title: Increased expression of glutamate transporter GLT-1 in peritumoral tissue associated with prolonged survival and decreases in tumor growth in a rat model of experimental malignant glioma.
abstract: OBJECTIVE
  Gliomas are known to release excessive amounts of glutamate, inducing glutamate excitotoxic cell death in the peritumoral region and allowing the tumor to grow and to expand. Glutamate transporter upregulation has been shown to be neuroprotective by removing extracellular glutamate in a number of preclinical animal models of neurodegenerative diseases, including amyotrophic lateral sclerosis and Parkinson disease as well as psychiatric disorders such as depression. The authors therefore hypothesized that the protective mechanism of glutamate transporter upregulation would be useful for the treatment of gliomas as well.
  
  
  METHODS
  In this study 9L gliosarcoma cells were treated with a glutamate transporter upregulating agent, thiamphenicol, an antibiotic approved in Europe, which has been shown previously to increase glutamate transporter expression and has recently been validated in a human Phase I biomarker trial for glutamate transporter upregulation. Cells were monitored in vitro for glutamate transporter levels and cell proliferation. In vivo, rats were injected intracranially with 9L cells and were treated with increasing doses of thiamphenicol. Animals were monitored for survival. In addition, postmortem brain tissue was analyzed for tumor size, glutamate transporter levels, and neuron count.
  
  
  RESULTS
  Thiamphenicol showed little effects on proliferation of 9L gliosarcoma cells in vitro and did not change glutamate transporter levels in these cells. However, when delivered locally in an experimental glioma model in rats, thiamphenicol dose dependently (10-5000 μM) significantly increased survival up to 7 days and concomitantly decreased tumor size from 46.2 mm(2) to 10.2 mm(2) when compared with lesions in nontreated controls. Furthermore, immunohistochemical and biochemical analysis of peritumoral tissue confirmed an 84% increase in levels of glutamate transporter protein and a 72% increase in the number of neuronal cells in the tissue adjacent to the tumor.
  
  
  CONCLUSIONS
  These results show that increasing glutamate transporter expression in peritumoral tissue is neuroprotective. It suggests that glutamate transporter upregulation for the treatment of gliomas should be further investigated and potentially be part of a combination therapy with standard chemotherapeutic agents.
authors.affiliation: Department of Neurology.
authors.forename: Rita
authors.initials: R
authors.lastname: Sattler
authors.forename: Betty
authors.initials: B
authors.lastname: Tyler
authors.forename: Benjamin
authors.initials: B
authors.lastname: Hoover
authors.forename: Luke T
authors.initials: LT
authors.lastname: Coddington
authors.forename: Violette
authors.initials: V
authors.lastname: Recinos
authors.forename: Lee
authors.initials: L
authors.lastname: Hwang
authors.forename: Henry
authors.initials: H
authors.lastname: Brem
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Rothstein
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D001921:Brain / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D001932:Brain Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004195:Disease Models, Animal; D027342:Excitatory Amino Acid Transporter 2 / Q000235:genetics / Q000378:metabolism*; D018316:Gliosarcoma / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D051381:Rats; D011916:Rats, Inbred F344; D013839:Thiamphenicol / Q000494:pharmacology / Q000627:therapeutic use
chemical_list: D027342:Excitatory Amino Acid Transporter 2; C493395:Slc1a2 protein, rat; D013839:Thiamphenicol
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