chaetocin and Brain-Neoplasms

Glioblastoma Multiforme (GBM) is the most common and aggressive primary brain tumor. Despite recent developments in surgery, chemo- and radio-therapy, a currently poor prognosis of GBM patients highlights an urgent need for novel treatment strategies. TRAIL (TNF Related Apoptosis Inducing Ligand) is a potent anti-cancer agent that can induce apoptosis selectively in cancer cells. GBM cells frequently develop resistance to TRAIL which renders clinical application of TRAIL therapeutics inefficient. In this study, we undertook a chemical screening approach using a library of epigenetic modifier drugs to identify compounds that could augment TRAIL response. We identified the fungal metabolite chaetocin, an inhibitor of histone methyl transferase SUV39H1, as a novel TRAIL sensitizer. Combining low subtoxic doses of chaetocin and TRAIL resulted in very potent and rapid apoptosis of GBM cells. Chaetocin also effectively sensitized GBM cells to further pro-apoptotic agents, such as FasL and BH3 mimetics. Chaetocin mediated apoptosis sensitization was achieved through ROS generation and consequent DNA damage induction that involved P53 activity. Chaetocin induced transcriptomic changes showed induction of antioxidant defense mechanisms and DNA damage response pathways. Heme Oxygenase 1 (HMOX1) was among the top upregulated genes, whose induction was ROS-dependent and HMOX1 depletion enhanced chaetocin mediated TRAIL sensitization. Finally, chaetocin and TRAIL combination treatment revealed efficacy in vivo. Taken together, our results provide a novel role for chaetocin as an apoptosis priming agent and its combination with pro-apoptotic therapies might offer new therapeutic approaches for GBMs.

Topics: Animals; Apoptosis; bcl-X Protein; Brain Neoplasms; Caspases; Cell Line, Tumor; Cell Proliferation; Cell Survival; DNA Damage; Drug Evaluation, Preclinical; Drug Synergism; Epigenesis, Genetic; Fas Ligand Protein; Fungi; Gene Expression Regulation, Neoplastic; Glioblastoma; Heme Oxygenase-1; Humans; Metabolome; Mice; Models, Biological; Piperazines; Reactive Oxygen Species; RNA, Messenger; TNF-Related Apoptosis-Inducing Ligand; Transcriptome; Tumor Suppressor Protein p53

Oxidative stress serves as an important regulator of both apoptosis and metabolic reprogramming in tumor cells. Chaetocin, a histone methyltransferase inhibitor, is known to induce ROS generation. As elevating basal ROS level sensitizes glioma cells to apoptosis, the ability of Chaetocin in regulating apoptotic and metabolic adaptive responses in glioma was investigated. Chaetocin induced glioma cell apoptosis in a ROS-dependent manner. Increased intracellular ROS induced (i) Yes-associated protein 1 (YAP1) expression independent of the canonical Hippo pathway as well as (ii) ATM and JNK activation. Increased interaction of YAP1 with p73 and p300 induced apoptosis in an ATM-dependent manner. Chaetocin induced JNK modulated several metabolic parameters like glucose uptake, lactate production, ATP generation, and activity of glycolytic enzymes hexokinase and pyruvate kinase. However, JNK had no effect on ATM or YAP1 expression. Coherent with the in vitro findings, Chaetocin reduced tumor burden in heterotypic xenograft glioma mouse model. Chaetocin-treated tumors exhibited heightened ROS, pATM, YAP1 and pJNK levels. Our study highlights the coordinated control of glioma cell proliferation and metabolism by ROS through (i) ATM-YAP1-driven apoptotic pathway and (ii) JNK-regulated metabolic adaptation. The elucidation of these newfound connections and the roles played by ROS to simultaneously shift metabolic program and induce apoptosis could provide insights toward the development of new anti-glioma strategies.

Topics: Adaptor Proteins, Signal Transducing; Adenosine Triphosphate; Animals; Antineoplastic Agents; Apoptosis; Ataxia Telangiectasia Mutated Proteins; Brain Neoplasms; Cell Line, Tumor; Cell Proliferation; DNA-Binding Proteins; Dose-Response Relationship, Drug; Enzyme Activation; Glioma; Glucose; Hexokinase; Humans; JNK Mitogen-Activated Protein Kinases; Lactic Acid; Mice; Mice, Nude; Nuclear Proteins; Oxidative Stress; p300-CBP Transcription Factors; Phosphoproteins; Piperazines; Pyruvate Kinase; Reactive Oxygen Species; RNA Interference; Signal Transduction; Time Factors; Transcription Factors; Transfection; Tumor Burden; Tumor Protein p73; Tumor Suppressor Proteins; Xenograft Model Antitumor Assays; YAP-Signaling Proteins

Aberrant epigenetic histone modifications are implicated in cancer pathobiology, therefore histone modifying enzymes are emerging targets for anti-cancer therapy. There is a few evidence for deregulation of the histone modifying enzymes in glioblastomas. Glioma treatment is a clinical challenge due to its resistance to current therapies.. The effect of selected inhibitors on epigenetic modifications and viability of glioma C6 cells were studied using immunofluorescence and MTT metabolism test.. We found that VPA and TSA increase histone H4 acetylation in glioma cells, while chaetocin and BIX01294 at low concentrations reduce H3K9me3, and 3DZNep decreases H3K27me3. Long-term treatment with some epigenetic inhibitors affects viability of glioma cells.. We established the concentrations of selected inhibitors which in C6 glioma cells inhibit the enzyme activity, but do not decrease cell viability, hence allow to study the role of histone modifications in C6 glioma biology.

Topics: Acetylation; Adenosine; Animals; Azepines; Brain Neoplasms; Cell Line, Tumor; Cell Survival; Enzyme Inhibitors; Epigenesis, Genetic; Glioma; Histones; Hydroxamic Acids; Piperazines; Quinazolines; Rats; Valproic Acid