BACKGROUND: The glutathione S-transferases (GST) mediate exposure to various cytotoxic and genotoxic agents, including those associated with increased risk of the myelodysplastic syndromes (MDS). Both GST M1 (GSTM1) and GST theta 1 (GSTT1) genes have a "null" variant allele, in which the entire gene is absent. We tested whether the homozygous null genotype of GSTM1 and GSTT1 altered the risk for MDS. METHODS: In a hospital-based case-control study we analysed lymphocyte or bone-marrow DNA samples from 96 patients with MDS and 201 cancer-free controls of similar age, race, and sex. We have restricted our report to the 92 white MDS patients. We analysed GSTM1 and GSTT1 genotypes by PCR. FINDINGS: The frequency of the GSTT1 null genotype was higher among MDS cases (46%) than among controls (16%). Inheritance of the GSTT1 null genotype conferred a 4.3-fold of MDS (odds ratio 4.3, 95% CI 2.5-7.4, p < 0.00001). The GSTM1 null genotype was not associated with increased risk of MDS (odds ratio 0.8, 0.5-1.3). INTERPRETATION: Individuals with the GSTT1 null genotype may have enhanced susceptibility to MDS. The mechanism might involve decreased detoxification of environmental or endogenous carcinogens.
BACKGROUND: The glutathione S-transferases (GST) mediate exposure to various cytotoxic and genotoxic agents, including those associated with increased risk of the myelodysplastic syndromes (MDS). Both GST M1 (GSTM1) and GST theta 1 (GSTT1) genes have a "null" variant allele, in which the entire gene is absent. We tested whether the homozygous null genotype of GSTM1 and GSTT1 altered the risk for MDS. METHODS: In a hospital-based case-control study we analysed lymphocyte or bone-marrow DNA samples from 96 patients with MDS and 201 cancer-free controls of similar age, race, and sex. We have restricted our report to the 92 white MDSpatients. We analysed GSTM1 and GSTT1 genotypes by PCR. FINDINGS: The frequency of the GSTT1 null genotype was higher among MDS cases (46%) than among controls (16%). Inheritance of the GSTT1 null genotype conferred a 4.3-fold of MDS (odds ratio 4.3, 95% CI 2.5-7.4, p < 0.00001). The GSTM1 null genotype was not associated with increased risk of MDS (odds ratio 0.8, 0.5-1.3). INTERPRETATION: Individuals with the GSTT1 null genotype may have enhanced susceptibility to MDS. The mechanism might involve decreased detoxification of environmental or endogenous carcinogens.