Dichloroacetate metabolically targeted therapy defeats cytotoxicity of standard anticancer drugs

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.

Beyond the Warburg Effect: Oxidative and Glycolytic Phenotypes Coexist within the Metabolic Heterogeneity of Glioblastoma

Glioblastoma (GBM) is the most aggressive primary brain tumor, with a median survival at diagnosis of 16-20 months. Metabolism represents a new attractive therapeutic target; however, due to high intratumoral heterogeneity, the application of metabolic drugs in GBM is challenging. We characterized the basal bioenergetic metabolism and antiproliferative potential of metformin (MF), dichloroacetate (DCA), sodium oxamate (SOD) and diazo-5-oxo-L-norleucine (DON) in three distinct glioma stem cells (GSCs) (GBM18, GBM27, GBM38), as well as U87MG. GBM27, a highly oxidative cell line, was the most resistant to all treatments, except DON. GBM18 and GBM38, Warburg-like GSCs, were sensitive to MF and DCA, respectively. Resistance to DON was not correlated with basal metabolic phenotypes. In combinatory experiments, radiomimetic bleomycin exhibited therapeutically relevant synergistic effects with MF, DCA and DON in GBM27 and DON in all other cell lines. MF and DCA shifted the metabolism of treated cells towards glycolysis or oxidation, respectively. DON consistently decreased total ATP production. Our study highlights the need for a better characterization of GBM from a metabolic perspective. Metabolic therapy should focus on both glycolytic and oxidative subpopulations of GSCs.

The Importance of Gender-Related Anticancer Research on Mitochondrial Regulator Sodium Dichloroacetate in Preclinical Studies In Vivo

Sodium dichloroacetate (DCA) is an investigational medicinal product which has a potential anticancer preparation as a metabolic regulator in cancer cells’ mitochondria. Inhibition of pyruvate dehydrogenase kinases by DCA keeps the pyruvate dehydrogenase complex in the active form, resulting in decreased lactic acid in the tumor microenvironment. This literature review displays the preclinical research data on DCA’s effects on the cell pyruvate dehydrogenase deficiency, pyruvate mitochondrial oxidative phosphorylation, reactive oxygen species generation, and the Na⁺–K⁺–2Cl⁻ cotransporter expression regulation in relation to gender. It presents DCA pharmacokinetics and the hepatocarcinogenic effect, and the safety data covers the DCA monotherapy efficacy for various human cancer xenografts in vivo in male and female animals. Preclinical cancer researchers report the synergistic effects of DCA combined with different drugs on cancer by reversing resistance to chemotherapy and promoting cell apoptosis. Researchers note that female and male animals differ in the mechanisms of cancerogenesis but often ignore studying DCA’s effects in relation to gender. Preclinical gender-related differences in DCA pharmacology, pharmacological mechanisms, and the elucidation of treatment efficacy in gonad hormone dependency could be relevant for individualized therapy approaches so that gender-related differences in treatment response and safety can be proposed.

Surface-Functionalization of Zr-Fumarate MOF for Selective Cytotoxicity and Immune System Compatibility in Nanoscale Drug Delivery

Metal-organic frameworks (MOFs), network structures wherein metal ions or clusters link organic ligands into porous materials, are being actively researched as nanoscale drug delivery devices as they offer tunable structures with high cargo loading that can easily be further functionalized for targeting and enhanced physiological stability. The excellent biocompatibility of Zr has meant that its MOFs are among the most studied to date, in particular the archetypal Zr terephthalate UiO-66. In contrast, the isoreticular analog linked by fumarate (Zr-fum) has received little attention, despite the endogenous linker being part of the Krebs cycle. Herein, we report a comprehensive study of Zr-fum in the context of drug delivery. Reducing particle size is shown to increase uptake by cancer cells while reducing internalization by macrophages, immune system cells that remove foreign objects from the bloodstream. Zr-fum is compatible with defect loading of the drug dichloroacetate (DCA) as well as surface modification during synthesis, through coordination modulation and postsynthetically. DCA-loaded, PEGylated Zr-fum shows selective in vitro cytotoxicity toward HeLa and MCF-7 cancer cells, likely as a consequence of its enhanced caveolae-mediated endocytosis compared to uncoated precursors, and it is well tolerated by HEK293 kidney cells, J774 macrophages, and human peripheral blood lymphocytes. Compared to UiO-66, Zr-fum is more efficient at transporting the drug mimic calcein into HeLa cells, and DCA-loaded, PEGylated Zr-fum is more effective at reducing HeLa and MCF-7 cell proliferation than the analogous UiO-66 sample. In vitro examination of immune system response shows that Zr-fum samples induce less reactive oxygen species than UiO-66 analogs, possibly as a consequence of the linker being endogenous, and do not activate the C3 and C4 complement cascade pathways, suggesting that Zr-fum can avoid phagocytic activation. The results show that Zr-fum is an attractive alternative to UiO-66 for nanoscale drug delivery, and that a wide range of in vitro experiments is available to greatly inform the design of drug delivery systems prior to early stage animal studies.

Bioenergetic modulators hamper cancer cell viability and enhance response to chemotherapy

Gliomas are characterized by a marked glycolytic metabolism with a consequent production of massive amounts of lactate, even in the presence of normal levels of oxygen, associated to increased invasion capacity and to higher resistance to conventional treatment. This work aimed to understand how the metabolic modulation can influence tumour aggressive features and its potential to be used as complementary therapy. We assessed the effect of bioenergetic modulators (BMs) targeting different metabolic pathways in glioma cell characteristics. The in vivo effect of BMs was evaluated using the chicken chorioallantoic membrane model. Additionally, the effect of pre-treatment with BMs in the response to the antitumour drug temozolomide (TMZ) was analysed in vitro. Cell treatment with the BMs induced a decrease in cell viability and in migratory/invasion abilities, as well as modifications in metabolic parameters (glucose, lactate and ATP) and increased the cytotoxicity of the conventional drug TMZ. Furthermore, all BMs decreased the tumour growth and the number of blood vessels in an in vivo model. Our results demonstrate that metabolic modulation has the potential to be used as therapy to decrease the aggressiveness of the tumours or to be combined with conventional drugs used in glioma treatment.

Doxorubicin triggers bioenergetic failure and p53 activation in mouse stem cell-derived cardiomyocytes

Doxorubicin (DOX) is a widely used anticancer drug that could be even more effective if its clinical dosage was not limited because of delayed cardiotoxicity. Beating stem cell-derived cardiomyocytes are a preferred in vitro model to further uncover the mechanisms of DOX-induced cardiotoxicity. Our objective was to use cultured induced-pluripotent stem cell(iPSC)-derived mouse cardiomyocytes (Cor.At) to investigate the effects of DOX on cell and mitochondrial metabolism, as well as on stress responses. Non-proliferating and beating Cor.At cells were treated with 0.5 or 1 μM DOX for 24 h, and morphological, functional and biochemical changes associated with mitochondrial bioenergetics, DNA-damage response and apoptosis were measured. Both DOX concentrations decreased ATP levels and SOD2 protein levels and induced p53-dependent caspase activation. However, differential effects were observed for the two DOX concentrations. The highest concentration induced a high degree of apoptosis, with increased nuclear apoptotic morphology, PARP-1 cleavage and decrease of some OXPHOS protein subunits. At the lowest concentration, DOX increased the expression of p53 target transcripts associated with mitochondria-dependent apoptosis and decreased transcripts related with DNA-damage response and glycolysis. Interestingly, cells treated with 0.5 μM DOX presented an increase in PDK4 transcript levels, accompanied by an increase in phospho-PDH and decreased PDH activity. This was accompanied by an apparent decrease in basal and maximal oxygen consumption rates (OCR) and in basal extracellular acidification rate (ECAR). Cells pre-treated with the PDK inhibitor dichloroacetate (DCA), with the aim of restoring PDH activity, partially recovered OCR and ECAR. The results suggest that the higher DOX concentration mainly induces p53-dependent apoptosis, whereas for the lower DOX concentration the cardiotoxic effects involve bioenergetic failure, unveiling PDH as a possible therapeutic target to decrease DOX cardiotoxicity.

Enhancing anticancer cytotoxicity through bimodal drug delivery from ultrasmall Zr MOF nanoparticles

Dual delivery of dichloroacetate and 5-fluorouracil from Zr MOFs into cancer cells is found to enhance in vitro cytotoxicity.

Therapeutic Targeting of the Pyruvate Dehydrogenase Complex/Pyruvate Dehydrogenase Kinase (PDC/PDK) Axis in Cancer

The mitochondrial pyruvate dehydrogenase complex (PDC) irreversibly decarboxylates pyruvate to acetyl coenzyme A, thereby linking glycolysis to the tricarboxylic acid cycle and defining a critical step in cellular bioenergetics. Inhibition of PDC activity by pyruvate dehydrogenase kinase (PDK)-mediated phosphorylation has been associated with the pathobiology of many disorders of metabolic integration, including cancer. Consequently, the PDC/PDK axis has long been a therapeutic target. The most common underlying mechanism accounting for PDC inhibition in these conditions is post-transcriptional upregulation of one or more PDK isoforms, leading to phosphorylation of the E1α subunit of PDC. Such perturbations of the PDC/PDK axis induce a "glycolytic shift," whereby affected cells favor adenosine triphosphate production by glycolysis over mitochondrial oxidative phosphorylation and cellular proliferation over cellular quiescence. Dichloroacetate is the prototypic xenobiotic inhibitor of PDK, thereby maintaining PDC in its unphosphorylated, catalytically active form. However, recent interest in the therapeutic targeting of the PDC/PDK axis for the treatment of cancer has yielded a new generation of small molecule PDK inhibitors. Ongoing investigations of the central role of PDC in cellular energy metabolism and its regulation by pharmacological effectors of PDKs promise to open multiple exciting vistas into the biochemical understanding and treatment of cancer and other diseases.

Targeting Cancer Metabolism - Revisiting the Warburg Effects

After more than half of century since the Warburg effect was described, this atypical metabolism has been standing true for almost every type of cancer, exhibiting higher glycolysis and lactate metabolism and defective mitochondrial ATP production. This phenomenon had attracted many scientists to the problem of elucidating the mechanism of, and reason for, this effect. Several models based on oncogenic studies have been proposed, such as the accumulation of mitochondrial gene mutations, the switch from oxidative phosphorylation respiration to glycolysis, the enhancement of lactate metabolism, and the alteration of glycolytic genes. Whether the Warburg phenomenon is the consequence of genetic dysregulation in cancer or the cause of cancer remains unknown. Moreover, the exact reasons and physiological values of this peculiar metabolism in cancer remain unclear. Although there are some pharmacological compounds, such as 2-deoxy-D-glucose, dichloroacetic acid, and 3-bromopyruvate, therapeutic strategies, including diet, have been developed based on targeting the Warburg effect. In this review, we will revisit the Warburg effect to determine how much scientists currently understand about this phenomenon and how we can treat the cancer based on targeting metabolism.

The presence of wild type p53 in hematological cancers improves the efficacy of combinational therapy targeting metabolism

Manipulation of metabolic pathways in hematological cancers has therapeutic potential. Here, we determined the molecular mechanism of action of the metabolic modulator dichloroacetate (DCA) in leukemic cells. We found that DCA induces the AMP-activated protein kinase (AMPK)/p53 pathway with increased efficacy in tumors expressing wild type (wt p53). Clinically relevant, low concentrations of doxorubicin synergize in vitro and in vivo with DCA to further enhance p53 activation and to block tumor progression. Leukemia cell lines and primary leukemic cells containing mutant p53 are resistant to the above-described combination approach. However, DCA synergized with the Hsp90 inhibitor 17-AAG to specifically eliminate these cells. Our studies strongly indicate that depending on the p53 status, different combination therapies would provide better treatment with decreased side effects in hematological cancers.

Dichloroacetate alters Warburg metabolism, inhibits cell growth, and increases the X-ray sensitivity of human A549 and H1299 NSC lung cancer cells

We investigated whether altering Warburg metabolism (aerobic glycolysis) by treatment with the metabolic agent dichloroacetate (DCA) could increase the X-ray-induced cell killing of the radiation-resistant human non-small-cell lung cancer (NSCLC) cell lines A549 and H1299. Treatment with 50mM DCA decreased lactate production and glucose consumption in both A549 and H1299, clear indications of attenuated aerobic glycolysis. In addition, we found that DCA treatment also slowed cell growth, increased population-doubling time, and altered cell cycle distribution. Furthermore, we report that treatment with 50mM DCA significantly increased single and fractionated X-ray-induced cell killing of A549 and H1299 cells. Assay of DNA double-strand break repair by neutral comet assays demonstrated that DCA inhibited both the fast and the slow kinetics of X-ray-induced DSB repair in both A549 and H1299 NSCL cancer cells. Taken together the data suggest a correlation between an attenuated aerobic glycolysis and enhanced cytotoxicity and radiation-induced cell killing in radiation-resistant NSCLC cells.

Activation of mitochondrial oxidation by PDK2 inhibition reverses cisplatin resistance in head and neck cancer

Dichloroacetate (DCA), an orphan drug that promotes a shift from glycolysis to oxidative phosphorylation, has been repurposed for cancer therapy. The present study investigated whether DCA may overcome cisplatin resistance in head and neck cancer (HNC). Two cisplatin-resistant HNC cell lines (AMC-HN4R and -HN9R), their parental lines, and other human HNC lines were used. The effect of DCA, alone and in combination with cisplatin, was assessed by measuring cell cycle, viability, death, reactive oxygen species (ROS) production, mitochondrial membrane potential (ΔΨm), and protein expression in preclinical mouse tumor xenograft models. Increased glycolysis correlated with decreased sensitivity to cisplatin and was reduced by DCA. Cisplatin-resistant cells overexpressed pyruvate dehydrogenase kinase 2 (PDK2). DCA induced HNC cell death by decreasing ΔΨm and promoting mitochondrial ROS production. This effect was decreased by the antioxidant N-acetyl-l-cysteine or by inhibition of caspase-mediated apoptosis. Activation of mitochondrial glucose oxidation by DCA eventually activated downstream mitochondrial apoptotic signaling, leading to the death of chemoresistant cancer cells. Therefore, DCA significantly sensitized resistant HNC cells to cisplatin in vitro and in vivo. High glycolysis and PDK2 overexpression are closely linked to cisplatin resistance in HNC cells; the latter can be overcome by DCA.

VER-246608, a novel pan-isoform ATP competitive inhibitor of pyruvate dehydrogenase kinase, disrupts Warburg metabolism and induces context-dependent cytostasis in cancer cells

Pyruvate dehydrogenase kinase (PDK) is a pivotal enzyme in cellular energy metabolism that has previously been implicated in cancer through both RNAi based studies and clinical correlations with poor prognosis in several cancer types.

Here, we report the discovery of a novel and selective ATP competitive pan-isoform inhibitor of PDK, VER-246608. Consistent with a PDK mediated MOA, VER-246608 increased pyruvate dehydrogenase complex (PDC) activity, oxygen consumption and attenuated glycolytic activity. However, these effects were only observed under D-glucose-depleted conditions and required almost complete ablation of PDC E1α subunit phosphorylation. VER-246608 was weakly anti-proliferative to cancer cells in standard culture media; however, depletion of either serum or combined D-glucose/L-glutamine resulted in enhanced cellular potency. Furthermore, this condition-selective cytostatic effect correlated with reduced intracellular pyruvate levels and an attenuated compensatory response involving deamination of L-alanine. In addition, VER-246608 was found to potentiate the activity of doxorubicin. In contrast, the lipoamide site inhibitor, Nov3r, demonstrated sub-maximal inhibition of PDK activity and no evidence of cellular activity.

These studies suggest that PDK inhibition may be effective under the nutrient-depleted conditions found in the tumour microenvironment and that combination treatments should be explored to reveal the full potential of this therapeutic strategy.

Targeting of two aspects of metabolism in breast cancer treatment

Deregulated metabolism is gaining recognition as a hallmark of cancer cells, and is being explored for therapeutic potential. The Warburg effect is a metabolic phenotype that occurs in 90% of tumors, where glycolysis is favored despite the presence of oxygen. Dichloroacetate (DCA) is a pyruvate dehydrogenase kinase (PDK) inhibitor that can reverse the Warburg effect. PENAO (4-(N-(S-penicillaminylacetyl)amino) phenylarsonous acid) is a novel anti-mitochondrial agent that targets the adenine nucleotide transporter in mitochondria and is currently in clinical trials for solid tumors. We have investigated the targeting of two aspects of metabolism, using DCA to promote mitochondrial activity combined with PENAO to inhibit mitochondrial activity, in breast and other carcinoma cell lines. PENAO was effective at low uM concentrations in luminal (T-47D) and triple negative (MDA-MB-231) breast cancer cells, in normoxia and hypoxia. The cytotoxicity of PENAO was enhanced by DCA by a mechanism involving increased reactive oxygen species in both T-47D and MDA-MB-231 cells, however further investigations found it did not always involve PDK2 inhibition or reduction of the mitochondrial membrane potential, which are the accepted mechanisms for DCA induction of apoptosis. Nevertheless, DCA sensitized all cancer cell lines tested toward apoptosis of PENAO. DCA and PENAO are both currently in clinical trials and targeting cancer metabolism with these drugs may offer options for difficult to treat cancers.

Dichloroacetate restores drug sensitivity in paclitaxel-resistant cells by inducing citric acid accumulation

BACKGROUND

The Warburg effect describes the increased reliance of tumor cells on glycolysis for ATP generation. Mitochondrial respiratory defect is thought to be an important factor leading to the Warburg effect in some types of tumor cells. Consequently, there is growing interest in developing anti-cancer drugs that target mitochondria. One example is dichloroacetate (DCA) that stimulates mitochondria through inhibition of pyruvate dehydrogenase kinase.

METHODS

We investigated the anti-cancer activity of DCA using biochemical and isotopic tracing methods.

RESULTS

We observed that paclitaxel-resistant cells contained decreased levels of citric acid and sustained mitochondrial respiratory defect. DCA specifically acted on cells with mitochondrial respiratory defect to reverse paclitaxel resistance. DCA could not effectively activate oxidative respiration in drug-resistant cells, but induced higher levels of citrate accumulation, which led to inhibition of glycolysis and inactivation of P-glycoprotein.

CONCLUSIONS

The abilityof DCA to target cells with mitochondrial respiratory defect and restore paclitaxel sensitivity by inducing citrate accumulation supports further preclinical development.

Polycomb-dependent repression of the potassium channel-encoding gene KCNA5 promotes cancer cell survival under conditions of stress

Relapse after clinical remission remains a leading cause of cancer-associated death. Although the mechanisms of tumor relapse are complex, the ability of cancer cells to survive physiological stress is a prerequisite for recurrence. Ewing sarcoma (ES) and neuroblastoma (NB) are aggressive cancers that frequently relapse after initial remission. In addition, both tumors overexpress the polycomb group (PcG) proteins BMI-1 and EZH2, which contribute to tumorigenicity. We have discovered that ES and NB resist hypoxic stress-induced death and that survival depends on PcG function. Epigenetic repression of developmental programs is the most well-established cancer-associated function of PcG proteins. However, we noted that voltage-gated potassium (Kv) channel genes are also targets of PcG regulation in stem cells. Given the role of potassium in regulating apoptosis, we reasoned that repression of Kv channel genes might have a role in cancer cell survival. Here we describe our novel finding that PcG-dependent repression of the Kv1.5 channel gene KCNA5 contributes to cancer cell survival under conditions of stress. We show that survival of cancer cells in stress is dependent upon suppression of Kv1.5 channel function. The KCNA5 promoter is marked in cancer cells with PcG-dependent chromatin repressive modifications that increase in hypoxia. Genetic and pharmacological inhibition of BMI-1 and EZH2, respectively, restore KCNA5 expression, which sensitizes cells to stress-induced death. In addition, ectopic expression of the Kv1.5 channel induces apoptotic cell death under conditions of hypoxia. These findings identify a novel role for PcG proteins in promoting cancer cell survival via repression of KCNA5.

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 modulates cytokines toward T helper 1 function via induction of the interleukin-12-interferon-γ pathway

BACKGROUND

Dichloroacetate (DCA) is one of the new, promising anticancer drugs. DCA restores normal mitochondrial function and enables cancer cells to undergo apoptosis. In addition, DCA was found to modulate certain signaling pathways involving some transcription factors. The latter encouraged us to study DCA immunomodulatory activity on cytokines and their association with increasing DCA cancer cell cytotoxicity.

METHODS AND RESULTS

Cell viability assay was used to determine the effect of different concentrations of DCA on the survival of 3-methylcholanthrene (MCA) fibrosarcoma cell line. DCA decreased the percent survival of MCA fibrosarcoma in a dose-dependent manner (P<0.01). Furthermore, this percent survival was further reduced when MCA fibrosarcoma cells were cocultured with mouse splenocytes. The latter was observed at 10 mM DCA (P<0.01), and the inhibitory concentration at 50% dropped from 23 mM to 15.6 mM DCA (P<0.05). In addition, DCA significantly enhanced interferon (IFN)-γ but not interleukin (IL)-17 production levels in unstimulated and stimulated mouse spleen cells. To investigate the mechanism of DCA on IFN-γ production, DCA cytokine modulatory effect was tested on unstimulated macrophages, T-cells, and natural killer cells. DCA significantly increased IL-12 production from macrophages but did not modulate the production of IFN-γ from either T-cells or natural killer cells. Moreover, the DCA-enhancing effect on IFN-γ production was reversed by anti-IL-12 antibody. Also, the DCA cytokine modulatory effect was tested in vivo after inducing mouse skin inflammation using phorbol 12-myristate 13-acetate (PMA). DCA restored PMA-lowered IFN-γ and IL-12 levels and normalized PMA-increased transforming growth factor-β level, but it inhibited IL-10 levels even further (P<0.05).

CONCLUSION

DCA has immunomodulatory activity, mainly via activation of the IL-12-IFN-γ pathway and is able to modulate cytokines toward T helper 1 lymphocyte function. These DCA immunomodulatory effects are promising and further investigations are required to develop protocols for its use in cancer treatment.

DCA increases the antitumor effects of capecitabine in a mouse B16 melanoma allograft and a human non-small cell lung cancer A549 xenograft

PURPOSE

Capecitabine is one of the few chemotherapy drugs with high oral availability. Recently, sodium dichloroacetate (DCA) has shown great potential as an anticancer agent. In the present study, we assessed the anticancer effect of DCA in combination with capecitabine for cancers that modestly expressed TP.

METHODS

A mouse B16 melanoma allograft and a human non-small cell lung cancer A549 xenograft were used to assess the effect of DCA and capecitabine combined treatment. Histology and immunohistochemistry were used to detect the apoptosis and proliferation of cancer cells. Real-time PCR and Western blot were carried out to detect the expression of TP and caspases, respectively.

RESULTS

For the first time, we report that DCA increased the antitumor effects of capecitabine in a mouse B16 allograft and a human A549 xenograft by promoting apoptosis of tumor cells. DCA has little effect on the expression of TP.

CONCLUSIONS

Our finding suggests that DCA in combination with capecitabine might be potential as a new therapeutic regimen against some cancers.

Stalling the engine of resistance: targeting cancer metabolism to overcome therapeutic resistance

Cancer cells are markedly different from normal cells with regards to how their metabolic pathways are used to fuel cellular growth and survival. Two basic metabolites that exemplify these differences through increased uptake and altered metabolic usage are glucose and glutamine. These molecules can be catabolized to manufacture many of the building blocks required for active cell growth and proliferation. The alterations in the metabolic pathways necessary to sustain this growth have been linked to therapeutic resistance, a trait that is correlated with poor patient outcomes. By targeting the metabolic pathways that import, catabolize, and synthesize essential cellular components, drug-resistant cancer cells can often be resensitized to anticancer treatments. The specificity and efficacy of agents directed at the unique aspects of cancer metabolism are expected to be high; and may, when in used in combination with more traditional therapeutics, present a pathway to surmount resistance within tumors that no longer respond to current forms of treatment.

Dichloroacetate inhibits aerobic glycolysis in multiple myeloma cells and increases sensitivity to bortezomib

Background:

Dichloroacetate (DCA), through the inhibition of aerobic glycolysis (the ‘Warburg effect') and promotion of pyruvate oxidation, induces growth reduction in many tumours and is now undergoing several clinical trials. If aerobic glycolysis is active in multiple myeloma (MM) cells, it can be potentially targeted by DCA to induce myeloma growth inhibition.

Methods:

Representative multiple myeloma cell lines and a myeloma-bearing mice were treated with DCA, alone and in combination with bortezomib.

Results:

We found that aerobic glycolysis occurs in approximately half of MM cell lines examined, producing on average 1.86-fold more lactate than phorbol myristate acetate stimulated-peripheral blood mononuclear cells and is associated with low-oxidative capacity. Lower doses of DCA (5–10 mℳ) suppressed aerobic glycolysis and improved cellular respiration that was associated with activation of the pyruvate dehydrogenase complex. Higher doses of DCA (10–25 mℳ) induced superoxide production, apoptosis, suppressed proliferation with a G_0/1 and G₂M phase arrest in MM cell lines. In addition, DCA increased MM cell line sensitivity to bortezomib, and combinatorial treatment of both agents improved the survival of myeloma-bearing mice.

Conclusion:

Myeloma cells display aerobic glycolysis and DCA may complement clinically used MM therapies to inhibit disease progression.

In vitro and in vivo anticancer activity of aconitine on melanoma cell line B16

The anti-tumor effect of aconitine in melanoma cell line B16 has been studied in this paper. We found that B16 cells showed significantly reduced growth rates and increased apoptotic effects in the presence of aconitine. Furthermore, aconitine inhibited the PI3K/AKT and MAPK/ERK1/2 signaling pathways, thus regulating the levels of protein and mRNA of PCNA and apoptotic related signaling molecules. Above all, we found that aconitine showed an anti-melanoma effect in suppressing tumor growth in vivo. In conclusion, we show that aconitine may be a useful anticancer drug in the future.

Combination of sulindac and dichloroacetate kills cancer cells via oxidative damage

Sulindac is an FDA-approved non-steroidal anti-inflammatory drug with documented anticancer activities. Our recent studies showed that sulindac selectively enhanced the killing of cancer cells exposed to oxidizing agents via production of reactive oxygen species (ROS) resulting in mitochondrial dysfunction. This effect of sulindac and oxidative stress on cancer cells could be related to the defect in respiration in cancer cells, first described by Warburg 50 years ago, known as the Warburg effect. We postulated that sulindac might enhance the selective killing of cancer cells when combined with any compound that alters mitochondrial respiration. To test this hypothesis we have used dichloroacetate (DCA), which is known to shift pyruvate metabolism away from lactic acid formation to respiration. One might expect that DCA, since it stimulates aerobic metabolism, could stress mitochondrial respiration in cancer cells, which would result in enhanced killing in the presence of sulindac. In this study, we have shown that the combination of sulindac and DCA enhances the selective killing of A549 and SCC25 cancer cells under the conditions used. As predicted, the mechanism of killing involves ROS production, mitochondrial dysfunction, JNK signaling and death by apoptosis. Our results suggest that the sulindac-DCA drug combination may provide an effective cancer therapy.

From tumor cell metabolism to tumor immune escape

Tumorigenesis implies adaptation of tumor cells to an adverse environment. First, developing tumors must acquire nutrients to ensure their rapid growth. Second, they must escape the attack from the host immune system. Recent studies suggest that these phenomena could be related and that tumor cell metabolism may propel tumor immune escape. Tumor cell metabolism tends to avoid mitochondrial activity and oxidative phosphorylation (OXPHOS), and largely relies on glycolysis to produce energy. This specific metabolism helps tumor cells to avoid the immune attack from the host by blocking or avoiding the immune attack. By changing their metabolism, tumor cells produce or sequester a variety of amino acids, lipids and chemical compounds that directly alter immune function therefore promoting immune evasion. A second group of metabolism-related modification targets the major histocompatibility complex-I (MHC-I) and related molecules. Tumor MHC-I presents tumor-associated antigens (TAAs) to cytotoxic T-cells (CTLs) and hence, sensitizes cancer cells to the cytolytic actions of the anti-tumor adaptive immune response. Blocking tumor mitochondrial activity decreases expression of MHC-I molecules at the tumor cell surface. And peroxynitrite (PNT), produced by tumor-infiltrating myeloid cells, chemically modifies MHC-I avoiding TAA expression in the plasma membrane. These evidences on the role of tumor cell metabolism on tumor immune escape open the possibility of combining drugs designed to control tumor cell metabolism with new procedures of anti-tumor immunotherapy. This article is part of a Directed Issue entitled: Bioenergetic dysfunction, adaptation and therapy.

Mitochondrial remodeling in cancer metabolism and survival: potential for new therapies

Mitochondria are semi-autonomous organelles that play essential roles in cellular metabolism and programmed cell death pathways. Genomic, functional and structural mitochondrial alterations have been associated with cancer. Some of those alterations may provide a selective advantage to cells, allowing them to survive and grow under stresses created by oncogenesis. Due to the specific alterations that occur in cancer cell mitochondria, these organelles may provide promising targets for cancer therapy. The development of drugs that specifically target metabolic and mitochondrial alterations in tumor cells has become a matter of interest in recent years, with several molecules undergoing clinical trials. This review focuses on the most relevant mitochondrial alterations found in tumor cells, their contribution to cancer progression and survival, and potential usefulness for stratification and therapy.

Mitaplatin increases sensitivity of tumor cells to cisplatin by inducing mitochondrial dysfunction

Tumor resistance to chemotherapy is the major obstacle to employ cisplatin, one of the broadly used chemotherapeutic drugs, for effective treatment of various tumors in the clinic. Most acknowledged mechanisms of cancer resistance to cisplatin focus on increased nuclear DNA repair or detoxicity of cisplatin. We previously demonstrated that there was a unique metabolic profile in cisplatin-resistant (CP-r) human epidermoid adenocarcinoma KB-CP 20 and hepatoma BEL 7404-CP 20 cancer cells. In this study, we further defined hyperpolarized mitochondrial membrane potentials (Δψ(m)) in CP-r KB-CP 20 and BEL 7404-CP 20 cells compared to the cisplatin-sensitive (CP-s) KB-3-1 and BEL 7404 cells. Based on the mitochondrial dysfunction, mitaplatin was designed with two mitochondrial-targeting moieties [dichloroacetate (DCA) units] to the axial positions of a six-coordinate Pt(IV) center to sensitize cisplatin resistance. It was found that mitaplatin induced more apoptosis in CP-r KB-CP 20 and BEL 7404-CP 20 cells than that of cisplatin, DCA and cisplatin/DCA compared on an equal molar basis. There was more platinum accumulation in mitaplatin-treated CP-r cells due to enhanced transmembrane permeability of lipophilicity, and mitaplatin also showed special targeting to mitochondria. Moreover, in the case of treatment with mitaplatin, the dramatic collapse of Δψ(m) was shown in a dose-dependent manner, which was confirmed by FACS and confocal microscopic measurements. Reduced glucose utilization of CP-r cells was detected with specifically inhibited phosphorylation of pyruvate dehydrogenase (PDH) at Ser-232, Ser-293, and Ser-300 of the E1α subunit when treated with mitaplatin, which was indicated to modulate the abnormal glycolysis of resistant cells. The present study suggested novel mitochondrial mechanism of mitaplatin circumventing cisplatin resistance toward CP-r cells as a carrier across membrane to produce CP-like cytotoxicity and DCA-like mitochondria-dependent apoptosis. Therefore, mitochondria targeting compounds would be more vulnerable and selective to overcome cisplatin resistance due to the unique metabolic properties of CP-r cancer cells.

Dichloroacetate inhibits neuroblastoma growth by specifically acting against malignant undifferentiated cells

The small, water soluble molecule Dichloroacetate (DCA) is recently arousing lively interests in the field of cancer therapy for it has been shown to be able to inhibit the growth of human tumors acting specifically on the mitochondria of cancer cells without perturbing the physiology of nonmalignant cells. Neuroblastoma was one of the tumor types on which DCA was considered ineffective as it is composed of cells with few recognized mitochondrial anomalies. Neuroblastoma, however, is composed of different cell types in terms of metabolism, phenotype and malignant potential. Despite the above prediction, in this work, we show that (i) DCA exhibits an unexpected anticancer effect on NB tumor cells and (ii) this effect is selectively directed to very malignant NB cells, whereas the more differentiated/less malignant NB cells are refractory to DCA treatment. This result supports the need of a detailed investigation of DCA anticancer properties against this tumor type with the final aim of its possible use as therapeutic agent.

Role of SLC5A8, a plasma membrane transporter and a tumor suppressor, in the antitumor activity of dichloroacetate

There has been growing interest among the public and scientists in dichloroacetate as a potential anticancer drug. Credible evidence exists for the antitumor activity of this compound, but high concentrations are needed for significant therapeutic effect. Unfortunately, these high concentrations produce detrimental side effects involving nervous system, thereby precluding its use for cancer treatment. The mechanistic basis of the compound’s antitumor activity is its ability to activate pyruvate dehydrogenase complex through inhibition of pyruvate dehydrogenase kinase. Since the compound inhibits the kinase at micromolar concentrations, it is not known why therapeutically prohibitive high doses are needed for suppression of tumor growth. We hypothesized that lack of effective mechanisms for the entry of dichloroacetate into tumor cells may underlie this phenomenon. Here we show that SLC5A8 transports dichloroacetate very effectively with high affinity. This transporter is expressed in normal cells, but the expression is silenced in tumor cells via epigenetic mechanisms. The lack of the transporter makes tumor cells resistant to the antitumor activity of dichloroacetate. However, if the transporter is expressed in tumor cells ectopically, the cells become sensitive to the drug at low concentrations. This is evident in breast cancer cells, colon cancer cells, and prostate cancer cells. Normal cells, which constitutively express the transporter, are however not affected by the compound, indicating the tumor cell-selective therapeutic activity. The mechanism of the antitumor activity of the compound is still its ability to inhibit pyruvate dehydrogenase kinase and force mitochondrial oxidation of pyruvate. Since the silencing of SLC5A8 in tumors involves DNA methylation and its expression can be induced by treatment with DNA methylation inhibitors, our findings suggest that combining dichloroacetate with a DNA methylation inhibitor would offer a means to reduce the doses of dichloroacetate to avoid detrimental effects associated with high doses but without compromising antitumor activity.

In vitro cytotoxicity of combinations of dichloroacetate with anticancer platinum compounds

Purpose

Dichloroacetate (DCA) inhibits pyruvate dehydrogenase kinase (PDK), and thus promotes glucose oxidation over glycolysis and induces apoptotic death of tumor cells. The present study investigated the potential of DCA to increase the antitumor effects of platinum- based compounds against a panel of permanent cell lines, including small cell lung cancer (SCLC), ovarian cancer, and Ewing’s sarcoma in vitro.

Methods

DCA at a concentration of 10 mM was combined with cisplatin, carboplatin, satraplatin, the satraplatin metabolite JM118, oxaliplatin, oxoplatin, and picoplatin, and the cytotoxic activity was evaluated in proliferation tests employing a panel of different cell lines. Additionally, cells were pretreated with DCA and then exposed to the platinum drugs and etoposide, or incubated with cisplatin or etoposide followed by application of DCA, respectively.

Results

DCA 10 mM significantly increased the cytotoxicity of the platinum-based drugs carboplatin, satraplatin, JM118, and oxoplatin, but not cisplatin, picoplatin, and oxaliplatin in vitro. Preincubation of cell lines with DCA 10 mM for three days reduced the antiproliferative activity of platinum-based agents in sequential application, but exposure of cells pretreated with cisplatin or etoposide to DCA resulted in minor sensitization. The inhibitory effect of DCA showed no correlation with sensitization to the platinum compounds.

Conclusion

DCA alone in a concentration that shows low antiproliferative activity is capable of increasing the cytotoxicity of selected platinum compounds upon coincubation, and such combinations may be interesting for clinical application in tumors like SCLC, Ewing’s sarcoma, and ovarian cancer refractory to cisplatin chemotherapy as standard care. The mechanism of this synergistic effect of DCA in combination with specific platinum species remains to be investigated.