title: Genetic polymorphisms of glutathione S-transferase A1, the major glutathione S-transferase in human liver: consequences for enzyme expression and busulfan conjugation.
abstract: BACKGROUND
  High-dose busulfan is widely used as part of conditioning regimens for patients who are undergoing hematopoietic stem cell or bone marrow transplantation. High plasma concentrations of busulfan have been linked to the occurrence of hepatic venoocclusive disease (VOD), a severe complication associated with a high mortality. Because conjugation with glutathione, the major route of biotransformation of busulfan, is predominantly catalyzed by the isozyme glutathione S-transferase A1 (GSTA1), we hypothesized that low expression or function of GSTA1 in liver caused by genetic polymorphisms may be the mechanism underlying VOD.
  
  
  METHODS
  Immunoblot analysis of GSTA and measurement of busulfan-glutathione conjugation by liquid chromatography-mass spectrometry were performed in 48 normal human liver samples. To search for polymorphisms, the complete GSTA1 coding regions and the promoter fragment were sequenced. All results were compared by multivariate analysis.
  
  
  RESULTS
  Absolute levels of GSTA protein and formation rates of busulfan-glutathione conjugate displayed a 7- and 8-fold range, from 240 to 1600 pmol/mg and 25 to 205 pmol/min per milligram of total cytosolic protein, respectively, and correlate (r2 = 0.49, P <.0001). A total of 8 single nucleotide polymorphisms (SNPs) of GSTA1 were identified, 1 of which was a silent mutation in exon 5 (A375G); all others were found in the promoter region. Haplotype analysis revealed the existence of 5 defined alleles. There was no significant relationship between any of the GSTA1 SNPs or haplotypes and either hepatic glutathione S-transferase A (GSTA) expression or GSTA1 function.
  
  
  CONCLUSIONS
  The identified GSTA1 polymorphisms are not likely to be related to the VOD because they do not appear to be associated with changes in GSTA expression or function. Compared with other members of the GST family, GSTA1 displays surprisingly little variation.
authors.affiliation: Dr Margarete Fischer-Bosch Institute of Clinical Pharmacology, Stuttgart, Germany.
authors.forename: Monika
authors.initials: M
authors.lastname: Bredschneider
authors.forename: Kathrin
authors.initials: K
authors.lastname: Klein
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Mürdter
authors.forename: Claudia
authors.initials: C
authors.lastname: Marx
authors.forename: Michel
authors.initials: M
authors.lastname: Eichelbaum
authors.forename: Andreas K
authors.initials: AK
authors.lastname: Nüssler
authors.forename: Peter
authors.initials: P
authors.lastname: Neuhaus
authors.forename: Ulrich M
authors.initials: UM
authors.lastname: Zanger
authors.forename: Matthias
authors.initials: M
authors.lastname: Schwab
mesh_terms: D002066:Busulfan / Q000378:metabolism*; D017931:DNA Primers; D015971:Gene Expression Regulation, Enzymologic; D005838:Genotype; D005982:Glutathione Transferase / Q000235:genetics* / Q000378:metabolism*; D006239:Haplotypes; D006801:Humans; D015151:Immunoblotting; D007166:Immunosuppressive Agents / Q000378:metabolism*; D015999:Multivariate Analysis; D010641:Phenotype; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D011401:Promoter Regions, Genetic / Q000235:genetics
chemical_list: D017931:DNA Primers; D007166:Immunosuppressive Agents; D005982:Glutathione Transferase; D002066:Busulfan