Effects of the antitumoural dequalinium on NB4 and K562 human leukemia cell lines. Mitochondrial implication in cell death

Leukemia cells accumulate zinc for oncofusion protein stabilization

Acute promyelocytic leukemia (APL) and chronic myeloid leukemia (CML) are both hematological malignancies characterized by genetic alterations leading to the formation of oncofusion proteins. The classical chromosomal aberrations in APL and CML result in the PML-RARα and BCR-ABL1 oncofusion proteins, respectively. Interestingly, our flow cytometric analyses revealed elevated free intracellular zinc levels in various leukemia cells, which may play a role in stabilizing oncofusion proteins in leukemia and thus support cell proliferation and malignancy. Long-term zinc deficiency resulted in the degradation of PML-RARα in NB4 cells (APL cell line) and of BCR-ABL1 in K562 cells (CML cell line). This degradation may be explained by increased caspase 3 activity observed in zinc deficient cells, whereas zinc reconstitution normalized the caspase 3 activity and abolished zinc deficiency-induced oncofusion protein degradation. In NB4 cells, fluorescence microscopic images further indicated enlarged and enriched lysosomes during zinc deficiency, suggesting increased rates of autophagy. Moreover, NB4 cells exhibited increased expression of the zinc transporters ZIP2, ZIP10 and ZnT3 during zinc deficiency and revealed excessive accumulation of zinc in contrast to healthy peripheral blood mononuclear cells (PBMCs), when zinc was abundantly available extracellularly. Our results highlight the importance of altered zinc homeostasis for some characteristics in leukemia cells, uncover potential pathways underlying the effects of zinc deficiency in leukemia cells, and provide potential alternative strategies by which oncofusion proteins can be degraded.

Scorpion Venom Peptide Smp24 Revealed Apoptotic and Antiangiogenic Activities in Solid-Ehrlich Carcinoma Bearing Mice

Scorpion venom contains various peptides that could be utilized to treat various diseases, including cancer. This study aimed to evaluate the anti-cancer activity of scorpion venom peptide (Smp24) using a solid Ehrlich Carcinoma (SEC) mice model. SEC model was established by subcutaneous transplantation of SEC cells into Swiss albino female mice afterward subcutaneous injection of the Smp24 peptide compared to 5-Fluorouracil (5-FU) as a standard drug. Various biochemical, hematological, histopathological, immunohistochemical, and molecular (western blotting and RT-PCR) assays were performed to evaluate the antitumor activity of Smp24. Results revealed that Smp24 peptide significantly reduced tumor volume. Interestingly, Smp24 peptide significantly restored normal body functions in cancer-treated groups by maintaining HB, RBC’s, and WBC’s levels, reducing the elevated serum ALT and AST, and increasing total protein and albumin as well as enhancing antioxidant status through reducing the level of MDA and NO and elevating GSH, SOD, and CAT levels. Moreover, it restored the normal morphology of the liver and kidney tissues and improved hematological parameters in cancer-treated animals. Smp24 induced apoptosis in SEC cells, through upregulation of caspase-3 and BAX and the downregulation of VEGF, Bcl-2, p53, PCNA, and Ki67. Moreover, results exhibited the apoptotic and antiangiogenic effects of Smp24 against SEC cancer cells. These findings supported our previous results about the anti-cancer efficacy of Smp24 and made it a good candidate for developing effective and safe anti-cancer agents.

Dequalinium chloride is an antagonists of α7 nicotinic acetylcholine receptors

Dequalinium chloride has been used primarily as antiseptic compounds, but recently has been investigated for its effects on specific targets, including muscarinic acetylcholine receptors. Here we investigated dequalinium chloride as an antagonist to α7 nicotinic acetylcholine receptors. The pharmacological properties of dequalinium were established using cell lines stably co-transfected with the calcium-permeable human α7 nicotinic acetylcholine receptors and its chaperone NACHO, calcium dye fluorescent measurements or a calcium-sensitive protein reporter, and patch clamp recording of ionic currents. Using calcium dye fluorescence plate reader measurements, we find dequalinium chloride is an antagonist of α7 nicotinic acetylcholine receptors with an IC₅₀ of 672 nM in response to activation with 500 μM acetylcholine chloride and positive allosteric modulator PNU-120596. However, using a membrane-tethered GCAMP7s calcium reporter allowed detection of α7-mediated calcium flux in the absence of PNU-120596. Using this approach revealed an IC₅₀ of 157 nM for dequalinium on 300 μM acetylcholine-evoked currents. Using patch clamp recordings with 300 μM acetylcholine chloride and 10 μM PNU-120596, we find lower concentrations are sufficient to block ionic currents, with IC₅₀ of 120 nM for dequalinium chloride and 54 nM for the related UCL 1684 compound. In summary, we find that dequalinium chloride and UCL1684, which are generally used to block SK-type potassium channels, are also highly effective antagonists of α7 nicotinic acetylcholine receptors. This finding, in combination with previous studies of muscarinic acetylcholine receptors, clearly establishes dequalinium compounds within the class of general anti-cholinergic antagonists.

Stingless Bee Propolis: New Insights for Anticancer Drugs

Natural products are important sources of biomolecules possessing antitumor activity and can be used as anticancer drug prototypes. The rich biodiversity of tropical and subtropical regions of the world provides considerable bioprospecting potential, including the potential of propolis produced by stingless bee species. Investigations of the potential of these products are extremely important, not only for providing a scientific basis for their use as adjuvants for existing drug therapies but also as a source of new and potent anticancer drugs. In this context, this article organizes the main studies describing the anticancer potential of propolis from different species of stingless bees with an emphasis on the chemical compounds, mechanisms of action, and cell death profiles. These mechanisms include apoptotic events; modulation of BAX, BAD, BCL2-L1 (BCL-2 like 1), and BCL-2; depolarization of the mitochondrial membrane; increased caspase-3 activity; poly (ADP-ribose) polymerase (PARP) cleavage; and cell death induction by necroptosis via receptor interacting protein kinase 1 (RIPK1) activation. Additionally, the correlation between compounds with antioxidant and anti-inflammatory potential is demonstrated that help in the prevention of cancer development. In summary, we highlight the important antitumor potential of propolis from stingless bees, but further preclinical and clinical trials are needed to explore the selectivity, efficacy, and safety of propolis.

Recent Advances in Chemical Biology of Mitochondria Targeting

Mitochondria are vital subcellular organelles that generate most cellular chemical energy, regulate cell metabolism and maintain cell function. Mitochondrial dysfunction is directly linked to numerous diseases including neurodegenerative disorders, diabetes, thyroid squamous disease, cancer and septicemia. Thus, the design of specific mitochondria-targeting molecules and the realization of real-time acquisition of mitochondrial activity are powerful tools in the study and treatment of mitochondria dysfunction in related diseases. Recent advances in mitochondria-targeting agents have led to several important mitochondria chemical probes that offer the opportunity for selective targeting molecules, novel biological applications and therapeutic strategies. This review details the structural and physiological functional characteristics of mitochondria, and comprehensively summarizes and classifies mitochondria-targeting agents. In addition, their pros and cons and their related chemical biological applications are discussed. Finally, the potential biomedical applications of these agents are briefly prospected.

Medicinal applications and molecular targets of dequalinium chloride

For more than 60 years dequalinium chloride (DQ) has been used as anti-infective drug, mainly to treat local infections. It is a standard drug to treat bacterial vaginosis and an active ingredient of sore-throat lozenges. As a lipophilic bis-quaternary ammonium molecule, the drug displays membrane effects and selectively targets mitochondria to deplete DNA and to block energy production in cells. But beyond its mitochondriotropic property, DQ can interfere with the correct functioning of diverse proteins. A dozen of DQ protein targets have been identified and their implication in the antibacterial, antiviral, antifungal, antiparasitic and anticancer properties of the drug is discussed here. The anticancer effects of DQ combine a mitochondrial action, a selective inhibition of kinases (PKC-α/β, Cdc7/Dbf4), and a modulation of Ca²⁺-activated K⁺ channels. At the bacterial level, DQ interacts with different multidrug transporters (QacR, AcrB, EmrE) and with the transcriptional regulator RamR. Other proteins implicated in the antiviral (MPER domain of gp41 HIV-1) and antiparasitic (chitinase A from Vibrio harveyi) activities have been identified. DQ also targets α -synuclein oligomers to restrict protofibrils formation implicated in some neurodegenerative disorders. In addition, DQ is a typical bolaamphiphile molecule, well suited to form liposomes and nanoparticules useful for drug entrapment and delivery (DQAsomes and others). Altogether, the review highlights the many pharmacological properties and therapeutic benefits of this old 'multi-talented' drug, which may be exploited further. Its multiple sites of actions in cells should be kept in mind when using DQ in experimental research.

The potential value of dequalinium chloride in the treatment of cancer: Focus on malignant glioma

Dequalinium chloride has been known as one kind of antibiotic that displays a broad antimicrobial spectrum and has been clinically proven to be very safe. In recent years, studies have shown that dequalinium chloride can inhibit the growth of malignant tumours, and reports were mainly used for solid tumours. Glioblastoma is the most common malignant neuroepithelial tumour of the central nervous system in adults, and the prognosis of glioblastoma is poor as it has a high resistance to apoptosis. This review summarizes the current understanding of dequalinium chloride-induced cancer cell apoptosis and its potential role in glioblastoma resistance and progression. Particularly, we focus on dequalinium chloride as it exerts a wide range of anti-cancer activity through its ability to target and accumulate in the mitochondria, and it effectively inhibits the growth of glioblastoma cells in vitro and vivo. Dequalinium chloride is an inhibitor of XIAP and can also act as a mitochondrial targeting agent, which gives it an interesting perspective regarding recent advances in the treatment of malignant glioma.

Dequalinium chloride inhibits the growth of human glioma cells in vitro and vivo: a study on molecular mechanism and potential targeted agents

BACKGROUND

Our current understanding of the role of dequalinium chloride (DECA) in the progression of glioma remains very limited. This study was aimed to investigate the effect of DECA on human glioma cell lines in vitro and vivo.

METHODS

The underlying molecular mechanism was analyzed for developing potential targeted agents. MTT assay, genomic DNA electrophoresis, DAPI staining, TUNEL staining, and wound scratch assay were performed to evaluate the effect of DECA on human glioma cell lines. Bioinformatics methods were used to screen the possible signaling pathway proteins, and the expression of these proteins and the corresponding mRNA was measured.

RESULTS

DECA significantly inhibited the growth and proliferation of human glioma cells. Screening of apoptosis-related proteins showed the mRNA expression level of 6 genes was significantly changed after DECA administration.

CONCLUSION

This study shows that DECA effectively inhibits the growth of glioma cells in vitro and vivo. DECA may promote glioma cell apoptosis by affecting the expression of NFKB2, HRAS, NF1, CBL, RAF1, and BCL-2 genes.

Novel Inducers of the Expression of Multidrug Efflux Pumps That Trigger Pseudomonas aeruginosa Transient Antibiotic Resistance

The study of the acquisition of antibiotic resistance (AR) has mainly focused on inherited processes, namely, mutations and acquisition of AR genes. However, inducible, noninheritable AR has received less attention, and most information in this field derives from the study of antibiotics as inducers of their associated resistance mechanisms. Less is known about nonantibiotic compounds or situations that can induce AR during infection. Multidrug resistance efflux pumps are a category of AR determinants characterized by the tight regulation of their expression. Their contribution to acquired AR relies in their overexpression. Here, we analyzed potential inducers of the expression of the chromosomally encoded Pseudomonas aeruginosa clinically relevant efflux pumps, MexCD-OprJ and MexAB-OprM. For this purpose, we developed a set of luxCDABE-based P. aeruginosa biosensor strains, which allows the high-throughput analysis of compounds able to modify the expression of these efflux pumps. Using these strains, we analyzed a set of 240 compounds present in Biolog phenotype microarrays. Several inducers of the expression of the genes that encode these efflux pumps were found. The study focused in dequalinium chloride, procaine, and atropine, compounds that can be found in clinical settings. Using real-time PCR, we confirmed that these compounds indeed induce the expression of the mexCD-oprJ operon. In addition, P. aeruginosa presents lower susceptibility to ciprofloxacin (a MexCD-OprJ substrate) when dequalinium chloride, procaine, or atropine are present. This study emphasizes the need to study compounds that can trigger transient AR during antibiotic treatment, a phenotype difficult to discover using classical susceptibility tests.

Antineoplastic Activity and Curative Role of Avenanthramides against the Growth of Ehrlich Solid Tumors in Mice

Interest is growing in finding natural sources of effective antitumor agents that generate fewer side effects than conventional chemotherapeutic drugs. Avenanthramides (Avns) are such compounds; these phenolic molecules naturally occur in oats and have antioxidant, anti-inflammatory, and antiproliferative effects making them worthy of further research. The aim of this study is to characterise Avns' curative ability and antineoplastic activity on solid-form Ehrlich tumors. For the study, 75 female mice were randomly and equally allocated to five groups (group 1-control, group 2-DMSO, group 3-positive control receiving Avns, group 4-mice with Ehrlich solid tumor, and group 5-Ehrlich solid tumor treated with Avns). Mice with Ehrlich solid tumors exhibit increased tumor volume; elevated expression of AFP, ALT, AST, Bcl2, CEA, cholesterol, creatinine, urea, MDA, PCNA, potassium, triglycerides, TNF-α, and NF-κB; and a concomitant decline in catalase, GSH, P53, and SOD. In the mice with Ehrlich tumors who received Avns, there appeared to be improvement in NF-κB TNF-α, tumor markers (AFP and CEA), electrolytes, liver and kidney function enzymes, and lipid profiles; reduced MDA level; improved antioxidant parameters; normalised liver protein, P53, and PCNA; and reduced Bcl2 expression. Pathological examination of tumor lesions also indicated improvement. These results suggest that Avns exhibit antineoplastic activity and possess antioxidant properties that enhance the antioxidant defence system, thus reducing the oxidative stress caused by Ehrlich solid tumors.

Pharmacological modulation of mitochondrial ion channels

The field of mitochondrial ion channels has undergone a rapid development during the last three decades, due to the molecular identification of some of the channels residing in the outer and inner membranes. Relevant information about the function of these channels in physiological and pathological settings was gained thanks to genetic models for a few, mitochondria-specific channels. However, many ion channels have multiple localizations within the cell, hampering a clear-cut determination of their function by pharmacological means. The present review summarizes our current knowledge about the ins and outs of mitochondrial ion channels, with special focus on the channels that have received much attention in recent years, namely, the voltage-dependent anion channels, the permeability transition pore (also called mitochondrial megachannel), the mitochondrial calcium uniporter and some of the inner membrane-located potassium channels. In addition, possible strategies to overcome the difficulties of specifically targeting mitochondrial channels versus their counterparts active in other membranes are discussed, as well as the possibilities of modulating channel function by small peptides that compete for binding with protein interacting partners. Altogether, these promising tools along with large-scale chemical screenings set up to identify new, specific channel modulators will hopefully allow us to pinpoint the actual function of most mitochondrial ion channels in the near future and to pharmacologically affect important pathologies in which they are involved, such as neurodegeneration, ischaemic damage and cancer. LINKED ARTICLES: This article is part of a themed section on Mitochondrial Pharmacology: Featured Mechanisms and Approaches for Therapy Translation. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.22/issuetoc.

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.

Dipeptide-functionalized polyamidoamine dendrimer-mediated apoptin gene delivery facilitates apoptosis of human primary glioma cells

Glioblastoma multiform (GBM) is the most frequent and aggressive form of brain tumors in adults. However, the development of more efficient and safe nonviral vector gene therapy represents a promising therapeutic approach, using a tumor-specific killer gene, named apoptin. In this study, we describe the efficacy of non-viral gene delivery vectors, the amino acid-conjugated PAMAM derivatives (PAMAM-H-R and PAMAM-H-K) in delivering a therapeutic gene, displaying affinity toward human primary glioma cells (GBL-14 cells) and dermal fibroblasts. We analyzed transfection efficiency, using luciferase (Luci) and a pDNA encoding for enhanced fluorescent protein (EGFP), and cytotoxicity in both cells. The results show that transfection efficiency of PAMAM-H-R improved compared to native PAMAM dendrimer, but cytotoxicity of PAMAM-H-R and PAMAM-H-K were very low. We treated both cells with a polyplex formation of PAMAM-H-R or PAMAM-H-K/apoptin, and analyzed their cellular uptake and localization by flow cytometry and confocal microscopy. Furthermore, we analyzed the endosomal escape effect using TEM images, and found that PAMAM-H-R showed very fast escape from endosome to the cytosol. Caspase 3 activity assay, cell cycle distribution, and JC-1 analysis showed apoptosis induced by apoptin in GBL-14 cells. This indicates that PAMAM-H-R can be a potential nonviral vector gene delivery carrier for brain tumor therapy. The present study demonstrates that PAMAM-H-R/apoptin gene polyplex can be used as an effective therapeutic candidate for GBM due to its selective induction of apoptosis in primary glioma cells as a potential nonviral gene delivery carrier for brain tumor therapy.

In vitro and in vivo antitumor effects of the Egyptian scorpion Androctonus amoreuxi venom in an Ehrlich ascites tumor model

Scorpion venom is a highly complex mixture of about 100-700 different components, where peptides are the major constituents with various biological and pharmacological properties including anticancer activities. In this study, anticancer efficacy of the venom of the Egyptian scorpion Androctonus amoreuxi has been evaluated. In vitro, the human breast cancer MCF-7 cell line was treated with the venom and the IC50 was estimated. In vivo studies, Ehrlich ascites carcinoma (EAC) cells were inoculated into CD-1 mice intraperitoneally to form liquid tumor or subcutaneously to form solid tumor and then treated with intraperitoneal injection with venom (0.22 mg/kg) every other day. The total tumor cells in the ascitic fluid and the size of the solid tumor were assessed after 14 and 30 days, respectively. In addition, the mean survival time (MST), body weight, tumor volume, PCV, viability of tumor cells, CBC, AST, ALP, creatinine, oxidative stress biomarkers (GSH, MDA, PCC), tumor marker Ki67, growth factor VEGF and caspase-3 were measured in normal control, EAC control and venom-treated groups (n = 6). Treatment with venom induced anti-tumor effects against liquid and in solid tumors as indicated by a significant (P < 0.05) reduction in tumor volume/size, count of viable EAC cells, expression of Ki67 and VEGF as well as by remarkable increases in MST and caspase-3 expression as compared to non-treated group. Interestingly, the venom restored the altered hematological and biochemical parameters of tumor-bearing animals and significantly increased their life span. These data indicate to (1) the cytotoxic potential effects of A. amoreuxi on tumor cells via anti-proliferative, apoptotic and anti-angiogenic activities; (2) opening a new avenue for further studies on the anti-cancer effects of this agent.

Folate-mediated mitochondrial targeting with doxorubicin-polyrotaxane nanoparticles overcomes multidrug resistance

Resistance to treatment with anticancer drugs is a significant obstacle and a fundamental cause of therapeutic failure in cancer therapy. Functional doxorubicin (DOX) nanoparticles for targeted delivery of the classical cytotoxic anticancer drug DOX to tumor cells, using folate-terminated polyrotaxanes along with dequalinium, have been developed and proven to overcome this resistance due to specific molecular features, including a size of approximately 101 nm, a zeta potential of 3.25 mV and drug-loading content of 18%. Compared with free DOX, DOX hydrochloride, DOX nanoparticles, and targeted DOX nanoparticles, the functional DOX nanoparticles exhibited the strongest anticancer efficacy in vitro and in the drug-resistant MCF-7/ Adr (DOX) xenograft tumor model. More specifically, the nanoparticles significantly increased the intracellular uptake of DOX, selectively accumulating in mitochondria and the endoplasmic reticulum after treatment, with release of cytochrome C as a result. Furthermore, the caspase-9 and caspase-3 cascade was activated by the functional DOX nanoparticles through upregulation of the pro-apoptotic proteins Bax and Bid and suppression of the antiapoptotic protein Bcl-2, thereby enhancing apoptosis by acting on the mitochondrial signaling pathways. In conclusion, functional DOX nanoparticles may provide a strategy for increasing the solubility of DOX and overcoming multidrug-resistant cancers.

Antimicrobial, Antioxidant, Anti-Inflammatory, and Cytotoxic Activities of Propolis from the Stingless Bee Tetragonisca fiebrigi (Jataí)

Propolis from stingless bees Tetragonisca fiebrigi found in Brazil is used in folk medicine by their nutritional and therapeutic properties. However, there are no scientific records evidencing such properties. The present study was designed to investigate the chemical composition and the biological properties of propolis from T. fiebrigi. For this, the chemical composition of the ethanol extract of propolis (EEP) was determined by GC-MS and presented phenolic compounds, alcohol, and terpenes as its major class compounds. The antimicrobial activity was accessed in gram-positive and gram-negative bacteria and in fungi, isolated from different biological fluids and reference strains. The EEP was active against all microorganisms and showed antioxidant activity by scavenging free radicals, inhibiting hemolysis and lipid peroxidation in human erythrocytes incubated with an oxidizing agent. The anti-inflammatory potential of the EEP was confirmed by inhibition of the hyaluronidase enzyme. The cytotoxic activity was concentration-dependent against K562 cells, with a predominance of death by necrosis. Taken together, these results show that propolis from T. fiebrigi has important therapeutic activities, which suggest its potential application in the pharmaceutical industry, as well as in health foods, beverages, and nutritional supplements.

Thiosemicarbazone p-Substituted Acetophenone Derivatives Promote the Loss of Mitochondrial Δψ, GSH Depletion, and Death in K562 Cells

A series of thiosemicarbazone (TSC) p-substituted acetophenone derivatives were synthesized and chemically characterized. The p-substituents appended to the phenyl group of the TSC structures were hydrogen, fluor, chlorine, methyl, and nitro, producing compounds named TSC-H, TSC-F, TSC-Cl, TSC-Me, and TSC-NO₂, respectively. The TSC compounds were evaluated for their capacity to induce mitochondrial permeability, to deplete mitochondrial thiol content, and to promote cell death in the K562 cell lineage using flow cytometry and fluorescence microscopy. TSC-H, TSC-F, and TSC-Cl exhibited a bell-shaped dose-response curve for the induction of apoptosis in K562 cells due to the change from apoptosis to necrosis as the principal mechanism of cell death at the highest tested doses. TSC-Me and TSC-NO₂ exhibited a typical dose-response profile, with a half maximal effective concentration of approximately 10 µM for cell death. Cell death was also evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, which revealed lower toxicity of these compounds for peripheral blood mononuclear cells than for K562 cells. The possible mechanisms leading to cell death are discussed based on the observed effects of the new TSC compounds on the cellular thiol content and on mitochondrial bioenergetics.

Mechanisms of resistance to apoptosis in the human acute promyelocytic leukemia cell line NB4

Current frontline therapies have improved overall survival in acute promyelocytic leukemia (APL) patients to exceptional rates; however, relapse is still a problem among high-risk and old patients. Therefore, the development of better and safer therapies continues to be a goal in the treatment of this disease. In the present work, we examined three different pathways that hinder cell death in the APL cell line NB4, shedding light on the mechanisms that underlie resistance to apoptosis in these cells and that might help provide them with a proliferative advantage. We found that the proteasome inhibitor MG-132 specifically induces in NB4 cells an Nrf2-mediated antioxidant response which counteracts mitochondria-dependent apoptosis induced by the lipophilic cation dequalinium. More importantly, we also demonstrated that high basal autophagy levels and the gain-of-function of mutant p53 are intrinsic mechanisms of resistance to apoptosis in this cell line. According to our results, the pharmacological inhibition of autophagy and p53 mutants are useful tools to explore resistance to apoptosis in APL and other types of cancer and could be the bases of new therapeutic approaches that improve the efficiency and allow dose reduction of the current treatments.

Molecular and cellular characterization of the biological effects of ruthenium(II) complexes incorporating 2-pyridyl-2-pyrimidine-4-carboxylic acid

A great majority of the Ru complexes currently studied in anticancer research exert their antiproliferative activity, at least partially, through ligand exchange. In recent years, however, coordinatively saturated and substitutionally inert polypyridyl Ru(II) compounds have emerged as potential anticancer drug candidates. In this work, we present the synthesis and detailed characterization of two novel inert Ru(II) complexes, namely, [Ru(bipy)(2)(Cpp-NH-Hex-COOH)](2+) (2) and [Ru(dppz)(2)(CppH)](2+) (3) (bipy = 2,2'-bipyridine; CppH = 2-(2'-pyridyl)pyrimidine-4-carboxylic acid; Cpp-NH-Hex-COOH = 6-(2-(pyridin-2-yl)pyrimidine-4-carboxamido)hexanoic acid; dppz = dipyrido[3,2-a:2',3'-c]phenazine). 3 is of particular interest as it was found to have IC(50) values comparable to cisplatin, a benchmark standard in the field, on three cancer cell lines and a better activity on one cisplatin-resistant cell line than cisplatin itself. The mechanism of action of 3 was then investigated in detail and it could be demonstrated that, although 3 binds to calf-thymus DNA by intercalation, the biological effects that it induces did not involve a nuclear DNA related mode of action. On the contrary, confocal microscopy colocalization studies in HeLa cells showed that 3 specifically targeted mitochondria. This was further correlated by ruthenium quantification using High-resolution atomic absorption spectrometry. Furthermore, as determined by two independent assays, 3 induced apoptosis at a relatively late stage of treatment. The generation of reactive oxygen species could be excluded as the cause of the observed cytotoxicity. It was demonstrated that the mitochondrial membrane potential in HeLa was impaired by 3 as early as 2 h after its introduction and even more with increasing time.

Raf/MEK/ERK signaling inhibition enhances the ability of dequalinium to induce apoptosis in the human leukemic cell line K562

Delocalized lipophilic cations, such as dequalinium (DQA), selectively accumulate in mitochondria and display anticancer activity in cells from different malignancies. Previous studies in K562 human leukemic cells indicate that DQA causes cell damage as a consequence of an early disturbance in the mitochondrial function, inducing oxidative stress. These cells turned out to be resistant to apoptosis and died by necrosis when treated with high DQA concentrations (20 μmol/L) for long time periods (48 h). Resistance of K562 cells to DQA-induced apoptosis could be eliminated by inhibition of the kinase activity of the Bcr-Abl protein with imatinib. In this paper, we have studied the effect of DQA on the Raf/MEK/ERK1/2 and PI3K/Akt signal transduction pathways in K562 cells. Our data suggest a DQA downregulatory activity on both ERK1/2 and PI3K protein kinase activity supporting an interaction between both proteins. Moreover, inhibition of ERK1/2 with U0126 enhanced the ability of DQA to potentiate imatinib-induced apoptosis, suggesting a role of the Raf/MEK/ERK pathway and the Bcr-Abl tyrosine kinase in the K562 cell survival. This study contributes to a better understanding of the action mechanism of DQA on K562 cells and encourages the study of DQA in combination with other agents for improving the efficacy of targeted therapies and overcoming resistance to chemotherapeutic agents.

Investigation of Ehrlich ascites tumor cell death mechanisms induced by Synadenium umbellatum Pax

ETHNOPHARMACOLOGICAL RELEVANCE

Synadenium umbellatum Pax. is widely found in South America and empirically used in Brazil for the treatment of several diseases, mainly cancer. The aim of the study was to investigate cell death mechanisms induced by Synadenium umbellatum Pax. using Ehrlich ascites tumor (EAT) cells, as well as the myelotoxicity potential of this plant.

MATERIALS AND METHODS

S. umbellatum cytotoxicity was evaluated in EAT cells by trypan blue exclusion and MTT reduction test and the mechanisms involved in EAT cell death were investigated by light and fluorescence microscopy, flow cytometry and immunocytochemistry. Investigation of S. umbellatum myelotoxicity was performed by clonogenic assay of colony forming unit- granulocyte macrophage (CFU-GM).

RESULTS AND CONCLUSION

Our results demonstrated that S. umbellatum decreased the viability of EAT cells using both methods. Morphological analyses revealed that S. umbellatum-treatment induced EAT cell death by apoptotic pathway. We demonstrated the occurrence of reactive oxygen species (ROS) overgeneration, increased intracellular Ca(2+) concentration, alteration in mitochondrial membrane potential, phosphatydylserine externalization, and activation of caspases 3, 8, and 9. However, S. umbellatum produced myelotoxicity in bone marrow cells in a concentration-dependent manner. In comparison to EAT cells, the effects of S. umbellatum in bone marrow cells were 8-fold lower. Taken together, our results showed that S. umbellatum induced apoptosis in EAT cells at several levels and seems more toxic to tumor cells than to normal bone marrow cells.

Mitochondrial targeting topotecan-loaded liposomes for treating drug-resistant breast cancer and inhibiting invasive metastases of melanoma

Multidrug resistance and cancer metastases are two obstacles to a successful chemotherapy and metastases are closely associated with drug resistance. Mitochondrial targeting topotecan-loaded liposomes have been developed to overcome this resistance and resistance-related metastases. Investigations were performed on breast cancer MCF-7 and resistant MCF-7/adr cells, MCF-7 and resistant MCF-7/adr tumor spheroids, resistant MCF-7/adr cell xenografts in nude mice, and a naturally resistant B16 melanoma metastatic model in nude mice. The mitochondrial targeting topotecan-loaded liposomes were approximately 64 nm in size, and exhibited the strongest inhibitory effects on MCF-7 cells and resistant MCF-7/adr cells. Mitochondrial targeting effects were demonstrated by co-localization in mitochondria, enhanced drug content in mitochondria, dissipated mitochondrial membrane potential, opening of mitochondrial permeability transition pores, release of cytochrome C, and activation of caspase 9 and 3. The targeting liposomes had a stronger inhibitory effect on the resistant tumor spheroids in vitro, enhanced accumulation in resistant MCF-7/adr cell xenografts in mice, as well as being very effective on resistant MCF-7/adr cell xenografts in mice, and having a marked anti-metastastic effect on the naturally resistant B16 melanoma metastatic model in mice. In conclusion, mitochondrial targeting topotecan-loaded liposomes could be a promising strategy for treating resistant cancers and resistance-related metastases.

Quaternary ammonium salts and their antimicrobial potential: targets or nonspecific interactions?

For more than 50 years dequalinium chloride has been used successfully as an antiseptic drug and disinfectant, particularly for clinical purposes. Given the success of dequalinium chloride, several series of mono- and bisquaternary ammonium compounds have been designed and reported to have improved antimicrobial activity. Furthermore, many of them exhibit high activity against mycobacteria and protozoa, especially against plasmodia. This review discusses the structure-activity relationships and the modes of action of the various series of (bis)quaternary ammonium compounds.

Characterization of dequalinium as a XIAP antagonist that targets the BIR2 domain

Inhibitor of apoptosis proteins (IAPs) regulate the activity of caspases in apoptosis. The human X chromosome-encoded IAP (XIAP) is one of the more potent members of the IAP family and it has been described as a central regulator of apoptosis. Thus, molecules that inhibit XIAP could offer therapeutic opportunities to treat unwanted apoptosis inhibition. In the present study we have applied the selective optimization of side activities (SOSA) approach to the discovery of XIAP inhibitors. In this sense, we have identified dequalinium hydrochloride (Dq) as an inhibitor of the XIAP/caspase-3 interaction both in vitro and in cellular assays.

Dequalinium induces human leukemia cell death by affecting the redox balance

Dequalinium, an amphiphilic quinolinium derivative, selectively accumulates in mitochondria and displays anticancer activity in cells from different malignancies. Previous studies indicate a differential DQA-induced cytotoxicity in NB4 and K562 human leukemia cells as a consequence of an early disturbance in mitochondrial function. Results in this paper show that DQA induces a concentration-dependent oxidative stress by decreasing GSH level and increasing ROS in a cell type specific way. Inhibitors of the JNK and p38 stress regulated kinases potentiate DQA-induced NB4 cell death suggesting a protective function for these enzymes. K562 cells with relatively high GSH levels remained resistant to DQA action.

Selective targeting of neuroblastoma tumour-initiating cells by compounds identified in stem cell-based small molecule screens

Neuroblastoma (NB) is the most deadly extra-cranial solid tumour in children necessitating an urgent need for effective and less toxic treatments. One reason for the lack of efficacious treatments may be the inability of existing drugs to target the tumour-initiating or cancer stem cell population responsible for sustaining tumour growth, metastases and relapse. Here, we describe a strategy to identify compounds that selectively target patient-derived cancer stem cell-like tumour-initiating cells (TICs) while sparing normal paediatric stem cells (skin-derived precursors, SKPs) and characterize two therapeutic candidates. DECA-14 and rapamycin were identified as NB TIC-selective agents. Both compounds induced TIC death at nanomolar concentrations in vitro, significantly reduced NB xenograft tumour weight in vivo, and dramatically decreased self-renewal or tumour-initiation capacity in treated tumours. These results demonstrate that differential drug sensitivities between TICs and normal paediatric stem cells can be exploited to identify novel, patient-specific and potentially less toxic therapies.

Cytotoxic effects induced by combination of heliantriol B2 and dequalinium against human leukemic cell lines

Natural occurring compounds are considered an important source of antitumoral agents. In the present study, the cytotoxic potential of three pentacyclic triterpenes isolated from Chuquiraga erinacea (Asteraceae), against the human leukemic cell lines NB4 and K562 was assessed. Heliantriol B2 (HB2) showed the highest cytotoxic activity after 24 h treatment showing IC(50) values of 1.98 ± 0.12 µm and 3.52 ± 0.14 µm for NB4 and K562 cells, respectively. This activity was higher than that of the reference compound dequalinium (DQA). Apoptosis and necrosis induced by HB2 in both NB4 and K562 cell lines were analysed by Annexin V/PI labeling. Mitochondrial alterations including reactive oxygen species (ROS) production and mitochondrial transmembrane potential (ΔΨm) were also tested. The results demonstrated that HB2 induced cell death by apoptosis and necrosis and showed enhanced cytotoxic effects in combination with DQA. Besides, HB2 induced ROS overproduction in NB4 cells and a slight decrease of ΔΨm. Consequently, our findings prompt further studies on the HB2 mechanism of action and its selectivity to tumor cells in order to assess the potential of HB2 as an agent for cancer treatment.

Diethyl (6-amino-9H-purin-9-yl) methylphosphonate induces apoptosis and cell cycle arrest in hepatocellular carcinoma BEL-7402 cells: Role of reactive oxygen species

The primary purpose of this work was to study the mechanism of the anti-proliferation activity of compound diethyl (6-amino-9H-purin-9-yl) methylphosphonate (DaMP), a novel acyclic nucleoside phosphonate. Using cell survival MTT assay, flow cytometry analysis, DNA laddering, DCF fluorescence detection and caspases assays, this study investigated the effects of this compound on cell apoptosis, cell cycle regulation and reactive oxygen species in human hepatocarcinoma BEL-7402 cell lines. Exposure to DaMP at 80 microM for 24 h, BEL-7402 cells displayed a marked retardation of S-phase progression, leading to a severe perturbation of normal cell cycle. In addition, DaMP also significantly inhibited cell proliferation by inducing apoptosis, disrupting DNA synthesis and increasing the activities of caspase-3 and -9, while the antioxidants could significantly inhibit these effects. This study was the first to demonstrate that DaMP could induce apoptosis and cell cycle arrest by producing reactive oxygen species and activating caspase-3 and -9.

Dequalinium induces apoptosis in peripheral blood mononuclear cells isolated from human chronic lymphocytic leukemia

B-cell chronic lymphocytic leukemia (B-CLL) is an abnormal neoplasic proliferation of B cells, which accumulate mainly in the bone marrow and blood preventing both B cells development in the lymph nodes and the ability to fight against infection. The antitumor agents used in chemotherapy are aimed at inducing malignant cell death, thus limiting the growth and spreading of these cells. However, the lack of specificity for tumor cells exhibited by these agents causes undesirable side effects that have led to the investigation of new therapeutic strategies designed to specifically target malignant cells and thus trigger selective cell destruction. Dequalinium (DQA) is an antitumoral agent that selectively accumulates in the mitochondria and has been shown to display anticancer activity in cells from different malignancies. In the present study, the DQA-induced cytotoxicity in B-CLL cells was analyzed by measuring cell viability and cell death, either by necrosis or apoptosis. Our results support the importance of DQA as a selective and potential antileukemic drug with a higher cytotoxic effect on peripheral blood mononuclear cells from B-CLL patients than in those from healthy donors and encourage the performance of further studies in combination with other agents.

A novel diquinolonium displays preclinical anti-cancer activity and induces caspase-independent cell death

Quinolines are a class of chemical compounds with emerging anti-cancer properties. Here, we tested the activity of series of quinolines and quinoline-like molecules for anti-cancer activity and identified a novel diquinoline, 1-methyl-2-[3-(1-methyl-1,2-dihydroquinolin-2-yliden)prop-1-enyl]quinolinium iodide (Q(2)). Q(2 )induced cell death in leukemia, myeloma, and solid tumor cell lines with LD50s in the low to submicromolar range. Moreover, Q(2) induced cell death in primary acute myeloid leukemia (AML) cells preferentially over normal hematopoietic cells. In a mouse model of leukemia, Q(2) delayed tumor growth. Mechanistically, Q(2) induced cell death through caspase independent mechanisms. By electron microscopy, Q(2) increased cytoplasmic vacuolization and mitochondrial swelling. Potentially consistent with the induction of autophagic cell death, Q(2) treatment led to a punctate distribution of LC3 and increased MDC staining. Thus, Q(2) is a novel quinolinium with preclinical activity in malignancies such as leukemia and myeloma and warrants further investigation.

The effect of the lipophilic cation lucigenin on mitochondria depends on the site of its reduction

The role of NAD(P)H-dependent oxidoreductases of the outer mitochondrial membrane (OMM) in the activation of lipophilic cationic dyes is poorly understood. In the present study we compared the rates of production of reactive oxygen species (ROS) and mitochondriotoxic effects of the redox-cycling lipophilic cationic dye lucigenin upon its activation by the respiratory chain and NAD(P)H-dependent oxidoreductases of the OMM. We found that, only in the presence of external NADH and NADPH, which are unable to penetrate the inner membrane, lucigenin stimulated a massive superoxide production and a fast permeabilization of mitochondrial membranes. The permeabilization was biphasic. The first, cyclosporin A-insensitive and Ca(2+)-independent phase was characterized by increased permeability of the inner mitochondrial membrane to solutes with molecular masses of <or=200 Da. The second phase was sensitive to the antagonists of the permeability transition pore (mPTP) and was characterized by permeability similar to that of mPTP (<or=1500 Da). A massive cytochrome c release was observed even at the first phase of permeability when the second phase was inhibited by mPTP antagonists. Whatever the site of lucigenin activation, antioxidants and scavengers of ROS that strongly decrease the ROS level were unable to delay or prevent the permeabilization of membranes, which casts doubt on the involvement of ROS in the regulation of permeability by redox-cycling lipophilic cations. Our results strongly support the idea that the NAD(P)H-dependent reductases of xenobiotics of the OMM can mediate the toxicity of cationic dyes.

Dequalinium induces cell death in human leukemia cells by early mitochondrial alterations which enhance ROS production

Dequalinium (DQA) has been proposed as a selective antitumoral agent due to its preferential accumulation in mitochondria of cancer cells. Our aim was a better understanding of DQA cytotoxicity. DQA-induced NB4 and K562 cell alterations are initiated within the first 30 min of treatment at a high DQA concentration with a mitochondrial membrane depolarization. Cytochrome c release to cytoplasm, superoxide anion overproduction and ATP depletion in NB4 cells induce, 16 h later, apoptosis by a typical caspase-9/caspase-3-dependent intrinsic pathway. K562 cells were more resistant to the DQA effect than NB4 cells, remaining viable for longer time periods.

Plasmodium berghei: In vitro and in vivo activity of dequalinium

Bisquinoline compounds have exhibited remarkable activity in vitro and in vivo against Plasmodium parasites by inhibition of heme detoxification. We have tested the ability of dequalinium 1,1'-(1,10-decanediyl)bis(4-amino-2-methylquinoline), a known antimicrobial agent, to inhibit beta-hematin synthesis using a non-emzymatic colorimetric assay and globin proteolysis by electrophoretic analysis (SDS-PAGE-15%). Dequalinium was able to inhibit both processes in vitro with close correlation to a murine malaria model, reducing parasitemia levels, prolonging the survival time post-infection and curing 40% of infected mice using a combination therapy with a loading dose of chloroquine. These results confirm that dequalinium is a promising lead for antimalarial drug development.

Dicarba-closo-dodecaborane(12) derivatives of phosphonium salts: easy formation of nido-carborane phosphonium zwitterions

The first examples of arylphosphonium salts containing a dicarba-closo-dodecaborane(12) (closo-carborane) are reported; in contrast to the 1,12-carborane derivative, the 1,2- and 1,7-isomers undergo a facile deboronation reaction in polar solvents to afford the corresponding nido-carborane phosphonium zwitterions.