title: Regulation of dimethyl-fumarate toxicity by proteasome inhibitors.
abstract: The present studies examined the biology of the multiple sclerosis drug dimethyl-fumarate (DMF) or its in vivo breakdown product and active metabolite mono-methyl-fumarate (MMF), alone or in combination with proteasome inhibitors, in primary human glioblastoma (GBM) cells. MMF enhanced velcade and carfilzomib toxicity in multiple primary GBM isolates. Similar data were obtained in breast and colon cancer cells. MMF reduced the invasiveness of GBM cells, and enhanced the toxicity of ionizing radiation and temozolomide. MMF killed freshly isolated activated microglia which was associated with reduced IL-6, TGFβ and TNFα production. The combination of MMF and the multiple sclerosis drug Gilenya further reduced both GBM and activated microglia viability and cytokine production. Over-expression of c-FLIP-s or BCL(-)XL protected GBM cells from MMF and velcade toxicity. MMF and velcade increased plasma membrane localization of CD95, and knock down of CD95 or FADD blocked the drug interaction. The drug combination inactivated AKT, ERK1/2 and mTOR. Molecular inhibition of AKT/ERK/mTOR signaling enhanced drug combination toxicity whereas molecular activation of these pathways suppressed killing. MMF and velcade increased the levels of autophagosomes and autolysosomes and knock down of ATG5 or Beclin1 protected cells. Inhibition of the eIF2α/ATF4 arm or the IRE1α/XBP1 arm of the ER stress response enhanced drug combination lethality. This was associated with greater production of reactive oxygen species and quenching of ROS suppressed cell killing.
authors.affiliation: a Department of Biochemistry and Molecular Biology.
authors.forename: Laurence
authors.initials: L
authors.lastname: Booth
authors.forename: Nichola
authors.initials: N
authors.lastname: Cruickshanks
authors.forename: Seyedmehrad
authors.initials: S
authors.lastname: Tavallai
authors.forename: Jane L
authors.initials: JL
authors.lastname: Roberts
authors.forename: Matthew
authors.initials: M
authors.lastname: Peery
authors.forename: Andrew
authors.initials: A
authors.lastname: Poklepovic
authors.forename: Paul
authors.initials: P
authors.lastname: Dent
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D015415:Biomarkers; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D000069462:Dimethyl Fumarate; D004357:Drug Synergism; D005650:Fumarates / Q000633:toxicity*; D005909:Glioblastoma / Q000378:metabolism; D006801:Humans; D017628:Microglia / Q000187:drug effects / Q000378:metabolism; D061988:Proteasome Inhibitors / Q000494:pharmacology*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D000970:Antineoplastic Agents; D015415:Biomarkers; D005650:Fumarates; D061988:Proteasome Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D000069462:Dimethyl Fumarate
keywords: DMF, dimethyl-fumarate; EGF, epidermal growth factor; ERK, extracellular regulated kinase; JNK, c-Jun NH2-terminal kinase; MAPK, mitogen activated protein kinase; MEK, mitogen activated extracellular regulated kinase; MMF, monomethyl-fumarate; P, phospho-; PARP, poly ADP ribosyl polymerase; PI3K, phosphatidyl inositol 3 kinase; PTEN, Phosphatase and tensin homolog; R, receptor; WT, wild type; ca, constitutively active; dn, dominant negative; −/−, null / gene deleted