title: Mechanism of trifluoromethionine resistance in Entamoeba histolytica.
abstract: OBJECTIVE
  To determine the mechanism of trifluoromethionine resistance in Entamoeba histolytica and evaluate the impact of acquired drug resistance on virulence.
  
  
  METHODS
  Trifluoromethionine-resistant amoebae were selected in vitro and examined for cross-resistance to antiamoebic drugs, stability of resistance, methionine γ-lyase (MGL) activity, cell adhesion and virulence. Targeted gene silencing was performed to confirm the role of EhMGL.
  
  
  RESULTS
  Trophozoites with a resistance index of 154 were obtained. The cells were susceptible to chloroquine, metronidazole, paromomycin and tinidazole, but remained resistant to trifluoromethionine in the absence of drug pressure. A complete lack of EhMGL activity accompanied by increased adhesion and decreased cytolysis were also observed. Silencing of the EhMGL genes resulted in trifluoromethionine resistance.
  
  
  CONCLUSIONS
  This study provides the first demonstration of trifluoromethionine resistance in a parasitic protozoon. Repression of gene expression of drug targets represents a novel mechanism of resistance in E. histolytica. The information obtained from this work should help further development of trifluoromethionine derivatives that have lower chances of inducing resistance.
authors.affiliation: Department of Parasitology, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan.
authors.forename: Gil M
authors.initials: GM
authors.lastname: Penuliar
authors.forename: Atsushi
authors.initials: A
authors.lastname: Furukawa
authors.forename: Dan
authors.initials: D
authors.lastname: Sato
authors.forename: Tomoyoshi
authors.initials: T
authors.lastname: Nozaki
mesh_terms: D000818:Animals; D000981:Antiprotozoal Agents / Q000494:pharmacology*; D015153:Blotting, Western; D016466:CHO Cells; D013437:Carbon-Sulfur Lyases / Q000037:antagonists & inhibitors; D002448:Cell Adhesion / Q000187:drug effects; D006224:Cricetinae; D003412:Cricetulus; D003470:Culture Media; D004351:Drug Resistance; D004587:Electrophoresis, Agar Gel; D004748:Entamoeba histolytica / Q000187:drug effects* / Q000201:enzymology / Q000254:growth & development; D005786:Gene Expression Regulation / Q000187:drug effects; D020868:Gene Silencing; D007700:Kinetics; D008715:Methionine / Q000031:analogs & derivatives* / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D000981:Antiprotozoal Agents; D003470:Culture Media; C037646:trifluoromethionine; D008715:Methionine; D013437:Carbon-Sulfur Lyases; C021558:L-methionine gamma-lyase