Dichloroacetate induces apoptosis of epithelial ovarian cancer cells through a mechanism involving modulation of oxidative stress

Is there a link between talcum powder, oxidative stress, and ovarian cancer risk?

INTRODUCTION

The link between talcum powder use and cancer, particularly ovarian cancer, has been a topic of scientific research and legal debate for several years. Studies have suggested a potential association between long-term talcum powder use in the genital area and an increased risk of ovarian cancer.

AREAS COVERED

The following report includes up-to-date evidence to support the potential link between talcum powder use and the risk of developing ovarian cancer. The International Agency for Research on Cancer, which is part of the World Health Organization, classified talc-based body powder as possibly carcinogenic to humans when used in the female genital area. However, other studies have not consistently supported this association, and thus more research is needed to establish a clear and definitive link between talcum powder use and cancer. Despite this, recent molecular-level data have linked talc to alterations in redox balance, gene mutations, and inflammatory responses. Specifically, we have identified a role for talc to induce the pro-oxidant state, inhibit apoptosis, and more importantly induced cellular transformation in normal ovarian cells.

EXPERT OPINION

We presented unequivocal evidence to support our opinion that talc is not biologically inert and induces molecular changes that mimic the hallmarks of cancer.

Dichloroacetate for Cancer Treatment: Some Facts and Many Doubts

Rarely has a chemical elicited as much controversy as dichloroacetate (DCA). DCA was initially considered a dangerous toxic industrial waste product, then a potential treatment for lactic acidosis. However, the main controversies started in 2008 when DCA was found to have anti-cancer effects on experimental animals. These publications showed contradictory results in vivo and in vitro such that a thorough consideration of this compound's in cancer is merited. Despite 50 years of experimentation, DCA's future in therapeutics is uncertain. Without adequate clinical trials and health authorities' approval, DCA has been introduced in off-label cancer treatments in alternative medicine clinics in Canada, Germany, and other European countries. The lack of well-planned clinical trials and its use by people without medical training has discouraged consideration by the scientific community. There are few thorough clinical studies of DCA, and many publications are individual case reports. Case reports of DCA's benefits against cancer have been increasing recently. Furthermore, it has been shown that DCA synergizes with conventional treatments and other repurposable drugs. Beyond the classic DCA target, pyruvate dehydrogenase kinase, new target molecules have also been recently discovered. These findings have renewed interest in DCA. This paper explores whether existing evidence justifies further research on DCA for cancer treatment and it explores the role DCA may play in it.

Management of ulcerative colitis by dichloroacetate: Impact on NFATC1/NLRP3/IL1B signaling based on bioinformatics analysis combined with in vivo experimental verification

The inflammatory response in ulcerative colitis (UC) could be relieved by the conventional immunomodulatory agents; 5-aminosalicylic acid, corticosteroids, or azathioprine. However, the low remission rates and the intolerance to these agents necessitate investigation of gene expression signature in UC that could influence the therapeutic efficacy of drugs, as well as the interference with persistence genes by novel therapeutic option. Three microarray datasets (GSE66407, GSE38713 and GSE14580) from the NCBI-GEO database were utilized. Differentially expressed genes between samples of patients with UC and healthy ones were analyzed using R software. In addition, in vivo study using oxazolone-induced UC in BALB/c mice was carried out to investigate the proposed therapeutic efficacy of dichloroacetate (DCA). The bioinformatics analysis revealed the persistence of NLRP3, NFATC1, and IL1B in UC despite treatment with common therapeutic agents. DCA administration to oxazolone-treated mice showed remarkable interference with those persistence genes. Western blotting analysis for NLRP3, NFATC1, nuclear/total NF-κB, and cleaved caspase-1 revealed the ability of DCA to reduce the expression levels of these proteins in oxazolone-treated mice. Additionally, the inflammatory cytokines IL-1β and IL-13 were reduced in colonic tissue by DCA treatment. The therapeutic efficacy of DCA was further confirmed by the apparent reduction in histopathological scoring, disease activity index, and the normalization of colon length. Therefore, DCA could be suggested as a novel and promising therapeutic option in UC based on its ability to interfere with the persistence of NFATC1/NLRP3/IL1B signaling. That merits further safety/toxicological pre-clinical assessment and update of bioavailability/metabolism data prior to clinical investigation.

Monomeric myeloperoxidase is a specific biomarker for early-stage ovarian cancer

Background: Ovarian cancer cells are known to express myeloperoxidase (MPO), an oxidant-producing enzyme with a 150 kDa homodimer, consisting of two identical monomers connected by a disulfide bond. Here, we aim to validate monomeric MPO (mMPO) as a biomarker for the early detection of ovarian cancer.Methods: Human ovarian cancer cells, sera from patients at various stages, sera from non-cancer inflammatory gynecological diseases, and healthy volunteers were used. Monomeric and dimeric MPO were measured by ELISA. Receiver operating curves were used to compare the predictive powers of serum dimeric and monomeric MPO to discriminate between samples.Results: The expression of MPO was unique to ovarian cancer cells. Specifically, mMPO was found to be the only form of MPO in all ovarian cancer cell lines. Intriguingly, mMPO was detected in the sera from all patients with ovarian cancer at various stages, but not from healthy individuals. Serum mMPO discriminated between early-stage ovarian cancer, healthy controls, and benign inflammatory gynecologic disorders. In addition, mMPO discriminated between the early and late stages of the disease.Conclusion: This work highlights mMPO as a potential biomarker for early detection of ovarian cancer, which is critically needed.

Redox Signaling Modulates Activity of Immune Checkpoint Inhibitors in Cancer Patients

Although immunotherapy is already a staple of cancer care, many patients may not benefit from these cutting-edge treatments. A crucial field of research now focuses on figuring out how to improve treatment efficacy and assess the resistance mechanisms underlying this uneven response. For a good response, immune-based treatments, in particular immune checkpoint inhibitors, rely on a strong infiltration of T cells into the tumour microenvironment. The severe metabolic environment that immune cells must endure can drastically reduce effector activity. These immune dysregulation-related tumour-mediated perturbations include oxidative stress, which can encourage lipid peroxidation, ER stress, and T regulatory cells dysfunction. In this review, we have made an effort to characterize the status of immunological checkpoints, the degree of oxidative stress, and the part that latter plays in determining the therapeutic impact of immunological check point inhibitors in different neoplastic diseases. In the second section of the review, we will make an effort to assess new therapeutic possibilities that, by affecting redox signalling, may modify the effectiveness of immunological treatment.

Identifying the Role of Oxidative Stress-Related Genes as Prognostic Biomarkers and Predicting the Response of Immunotherapy and Chemotherapy in Ovarian Cancer

Background

Ovarian cancer (OC) is one of the most frequently seen and fatal gynecological malignancies, and oxidative stress (OS) plays a critical role in the development and chemoresistance of OC.

Materials and Methods

OS-related genes (OSRGs) were obtained from the Molecular Signatures Database. Besides, gene expression profiles and clinical information from The Cancer Genome Atlas (TCGA) were selected to identify the prognostic OSRGs. Moreover, univariate Cox regression, LASSO, and multivariate Cox regression analyses were conducted sequentially to establish a prognostic signature, which was later validated in three independent Gene Expression Omnibus (GEO) datasets. Next, gene set enrichment analysis (GSEA) and tumor mutation burden (TMB) analysis were performed. Afterwards, immune checkpoint genes (ICGs) and the tumor immune dysfunction and exclusion (TIDE) algorithm, together with IMvigor210 and GSE78220 cohorts, were applied to comprehensively explore the role of OSRG signature in immunotherapy. Further, the CellMiner and Genomics of Drug Sensitivity in Cancer (GDSC) databases were also applied in investigating the significance of OSRG signature in chemotherapy.

Results

Altogether, 34 prognostic OSRGs were identified, among which 14 were chosen to establish the most valuable prognostic signature. The Kaplan-Meier (KM) analysis suggested that patients with lower OS-related risk score had better prognosis. The area under the curve (AUC) values were 0.71, 0.76, and 0.85 in 3, 5, and 7 years separately, and the stability of this prognostic signature was confirmed in three GEO datasets. As revealed by GSEA and TMB analysis results, OC patients in low-risk group might have better immunotherapeutic response, which was consistent with ICG expression and TIDE analyses. Moreover, both IMvigor210 and GSE78220 cohorts demonstrated that patients with lower OS-related risk score were more likely to benefit from anti-PD-1/L1 immunotherapy. In addition, the association between prognostic signature and drug sensitivity was explored.

Conclusion

According to our results in this work, OSRG signature can act as a powerful prognostic predictor for OC, which contributes to generating more individualized therapeutic strategies for OC patients.

Impact of EcSOD Perturbations in Cancer Progression

Reactive oxygen species (ROS) are a normal byproduct of cellular metabolism and are required components in cell signaling and immune responses. However, an imbalance of ROS can lead to oxidative stress in various pathological states. Increases in oxidative stress are one of the hallmarks in cancer cells, which display an altered metabolism when compared to corresponding normal cells. Extracellular superoxide dismutase (EcSOD) is an antioxidant enzyme that catalyzes the dismutation of superoxide anion (O₂⁻) in the extracellular environment. By doing so, this enzyme provides the cell with a defense against oxidative damage by contributing to redox balance. Interestingly, EcSOD expression has been found to be decreased in a variety of cancers, and this loss of expression may contribute to the development and progression of malignancies. In addition, recent compounds can increase EcSOD activity and expression, which has the potential for altering this redox signaling and cellular proliferation. This review will explore the role that EcSOD expression plays in cancer in order to better understand its potential as a tool for the detection, predicted outcomes and potential treatment of malignancies.

Metabolic-targeted Combination Therapy With Dichloroacetate and Metformin Suppresses Glioblastoma Cell Line Growth In Vitro and In Vivo

BACKGROUND/AIM

We investigated the hypothesis that dichloroacetate (DCA), a pyruvate dehydrogenase kinase inhibitor, and metformin (MET), an antidiabetic agent and complex I inhibitor, have synergistic cytotoxic effects in glioblastoma cells in vitro and in vivo.

MATERIALS AND METHODS

We performed dose response experiments and combination index calculation. Apoptotic and necrotic cells were estimated by flow cytometry. Cell metabolism was evaluated by Seahorse analysis and lactate export. Overall survival and tumor volume growth experiments were performed in C57BL/6 mice GL-261 allograft model.

RESULTS

DCA and MET showed dose-dependent cytotoxicity and synergistic effects. DCA alleviated the increase in lactate production induced by MET. Seahorse analysis showed that DCA treatment results in increased oxygen consumption rate, which is decreased by MET. DCA and MET significantly inhibited tumor growth and increased overall survival in mice.

CONCLUSION

Compounds targeting tumor cell metabolism could become potential treatment options for glioblastoma multiforme.

Dichloroacetate and PX-478 exhibit strong synergistic effects in a various number of cancer cell lines

Background

One key approach for anticancer therapy is drug combination. Drug combinations can help reduce doses and thereby decrease side effects. Furthermore, the likelihood of drug resistance is reduced. Distinct alterations in tumor metabolism have been described in past decades, but metabolism has yet to be targeted in clinical cancer therapy. Recently, we found evidence for synergism between dichloroacetate (DCA), a pyruvate dehydrogenase kinase inhibitor, and the HIF-1α inhibitor PX-478. In this study, we aimed to analyse this synergism in cell lines of different cancer types and to identify the underlying biochemical mechanisms.

Methods

The dose-dependent antiproliferative effects of the single drugs and their combination were assessed using SRB assays. FACS, Western blot and HPLC analyses were performed to investigate changes in reactive oxygen species levels, apoptosis and the cell cycle. Additionally, real-time metabolic analyses (Seahorse) were performed with DCA-treated MCF-7 cells.

Results

The combination of DCA and PX-478 produced synergistic effects in all eight cancer cell lines tested, including colorectal, lung, breast, cervical, liver and brain cancer. Reactive oxygen species generation and apoptosis played important roles in this synergism. Furthermore, cell proliferation was inhibited by the combination treatment.

Conclusions

Here, we found that these tumor metabolism-targeting compounds exhibited a potent synergism across all tested cancer cell lines. Thus, we highly recommend the combination of these two compounds for progression to in vivo translational and clinical trials.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08186-9.

Metabolic Classification and Intervention Opportunities for Tumor Energy Dysfunction

A comprehensive view of cell metabolism provides a new vision of cancer, conceptualized as tissue with cellular-altered metabolism and energetic dysfunction, which can shed light on pathophysiological mechanisms. Cancer is now considered a heterogeneous ecosystem, formed by tumor cells and the microenvironment, which is molecularly, phenotypically, and metabolically reprogrammable. A wealth of evidence confirms metabolic reprogramming activity as the minimum common denominator of cancer, grouping together a wide variety of aberrations that can affect any of the different metabolic pathways involved in cell physiology. This forms the basis for a new proposed classification of cancer according to the altered metabolic pathway(s) and degree of energy dysfunction. Enhanced understanding of the metabolic reprogramming pathways of fatty acids, amino acids, carbohydrates, hypoxia, and acidosis can bring about new therapeutic intervention possibilities from a metabolic perspective of cancer.

Combinatorial Effect of DCA and Let-7a on Triple-Negative MDA-MB-231 Cells: A Metabolic Approach of Treatment

Dichloroacetate (DCA) is a metabolic modulator that inhibits pyruvate dehydrogenase activity and promotes the influx of pyruvate into the tricarboxylic acid cycle for complete oxidation of glucose. DCA stimulates oxidative phosphorylation (OXPHOS) more than glycolysis by altering the morphology of the mitochondria and supports mitochondrial apoptosis. As a consequence, DCA induces apoptosis in cancer cells and inhibits the proliferation of cancer cells. Recently, the role of miRNAs has been reported in regulating gene expression at the transcriptional level and also in reprogramming energy metabolism. In this article, we indicate that DCA treatment leads to the upregulation of let-7a expression, but DCA-induced cancer cell death is independent of let-7a. We observed that the combined effect of DCA and let-7a induces apoptosis, reduces reactive oxygen species generation and autophagy, and stimulates mitochondrial biogenesis. This was later accompanied by stimulation of OXPHOS in combined treatment and was thus involved in metabolic reprogramming of MDA-MB-231 cells.

Genetically Raised Circulating Bilirubin Levels and Risk of Ten Cancers: A Mendelian Randomization Study

Bilirubin, an endogenous antioxidant, may play a protective role in cancer development. We applied two-sample Mendelian randomization to investigate whether genetically raised bilirubin levels are causally associated with the risk of ten cancers (pancreas, kidney, endometrium, ovary, breast, prostate, lung, Hodgkin's lymphoma, melanoma, and neuroblastoma). The number of cases and their matched controls of European descent ranged from 122,977 and 105,974 for breast cancer to 1200 and 6417 for Hodgkin's lymphoma, respectively. A total of 115 single-nucleotide polymorphisms (SNPs) associated (p < 5 × 10-8) with circulating total bilirubin, extracted from a genome-wide association study in the UK Biobank, were used as instrumental variables. One SNP (rs6431625) in the promoter region of the uridine-diphosphoglucuronate glucuronosyltransferase1A1 (UGT1A1) gene explained 16.9% and the remaining 114 SNPs (non-UGT1A1 SNPs) explained 3.1% of phenotypic variance in circulating bilirubin levels. A one-standarddeviation increment in circulating bilirubin (≈ 4.4 µmol/L), predicted by non-UGT1A1 SNPs, was inversely associated with risk of squamous cell lung cancer and Hodgkin's lymphoma (odds ratio (OR) 0.85, 95% confidence interval (CI) 0.73-0.99, P 0.04 and OR 0.64, 95% CI 0.42-0.99, p 0.04, respectively), which was confirmed after removing potential pleiotropic SNPs. In contrast, a positive association was observed with the risk of breast cancer after removing potential pleiotropic SNPs (OR 1.12, 95% CI 1.04-1.20, p 0.002). There was little evidence for robust associations with the other seven cancers investigated. Genetically raised bilirubin levels were inversely associated with risk of squamous cell lung cancer as well as Hodgkin's lymphoma and positively associated with risk of breast cancer. Further studies are required to investigate the utility of bilirubin as a low-cost clinical marker to improve risk prediction for certain cancers.

Ascites-derived ALDH+CD44+ tumour cell subsets endow stemness, metastasis and metabolic switch via PDK4-mediated STAT3/AKT/NF-κB/IL-8 signalling in ovarian cancer

Background

Ovarian cancer is characterised by frequent recurrence due to persistent presence of residual cancer stem cells (CSCs). Here, we identify and characterise tumour subsets from ascites-derived tumour cells with stemness, metastasis and metabolic switch properties and to delineate the involvement of pyruvate dehydrogenase kinase 4 (PDK4) in such process.

Methods

Ovarian cancer cells/cell lines derived from ascites were used for tumourspheres/ALDH+CD44+ subset isolation. The functional roles and downstream signalling of PDK4 were explored. Its association with clinical outcome of ovarian cancer was analysed.

Results

We demonstrated enhanced CSC characteristics of tumour cells derived from ovarian cancer ascites, concomitant with ALDH and CD44 subset enrichment and high PDK4 expression, compared to primary tumours. We further showed tumourspheres/ALDH+CD44+ subsets from ascites-derived tumour cells/cell lines with CSC properties and enhanced glycolysis. Clinically, PDK4 expression was correlated with aggressive features. Notably, blockade of PDK4 in tumourspheres/ALDH+CD44+ subsets led to inhibition of CSC characteristics, glycolysis and activation of STAT3/AKT/NF-κB/IL-8 (signal transducer and activator of transcription 3/protein kinases B/nuclear factor-κB/interleukin-8) signalling. Conversely, overexpression of PDK4 in ALDH−CD44– subsets exerted the opposite effects.

Conclusion

Ascites-derived ALDH+CD44+ tumour cell subsets endow stemness, metastatic and metabolic switch properties via PDK4-mediated STAT3/AKT/NF-κB/IL-8 signalling, suggesting PDK4 as a viable therapeutic molecular target for ovarian cancer management.

Logical modelling reveals the PDC-PDK interaction as the regulatory switch driving metabolic flexibility at the cellular level

BACKGROUND

Metabolic flexibility is the ability of an organism to switch between substrates for energy metabolism, in response to the changing nutritional state and needs of the organism. On the cellular level, metabolic flexibility revolves around the tricarboxylic acid cycle by switching acetyl coenzyme A production from glucose to fatty acids and vice versa. In this study, we modelled cellular metabolic flexibility by constructing a logical model connecting glycolysis, fatty acid oxidation, fatty acid synthesis and the tricarboxylic acid cycle, and then using network analysis to study the behaviours of the model.

RESULTS

We observed that the substrate switching usually occurs through the inhibition of pyruvate dehydrogenase complex (PDC) by pyruvate dehydrogenase kinases (PDK), which moves the metabolism from glycolysis to fatty acid oxidation. Furthermore, we were able to verify four different regulatory models of PDK to contain known biological observations, leading to the biological plausibility of all four models across different cells and conditions.

CONCLUSION

These results suggest that the cellular metabolic flexibility depends upon the PDC-PDK regulatory interaction as a key regulatory switch for changing metabolic substrates.

Two dichloric compounds inhibit in vivo U87 xenograft tumor growth

Dichloroacetate (DCA) is an inhibitor of pyruvate dehydrogenase kinase (PDK) that has been shown to reverse the Warburg effect and cause tumor cell death. Clinical research into the anti-cancer activity of DCA revealed high dosage requirements and reports of toxicity. While there have been subsequent mechanistic investigations, a search for DCA alternatives could result in a safer and more effective anticancer therapy. This study evaluates eight small compounds with a conserved dichloric terminal and their in vitro and in vivo potential for anticancer activity. Initial viability screening across six cancer cell lines reveals even at 10 mg/mL, compound treatments do not result in complete cell death which suggests minimal compound cytotoxicity. Furthermore, in vivo data demonstrates that cationic dichloric compounds DCAH and DCMAH, which were selected for further testing based on highest in vitro viability impact, inhibit tumor growth in the U87 model of glioblastoma, suggesting their clinical potential as accessible anti-cancer drugs. Immunoblotting signaling data from tumor lysates demonstrates that the mechanism of actions of cationic DCAH and DCMAH are unlikely to be consistent with that of the terminally carboxylic DCA and warrants further independent investigation.

DNA damage response and repair in ovarian cancer: Potential targets for therapeutic strategies

Ovarian cancer is among the most lethal gynecologic malignancies with a poor survival prognosis. The current therapeutic strategies involve surgery and chemotherapy. Research is now focused on novel agents especially those targeting DNA damage response (DDR) pathways. Understanding the DDR process in ovarian cancer necessitates having a detailed knowledge on a series of signaling mediators at the cellular and molecular levels. The complexity of the DDR process in ovarian cancer and how this process works in metastatic conditions is comprehensively reviewed. For evaluating the efficacy of therapeutic agents targeting DNA damage in ovarian cancer, we will discuss the components of this system including DDR sensors, DDR transducers, DDR mediators, and DDR effectors. The constituent pathways include DNA repair machinery, cell cycle checkpoints, and apoptotic pathways. We also will assess the potential of active mediators involved in the DDR process such as therapeutic and prognostic candidates that may facilitate future studies.

Quercetin: a natural compound for ovarian cancer treatment

Ovarian cancer is the main cause of death among all reproductive cancers in females. In 2018, ovarian cancer was the seventh most common cancer of women entire the world. A wide variety of molecular and genetic alterations as well as different response to therapies in the different types of ovarian cancer lead to problems in design a common therapeutic strategy. Besides, ovarian cancer cells have tendency to acquire resistance to common cancer treatments through multiple mechanisms. Various factors, including cytokines, growth factors, proteases, adhesion molecules, coagulation factors, hormones and apoptotic agents have been examined to find effective cancer treatment. Phytochemicals have been indicated to have great potential anti-cancer properties against various types of cancers. Quercetin is one of the phytochemicals that exists extensively in daily foods. Wide evidences revealed that quercetin is able to inhibit various types of cancers including breast, lung, nasopharyngeal, kidney, colorectal, prostate, pancreatic, and ovarian cancer. Several in vitro and in vivo studied conducted to evaluate cytotoxic effects of quercetin on ovarian cancer. Since quercetin does not harm healthy cells and it is cytotoxic to cancer cells via various mechanisms, researchers suggest that it could be an ideal agent for ovarian cancer treatment or an adjuvant agent in combination with other anti-cancer drugs. Thus, in this review, we focused on chemo-preventive and curative attitude of quercetin for ovarian cancer and summarize some of the most recent findings which regard the possible molecular mechanisms by which this natural compound inhibits this cancer.

Inhibition of glycolysis disrupts cellular antioxidant defense and sensitizes HepG2 cells to doxorubicin treatment

Increased glucose consumption is a known hallmark of cancer cells. Increased glycolysis provides ATP, reducing agents and substrates for macromolecular synthesis in intensely dividing cells. Therefore, inhibition of glycolysis is one strategy in anticancer therapy as well as in improved efficacy of conventional anticancer chemotherapeutic agents. One such agent is doxorubicin (DOX), but the mechanism of sensitization of tumor cells to DOX by inhibition of glycolysis has not been fully elucidated. As oxidative stress is an important phenomenon accompanying DOX action and antioxidant defense is closely related to energy metabolism, the aim of the study was the evaluation of oxidative stress markers and antioxidant abilities of cancer cells treated with DOX while glycolysis is inhibited. HepG2 cells were treated with DOX and one of three glycolysis inhibitors: 2-deoxyglucose, dichloroacetate or 3-promopyruvate. To evaluate the possible interaction mechanisms, we assessed mRNA expression of selected genes related to energy metabolism and antioxidant defense; oxidative stress markers; and reduced glutathione (GSH) and NADPH levels. Additionally, glutamine consumption was measured. It was demonstrated that the chemotherapeutic agent and glycolysis inhibitors induced oxidative stress and associated damage in HepG2 cells. However, simultaneous treatment with both agents resulted in even greater lipid peroxidation and a significant reduction in GSH and NADPH levels. Moreover, in the presence of the drug and an inhibitor, HepG2 cells had a reduced ability to take up glutamine. These results indicated that cells treated with DOX while glycolysis was inhibited had significantly reduced ability to produce NADPH and antioxidant defenses.

Dichloroacetic acid upregulates apoptosis of ovarian cancer cells by regulating mitochondrial function

Background

Metabolic reprogramming is a characteristic of tumor cells and is considered a potential therapeutic target. Even under aerobic conditions, tumor cells use glycolysis to produce energy, a phenomenon called the “Warburg effect”. Pyruvate dehydrogenase kinase 1 (PDK1) is a key factor linking glycolysis and the tricarboxylic acid cycle. Dichloroacetic acid (DCA) reverses the Warburg effect by inhibition of PDK1 to switch cytoplasmic glucose metabolism to mitochondrial oxidative phosphorylation (OXPHOS).

Methods

Cell viability was examined using a standard MTT assay. Glucose consumption and l-lactate production were measured using commercial colorimetric kits, and intracellular lactate dehydrogenase (LDH) activity was evaluated using cell lysates and an LDH Quantification Kit. Real-time PCR was used to detect the expression of related genes. The production of total ROS was evaluated by staining with dichlorofluorescin diacetate.

Results

Comparison of various aspects of glucose metabolism, such as expression of key enzymes in glycolysis, lactate production, glucose consumption, mitochondrial oxygen consumption rate, and citric acid production, revealed that A2780/DDP cells were primarily dependent on glycolysis whereas A2780 cells were primarily dependent on mitochondrial OXPHOS. Mitochondrial uncoupling protein 2 (UCP2) protects against mitochondrial ROS while allowing energy metabolism to switch to glycolysis. Treatment of A2780 cells with various concentrations of DCA resulted in decreased expression of UCP2, a metabolic switch from glycolysis to mitochondrial OXPHOS, and an increase in oxidative stress induced by ROS. These effects were not observed in A2780/DDP cells with higher UCP2 expression suggesting that UCP2 might induce changes in mitochondrial functions that result in different sensitivities to DCA.

Conclusion

Our results show that a drug targeting tumor metabolic changes affects almost the entire process of glucose metabolism. Thus, it is necessary to comprehensively determine tumor metabolic functions to facilitate individualized antitumor therapy.

Cancer Etiology: A Metabolic Disease Originating from Life's Major Evolutionary Transition?

A clear understanding of the origins of cancer is the basis of successful strategies for effective cancer prevention and management. The origin of cancer at the molecular and cellular levels is not well understood. Is the primary cause of the origin of cancer the genomic instability or impaired energy metabolism? An attempt was made to present cancer etiology originating from life's major evolutionary transition. The first evolutionary transition went from simple to complex cells when eukaryotic cells with glycolytic energy production merged with the oxidative mitochondrion (The Endosymbiosis Theory first proposed by Lynn Margulis in the 1960s). The second transition went from single-celled to multicellular organisms once the cells obtained mitochondria, which enabled them to obtain a higher amount of energy. Evidence will be presented that these two transitions, as well as the decline of NAD+ and ATP levels, are the root of cancer diseases. Restoring redox homeostasis and reactivation of mitochondrial oxidative metabolism are important factors in cancer prevention.

Effects of dichloroacetate as single agent or in combination with GW6471 and metformin in paraganglioma cells

Paragangliomas (PGLs) are infiltrating autonomic nervous system tumors that cause important morbidity. At present, surgery is the only effective therapeutic option for this rare tumor. Thus, new agents for PGL treatment should be identified. Using unique PGL cell models established in our laboratory, we evaluated the effect of dichloroacetate (DCA) as single agent or in a novel combination with other metabolic drugs, including GW6471 and metformin. DCA and metformin had not been tested before in PGL. DCA reduced PGL cell viability and growth through mechanisms involving reactivation of PDH complex leading to promotion of oxidative metabolism, with lowering of lactate and enhanced ROS production. This resulted in cell cycle inhibition and induction of apoptosis in PGL cells, as shown by flow cytometry and immunoblot analyses. Moreover, DCA drastically impaired clonogenic activity and migration of PGL cells. Also metformin reduced PGL cell viability as single agent and the combinations of DCA, GW6471 and metformin had strong effects on cell viability. Furthermore, combined treatments had drastic and synergistic effects on clonogenic ability. In conclusion, DCA, GW6471 and metformin as single agents and in combination appear to have promising antitumor effects in unique cell models of PGL.

Erastin-Like Anti-Warburg Agents Prevent Mitochondrial Depolarization Induced by Free Tubulin and Decrease Lactate Formation in Cancer Cells

In Warburg metabolism, suppression of mitochondrial metabolism contributes to a low cytosolic ATP/ADP ratio favoring enhanced aerobic glycolysis. Flux of metabolites across the mitochondrial outer membrane occurs through voltage-dependent anion channels (VDAC). In cancer cells, free dimeric tubulin induces VDAC closure and dynamically regulates mitochondrial membrane potential (ΔΨ). Erastin, a small molecule that binds to VDAC, antagonizes the inhibitory effect of tubulin on VDAC and hyperpolarizes mitochondria in intact cells. Here, our aim was to identify novel compounds from the ChemBridge DIVERSet library that block the inhibitory effect of tubulin on ΔΨ using cell-based screening. HCC4006 cells were treated with nocodazole (NCZ) to increase free tubulin and decrease ΔΨ in the presence or absence of library compounds. Tetramethylrhodamine methylester (TMRM) fluorescence was assessed by high-content imaging to determine changes in ΔΨ. Compounds were considered positive if ΔΨ increased in the presence of NCZ. Using confocal microscopy, we identified and validated six lead molecules that antagonized the depolarizing effect of NCZ. Lead compounds and erastin did not promote microtubule stabilization, so changes in ΔΨ were independent of tubulin dynamics. The most potent lead compound also decreased lactate formation. These novel small molecules represent a potential new class of anti-Warburg drugs.

Mitochondrial targeting by dichloroacetate improves outcome following hemorrhagic shock

Hemorrhagic shock is a leading cause of death in people under the age of 45 and accounts for almost half of trauma-related deaths. In order to develop a treatment strategy based on potentiating mitochondrial function, we investigated the effect of the orphan drug dichloroacetate (DCA) on survival in an animal model of hemorrhagic shock in the absence of fluid resuscitation. Hemorrhagic shock was induced in rats by withdrawing 60% of the blood volume and maintaining a hypotensive state. The studies demonstrated prolonged survival of rats subjected to hemorrhagic injury (HI) when treated with DCA. In separate experiments, using a fluid resuscitation model we studied mitochondrial functional alterations and changes in metabolic networks connected to mitochondria following HI and treatment with DCA. DCA treatment restored cardiac mitochondrial membrane potential and tissue ATP in the rats following HI. Treatment with DCA resulted in normalization of several metabolic and molecular parameters including plasma lactate and p-AMPK/AMPK, as well as Ach-mediated vascular relaxation. In conclusion we demonstrate that DCA can be successfully used in the treatment of hemorrhagic shock in the absence of fluid resuscitation; therefore DCA may be a good candidate in prolonged field care following severe blood loss.

Oxidative stress: a key regulator of leiomyoma cell survival

OBJECTIVE

To determine the effects of attenuating oxidative stress with the use of dichloroacetate (DCA) on the expression of key redox enzymes myeloperoxidase (MPO) and inducible nitric oxide synthase (iNOS) as well as on apoptosis.

DESIGN

Prospective experimental study.

SETTING

University medical center.

PATIENT(S)

Cells established from myometrium and uterine fibroid from the same patients.

INTERVENTION(S)

Cells were exposed to normal (20% O₂) or hypoxic (2% O₂) conditions for 24 hours with or without DCA (20 μg/mL), a metabolic modulator that shifts anaerobic to aerobic metabolism.

MAIN OUTCOME MEASURE(S)

Nitrate/nitrite (iNOS activity indicator), iNOS, Bcl-2/Bax ratio, MPO, and caspase-3 activities and levels were determined by means of Greiss assay, real-time reverse-transcription polymerase chain reaction, and ELISA. Data were analyzed with the use of SPSS by means of one-way analysis of variance with Tukey post hoc analysis and independent t tests.

RESULT(S)

MPO, iNOS, and nitrate/nitrite expression were higher in leiomyoma than in myometrial cells, and they were further enhanced by hypoxia in myometrial cells. Treatment with the use of DCA decreased MPO, iNOS, and nitrate/nitrite levels and negated the effect of hypoxia in both types of cells. Leiomyoma cells showed less apoptosis, as indicated by both caspase-3 activity and the Bcl-2/Bax ratio, than myometrial cells. Hypoxia further decreased apoptosis in myometrial cells with no further effect on leiomyoma cells. Treatment with DCA resulted in increased apoptosis in both types of cells, even in the presence of hypoxia.

CONCLUSION(S)

Shifting anaerobic to aerobic metabolism with the use of DCA resulted in an increase in apoptosis in leiomyoma cells and protected myometrial cells from the acquisition of the leiomyoma-like phenotype.

Updates of the role of oxidative stress in the pathogenesis of ovarian cancer

Clinical and epidemiological investigations have provided evidence supporting the role of reactive oxygen species (ROS) and reactive nitrogen species (RNS), collectively known as oxidative stress, in the etiology of cancer. Exogenous factors such as chronic inflammation, infection and hypoxia are major sources of cellular oxidative stress. Specifically, oxidative stress plays an important role in the pathogenesis, neoangiogenesis, and dissemination of local or distant ovarian cancer, as it is known to induce phenotypic modifications of tumor cells by cross talk between tumor cells and the surrounding stroma. Subsequently, the biological significance of the relationship between oxidative stress markers and various stages of epithelial ovarian cancer highlights potential therapeutic interventions as well as provides urgently needed early detection biomarkers. In the light of our scientific research and the most recent experimental and clinical observations, this review provides the reader with up to date most relevant findings on the role of oxidative stress in the pathogenesis of ovarian cancer and the possible therapeutic implications.

Specific point mutations in key redox enzymes are associated with chemoresistance in epithelial ovarian cancer

Oxidative stress plays an important role in the pathophysiology of ovarian cancer. Resistance to chemotherapy presents a significant challenge for ovarian cancer treatment. Specific single nucleotide polymorphisms (SNPs) in key redox enzymes have been associated with ovarian cancer survival and progression. The objective of this study was to determine whether chemotherapy induces point mutations in key redox enzymes that lead to the acquisition of chemoresistance in epithelial ovarian cancer (EOC). Human EOC cell lines and their chemoresistant counterpart were utilized for this study. Specific SNPs in key redox enzymes were analyzed by TaqMan SNP Genotyping. Activities and levels of key redox enzymes were determined by real-time RT-PCR, ELISA and a greiss assay. Point mutations in key redox enzymes were introduced into sensitive EOC cells via the CRISPR/Cas9 system. Cell viability and IC₅₀ for cisplatin were determined by the MTT Cell Proliferation Assay. Data was analyzed with SPSS using Student's two-tailed t-tests and One-way ANOVA followed by Dunnett's or Tukey's post hoc tests, p<0.05. Here, we demonstrate that chemoresistant EOC cells are characterized by a further enhancement in oxidative stress as compared to sensitive counterparts. Additionally, chemoresistant EOC cells manifested specific point mutations, which are associated with altered enzymatic activity, in key redox enzymes that are not detected in sensitive counterparts. Supplementation of an antioxidant was able to successfully sensitize EOC cells to chemotherapeutics. Causality was established by the induction of these point mutations in sensitive EOC cells, which resulted in a significant increase in the level of chemoresistance. These findings indicate that chemotherapy induces specific point mutations in key redox enzymes that contribute to the acquisition of chemoresistance in EOC cells, highlighting a potential novel mechanism. Identification of targets for chemoresistance with either biomarker and/or screening potential will have a significant impact for the treatment of this disease.

Long-term stabilization of stage 4 colon cancer using sodium dichloroacetate therapy

Oral dichloroacetate sodium (DCA) has been investigated as a novel metabolic therapy for various cancers since 2007, based on data from Bonnet et al that DCA can trigger apoptosis of human lung, breast and brain cancer cells. Response to therapy in human studies is measured by standard RECIST definitions, which define “response” by the degree of tumour reduction, or tumour disappearance on imaging. However, Blackburn et al have demonstrated that DCA can also act as a cytostatic agent in vitro and in vivo, without causing apoptosis (programmed cell death). A case is presented in which oral DCA therapy resulted in tumour stabilization of stage 4 colon cancer in a 57 years old female for a period of nearly 4 years, with no serious toxicity. Since the natural history of stage 4 colon cancer consists of steady progression leading to disability and death, this case highlights a novel use of DCA as a cytostatic agent with a potential to maintain long-term stability of advanced-stage cancer.

Dichloroacetate, a selective mitochondria-targeting drug for oral squamous cell carcinoma: a metabolic perspective of treatment

Reprogramming of metabolism is a well-established property of cancer cells that is receiving growing attention as potential therapeutic target. Oral squamous cell carcinomas (OSCC) are aggressive and drugs-resistant human tumours displaying wide metabolic heterogeneity depending on their malignant genotype and stage of development. Dichloroacetate (DCA) is a specific inhibitor of the PDH-regulator PDK proved to foster mitochondrial oxidation of pyruvate. In this study we tested comparatively the effects of DCA on three different OSCC-derived cell lines, HSC-2, HSC-3, PE15. Characterization of the three cell lines unveiled for HSC-2 and HSC-3 a glycolysis-reliant metabolism whereas PE15 accomplished an efficient mitochondrial oxidative phosphorylation. DCA treatment of the three OSCC cell lines, at pharmacological concentrations, resulted in stimulation of the respiratory activity and caused a remarkably distinctive pro-apoptotic/cytostatic effect on HSC-2 and HSC-3. This was accompanied with a large remodeling of the mitochondrial network, never documented before, leading to organelle fragmentation and with enhanced production of reactive oxygen species. The data here presented indicate that the therapeutic efficacy of DCA may depend on the specific metabolic profile adopted by the cancer cells with those exhibiting a deficient mitochondrial oxidative phosphorylation resulting more sensitive to the drug treatment.

A Single Nucleotide Polymorphism in Catalase Is Strongly Associated with Ovarian Cancer Survival

Ovarian cancer is the deadliest of all gynecologic cancers. Recent evidence demonstrates an association between enzymatic activity altering single nucleotide polymorphisms (SNP) with human cancer susceptibility. We sought to evaluate the association of SNPs in key oxidant and antioxidant enzymes with increased risk and survival in epithelial ovarian cancer. Individuals (n = 143) recruited were divided into controls, (n = 94): healthy volunteers, (n = 18), high-risk BRCA1/2 negative (n = 53), high-risk BRCA1/2 positive (n = 23) and ovarian cancer cases (n = 49). DNA was subjected to TaqMan SNP genotype analysis for selected oxidant and antioxidant enzymes. Of the seven selected SNP studied, no association with ovarian cancer risk (Pearson Chi-square) was found. However, a catalase SNP was identified as a predictor of ovarian cancer survival by the Cox regression model. The presence of this SNP was associated with a higher likelihood of death (hazard ratio (HR) of 3.68 (95% confidence interval (CI): 1.149–11.836)) for ovarian cancer patients. Kaplan-Meier survival analysis demonstrated a significant median overall survival difference (108 versus 60 months, p<0.05) for those without the catalase SNP as compared to those with the SNP. Additionally, age at diagnosis greater than the median was found to be a significant predictor of death (HR of 2.78 (95% CI: 1.022–7.578)). This study indicates a strong association with the catalase SNP and survival of ovarian cancer patients, and thus may serve as a prognosticator.

Pyruvate dehydrogenase kinase expression and metabolic changes following dichloroacetate exposure in anoxic human colorectal cancer cells

Dichloroacetate (DCA) is a small molecule that inhibits pyruvate dehydrogenase kinase (PDK) to constrain the aerobic glycolytic pathway observed in many cancer cells and effectively kill them with limited cytotoxicity on normal cells. We previously showed that DCA induced a cytoprotective effect in different human colorectal cancer (CRC) cell lines under anoxic conditions. In this study, we investigated the molecular and metabolic changes that may be providing this cytoprotection. The expression profiles of PDK isoforms in SW480 and LS174T cells along with subsequent changes in pyruvate dehydrogenase (PDH) phosphorylation were assessed following DCA exposure. Changes in mitochondrial activity and subsequent glucose consumption and lactate production were then examined. We show evidence of differential regulation in PDH phosphorylation between different human CRC cells leading to differences in mitochondrial activity following DCA exposure. However, these effects did not lead to significant changes in cellular metabolism nor growth. In conclusion, DCA may only be beneficial in treating a subset of tumor types based on their molecular profiles of different PDK isoforms.

Dichloroacetate and cancer: new home for an orphan drug?

We reviewed the anti-cancer effects of DCA, an orphan drug long used as an investigational treatment for various acquired and congenital disorders of mitochondrial intermediary metabolism. Inhibition by DCA of mitochondrial pyruvate dehydrogenase kinases and subsequent reactivation of the pyruvate dehydrogenase complex and oxidative phosphorylation is the common mechanism accounting for the drug's anti-neoplastic effects. At least two fundamental changes in tumor metabolism are induced by DCA that antagonize tumor growth, metastases and survival: the first is the redirection of glucose metabolism from glycolysis to oxidation (reversal of the Warburg effect), leading to inhibition of proliferation and induction of caspase-mediated apoptosis. These effects have been replicated in both human cancer cell lines and in tumor implants of diverse germ line origin. The second fundamental change is the oxidative removal of lactate, via pyruvate, and the co-incident buffering of hydrogen ions by dehydrogenases located in the mitochondrial matrix. Preclinical studies demonstrate that DCA has additive or synergistic effects when used in combination with standard agents designed to modify tumor oxidative stress, vascular remodeling, DNA integrity or immunity. These findings and limited clinical results suggest that potentially fruitful areas for additional clinical trials include 1) adult and pediatric high grade astrocytomas; 2) BRAF-mutant cancers, such as melanoma, perhaps combined with other pro-oxidants; 3) tumors in which resistance to standard platinum-class drugs alone may be overcome with combination therapy; and 4) tumors of endodermal origin, in which extensive experimental research has demonstrated significant anti-proliferative, pro-apoptotic effects of DCA, leading to improved host survival.

Dichloroacetate should be considered with platinum-based chemotherapy in hypoxic tumors rather than as a single agent in advanced non-small cell lung cancer

OBJECTIVES

Dichloroacetate (DCA) is a highly bioavailable small molecule that inhibits pyruvate dehydrogenase kinase, promoting glucose oxidation and reversing the glycolytic phenotype in preclinical cancer studies. We designed this open-label phase II trial to determine the response rate, safety, and tolerability of oral DCA in patients with metastatic breast cancer and advanced stage non-small cell lung cancer (NSCLC).

MATERIALS AND METHODS

This trial was conducted with DCA 6.25 mg/kg orally twice daily in previously treated stage IIIB/IV NSCLC or stage IV breast cancer. Growth inhibition by DCA was also evaluated in a panel of 54 NSCLC cell lines with and without cytotoxic chemotherapeutics (cisplatin and docetaxel) in normoxic and hypoxic conditions.

RESULTS AND CONCLUSIONS

Under normoxic conditions in vitro, single-agent IC50 was >2 mM for all evaluated cell lines. Synergy with cisplatin was seen in some cell lines under hypoxic conditions. In the clinical trial, after seven patients were enrolled, the study was closed based on safety concerns. The only breast cancer patient had stable disease after 8 weeks, quickly followed by progression in the brain. Two patients withdrew consent within a week of enrollment. Two patients had disease progression prior to the first scheduled scans. Within 1 week of initiating DCA, one patient died suddenly of unknown cause and one experienced a fatal pulmonary embolism. We conclude that patients with previously treated advanced NSCLC did not benefit from oral DCA. In the absence of a larger controlled trial, firm conclusions regarding the association between these adverse events and DCA are unclear. Further development of DCA should be in patients with longer life expectancy, in whom sustained therapeutic levels can be achieved, and potentially in combination with cisplatin.

Dichloroacetate improves immune dysfunction caused by tumor-secreted lactic acid and increases antitumor immunoreactivity

The activation of oncogenic signaling pathways induces the reprogramming of glucose metabolism in tumor cells and increases lactic acid secretion into the tumor microenvironment. This is a well-known characteristic of tumor cells, termed the Warburg effect, and is a candidate target for antitumor therapy. Previous reports show that lactic acid secreted by tumor cells is a proinflammatory mediator that activates the IL-23/IL-17 pathway, thereby inducing inflammation, angiogenesis and tissue remodeling. Here, we show that lactic acid, or more specifically the acidification it causes, increases arginase I (ARG1) expression in macrophages to inhibit T-cell proliferation and activation. Accordingly, we hypothesized that counteraction of the immune effects by lactic acid might suppress tumor development. We show that dichloroacetate (DCA), an inhibitor of pyruvate dehydrogenase kinases, targets macrophages to suppress activation of the IL-23/IL-17 pathway and the expression of ARG1 by lactic acid. Furthermore, lactic acid-pretreated macrophages inhibited CD8+ T-cell proliferation, but CD8+ T-cell proliferation was restored when macrophages were pretreated with lactic acid and DCA. DCA treatment decreased ARG1 expression in tumor-infiltrating immune cells and increased the number of IFN-γ-producing CD8+ T cells and NK cells in tumor-bearing mouse spleen. Although DCA treatment alone did not suppress tumor growth, it increased antitumor immunotherapeutic activity of Poly(IC) in both CD8+ T cell- and NK cell-sensitive tumor models. Therefore, DCA acts not only on tumor cells to suppress glycolysis but also on immune cells to improve the immune status modulated by lactic acid and to increase the effectiveness of antitumor immunotherapy.

Mitochondrial activation by inhibition of PDKII suppresses HIF1a signaling and angiogenesis in cancer

Most solid tumors are characterized by a metabolic shift from glucose oxidation to glycolysis, in part due to actively suppressed mitochondrial function, a state that favors resistance to apoptosis. Suppressed mitochondrial function may also contribute to the activation of hypoxia-inducible factor 1α (HIF1α) and angiogenesis. We have previously shown that the inhibitor of pyruvate dehydrogenase kinase (PDK) dichloroacetate (DCA) activates glucose oxidation and induces apoptosis in cancer cells in vitro and in vivo. We hypothesized that DCA will also reverse the 'pseudohypoxic' mitochondrial signals that lead to HIF1α activation in cancer, even in the absence of hypoxia and inhibit cancer angiogenesis. We show that inhibition of PDKII inhibits HIF1α in cancer cells using several techniques, including HIF1α luciferase reporter assays. Using pharmacologic and molecular approaches that suppress the prolyl-hydroxylase (PHD)-mediated inhibition of HIF1α, we show that DCA inhibits HIF1α by both a PHD-dependent mechanism (that involves a DCA-induced increase in the production of mitochondria-derived α-ketoglutarate) and a PHD-independent mechanism, involving activation of p53 via mitochondrial-derived H(2)O(2), as well as activation of GSK3β. Effective inhibition of HIF1α is shown by a decrease in the expression of several HIF1α regulated gene products as well as inhibition of angiogenesis in vitro in matrigel assays. More importantly, in rat xenotransplant models of non-small cell lung cancer and breast cancer, we show effective inhibition of angiogenesis and tumor perfusion in vivo, assessed by contrast-enhanced ultrasonography, nuclear imaging techniques and histology. This work suggests that mitochondria-targeting metabolic modulators that increase pyruvate dehydrogenase activity, in addition to the recently described pro-apoptotic and anti-proliferative effects, suppress angiogenesis as well, normalizing the pseudo-hypoxic signals that lead to normoxic HIF1α activation in solid tumors.