Approaches for targeting mitochondria in cancer therapy

The natural product mensacarcin induces mitochondrial toxicity and apoptosis in melanoma cells

Mensacarcin is a highly oxygenated polyketide that was first isolated from soil-dwelling Streptomyces bacteria. It exhibits potent cytostatic properties (mean of 50% growth inhibition = 0.2 μm) in almost all cell lines of the National Cancer Institute (NCI)-60 cell line screen and relatively selective cytotoxicity against melanoma cells. Moreover, its low COMPARE correlations with known standard antitumor agents indicate a unique mechanism of action. Effective therapies for managing melanoma are limited, so we sought to investigate mensacarcin's unique cytostatic and cytotoxic effects and its mode of action. By assessing morphological and biochemical features, we demonstrated that mensacarcin activates caspase-3/7-dependent apoptotic pathways and induces cell death in melanoma cells. Upon mensacarcin exposure, SK-Mel-28 and SK-Mel-5 melanoma cells, which have the BRAF^V600E mutation associated with drug resistance, showed characteristic chromatin condensation as well as distinct poly(ADP-ribose)polymerase-1 cleavage. Flow cytometry identified a large population of apoptotic melanoma cells, and single-cell electrophoresis indicated that mensacarcin causes genetic instability, a hallmark of early apoptosis. To visualize mensacarcin's subcellular localization, we synthesized a fluorescent mensacarcin probe that retained activity. The natural product probe was localized to mitochondria within 20 min of treatment. Live-cell bioenergetic flux analysis confirmed that mensacarcin disturbs energy production and mitochondrial function rapidly. The subcellular localization of the fluorescently labeled mensacarcin together with its unusual metabolic effects in melanoma cells provide evidence that mensacarcin targets mitochondria. Mensacarcin's unique mode of action suggests that it may be a useful probe for examining energy metabolism, particularly in BRAF-mutant melanoma, and represent a promising lead for the development of new anticancer drugs.

Centrifugation-Free Magnetic Isolation of Functional Mitochondria Using Paramagnetic Iron Oxide Nanoparticles

Subcellular fractionation techniques are essential for cell biology and drug development studies. The emergence of organelle-targeted nanoparticle (NP) platforms necessitates the isolation of target organelles to study drug delivery and activity. Mitochondria-targeted NPs have attracted the attention of researchers around the globe, since mitochondrial dysfunctions can cause a wide range of diseases. Conventional mitochondria isolation methods involve high-speed centrifugation. The problem with high-speed centrifugation-based isolation of NP-loaded mitochondria is that NPs can pellet even if they are not bound to mitochondria. We report development of a mitochondria-targeted paramagnetic iron oxide nanoparticle, Mito-magneto, that enables isolation of mitochondria under the influence of a magnetic field. Isolation of mitochondria using Mito-magneto eliminates artifacts typically associated with centrifugation-based isolation of NP-loaded mitochondria, thus producing intact, pure, and respiration-active mitochondria. © 2017 by John Wiley & Sons, Inc.

Charge-Reversible Multifunctional HPMA Copolymers for Mitochondrial Targeting

Mitochondrial-oriented delivery of anticancer drugs has been considered as a promising strategy to improve the antitumor efficiency of chemotherapeutics. However, the physiological and biological barriers from the injection site to the final mitochondrial action site remain great challenges. Herein, a novel mitochondrial-targeted multifunctional nanocomplex based on N-(2-hydroxypropyl) methacrylamide (HPMA) copolymers (MPC) is designed to enhance drug accumulation in mitochondria. MPC possesses various functions such as extracellular pH response, superior cellular uptake, lysosomal escape, and mitochondrial targeting. In detail, MPC was formed by two oppositely charged HPMA copolymers, that is, positively charged mitochondrial-targeting guanidine group-modified copolymers and charge-reversible 2,3-dimethylmaleic anhydride (DMA)-modified copolymers (P-DMA). It was validated that MPC could remain stable in the blood circulation (pH 7.4) but could be cleaved to expose the positive charge of the guanidine group immediately in response to the mild acidity of tumor tissues (pH 6.5). The gradual exposure of positively charged guanidine will simultaneously facilitate endocytosis, endosomal/lysosomal escape, and mitochondrial targeting. The in vitro experiments showed that compared with copolymers without guanidine modification, the cellular uptake and mitochondrial-targeting ability of MPC in the simulated tumor environment (MPC@pH6.5) separately increased 4.3- and 23.8-fold, respectively. The in vivo experiments were processed on B16F10 tumor-bearing C57 mice, and MPC showed the highest accumulation in the tumor site and a peak tumor inhibition rate of 82.9%. In conclusion, multifunctional mitochondrial-targeting HPMA copolymers provide a novel and versatile approach for cancer therapy.

Functional nanosome for enhanced mitochondria-targeted gene delivery and expression

Mitochondria dysfunction plays a role in many human diseases. Therapeutic techniques for these disorders require novel delivery systems that can specifically target and penetrate mitochondria. In this study, we report a novel nanosome composed of dequalinium-DOTAP-DOPE (1,2 dioleoyl-3-trimethylammonium-propane-1,2-dioleoyl-sn-glycero-3-phosphoethanolamine) (DQA80s) as a potential mitochondria-targeting delivery vector. The functional DQAsome, DQA80s, showed enhanced transfection efficiency compared to a vector DQAsomes in HeLa cells and dermal fibroblasts. In addition, DQA80s/pDNA complexes exhibited rapid escape from the endosome into the cytosol. We observed the delivery of pDNA to mitochondria in living cells using flow cytometry, confocal microscopy, and TME imaging. More specifically, we confirmed our results by co-localization of hmtZsGreen constructs to mitochondria when delivered via DQAsomes and DQA80s in living cells. The mitochondria-targeting DQAsomes and DQA80s induced mitochondrial dysfunction through depolarization of mitochondrial membrane potential. Our data demonstrate that DQA80s show promise for use as a mitochondria-targeted carrier system for treatment of mitochondria diseases in vivo.

Bioreducible Poly(ethylene glycol)-Triphenylphosphonium Conjugate as a Bioactivable Mitochondria-Targeting Nanocarrier

Bioactivable nanocarrier systems have favorable characteristics such as high cellular uptake, target specificity, and an efficient intracellular release mechanism. In this study, we developed a bioreducible methoxy polyethylene glycol (mPEG)-triphenylphosphonium (TPP) conjugate (i.e., mPEG-(ss-TPP)₂ conjugate) as a vehicle for mitochondrial drug delivery. A bioreducible linkage with two disulfide bond-containing end groups was used at one end of the hydrophilic mPEG for conjugation with lipophilic TPP molecules. The amphiphilic mPEG-(ss-TPP)₂ self-assembled in aqueous media, which thereby formed core-shell structured nanoparticles (NPs) with good colloidal stability, and efficiently encapsulated the lipophilic anticancer drug doxorubicin (DOX). The DOX-loaded mPEG-(ss-TPP)₂ NPs were characterized in terms of their physicochemical and morphological properties, drug-loading and release behaviors, in vitro anticancer effects, and mitochondria-targeting capacity. Our results suggest that bioreducible DOX-loaded mPEG-(ss-TPP)₂ NPs can induce fast drug release with enhanced mitochondrial uptake and have a better therapeutic effect than nonbioreducible NPs.

A Multi-Mitochondrial Anticancer Agent that Selectively Kills Cancer Cells and Overcomes Drug Resistance

Mitochondria are double-membrane-bound organelles involved mainly in supplying cellular energy, but also play roles in signaling, cell differentiation, and cell death. Mitochondria are implicated in carcinogenesis, and therefore dozens of lethal signal transduction pathways converge on these organelles. Accordingly, mitochondria provide an alternative target for cancer management. In this study, F16, a drug that targets mitochondria, and chlorambucil (CBL), which is indicated for the treatment of selected human neoplastic diseases, were covalently linked, resulting in the synthesis of a multi-mitochondrial anticancer agent, FCBL. FCBL can associate with human serum albumin (HSA) to form an HSA-FCBL nanodrug, which selectively recognizes cancer cells, but not normal cells. Systematic investigations show that FCBL partially accumulates in cancer cell mitochondria to depolarize mitochondrial membrane potential (MMP), increase reactive oxygen species (ROS), and attack mitochondrial DNA (mtDNA). With this synergistic effect on multiple mitochondrial components, the nanodrug can effectively kill cancer cells and overcome multiple drug resistance. Furthermore, based on its therapeutic window, HSA-FCBL exhibits clinically significant differential cytotoxicity between normal and malignant cells. Finally, while drug dosage and drug resistance typically limit first-line mono-chemotherapy, HSA-FCBL, with its ability to compromise mitochondrial membrane integrity and damage mtDNA, is expected to overcome those limitations to become an ideal candidate for the treatment of neoplastic disease.

Mitochondria-Targeted Agents: Mitochondriotropics, Mitochondriotoxics, and Mitocans

Mitochondria, the powerhouse of the cell, have been known for many years for their central role in the energy metabolism; however, extensive progress has been made and to date substantial evidence demonstrates that mitochondria play a critical role not only in the cell bioenergetics but also in the entire cell metabolome. Mitochondria are also involved in the intracellular redox poise, the regulation of calcium homeostasis, and the generation of reactive oxygen species (ROS), which are crucial for the control of a variety of signaling pathways. Additionally, they are essential for the mitochondrial-mediated apoptosis process. Thus, it is not surprising that disruptions of mitochondrial functions can lead or be associated with human pathologies. Because of diseases like diabetes, Alzheimer, Parkinson's, cancer, and ischemic disease are being increasingly linked to mitochondrial dysfunctions, the interest in mitochondria as a prime pharmacological target has dramatically risen over the last decades and as a consequence a large number of agents, which could potentially impact or modulate mitochondrial functions, are currently under investigation. Based on their site of action, these agents can be classified as mitochondria-targeted and non-mitochondria-targeted agents. As a result of the continuous search for new agents and the design of potential therapeutic agents to treat mitochondrial diseases, terms like mitochondriotropics, mitochondriotoxics, mitocancerotropics, and mitocans have emerged to describe those agents with high affinity to mitochondria that exert a therapeutic or deleterious effect on these organelles. In this chapter, mitochondria-targeted agents and some strategies to deliver agents to and/or into mitochondria will be reviewed.

Water-soluble mitochondria-targeting polymeric prodrug micelles for fluorescence monitoring and high intracellular anticancer efficiency

Based on TPP modification on the branch of mPEG, mitochondria-targeting prodrugs micelles realize better mitochondria target, high anticancer efficiency and a faster release at alkaline pH.

Integrating Enzymatic Self-Assembly and Mitochondria Targeting for Selectively Killing Cancer Cells without Acquired Drug Resistance

Targeting organelles by modulating the redox potential of mitochondria is a promising approach to kill cancer cells that minimizes acquired drug resistance. However, it lacks selectivity because mitochondria perform essential functions for (almost) all cells. We show that enzyme-instructed self-assembly (EISA), a bioinspired molecular process, selectively generates the assemblies of redox modulators (e.g., triphenyl phosphinium (TPP)) in the pericellular space of cancer cells for uptake, which allows selectively targeting the mitochondria of cancer cells. The attachment of TPP to a pair of enantiomeric, phosphorylated tetrapeptides produces the precursors (L-1P or D-1P) that form oligomers. Upon dephosphorylation catalyzed by ectophosphatases (e.g., alkaline phosphatase (ALP)) overexpressed on cancer cells (e.g., Saos2), the oligomers self-assemble to form nanoscale assemblies only on the surface of the cancer cells. The cancer cells thus uptake these assemblies of TPP via endocytosis, mainly via a caveolae/raft-dependent pathway. Inside the cells, the assemblies of TPP-peptide conjugates escape from the lysosome, induce dysfunction of mitochondria to release cytochrome c, and result in cell death, while the controls (i.e., omitting TPP motif, inhibiting ALP, or removing phosphate trigger) hardly kill the Saos2 cells. Most importantly, the repeated stimulation of the cancers by the precursors, unexpectedly, sensitizes the cancer cells to the precursors. As the first example of the integration of subcellular targeting with cell targeting, this study validates the spatial control of the assemblies of nonspecific cytotoxic agents by EISA as a promising molecular process for selectively killing cancer cells without inducing acquired drug resistance.

Dihydroergotamine Tartrate Induces Lung Cancer Cell Death through Apoptosis and Mitophagy

BACKGROUND

Mitochondria have emerged as a major target for anticancer therapy because of their critical role in cancer cell survival. Our preliminary works have suggested that dihydroergotamine tartrate (DHE), an antimigraine agent, may have effects on mitochondria.

METHODS

We examined the effect of DHE on the survival of several lung cancer cells and confirmed that DHE suppressed diverse lung cancer cell growth effectively. To confirm whether such effects of DHE would be associated with mitochondria, A549 cells were employed for the evaluation of several important parameters, such as membrane potential, reactive oxygen species (ROS) generation, apoptosis, ATP production and autophagy.

RESULTS

DHE decreased membrane permeability, increased ROS generation as well as apoptosis, and disturbed ATP production. Eventually, mitophagy was activated for damaged mitochondria.

CONCLUSION

Taken together, our findings demonstrate that DHE induces lung cancer cell death by the induction of apoptosis and mitophagy, thus suggesting that DHE can be developed as an anti-lung cancer therapeutic agent.

The pathogenesis and treatment of cardiac atrophy in cancer cachexia

Cancer cachexia is a multifactorial syndrome characterized by a progressive loss of skeletal muscle mass associated with significant functional impairment. In addition to a loss of skeletal muscle mass and function, many patients with cancer cachexia also experience cardiac atrophy, remodeling, and dysfunction, which in the field of cancer cachexia is described as cardiac cachexia. The cardiac alterations may be due to underlying heart disease, the cancer itself, or problems initiated by the cancer treatment and, unfortunately, remains largely underappreciated by clinicians and basic scientists. Despite recent major advances in the treatment of cancer, little progress has been made in the treatment of cardiac cachexia in cancer, and much of this is due to lack of information regarding the mechanisms. This review focuses on the cardiac atrophy associated with cancer cachexia, describing some of the known mechanisms and discussing the current and future therapeutic strategies to treat this condition. Above all else, improved awareness of the condition and an increased focus on identification of mechanisms and therapeutic targets will facilitate the eventual development of an effective treatment for cardiac atrophy in cancer cachexia.

Cellular and Mitochondrial Dual-Targeted Organic Dots with Aggregation-Induced Emission Characteristics for Image-Guided Photodynamic Therapy

Targeted delivery of drugs toward mitochondria of specific cancer cells dramatically improves therapy efficiencies especially for photodynamic therapy (PDT), as reactive oxygen species (ROS) are short in lifetime and small in radius of action. Different from chemical modification, nanotechnology has been serving as a simple and nonchemical approach to deliver drugs to cells of interest or specific organelles, such as mitochondria, but there have been limited examples of dual-targeted delivery for both cells and mitochondria. Here, cellular and mitochondrial dual-targeted organic dots for image-guided PDT are reported based on a fluorogen with aggregation-induced emission (AIEgen) characteristics. The AIEgen possesses enhanced red fluorescence and efficient ROS production in aggregated states. The AIE dot surfaces are functionalized with folate and triphenylphosphine, which can selectively internalize into folate-receptor (FR) positive cancer cells, and subsequently accumulate at mitochondria. The direct ROS generation at mitochondria sites is found to depolarize mitochondrial membrane, affect cell migration, and lead to cell apoptosis and death with enhanced PDT effects as compared to ROS generated randomly in cytoplasm. This report demonstrates a simple and general nanocarrier approach for cellular and mitochondrial dual-targeted PDT, which opens new opportunities for dual-targeted delivery and therapy.

Targeting mitochondrial function for the treatment of breast cancer

There are many approaches used to control breast cancer, although the most efficient strategy is the reactivation of apoptosis. Since mitochondria play an important role in cellular metabolism and homeostasis, as well as in the regulation of cell death pathways, we focus here on metabolic remodeling and mitochondrial alterations present in breast tumor cells. We review strategies including classes of compounds and delivery systems that target metabolic and specific mitochondrial alterations to kill tumor cells without affecting their normal counterparts. We present here the arguments for the improvement of already existent molecules and the design of novel promising anticancer drug candidates that target breast cancer mitochondria.

Advances in the research and development of natural health products as main stream cancer therapeutics

Natural health products (NHPs) are defined as natural extracts containing polychemical mixtures; they play a leading role in the discovery and development of drugs, for disease treatment. More than 50% of current cancer therapeutics are derived from natural sources. However, the efficacy of natural extracts in treating cancer has not been explored extensively. Scientific research into the validity and mechanism of action of these products is needed to develop NHPs as main stream cancer therapy. The preclinical and clinical validation of NHPs would be essential for this development. This review summarizes some of the recent advancements in the area of NHPs with anticancer effects. This review also focuses on various NHPs that have been studied to scientifically validate their claims as anticancer agents. Furthermore, this review emphasizes the efficacy of these NHPs in targeting the multiple vulnerabilities of cancer cells for a more selective efficacious treatment. The studies reviewed here have paved the way for the introduction of more NHPs from traditional medicine to the forefront of modern medicine, in order to provide alternative, safer, and cheaper complementary treatments for cancer therapy and possibly improve the quality of life of cancer patients.

Synthesis of triphenylphosphonium phospholipid conjugates for the preparation of mitochondriotropic liposomes

Surface modification of liposomes with a ligand is facilitated by the conjugation of the ligand to a hydrophobic molecule that serves to anchor the ligand to the liposomal bilayer. We describe here a simple protocol to conjugate a triphenylphosphonium group to several commercially available functionalized phospholipids. The resulting triphenylphosphonium conjugated lipids can be used to prepare liposomes that preferentially associate with mitochondria when exposed to live mammalian cells in culture.

In vivo selective cancer-tracking gadolinium eradicator as new-generation photodynamic therapy agent

In this work, we demonstrate a modality of photodynamic therapy (PDT) through the design of our truly dual-functional--PDT and imaging--gadolinium complex (Gd-N), which can target cancer cells specifically. In the light of our design, the PDT drug can specifically localize on the anionic cell membrane of cancer cells in which its laser-excited photoemission signal can be monitored without triggering the phototoxic generation of reactive oxygen species--singlet oxygen--before due excitation. Comprehensive in vitro and in vivo studies had been conducted for the substantiation of the effectiveness of Gd-N as such a tumor-selective PDT photosensitizer. This treatment modality does initiate a new direction in the development of "precision medicine" in line with stem cell and gene therapies as tools in cancer therapy.

Core-shell nanoparticle-based peptide therapeutics and combined hyperthermia for enhanced cancer cell apoptosis

Mitochondria-targeting peptides have garnered immense interest as potential chemotherapeutics in recent years. However, there is a clear need to develop strategies to overcome the critical limitations of peptides, such as poor solubility and the lack of target specificity, which impede their clinical applications. To this end, we report magnetic core-shell nanoparticle (MCNP)-mediated delivery of a mitochondria-targeting pro-apoptotic amphipathic tail-anchoring peptide (ATAP) to malignant brain and metastatic breast cancer cells. Conjugation of ATAP to the MCNPs significantly enhanced the chemotherapeutic efficacy of ATAP, while the presence of targeting ligands afforded selective delivery to cancer cells. Induction of MCNP-mediated hyperthermia further potentiated the efficacy of ATAP. In summary, a combination of MCNP-mediated ATAP delivery and subsequent hyperthermia resulted in an enhanced effect on mitochondrial dysfunction, thus resulting in increased cancer cell apoptosis.

Disruption of mitochondrial complexes in cancer stem cells through nano-based drug delivery: a promising mitochondrial medicine

Mitochondria are the fulcrum for regulating cellular metabolism as well as apoptosis. The multi-lamellar vesicles (MLVs) liposome targeted against mitochondria can be formulated to disrupt mitochondrial integrity to attain programmed cell death of cancer stem cells (CSCs). The gold nanoparticles (GNPs) and a steroid nucleus (cyclopentanoperhydrophenanthrene ring) are encapsulated within MLV liposome that targets specifically to the CD44 receptor of the CSCs. Entering cytosol, it would bind distinctively to the malate-aspartate shuttle through a specifically designed ligand. Liposome fuses with the mito-membrane after associating with shuttle, thereby releasing both the components. The steroid disrupts mito-membrane's integrity facilitating release of cytochrome c. Thus, GNPs enter into the mitosol and interact with the mitochondrial complexes to cease cellular respiration. Since the solid nano-based pharmaceutics has shown a lot of promises as a potent anticancer therapy, the role of MLV liposome can be proved to be a better weapon to terminate malignancy.

Harnessing system models of cell death signalling for cytotoxic chemotherapy: towards personalised medicine approaches?

Most cytotoxic chemotherapeutics are believed to kill cancer cells by inducing apoptosis. Understanding the factors that contribute to impairment of apoptosis in cancer cells is therefore critical for the development of novel therapies that circumvent the widespread chemoresistance. Apoptosis, however, is a complex and tightly controlled process that can be induced by different classes of chemotherapeutics targeting different signalling nodes and pathways. Moreover, apoptosis initiation and apoptosis execution strongly depend on patient-specific, genomic and proteomic signatures. Here, we will review recent translational studies that suggest a critical link between the sensitivity of cancer cells to initiate apoptosis and clinical outcome. Next we will discuss recent advances in the field of system modelling of apoptosis pathways for the prediction of treatment responses. We propose that initiation of mitochondrial apoptosis, defined as the process of mitochondrial outer membrane permeabilisation (MOMP), is a dose-dependent decision process that allows for a prediction of individual therapy responses and therapeutic windows. We provide evidence in contrast that apoptosis execution post-MOMP may be a binary decision that dictates whether apoptosis is executed or not. We will discuss the implications of this concept for the future use of novel adjuvant therapeutics that specifically target apoptosis signalling pathways or which may be used to reduce the impact of cell-to-cell heterogeneity on therapy responses. Finally, we will discuss the technical and regulatory requirements surrounding the use and implications of system-based patient stratification tools for the future of personalised oncology.

Alkyne-azide "click" chemistry in designing nanocarriers for applications in biology

The alkyne-azide cycloaddition, popularly known as the "click" reaction, has been extensively exploited in molecule/macromolecule build-up, and has offered tremendous potential in the design of nanomaterials for applications in a diverse range of disciplines, including biology. Some advantageous characteristics of this coupling include high efficiency, and adaptability to the environment in which the desired covalent linking of the alkyne and azide terminated moieties needs to be carried out. The efficient delivery of active pharmaceutical agents to specific organelles, employing nanocarriers developed through the use of "click" chemistry, constitutes a continuing topical area of research. In this review, we highlight important contributions click chemistry has made in the design of macromolecule-based nanomaterials for therapeutic intervention in mitochondria and lipid droplets.

CHOP THERAPY INDUCED MITOCHONDRIAL REDOX STATE ALTERATION IN NON-HODGKIN'S LYMPHOMA XENOGRAFTS

We are interested in investigating whether cancer therapy may alter the mitochondrial redox state in cancer cells to inhibit their growth and survival. The redox state can be imaged by the redox scanner that collects the fluorescence signals from both the oxidized-flavoproteins (Fp) and the reduced form of nicotinamide adenine dinucleotide (NADH) in snap-frozen tissues and has been previously employed to study tumor aggressiveness and treatment responses. Here, with the redox scanner we investigated the effects of chemotherapy on mouse xenografts of a human diffuse large B-cell lymphoma cell line (DLCL2). The mice were treated with CHOP therapy, i.e., cyclophosphamide (C) + hydroxydoxorubicin (H) + Oncovin (O) + prednisone (P) with CHO administration on day 1 and prednisone administration on days 1-5. The Fp content of the treated group was significantly decreased (p = 0.033) on day 5, and the mitochondrial redox state of the treated group was slightly more reduced than that of the control group (p = 0.048). The decrease of the Fp heterogeneity (measured by the mean standard deviation) had a border-line statistical significance (p = 0.071). The result suggests that the mitochondrial metabolism of lymphoma cells was slightly suppressed and the lymphomas became less aggressive after the CHOP therapy.

Mapping the redox state of CHOP-treated non-Hodgkin's lymphoma xenografts in mice

Drug treatment may alter the metabolism of cancer cells and may alter the mitochondrial redox state. Using the redox scanner that collects the fluorescence signals from both the oxidized flavoproteins (Fp) and the reduced form of nicotinamide adenine dinucleotide (NADH) in snap-frozen tumor tissues, we investigated the effects of chemotherapy on mouse xenografts of a human diffuse large B-cell lymphoma cell line (DLCL2). The mice in the treatment group were treated with CHOP - cyclophosphamide (C) + hydroxydoxorubicin (H) + Oncovin (O) + prednisone (P) using the following regimen: CHO administration on day 1 followed by prednisone administration on day 1-5. On day 5 the mitochondrial redox state of the treated group was slightly more reduced than that of the control group (p = 0.049), and the Fp content of the treated group was significantly decreased (p = 0.033).

Solid-phase route to Fmoc-protected cationic amino acid building blocks

Diamino acids are commonly found in bioactive compounds, yet only few are commercially available as building blocks for solid-phase peptide synthesis. In the present work a convenient, inexpensive route to multiple-charged amino acid building blocks with varying degree of hydrophobicity was developed. A versatile solid-phase protocol leading to selectively protected amino alcohol intermediates was followed by oxidation to yield the desired di- or polycationic amino acid building blocks in gram-scale amounts. The synthetic sequence comprises loading of (S)-1-(p-nosyl)aziridine-2-methanol onto a freshly prepared trityl bromide resin, followed by ring opening with an appropriate primary amine, on-resin N(β)-Boc protection of the resulting secondary amine, exchange of the N(α)-protecting group, cleavage from the resin, and finally oxidation in solution to yield the target γ-aza substituted building blocks having an Fmoc/Boc protection scheme. This strategy facilitates incorporation of multiple positive charges into the building blocks provided that the corresponding partially protected di- or polyamines are available. An array of compounds covering a wide variety of γ-aza substituted analogs of simple neutral amino acids as well as analogs displaying high bulkiness or polycationic side chains was prepared. Two building blocks were incorporated into peptide sequences using microwave-assisted solid-phase peptide synthesis confirming their general utility.

Design and evaluation of multifunctional nanocarriers for selective delivery of coenzyme Q10 to mitochondria

Impairments of mitochondrial functions have been associated with failure of cellular functions in different tissues, leading to various pathologies. We report here a mitochondria-targeted nanodelivery system for coenzyme Q10 (CoQ10) that can reach mitochondria and deliver CoQ10 in adequate quantities. Multifunctional nanocarriers based on ABC miktoarm polymers (A = poly(ethylene glycol (PEG), B = polycaprolactone (PCL), and C = triphenylphosphonium bromide (TPPBr)) were synthesized using a combination of click chemistry with ring-opening polymerization, self-assembled into nanosized micelles, and were employed for CoQ10 loading. Drug loading capacity (60 wt %), micelle size (25-60 nm), and stability were determined using a variety of techniques. The micelles had a small critical association concentration and were colloidally stable in solution for more than 3 months. The extraordinarily high CoQ10 loading capacity in the micelles is attributed to good compatibility between CoQ10 and PCL, as indicated by the low Flory-Huggins interaction parameter. Confocal microscopy studies of the fluorescently labeled polymer analog together with the mitochondria-specific vital dye label indicated that the carrier did indeed reach mitochondria. The high CoQ10 loading efficiency allowed testing of micelles within a broad concentration range and provided evidence for CoQ10 effectiveness in two different experimental paradigms: oxidative stress and inflammation. Combined results from chemical, analytical, and biological experiments suggest that the new miktoarm-based carrier provides a suitable means of CoQ10 delivery to mitochondria without loss of drug effectiveness. The versatility of the click chemistry used to prepare this new mitochondria-targeting nanocarrier offers a widely applicable, simple, and easily reproducible procedure to deliver drugs to mitochondria or other intracellular organelles.

Mitochondria and cancer: a growing role in apoptosis, cancer cell metabolism and dedifferentiation

At the beginning of the twentieth century, Otto Warburg demonstrated that cancer cells have a peculiar metabolism. These cells preferentially utilise glycolysis for energetic and anabolic purposes, producing large quantities of lactic acid. He defined this unusual metabolism "aerobic glycolysis". At the same time, Warburg hypothesised that a disruption of mitochondrial activities played a precise pathogenic role in cancer. Because of this so-called "Warburg effect", mitochondrial physiology and cellular respiration in particular have been overlooked in pathophysiological studies of cancer. Over time, however, many studies have shown that mitochondria play a fundamental role in cell death by apoptosis or necrosis. Moreover, metabolic enzymes of the Krebs cycle have also recently been recognised as oncosuppressors. Recently, a series of studies were undertaken to re-evaluate the role of oxidative mitochondrial metabolism in cancer cell growth and progression. Some of these data indicate that modulation of mitochondrial respiration may induce an arrest of cancer cell proliferation and differentiation (pseudodifferentiation) and/or or death, suggesting that iatrogenic manipulation of some mitochondrial activities may induce anticancer effects. Moreover, studying the role of mitochondria in cancer cell dedifferentiation/differentiation processes may allow further insight into the pathophysiology and therapy of so-called cancer stem cells.

Gold(I) complexes of water-soluble diphos-type ligands: synthesis, anticancer activity, apoptosis and thioredoxin reductase inhibition

Gold(I) complexes of imidazole and thiazole-based diphos type ligands were prepared and their potential as chemotherapeutics investigated. Depending on the ligands employed and the reaction conditions complexes [L(AuCl)(2)] and [L(2)Au]X (X = Cl, PF(6)) are obtained. The ligands used are diphosphanes with azoyl substituents R(2)P(CH(2))(2)PR(2) {R = 1-methylimidazol-2-yl (1), 1-methylbenzimidazol-2-yl (4), thiazol-2-yl (5) and benzthiazol-2-yl (6)} as well as the novel ligands RPhP(CH(2))(2)PRPh {R = 1-methylimidazol-2-yl (3)} and R(2)P(CH(2))(3)PR(2) {R = 1-methylimidazol-2-yl (2)}. The cytotoxic activity of the complexes was assessed against three human cancer cell lines and a rat hepatoma cell line and correlated to the lipophilicity of the compounds. The tetrahedral gold complexes [(3)(2)Au]PF(6) and [(5)(2)Au]PF(6) with intermediate lipophilicity (logD(7.4) = 0.21 and 0.25) showed significant cytotoxic activity in different cell lines. Both compounds induce apoptosis and inhibit the enzymes thioredoxin reductase and glutathione reductase.