/p21 Axes Affects Antiproliferative Action of Cisplatin in Lung Adenocarcinoma Cells by Changing Metabolism of 2-Oxoglutarate/Glutamate

Thiamine (vitamin B1) is often deficient in oncopatients, particularly those undergoing chemotherapy. However, interaction between the thiamine deficiency and anticancer action of drugs has not been characterized. A major natural thiamine derivative, thiamine diphosphate (ThDP), is a coenzyme of central metabolism, also known to affect transcriptional activity of the master metabolic regulator and genome guardian p53. A direct transcriptional target of p53, p21, regulates cell cycle dynamics and DNA damage response. Our work focuses on dependence of the action of the DNA damaging anticancer drug cisplatin on metabolic regulation through p53/p21 axes and cellular thiamine status in human lung adenocarcinoma cells A549. These cells are used as a model of a hardly curable cancer, known to develop chemoresistance to platinum drugs, such as cisplatin. Compared to wild type (A549WT), a stable line with a 60% knockdown of p21 (A549p21-) is less sensitive to antiproliferative action of cisplatin. In contrast, in the thiamine-deficient medium, cisplatin impairs the viability of A549p21- cells more than that of A549WT cells. Analysis of the associated metabolic changes in the cells indicates that (i) p21 knockdown restricts the production of 2-oxoglutarate via glutamate oxidation, stimulating that within the tricarboxylic acid (TCA) cycle; (ii) cellular cisplatin sensitivity is associated with a 4-fold upregulation of glutamic-oxaloacetic transaminase (GOT2) by cisplatin; (iii) cellular cisplatin resistance is associated with a 2-fold upregulation of p53 by cisplatin. Correlation analysis of the p53 expression and enzymatic activities upon variations in cellular thiamine/ThDP levels indicates that p21 knockdown substitutes positive correlation of the p53 expression with the activity of 2-oxoglutarate dehydrogenase complex (OGDHC) for that with the activity of glutamate dehydrogenase (GDH). The knockdown also changes correlations of the levels of OGDHC, GDH and GOT2 with those of the malate and isocitrate dehydrogenases. Thus, a p53/p21-dependent change in partitioning of the glutamate conversion to 2-oxoglutarate through GOT2 or GDH, linked to NAD(P)-dependent metabolism of 2-oxoglutarate in affiliated pathways, adapts A549 cells to thiamine deficiency or cisplatin treatment. Cellular thiamine deficiency may interfere with antiproliferative action of cisplatin due to their common modulation of the p53/p21-dependent metabolic switch between the glutamate oxidation and transamination.

Cyclometalated Iridium(III) Complexes as Mitochondria-targeting Photosensitizers against Cisplatin-resistant Cells†

Four iridium (III) complexes Ir1-Ir4 were synthesized and characterized. Possessing high singlet oxygen production ability and specific mitochondria-localization, Ir1 was developed as a mitochondria-targeting photosensitizer. Ir1 exhibited strong phototoxicity against cancer cell line A549 and its corresponding cisplatin-resistant one A549R. In contrast, Ir1 showed low cytotoxicity toward normal cell HLF. This selectivity resulted from the different uptake amount. With 405 nm irradiation, Ir1 induced mitochondria-mediated cell death in A549R cells, achieving the overcome of drug-resistant.

Monofunctional Platinum(II) Anticancer Agents

Platinum-based anticancer drugs represented by cisplatin play important roles in the treatment of various solid tumors. However, their applications are largely compromised by drug resistance and side effects. Much effort has been made to circumvent the drug resistance and general toxicity of these drugs. Among multifarious designs, monofunctional platinum(II) complexes with a general formula of [Pt(3A)Cl]⁺ (A: Ammonia or amine) stand out as a class of "non-traditional" anticancer agents hopeful to overcome the defects of current platinum drugs. This review aims to summarize the development of monofunctional platinum(II) complexes in recent years. They are classified into four categories: fluorescent complexes, photoactive complexes, targeted complexes, and miscellaneous complexes. The intention behind the designs is either to visualize the cellular distribution, or to reduce the side effects, or to improve the tumor selectivity, or inhibit the cancer cells through non-DNA targets. The information provided by this review may inspire researchers to conceive more innovative complexes with potent efficacy to shake off the drawbacks of platinum anticancer drugs.

Anti-metastasis and anti-proliferation effect of mitochondria-accumulating ruthenium(II) complexes via redox homeostasis disturbance and energy depletion

The antiproliferative activity of three cyclometalated Ru(II) complexes with the formula [Ru(bpy)₂L]PF₆, where bpy = 2,2'-bipyridine, Ru1: L1 = phenanthro[4,5-fgh]quinoxaline; Ru2: L2 = benzo[f]naphtho[2,1-h]quinoxaline; and Ru3: L3 = phenanthro[9,10-b]pyrazine, have been synthesized and characterized. The lipophilicity of the three Ru(II) complexes was modulated by the alteration of the planarity in the ligands of the complexes. With appropriate lipophilicity, Ru1-Ru3 exhibited mitochondrial accumulating property and cytotoxic activity against a spectrum of cancer cell lines. The underlying mechanism study indicated that these Ru(II) complexes can selectively accumulate in mitochondria and disrupt physiological processes, including the redox balance and energy generation in cancer cells. Elevation of iron content in triple-negative breast cancer (MDA-MB-231 cells) was observed after treatment with Ru(II) complexes, which may contribute to the production of reactive oxygen species (ROS) via Fenton reaction chemistry. Besides, the Ru(II) complexes decreased the intracellular glutathione (GSH) in cancer cells, leading to the failure in the cells to combat oxidative damage. Both of the mentioned processes contribute to the high oxidative stress and eventually lead to cancer cell death. On the other hand, Ru1-Ru3 significantly induced the depletion of adenosine triphosphate (ATP), causing disturbance of energy generation. Moreover, the results of wound-healing assay and transwell invasion assay, as well as the tube formation assay indicated the anti-migration and anti-angiogenesis properties of Ru1-Ru3. Our study demonstrated that these Ru(II) complexes are promising chemotherapeutic agents with oxidative stress induction and energy generation disturbance.

Cytoglobin protects cancer cells from apoptosis by regulation of mitochondrial cardiolipin

Cytoglobin is important in the progression of oral squamous cell carcinoma but the molecular and cellular basis remain to be elucidated. In the current study, we develop a new cell model to study the function of cytoglobin in oral squamous carcinoma and response to cisplatin. Transcriptomic profiling showed cytoglobin mediated changes in expression of genes related to stress response, redox metabolism, mitochondrial function, cell adhesion, and fatty acid metabolism. Cellular and biochemical studies show that cytoglobin expression results in changes to phenotype associated with cancer progression including: increased cellular proliferation, motility and cell cycle progression. Cytoglobin also protects cells from cisplatin-induced apoptosis and oxidative stress with levels of the antioxidant glutathione increased and total and mitochondrial reactive oxygen species levels reduced. The mechanism of cisplatin resistance involved inhibition of caspase 9 activation and cytoglobin protected mitochondria from oxidative stress-induced fission. To understand the mechanism behind these phenotypic changes we employed lipidomic analysis and demonstrate that levels of the redox sensitive and apoptosis regulating cardiolipin are significantly up-regulated in cells expressing cytoglobin. In conclusion, our data shows that cytoglobin expression results in important phenotypic changes that could be exploited by cancer cells in vivo to facilitate disease progression.

DNA topoisomerases as additional targets for anticancer monofunctional platinum(ii) complexes

Topoisomerases are ubiquitous enzymes and important targets for DNA-oriented anticancer drugs. Two mitochondrion-targeted monofunctional platinum(ii) complexes, [Pt(ortho-PPh₃CH₂Py)(NH₃)₂Cl](NO₃)₂ (OPT) and [Pt(para-PPh₃CH₂Py)(NH₃)₂Cl](NO₃)₂ (PPT; PPh₃ = triphenylphosphonium, Py = pyridine), show significant inhibition towards the activity of DNA topoisomerases in addition to their DNA binding and mitochondrial targeting capabilities. OPT exhibits strong cytotoxicity toward the human renal clear cell carcinoma 786-O and the murine prostate cancer RM-1 cell lines. The complex could bind to the minor groove of DNA, as well as DNA topoisomerases I and IIα, thereby acting as an inhibitor of topoisomerase I/IIα and causing DNA damage. The damage was evidenced by the enhanced expression of γ-H2AX, Chk1/2 phosphorylation, p53 and cell cycle arrest in the G2/M phase. In contrast, the inhibitory effect of PPT on DNA topoisomerases was largely limited to the isolated enzymes. The results demonstrate that the cellular inhibition of the complex towards the DNA topoisomerases positively correlated with its mitochondrial accumulation. Molecular docking provided more detailed structural insights into the interactions of OPT or PPT with DNA and topoisomerase I/IIα. The binding sites of OPT and PPT in topoisomerase-DNA complexes are different from each other. Aside from previously revealed DNA and mitochondrial targets, this study discovered new evidence that DNA topoisomerases may also serve as targets of monofunctional platinum(ii) complexes. For a multispecific platinum complex, strong DNA binding ability does not necessarily lead to potent cytotoxicity as other factors including the cell types, mitochondrial accumulation, and activity of DNA topoisomerases also affect the outcome of DNA damage.

Mitochondria as a Novel Target for Cancer Chemoprevention: Emergence of Mitochondrial-targeting Agents

Cancer chemoprevention is the most effective approach to control cancer in the population. Despite significant progress, chemoprevention has not been widely adopted because agents that are safe tend to be less effective and those that are highly effective tend to be toxic. Thus, there is an urgent need to develop novel and effective chemopreventive agents, such as mitochondria-targeted agents, that can prevent cancer and prolong survival. Mitochondria, the central site for cellular energy production, have important functions in cell survival and death. Several studies have revealed a significant role for mitochondrial metabolism in promoting cancer development and progression, making mitochondria a promising new target for cancer prevention. Conjugating delocalized lipophilic cations, such as triphenylphosphonium cation (TPP+), to compounds of interest is an effective approach for mitochondrial targeting. The hyperpolarized tumor cell membrane and mitochondrial membrane potential allow for selective accumulation of TPP⁺ conjugates in tumor cell mitochondria versus those in normal cells. This could enhance direct killing of precancerous, dysplastic, and tumor cells while minimizing potential toxicities to normal cells.

Precisely Assembled Nanoparticles against Cisplatin Resistance via Cancer-Specific Targeting of Mitochondria and Imaging-Guided Chemo-Photothermal Therapy

Cisplatin resistance in tumor cells is known mainly due to the reduced accumulation of platinum ions by efflux, detoxification by intracellular GSH, and nucleotide excision repair machinery-mediated nuclear DNA repair. In this work, theranostic Pt(IV)-NPs, which are precisely self-assembled by biotin-labeled Pt(IV) prodrug derivative and cyclodextrin-functionalized IR780 in a 1:1 molecular ratio, have been developed for addressing all these hurdles via mitochondria-targeted chemotherapy solely or chemophotothermal therapy. In these nanoparticles, IR780 as a small-molecule dye acts as a mitochondria-targeting ligand to make Pt(IV)-NPs relocate finally in the mitochondria and release cisplatin. As demonstrated by in vitro and in vivo experiments, Pt(IV)-NPs can markedly facilitate cancer-specific mitochondrial targeting, inducing mitochondrial dysfunction and mitochondrial DNA (mtDNA) damage, thus greatly increasing the Pt accumulation, reducing the GSH levels, and avoiding DNA repair machinery in cisplatin-resistant cancer cells (A549R), finally resulting in significant inhibition of A549R tumor growth on animal models by chemotherapy solely. Upon near-infrared irradiation, mitochondria-targeted chemophotothermal synergistic therapy can be realized, further overcoming cisplatin resistance and even eliminating A549R tumors completely. Moreover, such novel Pt(IV)-NPs integrate multimodal targeting (cancer and mitochondria targeting), imaging (near-infrared imaging and photoacoustic imaging), and therapeutic (chemo- and photothermal therapy) moieties in a constant ratio (1:1:1) into a single, reproducible, and structurally homogeneous entity, avoiding nonuniform drug loading and premature leakage as well as the discrete steps of imaging and therapy, which thus is more beneficial for precise therapeutics and future clinical translation.

Multiaction Platinum(IV) Prodrug Containing Thymidylate Synthase Inhibitor and Metabolic Modifier against Triple-Negative Breast Cancer

Multifunctional platinum^IV anticancer prodrugs have the potential to enrich the anticancer properties and overcome the clinical problems of drug resistance and side effects of platinum^II anticancer agents. Herein, we develop dual and triple action platinum^IV complexes with targeted and biological active functionalities. One complex (PFL) that consists of cisplatin, tegafur, and lonidamine exhibits strong cytotoxicity against triple negative breast cancer (TNBC) cells. Cellular uptake and distribution studies reveal that PFL mainly accumulates in mitochondria. As a result, PFL disrupts the mitochondrial ultrastructure and induces significant alterations in the mitochondrial membrane potential, which further leads to an increase in production of reactive oxygen species (ROS) and a decrease in ATP synthesis in MDA-MB-231 TNBCs. Western blot analysis reveals the formation of ternary complex of thymidylate synthase, which shows the intracellular conversion of tegafur into 5-FU after its release from PFL. Furthermore, treatment with PFL impairs the mitochondrial function, leading to the inhibition of glycolysis and mitochondrial respiration and induction of apoptosis through the mitochondrial pathway. The RNA-sequencing experiment shows that PFL can perturb the pathways involved in DNA synthesis, DNA damage, metabolism, and transcriptional activity. These findings demonstrate that PFL intervenes in several cellular processes including DNA damage, thymidylate synthase inhibition, and perturbation of the mitochondrial bioenergetics to kill the cancer cells. The results highlight the significance of a triple-action prodrug for efficient anticancer therapy for TNBCs.

In Situ Monitoring of Mitochondria Regulating Cell Viability by the RNA-Specific Fluorescent Photosensitizer

Cell viability is greatly affected by external stimulus eliciting correlated dynamical physiological processes for cells to choose survival or death. A few fluorescent probes have been designed to detect whether the cell is in survival state or apoptotic state, but monitoring the regulation process of the cell undergoing survival to death remains a long-standing challenge. Herein, we highlight the in situ monitor of mitochondria regulating the cell viability by the RNA-specific fluorescent photosensitizer L. At normal conditions, L anchored mitochondria and interacted with mito-RNA to light up the mitochondria with red fluorescence. With external light stimulus, L generated reactive oxide species (ROS) and cause damage to mitochondria, which activated mitochondrial autophagy to prevent death, during which the red fluorescence of L witnessed dynamical distribution in accordance with the evolution of vacuole structures containing damaged mitochondria into autophagosomes. However, with ROS continuously increasing, the mitochondrial apoptosis was eventually commenced and L with red fluorescent was gradually accumulated in the nucleoli, indicating the programmed cell death. This work demonstrated how the delicate balance between survival and death are regulated by mitochondria.

A Pt(IV)-based mononitro-naphthalimide conjugate with minimized side-effects targeting DNA damage response via a dual-DNA-damage approach to overcome cisplatin resistance

Platinum(Pt)(II) drugs and new Pt(IV) agents behave the dysregulation of apoptosis as the result of DNA damage repair and thus, are less effective in the treatment of resistant tumors. Herein, mononitro-naphthalimide Pt(IV) complex 10b with minimized side-effects was reported targeting DNA damage response via a dual-DNA-damage approach to overcome cisplatin resistance. 10b displayed remarkably evaluated antitumor (70.10%) activities in vivo compared to that of cisplatin (52.88%). The highest fold increase (FI) (5.08) for A549cisR cells and the lowest (0.72) for A549 indicated 10b preferentially accumulated in resistant cell lines. The possible molecular mechanism indicates that 10b targets resistant cells in a totally different way from the existing Pt drugs. The cell accumulation and the Pt levels in genomic DNA from 10b is almost 5 folds higher than that of cisplatin and oxaliplatin, indicating the naphthalimide moiety in 10b exhibits preferentially DNA damage. Using 5'-dGMP as a DNA model, the DNA-binding properties of 10b (1 mM) with 5'-dGMP (3 mM) in the presence of ascorbic acid (5 mM) deduced that 10b was generated by the combination of cisplatin with 5'-dGMP after reduction by ascorbic acid. Moreover, 10b promoted the expression of p53 gene and protein more effectively than cisplatin, leading to the increased anticancer activity. The up-regulated γH2A.X and down-regulated RAD51 indicates that 10b not only induced severe DNA damage but also inhibited the DNA damage repair, thus resulting in its higher cytotoxicity in comparison to that of cisplatin. Their preferential accumulation in cancer cells (SMMC-7721) compared to the matched normal cells (HL-7702 cells) demonstrated that they were potentially safe for clinical therapeutic use. In addition, the higher therapeutic indices of 10b for 4T1 cells in vivo indicated that naphthalimide-Pt(IV) conjugates behaved a vital function in the treatment of breast cancer. For the first time, our study implies a significant strategy for Pt drugs to treat resistance cancer targeting DNA damage repair via dual DNA damage mechanism in a totally new field.

Recent advances in platinum-based chemotherapeutics that exhibit inhibitory and targeted mechanisms of action

Current platinum-based drugs used in chemotherapy, like cisplatin and its derivatives, are greatly limited due to side-effects and drug resistance. This has inspired the search for novel platinum-based drugs that deviate from the conventional mechanism of action seen with current chemotherapeutics. This review highlights recent advances in platinum(II) and platinum(IV)-based complexes that have been developed within the past six years. The platinum compounds explored within this review are those that display a more targeted approach by incorporating ligands that act on selected cellular targets within cancer cells. This includes mitochondria, overexpressed receptors or proteins and enzymes that contribute to cancer cell proliferation. These types of platinum compounds have shown significant improvements in anticancer activity and as such, this review highlights the importance of pursuing these new designed platinum drugs for cancer therapy, with the potential of undergoing clinical trials.

Bromocoumarinplatin, targeting simultaneously mitochondria and nuclei with p53 apoptosis pathway to overcome cisplatin resistance

Mitochondria as one of potential anticancer target, alternatively damaging mtDNA other than nDNA is a potential method for platinum-based anticancer drugs to overcome cisplatin resistance. We herein report that bromocoumarinplatin 1, a coumarin-Pt(IV) prodrug, targeted simultaneously mitochondria and nuclei with the contents of Pt in nDNA and mtDNA were 25.75% and 65.91%, respectively, which demonstrated mtDNA apoptosis played a key role in overcoming cisplatin resistance. Moreover, 1 promoted the expression of p53 gene and protein more effectively than cisplatin, leading to the increased anticancer activity of 1 through p53 pathway. The property of preferential accumulation in cancer cells (Snu-368 and Snu-739) compared to the matched normal cells (HL-7702 cells) demonstrated that 1 was potentially safe for clinical therapeutic use. In addition, the higher therapeutic indices of 1 for HCT-116 cells in vivo indicated that bromocoumarinplatin behaved a vital function in the treatment of colon cancer.

Toxoplasma gondii GRA8-derived peptide immunotherapy improves tumor targeting of colorectal cancer

Targeted tumor and efficient, specific biological drug delivery in vivo has been one of the main challenges in protein-based cancer-targeted therapies. Mitochondria are potential therapeutic targets for various anti-cancer drugs. We have previously reported that protein kinase Cα-mediated phosphorylation of Toxoplasma gondii GRA8 is required for mitochondrial trafficking and regulating the interaction of the C-terminal of GRA8 with ATP5A1/SIRT3 in mitochondria. Furthermore, SIRT3 facilitates ATP5A1 deacetylation, mitochondrial activation, and subsequent antiseptic activity in vivo. Herein we developed a recombinant acidity-triggered rational membrane (ATRAM)-conjugated multifunctional GRA8 peptide (rATRAM-G8-M/AS) comprising ATRAM as the cancer-targeting cell-penetrating peptide, and essential/minimal residues for mitochondrial targeting or ATP5A1/SIRT3 binding. This peptide construct showed considerably improved potency about cancer cell death via mitochondria activity and biogenesis compared with rGRA8 alone in HCT116 human carcinoma cells, reaching an IC₅₀ value of up to 200-fold lower in vitro and 500-fold lower in vivo. Notably, rATRAM-G8-M/AS treatment showed significant therapeutic effects in a mouse xenograft model through mitochondrial metabolic resuscitation, and it produced negligible immunogenicity and immune responses in vivo. Thus, these results demonstrate that rATRAM-G8-M/AS represents a useful therapeutic strategy against tumors, particularly colon cancer. This strategy represents an urgently needed paradigm shift for therapeutic intervention.

Cu(ii) phenanthroline–phenazine complexes dysregulate mitochondrial function and stimulate apoptosis

Herein we report the central role of the mitochondria in the cytotoxicity of four developmental cytotoxic copper(ii) complexes [Cu(phen)₂]²⁺, [Cu(DPQ)(Phen)]²⁺, [Cu(DPPZ)(Phen)]²⁺and [Cu(DPPN)(Phen)]²⁺superior to cisplatin and independent of resistance in a range of cells.

Mitochondria-targeting monofunctional platinum(ii)–lonidamine conjugates for cancer cell de-energization

We report the rational design and anticancer mechanism studies of novel mitochondria-targeting monofunctional Pt(ii)–lonidamine conjugates for the selective de-energization of cancer cells.

Antitumoral effects of mitochondria-targeting neutral and cationic cis-[bis(1,3-dibenzylimidazol-2-ylidene)Cl(L)]Pt(ii) complexes

cis-[Bis(1,3-dibenzylimidazol-2-ylidene)Pt^IICl(L)] complexes target mitochondria regardless of charge and size of ligands L, yet show different anticancer effects.

High cytotoxic and apoptotic effects of platinum(ii) complexes bearing the 4-acridinol ligand

4-Acridinol platinum(ii) complex PtA induces SK-OV-3/DDP cell apoptosis that is mediated by the mitochondrial dysfunction pathway.

Near-infrared phosphorescent terpyridine osmium(ii) photosensitizer complexes for photodynamic and photooxidation therapy

NIR phosphorescent terpyridine Os(ii) complexes can produce singlet oxygen and oxidize NADH under both blue and red light irradiation.

Potent and selective PTP1B inhibition by a platinum(ii) complex: possible implications for a new antitumor strategy

Showing anti-proliferation activity against MCF7 cells better than cisplatin, a platinum(ii) complex, [PtL(DMSO)Cl], was found to potently and selectively inhibit protein tyrosine phosphatase 1B (PTP1B), a putative target for anticancer agents, suggesting a new possible anticancer strategy based on platinum drugs.

Polyamine-Based Pt(IV) Prodrugs as Substrates for Polyamine Transporters Preferentially Accumulate in Cancer Metastases as DNA and Polyamine Metabolism Dual-Targeted Antimetastatic Agents

Diverse platinum drug candidates have been designed to improve inhibitory potency and overcome resistance for orthotopic tumors. However, the antimetastatic properties have rarely been reported. We herein report that homospermidineplatin (4a), a polyamine-Pt(IV) prodrug, can potently inhibit tumor growth in situ and reverse cisplatin resistance as expected, and more importantly, 4a displays remarkably elevated antimetastatic activity in vivo (65.7%), compared to those of cisplatin (27.0%) and oxaliplatin (19.6%). The underlying molecular mechanism indicates that in addition to targeting nuclear DNA, 4a can modulate polyamine metabolism and function in a manner different from that of cisplatin. By upregulating SSAT and PAO, 4a downregulates the concentrations of Put, Spd, and Spm, which favors the suppression of fast-growing tumor cells. Moreover, the p53/SSAT/β-catenin and PAO/ROS/GSH/GSH-Px pathways are involved in the inhibition of 4a-induced tumor metastasis. Our study implies a promising strategy for the design of platinum drugs for the treatment of terminal cancer.

ROS as a novel indicator to predict anticancer drug efficacy

Background

Mitochondria are considered a primary intracellular site of reactive oxygen species (ROS) generation. Generally, cancer cells with mitochondrial genetic abnormalities (copy number change and mutations) have escalated ROS levels compared to normal cells. Since high levels of ROS can trigger apoptosis, treating cancer cells with low doses of mitochondria-targeting / ROS-stimulating agents may offer cancer-specific therapy. This study aimed to investigate how baseline ROS levels might influence cancer cells’ response to ROS-stimulating therapy.

Methods

Four cancer and one normal cell lines were treated with a conventional drug (cisplatin) and a mitochondria-targeting agent (dequalinium chloride hydrate) separately and jointly. Cell viability was assessed and drug combination synergisms were indicated by the combination index (CI). Mitochondrial DNA copy number (mtDNAcn), ROS and mitochondrial membrane potential (MMP) were measured, and the relative expression levels of the genes and proteins involved in ROS-mediated apoptosis pathways were also investigated.

Results

Our data showed a correlation between the baseline ROS level, mtDNAcn and drug sensitivity in the tested cells. Synergistic effect of both drugs was also observed with ROS being the key contributor in cell death.

Conclusions

Our findings suggest that mitochondria-targeting therapy could be more effective compared to conventional treatments. In addition, cancer cells with low levels of ROS may be more sensitive to the treatment, while cells with high levels of ROS may be more resistant. Doubtlessly, further studies employing a wider range of cell lines and in vivo experiments are needed to validate our results. However, this study provides an insight into understanding the influence of intracellular ROS on drug sensitivity, and may lead to the development of new therapeutic strategies to improve efficacy of anticancer therapy.

A biotinylated ruthenium(ii) photosensitizer for tumor-targeted two-photon photodynamic therapy

Platinum-resistant cancer cells are sensitive to changes in the levels of reactive oxidative species (ROS). Herein, we design a biotin-modified Ru(ii) complex as a photosensitizer (denoted as Ru-Biotin). Ru-Biotin can selectively target cancer cells and produce vast amounts of singlet oxygen under two-photon excitation at 820 nm leading to cell apoptosis. Ru-Biotin is therefore an excellent candidate to overcome platinum resistance via two-photon photodynamic therapy.

A new rhodium(I) NHC complex inhibits TrxR: In vitro cytotoxicity and in vivo hepatocellular carcinoma suppression

Thioredoxin reductase (TrxR) is often overexpressed in different types of cancer cells including hepatocellular carcinoma (HCC) cells and regarded as a target with great promise for anticancer drug research and development. Here, we have synthesized and characterized nine new designed rhodium(I) N-heterocyclic carbene (NHC) complexes. All of them were effective towards cancer cells, especially complex 1e was more active than cisplatin and manifested strong antiproliferative activity against HCC cells. In vivo anticancer studies showed that 1e significantly repressed tumor growth in an HCC nude mouse model and ameliorated liver lesions in a chronic HCC model caused by CCl₄. Notably, a mechanistic study revealed that 1e can strongly inhibit TrxR system both in vitro and in vivo. Furthermore, 1e promoted intracellular ROS accumulation, damaged mitochondrial membrane potential, promoted cancer cell apoptosis and blocked the cells in the G1 phase.