title: A chalcone-related small molecule that induces methuosis, a novel form of non-apoptotic cell death, in glioblastoma cells.
abstract: BACKGROUND
  Methuosis is a unique form of non-apoptotic cell death triggered by alterations in the trafficking of clathrin-independent endosomes, ultimately leading to extreme vacuolization and rupture of the cell.
  
  
  RESULTS
  Here we describe a novel chalcone-like molecule, 3-(2-methyl-1H- indol-3-yl)-1-(4-pyridinyl)-2-propen-1-one (MIPP) that induces cell death with the hallmarks of methuosis. MIPP causes rapid accumulation of vacuoles derived from macropinosomes, based on time-lapse microscopy and labeling with extracellular fluid phase tracers. Vacuolization can be blocked by the cholesterol-interacting compound, filipin, consistent with the origin of the vacuoles from non-clathrin endocytic compartments. Although the vacuoles rapidly acquire some characteristics of late endosomes (Rab7, LAMP1), they remain distinct from lysosomal and autophagosomal compartments, suggestive of a block at the late endosome/lysosome boundary. MIPP appears to target steps in the endosomal trafficking pathway involving Rab5 and Rab7, as evidenced by changes in the activation states of these GTPases. These effects are specific, as other GTPases (Rac1, Arf6) are unaffected by the compound. Cells treated with MIPP lose viability within 2-3 days, but their nuclei show no evidence of apoptotic changes. Inhibition of caspase activity does not protect the cells, consistent with a non-apoptotic death mechanism. U251 glioblastoma cells selected for temozolomide resistance showed sensitivity to MIPP-induced methuosis that was comparable to the parental cell line.
  
  
  CONCLUSIONS
  MIPP might serve as a prototype for new drugs that could be used to induce non-apoptotic death in cancers that have become refractory to agents that work through DNA damage and apoptotic mechanisms.
authors.affiliation: Department of Biochemistry and Cancer Biology, University of Toledo College of Medicine, Toledo, Ohio, USA.
authors.forename: Jean H
authors.initials: JH
authors.lastname: Overmeyer
authors.forename: Ashley M
authors.initials: AM
authors.lastname: Young
authors.forename: Haymanti
authors.initials: H
authors.lastname: Bhanot
authors.forename: William A
authors.initials: WA
authors.lastname: Maltese
mesh_terms: D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology*; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D002599:Chalcone / Q000031:analogs & derivatives* / Q000494:pharmacology*; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000235:genetics; D011992:Endosomes / Q000187:drug effects / Q000378:metabolism; D005909:Glioblastoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D008954:Models, Biological; D014617:Vacuoles / Q000187:drug effects; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000378:metabolism
chemical_list: D000089982:ADP-Ribosylation Factor 6; D000970:Antineoplastic Agents; D002599:Chalcone; D020727:ADP-Ribosylation Factors; C000715348:ARF6 protein, human; D020691:rab GTP-Binding Proteins; D020830:rac1 GTP-Binding Protein