Clotrimazole decreases glycolysis and the viability of lung carcinoma and colon adenocarcinoma cells

Ferrocenyl Azoles: Versatile N-Containing Heterocycles and their Anticancer Activities

The medicinal chemistry of ferrocene has gained its momentum after the discovery of biological activities of ferrocifen and ferroquine. These ferrocenyl drugs have been designed by replacing the aromatic moiety of the organic drugs, tamoxifen and chloroquine respectively, with a ferrocenyl unit. The promising biological activities of these ferrocenyl drugs have paved a path to explore the medicinal applications of several ferrocenyl conjugates. In these conjugates, the ferrocenyl moiety has played a vital role in enhancing or imparting the anticancer activity to the molecule. The ferrocenyl conjugates induce the cytotoxicity by generating reactive oxygen species and thereby damaging the DNA. In medicinal chemistry, the five membered nitrogen heterocycles (azoles) play a significant role due to their rigid ring structure and hydrogen bonding ability with the biomolecules. Several potent drug candidates with azole groups have been in use as chemotherapeutics. Considering the importance of ferrocenyl moiety and azole groups, several ferrocenyl azole conjugates have been synthesized and screened for their biological activities. Hence, in the view of a wide scope in the development of potent drugs based on ferrocenyl azole conjugates, herein we present the details of synthesis and the anticancer activities of ferrocenyl compounds bearing azole groups such as imidazole, triazoles, thiazole and isoxazoles.

Clotrimazole causes membrane depolarization and induces sub G0 cell cycle arrest in Leishmania donovani

Clotrimazole is an FDA approved drug and is widely used as an antifungal agent. An extensive body of research is available about its mechanism of action on various cell types but its mode of killing of Leishmania donovani parasites is unknown. L. donovani causes Visceral Leishmaniasis which is a public health problem with limited treatment options. Its present chemotherapy is expensive, has adverse effects and is plagued with drug resistance issues. In this study we have explored the possibility of repurposing clotrimazole as an antileishmanial drug. We have assessed its efficacy on the parasites and attempted to understand its mode of action. We found that it has a half-maximal inhibitory concentration (IC50) of 35.75 ± 1.06 μM, 12.75 ± 0.35 μM and 73 ± 1.41 μM in promastigotes, intracellular amastigotes and macrophages, respectively. Clotrimazole is 5.73 times more selective for the intracellular amastigotes as compared to the mammalian cell. Effect of clotrimazole was reduced by ergosterol supplementation. It leads to impaired parasite morphology. It alters plasma membrane permeability and disrupts plasma membrane potential. Mitochondrial function is compromised as is evident from increased ROS generation, depolarized mitochondrial membrane and decreased ATP levels. Cell cycle analysis of clotrimazole treated parasites shows arrest at sub-G0 phase suggesting apoptotic mode of cell death.

Selective Anticervical Cancer Injectable and Self-Healable Hydrogel Platforms Constructed of Drug-Loaded Cross-Linkable Unimolecular Micelles in a Single and Combination Therapy

In the face of severe side effects of systemic chemotherapy used in cervical cancer, topical selective drug carriers with long-lasting effects are being sought. Hydrogels are suitable platforms, but their use is problematic in the case of delivery of hydrophobic drugs with anticancer activity. Herein, hydrogels constructed of unimolecular micelles displaying enhanced solubilization of aromatic lipophilic bioactive compounds are presented. Star-shaped poly(benzyl glycidyl ether)-block-poly(glycidyl glycerol ether) with an aryl-enriched core show high encapsulation capacity of poor water-soluble nifuratel and clotrimazole. Nifuratel attained selectivity against cervical cancer cells, whereas clotrimazole preserved its original selectivity. The combination of unimolecular micelles loaded with both drugs provided synergism; however, they were still selective against cervical cancer cells. The cross-linking of drug-loaded unimolecular micelles via dynamic boronic esters provided injectable and self-healable hydrogel drug carriers also displaying synergistic anticancer activity, suitable for intravaginal administration and assuring the effective coverage of the afflicted tissue area and efficient tissue permeability with hydrophobic bioactive compounds. Here, we show that the combination of star-shaped polyether amphiphiles and boronic ester cross-linking chemistry provides a new strategy for obtaining hydrogel platforms suitable for efficient hydrophobic drug delivery.

Repurposing antifungal drugs for cancer therapy

BACKGROUND

Repurposing antifungal drugs in cancer therapy has attracted unprecedented attention in both preclinical and clinical research due to specific advantages, such as safety, high-cost effectiveness and time savings compared with cancer drug discovery. The surprising and encouraging efficacy of antifungal drugs in cancer therapy, mechanistically, is attributed to the overlapping targets or molecular pathways between fungal and cancer pathogenesis. Advancements in omics, informatics and analytical technology have led to the discovery of increasing "off-site" targets from antifungal drugs involved in cancerogenesis, such as smoothened (D477G) inhibition from itraconazole in basal cell carcinoma.

AIM OF REVIEW

This review illustrates several antifungal drugs repurposed for cancer therapy and reveals the underlying mechanism based on their original target and "off-site" target. Furthermore, the challenges and perspectives for the future development and clinical applications of antifungal drugs for cancer therapy are also discussed, providing a refresh understanding of drug repurposing.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This review may provide a basic understanding of repurposed antifungal drugs for clinical cancer management, thereby helping antifungal drugs broaden new indications and promote clinical translation.

Cross-linkable star-hyperbranched unimolecular micelles for the enhancement of the anticancer activity of clotrimazole

Clotrimazole, a hydrophobic drug routinely used in the treatment of vaginal candidiasis, also shows antitumor activity. However, its use in chemotherapy has been unsuccessful to date due to its low solubility in aqueous media. In this work, new unimolecular micelles based on polyether star-hyperbranched carriers of clotrimazole are presented that can enhance solubility, and consequently the bioavailability, of clotrimazole in water. The amphiphilic constructs consisting of a hydrophobic poly(n-alkyl epoxide) core and hydrophilic corona of hyperbranched polyglycidol were synthesized in a three-step anionic ring-opening polymerization of epoxy monomers. The synthesis of such copolymers, however, was only possible by incorporating a linker to facilitate the elongation of the hydrophobic core with glycidol. Unimolecular micelles-clotrimazole formulations displayed significantly increased activity against human cervical cancer HeLa cells compared to the free drug, along with a weak effect on the viability of the normal dermal microvascular endothelium cells HMEC1. This selective activity of clotrimazole on cancer cells with little effect on normal cells was a result of the fact that clotrimazole targets the Warburg effect in cancer cells. Flow cytometric analysis revealed that the encapsulated clotrimazole significantly blocks the progression of the HeLa cycle in the G0/G1 phase and induces apoptosis. In addition, the ability of the synthesized amphiphilic constructs to form a dynamic hydrogel was demonstrated. Such a gel facilitates the delivery of drug-loaded single-molecule micelles to the affected area, where they can form a continuous, self-healing layer.

Studies Regarding the Antimicrobial Behavior of Clotrimazole and Limonene

The paper presents the results of the studies performed to establish the effect of the mixtures between limonene and clotrimazole against microbial pathogens involved in dermatological diseases, such as Candida albicans, Staphyloccocus aureus, and Escherichia coli. Preliminary data obtained from the studies performed in microplates revealed a possible synergism between the mixture of clotrimazole and limonene for Staphylococcus aureus. Studies performed "in silico" with programs such as CLC Drug Discovery Workbench and MOLEGRO Virtual Docker, gave favorable scores for docking each compound on a specific binding site for each microorganism. The tests performed for validation, with the clotrimazole (0.1%) and different sources of limonene (1.9% citrus essential oils), showed a synergistic effect on Staphylococcus aureus in the case of the mixtures between clotrimazole and the essential oils of Citrus reticulata or Citrus paradisi. The studies performed on Staphylococcus aureus MRSA showed a synergistic effect between clotrimazole and the essential oils obtained from Citrus bergamia, Citrus aurantium, or Citrus paradisi. In the case of Pseudomonas aeruginosa, essential oils and clotrimazole used alone did not exhibit antimicrobial activities, but the mixtures between clotrimazole and the essential oils of Citrus bergamia or Citrus sinensis exhibited a synergistic antimicrobial effect.

Detachment of Hexokinase II From Mitochondria Promotes Collateral Sensitivity in Multidrug Resistant Chronic Myeloid Leukemia Cells

Chronic Myeloid Leukemia is a neoplastic disease characterized by the abnormal expansion of hematopoietic cells with compromised functions. Leukemic cells often display a multidrug resistance phenotype, enabling them to evade a number of structurally unrelated cytotoxic compounds. One of those mechanisms relies on the high expression of efflux transporters, such as the ABC proteins, whose activity depends on the hydrolysis of ATP to reduce intracellular drug accumulation. In the present work, we employed a well-known erythroleukemia cell line, K562, and a multidrug resistant derivative cell, FEPS, to evaluate how hexokinase II, a key regulator for the rate-limiting step glycolysis, contributes to the establishment of the multidrug resistance phenotype. We found that multidrug resistant cells primarily resort to glycolysis to generate ATP. Clotrimazole reduced the expression of mitochondrial hexokinase II, which destabilized bioenergetic parameters such as reactive oxygen species production, ATP, and glutathione levels on multidrug resistant cells. This impaired the activity of ABCC1, leading to increased drug accumulation and cell death. In summary, we propose that decoupling of hexokinase II from the mitochondria emerges as a promising strategy to generate collateral sensitivity and aid in the management of chronic myeloid leukemia in chemotherapy-refractory patients.

Feasibility of Photodynamic Therapy for Glioblastoma with the Mitochondria-Targeted Photosensitizer Tetramethylrhodamine Methyl Ester (TMRM)

One of the most challenging problems in the treatment of glioblastoma (GBM) is the highly infiltrative nature of the disease. Infiltrating cells that are non-resectable are left behind after debulking surgeries and become a source of regrowth and recurrence. To prevent tumor recurrence and increase patient survival, it is necessary to cleanse the adjacent tissue from GBM infiltrates. This requires an innovative local approach. One such approach is that of photodynamic therapy (PDT) which uses specific light-sensitizing agents called photosensitizers. Here, we show that tetramethylrhodamine methyl ester (TMRM), which has been used to asses mitochondrial potential, can be used as a photosensitizer to target GBM cells. Primary patient-derived GBM cell lines were used, including those specifically isolated from the infiltrative edge. PDT with TMRM using low-intensity green light induced mitochondrial damage, an irreversible drop in mitochondrial membrane potential and led to GBM cell death. Moreover, delayed photoactivation after TMRM loading selectively killed GBM cells but not cultured rat astrocytes. The efficacy of TMRM-PDT in certain GBM cell lines may be potentiated by adenylate cyclase activator NKH477. Together, these findings identify TMRM as a prototypical mitochondrially targeted photosensitizer with beneficial features which may be suitable for preclinical and clinical translation.

Repurposing of Antimicrobial Agents for Cancer Therapy: What Do We Know?

The substantial costs of clinical trials, the lengthy timelines of new drug discovery and development, along the high attrition rates underscore the need for alternative strategies for finding quickly suitable therapeutics agents. Given that most approved drugs possess more than one target tightly linked to other diseases, it encourages promptly testing these drugs in patients. Over the past decades, this has led to considerable attention for drug repurposing, which relies on identifying new uses for approved or investigational drugs outside the scope of the original medical indication. The known safety of approved drugs minimizes the possibility of failure for adverse toxicology, making them attractive de-risked compounds for new applications with potentially lower overall development costs and shorter development timelines. This latter case is an exciting opportunity, specifically in oncology, due to increased resistance towards the current therapies. Indeed, a large body of evidence shows that a wealth of non-cancer drugs has beneficial effects against cancer. Interestingly, 335 drugs are currently being evaluated in different clinical trials for their potential activities against various cancers (Redo database). This review aims to provide an extensive discussion about the anti-cancer activities exerted by antimicrobial agents and presents information about their mechanism(s) of action and stage of development/evaluation.

Short review of SEC, a potential dexamethasone-sparing regimen for glioblastoma: Spironolactone, ecallantide, clotrimazole

This paper presents a short review of data supporting a dexamethasone sparing regimen, SEC, to reduce glioblastoma related brain edema. The conclusion of the reviewed data is that the rationale and risk/benefit ratio favors a pilot study to determine if the three drug regimen of SEC can reduce need for corticosteroid use during the course of glioblastoma. Details of how selected pathophysiological aspects of brain edema occurring during the course of glioblastoma and its treatment intersect with the established action of the three old drugs of SEC indicate that they can be repurposed to reduce that edema. Current first-line treatment of this edema is dexamethasone or related corticosteroids. There are multiple negative prognostic implications of both the edema itself and of dexamethasone, prime among them shortened survival, making a dexamethasone sparing regimen highly desirable. SEC uses spironolactone, an antihypertensive potassium-sparing diuretic acting by mineralocorticoid receptor inhibition, ecallantide acting to inhibit kallikrein activation marketed to treat hereditary angioedema, and clotrimazole, an old antifungal drug that inhibits intermediate conductance Ca++ activated K+ channel (KCa3.1). These three old drugs are well known to most clinicians, have a well-tolerated safety history, and have a robust preclinical database showing their potential to reduce the specific edema of glioblastoma. Additionally, these three drugs were chosen by virtue of each having preclinical evidence of glioblastoma growth and/or migration inhibition independent of their edema reduction action. A clinical study of SEC is being planned.

The Molecular Mechanism of Metabolic Remodeling in Lung Cancer

Metabolic remodeling is a key phenomenon in the occurrence and development of tumors. It not only offers materials and energy for the survival and proliferation of tumor cells, but also protects tumor cells so that they may survive, proliferate and transfer in the harsh microenvironment. This paper attempts to reveal the role of abnormal metabolism in the development of lung cancer by considering the processes of glycolysis and lipid metabolism, Identification of the molecules that are specifically used in the processes of glycolysis and lipid metabolism, and their underlying molecular mechanisms, is of great clinical and theoretical significance. We will focus on the recent progress in elucidating the molecular mechanism of metabolic remodeling in lung cancer.

Targeting mitochondrial hexokinases increases efficacy of histone deacetylase inhibitors in solid tumor models

Hexokinase 1 and 2 have been shown to inhibit Bak- and Bax-mediated apoptosis, leading us to combine the histone deacetylase inhibitor romidepsin with clotrimazole or bifonazole, two compounds that reportedly decrease mitochondrial localization of hexokinases. Cancer cell lines derived from breast, kidney, lung, colon or ovarian cancers were treated with a short-term exposure to 25 ng/ml romidepsin combined with either clotrimazole or bifonazole. The combination of romidepsin with 25 µM clotrimazole or bifonazole resulted in increased annexin staining compared to cells treated with any of the drugs alone. Cell death was caspase-mediated, as the pan-caspase inhibitor Q-VD-OPh was found to inhibit apoptosis induced by the combination. A549 lung cancer cells or HCT-116 cells deficient in Bak and Bax were also resistant to apoptosis with the combination implicating the intrinsic apoptotic pathway. We found that a 24 h treatment with clotrimazole or bifonazole decreased total hexokinase 2 expression, resulting in a 76% or 60% decrease, respectively, of mitochondrial expression of hexokinase 2. Mitochondrial hexokinase 1 levels increased 2-fold or less. Our work suggests that the combination of a short-term romidepsin treatment with bifonazole or clotrimazole leads to increased apoptosis, most likely due to decreased mitochondrial expression of hexokinase 2.

Clotrimazole inhibits the Wnt/β-catenin pathway by activating two eIF2α kinases: The heme-regulated translational inhibitor and the double-stranded RNA-induced protein kinase

The Wnt/β-catenin signaling pathway controls cell proliferation and differentiation, and therefore, when this pathway is excessively activated, it causes tumorigenesis. Our chemical suppressor screening in zebrafish embryos identified antifungal azoles including clotrimazole, miconazole, and itraconazole, as Wnt/β-catenin signaling inhibitors. Here we show the mechanism underlying the Wnt/β-catenin pathway inhibition by antifungal azoles. Clotrimazole reduced β-catenin revels in a proteasome-independent fashion. By gene knockdown of two translational regulators, heme-regulated translational inhibitor and double-stranded RNA-induced protein kinase, we show that they mediate the clotrimazole-induced inhibition of the Wnt/β-catenin pathway. Thus, clotrimazole inhibits the Wnt/β-catenin pathway by decreasing β-catenin protein levels through translational regulation. Antifungal azoles represent genuine candidate compounds for anticancer drugs or chemopreventive agents that reduce adenomatous polyps.

Nanomicellar Formulation of Clotrimazole Improves Its Antitumor Action toward Human Breast Cancer Cells

Background

Although demonstrated as a selective anticancer drug, the clinical use of clotrimazole (CTZ) is limited due to its low solubility in hydrophilic fluids. Thus, we prepared a water-soluble nanomicellar formulation of CTZ (_nCTZ) and tested on the human breast cancer cell line MCF-7 biology.

Methodology/Principal Findings

CTZ was nanoencapsulated in tween 80 micelles, which generated nanomicelles of, approximately, 17 nm of diameter. MCF-7 cells were treated with _nCTZ and unencapsulated DMSO-solubilized drug (_sCTZ) was used for comparison. After treatment, the cells were evaluated in terms of metabolism, proliferation, survival and structure. We found that _nCTZ was more efficient than _sCTZ at inhibiting glycolytic and other cytosolic and mitochondrial enzymes. Moreover, this increased activity was also observed for lactate production, intracellular ATP content, ROS production and antioxidant potential. As a consequence, _nCTZ-treated MCF-7 cells displayed alterations to the plasma membrane, mitochondria and the nucleus. Finally, _nCTZ induced both apoptosis and necrosis in MCF-7 cells.

Conclusions/Significance

MCF-7 cells are more sensible to _nCTZ than to _sCTZ. This was especially evident on regard to antioxidant potential, which is an important cell defense against drugs that affect cell metabolism. Moreover, this water-soluble formulation of CTZ strengths its potential use as an anticancer medicine.

Phosphatidylinositol-3-kinase as a putative target for anticancer action of clotrimazole

Clotrimazole (CTZ) has been proposed as an antitumoral agent because of its properties that inhibit glycolytic enzymes and detach them from the cytoskeleton. However, the broad effects of the drug, e.g., acting on different enzymes and pathways, indicate that CTZ might also affect several signaling pathways. In this study, we show that CTZ interferes with the human breast cancer cell line MCF-7 after a short incubation period (4 h), thereby diminishing cell viability, promoting apoptosis, depolarizing mitochondria, inhibiting key glycolytic regulatory enzymes, decreasing the intracellular ATP content, and permeating plasma membranes. CTZ treatment also interferes with autophagy. Moreover, when the incubation is performed under hypoxic conditions, certain effects of CTZ are enhanced, such as phosphatidylinositol-3-phosphate kinase (PI3K), which is inhibited upon CTZ treatment; this inhibition is potentiated under hypoxia. CTZ-induced PI3K inhibition is not caused by upstream effects of CTZ because the drug does not affect the interaction of the PI3K regulatory subunit and the insulin receptor substrate (IRS)-1. Additionally, CTZ directly inhibits human purified PI3K in a dose-dependent and reversible manner. Pharmacologic and in silico results suggest that CTZ may bind to the PI3K catalytic site. Therefore, we conclude that PI3K is a novel, putative target for the antitumoral effects of CTZ, interfering with autophagy, apoptosis, cell division and viability.

Clotrimazole as a Cancer Drug: A Short Review

Although clotrimazole was first used against fungal infections, a body of research was later developed indicating that this drug has anticancer properties as well. The mechanism of action is based on the inhibition of mitochondrial-bound glycolytic enzymes and calmodulin, which starves cancer cells of energy. Clotrimazole and its derivatives have been shown to decrease rates of cancer cell proliferation, induce G1 phase arrest, and promote pro-apoptotic factors, which lead to cell death.

Serotonin regulates 6-phosphofructo-1-kinase activity in a PLC-PKC-CaMK II- and Janus kinase-dependent signaling pathway

Serotonin (5-HT) is a hormone that has been implicated in the regulation of many physiological and pathological events. One of the most intriguing properties of this hormone is its ability to up-regulate mitosis. Moreover, 5-HT stimulates glucose uptake and up-regulates PFK activity through the 5-HT(2A) receptor, resulting in the phosphorylation of a tyrosine residue of PFK and the intracellular redistribution of PFK within skeletal muscle. The present study investigated some of the signaling intermediates involved in the effects of 5-HT on 6-phosphofructo-1-kinase (PFK) regulation from skeletal muscle using kinetic assessments, immunoprecipitation, and western blotting assays. Our results demonstrate that 5-HT stimulates PFK from skeletal muscle via phospholipase C (PLC). The activation of PLC in skeletal muscle leads to the recruitment of protein kinase C (PKC) and calmodulin and the stimulation of calmodulin kinase II, which associates with PFK upon 5-HT action. Alternatively, 5-HT loses its ability to up-regulate PFK activity when Janus kinase is inhibited, suggesting that 5-HT is able to control glycolytic flux in the skeletal muscle of mice by recruiting different pathways and controlling PFK activity.

Anticancer agents that counteract tumor glycolysis

Can we consider cancer to be a "metabolic disease"? Tumors are the result of a metabolic selection, forming tissues composed of heterogeneous cells that generally express an overactive metabolism as a common feature. In fact, cancer cells have increased needs for both energy and biosynthetic intermediates to support their growth and invasiveness. However, their high proliferation rate often generates regions that are insufficiently oxygenated. Therefore, their carbohydrate metabolism must rely mostly on a glycolytic process that is uncoupled from oxidative phosphorylation. This metabolic switch, also known as the Warburg effect, constitutes a fundamental adaptation of tumor cells to a relatively hostile environment, and supports the evolution of aggressive and metastatic phenotypes. As a result, tumor glycolysis may constitute an attractive target for cancer therapy. This approach has often raised concerns that antiglycolytic agents may cause serious side effects toward normal cells. The key to selective action against cancer cells can be found in their hyperbolic addiction to glycolysis, which may be exploited to generate new anticancer drugs with minimal toxicity. There is growing evidence to support many glycolytic enzymes and transporters as suitable candidate targets for cancer therapy. Herein we review some of the most relevant antiglycolytic agents that have been investigated thus far for the treatment of cancer.

The effect of clotrimazole on energy substrate uptake and carcinogenesis in intestinal epithelial cells

Clotrimazole has anticarcinogenic activity in several cell types. Our aims were to investigate the anticarcinogenic effect of clotrimazole in a tumoral intestinal epithelial (Caco-2) cell line, to compare it with the effect in a nontumoral intestinal epithelial cell line (IEC-6 cells), and to investigate inhibition of energy substrate uptake as a mechanism contributing to it. The effect of clotrimazole on cell proliferation, viability and differentiation, H-deoxyglucose (H-DG), H-O-methyl-glucose (H-OMG), and C-butyrate uptake, as well as mRNA expression levels of glucose transporters was assessed. In Caco-2 cells, clotrimazole decreased cellular viability and proliferation and increased cell differentiation. The effect on cell proliferation and viability was potentiated by rhodamine123. Clotrimazole also decreased cellular viability and proliferation in IEC-6 cells, but increased the cellular DNA synthesis rate and had no effect on cell differentiation. Exposure of Caco-2 cells to clotrimazole (10 µmol/l) for 1 and 7 days increased (by 20-30%) the uptake of H-DG and H-OMG, respectively, but had no effect on C-butyrate uptake. The effect on H-DG and H-OMG transport was maximal at 10 µmol/l, and the pharmacological characteristics of transport were not changed. However, clotrimazole changed the mRNA expression levels of the facilitative glucose transporter 2 and the Na-dependent glucose cotransporter. Clotrimazole exhibits comparable cytotoxic effects in tumoral and nontumoral intestinal epithelial cell lines. In Caco-2 cells, the cytotoxic effect of clotrimazole was strongly potentiated by the inhibition of oxidative phosphorylation. Moreover, stimulation of glucose uptake might be a compensation mechanism in response to the glycolysis inhibition caused by clotrimazole.

Clotrimazole preferentially inhibits human breast cancer cell proliferation, viability and glycolysis

Background

Clotrimazole is an azole derivative with promising anti-cancer effects. This drug interferes with the activity of glycolytic enzymes altering their cellular distribution and inhibiting their activities. The aim of the present study was to analyze the effects of clotrimazole on the growth pattern of breast cancer cells correlating with their metabolic profiles.

Methodology/Principal Findings

Three cell lines derived from human breast tissue (MCF10A, MCF-7 and MDA-MB-231) that present increasingly aggressive profiles were used. Clotrimazole induces a dose-dependent decrease in glucose uptake in all three cell lines, with K_i values of 114.3±11.7, 77.1±7.8 and 37.8±4.2 µM for MCF10A, MCF-7 and MDA-MB-231, respectively. Furthermore, the drug also decreases intracellular ATP content and inhibits the major glycolytic enzymes, hexokinase, phosphofructokinase-1 and pyruvate kinase, especially in the highly metastatic cell line, MDA-MB-231. In this last cell lineage, clotrimazole attenuates the robust migratory response, an effect that is progressively attenuated in MCF-7 and MCF10A, respectively. Moreover, clotrimazole reduces the viability of breast cancer cells, which is more pronounced on MDA-MB-231.

Conclusions/Significance

Clotrimazole presents deleterious effects on two human breast cancer cell lines metabolism, growth and migration, where the most aggressive cell line is more affected by the drug. Moreover, clotrimazole presents little or no effect on a non-tumor human breast cell line. These results suggest, at least for these three cell lines studied, that the more aggressive the cell is the more effective clotrimazole is.

Muscle-type 6-phosphofructo-1-kinase and aldolase associate conferring catalytic advantages for both enzymes

6-Phosphofructo-1-kinase (PFK) and aldolase are two sequential glycolytic enzymes that associate forming heterotetramers containing a dimer of each enzyme. Although free PFK dimers present a negligible activity, once associated to aldolase these dimers are as active as the fully active tetrameric conformation of the enzyme. Here we show that aldolase-associated PFK dimers are not inhibited by clotrimazole, an antifungal azole derivative proposed as an antineoplastic drug due to its inhibitory effects on PFK. In the presence of aldolase, PFK is not modulated by its allosteric activators, ADP and fructose-2,6-bisphosphate, but is still inhibited by citrate and lactate. The association between the two enzymes also results on the twofold stimulation of aldolase maximal velocity and affinity for its substrate. These results suggest that the association between PFK and aldolase confers catalytic advantage for both enzymes and may contribute to the channeling of the glycolytic metabolism.

Clotrimazole disrupts glycolysis in human breast cancer without affecting non-tumoral tissues

Human breast cancer tissues, as well as normal tissues from the same patients, were treated with clotrimazole (CTZ) and have their capacities for glucose consumption and lactate production evaluated. This treatment strongly decreased the lactate production rate by tumor tissues (85% inhibition) without affecting the other measurements made, i.e. lactate production by control tissues or glucose consumption by both, control and tumor tissues. This result directly correlates with the inhibition promoted by CTZ on the activity of the major regulatory glycolytic enzyme 6-phosphofructo-1-kinase (PFK) that was observed in tumor tissues (84% inhibition) but not in control tissues. Fractionation of the tissues revealed that this inhibition does not occur in the soluble fraction of the enzyme, but is exclusive of a particulate fraction. It has been previously shown that the particulate fraction of PFK activity in tumors is associated to actin filaments (f-actin). Thus, we investigated whether CTZ would affect the association between PFK and f-actin and we found that the drug directly induces the dissociation of the two proteins in the same extent that it inhibits lactate production, total PFK activity and the particulate PFK activity. We concluded that CTZ disrupts glycolysis on human breast tumor tissues, inhibiting PFK activity by dissociating the enzyme from f-actin.

Regulation of mammalian muscle type 6-phosphofructo-1-kinase and its implication for the control of the metabolism

Phosphofructokinase (PFK) is a major regulatory glycolytic enzyme and is considered to be the pacemaker of glycolysis. This enzyme presents a puzzling regulatory mechanism that is modulated by a large variety of metabolites, drugs, and intracellular proteins. To date, the mammalian enzyme structure has not yet been resolved. However, it is known that PFK undergoes an intricate oligomerization process, shifting among monomers, dimers, tetramers, and more complex oligomeric structures. The equilibrium between PFK dimers and tetramers is directly correlated with the enzyme regulation, because the dimer exhibits very low catalytic activity, whereas the tetramer is fully active. Several PFK ligands modulate the enzyme, favoring the formation of its dimers or tetramers. The present review integrates recent findings regarding the regulatory aspects of muscle type PFK and discusses their relation to the control of metabolism.

Clotrimazole induces a late G1 cell cycle arrest and sensitizes glioblastoma cells to radiation in vitro

Tumor cells are characterized by their high rate of glycolysis and clotrimazole has been shown to disrupt the glycolysis pathway thereby arresting the cells in the G1 cell cycle phase. Herein, we present data to support our hypothesis that clotrimazole arrests tumor cells in a radiosensitizing, late G1 phase. The effects of clotrimazole were studied using the glioblastoma cell line, U-87 MG. Flow cytometry was used to analyze cell cycle redistribution and induction of apoptosis. Immunoblots were probed to characterize a late G1 cell cycle arrest. Nuclear and cytoplasmic fractions were collected to follow the clotrimazole-induced translocation of hexokinase II. Clonogenic assays were designed to determine the radiosensitizing effect by clotrimazole. Our studies have shown a dose-dependent and time-dependent clotrimazole arrest in a late G1 cell cycle phase. Concurrent with the late G1 arrest, we observed an overexpression of p27 along with a decreased expression of p21, cyclin-dependent kinase 1, cyclin-dependent kinase 4, and cyclin D. Clotrimazole induced the translocation of mitochondrial-bound hexokinase II to the cytoplasm and the release of cytochrome c into the cytoplasm. Clotrimazole-induced apoptosis was enhanced when combined with radiation. Clotrimazole was shown to sensitize tumor cells to radiation when the cells were irradiated for 18 h post-clotrimazole treatment. The disruption of the glycolysis pathway by clotrimazole leads to cell cycle arrest of U-87 MG cells in the radiosensitizing late G1 phase. The use of clotrimazole as a radiosensitizing agent for cancer treatment is novel and may have broad therapeutic applications.

Clotrimazole potentiates the inhibitory effects of ATP on the key glycolytic enzyme 6-phosphofructo-1-kinase

Clotrimazole (CTZ) has been proposed as a potential anti-neoplastic agent, which inhibits glucose metabolism. The present work aimed to evaluate the effects of CTZ on the kinetic mechanism of 6-phosphofructo-1-kinase (PFK). We show that CTZ promotes a dose-dependent inhibition of PFK, presenting a K(i) of 28 +/- 2 microM. Inhibition occurs through the dissociation of the enzyme tetramers, as demonstrated through fluorescence spectroscopy and gel filtration chromatography. Moreover, the affinities of the enzyme for ATP and fructose-6-phosphate are reduced 50% and 30%, respectively. Furthermore, the affinity of PFK for ATP at the inhibitory site becomes 2-fold higher. Altogether, the results presented here suggest that PFK inhibition by CTZ involves a decrease in the affinity of PFK for its substrates at the catalytic site with the concomitant potentiation of the inhibitory properties of ATP.

Analyses of resected human brain metastases of breast cancer reveal the association between up-regulation of hexokinase 2 and poor prognosis

Brain metastases of breast cancer seem to be increasingin incidence as systemic therapy improves. Metastatic disease in the brain is associated with high morbidity and mortality. We present the first gene expression analysis of laser-captured epithelial cells from resected human brain metastases of breast cancer compared with unlinked primary breast tumors. The tumors were matched for histology, tumor-node-metastasis stage, and hormone receptor status. Most differentially expressed genes were down-regulated in the brain metastases, which included, surprisingly, many genes associated with metastasis. Quantitative real-time PCR analysis confirmed statistically significant differences or strong trends in the expression of six genes: BMP1, PEDF, LAMgamma3, SIAH, STHMN3, and TSPD2. Hexokinase 2 (HK2) was also of interest because of its increased expression in brain metastases. HK2 is important in glucose metabolism and apoptosis. In agreement with our microarray results, HK2 levels (both mRNA and protein) were elevated in a brain metastatic derivative (231-BR) of the human breast carcinoma cell line MDA-MB-231 relative to the parental cell line (231-P) in vitro. Knockdown of HK2 expression in 231-BR cells using short hairpin RNA reduced cell proliferation when cultures were maintained in glucose-limiting conditions. Finally, HK2 expression was analyzed in a cohort of 123 resected brain metastases of breast cancer. High HK2 expression was significantly associated with poor patient survival after craniotomy (P = 0.028). The data suggest that HK2 overexpression is associated with metastasis to the brain in breast cancer and it may be a therapeutic target.

Targeting of cancer energy metabolism

The main purpose of this review is to update and analyze the effect of several antineoplastic drugs (adriamycin, apoptodilin, casiopeinas, cisplatin, clotrimazole, cyclophosphamide, ditercalinium, NSAIDs, tamoxifen, taxol, 6-mercaptopurine, and alpha-tocopheryl succinate) and energy metabolism inhibitors (2-DOG, gossypol, delocalized lipophilic cations, and uncouplers) on tumor development and progression. The possibility that these antineoplastic drugs currently used in in vitro cancer models, in chemo-therapy, or under study in phase I to III clinical trials induce tumor cellular death by altering also metabolite concentration (i.e., ATP), enzyme activities, and/or energy metabolism fluxes is assessed. It is proposed that the use of energy metabolic therapy, as an alternative or complementary strategy, might be a promising novel approach in the treatment of cancer.

Activation of the steroid and xenobiotic receptor, SXR, induces apoptosis in breast cancer cells

BACKGROUND

The steroid and xenobiotic receptor, SXR, is an orphan nuclear receptor that regulates metabolism of diverse dietary, endobiotic, and xenobiotic compounds. SXR is expressed at high levels in the liver and intestine, and at lower levels in breast and other tissues where its function was unknown. Since many breast cancer preventive and therapeutic compounds are SXR activators, we hypothesized that some beneficial effects of these compounds are mediated through SXR.

METHODS

To test this hypothesis, we measured proliferation of breast cancer cells in response to SXR activators and evaluated consequent changes in the expression of genes critical for proliferation and cell-cycle control using quantitative RT-PCR and western blotting. Results were confirmed using siRNA-mediated gene knockdown. Statistical analysis was by t-test or ANOVA and a P value < or = 0.05 was considered to be significant.

RESULTS

Many structurally and functionally distinct SXR activators inhibited the proliferation of MCF-7 and ZR-75-1 breast cancer cells by inducing cell cycle arrest at the G1/S phase followed by apoptosis. Decreased growth in response to SXR activation was associated with stabilization of p53 and up-regulation of cell cycle regulatory and pro-apoptotic genes such as p21, PUMA and BAX. These gene expression changes were preceded by an increase in inducible nitric oxide synthase and nitric oxide in these cells. Inhibition of iNOS blocked the induction of p53. p53 knockdown inhibited up-regulation of p21 and BAX. We infer that NO is required for p53 induction and that p53 is required for up-regulation of cell cycle regulatory and apoptotic genes in this system. SXR activator-induced increases in iNOS levels were inhibited by siRNA-mediated knockdown of SXR, indicating that SXR activation is necessary for subsequent regulation of iNOS expression.

CONCLUSION

We conclude that activation of SXR is anti-proliferative in p53 wild type breast cancer cells and that this effect is mechanistically dependent upon the local production of NO and NO-dependent up-regulation of p53. These findings reveal a novel biological function for SXR and suggest that a subset of SXR activators may function as effective therapeutic and chemo-preventative agents for certain types of breast cancers.

Crude ethanol extract from babassu (Orbignya speciosa): cytotoxicity on tumoral and non-tumoral cell lines

Plant-derived substances have been considered as important sources of drugs, including antineoplasic agents. Babassu mesocarp is popularly used in Brazil as a food additive, and in popular medicine against several conditions, such as inflammations, menstrual pains and leukaemia. From babassu Orbignya speciosa (Mart.) Barb. Rodr. [Arecaceae (Palmae)] epicarp/mesocarp, an ethanol extract was prepared and named OSEME, which was tested on the viability,morphology and metabolism of several cell lines, such as the leukaemic cell lines, HL-60, K562 and the latter multidrug resistant counterpart K562-Lucena 1, the human breast cancer cell line MCF-7, the mouse fibroblast cell line 3T3-L1 and fresh human lymphocytes. OSEME promoted a dose-dependent decrease on the viability of all cells. This effect was much more pronounced on the tumoral cell lines than on non-tumoral cells, a phenomenon revealed by the dose of OSEME which promotes half of maximal effect (ID50). The decrease on viability was followed by shrinkage of cells, alteration on their morphology, and a markedly nuclear condensation. Curiously, stimulation of 6-phosphofructokinase activity (6.6-times) was observed on HL-60 cells, treated with OSEME, when compared to control treated with ethanol (vehicle). These results support evidences to suggest OSEME as a promising source of novel antineoplasic agents.

Clotrimazole, an antifungal drug possessing diverse actions, increases membrane permeation of cadmium in rat thymocytes

In previous study, clotrimazole, an antifungal drug, exerted potent cytotoxic action on rat thymocytes in presence of metal divalent cations such as Cd(2+) and Pb(2+). To reveal one of toxicological characteristics of clotrimazole, we examined the effect of clotrimazole on intracellular concentration of metal divalent cations by flow cytometer with fluo-3, a fluorescent. Simultaneous application of clotrimazole and CdCl(2) significantly decreased the cell viability although their concentrations were not cytotoxic, respectively. Clotrimazole alone increased the intensity of fluo-3 fluorescence, suggesting an increased concentration of intracellular Ca(2+). The intensity of fluo-3 fluorescence augmented by the combination of clotrimazole and CdCl(2) was much higher than that by respective agents. Removal of external Ca(2+) further increased the intensity of fluorescence augmented by the combination. Furthermore, the application of MnCl(2) did not attenuate the intensity in the presence of CdCl(2). Therefore, it is suggested that the augmentation of fluo-3 fluorescence in the simultaneous presence of clotrimazole and CdCl(2) is Cd(2+)-dependent. Clotrimazole may increase membrane permeation of Cd(2+).

Clotrimazole inhibits and modulates heterologous association of the key glycolytic enzyme 6-phosphofructo-1-kinase

Clotrimazole is an antifungal azole derivative recently recognized as a calmodulin antagonist with promising anticancer effects. This property has been correlated with the ability of the drug to decrease the viability of tumor cells by inhibiting their glycolytic flux and consequently decreasing the intracellular concentration of ATP. The effects of clotrimazole on cell glycolysis and ATP production are considered to be due to the detachment of the glycolytic enzymes from the cytoskeleton. Here, we show that clotrimazole directly inhibits the key glycolytic enzyme 6-phosphofructo-1-kinase (PFK). This property is independent of the anti-calmodulin activity of the drug, since it is not mimicked by the classical calmodulin antagonist compound 48/80. However, the clotrimazole-inhibited enzyme can be activated by calmodulin, even though calmodulin has no effect on PFK activity in the absence of the drug. Clotrimazole alone induces the dimerization of PFK reducing the population of tetramers, which is not observed when calmodulin is also present. Since PFK dimers are less active than PFK tetramers, this can explain the inhibitory effect of clotrimazole on the enzyme. Additionally, clotrimazole positively modulates the association of PFK with erythrocyte membranes. Altogether, our data support a hitherto unrecognized action of clotrimazole as a negative modulator of glycolytic flux through direct inhibition of the key enzyme PFK.

Functional KCa3.1 K+ channels are required for human lung mast cell migration

BACKGROUND

Mast cell recruitment and activation are critical for the initiation and progression of inflammation and fibrosis. Mast cells infiltrate specific structures in many diseased tissues such as the airway smooth muscle (ASM) in asthma. This microlocalisation of mast cells is likely to be key to disease pathogenesis. Human lung mast cells (HLMC) express the Ca2+ activated K+ channel K(Ca)3.1 which modulates mediator release, and is proposed to facilitate the retraction of the cell body during migration of several cell types. A study was undertaken to test the hypothesis that blockade of K(Ca)3.1 would attenuate HLMC proliferation and migration.

METHODS

HLMC were isolated and purified from lung material resected for bronchial carcinoma. HLMC proliferation was assessed by cell counts at various time points following drug exposure. HLMC chemotaxis was assayed using standard Transwell chambers (8 microm pore size). Ion currents were measured using the single cell patch clamp technique.

RESULTS

K(Ca)3.1 blockade with triarylmethane-34 (TRAM-34) did not inhibit HLMC proliferation and clotrimazole had cytotoxic effects. In contrast, HLMC migration towards the chemokine CXCL10, the chemoattractant stem cell factor, and the supernatants from tumour necrosis factor alpha stimulated asthmatic ASM was markedly inhibited with both the non-selective K(Ca)3.1 blocker charybdotoxin and the highly specific K(Ca)3.1 blocker TRAM-34 in a dose dependent manner. Although K(Ca)3.1 blockade inhibits HLMC migration, K(Ca)3.1 is not opened by the chemotactic stimulus, suggesting that it must be involved downstream of the initial receptor-ligand interactions.

CONCLUSIONS

Since modulation of K(Ca)3.1 can inhibit HLMC chemotaxis to diverse chemoattractants, the use of K(Ca)3.1 blockers such as TRAM-34 could provide new therapeutic strategies for mast cell mediated diseases such as asthma.

Enhanced anti-tumor activity and alleviated hepatotoxicity of clotrimazole-loaded suppository using poloxamer-propylene glycol gel

To develop a novel clotrimazole-loaded poloxamer-based suppository with enhanced anti-tumor activity and alleviated hepatotoxicity, the melting point of various formulations composed of P 188 and propylene glycol were investigated. The dissolution and anti-tumor activity of clotrimazole delivered by the poloxamer-based suppository was performed. Furthermore, the hepatotoxicity of clotrimazole was carried out after its rectal administration compared to oral administration in mice. The poloxamer mixtures composed of P 188 and propylene glycol were homogeneous phases. P 188 greatly affected the melting point of poloxamer mixtures. In particular, the poloxamer mixture [P 188/propylene glycol (70%/30%)] with the melting point of about 32 degrees C was a solid form at room temperature and instantly melted at physiological temperature. The ratio of P 188/propylene glycol greatly affected the dissolution rates of clotrimazole from poloxamer-based suppository. Dissolution mechanism analysis showed the dissolution rate of clotrimazole from poloxamer-based suppositories was independent of the time. The clotrimazole-loaded suppository with P 188 and propylene glycol could not irritate or damage the rectal tissues of rats and gave the improved anti-tumor activity in a dose-dependent manner at mouse. Furthermore, its rectal administration decreased the hepatotoxicity compared to oral administration. Thus, the poloxamer-based solid suppository system with clotrimazole/P 188/propylene glycol was an effective rectal dosage form for the treatment of tumors with alleviated adverse effects.

Modulation of 6-phosphofructo-1-kinase oligomeric equilibrium by calmodulin: formation of active dimers

Muscle 6-phospho-1-kinase (PFK) is the key regulatory enzyme of the glycolytic pathway and is a calmodulin-binding protein binding two calmodulin molecules per PFK protomer. This enzyme is characterized by a complex regulation that involves its allosteric behavior modulated by several ligands, which modulate the equilibrium between the active tetramers and the inactive dimers of the enzyme. Calmodulin is described to induce the dimerization of PFK, so inhibiting its catalytic activity. Here, we show that binding of calmodulin specifically to its higher-affinity site of PFK induce its dimerization without compromising enzyme catalytic activity forming a hitherto not described active dimmer of PFK. It is also shown that the dimerization is a Ca2+ -dependent event that responds to physiological intracellular Ca2+ concentrations and decrease the interaction of the enzyme to membrane site, which stimulate its catalytic activity. We propose that the effects of calmodulin on PFK reported here are of great physiological significance due to the response to physiological concentrations of Ca2+ and due to be in accordance to the known effects of calmodulin on cell ATP production. We also propose that calmodulin might affect the interaction of PFK to other cellular components as the cytoskeleton.

Clotrimazole Inhibits Hemoperoxidase of Plasmodium falciparum and Induces Oxidative Stress

The mechanism of antimalarial activity of clotrimazole was studied placing emphasis on its role in inhibiting hemoperoxidase for inducing oxidative stress in Plasmodium falciparum. Clotrimazole, in the presence of H2O2, causes irreversible inactivation of the enzyme, and the inactivation follows pseudo-first order kinetics, consistent with a mechanism-based (suicide) mode. The pseudo-first order kinetic constants are ki = 2.85 microM, k(inact) = 0.9 min(-1), and t(1/2) = 0.77 min. The one-electron oxidation product of clotrimazole has been identified by EPR spectroscopy as the 5,5'-dimethyl-1-pyrroline N-oxide (DMPO) adduct of the nitrogen-centered radical (aN = 15 G), and as DMPO protects against inactivation, this radical is involved in the inactivation process. Binding studies indicate that the clotrimazole oxidation product interacts at the heme moiety, and the heme-clotrimazole adduct has been dissociated from the inactivated enzyme and identified (m/z 1363) by mass analysis. We found that the inhibition of hemoperoxidase increases the accumulation of H2O2 in P. falciparum and causes oxidative stress. Furthermore, the inhibition of hemoperoxidase correlates well with the inhibition of parasite growth. The results described herein indicate that the antimalarial activity of clotrimazole might be due to the inhibition of hemoperoxidase and subsequent development of oxidative stress in P. falciparum.

Compartmentalization of transport and phosphorylation of glucose in a hepatoma cell line

The first steps of glucose metabolism are carried out by members of the families of GLUTs (glucose transporters) and HKs (hexokinases). Previous experiments using the inhibitor of glucose transport, CB (cytochalasin B), revealed that compartmentalization of GLUTs and HKs is a major factor in the control of glucose uptake in L6 myotubes [Whitesell, Ardehali, Printz, Beechem, Knobel, Piston, Granner, Van Der Meer, Perriott and May (2003) Biochem. J. 370, 47-56]. In the present paper, we evaluate compartmentalization of GLUTs and HKs in a hepatoma cell line, H4IIE, which is characterized by excess GLUT activity, HKI in a particulate and a cytosolic fraction, and insignificant G6Pase (glucose-6-phosphatase) activity. The measured activity of glucose transport exceeded the rate of phosphorylation approx. 30-fold. Treatment with 25 microM CB (K(i) approximately 3 microM in H4IIE cells) paradoxically increased the excess of GLUTs over phosphorylation (GLUTs are inhibited 80%, while phosphorylation is inhibited 98%). The global relationships of the data could be reconciled most simply by a two-compartment model. In this model, phosphorylation of glucose is carried out by a subset of HK molecules supplied by a subset of GLUTs that are more sensitive to CB than the other GLUTs. The agent, DCC (dicyclohexylcarbodi-imide) caused HKI to translocate from the particulate compartment to the cytosolic compartment and potently inhibited glucose phosphorylation. The particulate compartment may represent the mitochondria, to which the more CB-sensitive GLUTs may control the transport of glucose.

Clotrimazole decreases human breast cancer cells viability through alterations in cytoskeleton-associated glycolytic enzymes

Cancer cells are characterized by a high rate of glycolysis, which is their primary energy source. Glycolysis is known to be controlled by allosteric regulators, as well as by reversible binding of glycolytic enzymes to cytoskeleton. Clotrimazole is an anti-fungal azole derivative recently recognized as a calmodulin antagonist with promising anti-cancer effect. Here, we show that clotrimazole induced morphological and functional alterations on human breast cancer derived cell line, MCF-7. The drug decreased cell viability in a dose- and time-dependent manner, exhibiting an IC50 of 88.6+/-5.3 microM and a t0.5 of 89.7+/-7.2 min, with 50 microM clotrimazole. Morphological changes were evident as observed by scanning electron microscopy, which revealed the completely loss of protrusion responsible for cell adhesion after a 180 min of treatment with 50 microM clotrimazole. Giemsa stained cells observed by optical microscopy show morphological alterations and a marked nuclear condensation. These changes occurred in parallel to the detachment of the glycolytic enzymes, 6-phosphofructo-1-kinase and aldolase, from cytoskeleton. After a 45 min treatment with 50 microM clotrimazole, the remaining activities in a cytoskeleton enriched fraction was 16.4+/-3.6% and 41.0+/-15.6% of control for 6-phosphofructo-1-kinase and aldolase, respectively. Immunocytochemistry experiments revealed a decrease in the co-localization of 6-phosphofructo-1-kinase and F-actin after clotrimazole treatment, suggesting the site of detachment of the enzymes. Altogether, our results support evidence for apoptotic events that might be started by clotrimazole involving inhibition of glycolytic flux in MCF-7 cells and makes this drug a promising agent in the fight against human breast cancer.

Tumor apoptosis induced by ruthenium(II)-ketoconazole is enhanced in nonsusceptible carcinoma by monoclonal antibody to EGF receptor

Ketoconazole (KTZ) has been used as a second-line agent in hormone-refractory cancer therapy. Since transition metal complexes including those of Ru(III), show important anticancer activity with limited toxicity, we investigated the potential antitumor efficacy of Ru(II) complexed to KTZ or clotrimazole (CTZ) compared to Ru(II) alone or uncomplexed azoles. RuCl2(KTZ)2 exerted greater apoptosis- associated caspase-3 activation than RuCl2(CTZ)2, KTZ, CTZ or RuCl2(MeCN)4 against several human tumor cell monolayers. PARP cleavage and a decrease in S+G2 cells were evident after RuCl2(KTZ)2 treatment in genetically matched C8161 melanoma monolayers with unequal p53 functional status. Release of mitochondrial cytochrome c and Mn-SOD suggest mitochondria as a target of RuCl2(KTZ)2. Treatment of WM164 melanoma monolayers with 25 microM of cisplatin or RuCl2(KTZ)2 showed that the latter is more effective than cisplatin at inducing PARP fragmentation and proapoptotic Bak expression. Such results suggest that these Ru(II) and Pt(II) metal complexes are unequally effective and act through alternative signaling pathways. In studies with multicellular spheroids, which frequently are more resistant to cytotoxic anticancer drugs than monolayers, those from wt p53 C8161 melanoma underwent PARP fragmentation in response to RuCl2(KTZ)2. In contrast, spheroids of mut p53 A431 carcinoma overexpressing EGF receptor were resistant to either RuCl2(KTZ)2 or anti-EGF receptor C225 MAb. However, joint treatment with both agents restored growth arrest and apoptosis in these spheroids. In contrast to the antitumor action of cisplatin, which is known to be hampered by p53 dysfunction, we show that RuCl2(KTZ)2 is active irrespective of p53 functional status against several adherent tumor cells and synergizes with anti-EGF receptor C225 MAb to kill tumor spheroids resistant to either agent.