Calmodulin antagonists decrease glucose 1,6-bisphosphate, fructose 1,6-bisphosphate, ATP and viability of melanoma cells

Treatment of cancer with antipsychotic medications: Pushing the boundaries of schizophrenia and cancer

Over a century ago, the phenothiazine dye, methylene blue, was discovered to have both antipsychotic and anti-cancer effects. In the 20th-century, the first phenothiazine antipsychotic, chlorpromazine, was found to inhibit cancer. During the years of elucidating the pharmacology of the phenothiazines, reserpine, an antipsychotic with a long historical background, was likewise discovered to have anti-cancer properties. Research on the effects of antipsychotics on cancer continued slowly until the 21st century when efforts to repurpose antipsychotics for cancer treatment accelerated. This review examines the history of these developments, and identifies which antipsychotics might treat cancer, and which cancers might be treated by antipsychotics. The review also describes the molecular mechanisms through which antipsychotics may inhibit cancer. Although the overlap of molecular pathways between schizophrenia and cancer have been known or suspected for many years, no comprehensive review of the subject has appeared in the psychiatric literature to assess the significance of these similarities. This review fills that gap and discusses what, if any, significance the similarities have regarding the etiology of schizophrenia.

Anti-Proliferative and Anti-Migration Activity of Arene–Ruthenium(II) Complexes with Azole Therapeutic Agents

The efficacy of organoruthenium complexes containing ergosterol biosynthesis inhibitors (CTZ: clotrimazole, KTZ: ketoconazole and FCZ: fluconazole) against tumor cells, and their interaction with important macro-biomolecules such as human serum albumin and DNA have been investigated here. Our experimental results indicated that these ruthenium(II) complexes present spontaneous electrostatic interactions with albumin, and act as minor groove binders with the DNA. The ability of these Ru(II)–azole complexes to inhibit the proliferation of selected human tumor and non-tumor cell lines was determined by MTT assay. Complexes [RuCl(CTZ)(η6-p-cymene)(PPh3)]PF6 (3) and [RuCl(KTZ)(η6-p-cymene)(PPh3)]PF6 (4) were shown to be between 3- and 40-fold more cytotoxic than the free ligands and the positive control cisplatin. Complex 3 was selected to continue studies on the triple negative breast tumor cell line MDA-MB-231, inducing morphological changes, loss of adhesion, inhibition of colony formation, and migration through Boyden chambers, cell cycle arrest in the sub-G1 phase, and a mechanism of cell death by apoptosis. All these interesting results show the potential of this class of organometallic Ru(II) complexes as an antiproliferative agent.

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.

Thioridazine induces apoptosis by targeting the PI3K/Akt/mTOR pathway in cervical and endometrial cancer cells

Recently, thioridazine (10-[2-(1-methyl-2-piperidyl) ethyl]-2-methylthiophenothiazine), a well-known anti-psychotic agent was found to have anti-cancer activity in cancer cells. However, the molecular mechanism of the agent in cellular signal pathways has not been well defined. Thioridazine significantly increased early- and late-stage apoptotic fraction in cervical and endometrial cancer cells, suggesting that suppression of cell growth by thioridazine was due to the induction of apoptosis. Cell cycle analysis indicated thioridazine induced the down-regulation of cyclin D1, cyclin A and CDK4, and the induction of p21 and p27, a cyclin-dependent kinase inhibitor. Additionally, we compared the influence of thioridazine with cisplatin used as a control, and similar patterns between the two drugs were observed in cervical and endometrial cancer cell lines. Furthermore, as expected, thioridazine successfully inhibited phosphorylation of Akt, phosphorylation of 4E-BP1 and phosphorylation of p70S6K, which is one of the best characterized targets of the mTOR complex cascade. These results suggest that thioridazine effectively suppresses tumor growth activity by targeting the PI3K/Akt/mTOR/p70S6K signaling pathway.

Anti-angiogenic effects of thioridazine involving the FAK-mTOR pathway

Thioridazine is a type of anti-psychotic drug that also includes anti-tumor activity. In this study, we assessed the effects of thioridazine, as a novel anti-angiogenic agent, on the suppression of angiogenesis-mediated cell proliferation. Thioridazine was found to inhibit growth in ovarian cancer cells (OVCAR-3 and 2774), but did not possess any inhibitory effects on normal cell types such as HOSE-E6E7, MCF-10A, MRC-5, and BEAS-2B. Thioridazine also suppressed vascular endothelial growth factor (VEGF)-stimulated HUVEC migration in a dose-time-dependent manner. We also showed that being treated with thioridazine inhibited VEGF-stimulated proliferation, invasion, and capillary-like structure tube formation in vitro. Thioridazine suppressed phosphorylation of the signaling regulators downstream of the focal adhesion kinase (FAK) through αvβ3 integrin, which also include Akt, phosphoinositide-dependent protein kinase 1 (PDK-1), mammalian target of rapamycin (mTOR), ribosomal protein S6 kinase (p70S6K), but had no effect on VEGF-stimulated extracellular signal-regulated kinase (ERK) phosphorylation. We found the molecular mechanism of thioridazine to be a novel anti-angiogenic protein. These results provide evidence for the regulation of endothelial cell functions that are relevant to angiogenesis through the suppression of the αvβ3/FAK/mTOR signaling pathway.

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.

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.

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.

A gene signature-based approach identifies thioridazine as an inhibitor of phosphatidylinositol-3'-kinase (PI3K)/AKT pathway in ovarian cancer cells

OBJECTIVE

Thioridazine, a derivative of phenothiazine, has been reported to have antiproliferative activity on tumor cells. However, the mechanism has not been well defined.

METHODS

Using in-silico gene signature based approach, we have demonstrated that thioridazine could inhibit phosphatidylinositol-3'-kinase (PI3K)/Akt pathway, and thus exert cytotoxicity in ovarian cancer cells.

RESULTS

The Connectivity Map indicated that thioridazine induces gene signature similar to that of Akt inhibition. Moreover, preexisting inhibitors of PI3K/Akt pathway were also found to reveal similar signature. In SKOV-3 cells, immunoblot using p85 antibody showed that thioridazine could inhibit PI3K signal. In addition, thioridazine was found to inhibit p-Akt (Ser 473) in a dose-dependent manner. Furthermore, thioridazine was found to decrease cell viability and induce apoptosis. Exposure to thioridazine induced G(0)/G(1) arrest and down-regulated the cell cycle regulator, Cyclin D1 and CDK4, and up-regulated p21, p16, and p-CDC25A. Finally, additive cytotoxicity was observed when cisplatin and thioridazine were treated simultaneously.

CONCLUSIONS

The current study indicated that in-silico approach, such as Connectivity Map, is a potentially useful method to identify the unknown cellular function among the drugs already in use in clinic. Owing to the property of Akt inhibition and additive cytotoxicity observed with the platinum compound, further research should be focused on this drug.

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.

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.

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.

Inhibition of tumor growth and prolonged survival of rats with intracranial gliomas following administration of clotrimazole

OBJECT

Clotrimazole, an imidazole derivative and inhibitor of cytochrome P-450, inhibits the proliferation of cancer cells by downregulating the movement of intracellular Ca++ and K+ and by interfering with the translation initiation process. Clotrimazole inhibits the proliferation of human glioblastoma multiforme cells; it induces morphological changes toward differentiation and blocks the cell cycle in the G1/G1 phase. In vitro, clotrimazole enhances the antitumor effect of cisplatin by inducing wild-type p53-mediated apoptosis. The authors examined the effect of clotrimazole on tumor growth, sensitivity to cisplatin, and survival of rats with intracranial gliomas.

METHODS

Cultured C6 and 9L glioma cells were exposed to clotrimazole, and cell growth was assessed using the 3-(4,5-dimethylthiazol-2-yl)2,5-diphenyl tetrazolium bromide colorimetric assay. Clotrimazole produced a dose- and time-dependent inhibition of cell proliferation. The growth inhibitory effect of clotrimazole could not be overcome by exogenous stimulation with epidermal growth factor. Both C6 and 9L glioma cells were implanted into the rat brain and after 5 days, the animals were treated with a daily single dose of clotrimazole for 8 consecutive days. Clotrimazole treatment caused a significant inhibition of intracranial tumor growth. The survival of rats with 9L gliomas was analyzed after 10 days of treatment with clotrimazole, cisplatin, or a combination of clotrimazole and cisplatin. Rats treated with either drug displayed a significantly prolonged survival time; however, the combination treatment resulted only in an additional survival benefit.

CONCLUSIONS

Clotrimazole effectively inhibits cell proliferation and tumor growth, and prolongs survival of rats with intracranial gliomas. Clotrimazole may be considered a potential anticancer drug for treatment of intracranial gliomas.

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

Glycolysis is known to be the primary energy source in most cancer cells. We investigated here the effect of clotrimazole (1-(alpha-2-chlorotrityl)imidazole), the antifungal azole derivative, which was recently recognized as calmodulin antagonist, on the levels of glucose 1,6-bisphosphate and fructose 1,6-bisphosphate, the two stimulatory signal molecules of glycolysis, and on ATP content and cell viability in LL/2 Lewis lung carcinoma cells and CT-26 colon adenocarcinoma cells. We found that clotrimazole induced a significant, dose- and time-dependent reduction in the levels of glucose 1,6-bisphosphate, fructose 1,6-bisphosphate, ATP, and cell viability. These findings suggest that clotrimazole causes a reduction in glycolysis and ATP levels, which eventually leads to cell destruction after 3 h of treatment. Since cell proliferation was also reported to be inhibited by calmodulin antagonists, this substance is most promising agent in treatment of cancer by inhibiting both cell proliferation and the glycolytic supply of ATP required for cancer cell growth.

The recent impact of solid-phase synthesis on medicinally relevant benzoannelated nitrogen heterocycles

Benzoannelated heterocycles such as benzodiazepines and indoles can be prepared efficiently through cyclization on solid supports, although no single approach is currently universal for the preparation of all benzoannelated N-heterocycle chemistries. In this review, a number of synthetic strategies for the generation of benzoannelated nitrogen heterocycles using resin-bound substrates have been described. Classical heterocycle forming reactions such as the Fischer indole, the Bischler-Napieralski tetrahydroisoquinoline, the Pictet-Spengler tetrahydro-beta-carboline, the Tsuge, the Nenitzescu and the Richter cinnoline reaction are presented. In addition, the Heck, Sonogashira, Wittig, Diels-Alder, and olefin metathesis reactions have been also used. Multicomponent reactions such as the Grieco three-component assembly have been exploited for the synthesis of heterocycles. Cyclative cleavage from the solid support is particularly suitable for the synthesis of heterocycles while particular emphasis has been focused on the synthesis of libraries and the use of combinatorial chemistry techniques. In addition, the most relevant pharmacological properties of benzoannelated nitrogen heterocycles are included.

Detachment of glycolytic enzymes from cytoskeleton of Lewis lung carcinoma and colon adenocarcinoma cells induced by clotrimazole and its correlation to cell viability and morphology

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. We report here that clotrimazole (l-(alpha-2-chlorotrityl)imidazole), the antifungal azole derivative, which was recently recognized as calmodulin antagonist, induced a dose-dependent detachment of the glycolytic enzymes, phosphofructokinase (ATP: D-fructose-6-phosphate 1-phosphotransferase, EC 2.7.1.11) and aldolase (D-fructose-l,6-bisphosphate D-glyceraldehyde-3-phosphate-lyase, EC 4.1.2.13), from cytoskeleton of LL/2 Lewis lung carcinoma cells and CT-26 colon adenocarcinoma cells. The detachment of glycolytic enzymes from cytoskeleton would reduce the provision of local ATP, in the vicinity of the cytoskeleton membrane, and would also affect cytoskeleton structure and cell shape. We show here that clotrimazole decreased the viability of LL/2 Lewis lung carcinoma cells and CT-26 colon adenocarcinoma cells. After 3h of incubation with clotrimazole, complete cell destruction was detected. Ultrastructural cell damage was manifested by disintegration of the outer membrane by scanning electron microscopy (SEM). The detachment of glycolytic enzymes from cytoskeleton, induced by clotrimazole, preceded the decrease in cell viability, which indicates that this is an early effect and not a result of cell death. Since the cytoskeleton is being recognized as an important modulator of cell function, proliferation, differentiation, and neoplasia, detachment of the glycolytic enzymes from cytoskeleton induced by clotrimazole, as well as its reported inhibitory action on cell proliferation, makes this drug the most promising agent in the treatment of cancer.

Effects of the human papilloma virus HPV-16 E7 oncoprotein on glycolysis and glutaminolysis: role of pyruvate kinase type M2 and the glycolytic-enzyme complex

Proliferating and tumour cells express the glycolytic isoenzyme, pyruvate kinase type M2 (M2-PK), which occurs in a highly active tetrameric form and in a dimeric form with low affinity for phosphoenolpyruvate. The switch between the two forms regulates glycolytic phosphometabolite pools and the interaction between glycolysis and glutaminolysis. In the present study, we show the effects of oncoprotein E7 of the human papilloma virus (HPV)-16 (E7)-transformation on two NIH 3T3 cell strains with different metabolic characteristics. E7-transformation of the high glycolytic NIH 3T3 cell strain led to a shift of M2-PK to the dimeric form and, in consequence, to a decrease in the cellular pyruvate kinase mass-action ratio, the glycolytic flux rate and the (ATP+GTP)/(UTP+CTP) ratio, as well as to an increase in fructose 1,6-bisphosphate (FBP) levels, glutamine consumption and cell proliferation. The low glycolytic NIH 3T3 cell strain is characterized by high pyruvate and glutamine consumption rates and by an intrinsically large amount of the dimeric form of M2-PK, which is correlated with high FBP levels, a low (ATP+GTP)/(CTP+UTP) ratio and a high proliferation rate. E7-transformation of this cell strain led to an alteration in the glycolytic-enzyme complex that correlates with an increase in pyruvate and glutamine consumption and a slight increase in the flow of glucose to lactate. The association of phosphoglyceromutase within the glycolytic-enzyme complex led to an increase of glucose and serine consumption and a disruption of the linkage between glucose consumption and glutaminolysis. In both NIH 3T3 cell lines, transformation increased glutaminolysis and the positive correlation between alanine and lactate production.

Effects of the human papilloma virus HPV-16 E7 oncoprotein on glycolysis and glutaminolysis: role of pyruvate kinase type M2 and the glycolytic-enzyme complex

Proliferating and tumour cells express the glycolytic isoenzyme, pyruvate kinase type M2 (M2-PK), which occurs in a highly active tetrameric form and in a dimeric form with low affinity for phosphoenolpyruvate. The switch between the two forms regulates glycolytic phosphometabolite pools and the interaction between glycolysis and glutaminolysis. In the present study, we show the effects of oncoprotein E7 of the human papilloma virus (HPV)-16 (E7)-transformation on two NIH 3T3 cell strains with different metabolic characteristics. E7-transformation of the high glycolytic NIH 3T3 cell strain led to a shift of M2-PK to the dimeric form and, in consequence, to a decrease in the cellular pyruvate kinase mass-action ratio, the glycolytic flux rate and the (ATP+GTP)/(UTP+CTP) ratio, as well as to an increase in fructose 1,6-bisphosphate (FBP) levels, glutamine consumption and cell proliferation. The low glycolytic NIH 3T3 cell strain is characterized by high pyruvate and glutamine consumption rates and by an intrinsically large amount of the dimeric form of M2-PK, which is correlated with high FBP levels, a low (ATP+GTP)/(CTP+UTP) ratio and a high proliferation rate. E7-transformation of this cell strain led to an alteration in the glycolytic-enzyme complex that correlates with an increase in pyruvate and glutamine consumption and a slight increase in the flow of glucose to lactate. The association of phosphoglyceromutase within the glycolytic-enzyme complex led to an increase of glucose and serine consumption and a disruption of the linkage between glucose consumption and glutaminolysis. In both NIH 3T3 cell lines, transformation increased glutaminolysis and the positive correlation between alanine and lactate production.

Detachment of the glycolytic enzymes, phosphofructokinase and aldolase, from cytoskeleton of melanoma cells, induced by local anesthetics

Cancer cells are characterized by a high rate of glycolysis, which is their primary energy source. An important mechanism that controls glycolysis is the reversible binding of glycolytic enzymes to cytoskeleton. We report here that the local anesthetics, lidocaine and bupivacaine, induced a dose-dependent detachment of the glycolytic enzymes, phosphofructokinase (EC 2.7.1.11) and aldolase (EC 4.1.2.13), from cytoskeleton of B16 melanoma cells. The detachment of glycolytic enzymes from cytoskeleton would reduce the provision of local ATP, in the vicinity of cytoskeleton-membrane and would also affect cytoskeleton structure. We show here that the local anesthetics decreased the viability of melanoma cells. The detachment of the glycolytic enzymes from cytoskeleton, induced by the drugs, preceded melanoma cell death, which indicates that this is an early effect and not a result of cell death. Bupivacaine was more potent than lidocaine both on the glycolytic enzymes and on cell viability. The present results suggest that local anesthetics, and especially bupivacaine, are promising drugs for the treatment of melanoma.

Local anesthetics induce a decrease in the levels of glucose 1, 6-bisphosphate, fructose 1,6-bisphosphate, and ATP, and in the viability of melanoma cells

Glycolysis is known to be the primary energy source in cancer cells. We investigated here the effect of local anesthetics, lidocaine and bupivacaine, on the levels of glucose 1,6-bisphosphate and fructose 1,6-bisphosphate, the two stimulatory signal molecules of glycolysis, and on ATP levels and cell viability in B16 melanoma cells. We found that both drugs induced a significant, dose-dependent reduction in the levels of glucose 1,6-bisphosphate, fructose 1, 6-bisphosphate, ATP, and cell viability. Bupivacaine was more potent than lidocaine. The decrease in glucose 1,6-bisphosphate and fructose 1,6-bisphosphate, induced by the local anesthetics, preceded the reduction in the viability of melanoma cells, indicating that these are early changes and not a result of cell death. Cell viability was reduced in a close correlation with the fall in ATP. These findings suggest that the fall in the levels of the two signal allosteric regulators of glycolysis, induced by the local anesthetics, is one of the mechanisms that causes a reduction in glycolysis and ATP levels, which eventually leads to melanoma cell death. These experiments suggest that local anesthetics, and especially bupivacaine, are most promising agents in the treatment of melanoma.

Effects of psychotropic drugs on cell proliferation and differentiation

Some of the psychotropic agents widely used for the amelioration of anxiety, depression, and psychosis also show an effect at the cellular proliferation level. Surprisingly little research, however, has been directed to the antitumoral potential of these drugs, alone or in combination with established cancer treatments. Our review of the literature to date has yielded some promising early findings. Ligands active at the benzodiazepine (BZ) receptors have been studied the most extensively and were found to have differential, concentration-dependent effects on the growth and proliferation of both normal and cancer cells. Of the phenothiazines tested, chlorpromazine (CPZ) and perphenazine (PPZ) had the most potent cytotoxic action on fibroblasts and glioma cells. Antiproliferative effects also were noted by these and other agents in leukemic and breast cancer cell lines. Additional psychotropic drugs studied include the atypical antipsychotics, antidepressants, and mood stabilizers, especially lithium. Most of the reported activities were observed in in vitro studies and were achieved at high pharmacological concentrations. Further in vivo studies in well-designed animal models are warranted to determine whether these well-tolerated, relatively inexpensive, and widely available drugs or their derivatives may be added in the future to the armamentarium of cancer pharmacotherapy.

Ca2+-induced changes in energy metabolism and viability of melanoma cells

Cancer cells are characterized by a high rate of glycolysis, which is their primary energy source. We show here that a rise in intracellular-free calcium ion (Ca2+), induced by Ca2+-ionophore A23187, exerted a deleterious effect on glycolysis and viability of B16 melanoma cells. Ca2+-ionophore caused a dose-dependent detachment of phosphofructokinase (EC 2.7.1.11), one of the key enzymes of glycolysis, from cytoskeleton. It also induced a decrease in the levels of glucose 1,6-bisphosphate and fructose 1,6-bisphosphate, the two stimulatory signal molecules of glycolysis. All these changes occurred at lower concentrations of the drug than those required to induce a reduction in viability of melanoma cells. We also found that low concentrations of Ca2+-ionophore induced an increase in adenosine 5'-triphosphate (ATP), which most probably resulted from the increase in mitochondrial-bound hexokinase, which reflects a defence mechanism. This mechanism can no longer operate at high concentrations of the Ca2+-ionophore, which causes a decrease in mitochondrial and cytosolic hexokinase, leading to a drastic fall in ATP and melanoma cell death. The present results suggest that drugs which are capable of inducing accumulation of intracellular-free Ca2+ in melanoma cells would cause a reduction in energy-producing systems, leading to melanoma cell death.

Effects of Ca(2+)-ionophore A23187 and calmodulin antagonists on regulatory mechanisms of glycolysis and cell viability of NIH-3T3 fibroblasts

We studied here, in NIH-3T3 fibroblasts, the effect of the Ca(2+)-ionophore A23187 (which is known to increase intracellular-free Ca(2+)) on the control of glycolysis and cell viability and the action of calmodulin antagonists. Time-response studies with Ca(2+)-ionophore A23187 have revealed dual effects on the distribution of phosphofructokinase (PFK) (EC 2.7.1.11), the rate-limiting enzyme of glycolysis, between the cytoskeletal and cytosolic (soluble) fractions of the cell. A short incubation (maximal effect after 7 min) caused an increase in cytoskeleton-bound PFK with a corresponding decrease in soluble activity. This leads to an enhancement of cytoskeletal glycolysis. A longer incubation with Ca(2+)-ionophore caused a reduction in both cytoskeletal and cytosolic PFK and cell death. Both the "physiological" and "pathological" phases of the Ca(2+)-induced changes in the distribution of PFK were prevented by treatment with three structurally different calmodulin antagonists, thioridazine, an antipsychotic phenothiazine, clotrimazole, from the group of antifungal azole derivatives that were recently recognized as calmodulin antagonists, and CGS 9343B, a more selective inhibitor of calmodulin activity. The longer incubation with Ca(2+)-ionophore also induced a decrease in the levels of glucose 1,6-bisphosphate and fructose 1,6-bisphosphate, the two allosteric stimulatory signal molecules of glycolysis. All these pathological changes preceded the reduction in cell viability, and a strong correlation was found between the fall in ATP and cell death. All three calmodulin antagonists prevented the pathological reduction in the levels of the allosteric effectors, ATP and cell viability. These experiments may throw light on the mechanisms underlying the therapeutic action of calmodulin antagonists that we previously found in treatment of the proliferating melanoma cells, on the one hand, and skin injuries, on the other hand.

Taxol (paclitaxel) induces a detachment of phosphofructokinase from cytoskeleton of melanoma cells and decreases the levels of glucose 1,6-bisphosphate, fructose 1,6-bisphosphate and ATP

Glucose utilization through glycolysis, which is the primary energy source in cancer cells, is known to be controlled by allosteric regulators, as well as by reversible binding of glycolytic enzymes to cytoskeleton. Here we report of a novel mechanism of action of taxol (paclitaxel; Baccatin III N-benzyl-beta-phenylisoserine ester), the anti-microtubule agent with remarkable anticancer activity. We show that taxol affects both levels of regulation of glycolysis in melanoma cells; it decreases the levels of glucose 1,6-bisphosphate and fructose 1,6-bisphosphate, the two allosteric stimulatory signal molecules of glycolysis, and also causes a detachment of phosphofructokinase (ATP: D-fructose-6-phosphate 1-phosphotransferase, EC 2.7.1.11), the rate-limiting enzyme of glycolysis, from the cytoskeleton of B16 melanoma cells. These effects of taxol were dose-dependent, and preceded the decrease in ATP levels and cell viability. Thus, taxol not only inhibits the essential dynamic processes of microtubule network, but also reduces glycolysis, through the novel mechanisms described here.

Dequalinium induces a selective depletion of mitochondrial DNA from HeLa human cervical carcinoma cells

Treatment of cultured human cervical carcinoma cells with the anticancer drug dequalinium (DEQ) was found to cause a delayed inhibition of cell growth. This inhibition was preceded by a loss of mitochondrial DNA (mtDNA), a decrease in cytochrome c oxidase activity, and an increase in the level of lactate, indicating that growth inhibition was due to the loss of mtDNA-encoded functions. There was a progressive two-fold loss of mtDNA following each cell division in the presence of DEQ, suggesting that this drug was acting by inhibiting some aspect of mtDNA synthesis. Furthermore, cells became resistant to the growth inhibitory and cytotoxic affects of DEQ when they were grown under conditions that bypassed the need for mtDNA-encoded functions. Resistance was not associated with significant changes in drug accumulation. These results suggest that the DEQ-induced depletion of mtDNA plays an important role in drug cytotoxicity.

Insulin stimulates binding of phosphofructokinase to cytoskeleton and increases glucose 1,6-bisphosphate levels in NIH-3T3 fibroblasts, which is prevented by calmodulin antagonists

We report here a novel mechanism of insulin action in cultures of NIH-3T3 fibroblasts. Our experiments revealed that in these cells, insulin induced a rapid and transient increase in cytoskeleton-bound phosphofructokinase (EC 2.7.1.11), the rate-limiting enzyme in glycolysis, with a corresponding decrease in soluble (cytosolic) activity. Insulin also induced a slower increase in the levels of glucose 1,6-bisphosphate, the potent activator of cytosolic glycolysis. Both the rapid and the slower stimulatory actions of insulin were prevented by treatment with structurally different calmodulin antagonists, which strongly suggest that calmodulin is involved in these effects of insulin. The present and our previous experiments in muscle suggest that rapid, Ca2+-calmodulin-mediated increase in the binding of glycolytic enzymes to cytoskeleton, as well as the slower increase in glucose 1,6-bisphosphate, may be a general mechanism, in different cells, in signal transduction of insulin.

Clotrimazole and bifonazole detach hexokinase from mitochondria of melanoma cells

Cancer cells are characterized by a high rate of glycolysis. Hexokinase (ATP: D-hexose 6-phosphotransferase, EC 2.7.1.1), the only glycolytic enzyme which binds to mitochondria, is exceptionally high in cancer cells, and believed to play a key role in regulating cell energy metabolism and cancer cell growth rate. We have previously found that clotrimazole (1-(alpha-2-chlorotrityl)imidazole) and bifonazole (1-(alpha-biphenyl-4-ylbenzyl)imidazole), the antifungal azole derivatives, which were recently recognized as calmodulin antagonists, are calmodulin antagonists which most effectively reduce glycolysis and ATP level in B16 melanoma cells. They act through allosteric regulation and detachment of glycolytic enzymes from cytoskeleton. Here we report of a novel, additional, mechanism of action of these drugs. We show that they induce a dose-dependent detachment of hexokinase from mitochondria of B16 melanoma cells. This effect preceded the decrease in cell viability. These results suggest that clotrimazole and bifonazole may be promising drugs in treatment of melanoma.

Detachment of glycolytic enzymes from cytoskeleton of melanoma cells induced by calmodulin antagonists

Glycolysis, which is the primary energy source in cancer cells, is known to be controlled by allosteric regulators, as well as by reversible binding of glycolytic enzymes to cytoskeleton. We have previously found that different calmodulin antagonists decrease the levels of allosteric activators of glycolysis, and reduce ATP content and cell viability in B16 melanoma cells. Here we report of a novel, additional, mechanism of action of calmodulin antagonists in melanoma cells. We show that these drugs cause a detachment of the glycolytic enzymes, phosphofructokinase (ATP: D-fructose-6-phosphate 1-phosphotransferase, EC 2.7.1.11) and aldolase (D-fructose-1,6-bisphosphate D-glyceraldehyde-3-phosphate-lyase, EC 4.1.2.13), from cytoskeleton of B16 melanoma cells. This effect was dose- and time-dependent, and preceded the decrease in cell viability. The detachment of glycolytic enzymes from cytoskeleton would reduce the provision of local ATP, in the vicinity of the cytoskeleton-membrane and would affect cytoskeleton structure. Since the cytoskeleton is being recognized as an important modulator of cell function, proliferation, differentiation and neoplasia, detachment of the glycolytic enzymes from cytoskeleton induced by calmodulin antagonists, as well as their reported inhibitory action on cell proliferation, make these drugs most promising agents in treatment of cancer.

Serotonin decreases cytoskeletal and cytosolic glycolytic enzymes and the levels of ATP and glucose 1,6-bisphosphate in skin, which is prevented by the calmodulin antagonists thioridazine and clotrimazole

Serotonin (5-hydroxytryptamine) is believed to play a pathogenic role in skin damage and various skin abnormalities; however, its mechanism of action remains unknown. We show here that intradermal injection of serotonin in rats induced a marked reduction in the activities of the glycolytic enzymes, phosphofructokinase (EC 2.7.1.11) and aldolase (EC 4.1.2.13), in both the cytoskeletal and cytosolic fractions from skin. Serotonin also decreased the levels of glucose 1,6-bisphosphate in skin, the powerful regulator of glucose metabolism. These serotonin-induced changes were accompanied by a marked decrease in ATP content in skin. All these pathological changes induced by serotonin were prevented by treatment with two structurally different calmodulin antagonists: thioridazine, an antipsychotic phenothiazine, or clotrimazole, from the group of the antifungal azole derivatives that were recently recognized as calmodulin antagonists. The present results suggest that calmodulin antagonists may be effective drugs in the treatment of skin damage under various pathological conditions and diseases in which serotonin levels are increased.