Mitochondrial Electron Transport Is the Cellular Target of the Oncology Drug Elesclomol

Elesclomol is a first-in-class investigational drug currently undergoing clinical evaluation as a novel cancer therapeutic. The potent antitumor activity of the compound results from the elevation of reactive oxygen species (ROS) and oxidative stress to levels incompatible with cellular survival. However, the molecular target(s) and mechanism by which elesclomol generates ROS and subsequent cell death were previously undefined. The cellular cytotoxicity of elesclomol in the yeast S. cerevisiae appears to occur by a mechanism similar, if not identical, to that in cancer cells. Accordingly, here we used a powerful and validated technology only available in yeast that provides critical insights into the mechanism of action, targets and processes that are disrupted by drug treatment. Using this approach we show that elesclomol does not work through a specific cellular protein target. Instead, it targets a biologically coherent set of processes occurring in the mitochondrion. Specifically, the results indicate that elesclomol, driven by its redox chemistry, interacts with the electron transport chain (ETC) to generate high levels of ROS within the organelle and consequently cell death. Additional experiments in melanoma cells involving drug treatments or cells lacking ETC function confirm that the drug works similarly in human cancer cells. This deeper understanding of elesclomol's mode of action has important implications for the therapeutic application of the drug, including providing a rationale for biomarker-based stratification of patients likely to respond in the clinical setting

Alpha synuclein determines ferroptosis sensitivity in dopaminergic neurons via modulation of ether-phospholipid membrane composition.

There is a continued unmet need for treatments that can slow Parkinson's disease progression due to the lack of understanding behind the molecular mechanisms underlying neurodegeneration. Since its discovery, ferroptosis has been implicated in several diseases and represents a therapeutic target in Parkinson's disease. Here, we use two highly relevant human dopaminergic neuronal models to show that endogenous levels of α-synuclein can determine the sensitivity of dopaminergic neurons to ferroptosis. We show that reducing α-synuclein expression in dopaminergic neurons leads to ferroptosis evasion, while elevated α-synuclein expression in patients' small-molecule-derived neuronal precursor cells with SNCA triplication causes an increased vulnerability to lipid peroxidation and ferroptosis. Lipid profiling reveals that ferroptosis resistance is due to a reduction in ether-linked phospholipids, required for ferroptosis, in neurons depleted of α-synuclein (α-syn). These results provide a molecular mechanism linking α-syn levels to the sensitivity of dopaminergic neurons to ferroptosis, suggesting potential therapeutic relevance

Continuous cerebroventricular administration of dopamine: A new treatment for severe dyskinesia in Parkinson’s disease?

In Parkinson’s disease (PD) depletion of dopamine in the nigro-striatal pathway is a main pathological hallmark that requires continuous and focal restoration. Current predominant treatment with intermittent oral administration of its precursor, Levodopa (l-dopa), remains the gold standard but pharmacological drawbacks trigger motor fluctuations and dyskinesia. Continuous intracerebroventricular (i.c.v.) administration of dopamine previously failed as a therapy because of an inability to resolve the accelerated dopamine oxidation and tachyphylaxia. We aim to overcome prior challenges by demonstrating treatment feasibility and efficacy of continuous i.c.v. of dopamine close to the striatum. Dopamine prepared either anaerobically (A-dopamine) or aerobically (O-dopamine) in the presence or absence of a conservator (sodium metabisulfite, SMBS) was assessed upon acute MPTP and chronic 6-OHDA lesioning and compared to peripheral l-dopa treatment. A-dopamine restored motor function and induced a dose dependent increase of nigro-striatal tyrosine hydroxylase positive neurons in mice after 7 days of MPTP insult that was not evident with either O-dopamine or l-dopa. In the 6-OHDA rat model, continuous circadian i.c.v. injection of A-dopamine over 30 days also improved motor activity without occurrence of tachyphylaxia. This safety profile was highly favorable as A-dopamine did not induce dyskinesia or behavioral sensitization as observed with peripheral l-dopa treatment. Indicative of a new therapeutic strategy for patients suffering from l-dopa related complications with dyskinesia, continuous i.c.v. of A-dopamine has greater efficacy in mediating motor impairment over a large therapeutic index without inducing dyskinesia and tachyphylaxia

Whole and fractionated human platelet lysate biomaterials-based biotherapy induces strong neuroprotection in experimental models of amyotrophic lateral sclerosis

International audienceAmyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease of motor neurons leading to death within 3 years and without a curative treatment. Neurotrophic growth factors (NTFs) are pivotal for cell survival. A reason for the lack of patient efficacy with single recombinant NTF brain infusion is likely to be due to the synergistic neuroprotective action of multiple NTFs on a diverse set of signaling pathways. Fractionated (protein size <50, <30, <10, <3 kDa) heat-treated human platelet lysate (HHPL) preparations were adapted for use in brain tissue with the aim of demonstrating therapeutic value in ALS models and further elucidation of the mechanisms of action. In neuronal culture all fractions induced Akt-dependent neuroprotection as well as a strong anti-apoptotic and anti-ferroptotic action. In the <3 kDa fraction anti-ferroptotic properties were shown to be GPX4 dependent highlighting a role for other platelet elements associated with NTFs. In the SOD1G86

Inactivation of the HIF-1 /PDK3 Signaling Axis Drives Melanoma toward Mitochondrial Oxidative Metabolism and Potentiates the Therapeutic Activity of Pro-Oxidants

International audienc

Sensitivity of <i>S. cerevisiae</i> mutant strains to elesclomol-Cu.

<p>(A) A genome-wide readout of heterozygous strain sensitivity. In the plot, the X-axis orders all genes by their systematic name (hence, chromosome position) while the Y-axis is a measure of the ‘fitness’ of the strain deleted for the indicated gene grown in sub-lethal doses of elesclomol-Cu. The value on the Y-axis corresponds to −log₂ (ratio of normalized strain signal in treatment to DMSO control). Hence, the zero line represents equivalent growth in both conditions, while each unit above the line represents a 2-fold reduction in strain fitness. (B) Genome-wide profile of homozygous strain sensitivity. The data are presented as in <i>(A)</i>. Among the 150 most sensitive strains, the 137 having mitochondrial roles are highlighted color-coded: red (7 genes, mitochondrial genome maintenance), dark brown (8 genes, metal ion homeostasis), bright green (26 genes, mitochondrial localization), aqua (4 genes, mitochondrial, uncharacterized), blue (36 genes, ox-phos and respiration) mauve (5 genes, mitochondrial splicing), light gray (9 genes, response to stress) dark brown (26 genes, mitochondrial translation), dark gray (7 genes, mitochondrial import/export) and dark green (9 genes, mitochondrial tRNA).</p

Elesclomol-induced ROS generation and cytoxicity in yeast is dependent on the presence of copper.

<p>(A) Chemical structure of the elesclomol-Cu complex. (B) The parental BY4743 yeast strain was grown in the presence of the indicated concentrations of elesclomol, preformed elesclomol-Cu, and/or copper for 21.5 h at 30°C. Absorbance at 600 nm was used to determine cell density. (C) Flow cytometric analysis measuring ROS in <i>S. cerevisiae</i>. ROS induction, as measured by Dihydrorhodamine 123 fluorescence, was only observed with preformed elesclomol-Cu complex at a concentration (500 nM) above the MIC but not below (100 nM), nor with free elesclomol at either concentration (<i>upper panel</i>). The addition of supplementary copper (via CuCl₂) to elesclomol was sufficient to induce ROS, again only at the higher concentration (<i>lower panel</i>). (D) Elesclomol is cidal to yeast cells within an hour of treatment. Logarithmically growing cells were incubated with the indicated doses of elesclomol for 1, 2 or 4 h and then plated onto media without elesclomol. 5 µM and 22.5 µM elesclomol rendered cells unviable within 1 h, and lower doses (1.25 µM) killed cells within 4 h.</p

Biological processes and protein complexes associated with sensitivity to elesclomol.

<p>(A) Each node represents a significantly enriched biological process/protein complex in the elesclomol chemogenomic profile as determined by GSEA. The size of a node corresponds to the number of genes annotated to the functional category. The width of an edge corresponds to the level of gene overlap between two interconnected categories (i.e. gene sets). Edges are not shown where the overlap coefficient is less than 0.5 (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0029798#s4" target="_blank">Materials and Methods</a>). The color of a node shows the cluster membership where clustering is based on the level of overlap between categories. (B) Each bar plot corresponds to the cluster indicated by its border color, and shows the individual sensitivity scores (X-axis) of the genes that contributed to the functional enrichments of the cluster. For clusters with more than 10 genes contributing to the enrichments, only the top 10 associated with the most categories are shown. The percentage of times the particular genes occur in that gene set is indicated by a color key, with black indicating the gene is present every time that function appears enriched, graded to white for those genes in the leading edge that appear less frequently within the gene set.</p

Combinations of elesclomol-Cu and ETC complex inhibitors in melanoma cells.

<p>(A) Single agent viability assays in Hs249T human melanoma cells using graded concentrations of elesclomol-Cu, antimycin A or rotenone for 72 h. The IC₅₀ values obtained were 11 nM, 240 nM and 77 nM, respectively. Combination treatment of elesclomol-Cu with antimycin A (B) or rotenone (C) at IC₂₀ or IC₅₀ doses resulted in significantly enhanced cytotoxicity, showing that direct modulation of the ETC and mitochondrial respiration in mammalian cells enhances the cellular activity of elesclomol.</p